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n. 



TP 



GEOLOGICAL SURVEY OF OHIO 

J. A. BOVNOCKER, State Geologbt 



FOURTH SERIES, BULLETIN 11 



THE 



MANUFACTURE OF ROOFING TILES 



By VOLSEY GARNET VORCESTER 



EDWAR.D ORTON, Jr., Collitborator and EcUtor 



Ptsb!iihed by atithority of the Legislature of Ohlo» ander the stspervUioa 

of the State Geologist 



Columbus. Ohio. August, )9I0 



Printed by the Springfield Publishing Company, 
Springfield, Ohio. 









GrOVERNOR JUDSON HaRMON : 

My Dear Sir — I transmit herewith a bulletin on the Manufacture of 
Roofing Tiks by Wolsey Garnet Worcester with the co-operation of Pro- 
fessor Edward Orton, Jr. So far as I can learn this is the first bulletin 
prepared in any country on this subject. 

Ohio is pre-eminent among the states in the clay industries, and it is 
fitting that she should lead in the scientific discussion of clays and the 
processes by which they are made of service to man. This is the first 
of a series of bulletins treating of these subjects, all of which will be under 
the general supervision of Professor Edward Orton, Jr. 

Respectfully submitted, 

J. A. BOWNOCKER, 

State Geologist. 
Columbus, Ohio, August 1, 1910. 



85074 



THE SURVEY IN ITS RELATIONS TO THE PUBLIC. 

The usefulness^ of the Survey is not limited to the preparation of 
formal reports on important topics. There is a constant and insistent 
desire on the part of the people to use it as a technical bureau for free 
advice in all matters affecting the geology or mineral industries of the 
State. A very considerable correspondence comes in, increasing rather 
tliau decreasing in amount, and asking specific and particular questions 
on points in local geology. 

The volume of this correspondence has made it necessary to adopt a 
uniform method of dealing with these requests. Not all of them can be 
granted, but some can and should be answered. There is a certain ele- 
ment of justice in the people's demanding such information, from the fact 
that the geological reports issued in former years were not so distributed 
as to make them accessible to the average man or community today. 
The cases commonly covered by correspondence may be classified as 
follows : 

1st. Requests for information covered by previous publications, — 
This is furnished where the time required for copying the answer is not 
too large. Where the portion desired cannot be copied, the enquirer is 
told in what volume and page it occurs and advised how to proceed to 
get access to a copy of the report. 

2d, Requests for identificaiioii of minerals and fossils. — This is 
done, where possible. As a rule, the minerals and fossils are simple and 
familiar forms, which can be answered at once. In occasional eases, a 
critical knowledge is required and time for investigation is necessary. 
Each assistant is expected to co-operate with the State Geologist in 
answering inquiries concerning his field. 

.?rd. Requests from private individuals for analyses of minerals and 
ores, and tests to establish their commercial value. — Such requests are 
frequent. They cannot be granted, however, except in rare instances. 
Such work should be sent to a commercial chemical laboratory. The 
position has been taken that the Geological Survey is in no sense a chem- 
ical laboratory and testing station, to which the people may turn for 
free analytical work. Whatever work of this sort is done, is done on the 
initiative of the Survey and not at the solicitation of an interested party. 

The greatest misapprehension in the public mind regarding the Sur- 
vey is on this point. Requests for State aid in determining the value of 
private mineral resources, ranging from an assay worth a dollar, up to 
drilling a test well costing several thousand dollars, represent extreme 
cases. At present there is no warrant for the Survey making private 
ti«ts, even where the applicant is entirely willing to pay for the service. 

(V) 



VI 

In many cases individuals would prefer the report of a State chemist or 
State geologist to that of any private exi3ert, at equal cost, because of the 
prestige which such a report would carry. But it is a matter of doubt 
whether it will ever be the function of the Survey to^ enter into commer- 
cial work of this character; it certainly will not be unless explicit legal 
provisions for it are made. 

4th. Requests from a number of persons representing a diversity of 
interests, who joi7itly ask the Survey to examine into and publicly report 
upon some matter of local public concern. — Such cases are not common. 
It is not always easy to determine whether such propositions are really 
actuated by public interest or not. Each case must be judged on its 
merits. The Survey will often be prevented from taking up such in- 
vestigations by the lack of available funds, while otherwise the work 
would be attempted. 

The reputed discovery of gold is one of the most prolific sources of 
such calls for State examination. It usually seems wise and proper to 
spend a small sum in preventing an unfounded rumor from gaining ac- 
ceptance in the public mind, before it leads to large losses, and unneces- 
sary'' excitement. The duty of dispelling illusions of this sort cannot be 
considered an agreeable part of the work of the Survey, but it is never- 
theless of very direct benefit to the people of the State. 



Vll 



PUBUCATIONS OF FOURTH GEOLOGICAL SURVEY OF OHIO. 



Title. 


Date of 

Issue. 


Number 

of 
Pages. 


Number 
of Copies 
Printed. 


State Geologist. 


Bulletin 1 — -Oil and Gas. . . 


1903 


320 


8,000 


Edward Orton, Jr. 


Bulletin 2 — Uses of Cement 


1904 


260 


6,000 


Edward Orton, Jr. 


Bulletin 3{^--^-^^^^^^^^ -\ 


1904 


391 


4,000 


Edward Orton, Jr. 

• 


Bulletin ^{^'^tme!"^^, T^ 


1906 


365 


4,000 


Edward Orton, Jr. 


Bulletin 5{^^|^-^^^^^ 


1906 


79 


4,000 


Edward Orton, Jr. 


Bulletin 6 — 'Bibliography . . 


1906 


322 


3.500 


Edward Orton, Jr. 


[Nomenclature of 
Bulletin 7 Geological 

, Formations . . 


1905 


36 

• 

* 


3,500 


Edward Orton, Jr. 


Bulletin 8 


Salt Deposits 
and Salt In- 
, dustry 


1906 


42 


3,500 


Edward Orton ^ Jr. 


Bulletin 9- 


—Coal 


1908 


342 


6,000 


J. A. Bownocker 




• 

Geol. Map of Ohio 


1909 




4,875 


J. A. Bownocker. 


Bulletin 10(**'^dle De- 

{ vonian 


1909 


204 


3,500 


J. A. Bownocker. 


Bulletin 11— Roofing Tiles 


1910 




3,500 


J. A. Bownocker. 



vni 

Under the law, copies of these Bulletins can be bought at the office 
of the State Geologist at the cost of publication. Postal orders, money 
orders, checks, drafts or currency must accompany order. Stamps will 
not be received. 

Bulletin 1— Oil and Gas $.65 

Bulletin 2 — Uses of Hydraulic Cement .30 

Bulletin 3 — Manufacture of Hydraulic Cement* 

Bulletin 4^ Lime Resources and Lime Industry • ■ ■ 1 45 

Bulletin 5 — Sand-Lime Brick Industry j 

Bulletin 6 — Bibliography of the Geology of Ohio, and 

Index to Publications of the Geological 

Survey of Ohio 35 

Bulletm 7 — -Revised Nomenclature of the Ohio Geo- 
logical Formations 06 

Bulletin 8 — Salt Deposits and Salt Industry in Ohio. .06 

Bulletin 9 — Coal 50 

Geological Map of Ohio 25 

Bulletin 10— The Middle Devonian of Ohio 25 

Bulletin 11 — The Manufacture of Roofing Tiles 75 



* The sale edition of Bulletin 3 is exhausted. 



FOURTH SERIES, BULLETIN U 



THE 



MANUFACTURE OF ROOFING TILES 



By 



WOLSEY GARNET WORCESTER 



EDWARD ORTON, Jr., Collaborator and Editor 



August, 19 JO 



LETTER OF TRANSMITTAL. 

Dr. J. A. BowNOCKEB, State Geologist : 

Dear Sir — I take pleasure in handing you herewith the first one of a 
series of Bulletins on the Clays and Clay Products of Ohio. The subject 
of this bulletin is Roofing Tiles, and has been prepared under my gen- 
eral direction by Mr. Wolsey Garnet Worcester, Instructor in Ceramic 
Engineering in the Ohio State University, and formerly identified witji 
the Roofing Tile industry as designer, builder and operator of roofing 
tile factories. 

The manufacture of roofing tile is not one of the most extensive 
of the clay industries, either in Ohio or in the United States. The 
reason for its treatment in the first of the proposed series of Bulletins 
on the Clay industries, .is that it is the first report to reach completion, 
out of several which are under preparation. As this report is practi- 
cally an independent and complete treatise in itself, no adequate reason 
exists for delaying its appearance until other reports are ready. 

It has been the aim in this report and in the others which are to 
follow on allied topics, to diverge quite widely from the type of reports 
formerly issued by this and most of the other states, in which the geology 
of the clay beds, their occurrence and extent, have been the matters of 
first importance and the technology of the clay industry has been gener- 
ally lightly touched upon. It is my belief that of the clay beds of Ohio 
and their occurrence, and quality, enough has been said already by the 
reports of the Geological Survey to very fairly present, this topic to the 
people of the State. But the utilization of clays of the types found in 
Ohio is a matter of very much more intricate nature than their geolo- 
gical occurrence, and in this subject no headway can be made to convert 
the clays into an asset of wealth, except through an understanding of 
the technological processes of manufacture and the physical and chem- 
ical principles on which these processes rest. These reports are there- 
fore directed primarily towards enabling the people of the State to use 
the clay resources which are available, and are therefore primarily 
technologic, rather than geologic in character. Mr. Worcester is pe- 
culiarly competent to present to the public an article on the manufacture 
of roofing tiles, on account of his practical experience in this industry, 
and it is anticipated that the value of his contribution will speedily be 
recognized when the report reaches the producers and users of clay arch- 
itectural materials. 

Very Respectfully submitted, 

Edward Orton Jr., E. 'M. 



CONTENTS* 

CHAPTER L 

Page 
Brief History of Roofing Tile Manufacture and Use 11 

CHAPTER n. 

The Varieties and Qualities of Roofing Tiles 30 

CHAPTER nL 

The Selection of Clays for Roofing Tile Manufacture 70 

CHAPTER IV. 

The Preparation of Roofing Tile Cl^ys for Manufacture 166 

CHAPTER V. 

The Manufacture or Forming of Roofing Tiles 242 

CHAPTER VI. 

The Manufacture of Special Shapes and Roofing Terra Cotta 309 

CHAPTER VII. 
The Drying of Roofing Tiles 333 

CHAPTER Vra. 

The Setting of Roofing Tiles 369 

CHAPTER IX. 

The Kilns for the Burning of Roofing Tiles 387 

CHAPTER X. 

Roofing Tile Slips and Glazes 416 

CHAPTER XL 
Stocking and Shipping Roofing Tiles 437 

CHAPTER Xn. 

Location and Design of Plants for Roofing Tile Manufacture 443 

(5) 



J 



ILLUSTRATIONS. 

No. Title. ■ Page. 

1. Tile from the Temple of Hera 12 

rt /Normal or Asiatic Tile Designs 12 

^' \Pan or Belgic Tile Designs 13 

3. Robinson's Tile, made at Germantown, Ohio, about 1814 14 

4. Building Covered About 1814 with Tiles made at Germantown, Ohio 16 

5. Roofing Tiles Made by the Zoar Community, Zoar, Ohio 16 

6. Old Church at Zoar, Ohio 17 

7. Conrade Tile, Taken from the Watts Residence, Zanesville, Ohio 18 

8. Map of the United States, Showing Distribution of the Roofing Tile 

Plants 23 

9. Round-edged Shingle Tiles 38 

10. Interlocking Shingle Tiles 38 

11. "S" or Spanish Tiles, Made on an Auger Machine 39 

12. Interlocking Spanish Tile 40 

13. Section of a Roof, Showing Interlocking Spanish Tiles 40 

14. Showing Proper Design for an Interlocking Tile to Lie Flat on a 

Pallet 40 

15. Interlocking Tiles, French A Pattern 41 

16. Showing Section of a Roof Laid with Interlocking Tiles in Which the 

Lock Joints Break 41 

17. Showing Various Forms of Side and End Locks 42 

18. Under Side of an Open Construction Roof 49 

19. Mueller Auger Machine 73 

20. Cross -breaking Machine 74 

21. Graphic Representation of Relative Cross- breaking Strength of the 

Standard Roofing Tile Clays 76 

22. Curves Showing Rate of Shrinkages in Drying 78 

23. Seger Volumeter 81 

24. Time-temperature Curve, Showing Heat Treatment of Test-pieces 87 

25. Sketch Showing Progressive Oxidation of the Standard Roofing 

Tile Clays at Various Stages of the Burning Process 88 

26. Porosity Changes in Clays of Group I. .114 

27. Porosity Changes in Clays of Group II. 116 

28. Porosity Changes in Clays of Group III. 118 

29. Porosity Changes per Cone in Clays I, J, K and L 119 

30. Curves Showing Changes in Specific Gravity of the Standard Roofing 

Tile Clays at Various Stages of Heat Treatment 124 

31. Curves Showing Changes in Linear Shrinkage of the Standard Roof- 

ings Tile Clays at various Stages of Heat Treatment 128 

32. Showing Trial Pieces of First and Second Warpage Experiments, in 

Place 140 

33. Method of Setting Warpage Trials on Supports 143 

34. Drawing Showing Sagging or Warping of Clay Bars at Different 

Temperatures 144 

35. Warpage, Porosity and Shrinkage Comparisons for Clay A 147 

36. Warpage, Porosity and Shrinkage Comparisons for Clays B and C 147 

37. Warpage, Porosity and Shrinkage Comparisons for Clays D and E 148 

38. Warpage, Porosity and Shrinkage Comparisons for Clays F and G 148 

39. Warpage, Porosity and Shrinkage Comparisons for Clays H and L 149 

40. Warpage, Porosity and Shrinkage Comparisons for Clays T and K 149 

41. Warpage, Porosity and Shrinkage Comparisons for Clays M and N 150 

42. Clay Pit and Transportation System at Ludowici, Ga 169 

43. Quincy Clay Gatherer 172 

44. Quincy Clay Plow 173 

45. Quincy Plow in Action at Pit of Ludowici-Celadon Co., Chicago 

Heights, 111. 174 

46. Quincy Gatherer at Work in Pit of Ludowici-Celadon Co., Chicago 

Heights. 111. 174 

(7) 



8 BULLETIN ELEVEN 

ILLUSTRATIONS-ContinoccL 

No. Title. Page. 

47. Shale Bank of the United States Roofing Tile Co., Parkersburg, 

W. Va. 176 

48. Clay Pit No. 1, Huntington Roofing Tile Co., Huntington, W. Va. 178 

49. Clay Pit No. 2, Huntington Roofing Tile Co., Huntington, W. Va. 178 

50. Entrance to Shale Mine, Murray Roofing Tile Co., Clove'rport, Ky. 184 

51. Motor-driven Centrifugal Pump, in Use at Clay Pit of Ludowici- 

Celadon Co., Chicago Heights, 111. 186 

52. Shale Bank and Car of Western Roofing Tile Co., Coffey ville, 

Kansas 191 

53. Home-made Winding Drum, in Use at United States Roofing Tile 

Co., Parkersbure, W. Va 192 

54. Shale Bank of the Ludowici-Celadon Roofing Tile Co., New Lex- 

ington, Ohio 194 

55. Conveyor, from Pit to Factory — Detroit Roofing Tile Co., Detroit, 

Mich. 196 

56. Clay Pit of Detroit Roofing Tile Co., Detroit, Mich 196 

57. Pulverizer or Disintegrator, at Works of National Roofing Tile Co., 

Lima, Ohio 206 

58. Sectional View of Disintegrator 207 

59. Chaser Mill 208 

60. Clay Dryer, Substantially as Arranged at the Chicago Heights 

Plant, Ludowici-Celadon Co. 211 

61. Home-made Rotary Dryer Installed by the Detroit Roofing Tile 

Co., Detroit, Mich. 212 

62. Piano-wire Screen 221 

63. The "Perfect" Clay Screen 223 

64. Wet Pan, with Shovel 231 

65. Combined Pug Mill and Auger Machine, as Built by The J. D. 

Fate Co. 236 

65A End View of Double Pug Mill and Auger Machine 238 

66. The Crawford & McCrimmon Roofing Tile Press 252 

67. The Grath Roofing Tile Press 254 

68. Earlv Form of the Rogers Roofing Tile Press 256 

69. The ^Rogers Machine Tool Co.'s Roofing Tile Press 256 

70. The American Clay Machinery Co.'s Roofing Tile Press 258 

71. The Klay Roofing Tile Press (National Works, Lima, Ohio) 258 

72. The Grath Trimmings Press (Illinois Supply & Construction Co.) 260 

73. Trimmings Press, Made by the American Clay Machinery Co. 262 

74. The Rogers Trimmings Press 264 

75. The Mueller Hand Press 264 

76. The Laeis Trimmings Press, made by E. Laeis & Co., Trier, Germany 266 

77. The Jaeger Trimmings Press 267 

78. The Klay Trimmings Press (National Works, Lima, Ohio) 267 

79. Tile Trimmer in Use at the United States Roofing Tile Co. 268 

80. Single Stream "Beaver Tail" Shingle Tile Die and Cutter, Made by 

Th. Groke, Merseburg, Germany 274 

81. Quadruple Stream "Beaver Tail" Shingle Tile Die and Cutter, Made 

Th. Groke, Merseburg, Germany 274 

82. Hand Mold for Shingle Tiles 276 

83. Plaster Mold for Shingle Tiles 278 

84. The Mueller Shingle Tile Die 279 

85. The Murray Shingle Tile Die 280 

86. Shingle Tile Die Used by the United States Roofing Tile Co. 280 

87. The Brewer Shingle Tile Die 281 

88. Mueller's Reel Shingle Tile Cutter, Sold by The Illinois Construction 

& Supply Co., St. Louis. 282 

89. Roofing Tile Bar in Block Form, with points indicated at which the 

cuts are made to divide it into separate tiles 284 

90. Vertical Delivery of Shingle Tiles in Block Form 286 

91. The Robinski Lug-cutting Apparatus 287 

92. Pressed Shingle Tiles, Made by the United States Roofing Tile Co. 287 

93. Cutter and Tile Blanks, United States Roofing Tile Co. 289 

94. Feeding Side of the Roofing Tile Press, United States Roofing Tile Co. 289 



GEOLOGICAL SURVEY OF OHIO. 9 

JLLUSTRATIONS-Contintied. 

No. , Title. Page. 

95. Offbearing Side of the Roofing Tile Press, United States Roofing 

Tile Co. 291 

96. Press-made Shingle Tiles, United States Roofing Tile Co. 291 

97. Hand-power Press, Western Roofing Tile Co. 293 

98. Spanish Tile Die, Used by The Cincinnati Roofing Tile & Terra 

Cotta Tile Co. 294 

99. Spanish Tile Cutter, Made by the American Clay Machinery Co. 295 

100. Trowel Used for Removing Spanish Tiles from Cutter 296 

101. Plunger Machine Making Spanish Tiles at Cincinnati Roofing Tile & 

Terra Cotta Co. 298 

102. Tiles Delivering from Press — Detroit Roofing Tile Co. 298 

103. Home-made Reel Cutter for Blanks — Ludowici-Celadon Co., 

Alfred. X. Y. 299 

104. New Lexington Auger-made Interlocking Tiles 302 

105. Auger-made Interlocking Tiles 303 

106. Die Shells and Matrix for Making Plaster Dies 304 

107. Press for Plaster Dies 305 

108. Press for Plaster Dies at Detroit Roofing Tile Co., Showing Mold 

in Position ' 307 

109. Angle Frames for Cutting Hip and Valley Tiles 311 

110. Perspective View of Hip and Valley Cutting Table, Detroit Roofing 

Tile Co. 311 

111. Table for "Closing" Hip and Valley Tiles, Detroit Roofing Tile Co. 312 

112. "Closed" Hip Tiles 314 

113. "Closed" Valley Tiles 314 

114. "Closed" Eave Tiles 314 

115. Cincinnati Roofing Tile Co.'s "Closure" for Eave Tiles 314 

116. Ridge or "Top" Tiles 316 

117. Section of Shingle Tile Roof, Showing Top and Bottom Tiles in Place 316 

118. Crestings 317 

119. Hip Rolls 318 

120. Raymond Hand Press, Working on Hip Rolls at Cincinnati, Ohio 319 

121. Adjustable Pitch Board for Drying Crestings 320 

122. Details of Pitch Board 320 

123. Cutting Table for Handling Half-round Tiles for Hip Rolls 320 

124. Cutting Horse for Conical Hip Rolls 321 

125. Hip "Starters" 322 

126. Plain Hip Saddle 323 

127. First Stage of the Finial 323 

128. Completed Finial 323 

129. Modelers at Work at Mound City Roofing Tile Co. 324 

130. Modelers at Work at National Roofing Tile Co. 325 

131. Finials 326 

132. Tower Finial Table 327 

133. Tools Commonly Used by Clay Modelers 327 

134. Tower Covered with Spanish Tiles 328 

135. Floor Hooks Used in Laying Out Tower Tiles 328 

136. Perspective View of Method of Laying Out Tower Tiles 329 

137. Spanish Tower Tiles 329 

138. Mitered Valley Tiles 330 

139. Ventilator and Special Forms of Ridge Tiles 332 

140. Interior of Building, Showing Use of Glass Tiles, Furnished by 

Ludowici-Celadon Co. 332 

141. Dryer Used by The Cincinnati Roofing Tile & Terra Cotta Co. 338 

142. Buggy of Dry Tiles on the Way to the Kiln 340 

143. Steam Coils 342 

144. Fan for Dryer 344 

145. Plan for Dryer at United States Roofing Tile Co. 346 

146. Ground Plan of Groveport System of Heating Air for Drying Pur- 

poses 352 

147. Sectional Views of the Stove Used in the Groveport System 354 

148. Sketch of Proposed Regenerative Hot Blast Stove Installation Ap- 

plied to Drying 356 



10 BULLETIN ELEVEN 

ILLUSTRATIONS— Concluded. 

No. Title. Page. 

149. Waste Heat Tunnel Dryer at Ludowici-Celadon Co., New Lexing- 

ton, Ohio 358 

150. Dryer Fan at Western Roofing Tile Co. 360 

151. Wooden Shingle Tile Pallet .362 

152. Interlocking Tile Pallet 363 

153. Spanish Tile Pallet 364 

154. Pallet for Press-made Spanish Tiles 365 

155. Three-section Dryer Car with Loose Racks 366 

156. Two-section Dryer Car, with Fixed Racks 367 

157. A Home-made Car 368 

158. End or Bench Braces in Round Kiln of Spanish Tiles 371 

159. Ordinary Way of Setting Shingle Tiles 372 

160. Showing High Shrinkage in Boxes of Burned Shingle Tiles 373 

161. Method of Setting Shingle Tiles Flat, in Use at Murray Roofing 

Tile Co. 374 

162. Waste-strip Method of Setting Shingle Tiles 376 

163. Kiln Partly Set with Interlocking Tiles, Western Roofing Tile Co. 377 

164. Setting of Auger- made Spanish Tiles, The Cincinnati Roofing Tile 

& Terra Cotta Co. 379 

165. Kiln of Interlocking Tiles, Set Without Supports — National Roof- 

ing Tile Co., Lima, Ohio 381 

166. Doorway of Kiln Filled with Interlocking Tiles — Ludowici-Celadon 

Co,, Ludowici, Ga. 381 

167. View in Kiln at Detroit Roofing Tile Co. 383 

168. Drawing of a Typical Terra Cotta Setting 383 

169. Setting of Tiles and Terra Cotta — National Roofing Tile Co., Lima, 

Ohio 385 

170. Doorway of Kiln, Showing Mixed Setting — Mound City Roofing Tile 

Co., St. Louis, Mo. 385 

171. Center-stack Down-draft Kiln — United States Roofing Tile Co., 

Parkersburg, W. Va. 391 

172. Round Down-draft Kiln — The Cincinnati Roofing Tile & Terra 

Cotta Co., Cincinnati, Ohio 393 

173. Gas Producer Furnace Under High Fire — The Cincinnati Roofing Tile 

& Terra Cotta Co., Cincinnati, Ohio 395 

174. Double-furnace, Down-draft Kiln — Ludowici-Celadon Co., New Lex- 

ington, Ohio 305 

175. Stewart Kiln, National Roofing Tile Co. 403 

176. Mitchell Kiln, in Use at Detroit Roofing Tile Co., Detroit, Mich. 405 

177. Outside View of Mitchell Kiln — Detroit Roofing Tile Co., Detroit, 

Mich. 407 

178. Stock Yard, Showing Manner of Piling — Chicago Heights Plant 

Ludowici-Celadon Co. 440 

179. Storage Shed for Spanish Tiles— Cincinnati Roofing Tile & Terra Cot- 

ta Co., Cincinnati, Ohio 440 

180. Car Loaded with Roofing Tiles, Showing Method of Bracing 442 

181. General View of Plant of Huntington Roofing Tile Co., Huntington, 

W. Va. 444 

182. General View of Plant of the United States Roofing Tile Co., Par- 

kersburg, W. Va. 446 

183. General View of the Plant of the Western Roofing Tile Co. (since 

taken over by the Ludowici-Celadon Co.), at Coffeyville, Kan. 448 

184. General View of the Plant of the Ludowici-Celadon Co., at New 

Lexington, Ohio 450 

185. General View of the Plant of the Murray Roofing Tile Co., at 

Cloverport, Ky. 452 

186. General View of the Plant of the Ludowici-Celadon Co., at Chicago 

Heights. 111. 452 

187. Hypothetical Ground Plan of "Combination" Roofing Tile Plant 

Inserted between 462-463 



CHAPTER L 

A BRIEF HISTORY OF ROOFING TILE MANUFACTURE 

AND USE. 

General — The origin of roofing tile is shrouded in obscurity. It 
can, however, be traced back several centuries before Christ. Early in 
man's career, he doubtless lived in such caves and natural shelters as are 
found in a mountainous country, but, as he migrated from place to 
place, it would happen that natural shelters could not always be found. 
The impulse and suggestion for him to construct temporary caves, or shel- 
ters of slabs and pieces of rock, would be a perfectly natural one and 
doubtless has recurred many times in various places and peoples in the 
development of the human race. These early homes were no doubt covered 
with some sort of thatch or stone roofing material ; in mountainous coun- 
tries flat stones of flaggings would naturally be tried. Experience unques- 
tionably soon taught these early home builders the value of a sloped roof 
over a flat one, in shedding the rains. 

According to Morse^, the antiquity of the sloping roof is hinted at 
in the finding of cinerary vessels in the form of huts, and, consequently, 
known as hut-urns. These have been found in Italy, Saxony and other 
parts of southern Europe. It is believed they were made before the age 
of iron. 

The sloping roof must have preceded the roofing tile by many cen- 
turies. At the outset, bark, straw, thatch, rough stones and similar sub- 
stances were used until better devices were made, which finally culmi- 
nated in roofing tile of terra-cotta. The oldest known type of clay roofing 
tiles is, by far, the most common form in use in the world to-day. 

jVIost natural stones crumble, and metals oxidize or rust, but hard 
burned clay w^ares are nearly imperishable to the influences of- decay. 
Thus it happens that terra-cotta roofing tiles are often the only surviving 
relics of a prehistoric structure. The enduring nature of these objects 
may ultimately enable us to trace the paths followed by the tile-making 
races in their various migrations. 

While the actual beginnings of roofing tiles are not known, it is prob- 
able that their use was known very early in Asia Minor, and certainly 
very early in China. From the high skill of the potters and the great 

> Morse, E. S. "On the Older Forms of Terra-Cotta Roofing Tiles." 
Amer. Arch, and Building News [1892] vol. 35. p. 197. vol. 36, pp. 5, 24, 52. 
This article has been freely used in various parts of this chapter, for which 
due acknowledgment is hereby rendered. 

(in 



12 



BULLETIN ELEVEN 



antiquity of tlie fictile art in China, and the use of artistic roofinij tiles 
in that country in buildings erected some centuries ago, one might easily 
be led to believe that it was in China that the use of roofing tile originated. 
Graeber, in his memoir " Terra-kotten am Gieson," describes what 
he believes to be the earliest known terra-cotta roofing tile. These were 
found in the ruins of the Temple of Hera at Olympia, dating nearly 
a thousand years bolore Christ. This ancient tile consisted of two el- 
ements, a wide under piece (tegula) slightly curved, and a narrow, semi- 
cylindrical piece (imbrex) which was placed in an inverted position so 
83 to cover the upturned etlges of two adjacent tegulae. While the tiles 
from the Temple of Hera are probably as old as any authenticated in- 
stances elsewhere, it is not to be supposed that the Greeks sprang all at 
once from the thatched hut of the wild sheep-herder, up to the level indi- 
cated by this efficient system of tile roofing. It is Imown that the begin- 
nings of their other arts, pottery making, metal working, jewelry, sculp- 
tures, etc., were imported from older civilizations in Asia Minor, or else- 
where, and that while the genius of the Greeks soon developed all of these 
arts to a plane never before known in the world, they cannot be credited 
with their first discover;'. 

Among the substances used 
I in the construction of early 
, . ■— - roofs, worked marble tiles, 
f*.'^BMJ modeled after the terra-cotta 
I tiles, were made some 650 
I yeara before Christ. 
Fig. 1-Tiles from the Temple of Hera. Throughout all parts of the 

old world can be found tiles or the fragments of them, proving to us 
that the use of tile has been universal there at one period or another. 

The outline drawings' (Figure 2} represent in a general way the 
types and varieties of roofing tiles with their age and di'itribution. 



The Orient. An- 
cient Greece and 
Italy. 




m^: 




Normal or Asiatic 
Tile Designs. 



The Orient. Asia 
and Mediterra- 
nean Countries. 

,^1^. .^"^k .^^ .^^ Greece, Italy(An- 

\jr\jr\jr\jr\ ^^^^ ^^-^ ^''^■ 

Fig- 2 
H should be understood that colonies, past and present, usually 
adhere to the form of roofing tile in use in their parent countries. As 

' After Morse. On the Older Forms of Terra Cotta Roofing Tile. Amer. 
Archt. and Building News, (1892). Vol. 35. p. 198. 



GEOLOGICAL SURVEY OF OfflO. 



13 



an illustration,^ flat tile made in Montgomery County, Pennsylvania, 
about 1735, can be traced to the old German settlers. At Bethlehem, 
Pennsylvania, the Moravians were making tile as early as 1740.^ The 
pan tile discovered by Dr. C. C. Abbott^ on Burlington Island, in the 
Delaware River, on the site of a very old house, said to have been built 
in 1668 by Peter Jagon, points clearly to the Dutch settler as its author. 
In California and Mexico, the normal or half round tile used in the 
missions were made by the early Spanish conquerors. 

England and 
Scandinavia. 




Pan or Belgic 
Tile Designs. 





Belgium, Hol- 
land, Scandi- 
navia, Java 
and Japan. 



Fig. 2 — Continued. 



Modern, vari- 
ous countries. 



The tiles found in the above descril)od localities are believed to rep- 
resent the first use of roofing tiles in this country. It is quite possible 
that some of the first tiles used were brought from home by the colo- 
nists from their respective countries. 

Ohio — Taking up the history of roofing tile in Ohio, it has been 
found a problem of less magnitude to trace their developtnent. 

On a branch of the Cincinnati Northern Railway, some thirty miles 
to the northeast of Cincinnati, is found the quaint old village of German- 
town, which the records seem to indicate as the site of the first roofing 
tile manufacture and use in Ohio. 

During the year of 1814,* ^Ir. Philip Qunckel laid out the village, 
and named it after Germantown, a suburb of Philadelphia, whirjh still 
retains that title. About this time a Mr. John Robinson cast his lot with 
the early settlers of the little to^\^l, and began the manufacture of brick 
from clay gathered in a nearby field. Wishing to build for himself a 
home that would outdo those of his pioneer neighbors, Mr. Robinson made 
clay roofing tiles in quantity sufficient to cover his home and stable. 
Figure 3 shows very clearly the form and outline of the tile made by ^Ir. 
Robinson. These tiles were no doubt made from the same clay, and burned 
in the same kilns, as the brick which Mr. Robinson manufactured. The 
house has long since been destroyed, but the old stable withstood the 
ravages of time and storm until 1907. It was razed to make way for 

* Barber, E. A. Pottery and Porcelain of United States, p. 51. 
' loc. cit. 

• loc. cit. 

< Howe's History of Ohio. Vol. 2. p. 301. 



14 BULLETIN ELEVEN 

a fine library building. The ptiot<^raph shown in Figure 4 was taken 
just before the work of destroying the old building was begun. 

The view of the stable shows the roof in a dilapidated condition, 
not from the failure of the tiles or brick in the structure, but from the 
rotting of the wooden beams and rafters, so that they could no longer 
carry their load. 



Fig. 3^Robinson's Tile, made at Germantown, Ohio, about 1814. 

To the right in the picture stands a comer of the new library build- 
ing, upon which can be seen roofing tiles of modem manufacture. A 
more striking contrast could scarcely have been found, the one tile show- 
ing the marks of time and the primitive methods of manufacture of a 
century ago, while the other presents a roof of the present day. 

The Robinson tile at G«rmantown was probably a sporadic ease 
only, and does not probably stand for the introduction of the industry, 
as we have no evidence that he manufactured tiles for other than his own 
needs. 

Unquestionably, the next step in the production of roofing tile 
in Ohio was taken by the Zoarites, a German religious sect, who settled 
in Tuscarawas County about 1820, and built a town which they called 
Zoar. The manufacture of roofing tile by these people was upon a much 
larger scale than the early efforts of Mr. Robinson at Germantown, as 
practically all of their buildings were tiled. One only has to look upon 
the many old roofs that can still be seen standing today at Zoar, to 



GEOLOGICAL SURVEY OP OHIO. 15 

Tpcognize that the use of roofing tiles was not new to the people of 2oar. 
They came from a country where tiles had been used for centuries before 
they sailed away to build their Utopia in the wilderness, where they could 
be free to follow their own beliefs. The Zoar community has disbanded 
after « communal existence of about eighty years, but their honest work- 
manship and care have left buildings and roofs which will last for many 
decades to come. 



Fig. •■ 



These Zoar tiles are shingle tiles of the pattern known as the "Beaver 
Tail," the outline and style of which can be traced back to their native 
town, Wurtemburg. The tiles were all hand made; the clay was dug 
in the nearby fields, liauled to the tile yards by oxen, dumped into soak- 
pits, where water was added and the clay allowed to stand till soft. 
After soaidng for a day and night, men tramped the clay with their bare 
feet until it was properly kneaded or pugged. It was then covered over 
with straw, weighted with rails or boards, thus keeping the clay plastic 
until needed by the molders. It was then spaded out, and carried by 
iiand to the small workbenches of the molders. Wooden molds were used, 
which were previously wet and then sprinkled with sand. The molder 
first took up a lump of clay, which he rolled into a long tapered roll. 



16 BULLETIN ELEVEN 

similar id shape to a loaf of rye bread. This roll of clay was tlicn 
thrown or slammed forcibly into the center of the mold, and the molder, 
using his forearm and hand, would hammer or manipiilate the clay 
until it completely filled the mold. The excess clay was then scraped off 
with a straight edged stick. Ordinarily the tile would have been consid- 
ered complete at this point, hut hy observing the tiles shown in the illus- 
trations, it can be seen that their faces have been grooved with gutters, 
or lines running lengthwise of the tile. These grooves were produced 
by the fingers of the workmen, each finishing his tile with lines that 
seemed most appropriate to him. 



Fig. 5 — Roofing Tiles made by the Zoar Community. 

A two-fold purpose was filled by these grooves: first, they hn-ke the 
monotony of the otherwise ])lain tile, and secondly, they furnished a 
means of keeping the rain water away from the lateral joints. 

The tiles were carried frcm the molding benches by boys, to drying 
racks or fioors, where they were emptied out from the molds and left to 
drj'. The mold was carried back to the work ben:'h, where it was first 
dipped in water and then sprinkled with sand, in readiness for another 
operation. 

The burning was carried en in up-draft kilns similar to the up-draft 
clamp kilns used by manufacturers of soft mud bricks at the present time. 

Tile manufacture was carried on by these <iuaint people until 
about 1852, when it was discontinued. As at Germantown, the tiles made 
at Zoar were not designed for commercial purposes, biit merely to be 
used on the mills, store houses, shops, houses and barns of the Zoiir 
community, amounting in all to a considerable number of structures. 



GEOLOGICAL SURVEY OF OHIO. 17 

The next step in the evolution of the manufacture of roofing tile 
in Ohio and probably the earliest establishment of the industry on a 
commercial basis in the United States, came during the year 1871, when 
Mr. J. B. Hughes of Terre Haute, Indiaua, received letters patent on 
roofing tile of interlocking design, and at the same time on a machine 
to make such tiles. 



Fig, 6— Old Church at Zoar, Ohio. 

Among the first to become interested in the Hughes tile, was John 
W. Conrade of Zanesvitle, Ohio, who during the year 1873 purchased 
the right to manufacture the Hughes tile. Mr. Conrade opened a small 
plant during the fall of the same year and carried on the manufacture 
of Iho tile during tlie following winter. No roofs were covered, hoivever, 
until the spring of 1874, when the residence of Mr. A. H. Watts in 
Zanesville was constructed with this tile. The Conrade factory did not 
continue lung in operation. 

Closely following the starting 0^ the Conrade plant at Zanesville, 
Mr. Edwin Bennett at Baltimore, Maryland, embarkcfl in roofing tile 
manufacture. In the beginning, the Bennett plant was also operated un- 
der the Hughes patents. Mr, Bennett was ivithout doubt the second man 
in this country to take up the manufacture of roofing tile on a com- 
mercial scale. His plant was opened in 1876 and was in continuous opera- 
tion up until the summer of 1908, when, owing to the death of Mr. Ben- 
nett, operations were stopped and it has since been dismantled. 

Arriving in this country in 1841 from Woodville, Derbyshire, 
England, Mr. Bennett* joined his brother James Bennett at East Liver- 

' Barber. E. A., Pottery and Porcelain of the United States, p. 192. 
z— G. B. 11. 



18 BULLETIN ELEVEN 

pool, Ohio, in a small pottery works which liad been started in 1839 at 
that point, and which was undoubtedly tlie first pottery to be built at 
East Liverpool, and the foundation of the enormous industry ivhicli has 
developed t lie re. 



During 1»46 Mr. Edwin Bennett severed his connection at East 
Liverpool, and moved to Baltimore, where he founded a whiteware pot- 
tery which is still in successful operation to-day. But, becoming inter- 
ested in roofing tile in ISTfi, he embarked in the bu-siness in a small way. 
His entrance into this field was interesting, in that it marked a line of 
growth very unusual at that time and stiil so. The Ensclish potter as a 
rule has great pride in his craft, and a proportionate distaste for the 
other branches of clay manufacture, especially bricks and tiles, wbicli he 
regards as on an entirely different plane from his own. But Mr. Ben- 
nett's vision was prophetic, in that he saw the ultimate importauce of 
roofing tiles and the certainty of their use in enormous quantities, and 
he decide<l to apply his knowledge of clay manufacture to this new line. 
Unfortunately bis efforts were largely premature, as the markets had 
not been at all educated to the use of tiles. 

A year or so hiter. in I S77-78, Mr. Harris B, Camp at Cuyahoga Palls, 
Ohio, entered upon rooting tile manufacture. 

Mr. Camp had a most interesting personality. He owned a factory for 
the manufacture of sewer pi])OS and hollow goods, and also a machine shop 
of considerable size, wliere he did a custom trade as well ns liuilding and 
repairing bis own clay machinery. He was an inventive genius of a high 
order, but of the rare type that makes liis ideas pay. He experimented 
continually, seldom doing tlie same thing twice alike, even when success- 
ful. He became very wealthy before his death. 3tr, Camp's efforts in 
the roofing tile field were directed to the mannfacture of the well known 



GEOLOGICAL SURVEY OP OHIO. 19 

diamond shaped pattern, invented by Courtois in France prior to 1856. 
He only continued a short time in this branch of clay manufacture, 
when he sold his interests to Mr. J. C. Ewart of Akron, Ohio. 

^Ir. Ewart took up the work with much faith and energy, and has 
unquestionably done as much or more than any other man to promote 
the use of roofing tile in the United States. The plant w^hich he built 
at Akron in the late seventies was strengthened step by step and for 
many years held the record of being the largest and practically the only 
successful plant of its kind in this country, as the Bennett plant did not 
at any time assume large proportions, and was not largely known in the 
trade. Mr. Ewart 's success in his business was due entirely to his energy 
and application. He accomplished what he did almost entirely by 
his own efforts, relying very little on exchanging ideas with other clay 
workers. He solved his own problems in his own way, and did this 
at a time before clay w^orking had begun its modern expansion and con- 
trol along chemical and mechanical lines. His methods, and especially 
his exclusiveness, did not enable him to retain the control of the business 
which he had by great labor secured. Opposition began to develop, and 
ultimately his position became diflScult. He finally withdrew from the 
business a few years ago, the plant being taken over by the present firm, 
The Akron Vitrified Roofing Tile Co. 

It was not until a number of years after the starting of the Akron 
plant, that the roofing tile business was taken up by other manufacturr 
ers throughout the state. Among them was The Repp Roofing Tile Co., 
New Philadelphia, Ohio, about 1893; The Barnard Tile Co., Bellaire, 
Ohio in 1893 ; Zanesville Roofing Tile Co., at Zanesville, Ohio, in 1895 ; 
another one at Ottawa, Ohio, in 1900. None of the above plants operated 
to exceed three or four years at the longest, and none were successful 
in founding successful industries. About the same time, i. e., in 1895, 
a plant known as the Cincinnati Roofing Tile and Terra Cotta Co. was 
started at Winton Place, near Cincinnati, by IMr. Jacob Freund, inspired, 
as many of our German citizens are, with a true love and appreciation 
of a good tile roof. 

Starting in a very modest way, this plant was built up step by step 
by its founder and associates. The problems of manufacture here were 
studied independently and met in their own way, as in the Akron plant, 
and while the product was of different shape and design, the business 
became slowly successful. It was founded on solid experience at every 
step of the way, and succeeded where the other plants of its own age failed, 
chiefly because it was not a copy of any other plant and because it 
evolved its own methods. 

In 1902 a roofing tile plant at New Lexington, Ohio, was erected 
by a company of which Mr. A. W. Brown was President. This plant, 
at the time of its building, was designed upon broad lines, with ample 



20 BULLETIN ELEVEN 

provisions for enlargement, and, in its short career of eight years, has de- 
veloped into the next to the largest, if not the largest, roofing tile plant 
in the United States. 

Following, the New Lexington plant was one at Lima, Ohio, The 
National Roofing Tile Co., built by Mr. A. B. Klay, a native of Switz- 
erland. Having been born and reared in a country where tile roofs have 
been the main reliance for centuries, it was only natural that Mr. Klay 
should see the great possibilities for roofing tile in this country. 

Since gathering the field notes for this report, during the summer 
of 1908, a company has been formed at Canton, to build a plant at Spar- 
ta, Ohio, to manufacture dry-pressed roofing tile. 

Other States— Considering the establishment of plants outside of 
Ohio, the Mitchell Clay Co.* during the year 1866 undertook the manufac- 
ture of roofing tile at St. Louis. They were, however, in advance of the 
times and after a period of about five years they discontinued the manu- 
facture of this line of goods. 

Other attempts were made at several points throughout the country, 
none of which met with success until the starting of the Celadon Terra 
Cotta Co., of Alfred, New York, built in 1888 by Mr. Geo. Babcock. 
This plant was one of the pioneers, and has been in continuous operation 
from the time of its building. At present it is one of the plants owned 
by the Ludowici Celadon Co., of Chicago, 111.^ During 1890 a plant for 
the manufacture of roofing tile was built at Ottawa, III., and known as 
the Chicago Terra Cotta Roofing and Siding Tile Co. It was operated 
by various owners for about twelve years and then was dismantled. 

About 1893 the Ludowici Roofing Tile Company was formed in 
this country and built a plant at Chicago Heights, Illinois. This plant 
has grown steadily from the start until today it ranks among the largest. 

The next plants of importance were the Standard Roofing Tile 
Company, St. Louis, built in 1895, and the Ohio Valley Clay Shingle 
Company, now the Huntington Roofing Tile Company of Huntington, 
West Virginia, built in 1899. During the following year, 1900, the 
Ludowici Roofing Tile Company built a plant at Liberty City (now 
Ludowici) Georgia. 

It was not until three years later that other plants were built. 
During the year of 1903 there were three plants built. The United States 
Roofing Tile Company, Parkersburgh, West Virginia, The Mound City 
Roofing Tile Company, St. Louis, Missouri, and the Western Roofing 
Tile Company, Coffeyville, Kansas. The next year or during 1904, 
The Murray Roofing Tile Company was built at Cloverport, Kentucky ; 
following this company was the building of the Detroit Roofing Tile 
Company in 1906. 

'Whaler, H. A., Mo. Geol. Surv., Vol. XI, p. 436. 
^Destroyed by fire in fall of 1909.. 



GEOLOGICAL SURVEY OP OHIO. 21 

The latest company to enter the roofing tile field is the New York 
Roofing Tile Company at Saugerties, New York. 

Other companies that are manufacturing or have manufactured roof- 
ing tiles, either alOne or in connection with other clay* products, are: 
The Alfred Clay Company, Alfred, New York; Bums and Russell, 
Baltimore, Maryland; Golden Press Brick Company, Golden, Colorado, 
Los Angeles Pressed Brick Company, Los Angeles, California ; Gladding, 
McBean & Co., Lincoln, California; The Steiger Terra Cotta & Pottery 
Co., South San Francisco, California; N. Clark & Sons Co., Alameda, 
California; The Carnegie Brick & Pottery Co., Tesla, California; The 
Clay Shingle Company, Montezuma, Indiana ; Spillman Brick Company, 
Spillraan, West Virginia, and probably a number of others. 

Status of Manufacture Outside of United States— Roofing tiles are 
now manufactured in all parts of the world occupied by civilized races. 
In the far East we find well established industries in China, Japan, Java, 
India and the islands of the Asiatic coast. The manufacture of tiles in 
these countries is possibly not as great at the present time, as it has been 
in the past, owing to the frequent relaying of the excellent tiles, made 
years ago by their ancestors, on modem structures. 

It can be said of the Chinese, that they excel all other races in the 
world in their skill in the use of roofing tile. Estates and residences 
are generally bounded by high brick walls, crested with tiles, and even 
the most common country homes have at least a tile-covered gateway,, 
while temples, shops, and all buildings of the better class are tile covered 
as a matter of course. Moreover, China, Korea and Japan have all 
treated the roofing tile in an artistic w^ay apj^roached by no other coun- 
tries, excepting Greece and Italy. 

Passing on to Persia, Egypt and the countries bordering on the south 
and east coasts of the ^lediterranean Sea, we find that many tiles are still 
used, and that they retain for the most part the old normal pattern. 

In Italy, Switzerland, Spain, Asia Minor, Austria, Norway, Sweden, 
Belgium and Holland are many thousands of tiled roofs, but these 
countries are not properly called large producers of roofing tiles. 
They do not manufacture many tiles in excess of those needed for 
domestic use. On the other hand, Germany, France f\nd England are 
all large manufacturers of tiles. They annually produce many S(iuares 
for export purposes to South Africa, South and Central America, and 
the West India Islands. Some few tiles are manufactured in these latter 
countries, but their supply is for the most part imported. At Maracaibo, 
Venezuela, there are two plants making tiles: The Eastern Brick and 
Roofing Tile Co., which has been in operation for the last fifteen years, 
producing roofing tile by means of a French hand-power press, and 
the Western Brick & Tile Co., using a similar equipment. The combined 



22 BULLETIN ELEVEN 

output of these two ])lants is naturally small, and hence the bulk of the 
demand has to be met by importations. 

At JNIontevideo, Uruguay, Mr. John W. Tiara, U. S. Consul, re- 
ports that the -majority of roofs in that country are flat, like floors, being 
paved or covered with flat tiles like the English ** quarries," locally 
known as *'baldosas. " Many thousands of these are annually used, and 
he reports that in a single six months 2,537,000 were imported, largely 
from England. 

A vast amount of business in these southern countries is yearly 
lost to the United States, due partly to the scarcity of roofing tile plants 
in this country, more especially cji our southern, southeastern and 
southwestern sea board. At present we have only one plant in this vast 
territory, viz., at Ludowici, Georgia. This situation is also undoubtedly 
due in considerable i»art to our insufficient and irregular lines of com- 
municaticn with these countries. American ships are rare in those wat- 
ers and the bulk of American exports to them go in foreign bottoms. 
Another cause is the lack of knowledge of our American producers as 
to what is wanted by these southern neighbors, and generally a ten- 
dency to impatience with their demands for special shapes and st^^les. 
The English and Germans have secured the trade, by findins: out what 
the customs of the country require, and supplying it, while Americans 
have in some instances adopted a '*take it or leave it'' policy which is 
very unsuccessful in securing trade. 

Some tiles are produced in Cuba and Mexico, but only in the slow 
and primitive manner brought in by the Spaniards three hundred 
years ago. 

In Australia many tile plants have been put into operation by tlic 
English, German and French settlers. 

Status of Manufacture in the United States^- While the first manu- 
facturing of roofing tiles in this country has been shown in the preceding 
pages not to be of recent date, it is nevertheless a comparatively new in- 
dustry here. We have been slow in taking up the use of roofing tiles 
for several reasons which are discussed in detail a little later. At pres- 
ent, however, American ingenuity in this field, as in many others, has 
triumphed over time and tradition. Although slow to enter this field, 
our progress since entering it has been rapid, and American tiles today 
have many points cT excellence, and seme of superiority. From the 
crude presse-s brouglit into this country from Germany, England and 
France, our inventors have developed new roofing tile ma(;liinery that 
leads the world in simplicity, strength and output. Many improvcTnents 
in the materials of which dies are made, and also in the construction 
of dies, have been made in the past few years, until now the time honored 
plaster die is to be found in but few^ roofing tile plants. The chief objec- 
tion to i)laster dies has been that they must be renewed daily, owing 



GEOLOGICAL SUKVEY OF OHIO. 



23 



to the rapid rate at w)iich the soft plaster surface wears away, leaving the 
tile made upon them with a very rough and uneven exterior, which 
catches dust and dirt, and soon presents anything hut an attractive ap- 
pearance. To overcome these objections, our manufacturers have em- 
ployed dies made of such materials as cast iron, steel, brass, gun-metal, 
aluminium, and various alloys, all of which are being used with more or 
less success. 







Fig. 8 — Map of the United Staxes, Showing Distribution of the Roofing Tile 

Plants. 



In the past thirty years, the capacity of the roofing tile plants in 
this country has grown from the insignificant sum of from twenty-five 
to fifty squares per day, which is about the output of a single average 
plant, up to nine hundred or a thousand squares per day, if worked full 
time. In other words, the output has been increased from that of sulli- 
cient tile per day to cover a single medium sized building, to a number 
that would cover, roughly speaking, about twenty buildings of the same 
size. 

It will be s'^'^n from Figure 8 that with two exceptions the plants are 
centrally located. It will also be observed that Ohio ranks first in the 
number of plants, with West Virginia and New York as second. 



24 



BULLETIN ELEVEN 



Ohio .;....; 

West Virginia . . 


TABLE 


No. 1. 

No. 
Active Plante. 

4 
2 
2» 

Ai 


No. 
Building. 

1 

1 









No. 
Idle 





New York 

Illinois 

Michigan 

Kentucky 

Missouri 










1 


Kansas 

Georgia 

California 










*One of these is in connection with dry press brick. 

*A11 made in factories whose product covers a wide variety of clay wares. 
Roofing tile is not an important item in any of these plants, though made in all. 

Ohio, at the present time, as always in the pa.st, leads all other 
states in the production of roofing tile, as already shown. The first com- 
mercial roofing tile plant in this country was developed in Ohio, at 
Zanesville in 1873, and from the opening of the Zanesville plant, Ohio 
has, at no time, been wdthout roofing tile industry, somewhere in her 
borders. Ohio manufacturers have generally kept abreast of the times, 
and have fought many of the hard battles necessarily encountered in the 
introduction of a new industry. In the face of the cheaper 'natural roof- 
ing materials, and also of the failure of some of the poorly made tiles 
and poorly laid tile roofs of early days, Ohio manufacturers have con- 
tinually sought to produce more and better tiles, and to prove to the most 
exacting architect or builder that there is no other roofing material as 
nearly perfect as a well designed and well made roofing tile. 

Approximately one-third of all the roofing tiles mode in the United 
States are now produced in Ohio, and with the completion of the plant 
now in process of construction, the proportion will probably be raised 
somewhat higher. 

Slow Development of the Indastry in America.- -Why have not 
tiles been used more extensively in the United States in view of their 
very extensive use abroad? There have been several conditions in the 
past which have greatly impeded the development of the industry. Some 
of these conditions still exist in some parts of the country. A discussion 
of these conditions wdll furnish an answer to the above question. 

Firstly. — The competition of the wooden roof should be consid- 
ered. The country is relatively new, and most of it originally abounded 
with magnificent forests of timber, suited for use as shingles. Cleared 
land was, and in some sections still is, at a premium, and any use 
to which the primeval forests could be put was gladly w^elcomed. While 
this surplusage of timber has now passed away forever in the east and 
central portions of the country, which are noAV beginning to feel the pinch 
of scarcity and to realize the awful wastefulness of the past, in some sec- 
tions of the Northwest it is still possible to see enormous quantities 



GEOLOGICAL SURVEY OF OHIO. 25 

of wood ruthlessly burnt, in order to get rid of it. Thus for many years 
the use of other roofs than wooden slabs or shingles was very limited, 
owing to their cheapness and availability. As, time passed and neigh- 
borhoods became towns, and towns cities, disastrous fires have occurred 
which have pointed out the importance of some more fire-proof roofing 
material, since the sliingle-roofed house has formed a vulnerable point 
of attack in every large conflagration in this country, and in thousands 
of small fires. Thus the wooden roof, while still largely used, especially 
in the newer sections of the country, is doomed to a more and more rapid 
extinction, under the joint influences of increasing scantiness of wood 
supply, short life of wooden roofs under favorable conditions, and their 
constant danger of destruction by fire. 

Secondly, — The competition of slate or natural stone. The condi- 
tions described as to the wooden roof have generally been first met by 
resort to slate, a natural stone of highly fissile character, capable of be- 
ing readily sawed up into blocks of proper size, and split into very thin 
slabs of even thickness, which will stand further shaping and punching 
at the point of use. 

The United States is fortunate in having a large natural endowment 
of slate, in widely distributed localities, and these quarries have been 
and will always be a source of much wealth to th^ir communities. 
But slate is not free from faults, though it has many advantages which 
will always entitle it to an important place among roofing materials. 
It is cheap, easily applied, fireproof, and resistant to weather if of good 
quality. On the other hand, it is heavy, it is not resistant to weather 
if it contains soluble minerals, or easily oxidizable minerals like pyrites, 
or if it is not hard enough, i. e., too shaly. Also it is not very resistant 
to blows or strains, is not easy to repair when once laid in place, losses 
in shipping and application are rather high, and it makes a very plain, 
unomamental and uninteresting roof. The last reason is the most impor- 
tant of these, and were it not for this, slate would make the introduction 
of roofing tile a very slow and unprofitable venture. But slate only works 
in planes. It cannot be easily adjusted to curved surfaces, it possesses 
no relief, and makes a textureless roof and therefore one devoid of char- 
acter, and its range of colors is limited to a small variety of blues, greens, 
browns and dull reds. 

Thirdly. — The use of metal roofs, such as sheet iron, plain or coated 
with zinc or tin, and the use of corrugated or crimped or pressed iron 
plates has found a large field. The use of other sheet metals, siich as 
pure zinc, copper or tin, is possible in some few cases, but in general is 
precluded by cost. Tlie use of sheet iron in its various forms has the ad- 
vantage of cheapness, non-combustibility, exceeding lightness, ready 
adaptability to any shaped structure, exceedingly rapid application, 
and easj'- repair, and easy preservation by paint applications. On the 



26 BULLETIN ELEVEN 

other hand, it is very short lived unless thoroughly protected by paint or 
other applications at frequent intervals, and is thoroughly uninterestiug 
in its appearance when finished, unless the pressing has gone to the ex- 
tent of closely imitating roofing tile, in order to get the relief and tex- 
ture. In this case, it is more costly than a metal roof ought to be, and has 
all the faults of any material which merely copies another. 

The field of the sheet metal roof will therefore be likely to grow 
less rather than greater, and it will probably be confined more to fac- 
tories, barns and low class sheds, and less to buildings with pretension to 
architectural merit. 

Fourthly, — Composition roofs, made of sheets of artificial fabrics 
like paper, felt, asbestos, cloth, etc., water proofed with tar, asphalt, 
paint, and numerous patented and secret preparations, and covered 
with surface coatings of sand or gravel, are an important mode of cover- 
ing cheap or temporary structures. Such roofs are largely confined to 
factories, flat roofed stores and store houses, and seldom applied to 
dwellings or important structures of any kind. However, they have the 
merit of cheapness, of water proof character to a very high degree even 
at low angles of pitch, of easy application and easy repair or removal. 
They lose their elasticity and crack and leak, if the filling material is 
allowed to dry out too long without renewal. They often are resistant 
to fire from the outside, though nearly always highly inflammable from 
within. The tar or asphalt roofs cannot be used on heavy slopes on ac- 
count of drainage of the fluid during the summer heat. They are limited 
to strictly utilitarian purposes, having no pretensions to beauty under 
any circumstances. 

Fifthly. — Cement roofing is a new factor in the market, which may 
be applied in two ways: 1st, as tiles made separately and subsequently 
applied and fastened in place, or 2nd, in sheets of reinforced con- 
crete. Of the former, a comparison vnth clay- roofing tiles will be made 
later. Of the latter, the strong points are its rigidity, its fire proof nature, 
its permanence when well made. Against it, lie the probability of bad 
workmanship (or the difficulty of securing good workmanship on which 
its duration and strength directly rest). Cement products in general 
are all open to this difficulty, that it is not easy to tell whetJier they are 
well made or not from their appearance, i. e., scanting in material or 
workmanship is exceedingly difficult to detect and where so much de- 
pendence must be placed on good faith, frequent abuses are always like- 
ly. Also, this style of roof is very heavy, and requires Tuassive construc- 
tion. Light or thin slabs are not satisfactory at all, as they crack if bent 
much or struck smartly. 

E\adently, in competition with these five classes of roofing ma- 
terials, most of them well entrenched in trade practice, roofing tiles 
have had to demonstrate their worth. Tile roofs have been unusual. 



GEOLOGICAL SURVEY OF OHIO. 27 ' 

therefore not easily obtained and often causing long delays in comple- 
tion of a building. They have been heavy, requiring strong con- 
struction and thus more costly. They have been poorly laid, by work- 
men unskilled in their use and oftentimes actually hostile to the new 
rocf and glad to see it become unpopular on account of leaks or early re- 
pairs. They have been inherently more costly. But in spite of all those 
handicaps, and others not mentioned, the use of tile has increased more 
and mere rapidly with each year. Its advantage in the hands of a 
skillful user, in the beauty of form, of surface texture, and of color, 
and its entire satisfactoriness when properly designed, made anti laid, 
so far as weight and water-tight qualities are concerned, its uninflam- 
mable character and its actual resistance to the influence of exterior fire 
or water or both, its durability when properly designed and laid, all 
these and other advantages have been recognized by architects so thor- 
oughly that now the great majority of large institutional buildings, fine 
residences, and others where architectural considerations have weight, 
use the tile roof. It has not yet invaded the field of the cheap roof, and 
it is by no means certain, under American conditions as to both labor 
and materials, that it ever will attain the wide usage which character- 
izes its use in Europe and in the Orient. 

Handicaps — Some of the handicaps by which the use of roofing 
tiles has been limited in the [)ast will, however, undoubtedly be removed 
as time gees en. In the first place, the design of a roofing tile, which can 
meet the exacting conditions cf modern use, is becoming a less varied 
and more definite thing. Many fanciful, impractical and clumsy tiles 
have been "invented" cr designed by various enthusiasts and their 
introduction has tended to hurt the cau.se and delay the use of the de- 
signs which are practical, ^lany cf these theories have had to be tried 
cut and lived down afterward*^. ]\Iany of the leaky roofs and most of the 
slowness cf tile rcof construction has been due to poor design, part 
of it to poor workmanship. Secondly. — The weight of the early tile roof 
was excessive. Better machinery, better driers, better kilns, and more 
knowledge and experience on the part of the makers have overcome this 
objection in large part, and tile roofs are now furnished in which the 
weight consideration is no longer of much importance. Thirdly, the mul- 
tiplication of plants will remove one cf the biggest obstacles to the growth 
of the industry. With the avoidance of the excessive freight costs, and 
with the elimination of the delays caused by long shipments and frequent- 
ly by congested factory conditions, there will come a great expansion in 
the use of tiles, not only from an economical standpoint, but from the side 
01 artistic beauty, attainable by no other roofing material. With tile 
it is possible to get an everlasting roof in any pattern and of any desired 
•color. The color is contained in a vitrified body, hence it is non-fading. 



28 BULLETIN ELEVEN 

which is more than can be said of any other coloring compound used 
for any kind of a roof. 

Cement Tiles — ^Within the last few years many patents have been 
taken out for cement roofing tile. Plants have been started here and 
there over the country from time to time, the greater majority of which 
have been failures. Several plants have started in Ohio, namely at Co- 
lumbus, Lancaster and other points. Detroit, Michigan, also at one 
tijiie had a cement tile plant. The trouble has been to produce a tile 
which is not too porous, and which would not crack from expansion and 
contraction on the roof. To overcome this, they have necessarily been 
made very heavy. A second strong objection has been the inability to 
get permanent colors. Although minerals and mineral oxides arc used 
as colors, in the course of a single year they have been known to fade, 
presenting anythijic: but an attractive appearance. Numerous roofs in 
Detroit covered with colored cement tiles are examples of this. 

Asbestos Tiles. — A material lately come upon the market is a ce- 
ment asbest'^s shingle or tile. This material is proving far better than 
the regular cement tile, on account of its extreme lightness and a certain 
amount of elasticity. The same objection can be made against this tile 
as against the regular cement tile, viz., it will prove very unsatisfactory 
when the question of color is considered. Furthermore, they have been 
known to w^arp badly, w^hen exposed to the sun. To overcome this trouble 
a copper clamp or fastener has been devised and is being used on the 
later roofs of this material. 

There undoubtedly w411 be a field for this material on large roofs of 
cheap construction, where extreme lightness is necessary, but for strictly 
first class and artistic work where something other than a flat or corru- 
gated shingle is wanted, clay roofing tile will not likely be displaced. 

Scanty Distribution of Roofing: Tile Plants,— This question is perhaps 
the most important in connection with the promotion of the business. 
With at present only about one plant to three and one-half states, it is 
not remarkable that tiles are not more widely used. In many sections 
of the country a tile roof has never been seen. At the present time, 
not a single plant exists in our entire eastern coast region. In the entire 
South, only one plant can be mentioned, while the Southwest and West 
has not one single plant producing roofing tile as its sole output. In 
three or four plants in California, some few tiles are made in connection 
with other ware, but tiles form a minor part of the total output. When 
there are tile plants scattered through all the sections of our country, 
then we will begin to see the use of tile as a standard commodity, as 
bricks are used to-da}'. Nearly every town has its common brick j'ard, 
and nearly every state has one or more face or front brick plants, pro- 
ducing a high grade article, whose value will justify a freight rate to 
the large cities. 



GEOLOGICAL SURVEY OF OHIO. 29 

Thus should it be with roofing tiles. There is no present or future 
chance of shipping cheap tiles for covering barns and sheds. These 
should be made locally and carried in stock by dealers after the manner 
of the European countries. But the better class of tiles, such as Spanish, 
glazed and slipped, should be made by larger plants where proper 
material can be had, and shipped reasonable distances to their markets, 
as face brick and terra cotta are. 

These conditions actually exist now, in respect to the character of 
plants that are now doing business. There are in practically every case 
well constructed and carefully operated factories, which reach their 
markets by long distance shipments almost exclusively. But in the 
furture, with three or four such plants in each of the well settled states 
to care for the finer trade, and wth cheap tiles made in local yards for 
the cheaper trade, the industry will begin to compare with the develop- 
ment which it has reached in most other part» of the world. 

From time to time statements are made in the clay trade journals 
by various writers, that the present day brick manufacturers should 
take up the manufacture of roofing tiles in connection with their present 
business. Such advice is extremely ill considered. The manufacture 
of roofing tiles is a business by itself and should receive the undivided 
attention of those in charge. The methods, of drying, setting and burn- 
ing are widely different from those of brick manufacture and attempts 
in the past to burn brick and tiles in the same kiln have proven in a 
large measure a failure. In addition, the practice is not economical. 
The tiles can be burned in a much shorter time than the brick, hence it 
is a waste of time and fuel to hold the tiles under fire, waiting for the 
brick to receive the necessary heat treatment. 

There is no more reason for associating the manufacture of roofing 
tile with that of brick and drain tile, than for associating the manufac- 
ture of terra cotta with the same articles, or the manufacture of crude 
stoneware with fine porcelain. 



30 ; BULLETIN ELEVEN 



CHAPTER n. 

THE VARIETIES AND QUALITIES OF RCX)FING TILES- 

In making a critical analysis of the relative value of roofing tiles 
in comparison with other roofing materials, we see that in this country 
at least, the quality which enables this material to survive the attacks 
of competition and grow in spite of its greater cost, is its beauty, 
or the artistic quality which enables the architect to make the roof of 
a structure an ornament instead of a necessary disfigurement. The 
beauty of a roofing tile depends on two factors, viz., its shape or design 
and its color. Of the two, the design is more important, for with an 
uninteresting color (if not actually disagreeable) an attractive roof may 
be made if the design of the tile is cleverly handled, while with a poor 
design, even a tile of good color does not make an interesting roof. 

But the possession of an artistic design alone is insuflficient to 
justify the use of a tile roof. The properties of the material itself, its 
ability to resist weather, and its ability to resist the blows and accidental 
stresses of shipment, storage, application, and use, in short its strength, 
and also its weight in comparison with other roofs, all these must be 
considered. The qualities of a tile are therefore properly grouped 
along two lines, viz : 

Artistic — design and color. 

Practical or Utilitarian — durability, strength and weight. 

GENERAL DISCUSSION OF VARIETIES. 

The old adage, ''There is no new thing under the sun,'' is as well 
exemplified in the design of roofing tile as elsewhere, for any critical 
examination of the tiles of the present day compared with those of 
ancient times shows at once that we are now merely ringing the changes 
on the same old fundamental shapes which man's brain evolved early 
in the world's history. We have, it is true, greatly modified and im- 
proved them in details, but we have not and cannot get away from the 
original type forms. 

All roofing tiles may be divided into three great groups, viz : 

1. — Shingles or Flat Tiles. 

2. — Spanish or Normal Tiles. 

3. — Interlocking Tiles. 

Shinsfles or Flat Tiles — This pattern is the simplest of all; it 
is nothing more than a generally rectangular slab or plate of burnt clay, 



GEOLOGICAL SURVEY OF OHIO. 31 

about six inches wide and fifteen inches long, with holes punched at one 
end for securing it to the roof. In the eastern hemisphere, a lug or 
projection of clay is formed on the under side of the tile at the upper 
end, whereby it is hung on the roof purlin which supports it. Tile of 
this pattern make a very plain-looking roof. From a distance, the out- 
lines of the individual tiles are lost, and the entire roof surface appears 
as though covered with a single coating of some red material. Upon 
drawing nearer to the building, the butt ends of the tiles form faint 
horizontal lines across the roof, but outside of these lines, very little 
else appears to break the monotony of the surface. To overcome this 
monotony, shingle tiles have been designed with quite strong vertical 
ridges and valleys, or the sides or edges of the tiles are made in a semi- 
circle, so that when two tiles are placed side by side, a strong shadow 
line is thrown by the projection. Other patterns are also made, which 
have an increased thickness at the lower end over that of the upper, 
and in addition strong vertical ribs, are added, thus making a much more 
impressive appearance. There are also numerous patterns of shingle 
tiles at the present time which have been made inter] ocking. -\11 of 
these modifications tend either to break the monotony of the otherwise 
plain tiles, or to reduce the weight or number per square, or otherwise 
improve the roof. 

The simple flat shingle when properly made, that is, straiglit and 
true, and when laid with the proper lap, makes a perfectly water-tight 
roof. IMakers of other patterns often seek to discredit the shingle tile, 
by claiming that it is not water proof. It is true that a number of in- 
stances can be cited in this country in recent years where shingle-tiled 
roofs have failed to make a good water-proof covering. Upon a careful 
investigation of one of these unsatisfactory roofs, it was found that the 
tiles were very poorly made, being not only defective through side checks 
or cracks, i. e., checks extending in from the edges of the tile from one 
to three and one-half .inches, but they were also very crooked, many of 
them being so warped that they were one-half inch or more out of true. 

In addition, they were very rough from careless handling while soft. 
Using tiles with the above defects, it would only be natural to expect 

the resultant roof to leak. The tiles described above were made about 
eighteen years ago, when the methods of manufacture were not well de- 
veloped, and this particular roof happened to be the first contract taken 
by a company which was just beginning operations. Nevertheless 
it would have been possible to have sorted the tiles more closely, discard- 
ing the cracked and crooked ones, and thus have saved the roof from giv- 
ing constant trouble for eighteen years, and its final replacement with 
other tiles. Shingle tiles as made today are greatly improved, and if 
properly laid should furnish a perfect roof. 

The one great objection to the shingle tile design is its great weight, 



32 BULLETIN ELEVEN 

which largely exceeds that of the other styles. While they are in the 
same class with a slate roof in weight, they weigh from 200 to 400 pounds 
per square (100 square feet) more than Spanish or interlocking tiles. 
They are also unpopular with roofers, from the fact that it takes so 
many tiles to cover a square (with ordinary sizes, ahout four hundred). 
To properly fasten these, the roofer must drive 800 nails, while with 
Spanish tiles about 160 cover a square, making only 320 or less nails to 
drive. It can thus readily be seen that it wiU require nearly twice as 
much time to lay a square of shingle tiles as it does for a similar area of 
Spanish tiles. 

Architecturally, shingle tiles should be used on small structures 
only, owing to their being made in small units. Their size prohibits 
their use on large massive buildings, at least from an artistic point 
of view. For residences, park buildings, siding purposes, etc., where the 
roofs are not too elevated, shingle tiles make a very satisfactory covering. 

The Old Spanish or Normal Tiles — This design has, without ques- 
tion, been used in n\ore parts of the world than any other. While 
there are many modifications of the normal tile, from the simple half- 
round trough to the modern S tiles made on an auger machine, or the 
improved interlocking Spanish, they have no doubt all sprung from the 
ancient pattern such as we find used on the Temple of Hera in Greece 
about 1,000 years B. C. 

To describe all of the many forms and modifications of the normal 
tile would be impossible and useless as well. The following notes will 
be restricted to the more important forms in use at the present time. 

The real or typical normal tile is a trough shaped piece of clay ware 
of a more or less flattened semi-circular cross-section, enough smaller 
at one end so that the exterior of the small end will fit into the interior . 
of the large end and thus provide for the necessary lap. The troughs are 
thus seen to be half sections of the frustrum of a cone of slight taper. 
The length varies from twelve to eighteen inches. 

For the execution of certain styles of architecture, these half 
round pieces are placed on the roof so that one-half of the pieces act 
as covers for the other. That is,, two rows of the half-rounds are carried 
up the roof inverted, or with the troughs up, and just far enough apart 
so that a single row, trough down, will interlock with the two inverted 
rows, thus forming a cover for their edges and the space between. 

Another mode of using the typical normal shape is in connection 
with pan tiles, that is, flat tiles like shingles, but with the two edges turned 
up to form marginal ridges. When the half-round tile is laid in combina- 
tion .with the pan tile, the combination is known as the Roman design. 
While the original Spanish or normal tiles and the Roman designs are 
both manufactured at the present time, their use is ordinarily restricted 
in the United States to an occasional structure, where it is desired to 



GEOLOGICAL SURVEY OF OHIO. 33 

copy some ancient styles of architecture. For instance, there are many 
buildings in California and the southwestern United States, which are 
planned on the so called ** Mission'' type of architecture, which was 
the architecture introduced in that region by the Spanish padres who 
came up from Mexico, or from Spain direct, to establish their religion 
among the savage races who were then the sole occupants of that land. 
For these modern *' Mission'' buildings, modern tiles in the old Spanish 
designs are wanted, and in some instances, Mexican workmen are im- 
ported to make by hand and apply the crude Spanish tiles in the way that 
has been done for three hundred years in their own land, and thus give 
the roofs the characteristic texture and aged look which cannot be ob- 
tained with a machine-made product. For such purposes, the pure Spanish 
design is of course valuable, but when the questions of manufacture and 
use are considered, the old Spanish or normal tiles are not desirable, 
owing to the large number of pieces required to cover a square, and 
with the Roman style, it becomes necessary to maintain two sets of dies 
and pallets in order to provide the two forms required. 

For severe northern climates, where rough winds are encountered, 
this kind of tile must be laid in an elastic roofing-cement to get a water- 
proof roof. As the tiles have no. head and heel locks, and only overlap 
three inches, it becomes necessary to stop up this lap joint to prevent 
the wind from blowing the water up the joint between the two tiles and 
over the upper end of the lower tile, thus causing a leak. 

The elastic cement mentioned is a compound consisting of some or- 
ganic oil, with some mineral of red color, such as iron oxide or ore. 
This mixture is worked up to the consistency of soft putty and is applied 
in a thin layer, by a small trowel, to the upper end of the' lower tile; 
then the overlapping end of the upper tile is bedded into it. Thus the 
two tiles are stuck or bound together, although there remains sufficient 
elasticity to permit of expansion and contraction of the roof. For this 
reason, a cement which sets or hardens, like plaster of Paris or Portland 
cement, cannot be used. The drying out or hardening of the elastic ce- 
ment mentioned above is sure to occur in time, and when it occurs, it will 
crack under the strains brought about by changes of temperature and 
wind motions, and leaks begin to develop. Just what the life of these 
elastic cements is, has not l)een ascertained. One roof which had been on 
twelve years was examined by the writer and the cement was still plastic,* 
and could be worked up into a paste between the thumb and finger. How- 
ever, any design of roofing tile which depends on an elastic cement to 
make it a perfect roofing material is in default, because the life of the roof 
is that of the cement used, and relaying a roof is always an expensive and 
unsatisfactory task. Some tiles will always be broken in taking; up and 
their color could not be matched in any new tiles, and the result would be 

3— G. B. 11. 



34 BULLETIN ELEVEN 

a patched appearance. This and the cost, which would be in excess of 
the original laying, on account of the cleaning of the old cement oflf before 
relaying could be done, makes it impractical to consider a method as 
commercially sound which calls for the use of an elastic cement. 

Modern Spanish or S Tiles* — The difficulty of manufacture of a 
conical trough-shaped tile has made the use of the pure Spanish tiles an 
unusual thing, except in Mission architecture, as noted, but the beauty of 
the effects secured by their use is so great that there have been many ef- 
forts made to get a design which would avoid the tapering form, and still 
retain the same general effect. This has resulted in the development of 
the S tiles. 

The S tile, as at present made, is in cross section the shape of a flat- 
tened letter S, laid with its vertical axis horizontal. In the true S tiles, 
each one consists of a parallel ridge and trough, but a modification is als9 
in use, in which the trough is flat with an edge upturned vertically, while 
the ridge is curved in a half round as before. This shape is virtually a pan 
tile and Spanish tile in one piece, and does away with a part of the objec- 
tion to the real pan tile. Both of these two styles fall under the general 
head of S tiles. In order to allow for the lap of the tiles, they are so made 
that the faces and backs of the tiles are of the same radial length. Thus 
they can be nested, one above the other, indefinitely. 

These tiles, either the pure S tiles or the S pan tiles, have the same 
fault as the ones last described, viz, for ordinary roofs, it is necessary to 
use an elastic cement at the upper end of each piece at the point of over- 
lap. 

It has been the practice in many instances of late to lay roofs of these 
tiles dry, i: e., without cement. For roofs of any ordinary pitch, this 
practice is to be condemned, for in this case the roof must depend on the 
felt or building-paper, which is laid on the sheeting and under the tiles, to 
prevent wind suction. Also the tiles are nailed to the roof, and the felt 
paper is necessarily badly punctured, and is therefore not at all water- 
proof. Although no elastic cement will last indefinitely, it will at least 
for many years, and add very greatly to the value of the roof. 

Although the auger machine S tile, or modern Spanish, has this one 
objectionable feature, it is nevertheless destined to be the form of Spanish 
the most largely used in the future, on account of its cost of production 
being lower than that of the press-made or interlocking Spanish tile, as it 
is run out in continuous bar form, and cut off in lengths. It can be sold 
cheaper than a pressed tile and will therefore be more widely used. From 
the architectural view point, the S tile is very good. Its strong vertical 
lines from eaves to ridge of a roof are suitable for buildings of magnitude 
and strong outline. 

The Spanish design, either pure or in the modified forms, is the pat- 
tern that will be the most widely used in future work on the better 



GEOLOGICAL SURVEY OF OHIO. 35 

class of buildingS; like churches^ schools; libraries and institutions of all 
sorts, and possibly on large residences, but a sense of harmony prohibits 
the use of full-sized Spanish tiles on buildings of moderate size. Their 
extremely bold outlines and high relief makes an appearance of too 
much weight at the top of the building. This mistake is very com- 
monly made at the present time by architects all over the country. It is 
largely due, no doubt, to the fact that the manufacturers are making but 
one size of Spanish or S tiles. However, when the time comes that our 
American architects more fully realize the artistic beauty of the tile roof, 
and perceive that this can only be developed by using tiles of proper pro- 
portion for the buildings on which they are to be used, there will be tile 
manufacturers ready to produce the desired varieties of sizes. 

Interlocking: Spanish Tiks* — Although it has been seen that the de- 
velopment of the S tiles has solved the problem of cheap and rapid manu- 
facture, while still retaining much of the distinction, style and character- 
istic "texture*' of the real or old Spanish tiles, it has failed to overcome 
this most serious defect,viz., the necessity for cemented joints to make the 
roof reliable in windy rain ^nd snow storms. A further step has been 
taken in the interlocking Spanish design, to correct this deficiency. It 
may be objected that the use of the interlocking idea puts the tile out of 
the Spanish class altogether, but it does not seem so to the writer, for the 
name "interlocking tiles'' has a distinct meaning in the trade and no tile 
maker or dealer would confuse an interlocking tile with an interlocking 
Spanish tile, if the terms were used in that way.. In any case, the inter- 
locking Spanish tile is clearly distinct from the rest of the interlocking 
tiles and these latter will be discussed under a separate heading. This 
interlocking Spanish tile differs from the S tiles made on an auger machine 
very little in outline or appearance, but it is made with side and end 
locks, or tongues and grooves on the upper surface of the tiles, which in- 
termesh with corresponding grooves and tongues on the lower surface of 
the contiguous tiles. By this device is produced a perfect tile, that is, 
one that will not need a cement to make it water-proof. With locks of 
proper height, and tiles that are properly made, it is possible to lay a roof 
of this design that will withstand any storm except such a one as would 
be in danger of lifting the roof itself. 

The cost of producing this tile is naturally above that of the straight 
auger-machine S tile, since the locks can only be put on by pressure in a 
tight die, but the superiority which it undoubtedly affords should insure 
its use on the better class of buildings. 

From an artistic point of view, the press-made Spanish tiles are much 
better than the flow-die pattern, inasmuch as it is possible to give the butt 
or lower edge of the tile a rounded or curved shape which agrees with the 
other curved lines of the tile and make the whole consistent, while in the 
auger-machine S tiles, the ends are wire-cut and stand out in a sharp, 
harsh line in marked contrast to the flowing curves of the roll of the tile. 



36 BULLETIN ELEVEN 

Interlocking: Tiles* — As explained in the preceding section, this 
tile, unqualified by any other word, is understood in the trade to mean a 
pressed tile of a shape different from Spanish or S tiles, and as the name 
implies, all tiles of this group are made so that their edges interlock one 
with another. Just when the first interlocking tiles w^ere made is not 
known to the writer, but it was unquestionably much more recently than 
either of the other two types. It is probable that they were first made in 
France or Germany, for it is in those countries that we find their greatest 
development. 

The interlocking tile is rectangular in outline, and of various sizes, 
though at present the manufacturers have settled down very generally to 
the dimensions of nine inches wide by sixteen inches long. The outer 
surface of the tile is usually more or less broken by strong vertical lines or 
corrugations. On the edges are the tongues and grooves which form the 
locks. The right hand side of the tile is made to form the cover or upper 
half of the lock, while the left-hand edge carries the under half. The 
tongues and grooves which form the locks are made single or double or 
even treble. 

The upper and lower ends of the tile are also provided with similar 
locks, so that all four sides of the tile engage w'ith the edges of four other 
tiles. In cross section, the interlocking tiles are usually complex — that 
is, they are neither planes like the shingle tiles, nor simple curves like the 
old Spanish tiles, nor double or reversed curves like the S tiles. They are 
usually planes broken at one or more points by a curved roll or rounded 
elevation, the axis of which is parallel with the longer axis of the tile. 
Sometimes there are two such rolls, with a plane area between. Some- 
times the elevation is not a curve, but is V shaped in croSvS-section. 

The presence of this roll, whatev^er its form may be, strengthens 
and stiffens the tile materially in lines at right angles to its axis. In 
turn, the roll itself requires stiffening with smaller internal ribs or par- 
titions, which hold the tile against warpage on the other axis. Thus 
supported by the vertical and horizontal cross ribs, this tile is a much 
stronger, more solid structure than any of the preceding, and consequently 
it is possible to make interlocking tiles in much larger sizes. Their 
large size or roof-covering capacity, and their lightness, due to the 
narrowness of their overlaps, which is about two inches on all sides, 
makes them much in favor with every one dealing with the subject. 
The manufacturer likes to make them on account of their rigidity and 
the consequent small loss in manufacture. Also, on account of their 
size, few are required for a square — about lo5 — and as he sells by the 
square, he can quote a low price. The roofer likes them on account 
of the rapidity with which he can cover a roof. The architect likes them 
because of their low weight — about 800 to SoO pounds per square — and be- 
cause of their mechanical j^rfection and the permanence of the roof. The 
consumer likes them both on account of their appearance and their price. 



GEOLOGICAL SURVEY OF OHIO. 37 

80 all in all, from a commercial standpoint, the interlocking tiles are the 
ones most in favor. 

But, considering them from the standpoint of architectural beauty, 
they are seriously criticised in some quarters, and for this reason their use 
has largely been restricted to plain structures, like train sheds, power 
houses, factory buildings and others of like nature — buildings of large 
roof area, without much pretence to architectural beauty. They are used 
on buildings of the above classes, largely on considerations of cost, and for 
this reason the interlocking tiles are destined to be the most important 
commercial tiles of the world. The other tiles will always have their 
uses, but the interlocking tiles will surely l^e the standard commodity. 

THE DESIGNING OR PROPORTIONING OF ROOFING TILE. 

What has been said thus far has dealt with the design of the 
tile as a whole, and largely with its acceptability from the standpoint of 
appearance — the artistic side. We must now take up the more 
intimate phases of design, viz., the proportioning of the parts of 
the tile so that it will be able to resist the strains to which it will 
be subjected. It is one thing to select a superfijial form which is 
artistic and which would produce a beautiful effect on a roof, and 
quite another to make the tiles economically and with low losses in 
manufacture and use. The latter problem demands correct settle- 
ment of the proportions of the tiles — length, breadth, thickness, over- 
lap, mode of locking, and system of strengthening ribs to guard against 
warping or breaking. In treating this side of the subject, it will be 
well to again consider each of the three principal varieties separately. 

Shingle Tiles — The ordinary size is six by thirteen by three- 
eighths inches. The thickness is often allowed to reac'h one-half inch, 
chiefly through neglecting to watch the wearing of the die and fail- 
ing to replace it with a new one or to repair it with new lining. The 
weight of shingle tiles three-eighths of an inch thick is about 1 ,100 pounds 
per square, where one-half inch tiles will run 1,200 pounds or more. 
Thus the thickness should be very carefully watched. 

The edges or sides of the tile are made either square or rounded. 

■ 

The latter form is to be preferred on both practical and artistic grounds. 
It is extremely difficult to continuously produce square or sharp cor- 
ners in a column of clay flowing through a die. The corners tend to 
crack or pull up, or xag or feather-edge, due to the greater friction or 
resistance of the corners to the passage of the clay. With a rounded 
edge, the tile-bar will flow much easier through the die, and with far 
less probability of checking on sides or corners. 

When the round-edged tile is placed on the roof, vertical lines 
are accentuated much more than with square-edged, close-fitting tiles, 
and this is a great help to an otherwise plain roof. 



38 BULLETIN ELEVEN 

Again, the rounded corners form air spaces or channels at the 
under edge of the tile, thus providing open channels for the ventila- 
tion of the roof, keeping the sheathing boards dry, and delaying decay. 

Interlocking Shingle TfIes.^These 
tiles are usually made nine inches 

wide, by thirteen inches long, by one- 

half inch thick, and require about 
190 to the square. Their weight 
per square runs from eight hundred 
to nine hundred pounds. At the 
upper end of the tile on the face or 
obverse side, two small ribs, about 
one-quart«r of an inch high, are so 
placed that one is at the extreme 
edge and the other about one and 
one-half to two inches lower down 
on the tile. On the under or reverse 
side, at the lower end of the tile, 
are two counterpart ribs, one form- 
ing the end of the tile. These ribs 

act as wind and water-breaks at the pig s-Round-edged Shingle Tilea. 
ends of the tile. 

Along the left-hand side of the tile is a single gutter, into which 
meshes a corresponding rib projecting downward from the right-hand 
margin of each tile, thus forming the lateral or side lock. 



Fig. 10— Interlocking Shingle Tiles. 

The greatest trouble in making this kind of tiles is to get the locks 
deep enough. If they are made as deep as they should be, then the 
butt end of the tile is too high, accentuating the horizontal lines on 
the roof and making them appear out of proportion or harmony. 

S Tiles. — ^The S tile made on an auger machine is usually eleven 
inches wide by thirteen inches long, with an extreme height of roll of three 
inches, and average eight hundred to nine hundred pounds per square. 
The thickest part of the roil is one-half inch and the thin part about 
five-sixteenths of an inch. These different thicknesses are due to 
curves of the same radii being used on both sides of the tile in order 



GEOLOGICAL SUEVBY OP OHIO. 39 

that the overlap may fit perfeotly. It is usually better to have off- 
sets in the die, which produce parallel grooves through the thick por- 
tions of the tile, thua not only making them a little lighter in weight, 
but assisting in the drying and burning as well. Tiles having these 
open grooves should not be laid dry; an clastic cement should bo used 
to prevent water and snow from blowing up over the end of the tile, 
under influence of wind in the proper dii-ection, The side of the tile 
which is covered by the roll should be made just as high as the roll 
will allow, thereby forming a good deep gutter. 



Fig. 11 — "S" or Spanish Tiles, made on an Auger Machine. 

Interlocking; Spanisli Ttles. — In general outline and appearance. 
these tiles are not very different from the S tiles produced on the auger 
machine. The real difference is in the side and end locks, but these 
do not show when the tiles are in position on the roof. In size they 
usually run about nine by twelve inches, or a little larger, and weigh 
about eight hundred and fifty pounds per square. In some pat- 
terns the lock consists of two raised ribs, running lengthwise, along the 
side of the gutter, and then crosswise of the upper end of the tile. 
These ribs are usually three-quarters of an inch high and the same 
distance apart. 

Underneath the roll are two projecting tongues, which interlock 
with the side ribs on the edge of the gutter. The end of the tile may be 
made either square or rounded. The latter shape is the more pleasing 
and lends its form more to the shape of the rest of the tile- 
To make this tile perfect, it should have a strong double lock along 
the side and over the top. The ribs should be fully three-quarters of an 
inch high, or even more, and the tongue which fits between the ribs 
should not quite touch the bottom of the groove, allowing room for the 
water to flow, thus preventing the accumulation of dirt. It is also well 



40 



BULLETIN ELEVEN 



Fij. 12 

Interlocking Spanish 
Tile. 



press. 



not to have too close a fit, in order lo avoid a tendency for this space 

to fill and remaindampby capillary attraction; also, there should be some 

play in the locks to allow for slight differences in size of the bui'ned tiles. 
Interlocking: Tiles. — In this group we find 
the best representatives of the interlocking prin- 
ciple. A few forms will be shown to illustrate 
not only good forms of locks for interlocking 
tiles, but for any other kind of tiles using the 
interlocking principle. 

In the first place, the tile should be so de- 
signed that all high parts on the face or obverse 
side are in the same plane, so that a single flat 
pallet can be used to place it on when it is 
taken, soft and easily doformable, from the 
A tile in position on its pallet is shown in Figure 14. 
On the back or reverse side of the tile, small cross-ribs should be 

provided, not only to stiffen it, but to make its nesting or packing more 

secure and solid. 

It will be seen that the 

Fi-ench A pattern. Figure 15, 

has two rather deep valleys or 

gutters; these carry away the 

greatest part of the water. 

Upon long roofs of low pitch, 

they are often taxed to their 

utmost capacity. The tiles 

should also be so designed 

that they break joints, i. e., 

the locks in the various 

courses on the roof should be 

made to alternate. Thus, 

the water that gets into the 

lock of one tile is not transmitted to the lock of the tile next below, 

but is turned into the broad gutter on its surface. 




Fig. 14 — Showing proper design for an Interlocking Tile to lie Flat on a pallet. 

These tiles are usually made nine by sixteen inches, requiring one 
hundred and thirty-five per square. Each square weighs approximately 
seven hundred and fifty to eight hundred pounds. 



GEOLOGICAL SURVEY OF OHIO. 41 

On the general subject of modes of interlockini; available for use in 
tiles, there is considerable of interest. Referring to page 42, a series of 
sketches show the gradual development of the interlocking idea. 



Pig. 15— Interlocking Tiles. French A Pattern. 

Side Locks. — Figure A shows the simplest form of lock, being 
merely a single tongue and groove. This lock is not very serviceable. 
In the first place, it is too shallow, and secondly, the water can enter the 
open joint at the point marked (a), carrying dust and dirt with it, which 
soon fills the shallow place under the tonjtue. The water, being thus 
blocked, soon fills up the gutter and leaks over onto the roof boards. 
Tiles provided with this form of a lock should only be used on buildings 
of little importance, like sheds. 

Figure S is a lock of a little better design, inasmuch as the shoulder at 
the point marked (b) will have a 
tendency to break up currents of 
air and prevent them from carry- 
ing water into the lock so freely. 
Also, the dirt will be more likely 
to lodge on the shoulder (b) and 
not fill up the gutter. 

Figure C. This lock is a very 
much better one than either A or 
B, because the open joint is on the 
side, and cove.'ed by the over-lap 
(c),thus preventing the rain from 
entering the lock-joint directlj'. 
The most se.'ious objection to this 
lock is the likelihood of its leak- 
ing by cross-currents of air blow- 
ing into the open jointat the point 

marked (c) and carrying the water F"K- \^ -Showing Section of a Roof Laid 
*■ ' .' e ^;ih TT,t<.fin.-irin<. TjIbc ir^ Which the 



42 



BULLETIN ELEVEN 



Figure D, This lock is again a very decided improvement over 
any of the preceding; while it resembles B, it is better, because of the 
protecting lug at the point marked (d) which prevents cross currents 
of wind and rain from entering the joint from the side, as in Figure C. 
Also, an improvement over B lies in the fact that an air space is left 
under the tongue at the point marked (d). This allows the dirt that 
might enter to be washed away, and also prevents the possibility of 
capillary attraction, which is apt to cause leaks in Figures A, B or C. 
The raised portion (d) also makes the depth of the main gutter of the 






Fig. 17 — -Showing Various Forms of Side and End Locks. 

tile deeper, which is a good feature. This lock is very largely used 
in this country on the principal brands of interlocking tiles. 

Figure E. In E, we have a lock in some respects like C, except 
that it is double. These double locks make it almost impossible for 



GEOLOGICAL SURVEY OF OHIO. 43 

wind to blow fine snow or rain through the various turns that would 
have to be made. This is an exceptionally good lock, there being only 
one slight drawback, viz., the main gutter of the tile is not quite so deep 
as in D or F. 

Figure F shows a double lock patterned after D, which should 
prove very effective. The high part at (f) makes the main gutter very 
deep; with the two lock gutters there should be no trouble from leakage. 
While locks E and F require the use of more clay than lock D, they 
should prove very much more satisfactory. Any snow or rain getting 
beyond the first lock will surely be caught by the second, thus pre- 
venting a leaking roof. 

There are, of course, still other locks in use, but they are all more or 
less modifications of the ones shown, and bring in no new principles or 
added efficiency or economy in manufacture. 

Figure G shows the typical lock used on ordinary auger-machine 
Spanish or S tiles. While this lock is simple, it is very effective. The 
main gutter is very deep, and the air space (g) tends to break up any 
capillary flow. However, if the tiles are not straight, and the two 
contact points are open, fine snow will very frequently blow over the 
tongue, and, melting afterwards, cause leaks. 

Figure // is a fair representative of the lock used most commonly 
on interlocking Spanish tiles. It will be seen that the lock is a double 
one, and, as said before, if the ribs are high enough, it will make a very 
Satisfactory lock. 

Figures I and J are two other forms of locks used on Spanish tiles, 
neither of which has any particular advantage over H, and, in fact, are 
more likely to leak under the influence of winds blowing diagonally 
across the roof. 

Headier Top and Bottom Locks* — Figure K represents the most 
simple form of a head-lock which can be used, viz., the end of one 
tile turning up and the next one down. This lock is a very poor 
and ineffective one. Many tiles have been made with this simple lock, 
but the day when they can be freely disposed of has passed. The locsj 
does not prevent wind from cariying fine snow and rain over it. 

Figure L is a very much better lock and is the type largely used for 
the head-lock of Spanish tiles. Any snow that may pass the first tongue 
and groove will be caught by the second one and returned to the outside 
face of the tile as water. 

Figure M represents the typical head-lock for interlocking tiles 
other than Spanish. It is the one mostly used in the United States, 
and as a rule proves very effective. It can, how^ever, be improved for 
open construction work by using the head-lock as shown at N. 

Figure A^ This is a triple head-lock and should remain dry through- 
out any storm. 



44 BULLETIN ELEVEN 

The most vulnerable part of a tile is the joint, both on the side and 
end. Many of the first tiles used in this country failed to make dry 
roofs by not having the looks either large and deep enough, or in suffi- 
cient number. More attention is being paid by tile manufacturers to 
the perfection of the locks each year, and such should be the case, for 
the future of the industry absolutely depends on its being able to furnish 
strictly water-proof roofs for important structures. It is quite probable 
that there will always remain a field for the use of tiles of such a grade 
that they will remain tight under all ordinary storms and might leak 
a little under severe and exceptional stress, for there are many buildings 
in which a slight and well diffused leakage, separated by wide time 
periods, would do no real harm. If tiles for such purposes can be made at 
decidedly lower figures, they \\\\\ unquestionably find use, but such tiles 
ought to be sold on this understanding. The trouble in the past has 
been that the tiles of this grade have been sold under a short-sighted 
business policy as being fit for a roof of first grade, while, as a fact, they 
belong to and hre fit for only a roof of second grade. 

There are also many roofs which may leak more than a little with 
every win<ly rain, but which are still good enough for their purpose, 
and the cheapest grades of tiles without any locks, or only the least 
efficient, will surely find use for such purposes. 

What is needed in the roofing tile business at present is some 
clavssification of tfie product according to its purpose;. It is manifestly 
unfair that the leaknge of a cheap tile on a roof of small importance 
siiould be c(.nsidered as nn indictment against lilc roofs in general. If 
a tile 11111 nufa^'tuior guarantee*: a roof i\s water-proof under any or all 
natural oonditions, and it fails, then his blame and responsibility are 
unquestioned. But if he sells a roof for what it is, then the architect 
and consumer have no just cause for complaint. 

THE RELATION BETWEEN THE DESIGN AND THE PHYSICAL 

PROPERTIES OF A ROOnNG TILE. 

It has been shown that the selection of a design for a roofing tile 
involves a consideration, not only of the artistic results attainable by 
the use of the tiles in masses, and of the ability of the tiles to collectively 
make a dry roof, but also of the proportioning of its parts to develop the 
required physical strength for handling, piling in driers and kilns, storage, 
and fastening to a roof. The question of color is one that is largely 
separated from considerations of design, l)eing usually a fixed factor 
with any single clay, though sometimes regulated by mixture of clays 
or addition of coloring compounds to them or covering their surface 
with colored coatings. 

The question of the strength of the resultant tile, then, must' always 
be kept before one in designing a tile — any neglect of this point will result 



GEOLOGICAL SURVEY OF OHIO. 45 

in heavy losses in manufacture and generally by breakage or leakage 
after application on the roof, owing to inability to stand the shocks and 
strains incident to ordinary use . This question of the proportions or sizes 
necessary to give the requisite strength is one which cannot be settled 
by any arbitrary rules or principles. If clays were a fixed and definite 
material, or even nearly so, as steel or glass, it would be possible by 
experiment and calculation to reach a standard ratio of thickness to 
area, and a minimum of reinforcement or filleting at corners or points 
of abrupt change in direction of the body of the tile. But since clays 
in general are anything but fixed or definite, and since even the same 
clay develops very great variations of strength at different stages in its 
burning process, and is moreover often subject to fluctuation in quality 
in the same bed, it is evident that the selection of a design for a tile can 
only be a tentative matter, and that the tile ultimately developed is 
very apt to differ more or less widely from the design selected in the 
beginning. The tile-maker is likely to find that his clay will not flow 
in a stream of the desired cross section, Ox* that it will not release well 
from a die of the desired complexity of shape, or that it must be made 
heavier to endure drying or burning without warping, or that new ribs 
and reinforcements, not needed or desired, so far as water-proofness is 
concerned, are required to keep the ware straight and strong. Therefore, 
a tile design in successful use in a factory almost invariably represents a 
process of adaption or adjustment between the ideals of design on the 
one hand and the capacities of the material on the other. 

It is not the intention to discuss at this point, the intimate physical 
properties of the roofing tile bodies as to strength per square inch, etc., 
but rather to consider broadly the som-ces of the strength of the product, 
and the relative desirability of the different internal structures which 
clay bodies of different sorts are known to develop, especially under 
the influence of different heat treatments. 

The strength of a burnt clay ware is dependent on: 

1st. The plasticity or internal cohesion which the mass exhib- 
ited in the unburnt condition. 
2nd. The assortment of the sizes of the mineral grains com- 
posing the mass. 
3rd. The extent of the alteration of volume of the mass in 

drying and vitrification. 
4th. The degree of combination, or vitrification of the mineral 

grains in the burning process. 
5th. The cooling of the product from the nearly-fused con- 
dition to the atmospheric temperature without inducing 
cracks or cooling strains. 
Taking them up for consideration in order: — 
1st. It is a point well known and recognized by clay workers that 
those clays which show a high degree of internal cohesion or sticking 



46 BULLETIN ELEVEN 

quality, with which is always associated good or high plasticity, are 
apt, other things being equal, to make a strong, tough product when 
bux'nt. There are doubtless exceptions to this rule, but the use of the 
adjective "strong" by so many clay workers is a tacit recognition by 
them of this point. Strong or fat clays, i. e., tough, adhesive, cohesive, 
plastic clays, make strong products, compared to the products made 
from '*weak" or lean clays, whose properties are the reverse of those 
above listed. 

The bearing of this in roofing tile manufacture is that clays of the 
lean or weak class are not suited to this purpose, and if used, as they 
sometimes are, will require extra fitness in other directions, or extra 
care in firing to make up for this deficiency. In general, roofing tile 
manufacturers are divided into two hostile camps, producing, respec- 
tively, soft, porous tiles and hard, impervious or vitrified tiles. The 
soft, porous tiles are almost always produced from glacial or alluvial 
clays which are ^'strong," and the strength of the tile in its unbui-nt 
state is comparatively little increased in the burning process. The 
hard, vitrified tiles, on the other hand, are frequently, if not usually, 
made from shales or indurated fossilized clays, which have lost the 
most of their plastic character during their long existence in rock form, 
and only developed a partial or feeble cohesion and plasticity in tem- 
pering. These clays are 'Sveak'' and make a tile which is physically 
weak and easily broken in handling in the raw condition. But this 
defect is overcome by their fitness to develop strength in burning. They 
vitrify well and their product is able to stand alll the physical tests to 
which it can fairly be put, with credit. 

2nd. The assortment of the sizes of the mineral grains of a clay 
is of importance in two directions — its effect on the strength of the raw 
clay and its effect on the ease of vitrification in burning. It has been 
shown that a mixture of coarse and fine particles, in graduated sizes 
from the finest slimes up to medium sized sands, is productive of tensile 
strength in an unburnt clay. A clay composed of all fine particles has 
been found by a number of observers to develop usually only moderate 
or low strength. The same facts are found to apply to cement con- 
cretes where a proper mixture of sizes is a matter of rigid r-equirement 
in the sands, gravel and bx'oken stones used in work of importance. 

In the glacial and alluvial clays, commonly used in making porous 
roofing tiles, this variety of sizes of mineral particles is usually found. 
The fine sizes especially are well represented, insuring the filling of the 
voids between the coarse particles. In shale and fossil clays, commonly 
used in making vitrified roofing tile, the ultimate mineral particles are 
usually very fine indeed, but in grinding and tempering, the paste which 
is formed is not composed of its ultimate mineral particles. Its grains 
are usually aggregates or lumps of grains, sticking together and acting 



GEOLOGICAL SURVEY OF OHIO. 47 

as single large grains, and there is usually a deficiency of fine material. 
Hence, the product is weak in its unburnt condition. 

After burning, however, these relationships are altered. The 
relatively coarse-grained glacial and alluvial claj^ with a large variety 
of sizes of grains in its component minerals, usually vitrifies slowly and 
the structure is apt to be porous and less compact when fired at moderate 
temperatures. But the shale grains, which acted in clots or groups in the 
plastic state, act more nearly at their true size value in vitrification, and a 
greater degree of consolidation and body-knitting takes place than in 
the other case. So that the assorted sizes of grains is found to most 
generally favor the production of porous tiles, while the use of clays of 
uniformly fine grain is apt to produce dense, vitrified tiles, all other 
things being equal. 

3rd. The effect of large volume-changes on the strength of the 
product is a factor of importance. It cannot be considered as operating 
separate from the considerations Nos. 2 and 4, but its influence can 
be clearly seen in connection with these factors. In general, excessive 
volume-changes lead to weak, structurally defective products This is 
true, whether the change in volume occurs in drying or in firing. This 
may seem paradoxical, because extensive volume-changes are necessary 
to develop a highly vitrified structure. But there is a golden mean here 
as elsewhere, and clays which undergo great shrinkage almost invariably 
develop at the same time internal flaws, or laminations. Or "dry spots," 
representing the inability of the mass as a whole to contract at the same 
rate in all directions on account of its shape, or the influence of pressure 
of other pieces of ware resting on it or similar causes. The result must 
mean flaws at right angles to the directions in which high tension 
develops. 

Thus, roofing tiles made from glacial and alluvial clays, which 
shrink at a moderate total rate, usually retain a sound interior structure, 
and are little weakened by interior flaws, while the tiles made from shales, 
whose volume-changes are high, in vitrification at least, are often con- 
siderably weakened by shrinkage-cracks inside the shell of the ware. Ex- 
amples can be found in both groups of clay where these properties are 
reversed, but the above is true in general. 

4th. Any clay, on firing, goes through a considerable series of 
changes or stages from the comparatively weak or unstable raw 
condition to the comparatively strong and permanent burnt condition. 
The changes are usually in the direction of increasing density, increasing 
strength, increasing shrinkage, decreasing porosity and decreasing 
specific gravity. But in any clay, a point is attained when these changes 
reach a condition of balance — when the claj'' is at its best — and further 
increase of heat leads to a reversal of all these properties. That is, the 
clay grows less dense, less strong, bloats instead of shrinks, and develops 



48 BULLETIN ELEVEN 

marked porosity. The strength, therefore, will vary quite widely, 
according as the burning process is stopped before this culmination, or 
at it, or subsequent to it. 

In the glacial and alluvial clays, the burning is customarily stopped 
considerably short of the culmination point of the clay's heat treat- 
ment, and while its strength is still undev^eloped. This is done to 
retain in the product the quality of porosity, to which a high value is 
assigned, for reasons discussed later. 

In shale clays, the burning is generally carried to fuller maturity 
and the properties attained represent approximately the greatest strengl h 
and minimum porosity which the clay will develop. This is done on 
the theory that a dense vitrified body is the best for roofing-tile purposes. 
It will be seen, therefore, that the two hostile camps, advocating res 
pectively porous and vitrified tiles, select their materials, treat them, 
and fire them, all with a view to developing these two divergent sets of 
properties. 

5th. The cooling of any highly heated clay body is attended with 
risks — sudden cooling will crack practically any clay product and the 
thicker and more thoroughly vitrified it is, the more certain it is to 
undergo cooling strains in excess of its resisting power. Therefore, 
those who favor the vitrified roofing tiles must take a constantly higher 
risk of loss in handling their product, than those whose product is porous 
and which will therefore stand cooling with less likelihood of dunting. 

The development of strength has been shown in the preceding 
discussion to be conditioned on a considerable number of allied and 
interdependent factors. It has been shown that the pushing of a clay 
body to that stage of burning which will produce the maximum of 
strength cannot be done without producing other changes which to 
some extent are contrary to or harmful to the production of a desirable 
product. It therefore becomes a matter of judgment, for each manu- 
facturer to decide for himself. 

POROUS vs. VITRIFIED ROOFING TILES- 

As before stated, this question is an ever present one in the roofing 
tile industry, and in the nature of the case it is one which never can be 
settled, for as long as men's minds work independently, so long will the 
facts be subject to different interpretations. 

Numerous examples of ancient roofs covered with both kinds of 
tile can be pointed out which have by no means gone to pieces,or given any 
other trouble. Hence, at the outset it must be admitted that each side 
is partly in the right so far as claiming good qualities for its own product 
is concerned, and in the wrong in most that they say about the baa 
properties of the other kinds of tiles. While it is a fact that more roota 
built of porous tiles have gone to pieces than in the case of the vitrified 



GEOLOGICAL SURVEY OP OHIO. 49 

ones, it must not be overlooked that there are hundreds of roofs built of 
the porous variety to single ones of the vitrified. A comparison, to have 
value, would have to consider percentage oi failure in each case. For 
instance, in France and Germany, the two largest tile centers in the 
world, the manufacturers are producing hardly anything but the porous 
tiles. Tiles that have been on roofs in those countries literally for 
centuries have been found to absorb a high per cent of water. This fact 
alone should show that a high degree of porosity is not necessarily proof 
of inability to stand frost and bad weather. 

As to the vitrified tiles, no one questions their durability when once 
in position, but there is an objection to them which is well founded. 

It frequentlj' happens that tiles are laid upon a roof of open con- 
struction. That is, the roof is not sheathed soHdIy in the usual manner, 
but the tile are hung on wooden or iron purlins, spaced apart horizontally 
on the roof just so as to accommodate the length of the tile. When a 
roof is so covered, and the roof is examined from beneath, the under 
side of the tiles are open, or exposed to view. 



Fig. 18— Under Side of Open ConstructLon Roof. 
For various reasons, among them fire protection, many roofs of the 
above style are used on boiler rooms, power houses, storage houses, and 
buildings of like nature. It very frequently happens in cold winter 
weather that the air in the interior of such a building becomes of high 
humidity. Such air, upon rising in the building, will come in contact 
with the under surface of the cold tiles, and will deposit water as dew upon 
them. Should the roof be very steep, the water thus deposited may, 
in the case of vitrified tile, course along down from tile to tile, but under 
ordinary conditions it will form drops or beads of water, which will in 
time reach a size where they will drop off or drip. A dripping roof often 
causes much damage and annoyance where expensive machinery or ma- 
terial must be kept dry, 
4— a. B. 11. 



50 BULLETIN ELEVEN 

The above tendency of .vitrified tiles to form dripping roofs has been 
the chief argument of the maker of porous tiles against his opponent. 
He has claimed that porous tiles under the conditions set forth above 
will never sweat or drip, but instead, on account of their porosity, will 
absorb the moisture, and gradually evaporate it into the atmosphere on 
the outside. The fact that it is only in places of the sort described above, 
and in roofs built as above, that trouble from dripping is observed, is 
a point in the controversy seldom mentioned by the maker of porous 
tiles. 

The tendency of soft-burned clay products to disintegrate by frost 
action has been mentioned, and it has undoubtedly caused the failure 
of an occasional tile and an occasional roof, but it is not a common defect, 
and it does not occur in many cases when the extreme porosity of the 
tile seems to invite it. In order to understand this fact it will be neces- 
sary to study the plays used, and the method of manufacture pursued. 

With very few exceptions, porous tiles are made from the soft or 
unconsolidated clays, of alluvial or glacial origin, while the vitrified 
ware comes largely from shale. The fact that few soft clays will stand 
vitrification in thin wares, like roofing tiles, while shales as a rule will, 
shows why one kind of clay and one kind of tiles are thus associated. 
The manufacturer using shale under the ordinary methods of prepara- 
tion knows that his ware will be too weak and porous, and that it will 
not stand up under freezing and thawing conditions unless it is well 
vitrified. Thus each manufacturer is giving the treatment which his 
material requires, and is doing so under necessity. 

The question now arises why, if many roofs of porous ware stood 
for centuries, is it necessary for the user of shale clays to vitrify his 
product? 

This subject as applied to bricks has received recently very careful 
treatment at the hands of Mr. J. C. Jones,* a digest of whose article 
follows: 

Taking bricks of different degrees of hardness as manufactured 
from different clays by the soft and stiff mud processes, after deter- 
mining their absorption and porosity, they were then subjected in a 
completely saturated state to a severe freezing test, extending through 
twenty freezings and thawings. The bricks were then crushed, together 
with unfrozen duplicates, in an Olsen testing machine. The following 
table shows the results of the freezing test. 



*Jones, J. C., Transactions Amer, Cer. Soc, Vol. IX, p. 528. 



GEOLOGICAL SUBVEY OF OHIO. 



51 



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52 BULLETIN ELEVEN 

Mr. Jones says, "As may be seen, there is little relation between 
the hardness of the brick and its resistance to frost. The surface clay 
suffered greatest loss when burned medium hard. The soft-mud shale 
suffered most when hard burned and the softest brick the least, while 
with the wire-cut shale brick, the soft and medium hard suffered most 
and the hard burned much less.*' 

He also points out that there is little if any relation between the 
amount of pore-space and resistance to frost. This is in accordance 
with the work of Dr. Buckley* on building stones. Jones further says, 
'The rate of absorption does, however, seem to bear a much closer relation 
to the resistance to frost than do the other factors. This is true since 
the rate of absorption is governed by the same factor that controls the 
rate of flow through the pores, and consequently relief from danger of 
damage by frost." In conclusion he says, *'It is of vital importance to 
consider the future position and condition in which brick are to be 
placed, in making tests to determine the ones best adapted. In situ- 
ations where saturation is the controlling condition, as in foundations, 
the brick that contains the least pore space is best, but in places where 
the brick can drain, the one with large pore channels is best." 

In further explanation it may be said that the degree of cohesion 
attainable in bodies made Trom strong plastic glacial and alluvial clays 
is very different from that obtained in weak sandy clays, or in shales. 
The former permit softening under the action of water, and a body of 
thoroughly mixed and thoroughly adhesive grains ensues. The shale 
does not soften to the same degree with water, and its comparatively 
coarse granules do not knit or assume as dense a body structure prior 
to burning. If burnt to the same degree, represented by an absorption 
of twelve or thirteen per cent, of water, the body made from the strong 
clay will probably defy frost, from Its highly developed, but not too coarse, 
intercommunicating pore-system. The body made from a sandy or 
shale clay will probably be entirely unsafe from frost, on the other 
hand, because its composite grains, consisting of very fine particles, 
have perhaps hardened enough and become dense enough, but between 
the grains themselves, little or no bond has yet been developed, on 
account of their size and imperfect contact with each other. Their 
pore-system is coarse, the cavities large, and the elastic strength of 
the walls of the pore system is yet low. In other words, the structure 
consists of a mass of grains, themselves sufficiently vitrified to stand 
frost, but insecurely bound together as yet, and therefore not frost-proof. 

The strong plastic clay-body will thus stand while the still 
granular shale-body will not. But if we now raise the temperature to 
a point where both clay? are reduced to their minimum absorption, 
there is a very strong presumption that neither will fail from frost. Cer- 



*Buckley, E. R. Quarrying Industry of Missouri, Mo. Geol. Surv. Vol. 2, 
Second Series, p. 45 



GEOLOGICAL SURVEY OF OHIO. 53 

taiiily the shale will not, if it be of the type variety. The difference is 
that when the requisite heat was reached, the shale grains amalgamate 
and sinter together to a degree that the relatively coarser plastic 
clay can not equal, and it produces a dense vitrification, in which 
almost no water is admitted, and in which the factor of strength of the 
pore walls is very high. The condition of the plastic clay is meanwhile 
improved also as regards frost strength, though that was not needed, 
but as a rule it develops warping, sticking or other troubles in burning 
which make it impractical to use such heat in burning it. 

One of the very strongest advocates of porous roofing tiles in Amer- 
ica is the veteran tile maker, Mr. Charles Stolp of Chicago Heights, 
Illinois. He expresses his idea on the importance of adequate prepa- 
ration of the clay as follows: 

*'A tile to be durable, though porous, must receive its strength 
from the preparation of the clay, and not depend on the burning to 
produce its weather resisting qualities.'* 

One cannot study the methods of roofing tile manufacture in the 
old world without observing that they fully realize the importance of 
the above statement. They take superficial clays w^hich have been 
weathering for centuries, and put them through a most exhaustive 
treatment of grinding and mixing, after which they still further prepare 
them by aging the clay in damp cellars for wrecks before use. All of this 
tends to develop the cohesive strength of the clay. 

Tiles made from cky thus prepared, though porous, will stand, 
and have stood, against the severe weather conditions of Sweden, 
northern Germany and northern Europe, and in this, our own country. 

In this connection, the table on page 54 shows the absorption per- 
centage of a number of brands of tiles which have been in use for long 
periods in this country with excellent results, will be interesting. In 
all cases, the samples were taken from roofs where they had done serv- 
ice, and the determinations were made by the writer for this purpose. 

By reference to the table on page 54 it will be seen that sixteen 
different tiles were used in this test, representing eight different clays, 
as follows: 

Three shales, three alluvial red-burning soft clays, one shale and 
alluvial clay mixed, and lastly, one No. 2 plastic fire clay. 

It was thought that these samples would fairly well represent 
the field, not only as to kinds of material used, but in the variations in 
absolute absorptive capacity and duration of exposure in actual service 
on roofs. 

Tiles Al and A2 were hand-made, from a soft alluvial clay, and 
burned to a moderate degree of hardness. Each can be easily scratched 
with steel. The total absorption for 125 hours was 12.76% and 14.69% 
respectively. These tiles have seen 35 years service on a roof in north- 
central Ohio, but they show no signs of weakness or disintegration. 



54 



BULLETIN ELEVEN 



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Tiles Bl to B4 inclusive were also made of a soft red-burning clay. 
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medium-burned ones in this set. Bl, for instance, took up 7.17% of 
water, while B4 absorbed 21.46%. It goes without saying that this 



GEOLOGICAL 8UEVEY OP OHIO. 55 

latter tile is very soft and easily cut by steel, while Bl is scratched with 
difficulty. Considering the length of time, 92 years, that these tiles 
were in use, and the high absorption of B2 and B4, it is quite signifi- 
cant that they should have remained in perfect condition. 

Tiles CI and C2 were made by modern machinery and modern 
methods, from a soft alluvial or semi-glacial clay. While the absorption 
in these tiles is high, nearly 15%, it should be said that their abiUty to 
withstand freezing and thawing is no doubt largely due to the thorough 
preparation given the clay, thus developing a high internal cohesive 
strength. 

Tiles Dl and D2 were made from shale which had been ground and 
screened to 18 mesh, pugged in an ordinary pug mill, and then made 
directly into tiles. It will be noted that the absorption in these tiles is 
very much lower than in those described previously. While these two 
tiles have been in use four years in a northern climate, it is the writer's 
opinion that the one having an absorption of 6.02% is bordering very 
closely upon the point of failure from disintegration. 

Tile El has been in use 15 years on a roof in central Ohio. The 
tile was made from a mixture of clay and shale, prepared by pugging in a 
pug-mill, and then forming into tile on a hand press. It will be seen 
that the per cent, of absorption is about midway between the tile made 
from shale and the average clay tile. 

Tiles Fl and F2 were made from a shale. The latter was ground 
in a dry-pan, and then thoroughly pugged in a wet-pan before being 
formed into tile by power machinery. These tiles were both harder 
than steel; although they show an absorption in the one case of over 
2J^ per cent., they would fall into the class known as vitrified tiles. 
In fact tiles Dl and D2 are sold as vitrified tiles, but by noting the 
per cent, absorption it will be seen that they are a long way from being 
such. 

While tiles Fl and F2 were used on a roof in Ohio for 18 years, they 
have recently been removed from the roof, not from any disintegration 
or failure of the tile, but on account of the roof leaking. The tiles 
were very poorly made, and were exceedingly crooked or warped from 
the extreme degree of vitrification to which they had been burned. 

Tiles Gl and G2 were made from plastic clays. Gl was made from 
a red-burning soft clay, while G2 was made from a plastic buff-burning 
clay. It will be observed that the total percentage absorption is nearly 
the same in each tile, but the rate at which the absorption has taken 
place has been very much faster in the red tile than in the buff. Both 
tiles were harder than steel, and though in use for 35 years, are as 
perfect today as when made. 

Tile HI was made from a No. 2 plastic fire-clay, which, after being 
pugged, was made up by the hand-press method. While the absorption 
was 7.74 per cent., the tile has withstood the 36 years* use perfectly. 



56 



BULLETIN ELEVEN 



In this connection a paper by Wheeler*, gives a similar table from 
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»o 








CM 




CO 


CM 



X 
00 



00 



l^ 


CM 


lo 


CM 






X 








X 




X 


o 


o 

o 


CO 

o 


1—4 




CM 

1-4 

O 
4-> 


• 

o 


CO 





1-H 

• 

o 

CM 


• 


CO 

• 

o 


CO 

o 


CO* 


CO 




o 


CM 


1—1 


CO 


o 






CO 








r-t 




»c 


q 


o 


o 


o 


CM 






»« 








CM 




CO 


1-H 



x' 



x' 



l-H QC 



q6 
o 

4-> 









1 


























1^ 






»-i 








•—1 
1 


CM 

1 


CO 


Tf 


< 


PQ 


PQ 


O 


Q 


» 


w 


^ 


o 


ffi 


w 


ffi 


X 


ffi 



X 



From the foregoing tables it can very clearly be seen that the per- 
centage absorption of various weather resisting tiles has a very wide 

^"•Wheeler, H. A. Trans. Amer. Cer. Soc. Vol. VIII, p. 154. 



GEOLOGICAL SUEVEY OF OmO. 57 

range; extending in table No. 3 from 1.44 to 21.46, a total difference of 
20.04. The highest absorption among the shale tiles is seen to be 6.02 
per cent., while the highest from plastic clay tiles was 21.46 per cent. 
The lowest absorption from shale tiles was 1.44 per cent., while the 
clay tiles gave 2.26 per cent, as the lowest amount. 

From these figures and a study of the durability of the tile in ques- 
tion, it is evident that the percentage of absorption is in no way a meas- 
ure of the durability of the tile, or its liability to disintegrate. It is 
quite possible that a microscopic study of the tile bodies would throw 
considerable light upon this question, and would perhaps give a bet- 
ter way of studying the ability of a tile body to resist freezing, than 
does the absorption test. The only value that can be attached to the 
absorption test is its measure of the increased strain or load put upon 
roof members by rains, or melting snow, which will be discussed a 
little later. 

A second objection to porous tiles is that they become dirty and 
old-looking very shortly after laying. This is true in many instances 
especially in districts where much smoke and dust prevails. In cases 
where the* rain water is desired for domestic use, this objection may 
become one of importance, but in many of our modern buildings it 
is in many cases desired to have the structure present an old or rustic 
appearance, in imitation of some ancient building. In such cases, 
the use of a porous tile has an advantage over the vitrified. 

A third accusation against tiles of high porosity is their tendency 
to absorb large quantities of water during prolonged rains, and thus 
increase in weight to a degree prejudicial or even dangerous to the 
roof timbers. Referring to tables Nos. 3 and 4, the maximum ab- 
sorption recorded in either set of tests is 21.50 per cent. Allowing, 
for the sake of argument, that every tile in a roof was able to absorb 
the maximum figure found, and that it was so situated as to have op- 
portunity to become fully saturated, the increase in weight of the roof 
would not exceed 25 per cent. No roof should be constructed with 
a factor of safety so small that an overload of several times this amount 
would in the least endanger it. Similar loading from heavy snow-falls 
is common in all northern latitudes, and in many cases wind pressures 
amounting to more than 20 per cent, of the weight are common. There- 
fore, while an increase of weight from water absorption is an unques- 
tionable fact, still it ought not to be a source of the least danger to a 
roof otherwise safe. 

This argument is rather a "trade talking-point" than a real or 
serious accusation against soft-burnt tiles. No roofing tiles in use are 
apt to absorb as high as 20 per cent. Individual tiles may do so, but 
a whole roof of such tiles would be rare. Further, it is always unlikely 
that the tiles in a roof will be so situated that total absorption becomes 
possible. A roof covered with slowly melting snow may easily reach 



58 BULLETIN ELEVEN 

60 or 80 per cent, of its total absorption, but no higher figures are 
probable, and while absorbing water on one side, it is usually evap- 
orating it on the other. 

The absorption test is more useful in this connection than as to 
frost resistance, however, and it should be made to note not only the 
total absorption of the tile, but the rate at which absorption takes 
place. 

By reference again to table 3, it will be seen that a number of 
the tiles absorb from 70 to 90 per cent, of their total amount within the 
first fifteen minutes. Especially, the soft or very porous tiles, such 
as A2, B2 and B4, have, at the end of one hour, only increased their water 
content by less than 2 per cent, over what it was at the end of a fifteen 
minute immersion. These tiles would throw an increased load of 10 
to 15 per cent, upon a roof, during a very short rain storm; while tiles 
like D2, Fl, F2, Gl, and G2, would pass through a long continued rain 
without materially increasing the load. The small increase taken 
up would be easy and gradual, thus throwing only gentle weight-changes 
upon the roof. 

Manufacturing Condftion& — In the manufacture of the two kinds 
of tiles, the porous tile manufacturer should make his tile before it goes 
to the kiln, while the vitrified advocate depends on the burning to make 
his tile. In other words, the porous tile should receive much the great- 
est attention in the preparation of its raw material and in the forming, 
for if the tile is not strong and solid wiien dried, it will scarcely harden 
and strengthen enough in the firing process to make it frost proof. The 
vitrified tile may be made from granular, poorly-prepared raw material, 
but if it is of the right vitrifying properties, it may be made durable 
by hard burning. 

Which tile is the more profitable to the manufacturer? The answer 
should be self-evident. The maker of porous tile, by spending great 
care in handling the crude, raw material, the working of which can 
be largely done by machinery, obtains a product which goes into the kiln 
in sound, straight condition. By stopping the burning at a point where 
the physical strength, though not at its maximum, is sufficient, he obtainsa 
product which has not undergone severe volume changes, and therefore 
remains sound and straight and strong, but not brittle. His loss from 
overfired wares should be nothing, and his loss from warped or cracked 
or dunted wares should be very low, and his losses from handling, un- 
equal kiln pressures, tilting, etc., should be at a minimum. 

With the maker of vitrified tiles it is different. In the burning it be- 
comes necessary to use some system of saggers as supporters for the ware, 
on account of the great shrinkage and consequent tendency to warpage, 
cracking, rolling of the ware in the kiln, resulting in wholesale defor- 
mation, etc. The handling and breaking of saggers or platform bricks 



GEOLOGICAL SUKVEY OF OHIO. 59 

is an added expense; and in addition a large amount of heat is con- 
sumed in heating up this dead material each time. In some few cases, 
it is feasible to combine two kinds of ware, so that one will serve as 
the sagger and the other the contained charge, but this condition does 
not often obtain in roofing tile factories. 

As it is desired to have the ware in all parts of the kiln vitrified, 
it often happens that ware nearest the fire will be overfired and ruined. 
Then large numbers of the tiles will warp and twist while under a 
vitrifying heat, no matter how carefully placed in setting, resulting 
in their loss, or in putting them in the second-class stock or cull. The 
percentage of good No. 1 wares brought from a kiln of vitrified tiles is 
very seldom 75 per cent, and the difficulty of disposing of the culls 
and seconds makes it necessary to assess on the first-class goods a 
large share of the total manufacturing cost. 

Hence, it can easily l>e seen which manufacturer is spending the 
greatest amount of money to make his ware durable, when the losses 
of the two systems arc taken into consideration. 

If a manufacturer wishes to make use of shale clays, it would be 
more profitable to him to prepare his clay more thoroughly — that is, 
grind it extremely fine, temper it and allow it to age in bins until thor- 
oughly, disintegrated — it would then not be necessary for him to burn 
his product to such a high degree of vitrification in order to make it 
weather-resisting. The writer firmly believes that with shales properly 
tempered by grinding and aging, it would not be an}^ more necessary 
to vitrify the ware than it is with tiles from the soft clays, and it is 
advantageous not to have the tile too vitreous. If it will absorb water 
up to about 5 per cent, of its dry weight, it will prevent sweating and 
dripping when laid on open construction. 

PATENTS ON ROOFING TILES. 

From the beginning of roofing tile manufacture on a commercial 
scale in this country, up to within the last decade, it was the general 
practice for plants to manufacture tiles whose shapes were patented as 
an invention, either their own, or some one else's oi:)erating under royalty. 

In fact, from time to time large sums have been paid for patents of 
roofing tile designs, and in many cases the designs were found to be 
impractical for manufacture in a commercial way. In one instance 
known to the writer, $50,000.00 was allowed in stock for a patent on 
a tile design which was found to be be so expensive to manufacture 
that no one would use it, if free to do so. It certainly did not need a 
patent to protect it from infringement. Many of the older companies, 
that have in the past held patents, have allowed them to run out without 
effort to obtain modifications which would keep the patent alive. 

The time has come, in the manufacture of roofing tiles in this 
country, that no single design is going to find universal acceptance 



BULLETIN ELEVEN 

or control the market. There are enough unpatented designs of 
tiles of perfectly commercial grade, in all styles, so that no one should 
think that a new patent design will protect him from competition. 
Today, it is a question of producing tiles of the proper quality at the 
proper price. 

As a matter of general interest to roofing tile makers, present and 
prospective, it has been thought worth while to record in this volume 
some statistics as to just what has been done in the way of patents 
on roofing tiles in this country. The data have been compiled from a 
study of the records of the United States Patent Office. It is needless 
to say that only a very small per cent, of the patents taken out have 
ever been followed by actual manufacture of tiles according to the pat- 
ented design. 

Listing these roofing tile patents according to their distribution 
in the states from which they originated, the order is as follows, in- 
cluding all patents prior to 1909: 

TABLE No. 5 
Patents Granted for Roofing Tile Designs, Originating in the United States. 



State 



Ohio 

Illinois 

Maryland .... 
New Jersey. . . 
New York . . . 
Pennsylvania. 

Indiana 

Missouri 

Massachusetts 

Iowa 

Michigan .... 

Florida 

Mississippi . . . 
Georgia 




30 

19 

12 

10 

10 

8 

8 

8 

4 

3 

3 

2 

2 

1 



State 



No. 



Kentucky 

California 

Colorado 

Connecticut . . . , 

Kansas 

Minnesota 

North Carolina. 
New Hampshire 

Oregon 

Tennessee 

Texas 

Vermont 

West Virginia. . 



Total 



2 



1*22 



GEOLOGICAL SURVEY OF OHIO. fji 

TABLE No. 6 

Patents Granted in the United States, for Roofing Tile Designs Originating 

in Foreign Countries. 



Country i No. 



Germany 22 

England ] 5 

France 

Denmark 

Hungary 

Sumatra 

Sweden 



Total 



3 
1 
1 
1 
1 



34 



Observing the above table it may be plainly seen in what sections 
of the country the greatest interest and activity has existed in roofing 
tile manufacture and use. Ohio outranks any other state in the number 
of patents taken out, as it always has in the number of roofing tile plants. 
It will also be noted that the southern and western states, which cli- 
matically are perhaps best suited to the use of cheap forms of tile, fall 
far behind. It is only very recently that there have been any roofing 
tile plants in these states. 

Among the foreign countries, Germany leads with over three times 
as many patents as any other country, while France, one of the greatest 
tile using centers in the world, has taken out but three patents in this 
country. 

The first patent for a roofing tile design was taken out in this 
country by J. Parker, August 15, 1835. The tiles were of a form 
resembling brick, or possibly more like the promenade tile or quarries 
of today. 'No provision was made for the tiles to overlap or to lock, 
hence it must have been the intention to bed them in clay or cement, 
making to all intents a pavement of the roof, very much as the Chinese 
do at the present time. 

The next patent was was taken out in December, 1855, by 
C. Graessle. This tile was of the interlocking type. One-half of the 
tile was made in a low half-round; the other half, consisting of the pan of 
tile, was flat. It was protected on the edge by two parallel ribs, with 
a gutter between for the tongue of the adjacent tile. That is, the half- 
round of one tile acted as a cover for the locks on its neighbor. The 
upper end of the tile carried a lug or projection on the under side, by 
which the tile could be hung on the roof purlins. On the top side of 
the upper end of the tile were two cross ribs to form the head-lock, 
while the lower end of the tile was provided with two counter tongues. 
Thus it can be seen that a good interlocking tile was devised and the 
principles of interlocking understood in this country as far back as 
1855. 



62 BULLETIN ELEVEN 

In April, 1858, J. S. Graessle obtained a patent on an inter- 
locking tile of very good design. In fact it is superior to many designs 
on which patents have been granted since. The tile is constructed with 
a double locking device on all four sides, and has a broad flat pan for 
conveying the water. 

• The first patent on an interlocking shingle tile was taken out in 
1867, by Wm. Cranage, of Cleveland, Ohio. The idea in this patent 
was that of making the tile as though it were composed of two separate 
parallel plane surfaces of the same size and thickness, of which the 
upper one had been shifted so that it no longer covered the lower 
exactly, but left a side and end of the lower plane exposed for a half- 
inch or so wide, thus making provision for overlapping. This tile 
would make a very uninteresting roof in any case, for the method of 
overlapping the edges by extensions of half-tile thickness produced a 
perfectly plane surface from tile to tile in the same tier, and the only 
relief was that due to overlap of one tier on another. The vertical lines 
would thus be lost almost at once, and. only the horizontal would be 
visible, even near by, thus accentuating the characteristic fault of this 
kind of tile unnecessarily. 

The true interlocking shingle tile, having side and end-locks of 
the regular tongue and groove pattern, did not appear until 1874, when 
Louis Hamel, of Baltimore, obtained a patent on such a design. 

The first patent covering a normal or Spanish tile was obtained 
in 1873, by Daniel Swain, of Dover, New Hampshire. His plan* 
provided for the use of two patterns, one of which was a broad, concave 
tile, made flat on the under side, to allow it to sit down flat on the sheath- 
ing boards. Rows of these broad tiles were carried up the roof in close 
parallel lines, allowing each upper tile to overlap the next lower as usual. 
To cover the joints between the edges of the parallel rows, small half- 
round tiles were used. 

During 1886, three patents were granted for Spanish or roll tiles, 
with the pan and roll combined in one piece. The first of these was 
taken out in July, by Albert Aldrich, of New York. His design, 
however, was impractical to manufacture, on account of the locks 
requiring undercuts, which cannot be made by ordinary pressing ma- 
chines. A much better pattern, and entirely practicable to make, was 
patented by Edwin Bennett, of Baltimore, during the latter part 
of the same year. 

The first patent on a tile design to be run out in bar form on an 
auger machine and subsequently cut into appropriate lengths was taken 
out in 1889, by Joseph Repp, of Akron, Ohio. This tile, instead of 
having a roll or rounded elevation on its face, was made with an angular 
ridge or inverted letter V, with a pan and a single side-rib. This design 
was entirely practical commercially, and was manufactured for some 



GEOLOGICAL SURVEY OF OHIO. 



63 



time. This design is of interest chiefly because it was the forerunner 
of the numerous patterns of auger-machine Spanish or S tiles that 
have followed. 

The first auger-machine interlocking tile to be patented in this 
country was that of C. Jungst, of Germany, during the year 1887. His 
tiles are provided with side-locks only, the end-locks being formed by 
the upper and lower ends of two contiguous tiles overlapping, like 
ordinary shingle or S tiles. 

The largest number of patents on roofing tile designs taken out 
in any single year was in 1890, when twelve were granted. 

The number of patents taken out annually from 1890 dropped 
off until 1903, when it -increased to ten for the single year. 

During 1908, there were seven patents taken out, but they were 
nearly all for cement tiles. For the benefit of those who may be inter- 
ested in looking up the literature of tile patents more carefully, the 
following list of patents granted up to February, 1909, has been prepared: 

TABLE No. 7. 
Consecutive List of American and Foreign Roofing Tile Patents. 



Date of Issue. 



Year. 



Month and 
Day.. 



Name of Grantee. 



Number 
of 
Patent. 



Remarks on Style of Deslgrn. 



1835 
1855 

1858 
1862 

1862 

1867 
1867 

1867 

1870 
1871 
1871 

1872 

1872 

1873 

1874 

1874 
1874 
1874 

1874 



Aug. 15 
Dec. 11 

April 27 
May 6 

Aug. 19 

Nov. 12 
Dec. 3 

Dec. 10 

Oct. 4 
Feb. 21 
Dec. 5 

July 23 

Aug. 6 

Aug. 19 

Feb. 3 

Feb. 3 

April 7 
May 5 

July 14 



k 



Parker. . 
Graessle 



J. S. Graessle . . . . 

/Samuel M. Logan 

IPhilo E. Baker. . . 

! J Isaac Marsh, Jr.. . 

I \Griggs Marsh . . . . 

George Cook 

William Cranage . 

Orville Manly . . . . 






William Utley 

Charies Howard 

John B. Hughes 

/Isaac Hodgson . . . . \ 

1 William H. Brown ./ 
/Alexis Roux ...... 1 

\Pierre Roux j 

Daniel Swain 

Sanford S. Perry . . . . 

Garry Manvel 

John F. Graessle .... 
John T. Weybrecht . . 

Louis Hamel 



not giv. 
13,906 

20,059 
35,164 

36,225 

70,805 
71,583 

72,060 

108,068 
111,938 
121,624 

129,826 

130,156 

142,056 

147,018 

147.061 
149,469 
150,642 

152,991 



Flat or pavement tile. 

Interlocking. 

/Interlocking of fairly good 
\ design. 

Pan tile. 

Quarry tile for roofs. 

Improved pan tile. 

Flat or shingle tile. 
/ Quarry tile to be laid in 
1 coal tar and clay. 
/Flat or shingle tile, very 
\ little change over 7 1 ,58^ 

Interlocking tile,poor locks 
/Improved pan tile, like 
1 70,805. 

/Improvement on tile or 
1 glass roofs. 
/Interlocking tile with good 
1 locks. 

/Spanish or normal tile, too 
\ heavy. 

Improved pan or Roman 
tile. 
^Overlapping or interlock- 
\ ing tile of poor design. 

Diamond tile. 
/Interlocking tile of French 
design. 

Interlocking shingle tile, 
\ locks good. 



64 



BULLETIN ELEVE^' 



TABLE No. 7— Continued. 
Consecutive List of American and Foreign Roofing Tile Patents. 



Date of Issue. 



Year. 



Month and 
Day. 

• I 



Name of Grantee. 



Number 

of 
Patent. 



Remarks on Style of Deslgrn 



1874 
1874 

1875 

1875 

1875 

1875 
1875 
1876 
1876 

1876 

1876 

1877 

1877 

1877 

1877 
1878 
1879 
1879 

1879 

1881 

1881 

1881 

1882 

1882 

1883 

1883 

1885 
1885 

1885 

1886 

1886 

1886 
1886 

1886 

1886 

1887 



Sept. 8 
Dec. 1 

Mar. 2 

Mar. 30 

May 4 

June 8 
Nov. 30 
Feb. 22 
Mar. 28 

Aug. 29 

Dec. 26 
June 26 

Sept. 25 

Nov. 6 

Dec. 18 
April 30 



Feb. 
Feb. 



4 
4 



Aug. 26 
Mar. 15 
Mar. 22 

Sept. 27 

Feb. 7 

Nov. 21 

Mar. 20 

Aug. 14 

May 5 
June 23 

July 28 

April 27 

July 13 

July 20 
Aug. 17 

Sept. 7 

Nov. 2 

April 19 



Edwin Bennett 
Louis Hamel. . . 



John M. Lewis 
Samuel Mills. . 



Garry Manvel 

La Fayette Parker 
Calvin T. Merrill . . 

Jonas Smith 

Cyrus M. Warren. . 

Jacob Greenawalt . 

George Elberg . . . . 
Philip Pointon . . . 



John W. Hoyt 



Hiram Stripe . . . . 

Philip Pointon . . 
Henry E. Merrill . 
George A. Taylor. 
Edwin Bennett . . 



Frank Waters 

iohn J. Williams . . . 
, rorenzo Lane 1 

\LaurinD. Wood worth/ 

William Barry 



Thomas B. Atterbury 

/Lorenzo Lane 

ILaurin B.Wood worth 
/Christopher McCarthy 
\James P. Gumming . 

Wilhelm Ludowici. . 



Fawcett Plumb 
Paul Simons . . 



John E. Donaldson 

Frank Hengesbach 

Carl Weise 

Elbert Aldrich .... 
Henry Hall 

John C. Litzelle . . 

Edwin Bennett . . . 

E. C. Lindemann . . 



154,828 
157,392 

160,445 

161,538 

162,836 

164,203 
170,582 
174,021 
175,533 

181,670 

185,632 
192,451 

195,607 

196,773 

198,414 
202,953 
211,944 
211,955 

219,044 

239,007 

239,104 

247,596 

253,174 

267,904 

274,354 

283,126 



317,414 
320,822 

322,917 

340,668 

345,400 

345.942 
347,425 

348,920 

351.956 

361,425 



Diamond tile. 

Interlocking quarry tile. 

Interlocking tile of poor 
design, requires two 
forms of tile. 

Diamond tile. 
/Overlapping or interlock- 
\ ing tile of poor design. 

Diamond tile. 

Diamond tile. 

Diamond tile, two piece. 

Cement shingle tile, 
f Diamond tile, slightly 
\ modified. 

Diamond tile modified. 

Diamond tile. 

Metal tile filled with ce- 
ment, would be imprac- 
tical. 

/Improved pan tile, side 
\ lock. 

Interlocking tile, poor locks 

Diamond tile. 

Pan tile. 

Improved diamond tile. 
/Interlocking tile, poor de- 
\ sign. 

Improved quarry tile. 

Diamond tile. 

/Flat tile with side lock, 
poor. 

Improved shingle tile, not 
good. 

Diamond tile, improved 
1 over 239,104. 
/interlocking quarry or flat 
1 tile, impractical, 
/interlocking tile of good 
1 design. 

/Flat shingle tile, method 
\ of fastening. 

Diamond tile, hollow. 

(Interlocking flat shingle, 
would be too expensive 
to manufacture. 
Interlocking. 
Improved Bat or shingle 

tile. 
Spanish tile. 
Facing or siding tile. 
/Holland pan tile, resem- 
\ bles Spanish tile. 
Spanish tile. 

/Spanish tile composed of 
\ two members. 



{ 



GEOLOGICAL SURVEY OF OHIO. 



65 



TABLE No. 7 — Continued. 
Consecutive List of American and Foreign Roofing Tile Patents. 



Date of Issue. 



Month and 
Year. Day. 



1887 

1887 
1888 

1888 

1888 
1889 

1889 

1889 

1890 
1890 

1890 

1890 

1890 

1890 

1890 

1890 

1890 
1890 
1890 
1890 
1891 

1891 
1892 
1892 
1892 

1892 

1892 
1892 
1893 
1893 
1893 
1893 
1893 
1893 



Aug. 2 

Aug. 16 
Feb. 7 

April 10 

July 3 
May 21 

Sept. 17 

Sept. 24 

Feb. 18 
April 22 

April 29 

June 17 

June 17 

June 17 

June 17 

June 17 

June 17 
June 17 
June 17 
Oct. 14 
Mar. 31 

Dec. 15 
Jan. 26 
June 21 
July 5 

July 26 

July 26 
Sept. 27 
Feb. 14 
May 9 
Aug. 8 
Dec. 26 
Dec. 26 
Dec. 26 
B. 11. 



Name of Grantee. 



Number 

of 
Patent. 



Remarks on Style of Deslgrn. 



Carl Jungst 



John E. Donaldson . 
Edward Walsh, Jr. .. 

Arthur W. Cooper . . 

Albert Diedrich 



/John Erec G us ten . . "I 
\6arl Wm. Braun . . . j 



Joseph Repp 



Robert Liddell 



E. C. Lindemann .... 
E. C. Lindemann .... 

John E. Donaldson . 

George H. Babcock. . 
George H. Babcock . . 
George H. Babcock . . 
George H. Babcock . . 
George H. Babcock.. 

George H. Babcock . . 

George H. Babcock . . 

George H. Babcock . . 

E. C. Lindemann .... 

Edwin Bennett 

/John E. Donaldson 1 
\Edward C. Elder . . J 

Basil Edwards 



Joseph Martin Wood 

Joseph Repp 

/Frederick N. Marvickl 

\ John Walter / 

Frederick N. Marvick 

Henri Sturm 

C. W. E. Wutke 

Francis Andrew .... 

Max Kaestner 

Andrew M.Cheeseman 
Andrew M.Cheeseman 
Andrew M.Cheeseman 



367,758 

368,386 
377,588 

380.864 

385,343 
403,837 

411,299 

411,666 

421.734 
426,289 

426.584 

430,362 

430.363 

430,364 

430,365 

430,366 

430.367 
430.369 
430.371 
438,321 
449,397 

465,364 
467,791 
477,346 
478,171 

479,441 

479.442 
483.180 
491.625 
497.161 
502,725 
511,506 
511,507 
511,683 



Auger made interlocking 
tile, suitable for cheap 
structures only. 
I nterlocki ng tile , poor 

locks. 
fCombined pan and roll tile 

of glass. 
Combination shingle tile 
and metal roof, not 
. practical. 

^Interlocking flat tile or 
\ quarries. 

Diamond tile. 

Improved auger made tile, 
the forerunner of the 
modern Spanish. 
'A combination flat and 
cover or joint tile, not 
commercial. 

Improved shingle tile. 

Roman or pan tile. 
/Interlocking tile, very 
1 poor locks. 
/Ornamental diamond or 
\ scale tile. 

Improved shingle tile. 
/Scale or modified diamond 
\ tile. 

Eave tile or starters. 
/Interlocking tile known as 
\ "Conosera." 

Hip tile. 

Gable tile. 

Comer or mitre tile. 

Interlocking Spanish tile. 

Pan and cover tile. 
/Interlocking tile, locks too 
\ shallow. 

/Improvement on shingle 
1 tile. 

/Interlocking tile with 
1 method of fastening. 
/Improved auger made 
\ Spanish tile. 

Overlapping flat tile. 

Interlocking tile. 
Interlocking hollow tile. 
Interlocking tile. 
Interlocking tile. 
Diamond tile. 
Pan and roll tile combined. 
Pan and roll tile combined. 
Pan and roll tile, two piece. 



66 



BULLETIN ELEVEN 



TABLE No. 7 — Continued. 
Consecutive List of American- and Foreign Roofing Tile Patents. 



Date of Issue. 



Year. 



Month and 
Day. 



1894 
1894 

1894 

1894 

1894 

1894 

1894 
1894 
1895 
1895 

1895 

1895 

1896 
1896 

1896 

1896 
1896 
1896 
1896 
1897 
1897 
1898 
1898 

1898 

1898 

1898 

1898 
1899 
1899 
1899 
1899 

1900 

1900 
1900 
1900 

1900 

1901 

1901 
1902 



Jan. 23 
April 10 

April 17 

July 10 

July 10 

July 24 

Oct. 16 
Dec. 4 
Mar. 5 
April 16 

Aug. 13 



Aug. 20 

21 
11 



Jan. 
Feb. 



April 14 

June 30 
Aug. 4 
Dec. 15 
Dec. 29 
Mar. 23 
Oct. 26 
Feb. 22 
April 26 

May 17 

June 14 

June 14 

July 19 
Jan. 24 
July 11 
Sept. 12 
Dec. 12 

Jan. 2 

May 29 
June 5 
June 19 

July 31 

Jan. 14 

Dec. 10 
June 10 



Name of Grantee. 



Number 

of 
Patent. 



Remarks on Style of Design. 



Wilhelm Ludowici . . . 
George H. Babcock . . 

/John Veen 1 

F. A. Dornberg . . . . / 
John E. Donaldson 
John Athern 

Samuel K. Cohen. . 



} 



Albert Kayser 



Christian Lesmeister 
H. Niederiaender . 
Thos. A. Aldridge 
Kad Thomann . . . 

/Michael Hoffelt . . 

\Matt Hoffelt 

Lucian F. Plympton 

George A. Taylor. . . 

Clinton Keiser 

/Gustav Krebs 

\ Abraham Weil . . . 

Heinrich Brocker. . 

Patrick F. Jones . . 

Milo Horiocker. . . . 

Wm. A. C. Waller 

Charies T. Harris. . 

John J. Merrill . . . 

Marshall C. Barber 

Abraham Weil . . . 



) 



} 



Jacob Freund 

Gustav Schulze 

Christian W. Schou . . 

Henry B. Skeele . . . . 
Wilhelm Borgolte . . . 

Emil Ahrens 

Hendrick Ludeling . . 
John E. Donaldson . . 

William D. Turnley. . 

Leopold Gnoth 

Gustav F. Kasch . . . 
Wilhelm Ludowici . . . 

Nicholas Daubach . . 

John W. Carnes .... 

George P. Heinz .... 
Albert Gustorp 



513,430 
517,832 

518,294 

522,686 

522,879 

523,353 

527,431 
530,119 
535,183 
537,732 

544,303 

544,770 

553,321 
554,274 

558,395 

562,798 
565,356 
573,328 
573,939 
579.481 
592.474 
599,312 
602,889 

604,035 

605,654 

605,750 

607,489 
618,197 
628,737 
633,019 
638,802 

640,338 

650,387 
650,939 
651,873 

654,717 

691,239 

688,641 
702,202 



Interlocking tile. 
Tower tile. 

Interlocking tile. 

Interiocking tile. 

Spanish tile. 

/Interiocking tile of French 
\ pattern. 

Interiocking tile. 
Interiocking. tile. 
Interiocking shingle tile. 
Interiocking tile. 

Interiocking tile, poor locks 

fPan and cover tile, two 
\ pieces. 

Pan tile. 

Interlocking flat tile. 

Diamond tile. 

Diamond tile. 

Spanish tile. 

Interlocking tile. 

Diamond tile. 

Shingle tile. 

Interlocking tile. 

Spanish tile. 

Diamond tile. 
/Improved auger made 
\ Spanish tile. 

Diamond tile. 
/Shingle tile with metal 
\ locks. 

Interlocking Spanish tile. 

Diamond tile. 

Diamond tile. 

Hollow interlocking tile. 

Small interlocking tile. 
/Glass tile and method of 
1 fastening. 

/Interlocking tile, side locks 
\ only. 

Auger made pan tile. 
/Interlocking tile similar to 
1 the Spanish. 
[Tile similar to Spanish in 
connection with a metal- 
cement joint. 
/Interlocking tile, poor de- 
\ sign. 

End locks for tile. 

Diamond tile. 



GEOLOGICAL SUBVEY OP OHIO. 



67^ 



TABLE No. 7— Continued. 
Consecutive List of American and Foreign Roofing Tile Patents. 



Date of Issue. 



Year. 



Month and 
Day. 



Name of Grantee. 



Number 

of 
Patent. 



Remarks on Style of Deslgrn. 



1902 
1903 

1903 

1903 

1903 

1903 
1903 

1903 

1903 
1903 

1903 

1903 
1904 

1904 

1904 

1904 

1904 
1905 

1905 

1905 
1905 

1905 

1905 

1905 
1905 

1906 

1906 

1906 
1907 

1907 



Sept. 2 
Jan. 13 

Jan. 27 

Feb. 3 

Feb. 17 

Mar. 17 
June 2 

July 28 

Aug. 18 
Sept. 15 

Dec. 15 

Dec. 29 
Jan. 12 

Feb. 23 

Oct. 18 

Oct. 25 

Dec. 6 
April 18 

April 18 

May 2 
Sept. 12 

Oct. 10 

Oct. 31 

Nov. 14 
Nov. 28 

Mar. 13 

Mar. 27 

April 17 
Feb. 19 

Feb. 26 



Holden Brock. . . . . . 

/William C. Sharp. .. 
\John C. Sharp 

Frank E. Coombs . . 



1 



Joseph Schall 

Jons Nilsson Mauntin 

Henrv B. Skeele . 
Abraham B. Klay 

Jacob Simmerman 

Johannes Veen . . 
Henry Ohaus . . . 

Carl Schlachter . 



George C. Zwerk . 

Walter P. Grath . 

/Henry Baden . . . 
\ William Gluss . . . 

Wilhelm Ludowici 

Carl Theo Seested 

Walter C. Mitchell 
Leslie G. Sharp . . 

Leslie G. Sharp . . 



} 



Leslie G. Sharp . 

« 

James H. Perrin 
Wenzel E. Miksch . 

« 

Ludwig J. W. Birn . 

Henry Meyer 

Lloyd G. Satterlee. . 

Frederick M. Lensch 
Orvey Price 



Henry Baden 

Edward E. Johnston. 

Edward H. Binns . . . 



708,307 
718,284 

719,193 

719,514 

720,831 

722,918 
730,131 

734,976 

736,801 
739,211 

746,747 

748,141 
749,182 

753,188 

772,363 

773,230 

777,058 
787,474 

787,475 

788.676 
799,259 

801,736 

803,524 

804,754 
805,884 

814,970 

816,252 

818,333 
844,453 

845,290 



/Interlocking tile, no head 
\ lock. 
Improved shingle tile. 

/Lock for interlocking or 
\ Spanish tile. ; 

Spanish tile, interlocking. 
[Corrugated tile made in- 
< terlocking by means o£ 
[ metal strips. ' 

Spanish tile, interlocking. 

Interlocking tile. 

/Improved shingle tile of 
\ glass or clay. 

Auger made pan tile. 

Improved shmgle tile. 
/Interlocking corrugated or 
"I Spanish tile. 
/Shingle tile to be made oi 
\ cement and metal. 

Interlocking Spanish tile, i 

Diamond tile. 



1 



Interlocking tile, two parts 
'^Interlocking tile, with 

• method of fastening, in- 
tended to be made of 
cement, no end locks. 

Mission tile, two pieces. 

Interlocking Spanish tile. 
/Modified shingle tile, to be 
\ press made. 
/Modified shingle tile, to be 
\ press made. 

Diamond tile, two parts. 

! Interlocking tile, auger 
made, no head locks, 
partly hollow. 
Interlocking tile, modified 
1 "Conosera." 
/Diamond tile preferably 
\ of cement and metal. 
Modified shingle tile. 
[Overlapping corrugated 
J tile, no end lock, prefer- 
1 ably made of cement 
1 and metal, 
f Shingle tile, of cement and 
\ metal. 

Diamond tile. 

Interlocking tile. 

^Shingle tile made of straw- 
board, lime or sand, 
metal and asphalt. 



68 



BULLETIN ELEVEN 



TABLE No. 7— Concluded. 
Consecutive List of American and Foreign Roofing Tile Patents. 



Date of Issue. 



Year. 



Month and 
Day. 



1907 

1907 
1907 



1907 

1908 
1908 

1908 



1908 
1908 

1908 

1908 
1908 
1908 
1909 
1909 



Mar. 26 

April 30 
May 7 

July 23 

Feb. 25 
Mar. 10 



Mar. 24 

April 21 
June 2 

July 7 

July 28 
Nov. 10 
Dec. 29 
Feb. 9 
Feb. 16 



Name of Grantee. 



Number 

of 
Patent. 



Remarks on Style of Desigrn. 



Charles C. Davis . . . . 

Albert Voigt 

Edward Coffin 



Ignatz H. Freund . . . 

Bertel R. Christensen 
Edward T. Winslow. . 



Michael Marte 



Carlos N. Bruzand 
Joseph Freund . 

Isham P. Walker 

Joseph W. Farr . 
Saniuel A. Jones 
Fred Lotulip .... 
Emery P. Auger 
Byron L. Bacot 



848,537 

852,402 
853,063 

860,796 

880,012 
881,522 

882.765 



885.663 
886.595 

802.917 



. . 894,489 
. 903,477 
. ; 907,824 
. 912.057 
.. 912,353 



/Shingle tile of cement and 
\ metal. 

Diamond tile. 

Diamond tile. 
fShingle tile with glass 
J opening preferably of 
\ cement, metal and 
[ glass. 

Pan and roll, cover tile. 
(Corrugated or angle tile in 
\ combination with angle 
j covers for the side joints 
fShingle tile having an em- 
I bedded metal hook for 
\ hanging the tile. Very 
I impracticable, metal 
I would be destroyed in 
[ the burning. 

Interlocking tile. 
/Interlocking tile, locks im- 
\ perfect. 

fPan tile with separate 
1 cover tile. 

fCement-metal sheets for 
\ roofing, no particular 
( style. 

Diamond tile. 

'Modified shingle tile, im- 
practicable to make on 
account of under cuts. 

Cement shingle tile. 
[Spanish tile, having an 
\ impractical lug on the 
\ under side. 



Other Patents Pertaining to Tiles or Tile Roofs. 



1890 
1891 

1891 

1901 
1903 



July 15 
Aug. 25 

Dec. 8 

Mar. 26 
Feb. 24 



John E. Donaldson .. 432,122 Die for forming roofing tile. 

T? r T;«^^r««*,« n iqa /Reissue of patent 361,425, 

E/. L/. Lfinaemann .... 11, loo < Snani«;h tile 

&'^.ja%to°n".::} 464,503 Y'^^^^^' '" 

I Means for rendering inter- 

G. A. Nebling 670,723 \ locking tile roofs 

1 , [ weather proof. 

Henry B. Skeele . . . . ! 721,246 | Metal fastener for tile. 



GEOLOGICAL SUBVEY OF OHIO. 69 

As stated before, the day of patented tile designs has nearly passed. 
The possible variations in the shapes, locks, and mode of attachment 
of the three fundamental varieties have been pretty thoroughly ex- 
ploited, and the possibility of a new design being brought out, which 
could play a new variation of this w^ell worn theme, and still have any 
real advantage in it over those which have been long since used, is now 
quite remote. We may fairly say that the roofing tile designs are now 
pretty well crystallized into a few types. What is needed at present 
is more tile plants to use these standard patterns in manufacturing 
tiles of first class color and strength. No one needs a patented design 
now to compete in the roofing tile business. 



70 " BULLETIN ELEVEN 



CHAPTER m. 

THE SELECTION OF CLAYS FOR ROOFING TILE 

MANUFACTURE. 

In the selection of a clay for the manufacture of roofing tile, the 
qualifications which should be most carefully considered are plasticity, 
strength, shrinkage, burning behavior and fusibility, color, hardness 
and porosity. 

In a careful search of ceramic literature, no data have been found 
bearing directly on the testing of clays for roofing tile purposes. In order 
to give as clearly and as exactly as possible just what the qualifications 
of a clay should be to make it suitable for roofing tile manufacture, 
it was thought best in the absence of any previous work, or any kind 
of recognized standards to go by, to make a thorough study of such 
clays as are or have been used for successful roofing tile industries, 
and let the data thus obtained serve as a basis for future judgments 
as to the fitness of clays for this purpose. 

There were in the country in the summer of 1908 fourteen such 
plants. There were several others which had manufactured roofing tile 
on a commercial scale at ons time, but which had for one reason or 
another gone out of the business. Samples were obtained from nearly 
all of the active plants and from some of the defunct ones. Owing to 
sensitiveness on the part of some of the manufacturers, as to tests of 
their clay being published, these samples are all listed in the following 
tables by letters instead of names, so that the source of the samples 
cannot be established from anything which appears in the report. 

For the benefit of interested readers, it may be said that all of the 
clays of which tests are published herewith were taken either from plants 
in active operation or recently defunct, and that of the active plants 
samples were obtained from all but a very few. In one or two instances, 
the objections of the management to having their clays studied could 
not be overcome. The list of clays studied, however, is strictly rep- 
resentative of the materials used in roofing tile manufacture in this 
country. Every type of clay which is used in any past or present plant 
is represented by one or more samples. In one case, the tile body is 
made of a mixture of three separate clays and a sample of each clay 
was taken and tested separately, and another sample of the mixture 
as a whole. 

The samples, with two exceptions, were taken either from the 
unground clay in the stock shed, or from the ground clay which had 



GEOLOGICAL SURVEY OF OHIO. 



71 



passed the dry-pan, it being desired to obtain the samples unaffected 
by any tempering operation. In the two exceptional cases, the clays 
were collected at the end of the pug-mill or tempering machine. As all 
of these samples were naturally soft plastic clays, it is believed that 
the tempering has produced but very little difference, and that after 
drying out and regrinding, they would compare closely with samples 
taken direct in the pit. 

Taking up the various properties of clays, it is deemed best to 
discuss the bearing that each has on the value of the clay before con- 
sidering the actual test as carried out. 

Plasticity* — Plasticity in clay is the property which it possesses, 
when mixed with water, of being moulded into desired shapes and of 
retaining its shape after moulding. It is not necessary to here go 
into the cause of plasticity, for which a number of theories have been 
advanced, none of which have been fully accepted, nor have any prac- 
tical methods been devised for the measurement of this valuable prop- 
erty of clays. 

Among practical clay workers, such terms as plastic, very plastic, 
poorly plastic, or medium plastic are used. Fine grained plastic clays 
are known as "fat," while sandy or coarse grained ones are termed 
''lean." 

The amount of water required to develop the plasticity of a clay 
is to a certain degree a measure of its plasticity. The finer the grain 
of the clay, the more water is required to develop its plasticity. In 
ball clays, for instance, as high as 30 or 40 per cent, of water may be 
required to get the best plasticity, while some shales will only need from 
15 to 25 per cent. 

The samples of roofing tile clays as described above were tested 
as to the amount of water required by each for plasticity. It was not 
possible to tell when the different samples reached the same degree of 
plasticity by any other test than the ordinary sense of feel. When 
tempered to a point where they felt right for manufacture, the amount 
of water was determined accurately, with the following results: 

TABLE No. 8. 

Showing Per Cents, of Water Added to Develop Working Plasticity in the Standard 

Roofing Tile Clays. 



Designation 
of clay. 


Percentage of free 
water contained 


Designation 
of clay. 

1 


Percentage of free 
water contained. 

ft 


Designation 
of clay. 


Percentage of free 
water contained. 


A 
B 
C 
D 
E 


18.31 
15.22 
22.22 
20.35 
19.16 


F 
G 
H 
I 

J 


20.65 
13.82 
21.22 
15.99 
20.83 


K 
L 

M 

N 
O 


18.97 
17.21 
15.86 
16.13 
18.74 



72 BULLETIN ELEVEN 

From table No. 8 it will be seen that Sample G is the only 
one that requires less than 15 per cent., while none of them reach very 
high figures. Sample C, with 22.22 per cent., is the highest. The 
average of all the samples is 18.31 per cent., which is about the same as 
shown by clays used in stiff-mud brick industry and similar processes. 

By reference to table 8 it will be seen that in a general way the 
clays requiring the larger amounts of water to. develop plasticity are 
also the ones that develop the highest drying shrinkage which would 
indicate a connection between the degree of plasticity, the water used 
in tempering, and the shrinkage in drying. Clays for roofing tile manu- 
facture should have a moderate degree of plasticity — sufficient to permit 
of their being easily worked, or moulded into the desired shapes, but 
excessive plasticity is dangerous, in that it indicates a similar excess 
in air shrinkage and the other drying qualities of clays and excessive 
lamination of the clay in manufacture. Clays with the highest degree 
of plasticity are the ones most likely to crack in drying. Then, too, 
the excess water that must be used in tempering extremely plastic clays 
causes increased expense in drying, as well as being more apt to dissolve 
soluble salts and bring them to the surface of the ware as a scum or 
whitewash. The tempering water is frequently highly impregnated with 
soluble salts, hence the use of less water in tempering the less plastic 
clays is an advantage. 

Strengtli* — The strength which a clay develops on drying is 
very important to the roofing tile manufacturer. His ware, for the 
greater part, is of thin cross section, and unless the clay has a fairly 
good strength, large losses will result in handling the ware during the 
setting, and still greater losses will occur if the ware is set without sag- 
gers, or some form of kiln supports, as roofing tiles are being set at the 
present time in several of the plants. In other words, the clay should 
possess strength enough to resist the crushing strain of the superim- 
posed tile, in such modes of satting as are otherwise most economical. 
It is not known that all the factors influencing the strength of a raw dry 
clay are definitely determined, but some at least of these factors may 
be recognized. 

Upon evaporating from a clay, the water previously added to pro- 
duce plasticity, the clay particles are drawn closely together, and the 
grains develop a cohesion between each other. By some, this strength 
is thought to be due to an interlocking of the clay grains, while others 
contend that it is due to the cementing power of colloidal matter developed 
by the action of water on clay particles. 

The strength is usually measured by the so-called tensile test using 
a small brickette, having a central cross section of one inch square, 
and widened ends which are caught in the jaws of clamps. An in- 
creasing load is very carefully applied, breaking the brickette at the 
narrower part by a steady pull. For some purposes, this test will 



GEOLOGICAL SURVEY OF OHIO. 73 

probably answer, but in testing a clay for roofing tile purposes it was 
thought that the cross breaking strengtli would give data nearer to 
the actual conditions to which such clays are exposed in practice. The 
following test was devised for this purpose: 

The trial pieces were made from the standard roofing tile clays, 
all of which had previously been carefully ground and screened to pass 
a 20-mesh screen, this size being commonly used commercially. The 
clays were then mixed with water by hand upon a clean table, until 
each clay had been made a little softer than was considered its proper 
working condition. Each'cJay was then made into a large ball-shaped 
lump, containing from 30 to 50 pounds. These balls of clay were wrapped 
in wet burlap and packed in damp boxes, made of plaster of Paris. 
The clay was allowed to remain in the damp boxes for at least 48 hours, 
when each in turn was removed, placed on a wedging block and thor- 
oughly reworked. It was found that in nearly every instance the clay 
had assumed a nice condition; that is, the water added for plasticity 
had become evenly distributed, and the clays had mellowed or tough- 
ened to a very marked degree. 



Fig, 19 — Mueller Auger Machine. 

The trial pieces for the cross breaking tests were made by running the 
different clays through a small auger-machine made by Mueller Bros., 
St. Louis, Missouri, shown in the above illustration. 

The bar was approximately one-half inch thick by six inches wide, 
and this was cut into fourtecn-inch lengths. Kach tile was then care- 
fully cut lengthwise in the center, producing two strips three inches 



74 



BULLETIN ELEVEN 



by fourteen inches by one-half inch. These were placed on boards to 
dry in an open room at ordinary room temperature, up until the time 
of testing, when they were placed in a drying oven, and heated to 
212° Fahrenheit for 24 hours, being removed from the dryer a few at a 
time as needed for testing. They were first allowed to cool to about 
atmospheric temperature. In most of the clays, eight trial pieces 
were used to make this test, while ten were used in a few. 

The object in using the auger-machine to make the trial pieces 
was to eliminate the personal factor in moulding as much as possible. 
In addition, the bar of clay was thus made under actual working con- 
ditions and in the full size, though subsequently cut up. The trial 
pieces were carefully measured by calipers having a Vernier scale, 
correct to the second decimal place. The thickness and width of each 
bar was thus taken. 



Itii^T^a 



Hh 



}i-i- 



Portia/ enc/ e/et/^//or? ,3/fotY/nff 
&t/mfp />? pos/fforf ^f7€? /no/. 




Fig. 20— Cross- Breaking Machine. 



The actual test of breaking the trials was accomplished by the use 
of the apparatus shown in Figure 20. It will be observed from the cut 
that the test piece to be broken was supported upon knife edges, made 
of hard oak, and placed ten inches apart from center to center. A stir- 
rup having a knife edge resting on the bar of clay, and a hook at its 
lower end, was placed midway between the end supports. A pail or 
bucket was then attached to the hook as shown. The actual breaking 



GEOLOGICAL SURVEY OF OHIO. 



75 



load or weight was supplied by water from the tank on the table. A 
small rubber tube was used to eonvev the water from the tank to within 
an inch or so of the pail bottom as shown. Attached to the rubber hose 
was a pinch-cock, which was closed the instant sufficient water had 
been run into the pail to break the piece. By keeping the hand upon the 
pinch-cock constantly, it was possible to shut off the supply almost 
instantly, or at least with only a small factor of error. 

After each breaking test, the pail and its contents was carefully 
weighed, the water returned to the supply tank, and the operation 
repeated. 

Each breaking weight has been calculated into load per square 
inch in the following table : 

TABLE No. 9. 

Results of the Cross-breaking Test as Applied to the Standard Roofing Tile 
Clays. Bars One-half Inch by Three Inches in Cross Section. 

















Designation of 


Load in pounds 


Designation of 


Load in pounds 






clay sample. 


per square inch. 


clay sample. 


per squai e inch. 






A 


6.33 


H 


11.50 






B 


6.41 


I 


6.98 






C 


5.95 


T 


8.78 






D 


4.17 


"K 


7.04 






E 


7.53 


L 


not determ'ed 






F 


5.04 


M 


4.79 






G 


2.76 


N 


9.05 










O 


not determ'ed 





From the table it will be noted that clay H stood the greatest 
load, 11.50 pounds, while clay G was the lowest, only requiring 2.76 
pounds to break it. Cla)' G was extremely brittle or short, and was 
very hard to handle without breaking. Clay D, while much better, 
was still too weak. Care would have to be exercised in workin;^ with 
it. Those clays having a cross-breaking strength of 5 pounds or more 
per square inch were all safe to work with. Clay H would stand very 
rough handling in setting, but this advantage is offset by having a 
higher shrinkage than the other clays. 

Clays of the type of A, B, C and F are good commercial clays, 
in so far as strength of the unburned, dried ware is concerned. 

Figure 21 is a graphic representation of the necessary loads 
to break the various trials. 

Air Shrinkage* — The volume changes of clays are preferably studied 
in two stages, proceeding from dissimilar causes; viz., the drying or air 
shrinkage and the burning shrinkage, Only the former will be 
considered here. 

The water which is added to a clay to make it plastic is lost by 
evaporation, causing a loss of volume. The loss of volume or shrinkage 



76 BULLETIN ELEVEN 

varies greatly with different clays, and with the same clay under dif- 
ferent modes of treatment. The amount that a clay will shrink in 
drying is best expressed in per cents, of the initial length as linear shrink- 
age, or of the initial volume as cubic or volume shrinkage. 



I 



I 



E F O H I J K M N 



Purdy', in a very careful and extensive test on the measurement 
of linear air shrinkage of clays, says that this factor varied as much 
as 1.33 per cent, from the average, and that such data must be wholly 
unreliable. Although extreme care was exercised in preparing and 
handling the test, he says that the large variations in the results were 
a surprise to the operator. 

The volume air shrinkage was found to vary within much more 
reasonable limits, although such variations as 33.8 per cent, were found. 
The reasons given for such errors are charged to the smailness of trial- 
pieces and the personal factor. In view of Purdy's results, both linear 
and cubic shrinkage were carefully measured on the standard roofing- 
tile clays as a possible check, one to the other. 

Linear Air Shrinkage. — Takiog up first the linear air shrinkage; 
The trial-pieces were made by taking the previously prepared and aged 
clay, and passing the same through a one-inch by one-inch die attached 
to a small plunger or piston machine. The elay was fed into the barrel 
of the machine in lumps or balls, packing the chamber as full as 
possible. The plunger was then moved forward by a screw move- 
ment, and as the clay issued from the die it was cut off into four and 
one-half inch lengths. Ten trial pieces of each clay were thus made. 
These bars were placed on metal pallets, lettered, numbered, and stamped 
'Purdy, R. C. Illinois State Geol. Sur., Bull. IX, p. 133. 



GEOLOGICAL SURVEY OF OHIO. 



77 



with a 100 mm. distance marker. To determine the water added for 
plasticity, the trials were weighed upon leaving the die. Then, at in- 
tervals, they were weighed and measured, giving the results in Table 10. 

TABLE No. 10. 

Table showing loss of Water, and Corresponditig Air Shrinkage of the Standard 
Roofing Tile Clays, from Time of Making to Complete Dryness. 



Designation 
of clay. 



' Per cent loss 
o£ water. 



I 



Per cent of 

drying 
shrinkage. 



Designation 
of clay. 



Per cent loss 
of water. 



Per cent of 

dp^ng 
shrinkage. 



B 



^* ^ 



D 



H 



4.19 
7.69 
16.7S 
19.23 
20.75 
20.62 



1.75 
4.50 
5.00 
5.50 
5.50 
5.50 



J 



3.18 


1.50 , 


9.26 


2.75 


15.01 


3.00 


15.97 


3.00 


16.22 


3.00 : 


5.71 


2.00 i! 


13.21 


. 4.50 1 


21.42 


4.50 ' 


23.21 


4.50 


24.28 


4.50 


13.88 


3.50 


20.48 


3.50 


21.52 


3.50 


21.87 


3.50 


6.25 


4.00 


15.97 


6.00 


20.83 


6.00 


21.52 


6.00 


6.94 


4.00 


17.01 


5.00 


21.52 


5.25 


22.22 


5.25 


1.80 


.50 


7.34 


2.00 


13.85 


2.00 


15.66 


2.00 


3.54 


2.00 


5.67 


3.50 


12.05 


6.50 


19.85 


7.00 


22.62 


7.25 


2.00 


1.00 


6.66 


3.25 


10.00 


4.00 


13.66 


4.00 


15.33 


4.25 


16.33 


.4.25 


17.33 


4.25 

1 



K 



M 



X 



O 



6.33 
8.80 
13.73 
20.07 
21.47 
23.94 



6.25 
9 02 
12.50 
17.35 
19.79 
20.48 



1.80 

3.31 

5.92 

6.18 

9.98 

11.43 

13.38 

19.12 

20.56 



1.54 

3.08 

5.27 

9.40 

11.53 

13.58 

17.14 



1.95 

4.02 

5.21 

6.84 

10.28 

12.33 

13.90 

16.90 



2.09 

3.82 

6.42 

7.30 

11.95 

12.48 

13.32 

17.52 

21.90 



2.50 
3.50 
5 50 
6.00 
6.50 
6.50 



3.00 
4.00 
5.00 
5.50 
6.00 
6.00 



1.00 
2.00 
3.50 
4.00 
5.50 
6.00 
6.00 
6.00 
6.00 

.50 
1.50 
3.00 
3.50 
3.50 
3.50 
3.50 



1.00 
2.50 
4.00 
4.00 
4.50 
5.00 
5.00 
5.00 



1.00 
200 
5.00 
4.50 
5.50 
5.50 
5.50 
5.50 
5.50 



78 BULLETIN ELEVEN 

In order to make this mass of data easier to interpret, it has been 
plotted to scale on co-ordinate paper, and the points connected, making 
the curves shown in Figure 22. The irregularity of the periods for tak- 
ing readings and the few readings obtained in the early part of the 
drying tests leave much to b§ desired, but, after all, the curves are of 
assistance in visualizing the data. From these tables and curves, it is 
possible to divide these fifteen clays into two tolerably distinct groups. 

First. Those clays which continue to show a steady shrinkage as 
long as the expulsion of water continues. Samples J, H, K, I and E 
belong here. J is the type, continuing to shrink up to 21.5 water loss 
out of a total water expulsion of 24. 

Second, Those clays which cease or nearly cease shrinking when 50 per 
cent, of the water has been expelled. Samples O, A, F, L, N, M, G, B; 
D and C belong here. is the type, being almost through shrinking 
at 6 per cent, water loss, but continuing to lose water up to 22 per cent. 

The second group may for convenience be divided again into sub- 
group A, those which show a high shrinkage — 5 per cent, or above — as 
0, A, F, N and L, and subgroup B, those which show a low shrinkage — 
4 per cent, or below — as G, B, D, C and M. 

The theory has been long held that the water required to make a 
clay plastic must be in excess of the interstitial or pore space of the clay, 
and that after this open space is filled then further addition of water 
widens the distance between grains of clay, causes them to float and 
move on each other more easily, and by its subsequent removal causes 
the shrinkage of the clay in drying. This theory is borne out by the 
curves shown in Group 2, both in the high and the low sub-groups. But 
in Group 1 we have clays whose behavior does not at all agree with this 
familiar conception of the mechanics of a plastic clay mass. These 
clays become less in volume almost up to the very last of their water 
supply, and if these data can be reproduced and extended in other 
clays, they would call for a remodeling of this old conception. 

It is believed that this method of examining the drying proper- 
ties of clays by plotting the shrinkage vs. loss of water in curve form 
promises to be of practical value. 

For example, take clays of the type of G or D. It can be seen at a 
glance that these clays could be dried easily and safely up to the point 
of their maximum shrinkage. Their loss of water has a relation to the 
shrinkage of four to one or above, while clays like H and K, having a 
relation of the loss of water to shrinkage of about three to one would 
be more difficult to dry. In other words, their rate of drying would 
have to be decreased to about one-half of that required for G and D. 

Again, clays H and K would have to be dried very carefully right 
up to complete dryness, while clays like G and D could have their rate 
of drying forced, from the time at which their shrinkage ceases, up till 
all water is expelled. 



GEOLOGICAL SURVEY OF OHIO. 



79 




/o /* /^ /6 /e eo jajs, j?^ 




6 ^ TO IB 7^ 76 7S 



Fig. 22 — Curves Showing Rate of Shrinkage in Drying. 



80 BULLETIN ELEVEN 

Trial Pieces for Volume SIirinkag;e* — Owing to the die used for the 
linear shrinkage trials being improperly constructed, and requiring too 
much time to produce a perfect bar, it was discarded and a new outfit 
used for the volume trials. This consisted of a cast iron die box having 
a two-inch by two-inch opening extending through it. Closely fitting 
the opening was a piston which was used to compress the clay in the 
mold and then to expel the same. The clay was carefully made into a 
roll that would just enter the opening. The die standing vertically on 
a table, the roll of clay was dropped in, the piston was inserted and then 
pressed down until the clay completely filled the die. Turning the die 
box on its side, the rectangular mass of clay was forced out. This piece, 
approximately two inches by two inches by four inches, was now cut 
into cakes three-fourths inch by two inches by two inches by means of 
a wire cutter. Ten trials were thus made. Finally, each in turn was 
returned to the same die box and firmly repressed, to destroy the rough 
edges and surfaces from the wire cuts. Each trial was at once weighed, 
lettered and marked with a 50 mm. marker. Then all were placed in 
pans of water-free kerosene, where they were allowed to remain twenty- 
four hours. Each trial in turn was then measured for its volume in a 
Seger volumeter. 

The volumeter consists of a glass jar with a capacity of about four 
litres, having a broad mouth and closed with a ground glass stopper. 
Through the center of this stopper is a circular opening, into which fits 
a glass tube, which has an expanded bulb at its upper end. Through 
this bulb and tube the interior of the jar is open to the air. 

At the base of the jar in one side is a glass stop cock, which is con- 
nected to the burette shown to the right of the jar in the cut. The 
burette holds 125 cubic centimeters, and is graduated to tenths of a 
cubic centimeter. The upper end of the burette is expanded into a bulb, 
which acts as a reservoir for the liquid drawn up from the jar by means 
of suction applied to the top of the burette. The glass tube inserted 
in the stopper of the jar has a zero mark placed upon it, just below the 
bulb. At the same level on the burette is a second zero mark. Thus 
the apparatus is standardized by filling the jar until the liquid exactly 
reaches the zero marks. 

To use the volumeter, oil must be used for the unburned trials, 
while water could be used for any substance that will not disinte- 
grate when immersed in it. After the jar has been filled to the 
zero marks, the oil is sucked or drawn out of the jar up into the 
burette and its bulb. When a sufficient quantity has thus been removed 
from the jar, the stop cock in the burette is closed. The glass stopper 
is then removed from the jar, and the trial piece which has been pre- 
viously saturated with oil is lowered into the jar, the stopper replaced, 
the burette stop cock opened, and the oil allowed to run back into the 
iar, care being taken to stop it exactly at the zero mark in the glass 



GEOLOGICAL SUKVEY OF OHIO. 




Fig. 23— Seger Volumeter. 

Stopper. There will remain in the burette, and measured by it, a volume 
of oil in cubic centimeters equal to the volume of the trial piece placed 
in the jar. After the volume has been read off, a portion of the oil is 
again drawn up the burette, the trial piece removed, and a second stan- 
e— G. B. 11. 



82 



BULLETIN ELEVEN 



dardization of the liquid made. Thus the work is carried on. Much 
care must be given to the operating of a volumeter in order to get con- 
sistent data; many small factors creep in to vary results. For instance, 
after the oil has been drawn up into the bulb of the burette, a trial placed 
in the jar, and the oil allowed to flow back, it will be found that unless 
a considerable time is allowed for the oil to drain down the sides of 
the burette, that an error of considerable importance will be made — 
that is, the volume will be underread. Again, much care should be 
used in having the trial pieces free from excess oil upon entering the 
jar and in seeing that the oil is not spattered out or lost upon removing 
the lid. 

For lowering the trials into the jar a little device was used con- 
sisting of a piece of flat sheet iron, so bent that the step formed had its 
center of gravity directly under its vertical part. In the top of the 
piece was a hole, through which the lifter and its charge could be raised 
or lowered into and out of the jar by means of a small hook. The lifter 
must of course be left in the jar while standardizing. 

All of the trial pieces used in this test were prepared as before 
noted, and their volume carefully measured in the volumeter. After 
being removed from the volumeter, they were allowed to air-dry for 
several hours, and then placed in a drying oven and brought to dryness, 
after which they were carefully weighed, measured and allowed to soak 
in oil a second time, this time for a period of 48 hours. The volume of 
each trial piece was again taken, giving the following results based 
upon the average : 

TABLE No. 11. 

Comparing the Volume Shrinkage of the Standard Roofing Tile Clays with 
Their Measured and Calculated Linear Shrinkage and Water Content. 





Sample 


Average 

Initial ^ater 

Content in 

ler Cents. 


Average 

Volume 

Shrinkage in 

Per Cents. 


Average 
Measured Lin- 
ear Shrinkage 
in Per Cents. 


Calculated 

Linear 

Shrinkage in 

Per Cents. 




A 


16.01 


13.47 


3.94 


4.71 




B 


14.23 


7.34 


3.32 


2.51 




C 


20.16 


12.63 


4.90 


4.40 




D 


18.80 


8.60 


3.90 


2.95 




E 


16.80 


12.43 


3.94 


4.33 




F 


19.08 


12.96 


4.03 


4.52 




G 


11.37 


3.09 


1.66 


1.04 




H 


19.83 


19.36 


6.00 


6.92 




I 


14.69 


8.49 


3.96 


2.92 




t 


17.72 
17.47 


17.02 
13.93 


5.98 
4.88 


6.03 

4.88 




L 


16.67 


16.96 


4.88 


6.01 




M 


15.58 


8.25 


3.92 


2.83 




N 


16.13 


9.38 


3.46 


3.23 




O 


18.74 


12.08 


3.82 


4.20 



GEOLOGICAL SURVEY OF OHIO. 83 

The above figures of volume and linear shrinkage, with the per 
cent, of initial water, are taken from the average of ten samples in each 
case. The linear shrinkages given in column 5 were calculated from 
the observed volume shrinkage by the Purdy formula.* 

While the measured and calculated shrinkage do not check each 
other closely, there is a very general similarity in them. 

Much care was taken in obtaining the two kinds of measurements. 
The linear shrinkage marks were cut into the trial pieces by sharp-pointed 
dividers, set to read 50 mm. When the trial pieces were dry, they 
were measured by a Vernier shrinkage scale, which read to the second 
decimal place. The differences in the measured and calculated 
shrinkages no doubt come from the inability of clay bodies to shrink 
perfectly. Structural flaws form inside clay wares, owing to the ina- 
bility of the highly viscous mass to completely obey the laws of a fluid. 
No piece of plastic clay ware can be broken open and found free from 
structural defects. Hence, no formula based on a perfect volume change 
can be expected to agree other than superficially, where it is known 
that the volume change is highly imperfect. 

It will be noted that clays H and J have the highest volume and 
linear shrinkages of the entire list, while clay G has the lowest. These 
same clays have the highest and lowest per cents, of initial water. By 
referring to Table No. 8, it will also be seen that clay H has the greatest 
cross-breaking strength, and clay G the lowest. Thus we can see that in 
this case there is a close relation between the percentage of water re- 
quired for plasticity and the shrinkage and strength of the clay. 

BEHAVIOR IN BURNING. 

The properties which weigh in making one clay more desirable to 
work than another in the burning process are : 

1st. Freedom from a tendency to snap or pop in heating up. 
2nd. Ease of oxidation. 
3rd. Wide vitrification range. 
Nearly any clay can be burnt successfully if sufficient time and 
skill and expense can be brought to bear on it, but the ease with 
which some clays can be burnt and the difficulties which arise with 
others make these properties of very real importance in estimating the 
value of any given sample. 

The properties which are developed in the clay by the burAing 
process — the color, strength, hardness, frost resistance, volume change 
etc. — are really separate from the actual behavior in burning and will 
be considered under a later heading. 

*"If a unit cube shrinks so that each edge is decreased by linear length 'a,' 
then the new length of the edges becomes (1 — a). If the decrease in volume 
of this same cube be represented by 'x,' then the new volume will be (1- x). 
Since the edges of the cube are now (1 — a), its volume can also be represented 
by (1 — a)' hence (1 — a)' is equal to (1 — x), or a = <l — x." (Bull. IX, Illinois 
Geological Survey p. 133.) 



84 BULLETIN ELEVEN 

Snapping^* — This peculiarity is not a very common defect of clay 
wares, but is a serious drawback to a clay when it does occur. The 
clay on heating shatters or flies to pieces explosively, in whole or in 
part, and not only ruins the piece affected, but often does much harm 
to the surrounding pieces — especially if they be glazed and subject to 
easy disfigurement. 

The idea is common that snapping or popping is due wholly to the 
too rapid expulsion of moisture, so that steam is generated faster than 
can escape from the pores of the clay, and, as a consequence, flakes or 
chips of the ware are blown off to vent the interior pressure. Beyond 
doubt such steam explosions do occur, and commonly too. Especially 
in piston-made wares, like sewer-pipe, in which longitudinal laminations 
are extensively produced in the die, the steam seems to collect in these 
cavities and blows off large flakes, and the resultant product is usually 
worthless or nearly so. Any clay will fail from this cause, if its treat- 
ment is conspicuously over-hastened, and time is not afforded for the 
water to peacefully vaporize, but in general those clays which give the 
most trouble are the fat, rich, plastic clays of tight body. Such clays 
manifest a stronger tendency to laminate, or to form layers separated 
by cracks or unbonded zones, and thus help to produce this defect, 
both by hindering the easy escape of steam and affording accumulation 
zones for it to gather in until the danger point is reached. Weak, 
porous, sandy clays are not given either to holding back the steam or 
forming laminations, and hence in such clays steam-popping is at a 
minimum. 

But this form of popping is the easiest to regulate, because its 
causes are understood. Real snapping is not due to this cause. It 
develops in thoroughly dried clay wares and hence cannot be a water 
or steam trouble. Clays affected by it fly to pieces or chip off from the 
surface and give great trouble. In general it is close-bodied, dense 
clays which snap. The cause has never been adequately studied, but 
is probably due to unequal expansion or too rapid heating. In the 
fifteen samples tested for -this report, no snapping occurred in any of 
the trial pieces produced, showing that these clays are not affected. In 
another clay, subsequently tested in the same manner, snapping did 
develop. The likelihood of developing trouble from snapping is greater, 
of course, in laboratory experiments in small kilns than in large kilns 
in commercial work, on account of the tendency to quick heating in 
small kilns. 

Oxidation Behavior* — Clays contain a number of mineral and 
organic constituents, besides the silicate of alumina which constitutes 
the plastic cementing material which gives character to the mass, and 
in burning a large number of different chemical reactions may be occur- 
ring. In general, these reactions are of two sorts — destructive and con- 



GEOLOGICAL SURVEY OF OHIO. 85 

structivo. The former tend to break down the original constituents, 
drive out all of the volatile elements, and bring what is left into a con- 
dition of quiet equilibrium — i. e., a state where further chemical changes 
are not taking place. Only the less volatile substances usually remain 
when the clay has reached this stage, such as silica, alumina, iron, lime, 
magnesia, and the alkalies, and these substances are present partly as 
free oxides, and more largely as silicate compounds, more or less broken 
down from the mineral forms in which they originally existed. 

The second or constructive changes are those occurring in vitrifi- 
cation and fusion, by which the oxides and minerals left in the clay mass 
are brought into, new union by additional heat, and with this new partial 
combination comes a new set of physical properties, differences in 
color, strength, hardness, density, elasticity, etc. 

The first group, or destructive changes, are therefore, seen to be pre- 
liminary or preparatory for the final hardening or vitrification of the 
clay, and no clay can be satisfactorily vitrified until its minerals have 
been brought to a proper condition by this preparatory treatment. The 
preparatory process itself is divided into two stages called dehydration 
and oxidation. The former concerns itself with the expulsion of the 
combined water from the kaolinite and other hydrous minerals of the clay. 
The latter concerns itself with the burning out of the organic bodies, 
such as wood, leaves, grass, roots, peat, lignitic matter, coal graphite, 
bitumen, or oily matter, and with inorganic combustibles like sulphur 
from sulphides of iron and similar minerals, and also with the conver- 
sion of all oxides that are left in the clay mass into the state of equili- 
brium before mentioned, by giving up a part of their oxygen, or taking 
on more of it. 

The dehydration and oxidation reactions are not differentiated from 
each other clearly in the time of their occurrence, but oxidation changes 
usually last the longest, and require a higher temperature to complete 
them, though some parts of the oxidation may begin as early or 
earlier than any of the dehydration changes. 

Clays show a wide difference in behavior in the ease and completeness 
with which they undergo this preparatory treatment. Some clays 
contain almoi^t no oxidizable matter, and are ready to go ahead for 
vitrification as soon as the water is well out of them. Such clays are 
very '*'easy'' to handle. Others are so full of carbon, iron and sulphur 
compounds that they are actually combustible like low-grade fUels. 
Such require the most extreme care, and often specially designed kilns, 
to make it possible to produce marketable wares from them. 

In general, clays show by change of color when they are through the 
oxidation period. The presence of carbon or sulphur is indicated in a 
partially burnt clay by a black or dark discoloration. When this dis- 
appears from the center of the ware, then it is known that these sub- 
stances no longer remain in quantities sufficient to do further harm. At 



86 BULLETIN ELEVEN 

the same time, the iron which up to this time may have been existing 
in unstable forms of blue, green, gray or yellow colors, now takes on the 
usual brick-red tint in common clays. In fire clays, where the iron is 
much less in quantity, the characteristic buff tint is produced. The 
loss of the center discolorations and the assumption of the oxidized 
iron color is evidence that the clay is prepared for vitrification.^ 

While the roofing tile manufacturer is usually little troubled by 
oxidation difficulties in his clay, owing to the extreme thinness of the 
ware and the consequent ease with which oxygen permeates the mass 
and does its work, and also the openness of the setting, by which the 
air secures easy contact with the wares, still it was thought advisable 
to conduct a careful experiment to show the extent to which the standard 
series of roofing tile clays do really offer oxidation difficulties, and thus 
obtain a basis for judging how far oxidation troubles should be allowed 
to weigh against a clay under consideration for this particular industry. 

The cross section of ordinary roofing tiles being so thin, it was 
thought better to mould up the clays into test pieces of much thicker 
cross section, in order to require a longer treatment for oxidation and 
thus form a better opportunity to draw comparisons. All of the stan- 
dard clays were passed through a 20-mesh screen, tempered and aged, 
as described earlier, and seven brickettes of each, two inches by two 
inches by four inches, were then made in the die box before described. 
At the center of each trial, on all four sides, a light indentation was 
made to assist in breaking the brickettes at the desired point after 
drawing from the kiln. The trials were all carefully dried, and were 
then set in a small down-draft test kiln, in such a manner that a com- 
plete set of all of the standard clays could be taken out at a single draw- 
ing. The firing was done by coke, with a large excess of air passing 
through the kiln. To better control the temperature, a pyrometer 
was used. Time and temperature observations were carefully made 
at intervals, and the curve shown in Figure 24 was drawn to indicate 
the progress of the heat treatment. As each draw was made, the 
trials were placed on the floor, and with chisel and hammer they were 
carefully broken apart along the indentation lines. 



*See in this connection: 



Orion, The Role played by Iron in the Burning of Clays, Transactions 
American Ceramic Society, Vol. V, page 377. 

Orion & Grtffin. The Influence of Carbon in the Burning of Clay Wares. 
Bull; 2, National Brick Manufacturers' Association, Indianapolis, 1905. 

Orion & Staler. The Status of Carbon Iron and Sulphur in Clays dur- 
ing the Various Stages of Burning; Bull. 3, National Brick Manufacturers' 
Association, Indianapolis, 1908. 

Jackson & Uopivrod. Trans. North Staffordshire Ceramic Soc. The 
Coloration of Clay Wares. 1902, p. 93. 

Hopwood, A. Trans. English Ceramic Soc. The Changes in Color of 
Clays on Ignition in Clay Ware Kilns, 1903, p. 37. 



GEOLOGICAL SURVEY OP OHIO. 



87 



In Figure No. 25, page 88, it will be observed that an attempt 
has been made to represent graphically the results of the experiment 
on the rate of oxidation of the standard roofing tile clays. The various 
trial pieces were numbered in the order in which they were drawn from 
the kiln. Corresponding numbers are placed at the foot of each column 
in Figure No. 25, as well as the duration of the burn in hours at the 
time of the draw. An effort has been made by shading to represent 
the intensity of the color of the unoxidized cores in the various trial 
pieces. For instance, clays F, I, A, B are shown with areas lightly 
shaded, while clays J, N, E, H are shown black, the shading approach- 
ing the depth of color intended in each case. 



















































































































































_ _ 
























-^— 








^^ 


*^ 




^ oOO 










y^ 














• 








h 

« ^(*» 












/ 


^ 




• 


























/ 




























y 
























































/^9 


^^ 
































i 


i M 


» t 


\ i 


f A 


9 /i 


r? / 


•^ A 


tf h 


9 £ 


^ 1 


l> J 


4 ^^ J^ 



Fig. 24— Time-Temperature Curve, Showing Heat Treatment of Test Pieces. 



Draw No, i. Taken at 10 hours after the beginning of the burn. 
Temperature 565° centigrade. It will be observed in Figure No. 25 
that out of the fifteen clays tested, only one, clay D, was completely 
oxidized at this draw, while clays F, I, A and B had been oxidized to 
a depth of about one-half inch on all sides, the unoxidized area being 
of a faint gray or blue-black color. At the same draw, clays K, M, 0, 
L, G, C, J, and N had oxidized to a depth equal to or greater than F, 
I, A, and B, but the color of the unoxidized area was much darker, 
indicating a much larger amount of material to be oxidized. Clays 
E and H had only oxidized to a very shallow depth, less than one-fourth 
inch on all sides. In both of these cases, the central area was of a solid 
coal-black color. 

Draw A^o. 2, Taken at 12 hours. Temperature 570° C. 

Upon breaking open the trials from this draw, it was found that 
clays F and I had become completely oxidized, while clays A, B, K, 
M, and G had an area of three-fourths inch to one inch in diameter 
still remaining unoxidized. Clays L, C, J and N contained areas of 
one inch 1,0 one and one-half inch in diamecer still unoxidized, and ii\ 



88 



BULLETIN ELEVEN 



clays E and H, the oxidation liad proceodod but about one-eighth iuoh 
furr.her in than it wa.s in Draw No. 1. 



D 




FB 




I m 




A Q O 




BB Q 




Km • 


o 


Mm • 


• 


om • 


• 


LB m 


• 


om m 


• 


cm m 


• 


^m m 


• 


nM m] 


• 


bm m 


m 


ffM m 


e 



o 





• 


• 


• 

• 




• 
• 



Fig. 25 — -Sketch Showing Progressive Oxidation of the Standard Roofing Tile 

Clays at Various Stages of the Burning Process. 

Draw N). j. Taken at 14}4 hours. Temperature 5S7° C. 

Two more clays, A and B, had reached complete oxidation. Clays 
K, M and O only retained a small area unoxidized, about equal to the 
cross section of a lead pencil. In clays L, G, C, J and N, the oxi- 
dation had proceeded slightly less than in trials K, M and O, although 
all showed a marked change from draw No. 2. Clays J and N madQ 
the least gain. In clays K and H, the unoxidized portions had been 
reduced very little, but uniformly. 

Draw Xo. 4. Taken at 15,^4 hours. Temperature 620° C. 



GEOLOGICAL SURVEY OF OHIO. 89 

Two more clays, K and M, were found to have reached complete 
oxidation by the time. of making this draw, while claj's O, L, G and C 
retained but a very small area unoxidized. In clays J and N, the dark 
areas, while still darker than O, L, G and C, had undergone a marked 
decrease in size. The changes in clays E and H were noticeable, but 
small. 

Draiv Xo. 5. Taken at 20^2 hours. Temperature 660° C. 

Under the influence of the slightly increased temperature and the 
increased duration of time, clays O, L and G had reached complete 
oxidation, while N still contained a small area of black core. Clays 
E and H had lost their usual proportion of blaclc ar^a, but still con- 
tained a very dark core about three-fourths inch in diameter. 

Draio No. 6. Taken at 24% hours. Temperature 730° C. 

At this draw, trial-pieces C, J and N still retained a small area of 
core, not much reduced from that of No. 5. In trial pieces E and H, the 
core had onlj'^ been reduced a very little, indicating that the oxidation 
in these clays was progressing very slowly, notwithstanding an increase 
of temperature and a time period of about 4 hours. 

Draw No. 7. Taken at 28 hours. Temperature 605° C. 

Observations at this draw showed. trial pieces C and J to be com- 
plete in their oxidation, while the three clays N, E and H were still 
showing unoxidized areas about the size of a five-cent piece. Unfor- 
tunately the work could not be carried further, owing to the fact that 
only seven sets of trial pieces had been placed in the kiln. It had been 
thought that all of the clays would be completely oxidized at the end 
of a 24-hour period, and that seven draws would prove sufficient, but 
such was not the case. In order to complete the chart, the three <?lays 
N, E and H have been plotted as they would have appeared if the same 
rate of decrease of core had been maintained from there on to the finish 
as had been shown in the seven first draws. Using this same rate, 
and 4-hour intervals, clay N would have been completely oxidized at 
the end of 36 hours, w^hile clays E and H would have taken 40 hours, 
provided the temj^erature had been held about constant. 

Significance of this data. — Of the fifteen clays studied, only one 
clay, D, was found to be entirely free from unoxidized material at the 
end of 10 hours. 

This clay in its natural condition is a deep-red or chocolate-colored 
shale, the color indicating that the iron present in the clay had been 
deposited in the ferric form, and that no carbon or reducing materials 
were deposited vrith it, to serve as a means of reducing it later. 

In so far as oxidation is concerned, clay D, if made into roofing 
tiles, could be set tightly in the kiln, and fired fast, with no danger. 
It is the only clay of the series of which this could be said. 

Clay A was oxidized in 12 hours. It is quite possible that the 
actual amount of material to be oxidized in this clay is as great as in 



90 BULLETIN ELEVEN 

N, E and H, but the nature of the material is different. It is a shale 
whose structure is broken up by a high content of sandy material, 
making the body so porous that oxygen can readily permeate the tiles, 
and the carbonic acid generated can escape. N and H, on the other 
hand, are fine-grained alluvial deposits, and E a close-grained glacial 
clay. The fineness of grain in the three latter clays prevents the free 
permeation of the body by the oxygen, hence the oxidation period of 
the burn must be extended to properly provide for this. 

Notwithstanding the fact that clay A was seemingly oxidized easily, 
it is known from actual use of this clay in the manufacture of shingle tiles 
that it gives trouble in the matter of center marks and black core, unless 
the burn progresses very slowly. Ten to tw^elve days are used in the 
proper burning of the tiles. The mode of setting the shingle tiles made 
from this clay is very dense and close and anything but conducive to 
easy oxidation or imccessful, rapid burning. 

While it might appear, from the oxidation trials show-n in this 
work, that much trouble might be expected in the burning of roofing 
tiles from such clays, such is not really the case. The fact that roofing 
tiles are thin wares, and that the shape of all tiles, excepting flat shingles, 
is such that tight sotting is impossible, largely assists in the rapid oxi- 
dation of the tiles. The temperature at which this t^st was executed 
was also lower than necessary for safe oxidation, and the results were 
slower than in commercial practice on this account. However, oxida- 
tion at temperatures: above 800° to 850° Centigrade has been shown by 
Orton* to be a common cause of different colored center-marks, even 
though all carbon and sulphur are finally expelled from the ware. In 
actui^l kiln firing, the oxidation begins at 350° or 400° and progresses 
till about 900**, at which point it seldom continues to make much head- 
way. But in large kilns passing from 400° to 900° it usually stands for 
considerable time-periods, 24 to 48 hours or more, and this test shows 
that even in wares two inches square, not more than 40 hours would 
be required. 

It was not the purpose in making this test to try to establish a 
definite time for the oxidation period of any clay. In a search of ceramic 
literature for data, nothing could be found that would enable one to 
make safe conclusions upon the relative speed of oxidation in trial 
pieces and full-sized wares, and no attempt has been made to do so in 
this discussion. It is clear, however, from the w-ork done, that clays 
like E and H will take very much more time than A or B, and that 
roofing tiles, while easy to oxidize as a class, are nevertheless not at 
all exempt from troubles in this connection. 

An interesting point has been brought out in this work, in the 
study of the three clays, I, K and J taken singly, and the mixture L, 
formed by their blend. It will be observed that I shows very little 

*See references cited on page 86. 



GEOLOGICAL SURVEY OF OHIO. 91 

trouble in oxidizing, K a little more, and J very much more: in fact, 
the latter clay would be considered bad. The mixture of these three 
clays in the proportions used by the company furnishing them is an 
improvement over J, but is worse than K alone, and very much worse 
than I, which by itself would be considered as a good or easy clay to 
oxidize. This company is thus taking a very easily oxidizable clay and 
by adding others to it is greatly increasing the danger of getting: black- 
cored and center-marked ware. So far as oxidation alone is considered, 
it would be better to discard J entirely, and K if possible. 

VITRinCATION RANGE. 

General Discussion* — As explained under oxidation behavior, the 
changes occurring in the second part of the burn are constructive 
in nature, as a body is produced having physical properties entirely 
different from those of the original material as a whole or of its compo- 
nent minerals. The burned clay is a partially fused silicate mass — the 
extent to which the fusion has gone depending on the length and tem- 
perature of the firing, the mineral mixture present, the fineness of grain 
of these minerals, the completeness of their oxidation treatment, and 
many other factors. 

All clays, in producing marlcetable goods, must pass through some 
of this constructive heat work — how much, depends on the kind of prod- 
uct sought. But while practically all clays must undergo such a change, 
the rate at which the change takes place varies very greatly and con- 
stitutes one of the important criteria in deciding on the suitability of 
clays for use. The difference between clays in this respect ranges from 
those which harden, shrink, and reach their best structure interval 
of 50° centigrade in a few hours' time, to others which require 
300° or even 400° centigrade and several days' time to bring about 
the desired degree of combination. Without going, at this place, into 
any discussion of the causes of these wide differences, it is desired to 
know what the fusion habit of each of the standard series of roofing-tile 
clays is, with a view to interpreting the suitability of other clays for 
this purpose. 

A wide or gradual vitrification range has usually been consid- 
ered as of more importance for roofing tiles than for most clay products, 
because quick or sudden vitrification is usually associated with rapid 
and excessive changes in volume, with warpage and deformation, with 
rolling or falling over in the kiln, etc., and these difficulties are all e^tra 
severe on wares of large area and thin cross section, like roofing tile. 

The determination of the vitrification range of a clay can most 
conveniently be done by firing a series of test pieces of suitable shape 
and size through a series of increasing temperatures, withdrawing one 
or more at each successive temperature stage, and measuring their 
various resultant physical properties. By the progressive change in 
these properties, especially in the color, hardness, porosity, specific 



92 



BULLETIN ELEVEN 



gravity, and shrinkage, the progress of the fusion reactions may be ap- 
proximated. 

It will at once be appreciated that a thorough study of the vit- 
rification range involves or constitutes a thorough study of the final 
physical properties which the clay takes on by burning. These various 
properties, such as hardness, porosity, specific gravity, strength, color 
etc., are inherent properties of the clay, or latent within it, and they 
furnish a large share of the evidence in deciding the fitness of the clay 
for any purpose. So that we wish to know, not only the rate at which 
these properties develop in burning and the temperature range needed 
to draw them out, but we also need to know what the final status of the 
burnt clay is in each of these various respects. For instance, a clay 
may be shown to have a wide and perfectly satisfactory vitrification 
range, but its hardness, strength, color, etc., may be wholly unsatis- 
factory from the standpoint of producing a commercial product not- 
withstanding. 

Therefore, in the following studies made on the test pieces drawn 
progressively from the kiln as the temperature rose, the two points 
of view will be preserved and considered separately. 

The trial pieces chosen for burning for this test were the same 
as had been used in determining the drying shrinkage, viz., bars one 
inch by one inch by four and one-half inches, made on a small hand- 
power plunger machine. There were ten trial pieces of each clay, 
carefully marked with the sample letter, and numbered 1 to 10, inclu- 
sive. Each bar was also stamped with marks one hundred millimeters 
apart on the plastic clay; these marks came closer together as the clay 
shrank. In setting these trial pieces for burning, the pieces marked 
No. 1 of each clay were placed together, the No. 2's and each following 
number being similarly assembled. Each lot was placed in a conven- 
ient position for drawing. The firing w^as done in a Caulkin's Reve- 
elation kiln, fired by natural gas. With each lot of trial pieces was 
placed a standard pyrometric cone at the fall of which it was desired 
to draw the lot, as follows: 



No. 


1 


.. . .Cone 010 


No. 


6.. .. 


. . . .Cone 1 


No. 


2.. .. 


.. ..Cone 08 


No. 


7.. .. 


Cone 2 


No. 


3 . . . . 


.. . .Cone 06 


No. 


8.. .. 


. . . .Cone 3 


No. 


4.. .. 


.. ..Cone 04 


No. 


9 


.". . .Cone 4 


No. 


5 


Cone 02 


No. 


10. .. 


. . . .Cone 5 



Thus, when cone 010 melted, all of the trial pieces No. 1 were drawn; 
at cone 08 all of the trial pieces No. 2, and so on. To prevent the trial 
pieces from cracking by cooling suddenly in the air, and to better develop 
the color, a small up-draft kiln standing near the Caulkin's kiln was fired 
up to a good red heat and kept in that condition. The trial pieces as 
drawn from the test-kiln at the specified cone-temperatures were quickly 
transferred to the up-draft kiln. When the entire ten lots had been 



GEOLOGICAL SURA^EY OF OHIO. 93 

transferred, the kil^ was allowed to cool gradually down to the atmos- 
pheric temperature. This precaution is highly necessary, if a normal 
color or strength is| to be obtained. 

On these ten lots of trial pieces, the following properties were studied 
and measured: 

1 — -Color. 4 — 'Specific gravity. 

2 — Hardness. 5 — Shrinkage. 

3 — Porosity. 6 — Warpage and deformation. 

Colon — A good, clean, attractive color is a sine qua non with a 
successful roofing tile. If the material does not burn to a good, clean 
color in itself, the use of a slip of clay or engobe, or some body-colorant, 
must be used. 

In this country at the present time, only one natural color is really 
available for roofing tiles, and that is red. From time to time in the 
past years, a few tiles have been made up from buff burning-clays, 
but the demand for them has been very meager, and their manufac- 
ture soon abandoned. 

Of twelve plants inspected in 1908, eight were producing tiles 
of good red color from natural clays or shales, without the use of slips, 
engobes, or admixed mineral colors. The ninth and tenth plants were 
using a red-burning slip-clay to mask the poor color obtained from the 
raw material in use. 

The eleventh plant was using a slip clay, but with a very different 
object in view^ Their raw material in itself burns to a very nice red 
color, but, according to the statement of those in charge, it is rough 
and pimply. The slip is used to improve the surface finish of the tiles, 
so that they will remain bright and clean after being put in position 
on the roof. The above claim is probably well founded, in their par- 
ticular case at least, for the following reasons: 

The tiles at this plant are pressed on plaster dies. In the nature 
of the case it is impossible to keep the surface of a plaster die in perfect 
condition. It soon becomes badly pitted with minute pores or open 
cells, so that the tiles made upon it receive the reverse impression of 
the pitted die surface, producing very rough, pimpled surfaces. 

If such tiles are soft or medium burned, they will, when placed 
upon the roof, very easily catch dust and dirt, becoming black and 
begrimed within a very short time. Had these same tiles been 
coated with a good slip, their roughness would have been largely oblit- 
erated by the slip filling up the minute cavities on the surface of the tiles. 

In the burning at the above plant it is the practice to stop at a 
point considerabl}' below complete vitrification, or in other words to 
leave the tiles still quite porous. Hence, upon placing them upon the 
roof, it would be natural to expect them to take up much dirt and become 
badly discolored. Thus, it is possible, by using a slip clay which vit- 



94 BULLETIN ELEVEN 

rifles at an early period, to coat the tile-body with a vitrified covering, 
which will act much like a glaze. The product, instead of becoming 
weather beaten and dirty, will remain bright and clean by being washed 
with each rain. 

If the above clay would stand a higher degree of vitrification than 
is at present given it, then the slipping of the tile would no longer be 
justifiable, owing to the extra cost and the loss by breakage during the 
operation. Should it be found that the clay, upon a higher vitrification, 
deformed very badly, then the present procedure of low-temperature 
burning, with the use of a good perfect-fitting slip clay, would be jus- 
tified as the best method of handling a troublesome clay. 

At the twelfth plant, a very different method is pursued to improve 
or change the color of the tile for special orders. A few per cent, of 
mineral-red (oxide of iron) is added to the clay as it is being pugged, 
thus mixing the colorant through and through the clay. 

While the addition of the oxide darkens the natural color of the 
clay very materially, it was hard to see where it had improved the natural 
red color. It gave a dull or faded appearance to the tile thus treated. 
It has been repeatedly demonstrated, practically and experimentally, 
that it is impossible to obtain good, red colors by doctoring the clay 
with a free oxide of iron. This instance merely adds one more to the 
list of failures. 

In taking up the study of the colors produced in this research it 
must be borne in mind that it is impossible to make any clay give its best 
color, when fired in small test-kilns, and cooled rapidly. From a pre- 
vious knowledge of the colors obtained commercially from each of the 
standard clays tested, it was observed that the colors obtained with 
test-kiln burns check those obtained in the regular way very closely, 
with the exception that the colors are not so bright or clear. 

While the terms used to characterize the various shades used in 
describing these results have a wide latitude, it has heen the endeavor 
to use them consistently in the series. These data have been ar- 
ranged in Table 12, pages 95, 96, 97, 98, 99 and 100. It has also been 
thought worth while to include a column giving the percentage poros- 
ity of each trial piece in order to. better associate the colors developed 
with the progress of the vitrification reaction. 

Additional Color Trial. — A further study on the color of the various 
clays has been taken from the warpage trial pieces. These trial pieces 
were burned in a coke-fired kiln, under conditions which would more 
nearly approach the commercial than those of the vitrification test burn, 
in which the firing was by gas and the trial pieces were drawn from the 
kiln at the cone indicated. Although immediately transferred to a 
hot kiln for gradual cooling, still such conditions are not conducive to 
the production of the best colors which a clay is able to produce. The 



GEOLOGICAL SURVEY OF OHIO. 



95 



TABLE No. 12. 
Color Studies on Standard Roofing Tile Clays. 

CLAY A 



Drawn 
at Cone. 



Colots Pound on Cooling:. 



Percentage 
Porosity. 



010 
08 
06 
04 
02 
1 

o 

it 

3 

4 
5 



Light yellow-red 

Slightly darker 

Slightly darker than at cone 08 

Deep red — -A commercial color 

Much darker red — -A commercial color 

Very dark red — -A commercial color 

Very dark red, bordering on brown 

Chocolate brown 

Chocolate brown (dark) 

Blue black 

This clay gives its best color range from cone 04 to 02. 



29.53 

25.77 

18.11 

11.52 

7.48 

4.95 

3.00 

2.51 

1.08 

1.25 



CLAY B, 



010 Very light yellowish red 

08 Slightly darker red 

06 Light red —A commercial color 

04 Better red than 06 - -A commercial color 

02 Same as 04 — A commercial color 

1 About two shades darker red — A commercial color . . 

2 Dark red brown 

3 I Chocolate brown 

4 ■ Dark chocolate brown 

5 Blue black 

This clay gives its best color range from cones 04 to 1. 



31.07 
31.12 
26.80 
25.76 
26.15 
21.05 
19.29 
12.57 
14.04 
3.12 



CLAY C. 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



Salmon-yellow 

Slightly darker 

Same 

Much darker, through still a light red 

Very good red— A commercial color 

Dark red —A commercial color 

Very dark red -A commercial color 

Chocolate brown (light) —A commercial color 

Chocolate brown (dark) 

Bluish brown 

This clay gives its best color range from cone 02 to 1 



35.94 

35.02 

32.45 

17.00 

14.30 

7.41 

5.22 

4.0? 

1.10 



96 



BULLETIN ELEVEN 



TABLE No. 12— Continued. 
Color Studies on Standard Roofing Tile Clays. 

CLAY D. 



Drawn 
at Cone. 



Colors Pound on Cooling. 



010 Light red 

08 Same 

06 Yellowish red 

04 Much darker red — 'A commercial color 

02 Cherry red — rA commercial color 

1 Dark brownish red — A commercial color 

2 Darker brownish red — A commercial color 

3 Very dark brown-red — A commercial color 

4 Bluish brown 

5 Green 

This clay gives its best color range from cones 04 to 02. 



Percentage 
Porosity. 



32,85 

32.03 

33.29 

24.59 

13.04 

12.62 

10.12 

2.62 

0.74 

0.80 



CLAY E, 



010 Light pinkish red 

08 Very light salmon 

06 Same 

04 Same 

02 Same 

1 Buff specks in a matrix of reddish buff .....' 

2 Same 

3 Buff specks in a matrix of brown 

4 Bluish or gray 

5 Same 

There were no commercial colors developed. 
This clay would have to be slipped. 



38.42 

39.87 

39.34 

41.67 

40.10 

12.50 

26.24 

1.90 

2.72 

1.60 



CLAY F. 



010 Light pinkish red 

08 Somewhat darker, though still too light 

06 Same 

04 Light red, rather yellowish 

02 Same 

1 Dark brown 

2 Dark brown 

3 Very dark brown 

4 Bluish 

5 Same 

The nearest approach to commercial colors are obtained 
at cones 04 to 02. These colors are not good when 
compared to the standard tiles on the market. This 
clay should be slipped. 



33.99 

31.83 

33.48 

23.65 

24.61 

12.08 

16.83 

2.93 

0.60 

1.24 



GEOLOGICAL SURVEY OF OHIO. 



97 



TABLE No. 12— Continued. 
Color Studies on Standard Roofing Tile Clays. 

CLAY G. 



Drawn 
at Cone. 



Colors Found on Cooling. 



Percentage 
Porosity. 



010 Very light red, almost buff 

08 Same 

06 Much darker red 

04 A shade darker, much better — A commercial color. 

02 Same — -A commercial color 

1 Dark red — A commercial color 

2 Dark red-brown 

3 Same 

4 Same 

5 Dark brown , 

This clay gave its best color range at cones 04-02. 



28.31 

27.73 

19.03 

16.19 

16.69 

8.22 

9.10 

8.77 

8.42 

7.82 



CLAY H. 



010 Light brick red 

08 Same 

06 Same 

04 Much darker red— A commercial color 

02 Same — A commercial color 

1 Chocolate-red (light) — A commercial color , 

2 Chocolate-red (dark) — A commercial color , 

3 Very dark chocolate , 

4 Blue 

5 Same 

This clay gave its best color range at cone 04-02. 



30.76 

24.88 

29.94 

24.95 

25.37 

8.05 

16.20 

1.65 

2.56 

1.97 



CLAY I. 



010 Light yellowish red 

08 Same, though a little deeper 

06 Poor red with yellow specks 

04 Same 

02 Same 

1 Darker, poor color, yellow specks 

2 Chocolate matrix, yellow specks 

3 Same 

4 Same 

5 Nearly black matrix, yellow specks 

At no point does this clay show a good color. 
It is best at cone 08. 



33.04 
33.33 
32.10 
32.17 
32.10 
29.62 
23.88 
17.94 
15.32 
0.52 



7— G. E. 11, 



98 



BULLETIN ELEVEN 



Drawn 
at Cone. 



TABLE No. 12— Continued. 
Color Studies on Standard Roofing Tile Clays. 

CLAY J. 



Colors Pound on Cooling 



Percentage 
Porosity. 



010 

08 

06 

04 

02 

1 

2 

3 

4 



Very light "pink tinted buff 

Same 

Light yellowish brown or tan 

Same 

Same 

Same 

Olive green brown or tan 

Same 

Same 

Light tan color 

There were no good colors developed by this clay 
It would require slipping. 



24.55 
22.98 
11.22 
9.30 
9.15 
7.41 
7.17 
7.40 
7.88 
9.21 



CLAY K. 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



Yellowish red. Not commercial 

Darker yellowish red. Not commercial 

Much darker red. Commercial 

Deep red. Commercial .* 

Deep red. Some flash. Commercial . . 

Same 

Same 

O verfired 

Overfired 

Overfired 



17.53 
14.48 
8.24 
5.77 
1.71 
0.65 
0.80 



CLAY L. 



010 

08 

06 

04 

02 

1 

2 

3 

4 



Light brick red 

A shade darker, but still a poor red 

Improved but still vellowish red — -A commercial color . 
Darker red, but dull or dead — A commercial color . . . . 

Same — A commercial color 

A very little darker — A commercial color 

Chocolate-brown, poor color 

Same, but darker 

Melted 

Melted 

While there are a number of colors in this set which are 
reported as commercial, they are not very good, hav- 
ing too much of a yellow tint. Clay L is the mixture 
of clays I, J and K, as used in actual tile manufacture. 



27.26 
24.82 
22.59 
18.35 
15.50 
15.63 
12.76 
10.55 
5.20 
4.45 



GEOLOGICAL SURVEY OF OHIO. 



99 



TABLE No. 12— Concluded. 
Color Studies on Standard Roofing Tile Clays. 

CLAY M. 



Drawn 
at Cone. 



Colors Found on Cooling 



Percentage 
Porosity. 



010 Very light brick red • 29.88 

08 Light brick red ' 29.42 

06 Much deeper red — -A commercial color , 28.49 

04 Same — -A commercial color 28.73 

02 A shade darker — A commercial color 27.74 

1 Much deeper red, rather dull — A commercial color 21.73 

2 Chocolate-brown 10.73 

3 Same ^ 3.66 

4 A very little darker 3.10 

5 Same, but dead color 0.51 

This clay gives its best color at cones 06-02. 



CLAY N. 



010 Very light red 37.12 

08 Same 38.25 

06 Gray buff 37.64 

04 Same ' 37.20 

02 Same 36.42 

1 Darker gray 18.25 

2 Same 17.86 

3 Dark gray 5.68 

4 Same 21.04 

5 Yellow-brown (trial melted) 1.01 

There were no commercial colors in this set of trials. A 
slip clay would have to be used. 



CLAY O. 



010 Light salmon yellow 

08 Same 

06 Slightly darker 

04 A little darker red 

02 Medium red color. A commercial grade 

1 Drak red color. A commercial grade 

2 Same. A commercial g^ade 

3 Chocolate-red. Almost too dark 

4 Same 

5 Blue 



27.31 

32.23 

29.04 

22.85 

20.04 

8.84 

11.74 

7.31 

3.92 

5.35 



100 BULLETIN ELEVEN 

trial pieces about to be studied were burned and cooled in the same kiln, 
hence giving better conditions for a normal color. 

Clays A and B give their best commercial colors between cones 07 
and 04. 

Clays C gave its* best colors at a little higher temperature, namely, 
cones 04 to 01. This clay scummed badly. 

Clay D produced its best color at cones 04 to 01, though a fair light 
red is obtained ^t cones 09 to 07. 

Clay E produced nothing but buff-colored trials, due to the lime 
present in the clay. These trials also show considerable popping from 
limestone. 

Clay F gave its best red at cone 07, though the color is poor. All 
trial pieces of this clay were covered with scum or wiiitewash. 

Clay G has a range of good color extending from cones 07 to 01, with 
.04 as the best point. 

Clay H produces its best colpr from cones 07 to 04, with 07 as the 
best color. This clay developed numerous limestone pops, which 
would be strongly against it commercially. 

Clay I is fairly good in color from cone 07 to 01, with trial pieces at 
cone 07 as the best. 

Clay J did not produce any good colors, and furthermore the trial 
pieces were all coated with a scum. 

Clay K in this burn has given commercial colors from cones 09 to 04, 
with the 07 and 04 trial pieces the best. 

Clay M gives good commercial colors at cones 07 to 01, but is badly 
discolored with scum. 

Clay N is pink at cone 09, but all the balance of the trial pieces are 
buff, due to its large lime content. These trial pieces are, in addition 
to their poor color, scummed and linie-poppcd. 

Summing up the results of the entire series, clays A, B, C, D, G and 
M have given the best results. Clays H, K and I have given fairly 
good results, the colors being too light a red, or yellowish. Clays E, 
F and N would have to be given a coat of slip clay in order to make 
them commercial. 

A closer grading of the colors obtained in this work would give first 
place to clays A, B and D. 

From the foregoing, Table No. 13 has been abstracted. 






• • » * 



GEOLOGICAL SURVEY OF OHIO. 



101 



TABLE No. 13. 
Summary of Color Studies on the Standard Roofing Tile Clays. 



Designation 
of Clay. 



Color Range. 



A 
B 
C 
D 
£ 



G 
H 
I 

k 

L 
M 

N 
O 



Deep red, commercial grade — Cone 04-1. 

Fine red, commercial grade — Cone 06-1. 

Good red, commercial grade — Cone 02-3. 

Good red, commercial grade — Cone 04-3. 

Pink, salmon, buff, brown and blue-gray. Full of specks. Re- 
quires slip. 

Pink, light red, brown and blue, with non-commercial red. Re- 
quires slip. 

Good red, commercial grade — Cone 04 to 1. 

Good red, commercial grade — Cone 04-2. 

Yellowish red, poor red, chocolate and black. Not a good com- 
mercial grade. Requires slip. 

Pinkish, bufi, tan, brown and olive green. Would require slip. 

Good red, commercial grade — Cone 06-2. 

Poor lifeless red, barely commercial — -Cone 06-1. 

Good red, commercial grade— Cone 06-1. 

Light red, buff, gray and yellow-brown. Would require slipping. 

GQod red, commercial grade — Cone 02-2. 



It is somewhat astonishing to find that of twelve roofing tile plants, 
only eight were found to be working on good, clean, handsome, red- 
burning material. Three were working calcareous clays, which pass 
through a long cycle of color changes, without at any stage making a 
commercial red, and one plant mixes a clay of good, red-burning color, 
with two others, neither of which can pass muster, and the mixture 
resulting is a poor, lifeless, barely commercial red. 

This is only another illustration of a fact well known in the clay 
industry, viz., that many plants are started by persons of little or no 
experience, and without expert advice, and after making heavy invest- 
ments they find their clays unsuitable. Such concerns usually fail for 
their first projectors, but after one or more forced sales, at constantly re- 
duced valuations, they ultimately fall into capable hands and are op- 
erated. The handicap of a poor or mediocre material remains, however, 
and is a constant bar to a really high grade product, or large financial 
success. 



102 



BULLETIN ELEVEN 



G>Iof Rang:e vs. Vitrification Rang^e* — A study of the vitrification 
range, as disclosed by the color changes,. gives the following data: 

TABLE No. 14. 
Comparison Between Color Range and Vitrification Range. 



Designa- 
tion of 
Clay. 


• 




Period of over- 


Point at which 




End of 
immaturity. 


Period of 
maturity. 


maturity of 

color. Body 

still sound. 


color goes 

black, and 

body fails also. 


Remarks. 

• 


A 


Cone 06 . . 


Cone 04-1. 


Cone 2-4. 


Cone 5. . . 


A fairiy wide range. 


B 


Cone 08 . . 


Cone 06-1. 


Cone 2-4. 


Cone 5. . . 


A wide range. 


C 


Cone 04 . . 


Cone 02-3. 


Cone 4 . . . 


Cone 5 . . . 


A good range. 


D 


Cone 06 . . 


Cone 04-3. 


Cone 4 . . . 


Cone 5. . . 


A good range. 


E 


Cone 02 . . 


Cone 1-3 . 


Cone 4 . . . 


(Not 

reached 


Narrow range. 










F 


Cone 06 . . 


Cone 04-02 


Cone 1 . . . 


Cone 4 . . . 


Narrow range. 


G 


Cone 06 . . 


Cone 04-1 . 


Cone 2-5. 


/Not 

\ reached 


A faidy wide range. 


H 


Cone 06 . . 


Cone 04-2 . 


Cone 3 . . . 


Cone 4. . . 


A good range. 


I 


Cone 010. 


Cone 08 . . . 


Cone 1-4. 


Cone 5. . . 


A wide range. 


i 


Cone 08 . . 


Cone 06-1. 


Cone 2-4 . Cone 5 . . . 


A wide range. 


Cone 08 . . 
Cone OS . . 


Cone 06-2 . 
Cone 06-1 . 




Cone 3. . . 
Cone 4 . . . 


A wide range. 


L 


Cone 2-3 


A good range. 


M 


Cone 07. . 


Cone 06 1 . 


Cone 2-5. 


[Nrt 

\ reached 


A wide range. 


K 


Cone 08 . . 


Cone 0(>-3 . 


Cone 3 4. 


Cone 5 . . . 


A wide range. 


C) 


Cone 04 . . 


Cone 02-2. 


Cone 3-4 


Cone 5 . . . 


Fair ranee 



The foregoing table gives an illuminating view of roofing tile clays, 
and their variations, and enables us to fix a sort of tentative type for 
the group. So far as color changes are competent to decide, the type 
dav is as follows: 



TABLE No. 15. 



Color Scale of Typical Roofing Clay. 



TINTS. 



RanRe in 
Cones. 



Immature and light red colors — Up to Cone 06 

Commercial-red Color Range — Cone 05 to Cone 1 

Overmature Colors, red or brown, with body still sound — Cone 2 

to Cone 4 

Blue or Black Colors, with failure of body as well — Cone 5 and 

above 



5 Cones 
3 Cones 



The behavior of the four undesirable clays (not considering I, J, 
and K, which are not used individually in any plant and which appear 
in their proper proportions in Sample L) is difficult to summarize, because 



GEOLOGICAL SURVEY OF OHIO. 103 

they fail in a variety of ways. The foundation of the trouble of all, 
however, is the presence of enough lime to destroy or injure the red 
color. 

Hardness* — The idea of hardness in the minds of most clay workers is 
associated with other concurrent physical properties which, strictly 
speaking, are not the. same thing, though intimately related. The 
property of physical strength is involved in this common conception, 
and also the factor of toughness or brittleness. A clay worker in speak- 
ing of a tile would call it *'too hard,'' without really meaning that the 
hardness itself is undesirable, but merelv that its hardness leads him 
to expect it to be too brittle, and it is this quality he has in mind in 
condemning it. 

Toughness, or its converse, brittleness, is a property not easily 
measured, except by rough comparative tests, such as the rattler test. 
As roofing tiles are never subjected in actual use to any influences tend- 
ing to wear them out by friction or grinding, nor normally to impacts 
or blows, the application of the rattler t^st to this ware seems very 
foreign and inappropriate. Tests for hardness, as distinct from tough- 
ness or ability to resist blows, based on grinding the ware away by an 
abrasive plate or disc, under fixed conditions of pressure, lubrication 
with water, etc., have been proposed and carried out a few times by 
various investigators, but no standardized form of this test has come 
into acceptance. 

The simplest, oldest and most universally practiced gauge of hard- 
ness is the cutting test — a mode so crude as to be practically impossible 
to standardize it, but so simple that, for any one person, its findings soon 
become satisfactory and convincing to himself. Nothing is required 
but a piece of hard steel, a knife or file, or similar tool, ground to a sharp 
bat not thin edge. A triangular file, with all three surfaces ground 
into planes, makes the best tool. With this steel tempered as hard as 
it can be gotten, a man can soon gauge hardness in burnt clay wares, in 
terms that are not translatable into figures, but which are nevertheless 
satisfactory. 

The test as carried out in this work was done by taking a sharp 
piece of file steel in the hand, as one would hold a glass cutter. Then 
with varying degrees of pressure from the hand, the tiles were easily 
scratched, barely scratched, or not scratched at all, or the steel left a 
blue metallic mark on the tile's surface. In the latter case, the tiles 
were classified as l^eing harder than steel. Other trial pieces that 
could not be scratched, but failed to give a blue steel mark, were classi- 
fied as steel-hard. After a little practice, these gradations could ])e 
determined without much difficulty. 



104 



BULLETIN ELEVEN 



In the following table, No. 16, is shown the data concerning the 
hardness of a series of samples of commercial roofiing tiles. In con- 
nection with the hardness, the percentage absorption is also shown: 

TABLE No. 16. 
Showing the Hardness of Some Commercial Tiles. 



Designation 
of Sample. 


Description of Resistance to Cutting. 


Percentage 
Character of Fracture. Absorption in 

1 48 Hours. 


A-1 


Difficult to scratch 


Stony 


12.13 


A-2 


Difficult to scratch 


Stony 


13.89 








B-1 
B-2 


Very difficult to scratch 

Easilv scratched 


Stony 

Porous and stony 
Stony 


6.22 
20.03 


B-3 


Very difficult to scratch 

Easily scratched 


8.43 


B-4 


Porous and stony 


20.63 








C-1 


Easily scratched 

Easily scratched 


Stony 


17.72 


C-2 


Stony 


13.35 


« 






D-1 


Very difficult to scratch 

Eoual to steel 


Stony 


5.82 


D-2 


Semi-vitreous . . . 


3.26 








E-1 


Very difficult to scratch 


Stony 


5.92 








F-1 


Harder than steel 


Vitreous 

Semi- vitreous . . 


0.80 


F-2 


Eaual to steel 


2.24 








G-1 


Equal to steel (Buff tile) 

Harder than steel 


Stony 


2.31 


G-2 


Stony 


1.73 










H-1 


Equal to steel (Buff tile) 


Stony 


7.61 









In the following table, No. 17, pages 105-108, are shown the data 
on hardness as obtained from the experiments made on the standard 
roofing tile clays in the laboratory. They do not represent commer- 
cial wares: 



GEOLOGICAL SURVEY OF OHIO. 



105 



TABLE No. 17. 

Showing Comparative Hardness of Trial-pieces of the Standard Roofing Tile 

Clays. 



CLAY A. 



Designa - / 
tion of 
Trial- 
piece. 



Description of Resistance to Cutting. 



Temper- 
ature 
in Cones, 



Character of Fracture. 



Percent- 
age 
Porosity. 



1 
2 
3 
4 
5 
6 
7 
S 
9 
10 



Easily scratched 

Slightly harder than A-1 

Slightly harder than A-2 

Equal to steel 

Harder thaSstd}Best colors. 

Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel (overfired) . 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



Open, stony . 
Dry, stony . . 
Dry, stony . . 
Semi-vitreous 
Semi- vitreous 
Semi -vitreous 
Semi-vitreous 
Semi-vitreous 
Semi-vitreous 
Stony 



29.53 

25.77 

18.11 

11.52 

7.48 

4.95 

3.00 

2.51 

1.08 

1.23 



CLAY B. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



Scratched easily 

Scratched easily 

Difficult to scratch (Com. color) 

Very difficult to scratch 

Very difficult to scratch 

Barely possible to scratch . . . . 

Equal to steel 

Steel hard ". 

Harder than steel 

Harder than steel 




Open grained . . . . 
Open grained . . . . 
Dry and stony . . . 
Dry and stony . . 
Dry and stony . . 

Stony 

Stony, very dense 
Stony, very dense 

Vitreous 

Semi-vitreous . . . 



31.07 
31.12 
26.80 
25.76 
26.15 
21.95 
19.29 
12.57 
14.04 
3.12 



CLAY C. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



Scratched very easily 

Scratched very easily 

Slightly harder 

Difficult to scratch (Com. color) 

Equal to steel 

Harder than steel 

Harder than steel . , 

Harder than steel 

Harder than steel , 

Harder than steel (overfired) 




Very open grained. 
Very open grained. 
Very open grained. 

Open, stony 

Dense, stony 

Semi-vitreous .... 

Vitreous 

Glassy 

Glassy 

Stony 



35.94 

35.02 

32.45 

17.00 

14.30 

7.41 

5.22 

4.07 

1.10 

0.98 



106 



BULLETIN ELEVEN 



TABLE No. 17— Continued; 

Showing Comparative Hardness of Trial-pieces of the Standard Roofing Tile 

Clays. 

CLAY D. 



Designa- 
tion of 
Trial- 
piece. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



Description of Resistance to Cutting. 



' Tempcr- 
I ature 
in Cones. 



Character of Fracture. 



Scratched very easily 

Scratched very easily 

Scratched very easily 

Difficult to scratch (good color) 
Nearly equal to steel(best color) 
Harder than steel (good color) 

Harder than steel 

Harder than steel 

Harder than steel (overtired) . 
Harder than steel (overfired) . 



010 

08 

06 

04 

02 

1 

2 

3 

4 



Percent- 
age 

Porosity. 



Open grained 
Open grained 
Open grained 
Dense, stony 
Semi-vitreous 
Semi-vitreous 
Semi-vitreous 
Semi-vitreous 

Stony 

Stony 



32.85 

32.03 

33.29 

24.59 

13.04 

12.62 

10.12 

2.62 

0.74 

0.80 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



CLAY E. 



Scratched easily 

Slightly harder 

Slightly harder 

Slightly harder 

Slightly harder 

Ec^ual to steel 

Trifle under steel hard 

Harder than .steel 

Harder than steel 

Harder than steel (overfired) 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



Open grained ... 
Open grained ... 
Open grained ... 
Little more dense 
Little more dense 

Stony 

Strong, but open 

Vitreous 

Vitreous 

Stony 



38.42 

39.87 

39.34 

41.67 

40.10 

12.50 

26.24 

1.90 

2.72 

1.60 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



CLAY F. 



Very easily scratched 

Much harder 

Much harder 

Difficult to scratch 

Difficult to scratch 

Harder than steel 

Harder than steel 

Harder than steel ^ 

Harder than steel (overfired) 
Harder than steel (overfired) 




Very open grained 
Very open grained 
Very open grained 
Dense, stony .... 
Dense, stony .... 

Vitreous 

Semi-vitreous . . . 

Vitreous 

Stony 

Stony 



33.99 

31.83 

33.48 

23.65 

24.61 

12.08 

16.83 

2.93 

0.60 

1.24 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



CLAY G. 



Very easily scratched 

Very easily scratched 

Nearlyequal to steel (goodcolor) 
Nearly equal to steel] 
Nearly equal to steel ^bestcolor 
Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



Very open grained 
Very open grained 

Stony 

Stony 

Stony 

Semi-vitreous ... 

Vitreous 

Vitreous 

Vitreous 

Stony 



28.31 
27.73 
19.03 
16.19 
8.22 
9.10 



8. 
8. 
8, 
7, 



77 
42 
42 

82 



GEOLOGICAL SURVEY OF OHIO. 



107 



TABLE No. 17— Continued. 

Showing Comparative Hardness of Trial-pieces of the Standard Roofing Tile 

Clays. 

CLAY H. 



Designa 
tton of 
'1' rial- 
piece. 



Description of Res'stance to Cutting. 



Tenper- 

ature 
in Cones. 



Character of Fracture, 



Percent- 
age 
Porosity. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



1 
2 
3 
4 
5 
6 
7 
^ 
9 
10 



Easily scratched 

Slightly harder 

Same 

Difficult to scratch (good color) 
Difficult to scratch (good color) 
Harder than steel, too dark. . 
Harder than steel, too dark . 
Harder than steel, too dark. . 
Harder than steel (overfired) 
Harder than steel (overfired) 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



Very open grained. 
Very open grained. 
Very open grained. 

Dense, stony 

Dense, stony 

Semi- vitreous .... 
Semi-vitreous .... 

Vitreous 

Stony 

Stony 



30.96 

24.88 

29.94 

24.95 

25.37 

8.03 

16.20 

1.63 

2.56 

1 97 



CLAY I. 



Difficult to scratch i 010 

Difficult to scratch (best color) . '< OS 

Very difficult to scratch 06 

Very difficult to scratch ' 04 

Very difficult to scratch 02 

Nearly equal to steel 1 

Equal to steel , 2 

Steel hard 3 

Steel hard ; 4 

Steel hard (overfired) 5 



Open, stony 33.04 

Open, stony 33.33 

Stony 32.10 

Stony 32.17 

Stony 32.10 

Stony 29.62 

Stony 23.88 

Semi- vitreous 17.94 

Semi- vitreous 15.32 

Stony 0.52 



CLAY J 



Difficult to scratch 010 



Difficult to scratch 

Nearly equal to steel] 

Equal to steel fbest color 

Equal to steel J 

Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel (overfired) . 



OS 

06 

04 

02 

1 
o 

3 
4 
5 



Open grained . 
Open grained . 

vStony 

Semi-vitreous . 
Semi- vitreous . 

Vitreous 

Vitreous 

Vitreous 

Vitreous 

Stony 



24.55 
22.98 
11.22 
9.30 
9.15 
7.41 
7.17 
7.40 
7.8S 
9.21 



CLAY K. 



1 
2 
3 
4 
o 
6 
7 
S 
9 
10 



Difficult to scratch } 010 

Difficult to scratch OS 

Barely possible to scratch .... I 06 

Harder than steel 



Harder than steel 
Harder than steel 
Harder than steel 

Overfired 

Overfired 

Overfired 



04 

02 

I 

2 

3 
4 
5 



Dry, earthy fracture ' 17.53 

Stony ' 14.48 

Stony 

Semi-vitreous 

Vitreous 

Vitreous 

Semi-vitreous 

Spongy 

Spongy 

Spongy 



8.24 
5.77 
1.71 
0.65 
0.80 



108 



BULLETIN ELEVEN 



TABLE No. 17— Concluded. 

Showing Comparative Hardness of Trial-pieces of the Standard Roofing Tile 

Clays. 

CLAY L. 



Designa ■ 
tion of 
Trial- 
piece, 



Description of Resistance to Cutting. 



Temper- 
ature 
in Cones. ! 



Character of Fracture. 



Percent- 
age. 
Porosity. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



Difficult to scratch 

Difficult to scratch 

Very difficult to scratch 

Nearly equal to steely ^ ^ 
Nearly equal to steel J v^wav^x 

Steel hard 

Harder than steel 

Harder than steel 

Overburned 

Overbumed 



010 
08 
06 
/ 04 
02 
1 
2 
3 
4 
5 



I 



Stony, open 
Stony, open 
Stony, open 
Stony, more 
Stony, more 
Vitreous 
Vitreous 
Vitreous 
Stony. . . 
Stony. . . 



grained 

grained 

grained 

dense 

dense 



27.26 
24.82 
22.59 
18.35 
15.50 
15.63 
12.76 
10.55 
5.20 
4.45 



CLAY M. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



Easily scratched 

Easily scratched 

Difficult to scratch 

Difficult to scratch 

Difficult to scratch 

Nearly equal to steel (best color) 

Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel 




Stony, open grained 
Stony, open gained 
Stony, more dense. . 
Stony, more dense. . 
Stony, more dense. . 

Stony 

Glassy 

Vitreous 

Vitreous 

Stony 



29.88 

29.42 

28.49 

28.73 

27.74 

21.73 

10.73 

3.66 

3.10 

0.51 



CLAY N. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



Easily scratched . . . , 
Easily scratched . . . , 

Slightly harder , 

Same 

Same , 

Nearly equal to steel 
Nearly equal to steel 
Harder than steel . . . 
Nearly equal to steel 
Melted 




Open grained 
Open grained 
More dense . 

Same 

Same 

Stony 

Stony 

Stony 

Stony 

Slaggy 



37.12 
38.25 
37.64 
37.20 
36.42 
18.25 
17.86 

5.68 
21.04 

1.01 



CLAY O. 



1 
2 
3 
4 
5 
6 
7 
8 
9 
10 



Easily scratched 

Slightly harder 

Much harder 

Difficult to scratch 

Very difficult to scratch 

Equal to steeU, . , 

Equal to steel/ ^^^^ ^°^°^^ * * ' ' 

Harder than steel 

Harder than steel 

Harder than steel 




Open grained 

Open grained 

Open grained 

Becoming dense 

Very dense, but dry 

Stony 

Stony 

Semi-vitreous 

Semi-vitreous 

Stony '. 



GEOLOGICAL SURVEY OF OHIO. 109 

In order to obtain some judgment as to what degree of hardness 
in the foregoing tables represents a satisfactory roofing tile structure, 
we must be guided by the following considerations: 

A tile should have a hardness sufficient to make it easily handled 
and shipped without chipping or easy breakage, and above all to resist 
any damage from frost. But a tile burned to a degree of extreme 
hardness is just as much at fault as one too soft-burned. In the former 
case, the tile has been carried to a degree of vitrification where it becomes 
vitreous and is brittle, and will withstand handling, shipping, and cutting 
at the roof very poorly and large losses will result. Also, what has been 
said earlier in this report under the heading of "Porous vs. Vitrified 
Tile'' applies to the hardness also. That is, a tile that has been burned 
to a degree of hardness such that it is vitreous, will not prove as satis- 
factory upon the roof as a medium hard one. The extremely hard tiles 
will sweat, owing to their inability to absorb the moisture condensed 
upon their under surfaces. 

While the foregoing method of testing the hardness of the various 
commercial tiles and the vitrification trial pieces was very crude, it has 
shown one point quite clearly, viz., that the best commercial colors of 
the clays are found to correspond quite closely to the hardness of steel 
or a trifle below. The moment the trial piece becomes harder than 
steel, the fracture appears vitreous, and the color in most cases becomes 
too dark. These latter tile would be too hard for economy in commercial 
handling. In the light of the foregoing data and discussion, we may 
say that the hardness phenomena of the typical roofing tile clay will 
be about as follows: 

TABLE No. 18. 
Range of Hardness of Typical Roofing Tile Clay. 



Cone. 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



Hardness Data. 



Generally soft and easily cut. 
Generally soft and easily cut 

Difficultly cut 

Very difficultly cut 

Steel hard 

Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel 

Harder than steel 



Commercial Grade. 



Too soft. 

Too soft. 

Generally too soft. 

Generally good. 

Prime. 

Getting too hard. 

Too hard. 

Too hard. 

Overfired. 

Overfired. 



Hardness vs. Vitrification Range* — In order to reduce the fore- 
going mass of data to a more compact form, for the purpose of drawing 



no 



BULLETIN ELEVEN 



conclusions more easilj', the following symbols were used in the follow 
ing table: 

Degree of Hardness Symbol 

Very easily scratched }^ 

Easily scratched 1 

Difficultly scratched 2 

Very difficultly scratched 3 

Equal to steef. 4 

Harder than steel 5 

Assembling the data in this form, w^e have: 



TABLE No. 19. 
Hardness as a Gauge of the Vitrification Range. 



Cone 



Clay Samples. 



I A 



B 



C ' D 



E 



F 



H ' I 



K ! L 



M 



N 



O 

1 
1 
2 



010 

08 

06 

04 

02 

1 

2 

3 

4 

5 



1 
2 
2 

4 



5 



1 
1 
2 
3 



} 
1 

1 



i 

i 
1 



1 
1 
2 



1 
1 



1 
1 



1 



1 



4 



2 
2 



1 
1 



1 
1 



The heavy line has been drawn in the preceding table at a point 
supposed to represent the transition of the clay from the stage where 
it can barely be cut, to the steel-hard stage. This particular hardness 
cannot be correlated with either the beginning of commercial grades 
or the end of them. It is likely to represent the middle of the valuable 
period of the clay's life — not too soft to stand weather, nor so hard 
as to be brittle and glassy. 

It will be seen that clays I and N, both of which are poor materials, 
high in lime and of bad color, show a slow or gradual hardening, and 
have a different vitrification habit from the other clavs. Aside from 
these two clays, the line clings closely to the temperature zone 04-02-1. 

It is not possible to show the rauge of the vitrification process by 
hardness data, as well as by color or other tests, for no change of hard- 



GEOLOGICAL SURVEY OF OHIO. m 

ness occurs to mark the condition of overfire, until the latter becomes 
excessive. 

Porosity — The vitrification process in clays is most accurately 
marked by the changes in porosity of the sample. Vitrification means the 
assumption of a dense condition by a body originally always porous and 
sponge-like in structure. The vitrified body may or may not be vitreous, 
or glass-like. It may even be still notably porous, at the stage where 
it attains the best approach to a dense, vitreous structure that it is able 
to make at any temperature. Some clays never do vitrify to any sat- 
isfactory degree, but after gaining strength, hardness and density to 
only a moderate degree, they begin to undergo the bloating and de- 
structive changes of overfire. 

Vitrification is brought about by partial fusion of the mass, or 
rather the progressive fusion of portions of the mass and the attack 
on the still sohd remainder by this fluid magma. As the fusion pro- 
ceeds, the spaces between the original grains fill up and are obliterated, 
and if carried to the extreme of perfect fusion, the mass would become 
like a glass, entirely solid and devoid of recognizable pores. 

Since clay wares are not fused and cast in moulds, as glass or metal 
is, but are moulded while plastic with water, and merely carried up to 
such hardening as is safe without loss of shape by fusion, it follows 
that the initial structure of the mass is always preserved to some extent, 
and the voids between the grains, which constitute from 30 to 40 per 
cent, of the Volume of the clay at the end of the dehydration and oxi- 
dation process, are never fully closed up. Consequently, all clay 
wares are somewhat porous, or rather they contain cavities filled with 
air or gases. But the voids are inter-communicating in the beginning; 
the clay is porous in the real sense of the word, and fluids or gases will 
permeate it freely. But as vitrification progresses, the communication 
between voids becomes less and less perfect, and when the process is 
complete, in the sense of having reached the best combination of 
qualities that the clay can produce, these voids usually communicate to 
only a very limited degree. They are mostly present now as gas-blebs 
or sealed cavities, and are not properly pores at all. A clay burnt to 
this stage is not able to absorb much if any water, because the cav- 
ities inside do not reach the surface. 

The extent to which the porosity of a given clay will be extinguished 
under heat treatment will be dependent upon many factors — the min- 
eralogical composition of the clay, the size of its grains, and their pro- 
portions, and the intimacy of the mixture are prominent factors. For 
instance, calcium carbonate, if finely ground and evenly distributed 
throughout a clay mass in not too large proportion, will cause early 
and very rapid fusion of the body, but, should a like quantity of the 
same material be added in coarse, granular, or lump form, it will have 
but very little effect upon the mass, and combination will occur only 



112 BULLETIN ELEVEN 

at the points of contact. The rate at which the heat is applied, the 
pressure on the mass, and the chemical condition of the fire gases, also 
affect the rate of vitrification profoundly. 

In a study of all the changes that occur in the burning of a clay, 
there is no single factor that will explain what has taken place as well 
as a close study of the porosity changes. From these may be detected 
very clearly, not only the rate of the vitrification process as a whole, 
but also the periods of rapid or slow action, and the point where the 
failure of the mass begins. From what may be learned from the po- 
rosity curve, very safe conclusions can l>e drawn as to the suitability 
of a given clay for manufacture, so far as its vitrification behavior is 
concerned. 

The percentage porosity expresses the relation between the volume 
of pore space and the combined volume of the particles of which the 
clay is composed. It is, in other words, the ratio of the void spaces to 
solid particles. 

Dr. E. R. Buckley^ gives the following formula for determining 
porosity: ^,^ //, ;■) 

(W-D) Sp.gr. '^ X>y/^r^- 

100 = per. cent, porosity. */ 

(W -D) Sp. gr. + D 

W = saturated weight. 
D =dry weight. 

Sp. gr. =The composite specific gravity of the clay particles, as calculated 
from the dry, saturated, and suspended weights of the trial pieces. 

Purdy' has simplified the formula of Dr. Buckley to the expression: 

W -D 

100 = Porosity. 

W-S 

The Purdy formula was used in this work. 

The trial pieces for this measurement of porosity were obtained 
by breaking the one inch by one inch by six inch vitrification trial pieces 
in two. These pieces were carefully dried on a hot plate to constant 
weight; then, without allowing time to absorb water from the atmos- 
phere, they were weighed on a chemical balance, accurate to one-hun- 
dredth of a gram. 

Each trial piece was then immersed in distilled water, with one end 
slightly exposed to allow easy escape of the air. At the end of 24 to 
30 hours, they were placed under a bell-jar and the air kept exhausted 
for a psriod of about 4 hours, it liaving been found necessary to hold 

* Wisconsin Geol. anl Natural History Survey, Bull. VII, Econ. Series 4, 
P. 20. 

»Purdy, R. C. Illinois Geological Survey, Bull. 9, p, 142. 



GEOLOGICAL SURVEY OF OHIO. 



113 



them under vacuum for that length of tim2 to bring out the last traces 
of gases that would come out of the interior voids. 

After this treatment, the trial pieces were suspended, one at a time, 
by means of a silk thread, from the beam of a chemical balance and 
their saturated weights taken. While still suspended by the thread, 
a beaker partly filled with distilled water was brought up from below, 
so that the briquette was immersed in water and could still swing clear 
from the sides of the beaker. Thus the suspended weight of each trial 
piece was taken. 

These three determinations, applied in the formula before quoted, 
gave the porosity in per cents. These figures were obtained on each 
trial piece, representing each temperature at which draws were made, 
from the standard list of roofing tile clays. 



TABLE No, 20. 

Shpwing Porosity of the Standard Roofing Tile Clays, Fired to Different 

Stages of Vitrification. 



Designation of Clay. 



A 
B 
C 
D 
E 
F 
G 
H 
I 

k 

L 
M 
N 

O 



Heat Treatment Expressed in Cones. 



010 ; 08 06 



04 ' 02 



1 



29. 
3L 
35. 
32. 

138. 

'33 

'28, 

1 30, 

,33, 

!24, 

|17. 

27. 

29. 

37. 

27. 



53 



25.77 



07131.12 



94 35.02 
8532.08 
42 39.87 
99 31.83 
31 27.73 
96 24.88 
04 33.33 
55 22.98 
53 14.48 
26^24.82 
88,29.42 
12 38.25 



31 



32.23 



18.11 
26.80 
32.45 
33.39 
39.34 
33.48 
19.03 
29.94 
32.10 
11.22 
8.24 
22.59 
28.49 
37.64 
29.04 



I 

11.52] 

25.76 

17.001 

24.59, 

41.67 

,23. 65! 

,16.19, 

24,95 

,32.171 

9.30| 

5.77 

18.35' 

28.73i 

37.20 

22.85' 



7.48 
26.15 
14.30 
13.04 
40.10 
24.61 
16.69 
25.37 
32.10 
9.15 
1.71 
15.50 
27.74 
36.42 
20.04 



4.95 


3.00 


2.51 


1.08 


21.92 


19.29 


12.57 


14.04 


7.41 


5.22 


4.07 


IJO 


12.62 


10.12 


2.62 


0.74 


12.50 


26.46 


1.90 


2.72 


12.08 


16.83 


2.93 


0.60 


8.22 


9.10 


8.77 


8.42 


8.05 


16.20 


1.65 


2.56 


29.62 


23.88 


17.94 


15.32 


7.41 


7.17 


7.40 


7.88 


0.65 


0.80 


Bloa 


ted 


15.63 


12.76:10.55 


5.20 


21.43 10.73 


3.66 


3.10 


18.25 17.86 


5.68 


21.04 


8.84 


11.74 


7.31 


3.92 



1.23 
3.12 
0.98 
0.80 
1.33 
1.24 
7.82 
1.97 
0.52 
9.21 

• • • • 

4.45 
0.51 
1.01 
5.35 



Analysis of the Porosity Data* — In order to facilitate the read- 
ing and meaning of the data in the preceding table, an effort has been 
made to classify the clays shown into three different groups and to 
depict by curves the percentage porosity of the clays of each group. 

Group I . This group is of exceedingly narrow vitrification range. 
It comprises clays E, N, M and H. In none of this group do any 
serious or significant porosity changes occur prior to cone 02, but imme- 
diately following that point the porosity drops very rapidly until, at 
cone 3, vitrification is practically complete and no further diminution 
of porosity occurs with further accessions of heat (Figure 26). This signi- 
fies that the vitrification process or the mutual solution of the minerals 



8— G. B. 11. 



114 



BULLETIN ELEVEN 



of the clay does not begin early, but that it proceeds with great vigor 
when once begun. They indicate also that if the burning process is 
interrupted at a point between cones 02 and 3, that the tiles in the 
kiln would be apt to show a very irregular degree of porosity, for in no 




OJ(/QAT/Of^ FSfS/ao O/O Off ffS O^ ^£ / ^ J 

Fig. 26 — Porosity Changes in Clays of Group I. 

ordinary kiln-burning of such wares is the entire kiln likely to fall within 
a range of one cone in temperature. But in the four clays cited, one 
cone in temperature stands for a large reduction in porosity, so that 
with ordinary variations of kiln temperature we should have great 
variations in vitrification. 



GEOLOGICAL SURVEY OF OHIO. 



115 



In the following table are shown the facts as to the porosity changes 
per cone for clays composing this group: 





TABLE No. 21. 

• 

Porosity Changes per Cone in 


Group I. 




Designation of 
Clay. 


Temperature 
Range. 


Number of Cone 
Intervals. 


Reduction in 
Porosity Per cents. 


Reduction in Po- 
rosity Per Cone. 


E 
N 
M 
H 


02-3 
02-3 
02-3 
02-3 


4 
4 
4 
4 


38.20 
30.74 
24.08 
23.72 


9.55 
7.68 
6.02 
5.93 



The facts shown in this table constitute a serious indictment against 
these clays, of course. If the ware were of a sort that permitted selling 
in a wide variety of hardness, as common bricks do, so that the kilns 
need not be raised above cone 02, or if the ware could be kept in shape 
well at temperatures exceeding c(me 3, so that all of the kiln could be 
brought to that point, constant physical structure in the product, so far 
as porosity is concerned, would be expected. 

The color-temperature range has been indicated on these curves for 
the purpose of showing in what portion of the burn the colors are most 
satisfactory. We find considerable variations, but in three of these 
four clays, the colors are as good as the clays respectively can generate 
for a period preceding active vitrification. If the kilns could be finished 
off at these temperatures, then the burning would be relatively easy. 
But, the porosity being still almost unaffected, the wares would be 
altogether too soft for use. Later, when the clay has shrunk and become 
dense and hard, the color is no longer suitable for roofing tiles. In the 
case of clays N and E, both are calcareous, buff-burning materials and 
would require slipping at any temperature to get a marketable color. 

It should be noted that three erratic determinations have been 
rejected in drawing these curves. The determinations are plotted, 
with the clay that they belong to marked beside them, but they seem 
so certain to be due to some discrepancy in weighing, or recording, or 
to uneven heat distribution in the test kiln, that they have not been 
considered in the above remarks or the curves. 

Group II. — This group comprises clays of moderate vitrification 
range and rate. It includes clays A, C, D, F and 0. There are several 
determinations here also that seem unduly erratic, especially clay F at 
cones 02 and 2, and clay O at cones 010 and 1. They have been plotted, 
but the curves have been drawn with allowances or corrections in accord- 
ance with the preponderance of the data. (See Figure 27.) 



116 



BULLETIN ELEVEN 



These clays differ from the first group in three respects. First, they 
do not delay so long in beginning to undergo important porosity changes. 
At cone 08, in all but clay O, and at cone 06 in the latter, the vitrification 
process is evidently busy at work. Second, they do not progress at 
nearly so rapid a rate, as they are not down to minimum porosity till 
cone 4 is reached. This shows a complete vitrification range of eleven 
cones, or approximately 220° C, as against four cones for group one. 











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The average reduction of porosity per cent, per cone in this group, be- 
tween cones- 08 and 4, is about 2.70%. In the following table arc shown 



GEOLOGICAL SURVEY OF OHIO. 



117 



the facts as to the clays composing this group, in the zone of their 
most rapid vitrification: 



TABLE No. 22. 



Porosity Changes per Cone in Group II. 



Designation of 
Clay. 



Temperature 
Range. 



Number of 

Cone 
Intervals. 



C 


06-1 


6 


F 


06-1 


6 


D 


06-1 


6 


A 


08-02 


6 


O 

• 


06-1 


6 



Reduction of 
of Porosity 
Per cents. 



Reduction of 

of Porosity 

Per Cone. 



• 

25.04 


4.17 


21.40 


3.56 


20.77 


3.46 


18.29 


3.05 


20.20 


3.36 



The reduction in porosity, in the most rapid part of the process, over 
a range of 6 cones is much lower than in 4 cones in Group No. 1. If 
the entire vitrification range of these clays (instead of the most rapid 
part only) were included, it would show a stiH more striking contrast. 

Third, the period of good color occurs after vitrification is relatively 
well advanced — much later than clays H and M in Group No. 1. There 
is a chance, therefore, to get these clays finished off during a period of 
relatively slow vitrification change, which is essential to safe and profit- 
able burning. 

Group III. — These arc clays of slow vitrification rate and wide 
range. This group comprises clays B, G and L. Clays I, J and K, which 
are blended to produce L, are not given a separate position, because 
none of them are by themselves used for roofing tile manufacture. 

The clays of Group No. 3 show three erratic determinations, two 
in clay L, at cone 02 and 1 , and one in clay B at cone 4. These determi- 
nations have lx)en plotted, but not drawn into the curves. They are 
probably duo to experimental errors, very likely in irregular heat distri- 
bution in the test kiln, (^'ee Figure 28.) 

This group is characterized by a continuous and gradual reduction 
of porosity from cone 010, when the first draw-trials were taken, to cone 
5, when the last was taken, and none of them were yet as dense as many 
clays become. Their average drop in per cent, absorption per cone, 
over the range in which vitrification is in progress, is about 1.7^^ over 
the whole zone. Clay B belongs to this group with less certainty than 
the others. It might be graded in Group No. 1 nearly as well. 



118 



BULLETIN ELEVEN 



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Fig. 28 — Porosity Changes in Clays of Group III. 
In table No. 23, the porosity changes per cone are contrasted • 

TABLE No. 23. 
Porosity Changes per Cone in Group III. 



Designation 

of 

Clay. 


Temperature 
Range. 


Number of 

Cones 
Interval . 


Reduction in 

Porosity 

Per cents. 


Reduction in 

Porosity 

Per Cone. 


B 
G 

L 


04-1 
08-02 
010-04 


6 
6 
6 


13.58 

11.54 

8.91 


2.26 
1.92 
1.48 



The zone of commercial color is seen to occur in the middle of the 
vitrification process, but with changes progressing so slowly that it 
should be possible to fire a kiln off with fairly uniform color throughout. 

The clays of this group have an undoubted advantage over both 
preceding groups, so far as the evidence of the porosity changes is 
concerned. If satisfactory in other respects, they should be very safe 
in the kiln. 

For purposes of comparison, the following curve-sheet (Figure 29) 
containing clays I, J, K and the body blended from them, L, has been pre- 
pared. It is to be observed that clay K, which is the basis of the mixture, 



GEOLOGICAL SURVEY OF OHIO. 



119 



has a very steady vitrification process, coming to completion at cone 02, 
and bloating badly if overfired beyond cone 2. This clay has evidently 
begun to vitrify well before cone 010, as the porosity at cone 010 is only 
17.53%, which is too low for any clay in its period of maximum openness 
of structure. 





































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Fig. 29 — Porosity Changes per Cone in Clays I, J, K and L. 



To this regular but very early vitrifying clay are added I, a clay 
clearly belonging to Group No. 1, which vitrifies hardly at all until cone 
1, and clay J, which vitrifies rapidly at cone 06, and thereafter changes 
little in the temperature limits tested, but which reaches only a very 
imperfect vitrification at best. 

L, the mixture or composite clay, shows beautifully the influence of 
these components. Its course is parallel to clay K, but its progress is 
much delayed, so that when clay K is fully vitrified and ready to swell 
from overfire, clay L has still 12.75% porosity, and this is not wholly 
eliminated by going to cone 5, though the body becomes undesirable 
for foofing tile long before that point. 

In view of the fact that clay K has a good color by itself and appar- 
ently a good, though very early vitrification behavior, it would appear 
that the addition of clays I and J to it, spoiling not only its color but 
its vitrification behavior as well, is unfortunate. The occurrence of 
the three clays in the mine would make it difficult and expensive to 
mine clay K without also mining I and J, which is the reason for their 
inclusion in the mixture. 



120 



BULLETIN ELEVEN 



Summary on Porosity Changes* — The grouping of the twelve roofing 
tile clays into three more or less clearly defined groups on the strength 
of their porosity curves is not, however, a conclusive or satisfactory 
decision as to their quality. Good clays and bad ones, judged by other 
and not less important criteria, are found both in and out of each group. 

. Considering the clays in two groups — those of good color and those 
of bad — and listing the porosity data opposite eaph we have: 

TABLE No. 24. 
Comparison of Color Range and Porosity Behavior. 



Designation 
of Clay. 



Character of Porosity Curve. 



A 
B 
C 

D 
G 
H 
M 
O 



E 
F 



L 

N 



C/3 

"o 
PQ 



Wide vitrification range. Slow changes. Process com- 
plete at cone 3. 

Wide vitrification range. Slow changes. Process com- 
plete at cone 5. 

Rather narrow range. Rapid changes between cone 06 
and 04. Moderate between 02 and 3, in zone of use- 
ful colors. Complete at cone 4. 

Rather narrow range. Rapid changes between 06 and 
02. Complete at cone 3-4. 

Wide range. Changes slow. Process incomplete at 
cone 5. 

Narrow range. Sudden changes between cones 02 and 1. 
Changes complete at cone 3. 

Narrow range. Sudden changes between 02 and 3. Fin- 
ishes proce.ss at cone 5. 

Fairly wide range. Changes steady and not rapid. 
Changes incomplete at cone 5. 



Very narrow range. Rapid changes between 02 and 3. 
Complete at cone 3. 

Rather broad range. Erratic. Most rapid changes be- 
tween cones 02 and 1. Finishes process at cones 3 
and 4. 

Very wide range. Slow processes, incomplete at cone 5. 

Very narrow ran^e. Changes very rapid between cone 
02 and 3. Vitrification complete at cone 5, 



Thus we have six clays whose vitrification range is good; four of these 
have good color, while two are of poor colors, though not the worst. 
On the other hand, we have six clays whose vitrification range is narrow. 
Of these, four have good colors, while two have colors entirely unfit for 
use without slipping. 

In view of these facts, it can hardly be claimed that a typical roof- 
ing tile clay can be set forth, judged on the basis of its porosity changes. 

Porosity vs» Vitrification Range* — While the definition of a type 
clay is not possible from the foregoing evidence, it is not so diflicult to 
construct an ideal of what the porosity changes should be to constitute 



GEOLOGICAL SURVEY OF OHIO. 



121 



a desirable clay from the standpoint of safe burning. Suppose the clay 
in question is to reach complete maturity of color at cone 1. The follow- 
ing may be taken as a desirable porosity behavior. 

TABLE No. 25. 
Relation Between Porosity Behavior and Color, in Ideal Roofing Tile Clay. 



Temperature 
Expressed 
in Cones. 



Porosity 

Expressed in 

Per cents. 



Below 010 

010 

08 



. . to 30 
30 to 26 
26 to 18 



06 

04 

02 

1 



18 to 10 
10 to 6 
6 to 4.5 
4.5 to 3 



Color- Sequence and Structure. 



Light yellow or pinkish reds — not commercial. 
Structure very porous. 



2 
3 



3 to 2 
2 to 3 



4 
5 



3 to 4 

4 to 6 



Commercial red colors, ranging from light to dark. 
Structure, sufficiently dense. 



1 Colors too dark. 

J Body at greatest density. 



IColors entirely overdone. 

/Body beginning to swell from overfire. 



Whether any given clay reaches its maturity at the temperature 
limits indicated above, is not so important as that the general shape of 
the porosity curve should iDe substantially as shown. Its most rapid 
changes should occur before the development of the best commercial 
colors; then a period of good colors and relatively small porosity changes, 
merging into a zone of darker colors, and still less body change, and 
finally destruction of marketable colors and the increase of porosity 
from the swelling of the body. 

Specific Gravity — Until recently the specific gravity, while frequently 
determined, has yielded little if any intelligent insight into the clay's 
qualities. It was found that per se the si^ecific gravity of a clay did not 
clearly indicate? anything, pro or con. It remained for Purdy* to make 
the first effective use of this determination, which he did by determining 
the specific gravity of clays at a series of stages of burning, and also by 
adopting precautions to get the real, as well as the apparent specific 
gravity. In his hands, this determination has been useful in analyzing 
the processes taking place in the vitrification of clays, and he has rein- 
forced the evidence obtained from the porosity and shrinkage studies. 
It has been of special importance in bringing out and demonstrating the 
amount and volume of the sealed pores in vitrified clay bodies, the 
existence of which could not be proved by absorption or porosity 
measurements. 



'R. C. Purdy, Illinois Geol. Survey, Bull. IX, p. 133. 



122 BULLETIN ELEVEN 

Method of Determination* — The formula by which the apparent 

D 
specific gravity of a lump of any substance is obtained is— — in which 

D — o 

D == the dry weight of the substance and S = the weight of the same 

substance suspended in water. 

The true specific gravity is determined from the powdered material, 
ground so fine as to make the existence of any sealed pores or gas cavities 
in the grains a matter of some improbability. This determination is 
made in a small flask, accurately standardized, and called a pycnometer. 

In the work done in this report, no effort was made to pursue these 
investigations to the refinement that has been shown in the work of 
Purdy*, which should be consulted for further details on the capabilities 
of this mode of research. The determinations were made by the simplest 
process and represent the apparent specific gravity only. 

The same test pieces used in the porosity test were used, and the 
same weights. The porosity data being at hand, a mere calculation 
suffices to obtain the apparent specific gravity and for this reason it 
has been deduced and tabulated. (See page 123.) 

Examining the data of the foregoing table, it may be observed 
that in every instance the changes in value run along with small vari- 
ations from low to higher temperatures, until finally a sudden or marked 
drop occurs. The point where the drop occurs is as early as cone 04 
in the case of clay K, while it only occurs at cone 5 in five other samples. 

The significance of this break in the figures of each clay is as follows: 
While the clay remains porous or only partially vitrified, its voids are 
very largely permeable by water, especially if resort be had to boiling 
or the vacuum pump to suck out the air and allow the liquid to take 
its place. Hence calculation, as per the formula above, gives a close 
approximation to the true specific gravity. But, when the fusion pro- 
gresses to the point of sealing up the voids, or creating new blebs, from 
the evolution of gases inside the sticky, glassy matrix, then- a deter- 
.mination of the specific gravity of the lump gives results too low, for 
the gases are only very imperfectly replaced by water, and the denom- 

D 

inator of the fraction becomes too large, owing to the increased 

U — o 

displacement of the swollen lump, without proportionately increased 
weight. If the mass continued permeable to water, then the value of 
D — S would remain constant, whatever its volume. 

The reduction of the "apparent specific gravit}' of the trial pieces 
indicates, therefore, the growth of sealed blebs or cavities, and this 
in turn indicates progress towards a pasty, sticky stage of vitrification 
or semi-fusion. A clay is therefore certainly deteriorating in structure 
when its apparent specific gravity grows markedly less. 

'Loc. cit. 



GEOLOGICAL SURVEY OF OHIO. 



123 



TABLE No. 26. 

Showing Changes in Specific Gravity of the Standard Roofing Tile Clays at 

Different Stages of Burning. 



ID esi If nation 






Temperature Expressed i 


n Cones 


• 




• 


of Clay. 


010 


08 


06 


04 


02 


1 


2 


3 


4 


5 


A 


2.54 

2.66 

2.63 

2.54 
2.63 
2.58 

2.68 

2.60 
2.67 

2.56 

2.46 

2.61 
2.56 

2.64 
2.50 


2.52 

2.67 

2.66 

2.58 
2.75 
2.56 

2.69 

2.58 
2.67 

2.55 

2.46 

2.54 
2.57 

2.70 
2.53 


2.45 

2.68 

2.64 

2.63 
2.73 
2.63 

2.68 

2.55 
2.64 

2.50 

2.44 

2.62 
2.67 

2.68 
2.52 


2.52 

2.68 

2.56 

2.58 
2.76 
2.56 

2.67 

2.58 
2.64 

2.50 

2.44 

2.59 
2.66 

2.67 
2.50 


2.48 

2.68 

2.55 

2.60 
2.62 
2.56 

2.57 

2.52 
2.63 

2.49 


2.46 

2.70 

2.50 

2.50 
2.51 
2.71 

2.62 

2.42 
2.55 

2.43 


2.42 

2.61 

2.49 

• 2.47 
2.60 
2.53 

2.53 

2.50 
2.55 

2.39 


2.41 
2.57 
2.45 


2.25 


2.23 


B 


2.56 


2.35 


C 


2.30 

2.28 
2.05 
2.06 


2.26 


D 

E 
F 


2.40 
2.39 
2.34 


2.20 
1.60 
2.04 


G 


2.54 


2.51 


2.35 


H 
I 


2.32 
2.45 


1.93 
2.44 


1.73 
1.93 


J 


2.39 


2.39 


1.96 


K 


2.34 


1.88 


2.00 

2.35 
2.50 










2.27 
2.44 


1.15 
2.41 




L 

M ' 


2.63 
2.62 

2.66 
2.48 


2.51 
2.62 

2.43 
2.45 


1.20 
2.21 


N 



2.44 
2.45 


2.36 
2.44 


2.46 
2.42 


2.02 
2.13 



Judged by this standard, the clays pass the line from a reason- 
ably sound structure into a rapidly failing stage at the point indicated 
in the table by a heavy black line in each horizontal column. 

Comparing these determinations of the failing point of the clay 
with those obtained from the porosity test, we find that the specific 
gravity indicates a clay as failing earlier than by the latter, often several 
cones earlier and usually at least one. There are, however, wide vari- 
ations in the extent of the indicated failure, and these are much more 
easily recognized by means of curves. 

For convenience, the clays are drawn on curve sheets (Figure 30) in 
the order of their reduction in specific gravity, from the maximum to the 
minimum of each clay. Thus clay A changes only 0.31 between its 
maximum and minimum, showing that at cone 5 viscous swelling, or 



124 



BULLETIN ELEVEN 




oio ^m OS ^^ fi£ / ^ J 



Fig. 30— Curves Showing Changes in Specific Gravity of the Standard 
Roofing Tile Clays at Various Stages of Heat Treatment. 



GEOLOGICAL SURVEY OF OHIO. 125 

development of sealed gas blebs, had progressed to a small extent only. 
Clay L. on the other hand, changed 1.4S in specific gravity in the same 
heat treatment, showing the clay was far gone in viscous bloating. 
No effort has been made to group these clays according to the actual 
numerical value of their specific g avity, as this is a function of their 
mineral composition. It will be noted that the bad, limy clays E and 
N both show exceptionally high specific gravity, 2.76 and 2.70 res- 
pectively. 

A study of these curves shows a very considerable variety in their 
details, but the tendency is for each clay to attain a maximum, some- 
where prior to cone 02, and thereafter fall away more or less sharply, 
as the sealed pores begin to affect the volume. 

Clays A, G, B, C, O, D and M all have curves in which the reduction 
is moderate in amount, and occurs late enough in the firing, to show 
that these clays have wide vitrification ranges and safe vitrification habit. 
Clays F, X, H, E, L and K all show curves in which the reduction > 
large in amount and rapid in rate, and indicate clays of unsafe vitri- 
fication habit. 

It will be noted that the clavs which are condemned in the color 
test, E, F, L and X, are all condemned by this specific gravity test also, 
and with them clay H, whose color is good. 

Xo standard of specific gravity for roofing tile clays, either in 
numerical amount or in rate of change, can be set as the result of this 
inquiry, but in comparison of other clays with these, a similarity of 
general contour with the clays here known to be of good working quality, 
would tend to confirm other sources of judgment. 

Total Shrinkage — The total shrinkage is a property of much concern 
to the roofing tile manufacturer. Of the total shrinkage which occurs be- 
tween the moulding of the plastic clay and its recovery from the kiln, 
that part of the change in volume which occurs in burning is of more vital 
importance. Proper pallets and forms can be made to hold a piece of 
clay straight and true while drying, but such devices, while possible 
in the burning, are too costly for wares which sell as cheap as roofing 
tiles. In an earlier part of this chapter, the drying shrinkage has been 
discussed in detail, and there now remains to consider the shrinkage 
in burning. 

A knowledge of the total shrinkage of a clay has a direct practical- 
application, as it furnishes the information necessary to construct dies 
and moulds of the proper size to make a piece of ware that will, when 
burned, have the proper size and dimensions. 

In order to obtain the correct total shrinkage for practical purposes 
it is, of course, necessary to grind the clay to the proper fineness, temper 
with the right amount of water and burn to the temperature required 
in the actual manufacture of the ware. 



126 BULLETIN ELEVEN 

The cause of the shrinkage of the clay is the same as the force which 
extinguishes the porosity and converts a spongy, cellular mass, full of 
voids, into a dense resistant solid that* steel will not cut nor weather 
crumble. The vitrification or interaction of the minerals, and their 
mutual solvent effect on each other at high temperatures, causes the 
particles composing the old mass to disappear and the spaces between 
to close up. This produces a shrinkage., which is usually greater in 
proportion as this action is more complete. 

But there is another force which tends to counteract this shrink- 
ing tendency, which has been discussed in connection with porosity and 
specific gravity studies. This is the tendency to form gas blebs or bubbles 
in the mass, which, unable to escape, swell as the temperature increases 
and tend to convert the clay into a cindery or frothy slag. These two 
processes are working against each other during vitrification. The 
shrinkage is more powerful for a time, and the clay grows less in volume 
in spite of the thousands of minute gas cavities that arc forming. But 
after a time, the swelling action is the more powerful, and then the 
shrunken clay begins to bloat, and may assume its initial size or even 
become much larger than it ever was. 

The causes of this swelling and the conditions and mineral com 
position which especially favor its development will not be discussed 
at greater length at this time. It is merely necessary to point out 
that if the shrinkages of a series of test pieces fired to progressively 
higher temperatures be measured and plotted on a curve, we will find 
that in nearly every clay the curve rises with the temiDerature for a 
time, sometimes at a uniform gradual rate, and sometimes very sud- 
denly, and then after reaching a maximum, it usually stands more or 
less constant in volume for a time, the shrinkage and bloating reactions 
being in a deadlock so to speak, and then the bloating triumphs and 
the volume increases again. 

The determination of the shrinkage in the test of the standard 
series of roofing tile clays was on the same series of test pieces which 
had been measured for the determination of the drying shrinkage. The 
methods of firing, drawing, cooling, etc., were as described in connection 
with the preceding tests for color, hardness, etc. The results are 
shown in table No. 27, page 127. 

In order to get the assistance of the graphic method, the data of the 
above table were plotted in a series of curves, excluding that from clays 
I, J and K, which are represented in their blend or mixture, clay L, but 
which have no separate use for roofing tiles (Figure 31). In plotting the 
above curves, efforts to divide up the clays into groups of similar behavior 
were not satisfactory or illuminating. Each clay has therefore been 
plotted singly, though arranged in the order of decreasing total shrink- 
age value, viz., clay O with 14.00 per cent, is first, clay C with 13.60 
par cent, is second, etc.. The beginning and ending of each curve is 



GEOLOGICAL SURVEY OF OHIO. 



127 



TABLE No. 27. 
Showing Total Linear Shrinkage of Standard Series of Roofing Tile Clays. 









Heat Treatment Expressed in Cones. 


De^gnation of 








Clay. 




1 




















010 


08 


06 


04 


02 


1 


2 


3 


4 


5 


A 


4.90 


6.00 


6.60 


9.90 10.9o!ll.80 


12.20 


11.60 


11.90 


11.00 


B 


3.00 


3.25 


5.00 


5.00 


5.00 


5.75 


7.00 


7.00 


8.00 


7.50 


C 


4.60 


6.30 


6.70 


10.50 11.90 


13.50 


13.50 


13.20 


13.60 


13.30 


D 


3.10 


3.30 


2.90 


7.00 


7.30 


11.20 


11.60 


13.00 


13.20 


12.60 


E 


6.00 


4.60 


4.90 


6.20 


5.60 


10.'30 


9.50 


13.00 


10.00 


*6.00 


F 


4.60 


5.30 


5.30 


8.60 


8.00 


11.80 


10.30 


11.00 


11.90 


11.00 


G 


3.00 


4.00 


6.50 


6.25 


7.25 


7.50 


8.50 


8.00 


7.00 


*5.50 


H 


7.20 


7.60 


7.60 


9.70 


8.30 


12.50 


11.30 


13.00 


* 


* 


I 


5.00 


5.00 


5.00 


5.00 


4.50 


5.50 


6.75 


8.00 


♦7.50 


6.00 


ic 


7.25 


8.00 


11.50 


11.50 


12.00 


12.00 


12.00 


12.25 


12.25 


*7.75 


7.40 


8.80 


11.40 


12.70 


13.82 


8.23 


He 


* 


* 


* 


L 


7.70 


7.70 


8.-50 


10.30 


10.30 


10.30 


9.70 


♦8.80 


0.50 


2.00 


M 


3.00 


3.50 


5.00 


5.25 


5.25 


7.00 


7.00 


10.00 


10.00 


♦8.75 


N 


5.50 


5.50 


6.50 


6.00 


6.50 


9.00 


9.50 


11.00 


10.00 


* 


O 


4.00 


: 4.00 

1 


5.00 


5.75 


9.50!l2.50 12.50 


14.00 13.00 


*10.C0 



♦Overfired. 

marked with the proper percentage, from which the imaginiary base- 
line for each curve can easily be picked out. No two curves refer to the 
same base-line. 

By this method of plotting, the shape or contour of a number of 
curves can be easily and rapidly compared, and the numerical value 
of each can be ascertained with a moment's attention. 

Inasmuch as these clays have already been studied for color 
changes, and the temperature zones within which they are' of commer- 
cial grade have been determined, it was thought useful to plot these 
zones on the shrinkage curve of each clay. Thus clay O is of com- 
mercial color between cones 02 and 3, and the line is doubled in thick- 
ness between these points, to indicate that this zone only is of direct use 
in the roofing tile industry. 

Lastly, the angularity and inconsistent jogs of the curves are not 
to be construed literally at all. Clays probably do not shrink in this 
erratic fashion. Shrinkage is not a free factor — the structure of the 
clay mass, its shape, size, its position in the kiln, its cooling treatment 
and many little things all unite to make shrinkage data erratic, and 
only by obtaining large numbers of tests on one clay, and averaging 
them, could the true course of the shrinkage habit be accurately plotted. 

Taking up the discussion of the clays, each in turn — 

Clay — This clay changes volume slowly up to cone 04, thence 
rapidly up to 14.00 per cent, at cone 3, bloating 4 per cent, in the next 
two cones. The commercial area falls in the zone of rapid shrinkage 



128 



BULLETIN ELEVEN 




wc OS »a c^ a^ / £ ^ ^ ^ 



Fig. 31 — Curves Showing Changes in Linear Shrinkage of the Standard 
Roofing Tile Clays at Various Stages of Heat Treatment. 



GEOLOGICAL SURVEY OP OHIO. 129 

and is immediately followed by bloating. It would seem to be difficult 
to so fire a kiln of this clay, as to secure even shrinkage and even color 
inv all parts of the kiln and at the same time avoid the production of 
some overfired goods. 

Clay C — This clay has a very much better habit. It shrinks rapidly 
and steadily from cone 010 to cone 02, but from cone 02 to cone 5 its 
volume is nearly constant. The total amount of shrinkage is high, 13.6 
per cent., but this disadvantage is much more than offset by the long 
period of stability when shrinkage is once complete. The zone of com- 
mercial color also falls in the zone of stable volume. This clay should 
be of excellent properties for this purpose. 

Clay D — This clay begins its volume change at cone 06, and becomes 
stable at cone 3, remaining so to cone 5, at least. The total amount 
of shrinkage, 13.20 per cent., is high. The zone of commercial colors 
falls in the period of rapid volume change and the difficulty of getting 
uniform size and uniform color would probably be considerable. 

Clay H — The clay changes but little in volume till cone 04, when 
a moderate fire shrinkage of 5 per cent. (13 per cent, total) occurs. The 
clay bloats badly if fired above cone 3. The color zone from 04 to 2 
coincides with the zone of most rapid shrinkage. This clay does not 
seem particularly fortunate in its combination of properties. 

Clay E — This is a calcareous clay of buff color, requiring a slip 
clay covering to make it saleable. The clay does not change poreeptibly 
in volume up till cone 02, but remains during this time very soft and 
not very durable to weather or wear. It can, however, be kept of con- 
stant volume over a whole kiln, and by slipping, of a constant color. It 
is possible, therefore, to use this material for roofing tiles with good 
results if the porous tiles can be disposed of. If, on the other hand, it is 
desired to vitrify the clay, the task is troublesome. There is no range 
at all at the top of the curve. Bloating and failure occur very quickly 
after cone 3 is reached, and prior to cone 3 the body is shrinking very 
rapidly. It would be impossible to produce hard, dense products from 
this clay in quantity, on account of the losses from either under- or over- 
firing. 

Clay A — This clay is an unusually favorable one. The total shrink- 
age is 12 per cent., but its temperature range, after shrinkage is practi- 
cally over, is 8 cones wide. The zone of good colors is 4 cones wide, 
and volume changes are largely over before the color is matured. 

Clay F — The determinations are somewhat erratic, but the clay 
probably begins to shrink at cone 06, reaches maturity at about cone 1, 
remaining practically constant up to cone 5. This clay has a bad color 
and would have to be slipped, so that so far as can be seen a burning 
temperature of 01 to 3 would find the clay changing but little, and the 
color as good here as at any other period. Any place between cones 
06 and 1 finds the vitrification process actively in progress. 

9— G. B. 11. 



130 BULLETIN ELEVEN 

Clay N — The contour of this curve seems exceptionally favorable, 
but the clay is one of the highly limy ones, and its slow and moderate 
changes are due to this fact. The body is soft and porous during the 
entire period, from cone 010 to cone 3, when it passes abruptly into vitrifi- 
cation and fusion. This clay would have to be slipped in any case, so 
that it could be used iat the zone 06 to 01 with good results, if a porous 
body could be marketed. 

Clay L — This clay has a drying shrinkage, but the fire shrinkage is 
very light and the rate of change very gentle up to cone 1. The pre- 
ponderance of clay K in the mixture, with its very low point of maturity, 
causes the mixture as a whole to deteriorate rapidly at cone 1. From 
cones 04 to 2 the conditions are favorable. The clay w^ould probably 
have to be slipped in any case, so that the best part of the curve should 
be selected as the finishing zone. 

Clay M — This is a clay of exceptional properties. A good color, 
a very low shrinkage, a very gentle rate of change from 06 to 2, and no 
rapid failure from overburning imminent, make this one of the best 
yet considered. 

Clay G — The same conditions here prevail. The clay ranges from 06 
to cone 3 with gentle changes, and has a fairly w-ide color zone in the 
most stable part of the curve. 

Clay B — Exceptionally favorable. Small shrinkage, slow changes, 
wide range in which the color is good, 06 to 1, and no rapid failure 
after the colors become too dark for roofing tile, make this clay an 
unusually favorable one for safe burning. 

A summary of the above shows: 

Classed as favorable — li, G, M, A, C among the red burning clays, 
and E, L and N among the porous, buff burning clays which would 
require slipping. 

Classed as unfavorable — 0, 1), H, and F. 

Fire Shrinkage. — By subtraction of the initial or drying shrinkage 
from the total shrinkage, we can learn the amount of change in size 
which is directly due to vitrification changes. This information is in 
some connections useful, but ordinarily the total shrinkage sufTiccs. 
In the following table, (Number 28), the fire shrinkages have been 
calculated for the present series of trial pieces. 

In examination of the fire shrinkage apart from the total shrinkage, 
it is undoubtedly easier to compare and contrast the vitrification 
changes, than when each observation is modified by the inclusion of the 
drying shrinkage. But it is not, in the present instance at least, possible 
to reach any new or different conclusions as to the relative safety or 
desirability of the clays, than those obtained from the study of tlie 
totals. 



GEOLOGICAL SURVEY OF OHIO. 



131 



TABLE No. 28. 
Showing Per Cents, of Fire Shrinkage on the Standard Roofing Tile Clays. 





Heat Treatment E 


xpressec 


1 in Cones. 




Designation of 














Clay. 
























010 


08 


06 


04 


02 

I 

1 


1 

1 


2 


3 


4 


5 


A 


0.60^ 


0.50» 


1.60 


5.15 


5.90 


6.30 


6.70 


6.11 


6.40 


6.00 


B 


0.00 


0.25 


1.50 


2.00 


2.00 


2.50 


4.00 


4.00 


5.00 


5.00 


C 


0.10 


0.80 


1.70 


6.00 


5.90 


8.50 


9.00 


8.70 


9.10 


8.80 


D 


0.40» 


0.30 


0.10^ 


3.50 


4.30 


6.95 


7.35 


8.75 


9.45 


8.70 


E 


0.00 


0.40^ 


0.10' 


0.20 


0.10 


4.30 


3.50 


6.25 


5.00 


6.00 


F 


0.90^ 


0.20» 


0.30 


3.35 


2.75 


6.30 


5.30 


7.00 


6.40 


6.50 


G 


0.50 


1.50 


4.25 


4.50 


5.25 


5.25 


6.50 


6.00 


5.00 


4.50 


H 


0.30» 


0.10 


0.10 


1.70 


0.80 


5.00 


3.80 


5.50 


2 


2 


I 


0.50 


0.50 


0.50 


0.50 


0.00 


1.25 


2.75 


3.75 


3.75 


2.25 


. k 


1.25 


1 75 


4.25 


5.50 


5.50 


6.00 


5.50 


5.85 


5.85 


0.50 


2.59 
1.00 


3.89 
2.20 


6.49 
3.00 


7.79 
4.30 


8.69 
4.80 


3.10' 
4.80 


8 

4.40 








L 


3.56 * 


5.00' 


3.00' 


M 


0.30^ 


0.20» 


1.30 


1.55 


1.55 


3.30 


3.30 


6.00 


5.50 


5.15 


N 


0.00 


0.00 


0.00 


0.50 


0.50 


2.50 


3.75 


5.50 


6.00 


3 


O 


0.00 


0.00 


1.00 


1.87 


5.50 


6.50 


7.00 


8.00 


8.00 


4.50 



' — Increase over original dry measure. 

'—Melted. 

3— Bloated. 



WARPAGE. 



The tendency exhibited by clay wares to warp or deform at some 
stage in their treatment between the time they leave the machine, 
or die, or mould, or hands which formed them, and the time wlien tliey 
come from the kiln a finished product, is well known to all clay workers. 
It is a defect peculiar to clay products in greater degree than almost 
any other kind of product. Glass wares, metal wares, cement wares 
etc., deform but little — if they are once formed true, they will remain 
true unless by the intervention of some accidental, exterior force. In 
these products, the finishing of the form is the last stage of the process 
— the iron or the glass or the cement fills its mould, hardens there, 
and generally remains true. 

In clay wares, the forming is followed by two operations upon 
which the permanence of the ware depends — drying and burning. In 
both, the clay changes its volume materially, and in the latter, it changes 
its chemical condition from a mixture of uncombincd and unrelated 
mineral particles, to a more or less uniform, homogeneous solution, 
surrounding such portion of the original grains as still wholly or 
partly retain their mineral identity. 

Obviously, in these profound changes, every opportunity is offered 
to the clay to relieve itself of any strains which may remain from the 
process of forming or passage through moulds and dies under pressure. 



132 BULLETIN ELEVEN 

Also, strains arising from improper balance of the parts of a piece of 
ware, thick portions vs. thin ones, etc., result in strains both in dry- 
ing and vitrification, and if the clay approaches a viscous state in 
firing, these strains naturally tend to relieve themselves. 

Lastly, clay wares of many sorts are brought in firing as near to 
the condition of a viscous fluid as the stability of the shape will in any 
wise permit, and often a little more than is safe. Clay wares in posi- 
tion in the kiln are usually set so that they carry more or less weight — 
frequently very heavy loads — and, under the influence of the incipient 
viscosity, they are deformed at temperatures where a single piece, 
sitting free, would remain true and sound. If a clay ware reaches 
a degree of viscosity when it is no longer able to hold up the load of 
its own weight, sitting free, without deformation, it is usually consid- 
ered as fused, or in a state of viscous fusion. But in this case, all changes 
which take place must be such as a fluid would undergo in attempting 
to assume the horizontal — like a sagging or ^Sviiting^' of a stand of 
sewer pipes, etc. 

Warpage is to be distinguished from fusion only as a matter of 
degree. It must proceed from the viscosity of the clay mass. But it 
may occur in bodies which have not nearly approached the condition 
of viscous fusion. Further, the change of shape may be the reverse 
of gravitational, and the ware may spring in any direction, up or 
down, out or in, under the influence of strains existing in it since 
forming. Third, these changes may take place with but little obvious 
progress of vitrification. Yet in the main, and on the whole, it must 
be believed that it is the viscous condition of the clay, or some portion 
of it, brought about by incipient fusion in burning, which makes warpage 
possible. 

Roofing tiles are i^eculiarly susceptible to warpage. They are 
thin, of large area, and often stand up from the supporting surface in the 
form of arches. They are cheap and must be fired en masse — they 
cannot be accopded individual heat treatment in setting, for their price 
does not warrant it. Hence, every opportunity of structure and treat- 
ment is present in their manufacture and it is not strange that warping 
is a common and almost ubiquitous defect. 

The measurement or systematic study of warpage has been neg- 
lected in previous reports on the clay industry. In a search of avail- 
able ceramic literature, very little could be found that touched directly 
on this property of clay. In the past, the universal practice has been 
to consider warpage as a shrinkage trouble; that is, a clay with a high 
shrinkage would be expected to warp badly. In a general way, this 
may possibly be true, but such a theory leaves very much to explain 
in studying warpage. 

By the term viscosity is meant the degree of fluidity of the clay, 
in flowing or bending while under heat. For instance, tar is said to 



GEOLOGICAL SURVEY OF OHIO. 133 

be a fluid of high viscosity, while water compared to tar is of low vis- 
cosity, and alcohol is of still much lower viscosity than water. In 
silicates, the viscosity of the slag of a charcoal iron furnace is of a high 
order, since it creeps out slowly, inch by inch, over the open hearth, 
and is being broken up and carted away as a glassy solid at the other 
end of the slag-stream, only a few^ feet from the point where it has 
issued from the furnace. A coke blast furnace, on the other hand, 
produces a slag of low^ viscosity, which flows like a fiery torrent through 
the cinder runways, but chills almost at once from a thin fluid to a 
solid. A few per cent, difference in the ratio of silica, alumina and 
lime produce these remarkable variations in viscosity. 

In the same way, clays with a high degree of viscosity would be 
expected to resist warpage, while ones with a low viscosity, i. e., a thin 
fluid fusion, lend themselves very freely to this trouble. On the theory 
that chemical and mineralogical composition are instrumental in this 
defect, the following references were found bearing more or less di- 
rectly on the situation: 

Influence of Feldspar. — That complete vitrification is not neces- 
sary to the development of warpage has been show^n by Day and Allen.* 

The above writers in an attempt to study the viscosity of feldspars 
at their melting point prepared slivers of the feldspars about one by 
two by thirty millimeters. These slender trials w^ere then spanned 
across small empty platinum crucibles, and placed side by side in the 
furnace. These exposed crystals were heated to 1,225° C. for three hours. 
When removed, they were completely amorphous (melted), but re- 
tained their position with hardly a trace of sagging. Other slivers 
were heated in some instances to 1,300° C. for a few moments, and while 
at this temperature a platinum rod w^as inserted through a hole in the 
top of the furnace, and allowed to rest as a load upon the middle of 
the crystal bridge. Under this load, the slivers gradually gave way. 
Slides cut from these trials showed no squeezing out of the melted 
portion between the crystal fragments on the side towards the center 
of curvature, or open cracks on the outer side. On the other hand, 
there was evidence of the bending of the crystals as well as of the 
vitreous portion. 

They further say, with a degree of confidence, that the order of 
magnitude of the viscosity of the molten portion is the same as the 
rigidity of the crystal at these temperatures. 

From the above, it has been shown that while the feldspars had 
completely fused or melted, their viscosity was so high that deforma- 
tion did not take place until a load had been applied. 

While Day and Allen have shown that pure crystals of feldspar 
are extremely viscous, the actions of these same feldspars in connec- 

'Am. J. Sci., Vol. 169, page 93. 



134 * BULLETIN ELEVEN 

tion with a mineral mixture like ordinary clays might be very different. 
In the latter case, the feldspar might have an affinity for some portions 
of the mixture, and form fluid compounds that might possess a low 
degree of viscosity, which in turn might be imparted to the whole mass, 
causing warpage. 

Again, it might be possible, under some conditions, for the glass, 
formed by the fusion of the feldspar, to drain to the lower parts of the 
mass, leaving the upper portion unfused and porous. The well known 
'^liquation'' of platinum-gold alloys, in which the gold drains to the 
lower portion of the mass, leaving a platinum skeleton above, is a case 
in point. The silicate skeleton thus remaining might possess rigidity 
enough to overcome the low viscosity of the fluid matrix in the lower 
sections, and tluis prevent warpage. In this manner, it might be pos- 
sible to have a considerable degree of vitrification in a clay unattended 
by warpage. 

The action or influence of feldspar upon an ordinary clay is un- 
questionably a matter of condition, depending upon the size of the 
grains of feldspar and their relation to the other ingredients. Should 
the feldspar be present in relatively large grains, its influence would 
largely be that of resistance to warpage, while the same quantity of 
feldspar finely pulverized and intimately mixed throughout the mass 
could cause a rapid reduction in the degree of viscosity of the clay as 
a whole. 

Influence of Mica — In the past, mica has in general been con- 
sidered to act as a flux to clays, after the manner of feldspars; it has, 
however, been proved that its action upon clay will depend very largely 
upon the size of the grain. 

Stull* has shown that mica when extremely fine-ground acts as 
a flux upon clay, but not to the same extent as feldspar. In large 
flakes, however, it may act directly opposite. It is not at all uncommon 
to find flakes of mica remaining unaffected in hard-fire biscuit ware, 
proving that in large grains mica does not act as a flux at cone 8. Thus, 
if distributed throughout a clay mass in relatively large pieces, it may 
have a strong action upon the viscosity of the clay by its slowness to 
react with the other ingredients. Mica taken alone requires about 
cone 13 to melt it, as shown by Rieke'. When present in ordinary 
clays or shales, burning at or near cone 1, it is therefore not likely that 
mica assists very greatly in softening the body, but is more apt to increase 
its degree of viscosity, as a sterile ingredient. 

Influence of Alumina* — Purdy' says, **Alumina not only raises 
the actual period at which fusion is completed, but also causes the 

»R. T. Stull, "The Fluxing Power of Mica in Ceramic Bodies." Trans. 
Am. Cer. Soc. Vol. IV., p. 255. 

'Rieke. R. — "The Action of Calcium Mica on Kaolin.*' Sprechsaal, 
1908, 577. 

'Purely. R. C— "Further Studies on White Bristol Glazes." Trans. Am. 
Cer. Soc. Vol. V.. p. 136. 



GEOLOGICAL SURVEY OF OHIO. 



135 



ware made from aluminous clays to soften and deform very slowly. 
The slower softening and deformation of ware made from aluminous 
clays has been attributed to viscosity of the mass caused by alumina." 

The same writer* has shown that the addition of alumina as a 
constituent in a stone ware glaze, up to a proportion of alkali and alka- 
line earths to alumina of 2.5 to 1, not only rendered the glaze more 
fusible, but also less viscous. 

Additions of alumina above this proportional amount, however, 
increased the refractoriness of the glaze, and its viscosity. 

It is a well known fact that additions of alumina in slags and glasses 
above certain limits or proportions will increase their viscosity. 

Frink^ says that glass containing 0.6 per cent, or less of alumina 
will be found to be considerably less viscous than glass which con- 
tains from 3 to 4 par cent, of alumina. Tne Utter glass, due to its 
greater viscosity, will be tenacious and mo.'e desirable to work, and 
will show a less tendency to retain the imperfections of the moulds. 

Thus, the manner that alumina may act upon viscosity will depend 
upon its relative proportion to the other substances present. 

Influence of Magnesia*— In a paper by Hottinger^ it was pointed 
out that magnesite or dolomite added to a shale very greatly widened 
its vitrification range, as shown by the following table: 

TABLE No. 29. 

Hettinger's Experiment on the Influence of Magnesite upon the Fusibility 

of Clay. 



• 


Mixture. 


Absorption. 


No. 


Cone 05 


Cone 1 


Cone 3 


Cone 5 


C 1 
C 2 

C 3 

C 4 

C 5 

C 6 


Shale 100, Whiting 25 . . 
Shale 100, Whiting 12.5 

Shale 100, Magnesite 21. 

Shale 100, Magnesite 10.5 

Shale 100, Dolomite 22 . . 

Shale 100, Dolomite 11 . . 

Shale without additions. 


21.9 
20.4 

32.8 

28.4 

22.4 

17.7 

12.0 


Melted . . 
Vitrified . . 

7.3 

0.32 
11.5 
12.1 

0.78 


Melted . . 
Melted . . 

Vitrified . . 

Vitrified.. 

/Partially 1 
\melted. J 

Blistered 
Blistered 


■ 

Melted. 
Melted. 

/Shape 
Iretamed. 
/Slightlv 
\swelled 

Melted. 
Melted. 



»Purdy, R. C— Illinois Geol. Survey, Bull. IX. p. 217. 

^Frink, R. L.— ''The Effect of Alumina on Glass." Trans. Am. Cer. Soc. 
Vol. XI. p. 99. 

Hottinger, A. F. — "The Influence of Magnesia on Clay." Trans. Am. Cer. 
Soc. Vol. V, p. 130. 



136 BULLETIN ELEVEN 

From the preceding tab'e it is evident that mixtures C3 and C4 are 
strongly viscous, though vitrified completely. At cone 5 they have 
retained their shape, while mixtures of the same shale with whiting 
melted completely at a lower temperature, and with dolomite the action 
was intermediate in severity. Hottinger further says, in reviewing 
the previous work of Mackler* on the same subject, that clays carrying 
high magnesia can be made into wares of extreme length, with very 
thin, walls, which may be very nearly vitrified, and still be kept per- 
fectly straight and true. Also, the district in which Mackler made 
his first observations on the effect of magnesia was a roofing tile district, 
and the tiles produced from the clays of one part of the district warped 
badly, while clays from the other part of the district did not. Mackler 
found the magnesia content to be the only important difference in 
composition, and later verified by synthetic experiments the role of 
magnesia in reducing warpage. 

It is believed that these results are due to- the extreme viscosity 
of the magnesium silicate compounds, which allow a more complete 
vitrification without failure. 

That many red-burning clays and shales in this country contain 
magnesia in various quantities, even up to several per cents., is a well 
known fact. Thus, it is quite possible that magnesia is playing a larger 
part in the prevention of warpage than is commonly supposed. 

Influence of Lime* — The influence of lime upon the warpage of 
a clay will be dependent upon its size of grain and distribution. When 
present in lump or granular form, it is not probable that it assists warp- 
age any more than any other particles, but when incorporated through- 
out the mass in large quantity and a finely divided state, it tends to 
keep the body porous and to delay shrinkage and vitrification and to 
hold the body free from warpage up to the point where combination 
begins. From thence, it causes the body to soften with extreme rapid- 
ity. Such warpage as occurs in this connection is palpably that of 
imperfect fusion. 

In clays containing small amounts of lime (5 to 10 per cent.) finely 
divided and evenly distributed, its action is towards early fusion and 
rapid failure. The action is the same in quality, but the temperature 
at which it occurs depends on the quantity of lime, being low for low 
lime, or high for high lime. 

Experimental Work on Warpage — With the foregoing general knowl- 
edge of the trade conditions as to warpage, and the theoretical discus- 
sions just quoted as to suggested relationships between mineral composi- 
tion and warpage, some practical tests of the relative warpage of actual 
roofing tile clays was taken up. No records of any actual measurements 
or tests of warpage could be found, and therefore the method of inves- 

^Mackler, Dr. H. Influence of Magnesia on the Behavior of Clays, 
Tonindustrie-Zeitung, Vol. 26, II, p. 705. 



GEOLOGICAL SURVEY OF OHIO. 137 

tigation was necessarily entirely original and tentative. A large amount 
of the work which has been done in the testing of the standard roofing 
tile clays has been directed to the measurement of this property, so 
as to be able to pick out those clays which warp, or tend to warp, badly. 
Three separate experiments were made upon each clay in the series, 
excepting and L, of which the supply of clay secured was insufficient. 

First Experiment on Warpage. — It was thought that much could be 
told of the likelihood of the clay to warp by making thin flat tiles or quar- 
ries, and burning them upon flat surfaces, and noting the amount of 
"dishing," i. e., the curling up of the sides of the tiles, forming a shallow 
concave surface. 

For this test, tiles one-half inch by four and one-fourth inches 
by four and one-fourth inches were made, by batting out blanks of 
approximately the correct thickness, then cutting them to a size that 
would just enter the die of a screw-tile press. The blanks were care- 
fully pressed, especial attention being paid to getting them all as nearly 
of the same thickness as possible. 

After pressing, the tiles were carefully placed upon selected straight 
boards, or pallets, where they were left until completely dry before 
handling, in order that no undue strains might be introduced/ When 
these tiles were dry, they were set upon especially selected fifteen inch 
by twenty inch fire clay slabs, and placed in the chamber of a coke-fired 
down-draft kiln having a capacity equal to about 300 bricks. In order 
to obtain as much dishing as possible, it was thought best to place these 
trial pieces in the upper part of the chamber, where they would receiye 
the direct action of the heat. 

In order to learn the time at which warpage occurred, a series of 
four separate burns was carried out, finishing at cones 09, 07, 04 and 01, 
respectively. It was the intention to sta> within the workable temper- 
ature limits of the clays, hence no burns were made above cone 01. 

The time spent upon each of the four burns was about thirty hours. 
While more time would possibly have been better, it was firmly believed 
that the most severe test to which a badly warping clay can be put is a 
short, rapid firing, which does not give time for proper equalization 
of the strains. 

After assembling the trials from the four burns, they were studied 
to note their amounts of dishing. Instead of being "dished," they were, 
with very few exceptions, "bowed" — that is, the center of each tile 
had raised or drawn up, while its sides or edges rested upon the fire clay 
slab which formed the floor. 

In order to measure the amount of "bowing," a shallow, open- 
topped box a little larger than the tile was taken, and over the top from 
side to side a fine silk thread was stretched taut. A tile was placed in 



138 BULLETIN ELEVEN 

the box, with the convex side up. Then, with a millimeter scale grad- 
uated to 0.25 mm., a direct measure was made from the thread to the 
center of the convex surface and then to the two edges directly under 
the thread, thus obtaining a difference in reading, dependent upon the 
amount o** convexitv. 

In order to compare the amount of dishing or bowing in the different 
clays, all measurements were figured in per rents of the total distance 
from the silk thread to the box — that is, the measurement from the 
thread to the top of the tile was subtracted from the total depth from 
thread to the floor of the box. This amount was divided by the total 
depth, this quotient multiplied by 100, giving the figure in per cents of 
the total distance. 

While it was assumed that the tiles were all of one thickness, it is true 
that there were slight differences due to the differences of shrinkage, but 
no allowance was made for this. 

On tabulating these data, (Table 30) it was observed that clays which 
were known to warp badly in actual practice gave here different results 
under different heat treatment. For instance, clay G has at cone 07 
bowed 1.56 per cent., at 04 it is straight, and at 01 it developed a dishing 
of 6.25 per cent. In other words, it would appear that at cone 04 the 
flay has so softened that it has straightened out, and yet at a higher 
heat it curled again in the opposite direction. In clays L, N, K, G, B, 
M and C there have develoiK*d l»oth dishing and bowing of the trials. 
Just what conditions prevailed in the tiles or in the filing to pro- 
duce such irregular results cannot be said. 

There appears to be very little relation between shrinkage and 
warpage, as shown by clays A and E against clay G. The two clays 
A and E have a relatively high total shrinkage, and have remained 
straight, while clay G, having a rather low total shrinkage, has developed 
c^nsidirable warpage. Clay B, with a very low shrinkage, has warped 
to a considerable degree at the higher temperatures tested. 

In a general way, it will be seen that those clays which warp badly 
in this test, such as J, K and L, warped badly in the succeeding tests, 
also. But this test did not seem to give a satisfactory expression to the 
tendency of clays to warp, and another test was devised to take its place. 

Secx>nd Experiment on Warpage* — Much trouble results from a dif- 
ference in the burning shrinkage of the two ends of auger-made Spanish 
tiles. The cause of the trouble is due largely to the method of setting 
the tiles in the kiln. As stated elsewhere in this report, auger-made 
Spanish tiles are set standing on end, in open fire-clay boxes or saggers. 
After burning, the end of the tile that was down is very oftfen found to 
be larger, and its curvature more flattened out, than the end which was 
uppermost. The cause of this is the restriction of the shrinkage by 
friction against its supporting surface, while the upper end had perfect 
freedom to shrink or warp without restraint. It was thought worth 



GEOLOGICAL SURVEY OF OHIO. 



139 



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140 BULLETIN ELEVEN 

while to make this industrial difficulty the basis of a test of the conipara- 
tive warpage of different clays. A set of trial pieces was prepared, of 
such shape and thickness that it was thought that the clays Hkeh' to 
to give trouble in practice would be sure to develop it. These trial pieces 
were made in the form of half-round tiles, or semi-cylindrical troughs, 
three and one-fourth inches long, with an outsi<te diameter of three inches 
and one-fourth of an inch thick. They were made by pressing the clay 
by hand in plaster molds, much care being taken to produce them free 
from flaws. In order to prevent their becoming distorted while drying, 
pallets were made, upon which cleats were nailed just far enough apart 
to allow the sides of the half-rounds to stand between them. They 
were thus prevented from spreading or settling down while plastic. 

After thoroughly drying, the trial pieces were carefully measured 
at each end, one end being marked. The trials were then set in the kiln, 
each standing free from its neighbor on a smooth fire-clay slab. 



;nd Second Warpage Experim 



It was thought that the upper or free end would draw in, while the 
lower end, due to Its friction on its support, would be prevented from 
doing so, and thus giving a measurement of warpage. The trials for 
this test were burned in the same manner, at cones 09, 07, 04 and 01. 

After obtaining the trials from the four separate burns, they were 
again carefully measured at both ends. Then dividing the difference 
between the unburnod and the burned measurements by the initial 



GEOLOGICAL SUBYEY OF OHIO. 



141 



width, and multiplying by 100, gives the per cent, of contraction in 
width. As will be seen in table No. 31, there is in most cases a 
marked difference betw^een the per cent, of contraction of the lower and 
upper ends. 

This experiment would, no doubt, have proved more successful if 
the trial pieces had been made much larger and longer, increasing the 
load upon the low^er end, and thus making the resistance to warpage 
greater. The thickness of the walls of the trial pieces should also have 
been increased, to prevent their bulging out. In the majority of the 

TABLE No. 31. 

Showing Results of the Second Warpage Experiment on the Standard Roofing 

Tile Clays. The Difference in Contraction of the Free and 

Restrained Ends of Half-round Tiles. 



T^ — . — . ' A ? _ - 


Cone 09 


Cone 07 




Designation 














Average. 


of Clay. 


Per cent. 


Per cent. 




Per cent. 


Per cent. 






Contraction 
Upper End 


Contraction 
Lower End 


Difference. 


Contiaction 
Upper End 


Contraction 
Lower End 


Difference. 






, of Tile. 


of Tile. 




of Tile. 


of Tile. 






A 


1.59 


1 

1.59 i 


0.00 


' 2.63 


1.82 


1 
0.81 




B 


0.6SI 


0.139« 


0.541 


j 0.83 


0.27^ 


l.lt) 




C 


0.972 


0.110 


0.862 


3.01 


2.31 


0.70 




D 


0.4S1 


0.278 , 


0.203 


0.27^ 


0.69' 


0.42' 




E 


0.744 


0.604 : 


0.104 


0.59 


0.89 


0.30' 




F 


1.25 


1.06 


0.19 


1.09 


1.91 


0.82' 




G 


0.55 


0.41 


0.14 


1.32 


1.87 


0.55' 




H 


0.291 


0.298 


0.007' 


2.36' 


2.21 


4.57 




I 


0.41' 


0.55 1 


0.96 


0.70' 


0.27 


0.97 




J 


3.35 


4.58 


1.23' 


1.54 


1,12 


0.42 


^ 


K 


3.38 


2.54 


0.84 . 


5.15 


1.77 


4.38 




L 


2.59 


1.45 


1.14 


4.57 


2.34 


2,23 




■ M 








0.82 
3.43 


0.13 
3.83 


0.69 
0.40' 




N 


"" 5.20^ 


5.28^" ' 


0.08^ 






Cone 04 


Cone 01 




A 


8.13 


6.57 


1.56 


9.41 


4.48 


4.93 


1.82 


B 


2.06 


1.51 


0.55 


3.90 


3.01 


0.89 


0.512 


C 


16.32 


12.06 


4.26 


9.27 


9.33 


0.06' 


1.470 


I) 


8.31 


2.84 


5.47 


1.75 


1.62 


0.13 


1.55 


E 


0.86 


0.714 


0.146 


4.83 


3.94 


0.89 


0.038 


F 


3.71 


1.65 


2.06 


7.92 


6.52 


1.40 


1.117 


G 


6.07 


4.84 


1.20 


4.41 


0.666 


3.75 


1.41 


H 


0.00 


1.16' 


1.16 


3.91 


3.24 


0.67 


1.60 


I 


1.25 


1.67 


0.42^ 


2.13 


1.43 


1.70 


1.01 


k 


16.94 


15.05 


0.89 


0.43 


5.78 


5.35' 


1.97 


1.30 


2.32 


1.02' 


13.46 


7.91 


5.55 


2.94 


L 


6.58 


4.76 


1.82 


4.01 


3.76 


0.25 


' 1.36 


M 


0.S2 


1.51 


0.722 


5.79 


0.41 


5.38 


2.26 


X 


1.16 


0.57 


0.59 


0.54 


0.24 


0.30 


, 0.34 



' Expansion, in.stead of contraction. 

' Per cent, that the bottoms have contracted in excess of the tops. 



142 BULLETIN ELEVEN 

cases where a greater contraction of the lower end than the upper was 
shown, it was due to the sides bulging out and spreading the upper end, 
while the lower end was held by friction from doing so. Again, it is 
quite possible that the personal factor in pressing such thin sections has 
played an important part in causing irregularities. 

In studying the results of the second warpage trials it will be seen 
from the column of averages in the table that clay K has shown the 
greatest degree of difference between the two ends of the trials, pointing 
out this clay as the one most likely to give trouble from warpage. The 
results of this test on clay K have been confirmed by both of the other 
warpsge tests. 

In a comparison of the fire shrinkage and warpage, it is very 
clear from the behavior of clays K and C in thi5 method of testing, 
that there is no relation between the numerical values of the properties 
in different clays. Clay K has a fire shrinkage at cone 01 of about 9 
per cent, and has shown a warpage of 2.94 per cent. Clay C at cone 
01 shrinks in the neighborhood of 8 per cent, and only shows a warpage 
of 1.47 per cent., or just one-half that of K. 

Clays C, D, G, H and I show very similar warpage in the above 
test, and these same clays have fallen quite closely together in the two 
other tests for warpage as well. Clays M and B give erratic results 
in this test. It is believed, in the light of the third w^arpage test, that 
the figures for these clays are not representative, and that B and M 
should be classed with clays like C and D, while B as here shown belongs 
with clays E arid N, and M with K. The clays E and N show a very low 
degree of warpage, but their high lime content, their slow vitrification 
habit, their porosity until nearly ready to fuse, and the suddenness of 
their fusion when it once begins, all show that their behavior would 
not be like the vitrifying clays composing the rest of the series. 

All things considered, the second method seems to have but little 
advantage over the first, and neither arc satisfactory. 

Third Experiment on Warpage*— The third experiment more 
nearly approaches a correct method for measuring the warpage ten- 
dency of clavs than does either of the others tried, and it is believed 
than any other method known at the present time. It consists in 
supporting a long bar of clay on knife-edges in the kiln and measur- 
ing the amount and rate of sag developed in burning. 

It is believed that Dr. K. Cramer, of Berlin, Germany, was the first 
to use this method in the study of clays. The Holdcroft thermoscope, 
a patented English pyrometric device, closely resembling the German 
Seger cones in composition, uses exactly the same principle in its 
test bars, which are laid horizontal on supports, and which betray 
fusion by sagging, instead of curUng over as the triangular pyramids 
called "cones" do. It is not known, however, that this idea has 



GEOLOGICAL SURVEY OP OHIO. 143 

ever been used in this country prior to this investigation, or for this 
purpose. 

The work as carried out consisted in passing the previously tem- 
pered clays throuf!;h the Mueller auger machine and out through a fiat 
shingle die, in a bar ono-half inch thick by six inches wide. As the 
bar of clay issued, it was cut crosswise into thirteen-inch lengths, which 
in turn were cut lengthwise into strips one and one-fourth inches wide 
by thirteen inches long, after being placed upon a pallet. No handling 
of the small thin strips of clay after cutting was necessary. Much care 
was taken to select perfectly straight pallets upon which to dry these 
bars. In order to avoid drying strains as much as possible, the trial 
bars were all carefully dried in an open room until they were white- 
hard, after which they were placed in a drying-oven while still on the 
pallets. When dry, they were taken to the coke-fired down-draft kiln 
mentioned Ixjfore, and placed for firing. It is in the method of setting 
that the real test of the ciay consists. 



Fig. 33— Method of Setting Warpage Trials on Supports. 

From the above cut it will be seen that the trial bars were set upon 
fire-clay knife-edges (previously burned) placed 10 inches apart, center 
to center. The trial bars, which had been thirteen inches long when 
first cut, were for the most part about twelve inches long at the time 
ui setting. Hence, with the knife-edges ten inchts apart, there was 
an overhang of about one inch at each end for every bar. Two trial 
bars of each clay were set for each burn. While purposely not placed side 
by side, the two, trial l)ars gave closely concordant rcsuKs in every 
instance. In the four burns made, at cones 09, 07, 04 and 01, roK- 



144 



BULLETIN ELEVEN 



pectively, it was the intention not to overfire any of the clays and keep 

within commercial temperature ranges for all of the different clays. 

These test bars, one-half inch thick by one and one-fourth inches 

wide by ten inches long between supports and twelve inches, more 



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Fig. 34 — Drawing Showing Sagging or Warping of Clay Bars at Different 

Temperatures. 



GEOLOGICAL SURVEY OF OHIO. 145 

or less, over all, naturally tended, on softening from the heat, to sag 
down in a more or less perfect arc of a circle, of which their original 
position formed the chord. The idea of the experiment Was that 
the amount of the sag would afford a numerical index of the warping 
tendency. 

In measuring the trial bars, it was assumed that they went into 
the kiln perfectly straight, i. e., with per cent, warpage. The degree 
of sagging found after burning was measured by taking a thin flat rubber 
band and stretching it tightly from end to end of the tile across the 
intervening space like the string to an archer's bow, as shown by the 
dotted lines in Figure 34. Then by means of calipers graduated to 
the second decimal place, the distance from the under side of the taut 
band to the upper surface of the tile at the point of greatest deflection 
was taken, thus giving a direct measure and comparison of the warpage 
in the different clays. 

After taking the above measurements, a two-inch piece was care- 
fully broken from one end of each trial bar, and the porosity was de- 
termined with great care by the methods given in that connection. 

The tables to follow have been prepared by taking the average 
of the two results for each clay for each burn, for the degree of warpage 
and for the per cent, porosity. The linear shrinkage figures were not 
available at cones 09, 07 and 01, and were interpolated from the table 
given under the head of ''Fire Shrinkage." For cone 04 the observa- 
tions required no interpolation. 

In the above cut, the trial pieces are represented in their different 
degrees of warpage from a straight line at the four heat treatments, 
cones 09, 07, 04 and 01, respectively. 

Clays E and N have deformed the least and at a slow rate. Clays 
K and J developed a very high warpage and at a rapid rate, i. e., the 
increase from cone to cone was decided. Clay A shows a warpage 
equal to J or K, but there has not been a decided failure of this clay 
as in clays J and K. It will be noted that they have sagged in irregular 
curves, while A has sagged in a very regular manner. Clay K was ob- 
served to deform badly by the time that the kiln had reached a dull- 
red heat, indicating very early chstnges under fire. The discrepancies 
of clay K in this and other tests bsfore reconled, compared to the 
other clays tested, are probably due to the fact of its very early vitri- 
fication. Its curves of porosity, shrinkage and specific gravity are not 
different from the other curves in kind or contour, but the latter half 
of its vitrification period falls in the same temperature zone that wit- 
nesses the first half of the vitrification in the other clays. The result 
is that it seems all out of joint with the others. Without doubt, its 
full curves would be more normal in contour if our observation had 
begun at 750^ C. instead of 950° C. (cone 010). 

10— G. 13. II. 



146 



BULLETIN ELEVEN 



In the following tables are given the warpage as determined by 
this method. In addition, the fire shrinkage and porosity are given 
to facilitate comparisons. 



* 



TABLE No. 32. 

Shosing Results of Third Warpage Test on the Standard Roofing Tile Clays^ 
with Results of Fire Shrinkage and Porosity Tests Added for Comparison, 





Temperature of Different Bums. 


Designation 
of Clay. 




Cone 09 




Cone 07 




Per cent. 

Fire 
Shrinkage. 


Per cent. 


Measure of 


Percent. 

Fire 
Shrinkage. 


Per cent 


Measure of 




Porosity. 


Warpage. 


Porosity. 


Warpage. 


A 


0.55» 


26.49 


5.27 


0.55 


21.71 


11.80 


B 


0.12 


26.24 


5.57 


0.87 


19.26 


12.55 


C 


0.45 


32.72 


5.95 


1.25 


28.44 


10.92 


D 


0.05^ 


31.79 


7.47 


0.10 


32.20 


10.87 


E 


0.20* 


39.54 


0.00 


0.30» 


29.01 


1.80 


F 


0.55» 


31.05 


8.10 


0.05 


30.11. 


11.22 


G 


1.00 


25.28 


8.50 


2.87 


23.83 


11.12 


H 


0.20* 


31.03 


1.87 


0.10 


30.35 


3.02 


I 


0.50 


30.07 


5.87 


0.50 


29.90 


12.00 


i 


1.50 


16.81 


8.40 


3.00 


10.56 


20.10 


3.24 


16.27 


17.75 


5.19 


10.19 


37.95 


M 


0.25» 


30.96 


6.10 


0.55 


28.03 


10.15 


N 


0.00 


• 36.32 


1.32 


0.00 


36.13 


1.62 




CONE 


04 




co: 


NE 01 




A 


5.15 


7.57 


38.02 


6.10 


5.75 


47.15 


B 


2.00 


11.81 


29.50 


2.25 


11.74 


42.00 


C 


6.00 


11.86 


36.75 


7.20 


8.81 


47.15 


D 


3.50 


28.74 


21.82 


5.62 


23.01 


41.30 


E 


0.20 


38.34 


2.47 


2.20 


34.88 


8.60 


F 


3.35 


22.42 


24.95 


4.52 


18.91 


41.55 


G 


4.50 


12.75 


32.15 


5.25 


10.70 


41.55 


H 


1.70 


29.20 


8.27 


2.90 


26.02 


24.80 


I 


0.50 


31.29 


15.02 


0.62 


25.13 


25.40 


i 


5.50 


2.99 


35.50 


5.75 


2.82 


61.15 


7.79 


6.65 


37,30 


5.89 


2.78 


62.00 


M 


1.55 


25.73 


19.25 


2.42 


22.26 


40.50 


N 


0.50 


37.91 


4.55 


1.50 


37.57 


5.75 



These results have been plotted in the following curve sheets (pages 
147-150). For convenience in observing, the warpage and fire shrinkage 
are made to read down the page, while the porosity reads up. By this 
expedient, all the curves are made to traverse the paper in the same 
direction. Also, the scale selected for each kind of data is different, 
and is chosen to make the curves change elevation at about the same 
rate in the average case. If one property changes faster than another, 
the curves immediately diverge. 



GEOLOGICAL SURVEY OF OHIO. 



147 




^ 07 ^S 



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Fig, 35^ Warpage- Porosity-Shrinkage Comparison for ClayJA. 




Fig. 36 — Warpage-Porosity-Shrinkage Comparison for Clays B and C. 



148 



BULLETIN ELEVEN 




oo tf or a» 0f 



0r as as Cf 



Mf 



Fig. 37 — Warpage-Porosity-Shrinkage Comparison for Clays D and E. 




99 



fi7 CS CiS at 



o9 cr as OS ^ 



Fig. 38 — Warpage-Porosity-Shrinkage Comparison for Clays F and G. 



GEOLOGICAL SUBVEY OF OHIO. 



149 



,S» 




o» 



or ax aj at "09 ^^ Sr 2# "ST 



Fig, 39 — Warpage-Porosity-Shrinkage Comparison lor Clays H and I. 




Fig. 40 — Warpage-Porosity-Shrinkage Comparison for Clay J and K, 



150 



BULLETIN ELEVEN 



#^ 




Fig. 41 — Warpage- Porosity-Shrinkage Comparison for Clays M and N. 



A careful studv of these curves reveals the close relation which 
exists between the changes of volume and the changes of form. This 
is as has been assumed and expected, but up till the present no proof 
had been submitted, so far as is known. 

There are, it is true, some puzzling inconsistencies in the data. 
These inconsistencies largely come, no doubt, from the fact that we are 
dealing with a very small number of trial pieces, and, as is well known, 
shrinkage data are notoriously erratic and can only be accepted as of 
much weight when they are the mean of a large number of determina- 
tions. The wonder is, therefore, not that there are inconsistencies, but 
that so much consistency can be gotten out of such a limited amount 
of material. 

The three kinds of curves in clays A, C, E, G and N show a marked 
concurrence in direction and rate of change. No one, after looking at 
them, can fail to be struck with this fact. Clays A, C and G are all 
clays which shrink rather highly, decrease in porosity rather sharply, 
and warp rather evenly, but in considerable amount. Clays E and N 
are calcareous clays, which do not enter their active vitrification pro- 
cess in the temperature zone studied, and therefore neither warp nor 
shrink nor grow dense. They prove nothing,- either pro or con, in this 
discussion. 

In the clays D, F, H, J, K and M, we find again a marked concur- 
rence between the rates of fire shrinkage, porosity extinction, and warp- 



GEOLOGICAL SURVEY OF OHIO. 151 

age, in the earlier portion of the temperature zone studied. Between 
cones 09, 07 and 04, the concurrence in direction and rate of change is 
marked. But between cones 04 and 01 , the warpage consistently changes 
faster than the other properties do. 

This might be construed as weakening the contention that warpage 
is a function of the vitrification process, and controlled by the same 
actions that control shrinkage and porosity, but in fact it strongly 
verifies and supports it. If we consider warpage as being the result of 
incipient fusion of the clay — the development of a viscous taffy-like 
material in the clay body, not sufficient in amount to cause the clay to 
actually liquify and lose its shape at first, but growing gradually in 
amount and fluidity as the temperature rises, until in the end it does 
cause the resistant frame-work of the clay to slump and the clay to 
fuse — then the increase of warpage more rapidly than the parallel 
changes in either shrinkage or porosity is the normal thing and 
should be expected. 

We know that, as the porosity of an ordinary clay is extinguished, 
the rate of change becomes less and less with each increase of 
temperature. The progress goes on rapidly when the porosity is high, 
but gets slower and slower as it approaches the maximum density. 
Similarly with fire shrinkage. The maximum, in good clays at least, 
is reached by a series of slow approximations, followed by slow bloating, 
and the volume curve runs nearly horizontal for a time. But, while 
the last of the shrinkage and porosity are gradually taking place, the 
viscosity or incipient fusion is all the time gaining in force and power. 
Naturally, as the temperature rises to more and more critical points, 
do the warpage and deformation increase.. It would be seen to in- 
crease still faster in proportion, if the temperature zone studied in this 
work had covered a still higher range. Curves D, F, H, J, K and M, 
therefore, represent the same thing as curves A, C, and G, except that 
they have gone a little further toward fusion, and the deformation be- 
tween 04 and 01 has made more headway in the former than in the latter 
three. This is especially clearly distinguishable in clay J. Here we 
have the most complete extinction of porosity, with high fire shrink- 
age, that we have in the available data, and with it we get the highest 
deformation, and the most marked increase in rate of warpage when the 
other properties have ceased to change. In K, bloating has begun at 
cone 01, and this destroys the symmetry of the curves, though it would 
explain the high warpage. 

In two of the thirteen clays examined, viz., B and I, we find the 
situation less easily read. B is remarkable only in its very low shrink- 
age. Its porosity curve and its warpage behavior are strictly concord- 
ant with most of the other samples tested. But how a clay can show 
such evident signs of viscosity with so little fire shrinkage is not under- 
stood. 



152 BULLETIN ELEVEN 

In clay I, the curves indicate that the vitrification process was 
quiescent up to cone 04, neither fire shrinkage nor reduction of the 
porosity occurring. During this time a moderate or small warpage 
took place. At cone 04, porosity suddenly decreased, concurrent 
with warpage, but the fire shrinkage was still not affected. It is 
probable that a study of these clays over a wider temperature zone 
would assist in understanding their behavior. 

From the foregoing, we may present the following general deduc- 
tions: 

First — Change of shape in the burning of a clay ware is a function 
of the vitrification process, and results from the formation of a viscous 
silicate matrix, while the principal part or skeleton of the clay is still 
solid. 

Second — The changes of shape which occur early in the burn, while 
the clay ware still retains its general shape and usefulness, and those 
late changes from overfire which destroy the shape for commercial uses, 
are stages of one and the same process. 

Third — Changes of shape are found to begin at temperatures far 
lower than was expected — a low red heat in one instance. In general, 
these changes are insignificant below cone 010. 

Fourth — The rate of change of shape in normal clays is closely 
parallel to the rate of the other vitrification changes (shrinkage, porosity 
etc.) for a time. In most of the clays tested, this parallel lasted to cone 
04 and in several to cone 01. But as the rate of shrinkage and porosity 
changes decreases on approaching completion, the rate of change of 
shape increases, so the curves do not remain concurrent at higher tem- 
perature s. 

Fifth — The tendency to warpage and the absolutt^ amount or 
nunierici 1 value of the warpage of a clay at any given temperature are 
inherent properties of the material, and do not admit of prophecy: 
i.e., knowledge of the behavior of one clay docs not justify us in assuming 
what the next clay will do. Warpage stands on the same plane in this 
respect as the other properties of a clay. Nor can warpage be correlated 
at all closely in numerical amounts with the shrinkage, porosity, or 
other properties of the clay. For instance, two clays of equal warpage 
may or may not agree closely in shrinkage or porosity. Likewise, 
clays having the same shrinkage or porosity may or may not have 
similar w^arpage. Also", while high shrinkage and low porosity incline 
us to expect high warpage, it does not always follow — the relation is 
only a general one. 

Sixth. In studying warpage of clays for commercial applications, 
trial pieces covering the entire temperature range from cone 010 or below 
up to the point of complete maturity or slight overfire should be se- 
cured, in order to determine the critical point where the deformation 
begins to take place at a faster rate than the concurrent changes in 



GEOLOGICAL SURVEY OF OHIO. 153 

shrinkage and porosity. This point indicates where the warpage may 
be expected to become severe. 

Seventh, In estimating the value of clays for roofing tile purposes, 
or for making any thin-walled wares, the determination of the warpage 
tendency is a practical test, second in importance only to color and 
vitrification range. 

SUMMARY. 

In deciding on the clay to be used in a new enterprise, where all 
the data have l^een obtained that can be obtained as to its properties, 
a decision must be reached as to whether to accept or reject it. Enough 
has been shown in the foregoing series of tests to show that very rarely 
is any clay tested of which the properties are all favorable. Some defect 
is almost certain to be present. The question is where to draw the line 
between defects which are fatal and those which can be overlooked in 
consideration of the counterbalancing good properties. 

In Table 33 (pages 154-165) the net results of the preceding tests 
have been reduced to their simplest expression and a decision charac- 
terizing the clay as a whole has been reached. This may be of use as 
an example for others attempting a similar judgment on similar data. 



1)4 



BULLETIN ELEVEN 



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GEOLOGICAL SURVEY OF OHIO. 



157 



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GEOLOGICAL SURVEY OP OHIO. 



159 



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GEOLOGICAL SUKVEY OP OHIO. 



161 





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apid 
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U— G. B. 11. 



162 



BULLETIN ELEVEN 









a 








O 




4) 




7-4 




■ »^ 




H 




bo 


• 


d 


TJ 


■<d 


9i 


o 


S 


o 


d 


f^ 


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d 


-o 


o 


-0 




d 


CO 


<4J 


CO 


C/3 


• 

o 


V 


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d 
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to 


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0) 


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1 


If slipped and 
worked as a 
porous product, 
the mixture is 
not undesirable 
except on 
account of its 
easily exceeded 
overfire limits, 
and its warpage. 
The latter is 
known from the 
high warpage ^f 
its three 
ingredients. 


Standing of the Burnt 
Clay Within the Useful 
Color Range. Compar- 
ative Amounts or 
Effects. 


Satisfactory. 

Quality is poor at all 
temperatures. 

Steel hard or just be- 
low. 
High. 22%-16%. 

Not favorable. 
Moderate 8%-10%. 
Cannot be favorable. 
Unfavorable. 


bo 

c 

s 

u 
3 

> 


ho 

c 

"c 

u 
3 

w 

c 

o 

o 

« 

& 


• 

Moderately rapid. 

Changes between 06 and 1 are 
slow. 

Changes slowly. 

Changes very gradual. Rate 
per cone 1.48%. 

Body begins to fail rapidly at 02. 

Changes steady and small. 

Not measured. 

Very narrow range. Easily 
spoiled. 


Prooertles of the 
Burnt Clay. 


Oxidation. 
Color. 

Hardness. 
Porosity. 

Specific Gravity. 
Shrinkage. 
Warpage. 
Overfire. 


Properties In the 
Raw State. 


Water required 

for Plasticity: 

Moderate, 

17.21%. 

Shrinkage in 

Drying: 

High, 6%. 

Strength in 
Dried Condition: 
Not determined. 


'dldui 
uopBi 


Bg JO 
[JJ8IB8Q 


»J 



GEOLOGICAL SURVEY OF OHIO. 



163 





w 




ts 




rt 








O 




o 








•.^ 




H 




bo 




c 


TJ 


«a 


Q) 


o 


d 


o 




Pi 


4-» 

G 
O 


-0 

u 

c6 


O 


•o 




a 


CO 


c6 

•4^ 


CO 


cri 


• 

o 


U 


:^ 


4-> 


Px3 


o 


n 




< 




H 


H 




Umt 




o 




>. 




(h 




rt 




6 




B 




3 




C/3 



• 

C 

be 

»-> 

"3 

c 


A desirable 
material. 
Will make 
a rather 
porous tile 
of moderate 
warpage. 


Standing of the Burnt 
Clay Within the Useful 
Color Range. Compar- 
ative Amounts or 
EfTects. 


Satisfactory. 

Quality good. 

Hard enough. Below 

steel. 
High. 28%-22%. 

Favorable. 

Low. 5%-7%. 

Below average in 
amount.21%-39%. 

Favorable. 


bo 

c 

c 

u 

PQ 
c 


bo 

c 

£ 

3 

c 

£ 
O 

o 


Moderately rapid. 

Changes slowly between 06-1. 

Changes rapidly at cone 02-1. 

Changes rapidly between 02-3. 
Rate per cone 6.02. 

Begins to fail slow^ly at cone 1. 

Changes slow and small. ' 

Regular. 

No overburning for several cones 

• 


Properties of the 
Burnt Clay. 


Oxidation. 
Color. 
Hardness. 
Porosity. 

Specific Gravity. 

Shrinkage. 

Warpage. 

Overfire. 


Properties in the 
Raw State. 


Water required 
for Plasticity: 
Low, 15.86%. 

Shrinkage in 

Drying: 
Low, 3.5%. 

Strength in 

Dried Condition: 

Below Average. 

4.79 lbs. 


*9ldU] 

uon^i 


«S JO 


^ 



164 



BULLETIN ELEVEN 



CO 

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to 

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a 

CO 



c 
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bo 

p 



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E = s 

» « St- 
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bo 

c 

c 

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> 

JC 



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d 



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bo 

c 

O 



o 



0) 



O 

OQ 



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165 BULLETIN ELEVEN 



CHAPTER IV. 

THE PREPARATION OF ROOFING TILE CLAYS. 

The processes to be considered in this chapter include all that deal 
with the winning of the clay, its transportation to the plant, its grind- 
ing, the production and increase of plasticity, its aging and its chemical 
treatment to avoid efflorescence. 

In discussing these topics it has not been the intention to write a 
text book on all known methods of clay preparation, which would carry 
the book much beyond the proper limits, but to state somewhat fully 
how the roofing tile manufacturers are now actually solving their sev- 
eral problems, in the belief that a discussion of these facts may be of 
more use to roofing tile makers, present and prospective, than the more 
general treatment. 

VARIETIES OF CLAYS USED* 

The discussions of the preceding chapter on the clays used in roofing 
tile manufacture in this country have made clear their physical and chem- 
ical properties, and their origin, or geological occurrence, has been made 
known. In connection with the preparation of clays, it is again desir- 
able to consider their varieties. 

If the occurrence of the clays now actually in use in American roof- 
ing tile plants be tabulated, w^e \vi\\ find as follow^s: 

(1) Glacial clays, containing a considerable quantity 

of stone and lime . . . . ^ 1 plant 

(2) Alluvial or river flood-plain and lake-bottom clays, 

containing sandy streaks, but practically no 

stones or coarse impurities 3 plants 

(3) Shale beds, accessible for superficial workings .... 9 plants 

(4) Shale beds, under heavy cover, and requiring min- 

ing operations 1 plant 



14 plants 



So far as winning is concerned the first two groups may be lumped 
together, as the modes of operation are in general the same. The super- 
ficial shale beds make a group by themselves, differing from the first 
two chiefly in the difference in hardness of the clay and the use of ex- 
plosives to loosen it. A third mode of winning is represented in the 
single case of mining an underground vein. 



GEOLOGICAL SURVEY OF OHIO. 167 

- WINNING ROOFING TILE CLAYS. 

By winning is meant the operation or work performed in loosening 
a mineral from its natural bed and loading it ready for removal to its 
next destination. In many places the transportation and delivery of 
the material to its next destination are considered as a part of the defi- 
nition of W'inning, but it seems better in the interest of clearness to keep 
these matters separated. 

. The methods employed are many, depending upon the nature of 
the material, its position with regard to the surface, its hardness, the 
quantity required, etc., etc. They may be roughly classified, so far as 
the present purpose is concerned, as open pits, quarries and mines. 

OPEN PIT WORKINGS. 

As a general thing, open pit workings are confined to 
soft clays, such as the glacial and alluvial types, which do not require 
blasting to loosen them, and which have not the necessary hardness 
and rocky structure to make either mining or quarrying possible. 

Open pit w^orkings take on very different proportions and charac- 
ters in different parts of the world, according to the peculiarities 
of the clay beds, the customs of the country, the kind of labor, 
the climatic conditions, etc. In rare cases thev are of enormous extent 
and great depth, but in the ordinary or typical cases they are shallow 
excavations, from two or three feet to fifteen or twentv. Soft clavs are 
seldom worked with very deep pits, because of the danger of their caving 
during rains. It is practicable in some few cases where soft clay of one 
kind occurs in a very thick bed to make a deep excavation with banks 
sloping on the angle of stability of the clay when wet. But where the 
clay sought at deep levels is desired, and a heavy stripping is to be re- 
moved, then the open pit is no longer [Hi economical method. 

An op)en pit working may, then, be understood to be any kind of a 
cut in the surface from which clays can be won, provided that it involves 
no blasting, or but very little, to make the clay workable by the ordinary 
dirt- moving tools and apparatus. It may be a straight cut through a 
plain or ridge, or a crescent-shaped side-hill cut, or a shallow superficial 
pit of great area, or a steep-sided, bowl-shaped cavity, or even a vertical- 
walled shaft of large cross-section — all are entitled to the name of open- 
pit workings. 

The open pit is the most difficult form of all clay deposits to operate, 
owing to the fact that the deposit, in the nature of the case, must be 
subjected in all stages of working to the influences of daily weather 
changes and frequent storms. Rains not only usually drive the labor- 
ers from the field, but, if of any duration, so wet the clay that it becomes 
too soft or sticky to work it when delivered to the factory. The above 
conditions are to be expected occasionally during the summer months. 



168 BULLETIN ELEVEN 

but from about November to April in states north of the fortieth 
parallel of latitude it is usually impossible to operate except at a pro- 
hibitive cost. This entails that the manufacturer shall provide storage 
sheds, which he is obliged to fill during the summer months. These 
must be of such a capacity as will tide his work through the months in 
which he is unable to gather clay from the field, or else it involves the 
stopping of the plant for from a quarter to one-half of the time. 

Winning clay from open pits may be discussed under two headings, 
viz: (1) The actual operations of the clay digging or excavation, and 
(2) the subsidiary operations of draining the works, timbering, track 
laying, protecting from weather, etc. 

The excavation is accomplished by pick and shovel work, by .plow 
and scraper work, by clay-gathering machines, and by steam shovel 
work. 

Pick and Shovel Work* — This is the most elementary method 
in use in clay works among the civilized races. It is the most expensive 
method of all in labor, and the least expensive in equipment. The 
tools are the pick and shovel. It is in use in surprisingly many clay 
works today, and it is not uncommon to see clay handled more than 
once by this method before it reaches the preparing machinery. The 
costliness of the method depends very largely on the following two 
factors: 

1. The hardness of the clay, whether requiring much picking 
or not. Some require no picking. Others must all be 
picked before any shoveling can be done. 

2. The nature of the pit-bed as a shoveling-floor, whether 
smooth or rough, and also the nature of the material to 
be shoveled, whether fine and sandy or coarse and lumpy, 
or fiat and plate-like. 

In general, the use of this method is caused by lack of capital, 
but there are cases where the clays contain impurities that can be re- 
jected by hand-digging and not by other methods, or when different 
layers of clay must be kept carefully separated, as they are reached 
successively in the pit. In such cases, pick and shovel methods cannot 
be replaced by any other. 

Spading* — A modification of ordinary pick and shovel work, known 
as spading, is used in some clays very successfully. It requires a 
clay of wet, cheese-like consistency, comparatively free from bowlders 
or foreign matter which would stop the cut of the spade. Such clays 
can often be worked with vertical walls and stand for long periods without 
caving. This method of working is not uncommon among the plastic 
clay beds of New Jersey and the Atlantic coastal plain, but among the 
older and consolidated clays of the Mississippi Valley it is not very 
commonly used. In only two instances, among the present roofing 



GEOLOGICAL SUKVEY OF OHIO. 169 

tile plants of the country, is this method used: viz., at the Detroit Roof- 
ing Tile Company, Detroit, Michigan, and the Ludowici Celadon Com- 
pany's plant at Ludowici, Georgia, The former clay bed is of glacial 
origin, and has the peculiar, tough, cheese-like nature which makes 
spading the logical mode of extraction. (See Figure 56.) One of the 
best examples seen of the spading sj'stem was at the Ludowici, Georgia, 
plant of the Ludowici-Celadon Roofing Tile Company. 



Fig. 42 — Clay Pit and Transportation System at Ludowici, Georgia. 

The clay in this pit is of a very soft, fine-grained, plastic nature, 
having a depth of about six feet, and at the bottom resting on a bed 
of fine white sand. Quoting from Veatch, "The Clay Deposits of- 
* Georgia": 

"The clay used is located near the factory on Jones Creek, a small 
tributary of the AHamaha river. The deposit is of Pleistocene age 
and is probably the equivalent of the second bottom or Columbia de- 
posits of the Chattahoochee, Ocmulgee and Savannah rivers, and was 
deposited during a high Btage of water in the Altamaha river. The 
deposit is about six miles distant from the river, but is at the present 
time occasionally flooded by back-water from the Altamaha. 

"The clay is four to seven feet in thickness, has practically no over- 
burden and is underlain by a white water-bearing sand. It is yellowish, 
red, and bluish in color; a mixture has a yellow color, is very fine-grained, 
stiff and plastic. It is free from pebbles, coarse sand or coarse rock 
fragments. The clay is noticeably bluer, stiffer and more plastic around 
the roots of old stumps, a change evidently effected by organic acids 
from the wood. The deposit is mined in small separate pits, with pick 



170 BULLETIN ELEVEN 

and shovel; water accumulates rapidly in the pits and drainage facili- 
ties are poor, and in winning the clay a clay partition is left between 
the pits, to prevent the water which accumulates in the abandoned 
pits from flowing into those which are being worked. The clay is 
hauled to the plant, which is about one-half mile distant, in cars 
pulled by mules. 

Unless the method of winning clay by shovel is properly carried 
on, very annoying results may be expected. For instance, if a pit is 
not uniform from top to bottom, i. e., there are certain layers or strata 
varying in physical properties from the bulk of the deposit, and is 
taken off layer by layer, there will be a very variable product in the 
finished ware. 

Should this same pit be w^orked in benches, loading into each car 
a certain number of spadings each time from the various benches, a 
uniform product will be the result. 

While it is possible to get a very uniform mixture of material by 
the shovel method, this point is most often neglected and little attention 
is given to the order in which the strata are loaded. 

The Plow and Scraper Method* — This simple and everywhere 
familiar mode of excavating and moving earth is available as a mode 
of winning soft clays. The limit of hardness which a clay may have 
and still be amenable to plowing and scraping is usually known as 
*'hard-pan.'' Hard-pan is commonly bowlder clay, so compact as to 
be almost impossible to plow and so full of stones as to keep a plow 
jumping out of the furrow or stalling. Shales cannot ho plowed or 
scraped, except on their weathered surface. Whien the full hardness 
of even a soft shale is reached, the method becomes an ineffective one 
and hard shales cannot be worked in this manner at all. 

The plow and scraper method is used more as a means of stripping 
earth or clays from the surface of the desired stratum than it is for the 
winning of the stratum itself. The removal of from a foot or two up 
to eight or ten feet of undesirable earth and clay from a good stratum 
is within the limits of ordinary commercial conditions, but for regular 
strippings of more than ten feet in thickness, the use of a cheaper system 
than the plow and scraper becomes necessary, and hydraulic jets to 
wash the clay away or steam shovels or mechanical excavators are used. 

It will be observed that this system is finding its chief use as an 
auxiliary to some other mode of winning. The materials stripped are 
usually spoil w^hich goes over the dump bank or is used for grading 
purposes. But, if the materials removed are in themselves fit for 
use, their winning can be accomplished at a comparatively low cost. 
In the matter of securing a homogeneous daily output from a bank 
composed of strata of different pro{X3rties, this can be accomplished, 
as in hand work, but only by the daily exercise of care and pains. In 
general, men dislike to plow up hill or down hill, and in a bank with 



GEOLOGICAL SURVEY OF OHIO. 171 

horizontal beds the strong tendency of the men would be to take it 
off layer by layer, in the very way that makes the most serious trouble 
in the factory. By w^orking the bank on an incline, so as to cut all 
strata at an oblique angle, or by taking it out in benches and mixing 
the products of the benches in the ratios of their occurrence, an output 
may be obtained of quite uniform character from a bank of variable 
composition. The extra supervision to secure this result and the little 
daily losses of time in waiting for the different loaders to deliver their 
quota in turn, will surely make the method quite a little more costly 
than that of straight stripping work. 

One of the troubles incident to this mode of working a plastic clay 
pit is in the matter of wet clay after a rain. The use of horses and 
plows, etc., makes the pit muddy at once and the clay is sure to be so 
sticky as not to be fit for immediate use or for storage. A lump of 
plastic mud will stay wet a long time if buried under a pile of similar 
material. This difficulty constitutes a very real and important restric- 
tion to the use of this plan for storing clay in sheds for winter use. 

The Clay Harvesting or Gathering; System* — This plan is devised to 
meet the objections raised against the plow and scraper system in the 
preceding paragraph and is used by those of the industry who are not 
only obliged to w'in a supply of clay for the daily consumption of the 
plant, but in the summer months must provide a supply sufficient to 
run their plants throughout the winter. This means that a large amount 
of material must be handled within a short period of time. 

Two plants, those of the Ludowici-Celadon Company at Chicago 
Heights, Illinois, and the National Roofing Tile Company, at Lima, 
Ohio, are making use of a very excellent machine for the purpose, the 
proprietary name of which is "The Quincy Clay Gatherer." It is made 
by the Central Iron Works, at Quincy, Illinois. 

« 

This machine consists principally of an open-topped drum or barrel, 
supported between two wheels, which in turn cause a set of scrapers to 
revolve around the drum. These scrajxjrs scoop up the previously 
loosened clay, and carry it on their trip around, until upon reaching 
the opening at the top of the drum the clay drops from the scrapers 
into it. 

A drive of twenty or thirty yards is sufficient to fill the drum, 
which holds approximately one cubic yard. The scrapers are then 
raised and the load is hauled off to the storage shed or grinding room, 
where the drum by means of a trip or latch is caused to revolve with 
the wheels. As soon as the drum has made about one-quarter of a 
revolution, the clay begins to empty out of the open top and by the 
time the complete revolution has been made, the entire load has been 
discharged. 



BULLETIN ELEVEN 



Fig. 43 — Quincy Clay Gatherer. 



This method of winning clays is to be commended, owing to the 
fact that the layer of clay cut off from the surface of the ground is thin, 
only an inch or two, and even if the field is wet, after rains, the use of 
a drag or harrow to cut up the surface and air it, and the removal of 
the aired clumps of clay in a series of very thin cuts, enables ciay to be 
gathered with but little interruption from summer showers, and still pro- 
cured in excellent condition for storing. The method excels that of 
the plow and scraper only int his point. 

It is an excellent mode, also, oE obtaining a uniform mixture or 
average, where the clay formation occurs in parallel strata or l>eds, 
if it is properly worked, but requires the same careful supervision before 
described to see that all levels of the pit are being worked simultaneously. 

The gathering, to be properly done, requires the proper opening 
of the field, or pit. This is done by working the field on an inchned 
plane, having a depth equal to that of clay stratum to be worked. To 
properly gather the load of clay, the scraper is started at the bottom 
of the pit, driving either straight or diagonally to the top of 
the pit, then turning round and driving down the low sloping side 
again. A load so gathered represents an accurate mixture of the de- 
posit over its entire cross section. 

The sampling does not cease with the loading of the material, but 
\s again perfected at the unloading point. As described before, the 



GEOLOGICAL SURVEY OF OHIO. 173 

load is not dumped at a single point, but is distributed over the storage 
shed floor for a distance of ten or fifteen feet. 

It will be understood, though, that the advantage of the use of this 
day gathering device is restricted. It can only produce a strict average 
of the clay, where the latter occurs in parallel strata. In a bed of 
folded, or unconformable, or irregularly mixed clays, sueli as are often 
found in the more recent clays, this system would lose much of its ef- 
ficiency as an averaging device, though it could scarcely be improved 
upon by anything else except careful hand winning. It might possibly 
be used on very soft shales, provided the bank could be opened over a 
area large enough to properly carry on the work. 

The use of the clay gatherer is much more apphcable to the glacial 
and alluvial clays, whose bedding is always horizontal. In working 
these soft clays it is necessary to precede the gatherers by about half 
a day's work with a tool known as a drag, or plow, which loosens the 
clay to a depth of about two inches. 



Fig. 44 — Quincy Clay Plow. 

This machine not only loosens the clay, but puts it into a condition 
such that it will become more or less dry by the time the scrapers 
reach it. 

It will be found next to impossible to work wet or sticky clay by 
the clay-gatherer. The clay will pack in the drum, and give much 
trouble in dumping. 

The drag, or plow, shown in Figure 44, consists of a triangular 
wooden frame about five feet on a side, supported or carried at the three 
corners by email wheels. Distributed along the sides are small plows, 
or teeth, such as are to be seen on the ordinary farm cultivators. These 
teeth extend about two inches below the bottom of the wheels that 
carry the frame. Three horses are required for the plow, which cuts 
or loosens a path of clay about five feet wide. The action of the plow 
is similar to a harrow, except that its plows have a little better cutting 
power than a harrow. 



BULLETIN ELEVEN 



Fig. 45 — Quincy Plow in Actio 



I Pit of Ludowici-Celadon Co., 



GEOLOGICAL SURVEY OP OHIO. 175 

The Steam ShoveL — Another method of winning clays very widely 
used in both soft and hard clays is the steam shovel. The general na- 
ture of this machine is so well known that it will not be necessary to 
describe it here. It is a notable fact that not in a single instance in 
1908 was the steam shovel being used to win clays for the roofing tile 
industry. 

This state of affairs can easily be explained when we consider that 
the amount of raw material consumed by a roofing tile plant is relatively 
small when compared with the brick or sewer-pipe industries. For in- 
stance, if a roofing tile plant was producing one hundred squares per 
day, this would require in the neighborhood of fifty to sixty tons of 
material. Should this same amount of material be made into building 
bricks it would produce approximately 12,000 to 15,000 of standard 
size and much fewer of paving brick. This would be considered a very 
small plant, and for the tonnage required no one w^ould think of install- 
ing a steam shovel. The investment and the expense of maintaining 
and operating the shovel would be entirely out of proportion to its 
capacity. On the other hand, a roofing tile plant of a capacity of 100 
squares a day would be considered of very fair size. It would not be 
economical to use a steam shovel equipment for a roofing tile plant 
unless the plant were a very large one. 

WINNING OF SHALES. 

As stated before, of the fourteen plants visited, ten are using 
shales, nine using open pits or quarries and one drifting or mining into 
the hillside. 

Shales differ from glacial and alluvial clays in the matter of being 
hardened to a point where they can no longer be loosened by the spade 
or shovel, and generally not by a pick with any economy. The hardened 
clays or shales almost always require blasting to break or loosen them 
from their present mass, and even when thrown in a pile of loose material 
by a blast, they generally come out in such heavy, coarse lumps that a 
further recourse to the pick, sledge and bar are required to break them 
down into sizes accepted by the crushing machinery. Often auxiliary 
shots, or ''pop shots/' are employed to break the bigger pieces after a 
big blast has thrown down the face of a shale pit. 

Before studying the methods of quarrying shale, it would seem best 
to first fix in mind what conditions are to be found at the average shale 
bank in use. 

In the majority of cases the bed of shale will be attacked at some 
point above surface grade — that is, at a higher level than the plant or 
surrounding territory. Of course, shales may occur at any level with 
regard to that of the plant, but the difficulties of operating any clay pit 
below grade are so much greater than one with free drainage that clay 



176 BULLETIN ELEVEN 

workers generally hunt for an exposure of the proper material at the 
proper elevation instead of attempting to work one at a level too low 
to permit natural drainage. Of course, in some localities, where shales 
are scarce, the deposit is worked where it can be found, and a low level 
is accepted as one of the natural obstacles to be met and ( 



Shales are usually well stratified, but in some cases, as nt the bank 
of the United States Roofin" Tile Company, at Parkersburg, \V. Va., the 
stratification of the shale is very slight or has become partially ob- 
literated. 

At the plant of the Huntington Roofing Tile t'onipany, Huntington, 
W.Va., are to be found two shale banks in use. The lower, or \o. 1 bank, 
(Figure 4S) contains an extremely fine' grained, well stratified shale, quite 



GEOLOGICAL SURVEY OF OHIO. 177 

soft and easily dislodged. Their No. 2 bank is made up of a very sandy 
shale, well stratified and very hard, breaking out or blasting in very 
large blocks, as seen in Figure No. 49. On the left hand side of the same 
figure can be seen a large pile of slaked or weathered shale. This com- 
pany was in 1908 the only roofing tile concern in the United States that 
was weathering its raw shale. 

During the summer months of each year large amounts of the shale 
are blasted loose, and then wheeled out and heaped up in a windrow 
or long pile three or four feet deep, and allowed to remain until the 
following year. This allows the natural agencies to break down the 
massive blocks of hard material, which would otherwise have to be done 
by hand or machinery. In this particular case the clay is improved 
in another way, viz., the soluble salts of lime and magnesium that are 
present in the parent ledge are leached out and carried away by the 
rains, leaving the shale much improved in quality. 

Stripping* — By observing the pictures of the various shale banks 
shown in this report, it will be noticed that the overburden ranges in 
thickness from a foot or so, up to many feet. The removal of this 
overburden, if large, becomes a serious source of expense, and a 
problem in the management of the quarry. In most cases, the strip- 
ping is done by plow and scraper. If the road to the wasting point 
is short, the small dump-scraper is used, but if the distance is over 100 
feet, the wheeled scraper is the better and more economical machine 
to use, on account of carrying much larger loads. 

At none of the roofing tile plants has the use of hydraulic jets been 
taken up, in removing the stripping or overburden. What was said 
of the use of the steam shovel as a mode of winning for roofing tile 
plants applies to the use of the hydraulic method of stripping,, in some 
degree, i. e., the amount of material to be moved will not ordinarily 
justify its use. This does not apply with equal force, however, for 
while a steam shovel of the smallest size would be much too large for 
an ordinary roofing tile plant, it is possible to make hydraulic instal- 
lations on almost any desired scale. 

The method consists in the application of streams or jets of water 
from a hose pipe, under high pressure, usually 100 pounds per square 
inch at the nozzle, against the face of the soft clay. The water will 
burrow its way into the clay, and wash it into a slime or thin fluid, 
which will flow off through runways. The labor of this system is at 
a minimum — the nozzle-man is the only one employed for hours at a 
time. But the system requires the use of great amounts of water and 
the service of an engineer to provide it, and also requires frequent 
changes in the pipe-lines, the runways, the receiving ponds or fields on 
which the slime is distributed, etc. 

12— G. B. 11. 



BULLETIN ELEVEN 



Fig. 48 — Clay Pit No. 1. Huntington Roofing Tile Co., Huntington. W, Va 



;. 40— Clay Pit No. 2. Huntington Roofing Tile Co.. Huntington, W. Va. 



GEOLOGICAL SUBVEY OF OHIO. 179 

When all such costs are included, there is no question but that this 
mode of moving sand, gravel, clay, etc., is still far below any other 
method. It requires, however, conditions that are not always found, 
viz., adequate water supply, and a place to distribute the materials used 
— the latter is often more serious than the first. The method may be 
said, therefore, not to be susceptible to general adoption, though ex- 
ceedingly cheap where the conditions favor its use. 

At the Parkersburg plant the stripping is done by pick and shovel. 
The bank is on the side of a very steep hill, so that it is only necessary 
to loosen the overburden and give it a start with a shovel and it falls 
to the bottom of the pit, where it is loaded into dump-cars and sent 
down the incline to be used as grading material in the low lands below. 

In the ordinary shale bank, the usual method of procedure is 
to first uncover or strip the surface of the shale over an area which will 
furnish a year's run. This is mostly done, as stated before, by teams 
and scrapers. In the work of developing the bank at first, this pre- 
liminary stripping is often done by pick and shovel. This is continued 
until a working-face has been exposed, that is, an exposure of the shale 
for some -distance laterally along the out-crop, and having a vertical 
section equal to the depth of the stratum, or if this be too great, so 
much of it as may be desirable to work. There is naturally a good deal 
of extra stripping to be done in opening up the ordinary shale pit, before 
the conditions of quarrying become normal. The soft or weathered edge 
of the shale is usually to be removed, and an excess of surface-clay 
or stripping has to be taken off. Gradually, as the workings progress 
back into the hill, the face of the stratum exposed becomes normal^ 
i. e., the proportion of surface-clay, weathered shale, and hard unal- 
tered shale becomes more nearly constant. 

The height of a shale stratum which can conveniently be worked 
in one bench is not over twenty or twenty-five feet. The disadvantages 
of too high a face are great — it is dangerous, when caving, and incon- 
venient to get up and down, in loosening hanging pieces, etc. A thirty- 
foot bank is generally better worked in two fifteen-foot benches, rather 
than in one of thirtv feet. 

Quarrying. — The actual operation of quarrying differs from hand- 
digging in the use of explosives. Everything else is common to the 
two modes of working. Or, rather, after a shale has been blasted, its 
loading is practically the same as hand digging, though the proportion 
of use of bar, sledge, and pick is greatly increased and the use of the 
shovel is somewhat reduced. In many cases men will lift much of the 
shale in large lumps by hand instead of by shovel. 

Blasting. — The work of disrupting rocks or earth by explosives may 
be divided into three parts, viz.: 1st, drilling or preparing the hole for 
the reception of the explosive, 2nd, the loading, or preparing the ex- 
plosive charge, and equipping' it with ignition or firing mechanism. 



180 BULLETIN ELEVEN 

and 3rd, "shooting'* or exploding the charge. For drilling, and in 
fact throughout this work, two men usually work together as a crew. 

Drilling* — Drilling holes in rocks at its best is a specialized bus- 
iness, with large mechanical equipment and room for the exercise of 
much skill. In general, however, drilling is done in four ways: 1st, 
by hand; 2nd, by augers turned by hand power, with or without a 
mechanical feeding appliance; 3rd, rotary power-drills; 4th, percus- 
sion power-drills. The choice of a method for any given case depends 
on the amount of drilling to be done, the hardness of the rocks, the 
depth and diameter of the holes, the necessity or advantage of speed in 
drilling, the wetness of the strata, etc. In general, clay and shale is 
prepared for blasting by the first two methods, especially in the roofing 
tile business, for the amount of clay needed would make the installa- 
tion of a modern drilling plant an absurd extravagance. 

Hand Drilling:. — The tools required for this work are: a five or 
six-pound sledge-hammer, usually three drills or "spuds," varying in 
length from three or four feet in the shortest, up to ten or twelve feet 
in the 'longest. It is necessary to have these various lengths to suit 
the convenience of the men as the hole deepens. The drills are of 
tool-steel, J-inch to 13^-inches in diameter, drawn out at the lower end 
into a fan-shaped bit or cutting-point. A bucket of water, a dipper, 
a brush or "swab" and a scraper for cleaning out are also needed. The 
drillers most often provide their own swab by cutting a young sapling 
(of hickory preferably) an inch or so in diameter and about ten feet long. 
Then by pounding or mashing the thick end of it with the sledge, they 
fray it out for a length of six or eight inches. 

The actual process of drilling a hole for a blast is a process similar 
in nature in all materials, but varying greatly in difficulty or the amount 
of energy required. In the softest clays which need the use of explo- 
sives, the drill can be driven into the clay by merely lifting and dropping 
it, or "churn-drilling." In fact most shale clays can be churn-drilled. 

When the shale is quite hard, the drill requires the use of more 
power. In drilling a vertical hole, one man takes the sledge, the other the 
shortest drill, which he holds plumb at the point previously selected. The 
man with the sledge, called the striker, proceeds to strike the drill with 
quick, sharp blows, while at the same time the driller between each blow 
of the sledge raises the drill a short distance and during the same inter- 
val twists the drill through an angle of from 30 to 40°. Each four or 
six blows therefore cuts the bottom of the hole over its entire area, 
creating numerous small chips of the loosened rock. 

They proceed thus until they have drilled down through from 
several inches to a foot or so of the shale. A dipper of water is now 
poured down the hole and the brush end of the swab is inserted, and 
after a short churning up and down is withdrawn laden with the newly 
made mud. On withdrawing, the swab is given a sharp blow or rap 



GEOLOGICAL SURVEY OP OHIO. 181 

over a block of wood or a stone, thus freeing it of the accumulations; 
possibly a little more water is added, and the work repeated until all 
the mud made from the drillings has been withdrawn. The drill and 
sledge are now brought into play again. Thus the work proceeds, until 
the desired depth is reached, usually not exceeding ten or twelve feet. 
The hole is now dried and cleaned out as carefully as possible, by 
pouring down a handful or so of dry clay at a time and withdrawing 
it in the spoon or scraper. In wet clays, or shales permeated with 
water-bearing seams, this drying of the hole is very difficult to do, 
and recourse is had to a cartridge of oiled or soaped paper, which will 
slip down the hole quickly and permit a shot to be gotten off before the 
water soaks through the paper. 

Auger Drilling:* — This method is applicable to clays and shales 
of all degrees of hardness. It is limited to rocks of about that grade, 
such as coal, gypsum, talc and soft limestones, and is inapplicable to 
really hard rocks like sandstones, granites, etc. 

The simplest form of this work is a double brace, or handle devised 
for twisting the auger around an imaginary center, using both arms to 
maintain the motion and the chest to supply the pressure of the drill 
against the rock. This is applicable to soft clays and only the softest 
shales. 

The common forms are frames, arranged to fasten upright or in- 
clined between the floor of the quarry or mine and some point above 
it, in the face of the rock, or the roof of the mine. This frame is braced 
in position by screws and guys. The auger is mounted on the end of a 
long screw or threaded steel bar, which is passed through a nut fastened 
in the frame described above. By turning the screw, it feeds itself 
through the nut at the rate prescribed by the pitch of its threads, usually 
one-eight of an inch per revolution. The turning is done directly by 
a crank or handle on the end of the screw, or by the intervention of 
gears, with two or three different rates of motion, if the rock to be drilled 
is fairly hard. The power is supplied by the driller himself. 

These machines are of wonderful service in mines, where the roof 
and floor offer facilities for fixing them in position readily. They will 
make holes at almost any angle, but most easily when nearly horizontal. 
They are used, but less readily, along the foot of a shale bank, in an 
inclined position, and for making horizontal holes or holes inclining 
downward. They are practically useless for making vertical holes, 
in open workings. A man will make in a six foot hole, IJi inches or 2 
inches in diameter, in ordinary shale in from twenty to thirty minutes," 
and often much quicker. 

Rotary Power Drills and Percussion Power Drills* — These may be left 
out of consideration, as they are only suited to very large quarries or 
to rocks of greater hardness than shale clays. Some few brick works 



182 BULLETIN ELEVEN 

* 

in the country are large enough to make their use economical, but 
certainly no roofing tile plant could do so. 

Spring^ing: the HoIe« — This practice is only used in rather soft rocks 
or such as are penetrated with many fissures for the escape of the ex- 
plosion gases. It is done by firing a small piece of dynamite — usually 
a section of a stick an inch long is enough — at the bottom of the hole. 
It does two things. First — it dries out the hole by the hot gases liberated 
there. Second — it makes a cavity usually pear shaped or spherical in 
shape, which acts as a receptacle for the explosive. It thus makes 
it possible to get in a much larger quantity of explosive and also to con- 
centrate it in a relatively large mass, instead of spreading it up and 
down a large vertical range. 

Choice of Explosfve* — There are two classes available — the slow 
combustion powders and the instantaneous or chemical explosives. 
The powders burn very rapidly it is true, but nevertheless they generate 
their explosion by ordinary combustion. The chemical explosives 
generate their explosion by molecular decomposition, not like combustion 
at all, though it is accompanied by heat. The difference between the 
two is very great. The powder is slow, relatively, and weak in its effects. 
The chemical explosives, represented by nitroglycerine and dynamite, 
fulminates of silver and mercury, etc., work with much greater speed 
and much sharper or concentrated effect. This difference decides the 
use of the material for its proper place. Soft, loose, uncompacted, or 
''leaky'' rocks, like shales, need powder. The effect of dynamite is 
dissipated too much. But hard, dense and "tight" rocks need dynamite. 
Either kind will of course do something in any place where used, but 
their most efficacious use is as above set forth. Many shale drillers 
use a mixed charge, partly dynamite to "start" the explosion, and the 
balance black powder to "follow it up," these terms referring to the 
difference in rate of action. The economy of thus mixing charges is open 
to question. 

• Altogether, the technique of blasting, though simple, is nevertheless 
considerable, and there is room for the acquirement of great personal 
skill in handling the explosives judiciously. A good blaster will do 
three or four times as much work with a box of explosive as an inexpert 
one. 

Loading:* — The next step is to get the charge properly into place 
in the hole. The desired quantity, usually such as will about half 
fill the hole, is dropped in, a water-proof fuse tape being first let down 
the hole until it nearly touches the bottom, then is cut off from the reel 
or main supply about a foot above the top of the hole. Then fine dry 
dirt or clay is put in on top of the explosive and b}'' means of the tamper 
or reverse end of the drill, is carefully compacted. More is added and 
tamped at short intervals, damp clay being used after the first addition. 
When the hole is entirely filled, the fuse is lighted and the men re- 



GEOLOGICAL SUKVEY OF OHIO. 183 

tiuat to a safe distance. Usually a minute or two elapses before the 
explosion. Where dynamite is used extensively, an electric sparking 
apparatus for igniting a charge is used very commonly. It has the 
advantage of not being subject to dampness, and also of making it 
possible to ignite any number of charges simultaneously. For small 
plants, it is not needed, though used by some on account of the 
somewhat less dangfer of premature or delayed blasts. In most cases 
it will be found that the bottom of the bank has been blown out, 
and the mass above has either tumbled down at the foot in a rough 
pile, or is loosely hanging, ready to fall with a little assistance from 
the bar or pick. 

In cases where the shale is hard it will be found necessary to sledge 
apart or break up the large blocks before loading into wagons or cars. 

In favorable cases it is not unusual to dislodge from fifty to several 
hundred tons at a single shot, depending on the size of the bank and 
many similar conditions. 

In Figure No. 48 can be seen the effect of a newly-made blast. All 
of the loose material behind the wagon was brought down by a single 
shot. The tamping rods, drills, and other tools for the work, can be 
seen on the bank above the fall of shale. 

It will be readily understood that the work of shooting out the shale 
for a roofing tile plant each day is only a matter of one or two well- 
placed shots. 

It is not unusual for two, three, or even five holes to be drilled 
and fired at the same time, thus providing a week's supply of material 
at a single operation. 

The Placing of Shots, — In this subject lies the most of the skill 
of the quarryman, and one mAn exceeds another in the judgment he 
displays in placing shots where they will do the most execution. The 
art cannot be learned except by practice and experience, but many 
who have practice and experience in plenty never make expert blasters. 
The quarry boss usually supervises this himself, and aims to have each 
shot so placed that, when fired, it will expose a new point of advan- 
tageous attack. The nature of the rock, its seams and openness, its 
cleavages or lines of break, its tendency to hang or merely loosen up 
without lifting out of its bed, its rate of use at the plant, the extent 
to which it hurts it to be wet or caught by rains after blasting — all 
these and many more things have to be considered in laying out the 
work of a quarry. A good quarry boss can tell what his plan of cam- 
paign is for days ahead of his work, and has provided in this plan 
for the contingencies of stormy weather, shortage of men, etc. 

Clay banks are generally worked in a long line, approximately 
straight, or on a gentle curve, or else they are worked with two faces, one 
at right angles to the other. Some, of course, are erratic in shape, on 
account of irregularities of deposit or local obstacles. 



BULLETIN ELEVEN 



MINING. 



The third method which was found in use in the winning 
ot roofing tile clays was mining. The formation mined was a shale 
of the Coal-Meaaure period, at the plant of the Murray Roofing Tile 
Company of Cloverport, Kentucky, The shale bed here is capped with 
a ledge of limestone, making a good safe roof whenever the cover was 
deep, but around the out-crop the fissures of the limestone had been 
widened by the percolation of rain water until the stratum was cut up 
into blocks. These blocks, if undermined, completely or largely, then 
became very difficult to hold up, and hence dangerous. 



Fig. 50 — Entrance to Shale Min 

The shale stratum mined was about twelve or fifteen feet in thick- 
ness. The mine was situated closely in rear of the plant, and the tram 
car haulage from the mine led directly into the stock-room of the factory. 

The mining of a stratum of moderate thickness, five to ten feet, 
is simply a modification of quarrying. The modes of blasting, loosen- 
ing the material, sorting and loading it for transportation are all the 
same, or differ only in minor details from ordinary quarrying outdoors. 
But there is introduced an entirely new set of factors, viz., the support 
of the strata overhead to prevent caving in, and the conducting of 
ventilating currents into the mine and out of it, to make the air pure 
and healthful for man and beast. The problems of haulage and drain- 
age are not much different from the same factors outside. 



GEOLOGICAL SURVEY OP OHIO. 185 

The timbering or supporting of the roof or hanging wall, is a heavy 
factor of expense in nearly all mining. This factor varies with the 
thickness of the stratum mined, for the longer the timbers must be 
to reach from floor to roof of the chamber, the heavier and more ex- 
pensive they are. 

The ventilating of a mine also calls for the use of fuel, either burned 
directly in the old-fashioned ventilating furnace, or indirectly in steam 
engines or gas engines, by which fans are driven, forcing pure air in 
or sucking vitiated air out. The ventilation also requires the driving 
of special passages, break-throughs, over-casts, and the erection of 
doors, stoppings, brattices, etc., for direction of the air currents past 
the old and abandoned workings, and into the new workings where 
they are needed. To properly ventilate a large mine is a problem 
requiring high-grade skill and experience. 

It is obvious that to work in cramped quarters, in artificial light, 
to provide an artificial air supply, to provide timbers for preventing 
the beginning of caving in, in addition to the normal expenses of quar- 
rying, draining, loading and handling, is bound to make mining an 
expensive form of winning. It cannot be otherwise. Its average 
cost per ton may be said to run from about twice to three times what 
the quarrying of the same material in the open would be. 

There are, however, some advantages to offset the extra cost. 
The ability to work the mine all the year around and deliver a constant 
supply of material in the same condition as to dryness, in all kinds of 
weather, is a matter of the highest importance to a clay plant. The 
use of the mining method of winning ordinarily does away with the 
need of a storage shed for housing a winter's supply, and for the invest- 
ment of large sums of money in clay which has to be stored months 
before it can be used. It also provides, ordinarily, a more regular 
daily operation of the plant with far less variation from day to day 
than when clay direct from an open pit is used, since it does away with 
wet and muddy material and delivers its product in the same state all 
the time. More regular operation means a larger output with the 
same force of men. So that, while mined shale is more costly than 
quarried shale, it does not necessarily follow that the output of the 
plant is costing more in the long run. 

Mining shale is more difficult in general than mining fire clay, or 
coal, or other formations, on account of the thickness of the strata and 
the extraordinary length of timbers required. For this reason, a shale 
mine is very rare, and represents conditions seldom met, while the 
mining of fire clays and kaolins is quite the usual or common method 
of working these clays. 

Draining: Clay Pits. — Clay pits, whether open or under ground, and 
in soft or hard clays, very commonly are so situated as not to be self- 
draining. On side-hill excavations, the problem of draining is usually 



186 BULLETIN ELEVEN 

merely a matter of a little ditching. But, on level grounds, where clay 
pita are really pits in the true sense of the word, or in mines where the 
formation dips away from tht: opening, the problem of keeping the 
workings dry is a factor to be seriously considered. 

There are a considerable variety of means available. The following 
were observed in actual use in clay pits of the roofing tile companies of 
this country. 

1st.. Centrifugal Pumps. — This style of pump is capable of handling 
the mud and gravel that is sucked in with the water, without the cutting 
and clogging effects that occur with a piston-actuated pump. 

The Ludowici-Celadon Company's Plant at Chicago Heights, 
III., has in use a motor-driven centrifugal pump that throws, when work- 
ing at full speed, a solid six inch stream of water. This very large and 
powerful installation is made necessary on account of the large size of 
their c!ay-pit, some six or eight acres; it clears it in a reasonably short 



time. The above company is using the same kind of pump at their 
"Dixie" plant at Ludowici, Ga. For large plants, or for large clay pits, 
or for small but very wet clay pits, the centrifugal pump is the most 



GEOLOGICAL SURVEY OF OHIO. 187 

efficient mode of draining. Its ability to handle anything that will 
flow through a pipe is a great point in its favor. It requires an ex- 
pensive installation. 

2nd, Steam Ejector. — At another plant, where the pit i very much 
smaller and the water to be moved correspondingly less, a steam ejector 
is used to drain the clay field. The ejector, while very cheap in first 
cost, is of low capacity, and at the same time is a most expensive and 
inefficient way to use steam. Supplying it with steam is usually incon- 
venient and expensive, requiring a small boiler at the pit and a man to 
tend it, or else long expensive pipe lines from the main boiler house, 
with accompanying low efficiency of the steam by cooling and conden- 
sation enroute to the pit. 

This method, however, is of great utility in many places where but 
little water is to be removed, and steam is available at no great distance. 
It is very simple in operation. 

jrd. Bucket Elevator. — Another method of doing the work is by the 
use of the ordinary bucket elevator. The elevator suited to this class 
of work would preferably be that of the link belt or chain variety. The 
ordinary rubber or canvas belt would not answer so well on account of 

the continual soaking in water, and the cutting action of the sand and 

ft 

gravel. 

By using large cups placed near together on the chain, a very large 
amount of water could be raised in a given time. The power to operate 
a rig of this type would best be supplied by a small gas or gasoline engine, 
or by a small portable steam engine as second choice. It might even 
be operated by horse power. 

4th. Farm Windmill. — The use of a common farm windmill has 
been successful in draining a small clay pit for many years at Grove port, 
Franklin County, Ohio. The pit supplies ample clay for a moderate size 
roofing tile plant, and is located on a river bottom, where water is col- 
lected freely. As stated before, draining shale banks is usually an easy 
matter as most of them are side-hill workings which can be well drained 
by simple ditches. 

^th. Suction or Piston Pump. — At one shale-pit, t)iat of the Western 
Roofing Tile Co., at Coflfeyville, Kan., the shale lies at a level below the 
general surface of the prairie, and hence artificial drainage is necessary. 
At this plant, a three horse-power gas engine is employed to operate a 
regular suction or piston pump which is placed at a sump or collection 
hole at the lowest point of the pit. The water from the rest of the pit 
is brought here by ditches, and the pump delivers it to a point outside 
of the workings. 

At the one company which was mining its shale, the Murray Roof- 
ing Tile Co., of Cloverport, Ky., the strata happen to be dipping away 
from the plant, so that the drainage of the mine tends to collect always 



188 BULLETIN ELEVEN 

at the farthest point of the workings. This is a common but unfortu- 
nate condition in mining, for it means the working face of the mine 
tends to be wet, while the old or abandoned workings are usually dry. 
The only available method to drain such workings is to put down sumps 
connected with the working faces of the rooms by shallow ditches. By 
pumping the sump dry daily or continuously if necessary, the working 
faces n>ay be kept reasonably clear of water. Sometimes in outlying 
points, it is necessary to use a water car, or water-tight box or tank, 
which is filled by pumping or bailing the water at the working face and 
emptied either outside the mine or in a sump or ditch connecting with 
the outside. This is an expensive way, but often cheaper than a pipe 
line and power pump. 

Underground workings are very apt to be much worse to drain 
than surface pits. The latter are subject to evaporation by the wind 
and sun's rays, and only fill up from rains, while mines are usually fed 
by springs or underground seepage which runs constantly. So that 
the provision of a steam pump, compressed air pump, electric motor 
driven pump or gas engine pump is apt to be a necessity. This con- 
dition exists at the Cloverport plant, which uses a steam pump for this 
purpose. 

Qay Storage. — The plant that has for its source of material an 
open shale bank is in a much better position for a continuous supply of 
clay than one depending upon an open clay-pit, owing to the fact that 
the rains do not interfere nearly so much. The shale is much harder 
and more compact, and does not soften and become difficult to shovel 
or grind as a plastic clay does. At the same time, after a long,wet 
winter, it is often found that the shale with its overburden of plastic 
stripping or of partially weathered shale has become too wet to work. 
It possibly may not be enough to prevent its being ground, but enough 
to greatly interfere with its being screened. 

There are, during the year, many days of inclement weather, in 
which men are loth to work, and even though they work their out- 
put would be far below the average. To overcome the above conditions, 
nearly every roofing tile plant using shale has made provision for the 
storage of dry shale during the summer months, in order to carry them 
over the stormy days, or to enable them to mix dry shale with the wet 
sticky shale fresh from the quarry, which is certain to be encountered 
during the spring months. 

At some of the plants, provision is only made for a supply equal 
to a few days' run, or even a few hours' run, while in others a supply 
equal to six or eight weeks run is housed, inasmuch as this matter of 
storage of clay is one intimately concerned with methods of trans- 
portation of the clay from the pit to the plant, it may properly be con- 
sidered in connection with that topic. 



GEOLOGICAL SURVEY OP OHIO. 189 

TRANSPORTATION AND STORAGE OF CLAY* 

The method of transporting tlie clays from the pits or mines 
to the point of their storage or use is a matter much influenced by local 
conditions. Without attempting to discuss all the modes by which 
such work is done, those which were actually found in use were as 
follows: (a) Wheelbarrows, (b) Common scrapers and wheeled scrapers, 
(5) Quincy clay-gatherers, (d) Horse dump-carts and dirt wagons, with 
sectional slat bottoms. 

Taking them up in turn: 

Wlieelbarfows* — The extent to which this most expensive and 
unecojiomical mode of transporting materials still prevails in clay works 
is surprising. It is a common thing, in fact the usual thing, even in 
brick plants which use from three to five times as much clay as roofing 
tile plants, to find the clay undergoing one handling by wheelbarrow. 
The expense of overhead trestles, chutes, elevator storage-bins, or other 
means of using gravity or power to avoid hand labor has seemed too 
great in hundreds of plants where the daily labor bill for doing this 
work runs into large sums. It is not uncommon to find even two and in 
some cases three separate handlings of materials before they reach the 
grinding machinery. 

It is probably allowable and proper, with only a tonnage of 50 or 
60 per day, to use wheelbarrows once^ at the clay-pit with a short haul, 
measured in a few feet or yards. But it is bad management when a 
wheelbarrow trip is extended to a distance of a hundred feet, and it 
is bad engineering when clay once lifted by man-power on a shovel 
has to be lifted by man-power again, prior to grinding. 

Scrapers, G>mmon and Wheeled* — The effective radius of action of 
a common scraper, carrying ^g' to J^ of a cubic yard when heaped, is 
not more than a hundred yards. A travel exceeding that amount 
is costing more than is economical, for the number of trips per day 
is limited and a team is slow and cumbrous in turning and maneuvering 
for a load or for the dump and not rapid when in actual transit between 
terminals. The large wheeled-scrapers, whose capacity is from % to X^i 
cubic yards, are much more effective and may properly be made to 
travel even up to 200 or 300 yards, though of course the shorter the 
travel the more economical they are. When once the clay is in a 
scraper of any type, it should never be shoveled after that time — 
gravity or power apparatus should always be provided for its reception 
and future handling. 

Quincy Qay-gatherers* — These machines, from the standpoint 
of transportation, are about like the wheeled-scrapers. Their capacity 
is no larger, and their effective radius of action is therefore small. If 
worked over large fields, their capacity per day is qaite limited. It 
is better to use the gatherers to do their specialized work of loading 



190 BULLETIN ELEVEN 

and gathering, and to provide dumping stations in thfe fields, from 
which the clay can be loaded by gravity and trasported more quickly 
and more cheaply by wagons or cars. 

Horse Dump-carts and Dirt Wagons* — A horse-drawn vehicle cap- 
able of hauling loads of considerable size, such as from* 1}4 cubic yards 
up to 3 cubic yards, can be economically used for transporting clays 
considerable distances. Instances of such transportation over moun- 
tain roads for distances of 10 or 15 miles are on record, but the cost 
of the clay of course was rendered abnormal and made a heavy tax 
on the company using it. Instances of a haul of 2}/^ to 3 miles, with 
a change of level of 300 to 400 feet, are on record for plants which have 
operated thus for 20 years, with considerable daily tonnage of brick 
and sewer pipe, but here also the cost, while not prohibitive, was high, 
and was a handicap in times of close markets. Hauling a wagon-load 
a mile is quite within reason, and permits the making of 10 or 12 loads 
per day. 

In the fourteen roofing tile plants studied, five were using wagons 
or carts for transporting their clays. Tw-o of them were located well 
within the limits of cities of a considerable size, so that other haulage, 
unless it should have been by tram-road, was out of the question. At 
the Alfred, N. Y., plant of the Ludowici-Celadon Company, the distance 
and route to be traveled would have made a tram-car system of hauling 
and maintenance very expensive, the distance being something over 
a mile, and unless a right of way could have been obtained along the 
public thoroughfare, it 'would have been necessary to have purchased a 
right of way through expensive village lots for nearly a mile and a half. 
In such a case, the wagon was probably the last resort. 

In the case of the Huntington Roofing Tile Company, Huntington, 
W. Va., it was found that they were drawing their supply of shale from 
two banks, which are in different directions, distances and elevations 
from the plant. Their No. 1 bank, which is possibly three hundred 
yards from the pan shed, could be reached easily by a tram-car line, 
but bank No. 2 would be rather difficult to reach by car. Their use 
of wagon haulage at each bank is, therefore, probably justifiable, in 
that it permits them to keep a uniform mixture of their two shales, by 
hauling the desired quantity from each. 

At the plant of the Alfred Clay Company, Alfred Station, N.Y., the 
shale was being hauled by wagon from a bank on the opposite side of a 
ravine, across from the plant. The plant being at a somewhat higher 
level than the shale-pit, it would seem that an inclined tramway could 
have been installed here very nicely and the shale handled at mate- 
rially less cost. At present the material has to be hauled up a long 
winding hill, in very laborious manner. In general, it seems, then, that 
teaming is a commercially possible method of transporting for short 
hauls of a mile or less, but that it can scarcely be considered cheap for 



GBOLOOICAL SURVEY OF OHIO. 191 

distances of over a few hundred yards. Its use in many cases, like two 
that have been cited, is due to local conditions which rule out the use 
of mechanical power. 

Tram-cats, Ptabxi by Hand or Hone. — The advantage of the use 
of cars is the great reduction in traction and the therefore greater 
speed and lower use of power, or what amounts to the same thing, 
the larger amounts which comparatively feeble power can transport. 
Also, cars permit of easy and varied modes of automatic discharge, 
adjusted in each case to the track systems or bins or chutes leading to 
the pans. The capacity of cars usually runs from one to two and one- 
half cubic yards. 

The only illustration of the use of the hand pushed cars met was 
at the Detroit Roofing Tile Co., where cars were used to bring the clay 
from the margins of the bank to a central dumping point, from which 
a conveyor took the clay into the plant. The distance to be traveled 
was small. 

Tram-caiSr Transported by Mecbanical Power. — In this group, we 
find the, largest number of installations in clay works in general, and a 
considerable proportion among the roofing tile works. The modes of 
applying mechanical power are various, such as (1) cable-roads, lower- 
ing the clay down hill, or hauling it up hill or horizontally with tail-rope 
haulage; (2) st-eam locomotives or dinkeys; (3) electric motor haulage. 

At the Western Roofing Tile Co., Coffeyville, Kan., where the 
material must be elevated from a pit below the plant level, an inclined 
track is used, with an end dump car. 



Fig. 52— Shale Bank and Car of the Western Roofing Tile Company,. 

Coffeyville, Kansas. 
The above cut shows the car, loaded, ready to be hauled up the 
incline by an ordinary winding drum with friction power and friction 
brake. 



192 



BULLETIN ELEVEN 



It wil! be noticed that this car is provided with an extra set ot 
wheels placed on the main rear axle, which was made longer to accom- 
modate them; these wheels do not run on the hauling track, but when 
the car reaches the point where it is desired to dump the load, the main 
track at this point becomes horizontal, and an extra set of rails are 
placed just outside of the regular track, where these outer rear wheels 
engage on them and come into action. These outside rails continue up 
at tho previous angle of the main track, ao as the car moves forward 
the front end moves in on a level track, while the rear end is raised higher 
and higher until the load slides out of the front end of the car by gravity. 
This style of self-dumping car costs very little extra, gives very little 
trouble by accidents or repairs, and can be ccniniended as an ingenious 
and useful toot. It should be said that this company built its own cars. 

The United States Roofing Tile Co., of Tarkersburg, W. Va., uses 
another style of car, a side dump, made by E. M. Freese & Co., of Galion, 
Ohio. The conditions at this plant are different in that the shale is 
in the neighborhood of a hundred feet above the level of the plant, so 
that Instead of using a cable and power winding drum to elevate the 
cars, a cable and friction drum without power is used to lower them 
down the incline. 

In this instance, advantage has been taken of the power developed 
by the loaded car going down the incline to haul the empty car up. 
After the first installation has been made, this system is self-supporting; 
that is, no outside power is supplied to operate it. 



m 



^ 



c 



Fig. 53— Home-made Winding Drum, in Use at United States Roofing Tile Co. 



It will be noted that this drum is a very simple affair; with the ex- 
ception of the iron work, it was built by the company's carpenter. The 
staves of the drum are of oak, about three inches by five inehfs, and 
five feet long. The brake wheel is an old band wheel, and the brake 
band itself was a piece of kiln band-iron, seven inches wide by three 
sixteenths of an inch thick. It will be noted from the illustration 
that there are only four laps of the cable about the drum. In fact, two 
would have been sufficient. 



GEOLOGICAL SURVEY OF OHIO. 193 

The object in having the drum so long is to provide travel space 
for the cable laps. When a car is to be let down the incline, the cable 
laps are either to the right or left hand flange. As the drum revolves, 
the cable travels across the face, reaching the opposite side as the car 
reaches the foot of the incline. 

Another feature of this equipment is the three rail tramway, instead 
of the usual complete double track. In order to save on the construc- 
tion, which was high on account of costly trestling, the company made 
the trestle work narrow, and a three rail track system was constructed. 
At the passing point, or half-way down the incline, it was necessary of 
course to put in a double track or switch for a distance of thirty feet 
to allow the cars to pass. At this passing point the rails are so cut and 
laid that no attention has to be given to make the cars take the proper 
route. 

The method of operation is as follows: In the beginning the first 
car up the incline had to be taken up by block and tackle; when loaded 
it was run out on the main track in front of the drum where it was hooked 
onto one end of the three-fourths inch steel cable. At the lower end of 
the incline an empty car was hooked onto the other end of the cable. 
The full car was then started over the brink and proceeded on down 
the hill, its speed being controlled by the friction band, and the up car 
passed it at the switch. As the loaded car reached the bottom, its 
impetus carried it on into the storage shed, and the empty car was 
pulled over the brink ^of the incline and out on to the level of the pit 
tioor. Both cars w^ere now uncoupled, the loaded one moved by hand 
through the shed to the desired point for dumping, a catch-pin was 
removed, and the load, which was purposely a little overbalanced on 
the dumping side, immediately caused the car to tip to an angle such 
that the charge slid out. The car was then righted and run back to the 
loose end of the cable and hooked on, ready for the up trip. At the upper 
end of the line, the second car was loaded and made ready to lower. 
This system requires two men, one at either end; besides the loaders. 

Where the elevation of the shale or clay bank is such that this 
system can be used, it is to l)e recommended on account of its simplicity 
and the low cost of operation. 

At the New Lexington plant of the Ludowici-Celadon Co., the cars 
in use were made by the Star Manufacturing Co., of New Lexington. 
The car is a heavy wooden one, strongly ironed, and for dumping is 
provided with two hinged wings which meet in the center when the car 
is closed, and which swing down vertical when the bolt is withdrawn, 
leaving the bottom of the car wide open for the full width and two-thirds 
of its length. 

At the above plant and at the Parkersburg, W. Va., plant, also, the 
shale pit is at a somewhat higher level than the factory, so that the 

13— G. B. 11. 



19i BULLETIN ELEVEN 

material must come down an incUne. The grade, though, in this case is 
rather low, so that the cars, which are provided with good brakes, are 
loaded and started down the inciine without use of any cable. A man 
rides the car down, controlling its speed by the brakes to suit himself, 
it only being necessary to apply a very little pressure to stop the car at 
any point. 

At the foot of the incline, the car enters the stock shed, and is allowed 
to run on into the shed to the desired point. Here a latch is released, 
and the two hinged wings forming the bottom of the car swing open, 
allowing the load to drop through between the track rails to the floor of 
the storage shed some twenty feet below. The bottom wings are then 
pulled back into position by a chain winding up on a shaft and locked 
by a ratchet. The car is then pushed out to. the foot of the incline, 
where it is hauled up the incline to the bank by a horse. This horse has 
been trained to follow the load down at his leisure, in time to pull up the 
empty car. 



Fig. 54 — Shale Bank of the LudoWici-Celadon Co., New Lexington. Ohio. 

At this plant the short distance of the material from the plant makes 
it possible and economical to move the shale from the bank to the 
shed in the above manner, and the low grade would make operation 
with a friction drum difficult. This plant is unquestionably handling as 
much or more raw material than any other roofing tile plant in the 
country. This plant affords one of the best examples of a proper pro- 
vision of clay under cover in storage for use in bad weather. They 



GEOLOGICAL SURVEY OF OHIO. 195 

have a shed 60 feet wide by 150 feet long, with the track supported on 
the bottom chords of the roof trusses, about 20 feet from the floor. This 
whole immense space once filled would enable them to work for weeks 
without any other supply. A conveyor is used to move the material 
from the shed to the dry pans. 

The Murray Roofing Tile Company, of Cloverport, Ky., as men- 
tioned before, works a mine to win its shale. The entrance to the mine 
is about 100 yards from the plant, and at a level a few feet higher than 
that of the plant. In order to get storage room, the track has been 
carried into the storage shed at a slightly higher level than the mine 
entrance, so that the cars run back to the mine>by gravity after dumping. 
(See Figure 50.) To bring the cars from the mine a simple winding 
drum is used. This drum is located at the inner end of the stock shed, 
and is belt-driven. 

At the Ludowici, Ga., plant of the Ludowici-Celadon Company, the 
horizontal track system a mile or more long from the clay pits to the 
works is used, and the cars are hauled over in trams by mules. The face 
of the pit is kept vertical, so that the cars can be run close up parallel 
with the working face. The workmen are stationed at various inter- 
vals and levels, the bank being worked in steps, of single spadings deep, 
one man working on each step. (See Figure 42.) 

Railroad Cars* — At two plants, where the materials and plants were 
widely separated from each other, viz., The Mound City Roofing Tile 
Company, of St. Louis, and the Cincinnati Roofing Tile and Terra Cotta 
Company, of Cincinnati, Ohio, clays are shipped in full-sized railroad 
cars. At the former plant the shale is shipped a distance of about 25 
miles, while at the latter the material is shipped about 100 miles. 

After the cars of material reach the plant they are for the greater 
part of the time unloaded by shoveling into the dry pan direct, but 
at other times the clay is carried into large storage sheds for the 
winter use. When the sheds fill up to a point where the men can no 
longer put in more material by shoveling from the car, wheelbarrows 
and runways are resorted to in order to get the clay farther back into 
the shed. 

This method of handling the raw material is quite costly, for it 
must be wheeled for a third time when needed for use. It would seem 
that a short portable conveyor reaching from the side of the car back 
into the shed as far as desired could be easily arranged. It would be 
necessary, of course, to have a countershaft extending the full length 
of the shed, with driving pulleys at regular intervals where the conveyor 
could be attached. When one part of the shed was filled it would only 
be necessary to move the conveyor on to the next section. 

When it became necessary to draw on the reserve stock of material, 
it would again seem advisable to use a conveyor extending laterally in 
the shed, so that a man stationed at any section of the storage shed 



196 BULLETIN ELEVEN 

could shovel direct onto the conveyor, which in turn would deliver the 
clay to the dry pan for grinding. Whenever the distance exceeds a 
few yards, one man could easily move as much material in a given time 
by means of a conveyor as three men could move with wheelbarrows. 

The O)nvc7or System^ — A little illustration of the use of the con- 
veyor other than the suggested case just mentioned is that of the Detroit 
Roofing Tile Co., of Detroit, Mich. Their cGnveyor reaches from the 
grinding room out into the clay pit, a matter of fifty or more yards dis- 
tance. This conveyor is merely an endless rubber or cotton belt, about 
fifteen inches wide, carried on rollers at intervals of a foot or so apart. 
The power to drive the belt is supplied at the discharge end by a geared 
friction wheel and tightener. 

At first it was possible to shovel the clay direct from the bank onto 
the belt, but as the pit enlarged it was necessary to install two hand 
push cars, shown in the illustration. By observing this figure, No. 56, 
it will be seen that the clay is dug in benches, or spadings, each car being 
loaded with a definite number of shovelfuls from each l)ench, thus 
bringing every level of the bank equally from top to bottom. When a 
car is thus loaded, it is pushed to the conveyor by hand, and there un- 
loaded by hand. There are limits in the matter of elevation to which this 
system of clay handling could be employed, but by means of cleats or 
flites fastened to the belt the material could be carried down or up a 
rather steep angle — at least 25 degrees. The development of conveyor 
systems, with enormous carrying capacity and with adjustable dumping 
points, has reached an advanced stage of development in many lines of 
industry. The limitation which prevents their wider use in roofing tile 
manufacture is the small tonnage they are called on to handle and the 
relatively great expense for installation and up-keep. However, simple, 
straightaway belts of moderate capacity are no longer costly, and they 
are very simple and efliicient in use. 

• 

THE GRINDING OF RCX)FING TILE CLAYS. 

The purposes in view in the grinding of clays preliminary to 
manufacture by the plastic, or stiff mud, process are generally twofold: 

First — To break up any impurities or obnoxious minerals which may 
happen to l^e present in coarse form, and disseminate them uniformly 
through the mass — in other words, to homogenize the clay so that any 
one cubic inch of it will have the same physical and chemical prop- 
erties as any other cubic inch. It often happens that the minerals com- 
posing a clay or shale are not obnoxious if projDerly distributed, but if 
left in coarse lumps they would be classed as impurities — quartz or 
sand-rock, for instance, which is likely to be a really desirable addition 
to the clay if it can be properly distributed. It also generally happens 
that other minerals commonly found in clays, such as limestone or 



GEOLOGICAL SURVEY OF OHIO. 



Fig, 55— Conveyor at Detroit Roofing Tile Co., 



Fig, 56— Clay Pit at Detroit Roofing Tile Company. 



198 BULLETIN ELEVEN 

iron ore, are regarded as impurities under practically all conditions, 
either before or after grinding, but by fine grinding and more even dis- 
tribution their evil influence is much reduced. 

Second — To create plasticity in clays which have been so long stored 
iu rock form in the earth's crust that they have lost this property to 
a large extent, or rather, it lies dormant and undeveloped. The grinding 
makes it possible to apply the softening power of water on an enormous 
surface area at once, and also to create a plastic paste out of the finer 
portions of almost any rock powder. There are clays so hard and stony 
that no great or sufficient plasticity can be developed, even after per- 
sistent grinding with water in powerful machinery, but these are ex- 
ceptional. 

These two purposes are most commonly both represented in the 
grinding treatment of a given clay, but in some cases only one purpose 
may be in view. In general, in soft, plastic, glacial or alluvial clays 
there is no need of grinding to develop plasticity — in fact, they more often 
need some anti-plastic body, like sand, to cut down the excess of plas- 
ticity. Grinding, in such clays, is thei^efore chiefly for the dissemination 
of the harmful impurities, and in some few machines their removal. A 
grinding treatment of such clays is often very perfunctory, and some- 
times omitted entirely. In many shale clays the homogeneity of the 
material itself is yeyy good, and no impurities of importance exist, and 
here the grinding js wholly with a view to obtain a plastic paste. 

, Grinding treatments for the plastic process of manufacture, what- 
ever object, are divisible into two groups — wet grinding and dry grind- 
ing. It will be understood that the following remarks are not intended 
to apply to the slip or washing process of preparation for pottery clays, 
or to the dry press process, which finds little if any use as yet in roof- 
ing tile manufacture. In general, wet grinding is practiced where de- 
fective plasticity is found, as it is very much more powerful in developing 
the latent plasticity of a clay than any other treatment. At the same 
time, the ability to size the grains and secure the crushing of all of the 
coarse impurities, and thus secure high homogeneity, is largely lost in 
wet grinding. Hence this threatment is usually applied to the harder 
shale clays and fire clays, and when applied to very plastic clays the 
grinding is very short-lived and imperfect. 

In general, dry grinding is practiced where the material is unho- 
mogeneous naturally, and where its lack of homogeneity would be se- 
verely felt in the product if steps were not taken to overcome it. It is 
followed ordinarily by screening, which establishes the limits of the size 
of any particles in the clay, and is therefore the guarantee of homo- 
geneity. The screened powder is then to be converted to a plastic paste 
by a subsequent. process. Thus it is seen that the dry grinding and wet 
grinding operations are really more than alternative routes to the same 



GEOLOGICAL SURVEY OF OHIO. 199 

goal. To a considerable extent they produce different results and are 
applicable to different clays. 

The determination of which treatment should be given in any indi- 
vidual case is a matter of judgment with the operator. The wet treat- 
ment is slower, more costly, and has less control of the homogeneity of 
the product, but produces by far the best plasticity, and xjan be used 
where plasticity can be gotten in no other way. In general, any clay 
can be treated by this process, but it is rather uncommon to use it 
except where necessary on account of the reasons given above. 

The dry treatment is faster, cheaper, produces a more homogeneous 
paste, but of deficient plasticity. It can be used with clays of good 
and moderate plasticity, but not very well with those of low plasticity. 
Wherever it can be used it is very. likely to be selected for the reasons 
above. 

With these preliminary statements, setting forth the theory of the 
grinding process, the different modes of doing the work will be consid- 
ered. As in the case of winning, and in short throughout this report, 
no attempt will be made to discuss all possible modes of treatment. 
Those actually found in use in roofing tile plants will form the basis, 
with such suggestions of other processes as may seem worth while. 

« • 

Grinding "With Rolls* — The roll is one of the simplest and oldeat 
forms of grinding machines. Essentially it consists of two cylinders or 
cones, whose surfaces are in close contact or held closely parallel to 
each other. Their axes must be in the same plane, and in the case of 
cylindrical rolls they are parallel, but in the conical rolls the axes are 
inclined to each other by an amount proportional to the taper of the 
cones. By revolving these rapidly toward each other, any object caught 
between them tends to be nipped and carried through. If it is not too 
large and too hard, it will be crushed in passing; if it is too large it will 
not be nipped, and will simply roll around on the surface of the rolls 
without effect. If it is small enough to be nipped, but too hard to be 
crushed, one of three things will happen — the rolls will stall and stop, 
or they will spread apart to let the hard particle through, or they will 
break. In practice, they are held to each other by heavy springs, which 
permit them to spread momentarily in passing an exceptionally hard 
piece, rather than accept the other two alternatives of stopping or 
breaking. 

Rolls are designed for two different ends: First, as a wet grinding 
machine for crushing stony, plastic clays, and for rejecting the rocks 
or hard portions which are too large to fall within the angle of nip; 
second, as a dry grinding tool for pulverizing large quantities of materials 
of nearly uniform size of grains. The commonest use of rolls in this 
way is as a tailings grinder, to finish the grinding of small particles which 
are partly reduced, but not enough so to pass the screens. 



200 BULLETIN ELEVEN 

"Wet Grinding; Rolls* — These constitute the most simple method 
found in use for crushing soft plastic clays. Two roofing tile plants were 
using this method: The Detroit Roofing Tile Co., at Detroit, Mich., and 
the Dixie plaht of the Ludowici-Celadon Co., at Ludowici, Ga. The 
clay of the former company as stated before is a fine grained blue and 
gray, alluvial clay, soft enough to be w^on by spading, and hence very 
easy to grind, and so plastic as to be very difficult to grind in a strictly 
dry grinding machine, like a dry pan. The clay coming from the pit 
by conveyor feeds directly into a pair of smooth rolls, made by the 
Horton Manufacturing Co., of Painesville, Ohio. These rolls are dif- 
ferential, one being a small roll driven at high speed, and the other a 
larger and lower speed roll. They are set up within a small fraction of 
an inch of each other. The small roll, about nine or ten inches in diame- 
ter by two feet long, runs at approximately five hundred revolutions per 
minute, while the large roll, about eighteen inches in diameter, makes 
but one hundred and fifty revolutions per minute. The peripheral 
speed of these two rolls is quite different, so that when clay is fed into 
the machine, it not only squeezes and crushes it, but also shreds and 
tears it apart as well. The lumps or pebbles are caught up and crushed 
very fine, the size depending of course on the opening between the 
rolls. This machine is able to take clay either dry or wet and carry it 
through. Ordinarily as the clay comes from the bank it is of suitable 
water content for stiff mud work, but if too dry, a little water is supplied 
immediately after passing the rolls. As the clay drops down from the 
rolls it falls directly into an open topped pug mill, eight feet long, also 
made by the Horton Manufacturing Co. The clay slowly works its way 
through the pug mill, and drops onto a platform from whence it is picked 
up by a man who tosses or slams it into storage or aging bins, being very 
careful to get the clay well packed in the bins or pits. It is here allowed 
to stand about three days, enabling the water content, if unequally 
divided, to equalize itself through the mass by diffusion. A more 
uniform product is thus obtained. 

In the Dixie plant at Ludowici, Ga., as was noted under the heading 
of winning, they are working a very fine grained plastic clay, which 
rests upon a water-bearing sand; in fact, some of the clay is at times 
dug out of water (Fig. 42). It therefore usually comes to the plant in 
a wet, semi-plastic condition. It should be mentioned here that for 
reasons discussed later, a small proportion of a very sandy shale, pre- 
viously ground and screened, is added to each car of the plastic clay as 
it comes from the field. This shale is, of course, in a dry. dusty condi- 
tion, very different from that of the clay. 

The car, wuth its double charge, proceeds up an inclined trestle to 
a hopper, where it is dumped. This hopper stands immediately over a 
pair of smooth rolls specially made for the company. These rolls are 
very large, and run at a relatively slow speed. They are two feet long 



GEOLOGICAL SURVEY OF OHIO. 201 

and thirty inches in diameter. The rolls being of the same size and 
running at the same speed, the clay in passing through them is crushed 
or squeezed, rather than shredded or torn apart. After passing through 
the rolls, the clay drops into a combined pug mill and auger machine 
made by J. D. Fate & Co., of Plymouth, Ohio. 

This machine is used as a closed top pug mill, rather than a true 
auger machine, as it does not turn out a finished product. As the clay 
issues from the end of this mill it is taken by men and slammed down 
hard into soaking or aging bins, where it remains about one week. This 
allows the excess water in the field clay to come in contact with every 
particle of the dry ground shale that has been added to it. 

In this plant is illustrated a treatment admirably suited to their 
material. The homogeneous quality of the clay is such that actual 
grinding or reduction of size of grain is not needed. What is needed is 
a thorough mixing of the plastic clay so that the la3'ers representing 
different spadings shall be wholly obliterated and a new ingredient 
entirely foreign to the clay itself shall be uniformly disposed through it. 

In their mechanical treatment, the crushing effect of the rolls is 
followed by the combined work of a double sHaft pug mill and the com- 
pressing eflfect of an auger machine, which not only thoroughly mix 
the ingredients, but compress them into a dense mass, excluding the 
bulk of the air, and bringing the particles of clay substance into close 
contact. 

Dry Grinding; and Stone Separating; Rolls* — Owing to the wide dis- 
tribution of excellent alluvial clays and shales in the United States, 
very few persons will attempt to use a glacial clay for any but the com- 
monest kinds of material. Only one plant was found using a glacial 
clay for roofing tile manufacture, viz., the Chicago Heights plant of the 
Ludowici-Celadon Company. Their clay is an average sample of the 
glacial clays which characterize the Chicago district. These clays are 
still plastic as they are taken from the pit. They are fine grained in 
the main, but very badly mixed with coarse and fine glacial pebbles of 
all sorts. Of glacial clays in general, owing to their origin in ice sheets 
moving across the earth's surface, it is to be expected that they wull be 
heterogeneous in nature, and composed of a mixture of what they have 
passed over, viz., boulders, gravel, sand, rock-dust and clay substance. 
The stones may vary in size from boulders of enormous size down to 
the point where they lose their identity, and are called gravel. The 
ingredients may not only vary widely in size, but in proportions also, 
and they may also have a wide range in composition, i. e., different 
minerals and different amounts. Thus the man who attempts to work 
a glacial till is not only confronted with the working of a very impure 
clay, but at the same time a very variable one. 

The Ludowici Company has been working a material of such charac- 
teristics since about 1893. They have not only succeeded, but have 



202 BULLETIN ELEVEN 

proved that without question good roofing tiles can be made from this 
and similar heterogeneous clays elsewhere. This company, apart from 
the original error in judgment, in establishing such a plant on such a 
clay, has faced these most trying conditions with fine determination, 
and has unquestionably brought more real engineering science into 
use in surmounting its difficulties than any other roofing tile plant in 
this country. It is not meant that other plants could not have done 
the same, but the nature of their material has mercifully not required it. 

The problem of successfully working a glacial clay begins in the 
clay-pit. B}"^ referring back to the discussion on winning, it will be 
seen that this company is using the Quincy clay-gatherer, which is 
undoubtedly the finest tool in use for the careful averaging of the clay 
as it is taken in the field. The clay is dumped by the clay-gatherers in 
a stock house or storage shed of immense proportions, holding clay 
enough for several months' operation in the winter, when the bank 
is too wet for possible winning. Through this stock-shed, a central 
conveyor-belt runs, which can be loaded by shoveling from any point in 
the shed. 

This conveyor-belt delivers at one end of the shed to the first ma- 
chine — a pair of conical, dry-crushing rolls, smooth surface, set one 
inch apart, and running at 75 revolutions per minute. These rolls 
crush the lumps of clay and smaller pebbles; any stones that are con- 
siderably larger than the opening, i. e., too big for the angle of nip, 
gradually work their way to the large end of the cones, where they 
fall out into a wheelbarrow, to be removed. The use of these rolls 
is chiefly for the sake of their qualities as stone separators, but the next 
step in the process would hardly be successful if the clay had not been 
first crushed and shredded. 

In a day's run of ten hours, nearly ninety tons of clay pass through 
this small pair of rolls. In size they are about two feet long by twelve 
inches at the large end, and seven inches at the small. 

It will be understood that the gravel stones smaller than the space 
between the rolls have passed on through untouched. In this condition 
the clay-mixture could not be used for roofing tiles or any prod- 
uct. Finer grinding must be resorted to; in fact, it must be extremely 
fine in order to prevent the lime-pebbles from pitting or ^'popping out" 
in the burned tiles. No instance was observed in the roofing tile plants 
of the country of the use of the dry-crushing rolls for very fine sizes, 
i. e., tailings crushers, but such a use is common in other branches of 
the industry. No instrument is more efficient or does more work for 
the power used, in crushing an even-sized granular material than rolls. 

Grinding; "With Dry-pans. — This machine is so well known in all 
branches of clay manufacture that no space will be used in describing 
its construction. It is in use in all countries where clay working has 
progressed beyond the rudimentary stage. No other tool wholly takes 



GEOLOGICAL SURVEY OF OHIO. 203 

its place as a rough and ready grinding machine, in which the material 
comes to it in widely varying sizes, from large lumps of several hun- 
dred-weights down toidust; in widely varying hardness, from "nigger- 
head^' boulders in glacial clays and carbonate of iron concretions in 
shales down to soft crumbly earth; in widely varying degrees of plas- 
ticity, from sticky paste after a rain up to bone-dry materials returned 
from the driers for reworking; and in rates of feeding, varying from 
overloads of 300 or 400 per cent, down to frequent periods when the 
machine is running empty. All these irregularities occur in any works, 
and on every dry-pan. No machine that cannot give a good account 
of itself under such conditions will ever displace the dry-pan as a clay- 
grinder's main reliance. 

There are a number of different designs on the market, varying 
in various more or less important details. There are over-head driven 
pans, versus under-geared pans. The latter are common in ironworks 
for wet-grinding iron ore for puddlers' "fix," but they are not common 
in clay works for either wet or dry use. The advantages claimed are 
the low frames, the accessibility of the pan itself, and the housing of 
the gears under the pan free from dust of the shop. On the first and 
second points, no argument can be raised, but the gears underneath 
are very doubtfully better placed as far as saving the gears themselves 
from wear and tear is concerned. 

There are wooden framed versus cast-iron framed, and the latter 
versus the structural-steel framed pans. The former are fast passing 
from use and the latter are coming in. The vast majority of pans now 
in use have cast-iron frames. The wear and tear on cast frames is very 
severe, and breakage is not uncommon if the bolts are allowed to work 
loose. 

There are pans with separately suspended mullers and those with 
yoked mullers, i. e., both on the same shaft. The ends of the shafts 
are held In position by side guides, but are free to move up and down 
to accommodate the various sized lumps of material passing beneath 
the mullers. 

With a continuous shaft, i. e., the yoke pattern, the lifting of one 
muller throws the opposite one into a position where it is running on the 
outer edge of its face, hence doing very little work, while in the case of the 
independent mullers each works without interference from its neighbor. 

The propelling force of the mullers is derived through their frictional 
contact with the floor of the revolving pan, one muller moving in one 
direction and the other in the opposite. 

It is claimed by the manufacturers of yoke-muller pans that they 
can get a larger tonnage per day through their pan than the other type, 
their contention being that with both mullers on the same shaft, they 
obtain more weight to crush the material in hand, and can hence grind 
more in a given time. This claim can hardly be substantiated, for it 



204 BULLETIN ELEVEN 

is the repeated blows of the mullers that break down the hardest mate- 
rial, and not their mere weight. Their combined weight can never 
be concentrated on one end in any case. It may perhaps be conceded 
that the yoked muller-pans runs smoother and with less jumping than 
the independent muUer-pan and may possibly, by reason of this, wear 
longer, but as to their giving an extra output it will not be agreed to with- 
out more figures from some uninterested source. Either style of pan, 
though, proves successful in a roofing tile plant, because here quality 
of work is considered more largely than quantity. In no case are the 
pans likely to be run to their full capacity, for the tonnage of clay 
to be ground is relatively small and the problem is quite different and 
much easier to meet than in brick manufacture, where output is much 
more important. 

Pans are also usually constructed with S3rapers underneath, which 
revolve with the pan floor, dragging the c ay ahead to one point of 
delivery on the circumference, but in some instances large concrete 
brick or stone foundations are built with sufficient depth to permit 
gravity feed of the powdered clay to the point of delivery outside of 
the base. This method reduces the friction of the pan considerably, and 
seems destined to find general acceptance wherever the local situation 
permits the necessary depth of pit. 

Pans are also arranged with direct drive, from coupled engine shafts 
(rare); direct drive with geared electric motors, a new form still rare, 
but likely to become much used; and belt driven, comprising the vast 
majority. The belts are arranged to drive pulleys placed inside the 
main bearings of the top frame, or over hanging pulleys, or pulleys 
with separate outboard bearing. The belt drive, with either self-con- 
tained or outboard bearing, makes a perfectly safe and satisfactory 
drive and is likely to persist in general use as the most generally con- 
venient. 

Besides these variations in the larger questions of design, there 
are innumerable smaller ones, such as chilled cast iron muller tires vs. 
special chrome or manganese steel tires; friction clutch vs. tooth clutch 
vs. fast and loose pulleys for starting and stopping; fixed vs. adjustable 
scrapers; and the kind of step or bottom bearing to carry the weight 
of the vertical shaft. 

The step is one of the most essential features about a dry pan. In 
the ordinary pan, the weight of the pan bed, vertical shaft and gear 
wheel, the combined weight of the two mullers and their shafts as well 
as the eight hundred (800) to sixteen hundred (1,600) pounds of clay 
in the pan is carried upon this small bearing. 

This means that a load of five or ten tons is carried upon a bearing 
not as a rule exceeding five inches in diameter. This bearing tends to 
heat very easily and unless proper oiling facilities are provided, it will 
prove very short lived. Ball-bearing steps have been brought out 



GEOLOGICAL SURVEY OF OHIO. 205 

from time to time, but they have made no impression on the market. 
The principal thing is to secure positive and copious lubrication. Nearly 
any step, if of adequate size, will stand well if it is kept thoroughly 
lubricated and clay dust and grit are kept out of it. 

In selecting a pan one should try to secure one that is strongly 
built — not only strongly built but well built. By this is meant one 
that has every joint and bearing planed and fittedy ever}' bolt hole 
drilled and machined bolts that properly fill the holes. There is not 
another machine about a clay plant that has to stand the rough usage 
that the pan is expected to endure. 

Unless the pan is built as above stated, it will only be a matter of 
a short time until it will be creaking at every joint, consuming a great 
amount of extra power, and in fact pounding itself to pieces. 

Pans of the other type, with cored bolt holes, can be seen in some of 
the roofing tile plants. In one instance a pan was found so poorly con- 
structed that there were numerous bolt holes so out of line that bolts 
could not be put in at all, or had to be driven in. There is, however, a 
marked change in the last few years toward better clay-working 
machinery, and the machine manufacturers should be given credit for 
what they have done and proper encouragement to do still better. 

As before stated the step or bottom bearing is very important. 
Select the machine having a large and easily accessible step, one that 
runs in oil and that can be opened easily for inspection. 

The two most neglected points about a clay plant are: first, the 
dry pan step, and second, the elevator boot. The location of both of 
these parts is so inaccessible and so dirty, that the tendency to neg- 
lect them is strong. Unless the pan has a step that can be easily 
reached and easily taken apart, it is certain to be neglected. The 
pan tender will ordinarily not take the trouble and undergo the discomfort 
necessary to inspect the step, until forced to do so by the evident signs 
of distress from that locality. 

It is entirely impossible for any one to say that all the virtues are 
to be found in any single design. There is no best pan in the sense of 
one filling all situations best. Of those actually found in use in the 
roofing tile plants of the country the following makes were recorded. 

American Clay Machinery Company 7 

Frost Manufacturing Company 3 

C. W. Raymond Company 2 

Bonnot Company 1 

13 

Grinding; by Disfnteg;rators« — At the plant of the National Roofing 
Tile Co., Lima, Ohio, a method of grinding is used that is not to be 
found in any other roofing tile plant in this country, though the method 
is common in other branches of the industry. 



206 BULLETIN ELEVEN 

This company is using a pulverizer manufactured by Williams 
Patent Crusher & Pulverizer Co., St. Louis, Mo. 

The machine consists of a horizontal shaft to which are keyed a 
series of discs, through the circumference of which bars are run, and 
upon the latter are hung swinging hammers, which, by centrifugal force, 
fly straight outward on a line from the center of the shaft when the 
machine is rotated at high speed. The hammers swinging outward 
strike a very powerful blow, but the hammer is not rigid or inflexible, 
being held out merely by the centrifugal force and being free to bend 
back to the center whenever it comes in contact with a body heavy enough 
to overcome the centrifugal force. This acts as an ingenious protection 
against breakage by foreign material, like picks, bolts, shovels and the 
like falling into the hopper. The machine is run at a very high rate of 
speed, so that the material to be pulverized is subjected to many thou- 
sand blows per minute. The clay, being subjected to such severe treat- 
ment as this, is completely broken up before leaving the machiue. It 
will be noted from the cut that the clay in the case of the National 
Company is elevated by the cup elevator, on the left side of the machine, 
to a point where it is fed into the hopper. Upon passing out it is again 
caught by a second elevator, shown on the right side of disintegrator. 
This elevator carries the clay to a sixteen mesh screen on the third 
floor of the building. That part of the clay which is fine enough to 
pass tlie screen falls into a storage bin while the coarse material is 
returned to the disintegrator by the chute shown in cut. 



Fig. 57 — Pulverizer or Disintegrator at Works of National Roofing Tile 
Company, Lima, Ohio. 

It is found advisable to bring the clay to the disintegrator as dry 
as possible, and even then provision is made to steam heat the jacket 
of the mill in order to prevent the clay from packing or caking on il. 

For clays of a dry, compact, fairly hard nature, this style of ma 
chine will unquestionably break up the massive lumps and reduce the 



GEOLOGICAL SUBVBY OP OHIO. 207 

whole to a moderately fine powder at a good rate, varying with the size 
of machine, horse power used, and rate of feed. If the clay be a fat, 
sticky one, as in the case of the elay at Ludowici, Ga., it would prove 
impossible to work it through a disintegrator. Even moderate damp- 
ness must be guarded against as shown by the use of the steam-heated 
jackets in this style of machine. 

The relative performance of a disintegrator versus a dry pan, which 
is the only other machine with which a comparison is at all apt, is still 
a matter requiring proof. Makers of both machines claim all the ad- 
vantages for each. It is also certain that a big disintegrator, given the 
power and speed, will grind, at a furious rate, anything in the clay line, 
excepting wet clay. But any intelligent comparison must show the rel- 
ative power consumption on the same materials, and the output per 
day per horse power used, and also the relative repair bills for a year 
or so. Such figures are not available. The use of the disintegrator has 
been known to clay workers for twenty years or more, but has made 
comparatively tittle headway in displacing the dry pan, while for harder 
and more brittle materials, less liable to pack or cake in the machine, 
the disintegrator is finding a very great market. 

Wet Gtindmg. — The pre- 
ceding types of grinding ma- 
chines are designed to operate 
on clays of various stages of 
dryness, from the cheesy con- 
sistency, as spaded out of a 
swampy pit at Ludowici, Ga., 
up to the carefully predried and 
heated clay at Chicago Heights, 
III. In all these cases grinding 
is followed by tempering, a sec- 
ond operation for the develop- 
ment of plasticity, before going 
to the ware-forming machines. 
Fig. 58— Sectional View of Disiptegrator. There are two other pro- 

cesses of grinding in use which differ from the preceding in the fact 
that grinding and tempering go on jointly in one and the same machine, 
which delivers the plastic paste direct to the forming machinery. 

The Chaser. — This machine, now rarely seen, was originated, or at 
least most largely used, in the Akron district of Ohio. It was employed 
in the sewer-pipe and stoneware plants which have been very numerous 
there for forty or fifty years — in fact, for years these industries thought 
they could use no other device. From Akron as a center, the chaser 
mills were sent all over the country in the sewer-pipe and stoneware 
trades, and they may still be found occasionally, though few if any new 
ones are being installed. The Akron Vitrified Roofing Tile Company 
used this machine exclusively for the tempering process for all the 



208 BULLETIN ELEVEN 

earlier period of their existence. They were preceded in this direction, 
however, by the Bennett Roofing Tile Company, of Baltimore, Md., now 
dismantled. 

The clay used at the Bennett Company was a soft yellow alluvial 
material. Upon being hauled to (he plant by wagon, it was stored in 
bins until needed, then being wheeled by hand to the chaser, which was 
made by Turner-Vaughn- Taylor Company, of Cuyahoga Falls, Ohio, 
The clay to the amount of 800 to 1,200 pounds was dumped into the 
pan of the mill, water added, the mill started, and the work of grinding 
earricd on for from twenty to thirty minutes per charge. The mill was 
then stopped, the clay shoveled out, and packed in bins to age a little 
before being pressed into tiles. 

The construction of the machine can be readily understood from 
the following illustration: 



I^ig- 59— Chaser Mill. 

The machine differs from other pan grinders in the fact that the 
pan floor is solid, or stationary, while the grindiny wheels run in circular 
or spiral tracks around the central vertical driving shaft; hence the name 
"chaser," for the wheels seem to be in endless pursuit of each other. 

The action of the cliawer cannot be considered efficient from the 
standpoint of power consumption, daily output of clay, labor required 
or homogeneity of product. It is stow, costly to operate, and not thor- 
ough. Nevertheless, it gives to its product, or at least it.s advocates so 
claim, a toughness and cohesion not attained by other forms of tem- 
pering appliances. Rarely will a person accustomed to the use of clay 



GEOLOGICAL SUBVEY OF OHIO. 209 

from a chaser mill willingly accept clay from any other process as a fair 
equivalent. This idea is too universal among workmen, foremen and 
owners to make it likely to be wholly a prejudice. There is a foundation 
of truth, and the cause is to be sought in the peculiar variety of sizes 
of grains in the product. The principle of a dense structure requiring 
a variety of sized grains is known and recognized in cement work and 
mortar materials, and has been broached often in connection with the 
differences in strength and toughness of clays, and it is the probable 
cause of the peculiar tenacity of chaser-tempered clays. It will be at 
once understood that there is no screening or sizing process possible 
where wet grinding and tempering processes are employed, and the 
study of the product of a chaser shows a much wider variety of shapes 
and sizes of grains than do clays which have been screened dry. No 
matter how long the grinding is continued in this machine, some coarse 
particles will always dodge the narrow tread of the tempering wheels. 

The "Wet Pan* — The wet pan, as originally used, is simply a solid 
bottomed pan, of exactly similar variety of construction to that found 
in dry pans, into which raw clay is thrown in 800 to 1,200 pound charges, 
and ground and tempered in one operation and without prescreening or 
any final sizing of grains in the plastic paste. It is still used exactly in 
this way in the fire-brick industry, where charges of hard, flinty clays 
mixed with burnt "grog" are ground until enough plasticity is developed 
to permit hand molding of simple shapes. Often thirty to forty-five 
minutes are consumed in tempering a single charge. 

This mode of operation, \yhich justly entitles the wet pan to a 
place among grinding machines, is not employed at all in the roofing 
tile industry so far as known. The latter and common use of a wet 
pan is as a tempering machine, beginning with materials previously 
groimd in a dry pan and screened to the requisite fineness for the product. 
It cannot be doubted that under these conditions the wet pan still acts 
as a grinding machine, and that tempering even for 2}/^ or 3 minutes, 
which is the usual time when screened clay is used, results in some 
increased fineness of grain. Nevertheless, the tempering or develop- 
ment of plasticity is the important feature, and the grinding is inci- 
dental (though more important than is generally conceived or admitted). 
For this reason, the further discussion of the machine will be deferred 
till the topic of tempering is reached. 

Drying and Preheating; of Clays Before Grinding* — The greatest 
obstacle in the preparation of clays by all-dry, semi-dry, or plastic 
processes, in short, by all processes except where the clay is reduced 
to a state of fluid suspension as in the "washing" process, is the constant 
tendency to clog up the machinery by reason of its strongly cohesive 
properties. These properties are essential — the foundation, in fact, 

• 

14— O. B. 11. 



210 BULLETIN ELEVEN 

of the clay's value over other minerals, but they make clay prepa- 
ration difficult and inexact. 

Rolls, of all grinding machinery, are best able to deal with a clay 
in the cheese-like plasticity found in nature. Dry pans can handle a 
limited amount of such clay if mixed with some dryer material, but 
the capacity of a pan falls off very rapidly with each increase of water, 
over five or six per cent., and at thirteen or fourteen per cent, the pans 
will not put through i or A-inch screen plates more than twenty-five 
to thirty-three per cent, of their normal output. With actual plasticity, 
the dry pan becomes impossible. Disintegrators are even more sus- 
ceptible to hindrance from moisture than dry pans. 

After a clay has been through a pan or equivalent, and is in the form 
of a coarsely granular powder, the screening still remains difficult if 
moisture exceeding five or six per cent, is present. Caking on the screen 
and covering the holes, agglomerating and rolling along on the surface 
without passing through, slicking fast in the elevator cups and refusing 
to dump, choking up spouts and runways, etc., are the troubles incident 
to dry clay screening. Water is at the bottom of all these troubles and 
thoroughly dry clay grinds and screens as easily as could be desired. 

These difficulties all increase directly in proportion to the fineness 
of the powder which is to be produced. In order to get clay fine enough 
to make a good homogeneous roofing tile body, especially if it contains 
lime or iron minerals in lumpy form originally, it is sometimes necessary 
to dry the clay in advance by some artificial treatment. Winning 
in good weather, airing before gathering, storing in dry stock sheds 
for months before use, etc., are all still insufficient to permit fine grinding. 

The best illustration of really fine grinding and of proper prepa- 
ration for it was found at the Chicago Heights, 111., plant of the 
Ludowici-Celadon Roofing Tile Company. They employ a .rotary 
dryer, consisting essentially of a boiler shell about 4 feet in diameter 
by 30 feet long, supported near its ends, in a nearly horizontal position, 
by roller bearings. 

Provision is made to rotate the dryer by a gear wheel encompass- 
ing the shell and driven by a pinion near the discharge end. The shell 
is inclosed in a brick furnace, with space left in which the heated gases 
travel around and encircle the entire mill. The heat is supplied from 
coal-fired furnaces along the sides of the discharge end. 

Formerly the gases of combustion passed directly through the 
mill, bathing the clay in their travel, with water vapor, carbonic acid, 
soot and sulphur fumes. The effect of this was believed to be respon- 
sible for a scum or efflorescence of sulphates on the burned ware, so 
the present rig was devised, whereby the gases of combustion do not 
come in contact with the clay at all, but pass along the outside of the 
shell and up the stack at the feeding end. 



GEOLOGICAL SURVEY OF OHIO. 



211 




212 BULLETIN ELEVEN 

As the clay comes from the conical stone-separating rolls, in a 
fairly well shredded or disintegrated condition, it falls upon the inclined 
chute shown in the cut, and passes directly into the dryer. The dryer 
shell is inclined about one and one-half feet in its length, so as it rotates 
about 10 or 12 revolutions per minute the clay gradually works on 
through its entire length, being continuously picked up by four fiites 
or blades, shown in the end section. These flites carry the clay nearly 
to the top of the shell before letting it fall, thus constantly stirring 
the clay up and exposing it to heat and air circulation. As the clay 
slowly reaches the hot end of the dryer, it attains a temperature of at 
least 212° F., although no attention is given to this point, except to 
Bee that the clay is perfectly dry at all times. 

As the clay leaves the dryer it is caught up by a short cup elevator 
that discharges into the nine-foot dry pan. 

A similar, but less efficient, installation has recently been put in 
by the Detroit Roofing Tile Company. In this case, they use three 
furnaces under the rotating cylinder. 



Fig. 61— Home-made Rotary Dryer installed by the Detroit Rooting Tile Co. 

Such dryers, home-made in the two instances cited, but readily 
procurable from any one of a dozen prominent engineering concerns, 
especially those that cater to the cement manufacturing industry, are 
efficient. Their first cost, if home-made or built by a local shop from 
old boiler shell as a basis, may be kept sinall— under $1,000. If bought 
from a proprietary dryer firm, with furnaces and special feed apparatus, 
it may run from $2,000 to $4,000, according to dimensions and capacity 
and guaranteed evaporation. But by their use many clay works that 
limp along on one-third or one-half output c\'Cry rainy day and close 
down all through the bad winter weather, could bo made to turn out 
a good day's work all the time. 



GEOLOGICAL SURVEY OF OHIO. 218 

The cost of the treatment is comparatively slight. The power re- 
quired to rotate the heavy cylinder is probably less than five horse power 
in some cases, and imder fifteen in any that would be needed in a roofing 
tile plant. The fuel varies according to whether it passes through the 
dryer or merely around it, from one ton to three tons per day, or its equiv- 
alent in oil or gas. The feeding and discharge can readily be made en- 
tirely mechanical. The labor of operation may be confined to firing the 
furnace and this is done by automatic stokers in the Cummer and other 
good types. On the basis of drying fifty tons per day, and using two 
tons of coal, a fireman and ten horse power, the cost would normally 
not exceed 20 cents per ton and might easily be nearer 10 cents. 

This kind of treatment is not a common thing, although its value is 
apparent and unquestionable. It happens, however, that the effect 
of this drying treatment is more complex than at first imagined, and 
that results are obtained from it which were not in the least anticipated 
by those who first installed it. This subject has come to light through 
the researches of Prof. A. V. Bleininger,* of the University of Illinois 
and the United States Geological Survey,' advance sheets of whose bul- 
letin, in collaboration with Layman, have very kindly been furnishecl 
for notice in this report. 

In the above article it has been shown that by taking a clay of high 
shrinkage, one which cracked so badly in drying that it was commer- 
cially impossible to work it, and preheating it at a temperature varying 
from 100 to 200 degrees above boiling point of water, it was possible to 
so reduce the shrinkage that the clay could be safely worked. 

The test was applied to a clay found near Urbana, 111., which is 
extremely fine grained, very sticky and plastic, but of low bonding power. 
Small samples of the clay were heated at 100, 200 and 300 degrees cen- 
tigrade; after pulverizing and screening, the clay was tempered and 
wedged, then made into bars 10 inches by one-half inch by one-half 
inch. At the same time bars of the unheated clay were also made. 

It was found that the bar made from the unheated clay warped 
very badly, and the bar made from the clay heated at 100 degrees centi- 
grade did likewise. The bars made from the samples heated at 200 
and 300 degrees centigrade showed very little warping. 

The linear shrinkages were as follows: 

Unheated clay 10.3 per cent. 

Clay heated at 100** C 9.7 per cent. 

Clay h^ted at 200° C 7.3 per cent. 

Clay heated at 300° C 7.1 per cent. 

Thus it is plain that a marked improvement was made in the 
shrinkage by preheating. It was noted that the clay heated at 100 de*- 

^Publications of the Univ. of 111. A method of making possible the usfe 
of the Illinois Joint Clay. A. V. Bleinineer and F. E. Layman. 1910. 

^Owing to transfer of work, this bulletin was finally brought out by the 
Bureau of Standards. 



214 



BULLETIN ELEVEN 



grees was still sticky, while those at 200 degrees and 300 degrees had 
lost that characteristic property. 

It will also be noted that very little decrease was made in the shrink- 
age between the 200 degree and 300 degree samples, hence it would be 
probably useless to carry the heating up to the latter figure. 

They also went further with the work, making up samples in 
which varying per cents of the heated and raw clay were used, giving 
the following results: 

TABLE No. 34. 
Results of Preheating Treatment of Illinois Joint Clay. 



Kind of Material. 


Amount 

TemperinB 

W ater in 

Per cent. 

Dry 
Weight. 


Drying 

Shrinkage 

in Per 

cent. 

Volume. 


Burning 

Shrinkage 

in Per 

cent, by 

Volume. 


Drying 

Loss in 

Per cent. 


Burning 

Loss in 

Per cent. 


Total Loss 

in 
Per cent. 


Raw clay 

25% heated, 75% raw . . 
50% heated, 50% raw .. 
75% heated, 25% raw .. 
Heated at 200® C 


33.5 
32.0 
31.9 
31.0 
29.9 


41.2 
39.1 
35.8 
34.1 
29.3 


21.1 

21. 

21. 

20.9 

20.6 


32. 

26. 

15.3 
9.7 
0.5 


15. 

9.1 
11.0 
12.9 

4.0 


47. 
35.1 
26.3 
22.6 
4.5 



From the above results it is apparent that the preheating of the 
clay has greatly decreased the drying shrinkage, the difference being 
11.9 per cent, in volume, or nearly 4 per cent, linear shrinkage. 

It will also be noted that a decrease in the burning shrinkage has 
also resulted from the preheating. The total volume shrinkage is de- 
creased from 62.3 per cent, to 49.9 per cent, a difference of 12.4 per cent. 
The linear shrinkage has been reduced from 20.7 per cent, to 16.6 per 
cent. It will be noted that the shrinkage and losses decrease roughly 
with the increase of preheated clay. The writers also say that the sticky 
nature of the clay has been destroyed. 

As to the cost, preheating can be carried on economically in prop- 
erly constructed rotary dryers, either fired directly or making use of the 
waste heat from kilns. Quotations of two firms on the cost of dryers for 
such work were obtained. One firm recommended a rotary dryer, heated 
by direct firing, sixty inches in diameter and forty feet long, incased in 
brick. The cost of the dryer complete was $3,000, less freight. 

The machine would dry fifteen tons of clay pex hour, requiring 
eight to twelve horse power to operate, and for a material containing 
fifteen per cent, moisture the fuel consumption would be about 500 pounds 
of coal per hour. It was estimated that the cost per ton for preheating 
would be ten cents, including labor and depreciation. 

A second firm gave the following figures: The cost of the dryer, 
$3,500; erection, $600.00; power required, 20 horse; fuel consumption. 



GEOLOGICAL SURVEY OF OHIO. 



215 



60 pounds of good coal per ton of clay. The cost of drying was estimated 
at twelve cents per ton. 

As many of the standard roofing tile clays discussed in Chapter III 
have rather high shrinkages, and would be improved if the same could 
be reduced, it was thought well, in view of the facts set forth in the above 
paper, to take a number of roofing tile clays of the highest drying shrink- 
age, and put them through the same tests used by Bleininger and Layman. 

The tests, as carried out for this report, were conducted on five 
clays, numbers A, E, F, H and L, respectively, which were first ground 
to pass a 20-mesh screen. Several pounds of each were put in shallow 
pans and placed in the muffle of a Caulkins kiln, and the gas lit. By 
means of a pyrometer, the temperature was maintained for several hours 
at 200 degrees centigrade or above. At the end of this time the clays 
were taken out and cooled. It was found that they had materially 
changed in color, nearly all of them, regardless of the original color, as- 
suming a light brick-red color. The clays were then tempered, and al- 
lowed to stand for forty-eight hours before wedging carefully and making 
into trial pieces two inches by two inches by three-fourths of an inch 
thick. The designation of the sample and marks 50 mm. apart were 
carefully stamped upon each test piece. They were weighed, and then 
placed in oil, and after soaking for twenty-four hours, were carefully 
measured for their volume in the Seger volumeter. They were then 
dried, reweighed, and new measurements of the shrinkage taken after 
complete saturation in oil. The following results were obtained: 

TABLE No. 35. 

Showing Differences in Linear and Volume Drying Shrinkage of Clays in Their 
Natural Condition, and the Same Clays Heated at 200** C. 



Designation 
of Clay. 


Volume 
Shrinkage of 
Natural Clay. 


Volunr:e 

Shrinkage of 

Dried Clay. 


DifTerence in 

Favor of 
Dried Clay. 


Linear 

Shrinkage of 

Wet Clay. 


Linear 

Shrinkage of 

DriedClay. 


Difference. 


A 


13.47 


11.63 


1.84 


3.94 


3.70 


0.24 


E 


12.43 


11.10 


1.33 


3.94 


4.03 


0.09 


F 


12.96 


7.55 


5.41 


4.03 


2.44 


1.59 


H 


19.36 


12.52 


6.84 


6.00 


3.98 


2.02 


L 


16.96 


13.61 


3.34 


4.88 


4.52 


0.36 



Designation 
of Clay. 

■ 


Calculated 

Linear 

Shrinkage of 

Natural Clay. 


Calculated 

Linear 

Shrinkage of 

Dried Clay. 


Difference. 

• 


Plasticity Water 

in 

Natural Clay. 


Plasticity Water 

in 

Dried Clay. 


A 
E 
F 
H 
L 


4.71 
4.33 
4.52 
6.92 
6.01 


4.04 
3.85 
2.58 
4.36 
4.76 


0.67 
0.48 
1.94 
1.56 
1.25 


16.01 
16.80 
19.08 
19.83 
16.67 


18.19 
19.73 
17.18 
20.00 
17.26 



216 BULLETIN ELEVEN 

From the foregoing table, it will be observed that the volume 
shrinkage has been reduced in every instance by the heating of the 
clay, clay H being reduced by a total of 6.84 per cent., while clay 
E was affected the least, having been reduced only 1.33 per cent. The 
linear shrinkages, with one exception (clay E), check the volume shrink- 
ages in so far as they show a general decrease of shrinkage by the heat- 
ing. The exceptional case of clay E is no doubt due to error in making 
the small linear measurements, because the volume shrinkage shows 
a small loss for this clay. It will furthermore be noted that the cal- 
culated linear shrinkages check the measured shrinkages in a general 
way. 

The table on page 217 gives the further data obtained on the 
fire shrinkage of the same five clays. 

It is difficult to interpret the fire shrinkages,as they fluctuate widely 
between clays and in the same clay itself at different temperatures 
with no clearly prevailing tendency. But the fire shrinkages of any 
clay are the least worthy of credence of any measurements obtained 
from the test, as they are the point where all irregularities of measure- 
ment, treatment or inherent peculiarity are sure to be lodged. The total 
volume shrinkages show in general what the drying shrinkages do — 
viz., a clear tendency to reduction by the preheating treatment and 
a variable degree of sensitiveness to its influence in different clays. 

It was observed during the tempering of the predried clays that 
they had a tendency to work *'short," or, in other words, after the manner 
of meal. Therefore, a comparison of water required to develop plas- 
ticity was made. It will be noted that the samples that were preheated 
have with one exception, clay F, taken more water to develop their 
plasticity than the clay in its raw or natural condition, which is very 
surprising in view of the reduction in shrinkage. 

While no actual data were obtained on the rate of drying of these 
trials, it is firmly believed that, owing to their granular condition, they 
dried very easily and at a much more rapid rate than in the case of 
the same clays in their raw condition. 

The fact that a clay like H had its volume shrinkage on heating 
reduced 35.33 per cent, and its linear shrinkage 33.51 per cent., or in 
other words over one-third of the total amount, should convince the 
most skeptical that there are great possibilities in this preheating treat- 
ment for some clays. The findings obtained in this work throw no 
new light on the work of Bleininger and Layman, except to show that 
their process applies to other clays than those studied by them and that 
it does not by any means apply to all with equal force. Some clays 
are evidently but little affected. Much fuller and more careful inves- 
tigations on this subject are in progress in the U. S. Geological Survey 
laboratories at Pittsburgh, under direction of Professor Bleininger, 
where the cause is being earnestly sought for and the behavior of 
different clays at different temperatures is being studied. 



GEOLOGICAL SURVEY OF OHIO. 



217 









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II 



218 BULLETIN ELEVEN 

With the above figures at hand it would seem certain that it is 
within the reach of the roofing tile manufacturers of the country to 
install and operate such preheating equipments. The results shown 
in the original article and those obtained from the, study of actual 
roofing tile clays show highly desirable results in most of the clays tried. 

The relatively small tonnage of material used per day by the roofing 
tile manufacturers, and the price obtained per ton for the finished 
ware, make it entirely within the scope of possibility for them to pre- 
heat their clays. It certainly would be of great advantage to those 
working highly shrinking clays to preheat all or part of their clay at 
least. By the utilization of waste heat from the cooling kilns the cost 
of the treatment could be reduced to a few cents per ton, even putting 
it within the reach of the brick manufacturer. It is beyond doubt 
that those who have been using rotary dryers for purely drying pur- 
poses, have often obtained something of the value of this preheating 
treatment without definitely recognizing it, at least for a part of the 
time, if not constantly. One such instance is on record, where a brick 
manufacturer had almost no trouble fl*om cracking in winter when 
his dryer was necessary to grind the clay, but had constant trouble 
in summer, when the clay was dry enough to grind without the dryer 
being used. 

Screening;* — The purpose of screening is to set a limit to the max- 
imum size of mineral particles which will be allowed to enter a piece 
of clay ware. As the coarsest particles in a ground mixture are also 
apt to be the hardest and also of different chemical composition from 
the general matrix of fine material which contains the plastic aluminous 
matter we think of as clay substance, it follows that these coarse par- 
ticles are both difficult to grind finer and are the most injurious to the 
homogeneous character of the clay if they are not ground and made 
to blend well into the matrix. Particles of limestone, carbonate of 
iron, gypsum, pyrites, coal, etc., are all able to ruin the appearance 
of the product unless thoroughly disseminated by fine grinding. 

Screening is therefore necessary to establish a limit beyond which 
particles cannot enter the clay body, except by accident. It is a very 
necessary part of the process of homogenization, of which grinding 
and tempering are the two principal steps. 

The operation of screening clays is more troublesome than that 
of screening other dry powders, because of the sticky nature of clay 
grains when damp, as explained under predrying. For this reason, 
the actual size limit used in clay plants is often much greater than 
is desired by the manufacturer, because without predrying he cannot 
either grind or screen effectively. By thoroughly drying a clay in 
advance, fine grinding in the dry way becomes possible to any limit 
.needed for the most exact homogeneity of product required for any 
commercial uses. 



GEOLOGICAL SURVEY OF OHIO. 219 

The maximum size of particles permissible in roofing tiles is prob- 
ably somewhat less th&n for other parallel industries like paving brick, 
face brick, sewer pipe, etc. In general, a screen of 8 meshes per lineal 
inch, or 64 holes per square inch, with the wires which make these meshes 
occupying about one-third of the space, represents commercial fine- 
ness for brick and pipe. That makes the diameter of a particle to pass 
these holes not to exceed about 0.08 inch, though 0.10 would be likely 
to be found due to irregularities of weaving of the wire cloth. But 
besides wire cloth, screening is donie by perforated metal plates, with 
round holes or slotted holes, and latterly by piano wire screens with 
long slots, practically free from cross wires, so that the particles of 
flaky shape may, theoretically at least, pass the screen with far larger 
dimensions than 0.10 on one or more of their axes. 

The expression "ten mesh" or "eight mesh'' does not, therefore, 
carry a clear and unambiguous meaning of size, for the size of the wire 
must also be stated. Perforated metal with round holes makes a screen 
much slower to operate, but a much more exact standard of size. 

Roofing tile clays in general are passed through from twelve to 
twenty mesh screens or equivalent. In one instance eighty mesh was 
used for a long time, but this is altogether unusual, and was also un- 
necessary for a product of the required grade. 

Qassffication of Screens in Use* — In going over all the styles of 
screens in use, it is found that with two exceptions manufacturers 
are all using some form of the inclined screen, either stationary or mov- 
able. 

Stationary Inclined Screens. — These consist of an inclined chute, the 
bottom of which is made of perforated metal or woven wire cloth, 
over which the pulverized clay passes by gravity. The size of the per- 
forations and the angle at which the screen is hung governs the size of 
grain that will pass through it. 

Should the screen be horizontal, particles the same size as the open- 
ings will pass through, but upon elevating one end of the screen so that 
the material attains a momentum, the particles passing through will 
become smaller and smaller as the angle of elevation increases. 

Advantage is usually taken of this fact in constructing inclined 
screens, so that variations in their angle can be easily made. During 
the seasons of the year when the. clay is damp and screening difficult 
the angle can be flattened to enable the material to more readily pass 
through. As the material becomes more dry later in the season, the 
screen can again be raised to its former angle. The manufacturer can 
thus keep up nearly his proper daily output, although this means, of 
course, a lowering of the standard of his wares as to homogeneity in 
bad weather, which is a practice full of danger to the reputation of the 
product. The stationary inclined screen gives much trouble through its 
tendency to become caked over with clay, especially when the clay is 



220 BULLETIN ELEVEN 

damp. This means that the attention of some one must be given to 
the screen to keep it effective. Ordinarily a hoe or shovel worked back- 
ward and forward over the surface of the screen will partly keep it 
cleared of caked obstructions. Very often the work of keeping a screen 
clean is left to the dry pan feeder or some one else whose main duties 
are elsewhere. Visits to screens, up dusty stairs or dark ladders, are 
always likely to be at long intervals, for everyone is likely to dodge a 
disagreeable task if he can. It very often happens that one-third or 
one-half of the clay delivered to the screen from the grinder is being 
returned to the grinder as tailings because it cannot pass through the 
coated or clogged screen. The attendant will then make his way to the 
screen loft, and in desperation will attack the accumulation too vigor- 
ously, loosening large chunks of the caked dust, which slide down the 
screen and are likely to choke the tailings spout. This necessitates a 
shut-down of the pan while the obstruction is being removed. 

The fixed incline screen was found in use in only one roofing title 
plant, the Huntington Roofing Tile Company, Huntington, W. Va. 
Their material, as mentioned before, is composed of two shales, one 
very plastic and the other very sandy. The proportion of the mixture 
was not obtained, but the screened clay appears to be quite high in 
free silica. A sandy clay is not nearly so likely to cake on a screen as a 
more fat, plastic one. It was also found that the mesh of the screen 
used here was sixteen, which is a little coarser than the average mesh 
used by roofing tile manufacturers. These two facts probably explain 
why it is possible for this firm to use this simple type of screen without 
prohibitive trouble. 

Piano Wire Screen* — A rather recent form of inclined screen is 
called the ''piano wire type," which has been in use for only a few 
years. As the name implies, the screen is made of heavy steel piano 
wires. These are strung parallel on a strong, substantial cast or 
wrought iron frame about two and one-half feet wide by six feet long. 
The wires are drawn to a high tension by screw tightening pins, and 
should be so firmly secured that they cannot slip. If this is not guarded, 
the screen becomes very inefficient indeed. At each end of the frame 
the wires are drawn over a heavy rod, which is threaded to suit the 
space required between the wires. By varying the pitch of these 
threads the mesh can be easily changed to suit the conditions under 
which the screen is to be used. 

A threaded rod is also placed in the middle of the screen, and some- 
times two are used to steady the wires and prevent them from spreading 
apart when pieces wedge between them. The screen is usually set or 
hung so that the angle can easily be changed to meet changes in the con- 
dition of the clay. A very satisfactory expedient for preserving the dis- 
tance between the wires without making any superficial obstacle for the 
clay to lodge against or start to cake upon, is to solder strips of tin on 



GEOLOGICAL SUBVBY OF OHIO. 221 

the lower side of the wires at iotervals of a foot or so apart. The solder 
can be scrapsd smooth with the top surface of the wire very easily; it 
takes up but little room, and is easily repaired at any time. 

The increased rigidity of the wires is very important, indeed, in 
preventing wedging apart and consequent irregularity of output. The 
claims for this style of screen are: First, it has a large screening capacity, 
while giving very little trouble from clogging or packing of the clays; 
second, it does not cost anything for power to operate it; third, it re- 
quires but very little head room to house it. 

The above claims are all well founded, and without question for 
some classes of clay product this machine is a very valuable invention 
for the trade. 
. As applied to the roofing tile indus- 

try, a strong objection has been raised 
against it. This objection is that it is 
impossible to secure a close enough ac- 
curacy of sizing for roofing tiles, owing 
to the wires stretching and becoming 
loose, sagging down and allowing large 
grains of hard material to pass through. 
Three plants were found to be us- 
ing the piano wire screen with more 
or less success, depending on the nature 
of their raw material. 

One plant, using a very soft, easily 
slaking shale, was getting very good 
results. The very next plant visited, 
which was working a very hard, sandy 
Fig. 62 — Piano Wire Screen. shale, was getting anything but good 
results, the surface of the tiles being 
rough and unsightly at close range. One of the largest plants had at 
One time installed two piano wire screens, and after giving them a thor- 
ough test taken them out on account of their requiring too much 
attention to keep the product as uniform as is desired. 

The "Perfect" Screen.— This screen seems to be in most favor 
with the roofing tile manufacturers. It is made by the Dunlap Man- 
ufacturing Company, of Bloomington, 111. It is a modified form of 
the inclined screen. The main difference is that the screening surface, 
composed of plates of perforated metal, is continually in motion on an 
endless chain. 

The object of this device is to bring automatically every part of 
the screen surface over a rotary cleaning brush instead of depending 
on its being done by hand, as is the case with all stationary inclined 
screens. The perfect screen is made up of sectional screen plates, 
attached to sprocket chains on each side. These chains travel upward 



222 BULLETIN ELEVEN 

on an inclined frame-work around sprocket wheels at the top, back 
on the lower side, etc. There are four points of attachment to each 
plate, two on each side. One attachment is at the forward edge 
of the plate and the other is at the center, permitting the plates to travel 
around the sprocket wheels without binding. The clay from the grind- 
ing machine is thrown onto a spreading board at the upper end of the 
screen. After leaving the spreading board, the clay slides down over 
the surface of the screen plates which are travelling in the opposite 
direction, or against the down-coming stream of clay. The clay, pass- 
ing through the perforated plates, drops onto a floor which is between 
the two lines of travelling plates. The floor is more highly inclined 
than the screen proper, thus facilitating the delivery of the fine clay 
at the lower end where it falls upon the reverse side of the perforated 
plate. As the plate revolves around the sprocket wheel, the clay is 
dumped off into a bin below. The tailings flow over the lower end of 
the screen into a spout which returns them to the grinding machine. 
Curtains of loose aprons of canvas are hung down, touching the surface 
of the up-travelling screen plates. These retard the down flow of the 
clay, and have an effect similar to that of rubbing material through 
a screen by hand. 

On the other side of the frame work is a rotating brush, held in 
contact by weights with the face side of the screen plates as they pass 
downward on their return trip. By adding more or less weight to this 
brush, it can be made to brush harder or easier, as the condition of 
the clay requires. 

The screen plates in this machine are most usually of perforated 
metal, although piano wire plates can be furnished. In the metal 
plates, the perforations are usually slotted and are placed in rows her- 
ring-bone fashion, thus causing a greater resistance to the clay passing 
over it. 

The entire screen is so hung that its angle can be changed in a very 
few minutes. 

The rate of travel of the screen plates is quite slow, not over three 
or four feet per minute, so that the wear on the machine is very slight 
and the power used is insignificant. The screens are made in three 
sizes, the medium size is the one most used by the roofing tile manufac- 
turers. This size will easily care for the clay from a single nine-foot 
dry pan, and screen it to the fine mesh desired for roofing tile. 

In five plants, six of the above screens were found in use, the 
range of the meshes being eighteen at. three plants and twenty at the 
two others. No trouble was found in obtaining a sufficient amount 
of screened clay of this fineness. Owing to the constantly revolving 
brush, the room where this screen is used is for the most part rather 
dusty. The sweepings are generally allowed to fall to the floor instead 
pf being caught in a chute and returned to the pan. This latter point 



GEOLOGICAL SURVEY OF OHIO. 223 

ia not a fault of the screen in question, but toerely represents poor con- 
struction on the part of the builder. There are a number of distinct 
advantages in this type of screen over others. 



Fig. 63 — The "Perfect" Clay Screen, 

Its automatic cleaning is simple, effective and cheap. It requires 
almost no attention, and it has a large capacity, and will screen finer 
clay than other inclined screens because it is always clean. 

On the other hand it requires some power to operate it, though 
not very much. It makes a good deal of dust, and is large, and requires 
considerable head room. None of these objections are serious. 

Centrifugal Screen. — There j'et remains to describe a screen found 
in the plant of the Ludowici-Celadon Company, at Alfred, N. Y., which 
is out of the ordinary in the clay industry. 

It consists of a large funnel-shaped cage or receptacle, about four 
feet high with a diameter of nine feet at 'its upper or large end. The 
shell of this funnel is made of perforated metal. Vertically through 
the center oC this cone passes a shaft. At the lower end it extends 
through and rests in a step below the funnel. The upper end passes 
through ■& bearing and is equipped with bevel gears, to be driven 
by power. The conical shell is fastened to the main upright shaft 
by means of spiders, and hence revolves with it. The clay to be screened 
is fed into the cehter of the rapidly revolving cage. Upon striking 
the floor it at once begins to move up the sloping sides of the screen 
by centrifugal force, the fine clay being carried through the perforations 
while the coarser material travels on up the sides until it passes out 
over the top where it is caught in a trough and returned to the dry 
pan. The screened clay is intercepted by an exterior conical shell 
or casing that encircles the screen. Sliding down this floor, it enters 
an elevator boot where it is elevated to the storage bins. 

It is claimed by the owners that this screen has for a number 



224 BULLETIN ELEVEN 

of years given excellent satisfaction. In fact, the first one proved so 
satisfactory that the company later added a second one, though of 
smaller size, the latter one being only six feet in diameter at its large 
end. 

This type of screen, possibly differing in some details, has since 
been taken up by the manufacturers of clay machinery and applied 
to ether plants. 

In the Alfred plant, it is somewhat unfavorably situated, being 
set on the second floor on a level with the clay bin, and thus requiring 
two elevators to serve it, one to bring clay to it and the other to carry the 
fine screened product up to the top of the bin near by. This is a local 
fault and in no wise diminishes the effectiveness of the machine itself. 

Other Types of Screens. — There are many other screens in use 
in other clay industries, which might have been applied equally well 
to roofing tile manufacture. Shaking or vibrating screens, rotary 
or cylindrical or conical screens on a nearly horizontal axis, gyratory 
screens, pneumatic sizing by means of air blasts, are some of the more 
important. None are especially more effective than those discussed. 

The screening done by the Ludowici-Celadon Company at their 
Chicago Heights plant is unusual, both as to method and fineness. After 
passing the pan, the clay is caught up by a cup elevator and carried 
to the third story of the building, where it is thrown onto a pair of 
inclined gravity screens, constructed like a letter A, having an angle 
or opening of about 90°. These screens are joined at the top, or apex, 
and are about thirty-six inches wide by eighteen feet long per side, 
thus giving a screening area equal to a single screen thirty-six inches 
by thirty-six feet. 

The advantage claimed for this arrangement is that a lower build- 
ing is required than if built in one single screen. There is one disadvan- 
tage however. The screened clay that falls through one end of the screen 
must be conveyed over to the other side in order to have it dumped in 
the same bin. This conveying is done by means of a belt conveyor. 

The mesh of the screen was found to be one twenty-eighth of an 
inch, but with this extremely fine mesh set at an angle of forty-five 
degrees, the actual degree of fineness of the clay screened is nearer to 
forty or sixty mesh than twenty-^ight. 

It would seem next to impossible to screen the large tonnage used 
by this company through a screen of the above type and size and to 
such an extremely fine mesh, and under ordinary conditions it would 
be wholly so, but when the condition of the clay that goes to the screen 
is considered, it is not so hard to understand. The clay comes from 
the rotary dryer perfectly dry and so hot that after it passes the dry 
pan, and has been elevated and screened, it still contains so much heat 
that one can scarcely hold it in the open hand. 



GEOLOGICAL SURVEY OF OHIO. 225 

Under no other conditions would it be possible to screen so large a 
quantity of dry clay to so fine a mesh, which is much the finest used by 
any roofing tile plant in the United States. 

Studying briefly the results accomplished by this fine grinding, the 
heretofore mixture of rocky gravel, clay and sand has been made so 
fine and intimately mixed that it is, roughly speaking, a definite com- 
pound. That is, it will act more nearly like a single substance than as 
a mixture of several independent ingredients. The most troublesome 
material, limestone, has been reduced to such fine grains that it has 
lost its power to cause popping. It still makes the body a little lighter 
in color, and possibly helps to form sulphate scum on the surface of the 
tiles if brought in contact with sulphur gases in the kiln or dryer. 

While the use of glacial clay like this for roofing tile manufacture 
has been proved possible by this company, still it is not to be recom- 
mended, unless it be in very rare cases, in a territory where all other 
clays are lacking. Owing to their variable composition and the great 
care and expense necessary to prepare them properly, their use from 
an economical standpoint is to be condemned. 

As a rule glacial till runs so high in lime content that it is impossible 
to vitrify it safely. High lime content in a clay has that peculiar and 
treacherous feature of causing a very short vitrification range. 

So narrow is the limit between a good hard body and a vitrified one, 
speaking, of course, of limy clays, that the trade has not at its command 
a kiln permitting of regulation close enough to burn such clays to vitrifi- 
cation with safety. 

This means that the burning of glacial clays must stop at a point 
well below the complete vitrification point. In other words, the body 
must be left porous. 

Again, it is not likely that a clay of glacial origin will, with its various 
ingredients, burn to the good clean red so much desired for roofing tiles. 
This means that to obtain a good color the manufacturer must go to 
the expense of buying a good red burning clay elsewhere, and using it 
as a slip coating over the face of the glacial clay tile. 

This false covering is only a makeshift, adding greatly to the cost 
of production, and unless the body and slip fit well, they are likely to 
separate and peel. Also accidental chipping of the tile discloses its 
light colored body beneath the slip and keeps customers irritated over 
trifling defects not at all visible after the tile is in position. 

So, though this company deserves much credit and admiration 
for the way it has overcome the disadvantages of ; a badly selected 
clay, by thorough mechanical treatment, still it is^under a handicap 
in using it. 

15~G. B. IX, 



226 



BULLETIN ELEVEN 



Summing up the various screens in use at the roofing tile plants 
of this country, the following list is obtained: 

TABLE No. 37. 

Showing Various Types of Screens in Use Among 

Roofing Tile Plants. 



Kinds of Screens. 


Number 
Plants Using. 


Number 
in Use. 


Gravity, inclined • . . . . 

Piano wire, inclined 

Shaking 

Perfect clay screen 

Centrifugal 

None at all* 


3 
3 

1 
5 
1 

1 


3 
3 

1 
6 
2 








*Using soft clay in a wet pan. 

Tempering^. — Tempering means the adjustment of the water content 
of a clay to the forming operation which is to follow. In the dry press 
the amount of water used is small, and in fluid casting the amount is 
very large, but the same word "temper'^applies to the adjustment of 
the dry press powder for pressing and the thickness of the slip for suc- 
cessful casting. 

In ordinary clay working processes, depending on the use of clay 
of plastic or pasty consistency, tempering means the regulation of the 
water content so that this plastic quality may be' most fully or at least 
sufficiently developed. This involves not merely the adding the water, 
but in securing its even distribution over and among all the particles 
of the clay. 

The modern conception of a plastic clay is that of a very stiff fluid, 
in which every grain of solid matter is surrounded by a liquid film or 
envelope, so that the particles are virtually in a state of fluid suspension. 
This has been discussed in Chapter III in connection with shrinkage 
and water of plasticity. 

It is evident that to get a piece of clay into such perfect temper 
that the preceding conception becomes true or approximately true, 
calls for a very complete disintegration of the solid particles, so that 
they may readily assume the new relation towards each other under the 
influence of water. 

The ease with which different clays take up water and assume this 
state of fluid suspension, or plasticity, varies ver}'^ widely. The chief 
causes of variations are physical. They do not center so much in the 
proportions of the *'clay substance'' or plastic elements vs. the sand or 
anti-plastic elements as was formerly believed. It has been shown 
that many rocks, powdered finely, yield more or less plasticity, and that 



GEOLOGICAL SURVEY OF OHIO. 227 

only a small amount of plastic clay may convert a large amount 
of otherwise anti-plastic matter into workable shape. The purest clays 
are often of low^ plasticity. 

The important factors affecting the plasticity of clays are those 
of pressure, consolidation, heat and infiltration of hardening or cementing 
substances, like bitumen, ferric hydroxide, or carbonate of lime. In 
the clays of the present time or Pleistocene geological period, like river 
flood-plain clays, glacial till and lake-bed clays, consolidation by pressure 
is at its minimum. These clays are all superficial and have never been 
covered by deep deposits or great weight. They are constantly being 
opened up by the infiltration of surface water, and frost, and vegetation. 
Such clays are alwaj^s easily brought to as much plasticity as their 
mineral make-up permits. They temper easily. 

Clays which had their origin in geological periods preceding the 
Tertiary are always much hardened by the vicissitudes of heat and 
pressure to which they have at various times in their long existence 
been subjected. These clays are generally hard and rocklike unless 
softened superficially by weathering. Tempering such clay means break- 
ing down the close, dense structure given by pressure and heat, and 
oftentimes dissolving out or loosening up the hardening solutions which 
have permeated the masses of mineral grains and filled the voids with 
a hard cementing filler. 

Clays which had their origin in Tertiary or later periods, down to 
the Pleistocene or present period, are as a rule much less hardened or 
fossilized, and can as a rule be made plastic with comparative ease, 
though they are by no means like the present clay, and locally have 
often been hardened as completely as the carboniferous or Devonian 
clays. 

Whatever the structure, and no matter how great the hardening 
produced by age or pressure or chemical infiltrations, it is possible to 
restore the plasticity of a clay by mechanical treatment, provided the 
plastic elements have not been destroyed by heat. Clay, when burnt, 
can never be made plastic again, and in nature temperatures of far less 
than red heat have so altered the clay minerals that their capacity to 
assume the plastic state is destroyed. Slates, for instance, are, miner- 
alogically, exactly like shales, except that they have lost three or four 
per cent, of their chemically combined water, and are non-plastic in 
consequence. This change was due to heat far below redness. 

From the foregoing it is evident that the amount of mechanical 
work to be expended in getting clays into the same physical condition 
of plasticity is sure to vary greatly. With some it merely means stir- 
ring up with a little water — the old-fashioned vertical horse pug mill 
used on soft mud hand brick yards; or still more elementary, the shal- 
low soak pits, and the tramping of th^ clay with the bare feet of laborers, 
as is still done in Mexican roofing-tile yards, amply sufficed. With 



228 BULLETIN ELEVEN 

others an intense stirring, under pressure, is needed, as is gisren in the 
better class of pug mills. With others, nothing less than long-continued 
grinding in the presence of water, uiider heavy muUers, will succeed in 
breaking down the rock structure of the fossilized clay. 

In general there are only two mechanical methods available — pug- 
ging vs. wet grinding. The old-fashioned, primitive foot-tramping can- 
not he considered as commercially possible today in a civilized country. 

Ptigf Mills. — Their general features are so well understood that they 
need not be described. There are many variations in structure, which 
are of benefit or otherwise, and of these it is necessary to speak. The 
dimensions run from six to twenty feet in length and from two and one- 
half to four feet in diameter for horizontal mills. Vertical mills are sel- 
dom used today outside of the pottery industry. The pug shaft is car- 
ried at the outlet end by a simple bearing, while at the inlet end provi- 
sion must be made to not only carry the shaft but at the same time to 
provide for the heavy end-thrust produced by the work of moving the 
clay forward and forcing it out through a limited aperture. This is ac- 
complished in the more simple mills by having the boxing cast with one 
end closed. This boxing, of course, must be very securely held in posi- 
tion, hence it is usually made a part of the rear frame of the tnachine. 
The cap or end of the boxing is turned out true and smooth, then a 
bronze disc of the same diameter as the shaft is slipped into the bear- 
ing. The end of the shaft now is brought into contact with the bronze 
disc. As a rule the entire bearing runs in oil in order to reduce the 
friction as much as possible and keep the bearing from heating. 

Pug mills are made with single shafts like that just described, and 
double shafts revolving toward each other. 

At the outset it should be understood that the work of a pug mill 
is not that of grinding a clay, but only of mixing and stirring it. If 
given a clay with only a slightly hardened structure and slightly latent 
plasticity, it is possible by means of a single shaft pug mill to develop 
the plasticity sufficiently for most clay working purposes; but should 
the clay be a little more hardened, it would be better to use the double 
shaft mill, or possibly a very long single shaft mill. 

The double shaft mill, while not giving twice the pugging action 
of the single mill, has a much greater capacity, thus making it possible 
to hold the clay under the action of the stirring knives much longer. 
Also by using a less number of propelling knives, or knives of a lower 
pitch with an increase of simple cutting and stirring blades, it is possible 
to regulate the passage of the clay through the pug mill until it has been 
throughly mixed. 

Pug mills are also built open top and closed top, the difference being 
that the pressure applied to the clay in mixing and cutting it by the 
knives is limited. The clay is free to move upward, and thus relieve 
the pressure. But with mills of closed top the delivery of the clay be- 



GEOLOGICAL SUKVEY OF OHIO. 229 

comes like that of an auger machine^ and uses a large amount of power 
and rubs the clay and water together so much the more intimately. 

No pug mill exercises a grinding effect on a clay. Particles of a 
single mineral are rarely if ever reduced in size by pugging. Agglomera- 
tions of particles of minerals, when not held together by some ce- 
menting material, may soften enough by water to come apart under the 
stirring action of the pug mill, but if they are at all hard or consoli- 
dated, they will not. 

The pug mill is fit, therefore, for tempering unconsolidated or recent 
clays of readily plastic character. It is out of place with clays of diffi- 
cultly plastic nature. 

It is possible to use pug mills alone with no grinding machinery 
whatever in the case of some soft alluvial and glacial clays. Also, it has 
been found that many clays, by dry grinding and careful sizing of grains 
to exclude all coarse matter, will develop a moderate plasticity by pug- 
ging sufficient for stiff mud manufacture. Thus pug mills are in use 
in hundreds of plants merely as stirring machines, the dry pan breaking 
up the rock structure and producing a powder, the screen keeping the 
maximum coarseness under control, and the pug mill mixing the powder 
with water. Wherever this process gives a sufficient plasticity it should 
be used. It is cheaper, easier, simpler in every way than the wet grind- 
ing. But it will not do the work of wet grinding in dealing with difficult 
clays, and should never be expected to. 

Wet Grinding* — The use of the wet pan as a preliminary grinder, 
beginning with the crude clay direct from the pit, has been briefly dis- 
cussed at the proper place. The use of the wet pan as a tempering ma- 
chine, with grinding thrown in incidentally, requires a little different 
construction and radically different opel-ation. 

Wet pans for tempering previously ground and screened clay use, 
generally, mullers varying from three to eight inches in face, while 
initial grinders usually have mullers with from ten to eighteen inch 
face. The crushing action is magnified in the latter, the cutting and 
mixing action in the narrower wheels. The weight of the muller is not 
necessarily less, for it is very common to see wet pan mullers with extra 
large hubs, which are added for their weight, it being desired to have 
the mullers cut through the mass of clay, and crush any particles that 
may be caught between them and the pan floor. The scrapers are also 
set differently, and are of different size, being designed as much to stir 
the mass as to direct it under the wheels. The use of large plows or 
scrapers becomes difficult with very plastic clays, for it requires exces- 
sive power to drive the pan, which is hard to drive in any case. 

The pan is most usually located on the ground floor, immediately 
below the bin of screened clay. A tube of wood or iron, provided with 
a valve, or cut-off slide, leads down from the clay-storage bin to within 
two or three feet of the pan floor. The operation of a pan is about 



230 BULLETIN ELEVEN 

as follows: The pan being run empty, the attendant opens the valve 
in the clay spout, and at the same time opens the water valve, letting 
a stream of water run into the pan. Only ten or twenty seconds are 
required to introduce a charge of from 600 to 1,000 pounds of ground 
clay and from 150 to 200 pounds of water. The stream of clay is then 
stopped, but the water is continued until the clay apparently becomes 
too soft and too sticky to use. As the grinding progresses however, 
this apparent excess of water soon soaks in and more water must prob- 
ably be added. If the grinding is continued a minute or so extra, 
additions of water must be let in from time to time, the excess being 
soon taken up by the grains of clay, as the subdivision proceeds. The 
original grains, if hard, would require but little water to wet their sur- 
face, but the finer they are ground, the more water w411 be needed to 
secure the usual apparent dampness of the same. When the clay is 
tempered to the proper degree, determined by. the touch or sense of 
feel of the operator, it is emptied out as speedily as possible. The 
time consumed in tempering a charge varies from two to four minutes 
usually, three minutes is a fair average in all the plants in which this 
operation has been timed. Of course, with some hard clays, or in an 
industry consuming small amounts of clay only, the time per panful 
will be increased. 

Unloading is done by a semi-mechanical, hand-actuated shovel 
in almost every plant where wet pans are used. A large shovel, pivoted 
to the frame of the pan on a ball and socket joint, or equivalent, is 
lowered into the revolving pan, against the direction of motion. The 
clay in its travel with the pan, rushes up the inclined plane of this shovel 
until it will hold no more. The amounts held are seventy-five to one hun- 
dred pounds at a time. The operator then raises the loaded shovel by 
bearing down on the handle, swings it over the rim of the pan and dumps 
the load onto a conveyor or elevator to be carried to the forming ma- 
chinery. Automatic unloaders of many types have been made and 
used successfully. Plows; scrapers, revolving buckets, mechanically 
driven shovels, pans with sectional rims, discharging by centrifugal 
force, etc., have been tried — all successfully. The problem is not 
difficult, mechanically. 

The fact remains that the old hand method still hangs on, and is 
set up by many as the great obstacle to the use of the wet pan. 

Operation of Wet Pan, — The wet pan gives the most thorough 
tempering that it is possible to give clay. The grinding action is a 
very important feature, especially with hard, gritty clays. The hand- 
ling of such materials in a pug mill is either impossible or requires the 
addition of a soft plastic clay to help it out or a long-aging period to 
permit softening to take place in order to make perfect ware. With 
the wet pan the same hard clay can in a few minutes produce as much 



GEOLOGICAL SURVEY OP OHIO. 231 

or more plasticity than could be developed by a pug mill treatment 
with unlimited time. 



Fig. 64— Wet Pan with Shovel. 

Should it be advantageous to mix two kinds of clays, the wet pan 
will do the work in a most satisfactory manner. The clays are actually 
blended until they form a new material, different from either of the 
two that were originally added to the machine in color and properties 
of burning. On the same class of work, the pug mill will only stir the 
two clays together, but will not in any way grind them one into the 
other as the wet pan would, and the color of the mixture is almost 
always specky, showing separate grains of both clays still maintaining 
their identity. 

While the wet pan gives very excellent work as a tempering machine 
it has some objectionable points. Among them are the following: 

First. Its cost of installation being about twice that of a pug 
mill, viz., $800 to $1,000. 

Second. Its consumption of power. In most clays it requires 
two wet pans to prepare the clay for one auger machine making roofing 
tile, and if brick are to be made , three or four wet pans would be needed 
for a moderate auger-machine output. The actual horse-power used 
varies enormously with the clay, the charge tempered, the consistency 
or wetness desired, etc. But it is never low and probably runs from 
twenty-five to forty horse-power on the average, when it has a charge 
grinding. While unloading and recharging, the power consumption 



232 BULLETIN ELEVEN 

drops and rises again, so that about one-third of the time is lighter 
duty and two-thirds heavy duty. 

Third, The clay is tempered in batches, and even with the utmost 
care, it is impossible to always get each batch to the same temper. 
With some clays it will be found that they will absorb water so fast 
that it will be impossible to empty the pan quick enough to have the 
last of the batch of the same temper as the first. This means that 
the clay will go to the forming machinery in an uneven condition, giving 
more or less trouble, such as uneven flow through the dies and a variable 
shrinkage. 

Fourth. The class of men required to operate them are hard to 
secure. They not only require a man with a keen sense of feeling and 
good judgment, but one of good physique also. Very often these two 
requirements cannot be found in the same person. It often happens 
that a man of light weight can determine the proper temper of the clay 
to a nicety, but will lack the necessary strength to operate the shovel 
continuously. The trouble is within the reach of mechanical methods 
however; where unloading devices are seriously desired, they will be 
found. 

Fifth. The irregular load of a wet pan is hard on an engine. When 
two pans are in the same shop this usually regulates itself, as one is 
discharging and filling when the other is grinding. 

While the wet pan has these bad features, it will be noted that they 
are largely of a mechanical nature. No fault can be found with the 
quality of work done by the wet pan, except as to possible variability 
of temper. This variability is also susceptible to mechanical regula- 
tion, by using weighing or measuring boxes for clay and water, instead 
of charging purely by judgment. The condition of the clay, day by 
day and hour by hour, would require adjustment in the quantity of water 
added per standard charge of clay, but this could easily be changed 
as found necessary and each consecutive charge of the pan would then 
vary only as the clay itself varied in initial water content. 

In the preparation of roofing tile clays, too much stress cannot be 
placed upon the advisability of having the clay thoroughly prepared. 
Good tiles cannot be made from insufficiently tempered clays. In the 
case of soft clays, like alluvial or glacial deposits, it is possible to develop 
their plasticity by pug mill treatment without storing the clay in bins 
to age for several days. In the case of the fossil clays, like shales and 
fire clays, it will be found that only in the softer varieties can the temper- 
ing or pugging be satisfactorily accomplished by the pug mill. 

Should the pug mill be used, it will be found in nearly all cases 
advisable to use the double shaft style, and then age the clay for a 
period depending on the hardness and other qualities of the clay or shale 
in hand. 



GEOLOGICAL SUBVEY OF OHIO. 



233 



TABLE No. 38. 

Classification of Methods of Tempering at the Various Roofing Tile Plants 

of the United States. 



Quality of Material 
to be Tempered. 



Shales . . . 
Shales . . . 
Shales . . . 
Shales . . . 
Soft Clays 
Soft Clays 
Soft Clays 



Rolls and 
Pug Mill. 



1 plant 



Pug Mill. 



5 plants 
2 plants 
2 plants 



Wet Pan. 



1 plant 



Both Pug Mill 
and Wet Pan. 



1 plant 



1 plant 



Aging. 



No. 

No. 

No. 

Yes. 

Yes. 

No. 

Yes. 



From the above table it will be seen that of the nine roofing tile 
plants using shales, only one is using wet pans exclusively, one other 
plant has both pug mills and pans in use, and seven plants are using the 
pug mills exclusively for tempering. It will also be noted that in only 
two plants using shale is aging of the clay being practiced. Of the 
soft clays used in the four plants, three are being prepared by pug mill 
treatment followed by aging. In the fourth plant, while the clay is 
not aged it is given a possible equivalent for aging, by first running the 
soft clay through a wet pan and then through a pug mill, before enter- 
ing a combined pug mill auger machine for forming the clay bar. 

It can be seen at a glance that the plants using soft clays are the 
ones giving the best preparation, while the plants working shales, a 
material that is slow to temper, are using the least pains to properly 
prepare their body. 

Far more trouble in roofing tile manufacture is due to improper 
tempering of clays than is generally thought. The improper flow of 
the clay through dies, resulting in warped and checked tiles in the dryer 
and kiln, is one result. It will also be found that most shale clays which 
pass direct from the pug mill to the auger machine, or other forming 
machinery, will have a tendency to form a rough bar, with corner or 
side checks. This is due to the weakness or lack of tensile strength of 
the granular clay, the coarse grains of which act as so much non-plastic 
material. 

Where tiles are made from clays direct from the pugging machinery, 
the harder grains generally will not have slaked or softened down in 
the limited time available since the tempering began. These grains 
subsequently soften in the dryer under the influence of time and heat, 
before the water is expelled. When they do soften, they not in- 
frequently cause changes of volume leading to cracks, warping, pimples 
and similar troubles. Where no outward signs of disarrangement are 
visible, it is possible that the tiles will suffer distortion in the kiln as a 



234 BULLETIN ELEVEN 

result of their defective preparation. Now had these same clays been 
prepared in a wet pan, using hot water for tempering, or had it been 
tempered in a pug mill with hot water, and then stored in bins to age, 
allowing the granular particles to disintegrate before being manufactured 
into tile, it is believed that less loss in the kiln and drj^er would have 
been the result. 

It is also believed that while the wet pan has some objectionable 
features, its use should be much more general in the roofing tile industry. 
The amount of clay used is relatively small and the price for the finished 
ware is relatively high when compared to brick, so that it is possible for 
the roofing tile manufacturer to prepare his clay better than in some 
of the other industries. 

Aging Clays in Connection with the Tempering Process — The method 
is most popular and most likely to be used is the pug mill treatment. 
This, however, should be done in the best possible manner. To properly 
prepare clay by pug mill treatment, no better machine can be recom- 
mended than a combined double shaft pug mill auger machine. The only 
machine of this type found in use was that of the J. D. Fate Co., Ply- 
mouth, Ohio. Of the fourteen plants working in 1908, nine of them 
were using this company's pugging machinery. The clay should first 
of all be ground to eighteen mesh or finer, and when fed to the pug mill 
should be treated with hot water, in slight excess of that needed to 
produce the proper temper for working. As the clay is worked along 
by the blades or knives of the pug mill, each particle becomes wet in 
the hot water; as the clay passes from the end of the double pug mill, 
it is fed into the auger machine part of the mill. Here it is compressed 
^ and packed into a dense mass by the time it is expressed from the die. 
By a suitable cutter, it should be cut into blocks of convenient size 
for handling and carried by conveyors to the storage or aging bins to 
go through a sweating process lasting from two or three days to a month. 
The time will depend on the nature of the material in hand. Some clays 
will slake in one-tenth the time of others. Some will never slake at all, 
and for such nothing but severe grinding treatment can be done. 

It cannot be denied that aging clay increases the cost of production if 
the process stops with placinfe the ware on the drying racks, but if the 
per cent, of the perfect tiles brought out of the kilns is increased by 
aging, then the work is justifiable. 

Among the foreign manufacturers, especially the Germans, the aging 
of clay is considered important. Nearly every plant has its "sumps," 
or damp cellar. The cost of labor does not stand so much in the way 
there as with our manufacturers, but where the European nations have 
cheaper labor with which to do their work, the American manufacturer 
has the advantage in more readily securing mechanical assistance. 
Such assistance could be secured in cheapening the cost of aging roofing 
tile clays. 



GEOLOGICAL SURVEY OF OHIO. 235 

Ordinarily, the German roofing tile manufacturer will elevate his 
clay by inclined track to the second or third story of his building, from 
whence it passes through sets of rolls, one after another, until it lands 
either on the ground floor or basement, where it is packed away in brick 
rooms or bins. After remaining in these *'sumps" the proper length 
of time, it is spaded out into small cars, elevated a second time to the 
upper stories of the building to again pass through rolls and pug mills 
before entering the final machinery for shaping. 

It is not at all improbable that in this exhaustive treatment lies 
the secret of the durability of the porous tile of the foreign countries. The 
average Anerican roofing tile manufacturer would say at once that he 
could not afford to handle and rehandle his clay as his German neighbor 
does; bul if it pays the German, with his low selling price for tile, it would 
unquestionably prove equally profitable in this country, where better 
prices are received. The extra money spent to age and better prepare 
the clay would be more than offset by the fajct that it would be found 
unnecessary to burn the tile so hard to make them frost-proof. The 
majority of American roofing tile plants are burning their tile to such 
a high degree of vitrification that great loss occurs in the kiln. Whether 
this is necessarj^ or not, it is certain that shale clays, especially the harder 
ones, have often given trouble from frost if not burnt until practically 
vitreous. It is believed that should these same shale clays be better 
prepared, complete vitrification would not be found necessary to pro- 
duce ware of good resisting qualities. 

Observations on the arrangements for aging the clay in the various 
American roofing tile plants showed them to be generally very meager, 
and inadequate. Usually, nothing more was done than to pile up 
stacks of clay in the vicinity of the pug mill. In a few cases some burlap 
was thrown over the top of the pile and wetted down from time to time, 
but most often the clay was unprotected, and dust from the dry pan 
was found settling on the surface, assisting to absorb* the water from the 
rapidly drying surface. 

To carry out aging properly, cellars or chambers should be pro- 
vided, into which the clay can be delivered by belt. These chambers 
should be shut up or made reasonably tight, and water should be avail- 
able for wetting down the floors, walls and clay coverings from time to 
time in order to keep the air saturated at all times. This would permit 
the clay to retain its moisture rather than giving it up to the air. 

Without question, the best tempering of clay in this country for 
roofing tiles was seen at the plant of the Ludowici-Celadon Company, 
at Ludowici, Ga. The method employed at this plant has in part been 
discussed elsewhere, but will be restated. The clay, upon being dumped 
from the bank cars into a hopper, is fed through a pair of large rolls, 
which squeeze and crush the lumps. It then passes into the combined 
pug-mill auger-machine of the J. D. Fate Company, where it is thor- 



236 BULLETIN ELEVEN 

oughly mixed and worked by the double pugging arrangement before 
being passed into the auger, where it is compressed and expressed in 
column form, like the bar used in side-cut brick making. This bar is 
cut into blocks of convenient size for handling, which are carried by 
conveyors to open-top storage bins where the blocks are unloaded by 
hand and packed tightly in the bins. It remains here a week, and is 



Pig. 63 — Combined Pug Mill and Auger Machine, as built by the J. D. Fate Co. 

then spaded out, loaded onto a second conveyor, which takes it to another 
pair of rolls similar to the first except that they are set nearer together. 
The clay exudes from this second set of rolls in very thin sheets, being 
scarcely thicker than blotting paper. From these rolls the clay falls 
into a second Fate combined pug-mill and auger-machine, where it is 
thoroughly reworked and expressed in blank forms ready to be fed into 
the roofing tile presses. 

It should be borne in mind that the above treatment is given to 
an unconsolidated clay that is by nature extremely plastic. The prep- 
aration given it is not to develop more plasticity, but to bring the clay 
to its best condition for density and for toughness and for flowing 
through dies — in short, to make the soundest, solidcst tiles possible. 

If this company finds it justifiable to prepare a plastic alluvial clay- 
in this exceedingly thorough manner, it should prove a fruitful topic for 
thought with some of the other manufacturers who are making tiles from 
comparatively plastic shales. 

Scumming or Efflorescence of Roofing Tile Gays. — It is well known 
that many roofing tiles develop a scum, or white efflorescence, either in 
the drying or the burning, and occasionally after they are placed in 
position on the roof. 

This scum, or efflorescence, is due to the presence of salts in the 
clay, shown by repeated chemical analysis to be chiefly the sulphates 
of lime and magnesia, and less frequently sulphates of iron alumina and 
the alkalies. Other salts, such as chlorides, nitrates or organic acid 
salts, may also be present and form scums. 



GEOLOGICAL SURVEY OF OHIO. 237 

Nearly all common clays and shales contain or have contained sul- 
phur in the form of iron pyrites, and frequently in addition the carbonate 
of lime and magnesia. 

When a clay containing the above minerals is exposed to the action 
of the air and moisture, the pyrites oxidizes to sulphate of iron and free 
sulphuric acid. The sulphate of iron, and especially the sulphuric acid, 
reacts with any of the carbonate minerals that may be present, forming 
sulphates, like gypsum, epsom salts, etc. Also, other minerals are likely 
to be decomposed, though less readily than carbonates, yielding salts of 
alumina, the alkalies, etc. If the clay has not been exposed to the action 
of the air — that is, not weathered — the pyrites is likely to remain un- 
oxidized during working, and hence relatively harmless, though still 
undesirable. The other minerals will, therefore, probably remain in- 
nocuous, though some clays contain already in themselves water-soluble 
minerals like gypsum, already formed when the clay was laid down. Such 
clays are usually too impure to work, and hence do not come into serious 
consideration. Carbonate of lime or magnesium may be present in 
large quantities; sometimes in glacial and alluvial clays they may be 
present in large fragments or as gravel. These carbonates are not easily 
soluble in pure water. They do not give so much trouble, but with 
carbonated water they are more soluble. In wares of thin section, like 
roofing tiles, t-hese carbonates may be changed to sulphates by the ac- 
tion of the sulphur gases of the kilns. Unless the tiles be so hard burned 
or vitrified as to prevent water absorption, it may be found that after 
they are on the roof they will show signs of whitewash, due to the 
rainwater soaking into them and dissolving out these sulphates and then 
depositing them on the tile's surface as the water evaporates. 

The soft, or bituminous, coal used for burning contains sulphur in 
the form of iron pyrites as well as organic sulphur compounds. When 
such coals are burned, the iron sulphide gives off gaseous sulphur 
dioxide or trioxide. These gases pass through the kiln, combining with 
any water or moisture to form sulphurous or sulphuric acids, which, as 
stated above, readily forms sulphates from the carbonates. 

It is for this reason that often when tile are set wet they will come 
from the kiln coated with white. The damp tiles very easily absorb 
the sulphur gases, forming acids, which in turn form soluble salts or 
dissolve materials not otherwise soluble, and then, as the heat increases, 
the acid is driven off, leaving the dissolved salts behind on the surface 
of the tile. 

There is still another source from which efflorescence may arise, 
viz., the water used for tempering. Water taken from wells and streams 
is more or less impregnated with salts dissolved in it. These salts are 
usually the bicarbonates of lime and magnesium, and also the sulphates 
of the same bases. If in large enough amounts, these salts will cause 



238 BULI^TIN ELEVEN 

whitewash, the same as though they had originally been in the clay. 
Salts may also be obtained from the mortar used in bedding the tiles, 
though this is not a common thing in the American system of laying. 



Pig. 65-A — Combined Double-Shaft Pug Mill and Auger Machine. 

Pfcventioa of Efflorescence. — To cure a disease it is necessary 
to remove the cause, and the same principle applies to efflorescence. 

In the latter case, we can apply the following methods: 

First. Free the clay entirely from soluble salts, by washing it 
thoroughly. This is theoretically possible, but practically is too ex- 
pensive. Water of sufficient purity is seldom attainable. 

Second. Use the clay straight from the pit before the salts have 
a chance to form through the influence of weathering of iron pyrites. 
This is generally feasible, though disadvantageous in other respects. 

Third. Prevent the formation of the salts by rapid drying and 
water smoking. 

Fourth. Avoid sulphury fuels for drying or burning. 

Fifth. Change the soluble salts to insoluble ones by chemical 
additions to the clay or the water. 



GEOLOGICAL SURVEY OF OHIO. 239 

Sixth. Paint the surface of wares with tar, or some similar agent, 
which will not evaporate or soak in, but will drive the water to escape 
from the untreated portion of the surface. When the tar burns off 
later, no scum is foimd where it was. 

Seventh, Application of a coating which on drying peels off in 
flakes, carrying the collected salts w^ith it. This method has never 
been used in this country, but was patenlied in Germany about eight 
years ago. 

Taking up the first method, that of washing the clay or weathering 
it. The white-washing salts are all soluble or can be made so by weather- 
ing. The action though, is slow, and to be properly done, the clay 
must be spread in thin layers upon a sloping floor, either natural or 
prepared, so that as the rains w^sh through the clay dissolving the 
salts they may be drained away. Otherwise salts will accumulate in con- 
centrated form at the bottom of the weathering pile. This method requires 
the rehandling of the clay, and as the work to be well done must be 
extended over a long period of time, it becomes necessary to have ex- 
tensive weathering areas or floors. Hence in a practical way, this 
method is too expensive and should not be considered. 

The second method. While extensive weathering will prevent 
white w^sh, a short period of weathering is very likely to cause the 
same in a clay that might otherwise be free. As stated before, the 
sulphates which are soluble are chiefly the results of the weathering 
of iron pyrites. Hence by working a clay containing pyrites, into 
ware as quickly as possible, it is often possible to prevent these salts 
from being formed. 

The third method, that of rapid drying and burning, depends 
largely on getting the tempering water out of the tiles as speedily as 
possible. Just why the same quantity of water will cause a scum on 
the surface of a clay if evaporated slowly, in a steamy atmosphere, and 
will not if the drying be pushed vigorously, is not yet fully understood . 
It is an unquestionable fact nevertheless. The clay seems to act like 
a filter, holding back the salts in quick drying, but if time is permitted, 
they work through the filter and reach the outside at last. It is un- 
questionably largely due to causes two and three, that many of the 
roofing tile plants are troubled with scum at certain times and not at 
others. Especially is this so in the winter months, when the drying is 
more likely to proceed slower than during the summer. Also it is 
usual to draw the material largely from storage piles which have been 
air weathering from the previous summer, and this air weathered clay 
often causes scumming, which is avoided when working direct from 
the pit. 

Fifth method. This method is the one most universally used, 
not only in the roofing tile plants, but in all other branches of the clay 
industries. Without going into detail as to the various agents that 



240 BULLETIN ELEVEN 

might be used for the above reaction, it will suffice to say that the com- 
pound used must necessarily be cheap and easily handled. So far, 
some salts of the element barium have been found the most effective, 
especially the carbonate and chloride. More often the former is used. 
When either of these salts is added to a clay containing soluble 
sulphates, one of the following reactions takes place. 

Ba COa+Ca SO. = Ba SO. + Ca CO, 
Ba CI2 +Ca S04=Ba SO.+Ca CI, 

Thus, barium sulphate is formed in either case, which is one of the 
most insoluble compounds known. Hence, when the calcium or mag- 
nesium sulphates have been acted upon by the barium carbonate two 
insoluble compounds are formed, both inert to the action of the temper- 
ing water or kiln gases. No scum can form, as nothing remains soluble. 
Barium carbonate in itself is only slightly soluble. In order to get it to 
react with the sulphates, it is necessary to have the two in actual contact. 
•The problem thus arises how to best accomplish this end. In most 
plants, it is customary to add the barium at the wet pan or pug mill, 
at the time the water is added for tempering. For some clays low in 
soluble salts this method will do, but frequently with pug mill treatment 
it is not sufficient. In some plants they add the barium at the dry 
pan, thus getting a better mixture. In others, large blunging tanks 
into which the tempering water and barium are added are provided 
for, and the latter is kept in suspension by revolving paddles. The 
barium introduced in suspension in the tempering water is more apt to 
become closely in touch with the sulphates than if added dry. 

While the chloride of barium is easily soluble, its use is not to be 
recommended, because any excess above that required to counteract 
the sulphates may be drawn to the surface and itself form a scum by 
the evaporating water. Also, the product of its reaction with lime 
salts is chloride of calcium, which is very soluble, and forms a scum, 
though not so permanent or troublesome a one as the sulphates. Then 
too, any soluble form of barium is an active poison, so that the use of 
the chloride should be attended with much care. 

By weight, 172 parts of calcium sulphate requires 197 parts of 
barium carbonate, or in other words, for 1 part of the sulphate it will 
require 1.15 parts of the barium carbonate to counteract it. 

Taking for example, a clay containing 0.1 per cent, calcium sul- 
phate. Owing to inability to get the barium evenly distributed through- 
out the mass of clay, it has been found from experience, that there 
should be added a large excess over the theoretical quantity, in the 
neighborhood of ten times as much barium carbonate as is theoretic- 
ally required. Thus with barium carbonate costing two and one- 
half cents per pound, and a clay containing 0.1 per cent, calcium sul- 



GEOLOGICAL SURVEY OF OHIO. 241 

phate, there would be required for a square of tiles, weighing 1,000 
pounds, approximately twelve pounds of barium, costing thirty cents. 
While this would be an added expense, its use would not be prohibitory. 

It very frequently happens that the large hand-made ware about 
a roofing tile plant is the only class that gives trouble from white wash. 
In the light of what has been written in the last few pages, it will be 
easy to understand why this is so. The tile made by machinery passes 
directly into the dryer and is very quickly dried, while the thick, heavy 
ware made by hand is allowed to stand for days, in order to dry slowly. 
Then upon going to the kiln, it is much more likely to be damp than 
the tiles. So that the slow drying combined with the possible kiln 
dampness is very apt to promote the formation of soluble salts in and 
on the hand-made ware, where the regular tile will escape it. 

It has been the custom in a few of our plants, and more frequently 
in the old world, to coat or paint the newly made terra cotta pieces with 
tar or oil, on the exposed or face side. This coating of tar or oil will 
cause the water that is in the piece to evaporate from the inner or oppo- 
site side, thus depositing the greater part of the salts where they will 
not be objectionable. Any salts that have formed under the tar or oil, 
will very likely be broken up or reduced as the tar burns off, liberating 
the sulphur which passes off with the kiln gases. This method of pre- 
venting scum on special made pieces was used by the writer in 1899 
with remarkable success. 

There is also a custom among a very few plants at the present time 
to add a small per cent, of black oxide of manganese with the barium 
carbonate, it being claimed by those using this method that the manga- 
nese helps very materially in preventing the scum. It is possible that 
the manganese acts favorably in hiding the scum. At least, where 
used it was impossible to find a white washed tile. But no chemical 
grQund for this practice can be discovered, and it is probably unnecessary 
and without result. 



16— G. B. 11. 



242 BULLETIN ELEVEN 



CHAPTER V. 

THE MANUFACTURE OR FORMING OF ROOFING TILE, 

In the preceding chapters, the selection of the clay and its prepara- 
tion in the form of a stiff mud or plastic paste have been discussed. 
The fashioning of this plastic paste into the various simple and compli- 
cated shapes found in the roofing tile industry forms the subject of this 
chapter. 

As in the manufacture of nearly all other clay products, there are 
a number of different methods of attaining approximately the same end, 
and also, the same method may be applied to producing a variety of 
different products. Exact classification is therefore difficult. 

MECHANICAL APPARATUS FOR RCX)FING TILE MANUFACTURE. 

Roofing tiles are produced by at least four different methods: 

First — By exclusively hand molding. This is the simple archaic 
process which has originated in every part of the world when the use 
of roofing tile was first attempted. It is not to be considered as a serious 
manufacturing method to-day, especially in this country. It can still 
be foimd in use, however, in Mexico and many coimtries where labor is 
cheap and ignorant and machinery expensive. 

Second — By use of a hand power press or machine. 

Third — By use of a mechanically driven power press. 

Fourth — By forcing out the clay through a die of proper cross 
section, and cutting up the resultant column or bar into tiles of proper 
length. 

Neglecting the small and unimportant output made by hand or 
by hand presses, we may say that the roofing tiles of to-day, in America 
at least, are made either by the fourth or a combination of the fourth 
and third methods given above. The fourth method is applicable to 
the production as finished tiles only of simple forms of the shingle, 
Spanish and interlocking patterns. The true interlocking tiles cannot 
be made by this method. As they are the most important varieties of 
roofing tiles, it follows that the combination method of manufacture, 
by forming the clay into clots or blanks, of the proper size, shape and 
weight by means of the flow die process, followed by their pressing into 
finished roofing tiles by some form of power press, is the most common 
and must important process of manufacture to-day. There are, there- 
fore, two important types of machinery to consider: viz. first, the flow 
die machines, which may produce a finished product by themselves 



GEOLOGICAL SUBVEY OF OHIO. 243 

alone, but are most widely used as preparatory machines to form blanks; 
and second, the power presses, which cannot economically be employed 
except when fed with prepared blanks, but which are necessary as the 
final step in all but the simplest forms or designs of roofing tiles. 

FLOW DIE MACHINES. 

Whenever plastic clay is subjected to pressure, it tends to obey 
the laws of a fluid, by transmitting its pressure equally to all parts of 
the mass, and by escaping by flow, through any and all orifices which 
may be accessible. Plastic clay is far from being a perfect fluid, but 
under high pressures it is capable of flowing very much like a fluid would, 
and through very small aperatures. Whenever the pressure ceases 
the parallel also ceases, for the erstwhile fluid at once stiffens to a more 
or less solid mass, retaining the form received during its period of flow. 

There are two types of flow-die machines, differing in the mode of 
applying the pressure to the clay: first, the plunger or piston machines, 
and second, screw or auger machines. The former comprise several varie- 
ties, while the latter are to a much larger degree true to one single type. 

Plunger or Piston Machines* — Thei« are several types of these 
machines. The direct acting, where a piston is made to press the clay 
ahead of it, by means of steam, compressed air, or water or oil under 
pressure, and the indirect, where the piston is actuated by some form of 
mechanical gearing, cams, cranks, levers, screws, etc. These various 
devices have been evolved in connection with the sewer pipe and brick 
industry chiefly, and only one plunger machine was found in use in the 
American roofing tile plants. This was at the works of the Cincinnati 
Roofing Tile and Terra Cotta Co., at Winton Place near Cincinnati. 
In this machine, the clay is pushed out by a movable head or piston 
working back and forth in a rectangular chamber. The head is moved 
by an eccentric or crank shaft and connecting rod. 

On the back stroke, or as the head is drawn back to its stopping 
point, an opening into the clay chamber is disclosed. Into this opening 
a quantity of clay is fed, and as the plunger head comes forward it 
pushes the clay ahead of it. After a suflicient amount has been added 
to fill the front of the chamber, the clay will be seen to issue from the 
die in spurts, corresponding to each forward movement of the plunger. 
Naturally the flow cannot be continuous, as in the case of the screw or 
auger machine, but is always intermittent in a reciprocating machine. 
The length of flow — or, in other words, the distance that the column 
will issue from the die at a stroke — will depend on the amount of clay 
fed into the machine at each stroke by the feeder. It is only natural 
to expect the results from a mechanically geared plunger machine to 
be variable and unsatisfactory. After each stroke of the plunger the 
issue comes to a full stop. Then, as the new charge packs, consolidates 



244 BULLETIN ELEVEN 

and comes forward, the column shoots out of the die at a high speed, 
diminishing as the plunger reaches the most forward point in its stroke. 
The irregular speed means that the clay has very little time to adjust 
itself to the conditions existing in the die. Then, further, there is always 
more or less wastage, due to the fact that the feeder is unable to 
adjust the feeding so that an equal length is issued each time. Hence, in 
order to be sure to have sufficient clay bar issue to make the proper 
length for a tile, the extra clay must be added each time. This extra 
material is cut off as waste, and must be rehandled to get it back to 
the machine again. The difficulty of regular feeding and the ill effects 
of irregular feeding are both apparent. It would seem as if some pre- 
liminary machine to pack the clay into a compact mass, of which a. 
uniform quantity could be fed with each stroke, would materially help 
the performance of the geared plunger machine. 

In this connection a small auger machine, through which the clay 
could be run in a continuous column, has been suggested. By means 
of a simple cutter, this column could be cut into lengths which would 
contain just the necessary amount of clay for each tile. By having 
the auger and cutter located above the plunger, it would be possible to 
so speed them that the feed would be automatic. 

However, if the auger machine were added, it would prove better 
to dispense with the plunger machine, and run the tile on the auger 
machine direct. As before stated, the plunger machine has many dis- 
advantages which are largely overcome by the use of an auger machine. 
Another handicap of the geared plunger machine is that it is speeded 
to give a definite, limited number of strokes per day. Every time a use- 
less stroke is made, or the tile is spoiled, just that number will be cut 
from the day's output. For instance, all of the clay cannot be expressed 
at each stroke; in fact, a large amount is retained in the head of the 
machine to.act as a cushion. This excess clay will become too dry or 
hard, which necessitates the removal of the head plate of the machine 
two or three times a day, and pushing the great lump of hardened 
clay out, to be returned to the tempering machine. Much time is lost 
in this way, or, in other words, many strokes of the piston, each of 
which should produce a tile, are lost. Other interruptions also inter- 
vene in the same way. Further, the plunger machine has a fault char- 
acteristic of itself in that it entraps air into the bar of clay more than 
any other type of machine. The piston, coming forward, closes the 
feeding opening, and compresses the clay so quickly that but a part of 
the air is able to escape. This entrapped air may escape in part around 
the plunger head, but what cannot escape in that way must pass out 
with the clay bar. It may show as blisters on the tiles, or may produce 
laminations or open cavities inside the bar. In the case of hard-burned 
tiles it is not likely that these laminations will give trouble; but should 



GEOLOGICAL SURVEY OF OHIO. 245 

the tiles be under- or soft-burned, then water may accumulate in these 
open spaces and freeze, and the tile will then surely go to pieces. 

With the intermittent flow of clay from the plunger machine, it is 
not necessary to use a reel or continuous cutter. A simple hand cutter 
is all that is necessary, as there is time to cut the tile and remove it 
during the return of the piston to its starting point. This cut-off is 
simple and easy to operate. 

About the only thing that can be said in favor of the plunger ma- 
chine is that it allows the cutting and ofifbearing of the tile to be accom- 
plished with more care than when using the trowel method for the re- 
moval of the product of a continuously moving bar. The average out- 
put of this plunger machine at this plant is about 4,500 tile per day, as 
against 10,000 to 12,000 by the use of an auger machine, employing 
the same number of men in each case. This shows that the additional 
time for handling must be considerable. 

The use of this geared plunger machine, with its limited nujnber 
of strokes per day and its small output per stroke, is by no means the 
best that could be done. The direct-acting plunger machines, using 
steam cylinders as the motive power, are very much more efficient in 
sewer pipe, brick and hollow tile manufacture, and can handle large 
tonnages per day. Their gain lies not only in the larger capacity of the 
cylinders, but in the delicately controlled power by which the flow can 
be regulated to a nicety. The last clay in the cylinder can be expelled 
at substantially the same rate as the first, and as fast or as slow as is 
desired. By cutting several tiles at one stroke, the proportion of waste 
could be very materially reduced. In fact, the Cincinnati machine rep- 
resents about the low-water mark of plunger machinery operation. 

The faults of bar structure and the intermittent nature of the flow, 
however, are matters that cannot be overcome by any plunger machine. 

Screw Of Auger Machines. — The general principles of the auger ma- 
chine are well known, and require no extended description. Essentially 
it consists of a barrel, usually horizontal, and either cylindrical or conical 
in shape, through which runs a center shaft, which carries a series of 
cast or forged sections which combine to make a more or less complete 
screw. The clay is fed into the rear of this barrel, and is carried forward 
by the screw, and forced out of a more or less constricted die in the front 
in the form of a continuously flowing bar or column of clay. 

The different makes of auger machines have naturally played al- 
most all possible variations on the different features of the auger ma- 
chine. For instance, the shape of the barrel varies from a pure cylinder 
to a pure cone, or combined part cylinder and part cone, and in some 
cases they are of oval or elliptical cross-section. The frame varies from 
cast iron to structural steel. The driving may be done by single gears, 
double,, or even triple gears, with ratios ranging from four to one up to 
twenty to one. The driving mechanisms include belts, which are the 



246 BULLETIN ELEVEN 

important method; direct connections to shafts by gearing; electrical 
drive; and rope drive. The auger shaft may be cast or forged. It may 
be equipped with a complete screw slipping on in sections, or it may be 
a series of forged knives or blades, set so as to collectively form a highly 
interrupted screw. The thrust block or bearing at the rear of the auger 
shaft is like the st^p of the dry pan, the point where trouble is first 
likely to manifest itself. The enormous forcing power of the whole ma- 
chine is concentrated on this one point, and heating is very sudden if 
the lubrication is imperfect or the alignment of the end plates gets dis- 
arranged. Auger machines also vary enormously in size, from giants 
able to force out five hundred tons of clay through a two and one-half 
inch by four inch nozzle in ten hours, down to toy sizes that will scarcely 
make ten tons of ware. 

Auger machines have been developed most extensively with an eye 
to the brick industry. Their use in producing hollow goods of all sorts 
and roofing tiles is distinctly of secondary importance. Hence we find 
the auger machines used in the roofing tile industry are usually the 
smallest sizes of brick machines equipped with the dies. Only a few 
auger machines have been developed especially for roofing tile purposes. 

The critical features of the auger machine are : First, the auger for 
forcing the clay out; second, the die, through which it is forced. All 
other parts of the machine may be built in various ways without spe- 
cially affecting either the power required to drive the machine, the quan- 
tity or quality of the output. They may, of course, affect the size, weight, 
frequency of breakdown, ease of access for repair, etc., but they are 
not essential points. 

The auger, or screw, as before stated, may be made in sections to 
slip on the auger shaft, one after the other. In some cases the fittings 
are merely blades set with a slight spiral twist, and forming a slightly 
interrupted screw, and sometimes they are a set of steel-forged knives 
set at a variable lead at different points on the shaft. However, in all 
cases the effect secured is that of a screw. 

■ 

The front end of the auger shaft is fitted with a casting having a 
spiral thread of large pitch, making one or more complete turns around 
the core, or axis. This casting is called the auger. It is designed to 
gather up and compress the clay delivered to it by the segmental screw 
made by the knives or blades farther back on the shaft. While the clay 
is being compressed it is being pushed forward to the die, through which 
it passes under much pressure, taking its final shape as it comes out. 

The auger may be made up of a single spiral, in which case it is 
necessary to have a spacer or collecting chamber placed between the 
end of the auger and the back end of the die. This is necessitated by 
the clay coming from the auger in a single stream, which follows the 
turns of the auger about the die entrance. Should the auger and die 
be placed too close together, it would be found that the column of 



GEOLOGICAL SURVEY OF OHIO. 247 

clay issuing would not flow regularly and true, but would wabble or 
lunge from side to side as the opening in the auger passed from side to 
fide. By putting in the spacer and making a collecting chamber^ it will 
be found that the unequal or irregular pressure of the auger is overcome 
in part or completely. The character of the clay as to slipperiness, and 
the necessity for the product to be sound or devoid of structure marks, 
will determine whether this type of auger is suitable or not in any given 
ease. 

For instance, in Chicago common brick yards, a single-threaded 
auger of large pitch is used, and enormous quantities of brick are made 
per day from a fat, sticky, slippery clay. The structure is very bad in- 
deed, the bar being composed of spirally disposed layers, separated by 
laminations or unbonded zones. For the purposes in view this bar 
structure is a matter of indifference, and quality and smoothness of 
exterior are the only criteria. 

For a paving brick plant such a course would be out of the question, 
for a bar as nearly devoid of laminations or spiral structure as possible 
is here necessary. 

In these cases augers are made with two threads, or "double bitted." 
This style of auger overcomes to a large extent the trouble of the single- 
thread type in that the clay is delivered to the die in two streams, which 
blend into one another and make a more regular and uniform feed. In 
the manufacture of brick it is rarely necessary to go beyond the double- 
threaded auger to get a bar of even flow and good structure, at least with 
the intervention of a collecting chamber. 

In some brick clayis a poor structure results even with a double- 
threaded auger and intermediate collecting chamber between the front 
of the auger and the back end of the die. The length of this chamber 
is of great importance. It must be determined by experiment in each 
case. The correct distance is manifested, when found, by a greatly 
improved structure of bar. 

In some cases, chiefly for products like shingle tiles, drain tiles, or 
bars of small cross-section and hence of exaggerated tendency to lamina- 
tions, augers of three threads are employed. They look almost like the 
propeller of a steamship. The three streams of clay, blending into one, 
do away with uneven or convulsive flow to a very complete degree. The 
clay is delivered to the die in a steady, continuous feed, with equal 
pressure over the entire area of the die at all times. It is thought that 
a short collecting chamber, even with a three-wing auger, would be 
advisable, though at the United States Roofing Tile Company they use 
none, and the distance from auger to die is only two inches, and a bar 
of good structure is obtained. 

Should a single-wing auger be used for roofing tile, it should be 
provided with a lip, or projecting flange, along the edge to prevent the 
clay from slipping or working back while under pressure. The collecting 



248 BULLETIN ELEVEN 

chamber should be long — say twelve or fifteen inches. This will per- 
mit of the equalization of the flow and break up the laminations in part, 
but at the same time it will require a great deal more power to operate 
the machine. 

The auger, assisted by the more or less interrupted screw behind it 
on the auger shaft, constitutes the propelling force of the machine. The 
die is the shaping mechanism, which forms the clay into a bar of the 
desired cross-section. A flow-die is simply a tube through which the 
stream of clay flows. It limits the shape or cross-section of the clay 
bar on two axes; the third axis, being the line of flow, is indefinite and 
unlimited. 

The nature of this tube is, however, a matter of the gravest concern 
for on it depends the smoothness or surface perfection of the clay product. 
If the tube is perfectly straight — that is, of the same dimensions from 
end to end — the bar would be of bad structure and the power required 
to operate it would be enormous. If the tube be conical, with a larger 
area in the rear next the auger, and a reduced cross-section, the clay 
will feed into it better and less power will be used. But if the nozzle is 
the smallest point in the tube, the bar would tend to rufile, or flow with 
a rough, cracked or scarred exterior. The usual plan is to combine a 
conical or sloping cross-section for the rear half or two-thirds, with an 
almost if not quite uniform cross-section in the front portion. 

The bar thus formed in the rear of the die compresses and elongates 
as it slips forward and in the front portion is "slicked up," or smoothed 
for its final surface. 

The variations in dies are innumerable. Only a few will be dis- 
cussed here, and those chiefly in connection with the plants or ma- 
chines in which they were observed. 

The following auger machines were observed in use in the roofing 
tile plants of the country: 

The Mttrray Machine* — This machine is the most largely used in 
the manufacture of shingle tiles. It was desigi^ed by Mr. A. H. Murray, 
of Cloverport, Ky. Its pugging chamber is short, and situated a little 
above and attached to the case containing the auger. The auger and 
die are the important part. 

This machine is simply a small combined pug mill and auger ma- 
chine. The pugging chamber is not over four feet long, the auger case 
and die possibly two feet more. It is only about four feet high. When 
these figures are compared with those of the ordinary sizes of combined 
pug mill and auger machines, it will be seen that it is very small indeed. 
The clay has to be prepared by other pugging or tempering machinery 
before being fed to the Murray machine. In the Murray machine the 
die is made to act as a collecting chamber and a die at the same time. 

Four plants were found to be using the Murray machine. The 
Huntington Roofing Tile Company, two machines; the Murray Roofing 



GEOLOGICAL SURVEY OF OHIO. 249 

Tile Company, one machine; the Ludowici-Celadon Company, at Chicago 
Heights,. Ills., one machine, and the same company, Ludowici, Ga., 
one machine. While this machine is small, its output is equal to that 
of the larger machines, averaging daily about 12,000 shingle tiles. The 
main difference, however, lies in the fact that the clay must be run 
somewhat softer than it is in the larger machines. This point is not 
a serious objection, except that a higher shrinkage of the tile is likely 
to be encountered, and this high shrinkage is very apt to produce a 
larger per cent, of twisted tile. 

The combined pug mill auger machine made by the J. D. Fate 
Company, of Plymouth, Ohio, is apparently very popular among the 
roofing tile manufacturers. Not less than six of these machines were 
found in use. There were three dilBferent sizes, named the "Hummer," 
the "Premier," and the "Imperial," of which there were two each. 

The main reason for the popularity of the Fate auger machine 
is that the double shaft pugging-part gives the clay a very good mixing 
or working before it enters the auger. Also, the head of the machine 
is so arranged that it is very easily opened for cleaning and changing 
dies. The strength of the machine is such that little trouble has been 
encountered from break-downs. It is true that other makes of ma- 
chines on the market meet the same conditions, but so far they have 
not been able to force their way into use to nearly as large an extent as 
the Fate machine. 

The American Clay Machinery Company, of Bucyrus, has four 
auger machines in the roofing tile industry, viz., at the New Lexington, 
plant of the Ludowici-Celadon Roofing Tile Company a No. 1 "Giant" 
and a No. 2 "Giant" at the Alfred plant of the same company, a "Cen- 
tennial," originally made by the Frey-Sheckler Company (now the 
American Clay Machinery Company); at the Alfred Clay Company, 
Alfred, N. Y., a No. 2 "Giant." 

The Bonnot Company, of Canton, Ohio, has one auger machine 
in use in the roofing tile field, viz., at the New Lexington plant of the 
Ludowici-Celadon Company, where a No. 2 Bonnot is used for shingle 
tiles, blanks and other work. 

Mueller Brothers, 2935 Clark avenue, St. Louis, Mo., make a small 
auger machine for the roofing tile industry, the distinguishing pecu- 
liarity of which is the use of two parallel auger shafts, whose streams 
unite in one die to produce a single bar of clay. They sell the larger 
part of their output through the Illinois Supply and Construction 
Company, of St. Louis. These machines are in use by the Mound City 
Roofing Tile Company, and the Detroit Roofing Tile Company, and 
single shaft machines of the Mueller plant are in use in the laboratories 
of the Ohio State University, at Columbus, the Bureau of Standards, 
at Pittsburgh, and Edward Orton, Jr., at Columbus. (See figure 19.) 



250 BULLETIN ELEVEN 

As to the success of these small machines, there is not much to be 
said, because the companies using them are not working them at all 
closely to their limit. However, at one of the plants, the objection is 
raised against them, that the augers will wear unevenly and the feed of 
the clay into the die then becomes unequal on both sides of the tiles, 
causing one side of the tiles to run faster than the other. Such tiles, 
of course, cannot be used on account of the warp or bow given them. 
These machines are much too light for heavy or continuous work. The 
clay has to be run much softer than it otherwise would. 

It seemingly is somewhat difficult for many people to Understand 
that it takes more power to run roofing tiles through a die than it does 
ware of larger cross-section, the reason being that the proportion of 
frictional area in the case of tile is far greater in proportioa to the quan- 
tity of clay than it is in the case of side-cut brick for instance. Many 
have thought that because very little clay is used in tile, that it only 
requires a small, light machine to handle it. Such is far from the case. 
The auger machine for making roofing tile should be built upon gen- 
erous lines, with much strength, so that the tiles can be run from stiff 
clay and put under much pressure in passing through the die. The 
actual barrel or drum of the auger does not necessarily need to be large, 
but the auger and its thrust-block should be given much attention. 
The gearing should be strong and accurately made. 

Cutters. — After the clay has been extruded from the die in the 
form of a continuously moving bar, the question of cutting it up into 
lengtljs while in motion is to be overcome. Automatic cutters, moving 
at the same speed that the bar moves, are produced by practically all 
manufacturers of auger machinery. These necessarily are adapted, 
each to some special tile, and for this reason will be discussed in con- 
nection with the machine and the plant where they were seen in operation. 

A large part of the work of auger machines in the roofing tile plants, 
is in preparing blanks for subsequent pressing on power presses. This 
purpose is a much easier one to fill than to make a finished tile by auger 
machine alone, as poor surface or bad structure may be overlooked, 
if they do not persist through the subsequent pressing, which they 
generally do not. 

Presses* — The presses used in making roofing tiles may be classi- 
fied as in the following tables: 

Hand Presses /Screw. 

\Toggle. 

(Crank. 
Eccentric. 
Toggle. 



Power Presses 



Trimmings f Crank. 

. \Toggle. 

Special. 



GEOLOGICAL SUBVEY OF OHIO. 251 

The various roofing tile presses used for the making of roofing tiles 
and tile accessories are in considerable number, and it would almost 
seem that each plant was trying to solve the problem of making the best 
tile press for itself. There are in use, at the present time, revolving 
presses made by seven different companies as follows: 

Rogers Machine Tool Company Alfred, New York. 

American Clay Machiner3r Company Bucyrus, Ohio. 

Fisher & Koontz, Machinists Parkersburg, West Virginia. 

East Iron Machine Company Lima, Ohio. 

Crawford & McCrimmon Company Brazil, Indiana. 

Illinois Supply & Construction Co St. Louis, Missouri. 

Ludowici-Celadon Company Chicago, Illinois. 

This latter company does not manufacture presses, but for two of 
their plants they have had presses built for them, from the patterns of 
a German press largely used by the Ludowici's in France and Germany. 

In taking up the study of the revolving power presses as a whole, 
the first thing observed is that they all have one common feature, i e., 
-the revolving pentagon upon which the dies are placed. The chief 
differences in the presses are in the methods of applying the pressure, 
and the shape of the frames of the press. 

There are two modes of application of the pressure, first, by crank 
shaft, cams or eccentrics, and second, by toggle-joint movements. 

The presses using crank shafts can again be divided into two classes, 
first, those in which the entire gearing is attached to the main frame 
work of the machine, and second, those having a solid base, but with 
the gearing separate from the main frame work. 

Crawford-McCrimmon Press. — This company was undoubtedly the 
first to manufacture a revolving pentagon press in this country. Their 
press is of the eccentric type, having the gearing attached to the frame 
of the press. 

As shown by the cut, the press consists of two side frames, con- 
nected at the top by a curved yoke. Carried upon the upper part of 
the frame is a shaft, on which the belt or driving pulley and the fly or 
balance wheel are placed side by side. This shaft carries a small gear 
or pinion wheel on the other end which intermeshes with the large gear 
wheel shown on the right of the press. This latter gear drives the main 
shaft which extends across the press, carrying the two eccentrics which 
are connected by two threaded rods each to the cross head or plunger 
of the machine. The cross head works up and down between guides 
attached to the side frames of the press. To the under side of the plunger 
is attached the upper die. 

The large gear wheel has fastened to it a stud-bolt, which projects 
outward. This stud or "trip" as it is called, is so placed that it engages 
one member of the spider wheel, shown on the right side of the press, 
below the main gear wheel, at each revolution. Immediately back of 
the spider, near the frame work, can be seen a wheel or collar in which 



252 BDLLBTIN ELEVEN 

pockets are cut. These pockets are to receive the plunger or pin, ahown 
above the lock or pocket wheel. The main shaft to which the spider 
wheel is attached carries the part of the press called the pentagon, upon 



Fig. 66— The Crawford & McCrimmon Roofing Tile Press. 



which the lower dies are placed. The operation of the pentagon is 
actuated by the trip pin engaging the spider wheel as the main gear 
revolves. At the instant the trip pin engages, the lock pin or plunger, 
which holds the pentagon firmly while the pressure is being made, is 
released and the pentagon revolves one-fifth of a revolution. The top 
die descends, making the pressure, then raises, and the pentagon is 
tripped, and turned one-fifth of a revolution again, and so on. 

While quite a number of these presses have been made and sold 
by the Crawford & McCrimmon Company from time to time, there was 
only one in use at the time of the visits made to the various plants of 
this country. 

One objection to this press, and the same applies to all presses of 
this type, is that the main driving mechanism is attached directly to 
the press, and too far from the base. In other words, the machine is 



GEOLOGICAL SURVEY OF OHIO. 253 

top heavy. The constant strain and racking of such a press is far greater 
than in the type where the power is applied lower down and separate 
from the frame work. 

The Grath Press* — This press is manufactured by the Illinois Supply 
& Construction Co., at St. Louis, Mo. The main difference in this press 
over that Just described is in the method of applying the pressure to 
the plunger head. 

It will be seen that a crank shaft is used in the place of eccentrics. 
While the crank shaft may be a better mechanical movement than the 
eccentric, the manner in which it is used in this case is a disadvantage 
in as much as the pressure to the plunger is applied at the center. The 
cross head or plunger piust depend entirely upon the guides to hold it 
true, in case there is an excess of clay at one end of the die over that at 
the other. While it is true that all presses must depend on the guides 
to properly center the upper die with the lower one, it is certainly 
better from a mechanical standpoint to apply the pressure equally at 
both sides of the plunger, rather than at one point. 

This press also differs from the Crawford-McCrimmon press in the 
matter of locking or holding the pentagon in place for the pressure. 

This feature as shown in the cut consists of a raised rib or lug cast 
on the main gear wheel. This circular rib engages with the spider wheel 
direct, as shown. At the point where the trip pin is located, a section 
of the rib is cut away, thus allowing an open space to permit the spider 
to turn one-fifth of a revolution. There is an objection to this feature, 
arising from the wearing away of the segmental sections on the spider, 
allowing the pentagon to have more or less play backward and forward. 
With dies using trimmers, such conditions cannot be tolerated at all. 
The pentagon must register exactly with each motion. 

It is plainly seen that the wearing surface of the individual segments 
of the spider is far less than that of the interlocking rim, and will there- 
fore wear away much faster. This could be overcome by making the 
spider much larger, and the holding rim smaller, or by providing re- 
newable wearing surfaces at the critical points. There was found but 
one plant using the Grath press, viz., The Detroit Roofing Tile Company. 

The Ludowici press made in America from German patterns, is 
of the same general type as the two types just described, although not 
built so heavy. This is easy to understand when it is known that the 
Germans are as a rule using plaster dies and must necessarily work their 
clays much softer than they would if metal dies were used. They have, 
therefore, not built presses as heavy as the American firms, who have 
had to build with a strength to accommodate metal dies and stiff clay. 

Presses with Separate Driving Mechanisiiit — This type of press has the 
main drive gearing on the same bed plate as the press proper, but not 
on the same frames, thus relieving the press frame of the overhead load. 



264 BUUJiTIN ELEVEN 

In this general type of press are embodied the best mechanical 
features, and it will without doubt prove to be the press of the future. 
There were eleven of these presses in use in the various plants at the 



Fig. 67 — The Grath Roofing Tile Press. 

time of taking the field notes for this report. The eleven presses in 
use were made by three different firms. Six of them by the Rogers 
Machine Tool Company, three by the American Clay Machinery Com- 
pany, and two by Fisher & Koontz. 

The Rogers Prew,— The Rogers Machine Tool Company has the 
largest number of presses in use at the present time. They well deserve 
this credit, for they were the first to produce a machine of distinctly 
different type from the foreign presses. The following illustration 
shows one of the early pres,ses developed by this firm, a few of which 
are still in existence. 



COaCKUMrCAL SUBVET OF OHIO. 255 

This press has been modified and improved until the most recent 
form put out by this firm has diverged quite widely from the starting 
point. 

It will be observed that this press is constructed upon generous 
lines. The entire press stands upon a solid bed plate, to which are 
attached the two heavy upright frames .carrying the pentagon and 
plunger. To the left of the main frame, and on the same bed plate, are 
the two upright pedestal bearings which carry the primary and sec- 
ondary driving mechanism. A heavy fly wheel is attached to the 
primary shaft, which in turn is controlled by means of a friction clutch 
pulley. The secondary shaft, shown on the top of the pedestals, 
drives the shaft which carries the eccentric to operate the plunger by 
means of a small pinion. 

It will be observed that the cross head or plunger is very large, 
having the two side frames with side and back face plates for guides. 
At the upper right hand corner of the cross head can be seen a gib or 
take-up. This is used to provide for the slight wear that may occur 
on the face of the guides. 

The spider wheel is made very large, thus affording a large bearing 
or leverage siu-face for holding the pentagon steady. 

The trip wheel is shown just above the spider, and behind the large 
upper gear wheel. This trip wheel is provided with a case-hardened 
steel roller and pin, which enters the slots of the spider wheel and turns 
it one-fifth of a revolution at each stroke of the pressure head. The 
capacity of such a press is about 5,000 to 6,000 tiles per day of ten 
hours, and requires about ten horse power to operate it. 

The American Press. — The press of the American Clay Machinery 
Company is of this same type, very little difference having been made in 
its design. The main advantage claimed by its manufacturers, is in the 
manner of making the main housings or frames of the press. In the 
Rogers press they are cast in one solid piece, while the press in question 
has the housings cast in two parts each, depending on the strength of 
two steel rods to each housing to take care of the pressure between 
the head and pentagon. 

Fisher & Koontz Press.— This press is practically the duplicate 
of the one just shown. Hence a description is imnecessary. 

It will be observed from the illustrations of the presses shown, 
that the true American roofing tile presses are equipped with double 
back gearing, while the presses of the German type have single gearing 
only. The double gearing assists the press in the matter of steady, 
uniform speed. The effect of the pressure is scarcely noticeable at 
the driving belt. 

The Klay Press* — The Klay press is manufactured by the East Iron 
Machine Co., Lima, Ohio. It was designed and patented in 1901, by 



BULLETIN ELEVEN 



Mr. A. B. Klay, of Lima. In 1908 only two of these presses had been 
installed, both being in use by the National Roofing Tile Company at 
Lima. 



Fig. 68— Early Form of the Rogers Roofing Tile Press, 



Fig. 69 — The Rogers Machine Tool Company's Roofing Tile Press. 

The Klay press differs very widely from all other makes in the 
matter of applying the pressure to the plunger head by toggle joints 
instead of the crank or eccentric. 



GEOLOGICAL SURVEY OF OHIO. 257 

It will be seen from the cut that the press stands upon a cast bed 
plate, upon which are erected the two tall housings on the right and the 
pedestal bearing on the left. 

It will be observed that the machine is belt-driven. The main 
driving shaft carried a pinion which engages the gear wheel shown to the 
left side. This gear in turn is attached to a shaft carrying two pinions 
which work against two large gear wheels shown below. These large 
gear wheels are made with cams which in turn operate the plunger 
shown just above the cam gear wheels. The plunger, it will be seen, is 
attached to, and operates the toggle joint just above it. This toggle 
in turn is connected to the main toggles which operate the plunger 
head. Thus with all of the compound movements, an enormous pres- 
sure is exerted at the pentagon. The pentagon is operated by a small 
sprocket or trip wheel which meshes with a segmented one on the cam 
shaft. 

It will be noticed that there is a double set of toggles at the plunger. 
The inner or large ones operate the plunger, and give the pressure, while 
the smaller or outside ones operate the frame around the upper die, 
called a trimmer. These latter toggles are made a little longer than 
the main ones, so that as the plunger descends, the trimmer moves 
down a little faster and farther than the plunger-head. By so doing, 
it reaches and encloses the lower die before the pressure is applied. 
Thus the clay is held securely in by the trimmer so that when the pres- 
sure is released the tile is left with perfectly smooth edges, requiring 
no trimming. The dies on this press are made of ''white metal,'' and heat 
must be supplied to make the clay release. This is supplied at the upper 
die only, steam being used. The hose pipe shown in the cut, which 
enters between the toggles, conveys the steam into the hollow backing 
of the upper die. A small pipe can be seen extending across the front 
of the upper die on the pentagon. At the bottom is another, and one 
in the back is placed so that it is in proper line for the upper die. These 
small pipes are for spraying oil upon the dies by means of compressed 
air. This pipe system is so connected with a trip that it automatically 
sprays the oil at the proper time when the plunger is up, thus doing 
away with the bothersome and expensive hand method of applying 
the oil. 

While this press has had but little opportunity to demonstrate 
its working qualities, outside of this one plant, it was claimed by those 
using it, that it had given very good satisfaction there. The press, 
however, is very much more expensive than the other types of presses 
built in this country. The ordinary presses cost from $800.00 to 
$1,500.00, while the Klay press runs very much higher. 



17— G. B. 11. 



BULLETIN ELEVEN 



Pig. 70 — The American Clay Machioery Company's Roofing Tile Press. 



Fig. 71 — The Klay Roofing Tile Press. (National Works. Lima, O.) 



GEOLOGICAL SURVEY OF OHIO. 269 

SPECIAL OR TRIMiynNGS PRESSES. 

These presses differ from the pentagon presses in that they are 
usually made to carry one die only. Their use is for the special pieces 
that must be used with the regular tiles to make a roof complete. They 
produce such shapes as eave tiles, top or ridge tiles, hip rolls, crest- 
ings,etc. 

The press used for this purpose differs quite widely in the method 
of applying the power. Five machine firmswere represented by presses 
manufactured in this country, while a press manufactured in Germany 
has found use with one American company. 

The American firms were as follows: 

The C. W. Raymond Company Dayton, Ohio. 

Illinois Supply & Construction Co St. Louis, Missouri. 

Rogers Machine Tool Company Alfred, New York. 

American Clay Machinery Company Bucyrus, Ohio. 

East Iron Machine Company Lima, Ohio. 

With the exception of the Raymond press, these presses are all 
power driven. In the selection of a trimmings press, much care should 
be used, output and ease of operation being the primary objects of 
attention. 

In the foreign countries, screw trimmings presses have been very 
widely used in the roofing tile industry, but in our own country the 
screw press has found but little or no use in this industry. There are 
hundreds of screw presses in use in the dry press tile factories, making 
wall and floor tiles, but for plastic clay they are not popular. The 
American manufacturer wants a press that can be operated more quickly 
than a screw press. 

The Raymond Hand Press* — This hand press has found the great- 
est use in this country of any hand-power press. It is known as the 
"Perfection Hand Press." It is made in three sizes, the No. 3 size 
being the one most in use. (See Figure No. 120.) 

It will be seen that the press is of the toggle joint type, the pres- 
sure being exerted by bringing the toggles to a vertical position, which 
is accomplished by pulling the hand lever down. This press when 
properly arranged, has a sliding track arrangement, whereby the tile 
dies are moved back and forth to receive the pressure, and then to dump 
the tile onto a pallet. 

For varying thicknesses or sizes of dies, provision is made to move 
the upper head up or down by means of screw and hand wheel. This 
adjustment can be made very quickly. The pressure exerted by the 
mechanism of this press is sufficient to make dry press brick, hence for 
plastic clay ware it is ample at all times. 



260 BULLETIN ELEVEN 

Its daily output depends largely upon the operator and the size 
of tiles made, but under average conditions it is possible to make 500 
pieces, but more often the output will not exceed 300 pieces per day. 



Supply & Construction 

While this press has found quite a wide use among the roofing 
tile manufacturers, it has one feature that is not desirable. By refer- 
ence to the cut it will be seen that the pressure is applied from below, 
raising the lower die up against the top die, which in turn remains sta- 
tionary. This, however, should not be the case. The top die should 
be the one to move and the lower one remain stationary, for the fol- 
lowing reasons: In the nature of the case, tile die-s are heavy, and in 
addition to the dies, the weight of the track or dumping mechanism 
rests on the die platform, so that the man at the lever has a dead load, 
amounting at times to 200 pounds, to raise at the pressing of each tile. 
In part, this load is relieved by the side springs shown in the cut, but 
the tile manufacturer has ao many dies to be used on a press of this 
kind that it is not usually pos.sible to keep the springs properly adjusted 
to equalize the weight of each one. 

The above objection to the press is possibly no more serious than 
having the sliding track moving up and down with each pressing. For 
various reasons it is desirable to have the track remain at one level, 
especially if the press is fed from both sides. Another obje(;fion to this 
press which will apply to all hand presses is that it requires two men to 
operate it properly, one at the die and the other on the lever. The same 
work can as well be d(me by one man if the press is fitted for power. 

The Grath Trimmings Press. — Of the power prcs.ses for special work, 
this press has found a considerable use and well deserves its popularity. 
It is small and compact, requiring but very little floor space, and is 
easily operated by one man. 



GEOLOGICAL SURVEY OF OHIO. 261 

By referring to the illustration it will be seen that the press consists 
of two cast side frames, or housings, which practically enclose all of the 
working parts of the press. On the opposite side, back of the die in 
the cut, is the driving pulley. This is on a shaft, which in turn carries 
two pinion wheels, w^hich drive the tw^o large master gears shown at the 
back of the press. These carry a cam, which in turn operates a connect- 
ing rod that is attached at its outer end to the toggle joints shown below 
the die. When these toggles are pulled to a veritcal position they trans- 
mit pressure to the upper die by means of the four large rods working 
in gmdes at either side of the press. The lower die is arranged to slide 
in and out upon a rod to which it is hinged. It is a very easy matter to 
dump the largest dies by turning them over with the handle shown at 
the end of the die in the cut. For the proper adjustment of the upper 
die to suit the varying thicknesses, it is necessary to raise or lower the 
nuts on the four upright rods. If this feature were improved, the value 
of the press would be very much enhanced. In addition, the press should 
be built with a higher lift, it being now impossible to make ware of much 
depth. The weight is all below, and the lower die does not move up 
and down with the pressure, as in the Raymond press, both of which 
features are desirable. 

American Trimmings Press* — It will be seen (Figure 73) that this 
press is built upon very different lines from those of the Grath press. 

It consists of a main central frame, or housing, a part of which 
forms the journal bearings for the driving and crank shaft. .Two up- 
right guide rods carry the cross head to which the upper die is attached. 
It will be noticed that relieving springs ai^ employed to allow a slight 
give to the cross head in case of excessive pressure. 

The four connecting rods connect the crank pins, riveted into the 
crank gears at either side of tHe press. The crank gears are provided 
with counterweights to balance the upper cross head. The power is 
applied at the friction clutch pulley, which in turn drives a shaft carrying 
two pinions that engage the large crank gears. Suitable sliding track 
arrangements are made for the lower die. Considering this press as a 
whole, it should meet the demands of the roofing tile manufacturer and 
prove very satisfactory. Only one of these presses was found in use, but 
this design had not been on the market long at the time of taking the 
field notes for this report. 

The Rogers Trimmings Press* — This press is built along quite dif- 
ferent lines from those of the American or Grath. It is, in a general way, 
patterned after the Rogers pentagon press, in that the main housings 
and outbearings stand upon a heavy one-piece bed plate, thus making 
a much heavier, and at the same time a more rigid, press than those 
having outbearings resting on separate pillow blocks or foundations. 



262 BUIJJETIN ELEVEN 

From the drawing on page 264 it can be Been that the press consists 
essentially of the solid bed plate, with the two outbearings on the 
right, while at the left are the two main housings. These are con- 
nected at the top by a heavy cast iron yoke. 



Fig. 73 — Trimmings Press, made by the American Clay Machinery Company, 

The driving mechanism of the press is of the double back-geared 
type. The main driving pulley is carried by the shaft resting in the 
bearings at the top of the outbearing blocks. This primary shaft, in 
addition, carries the pinion wheel at the extreme right, which meshes 
with the large gear wheel on the secondary shaft. The secondary shaft 
extends across the face of the main housings, being attached to the same 
by bearings. The power is delivered from the secondary shaft through 
the two small pinions to the large crank gear wheels, one on either side 
of the press and connected by a shaft. From the crank wheels the power 
is delivered to the main cross-head by heavy rods, two at either side of 
the press. 

The cross-head is made very large and heavy, and travels or recip- 
rocates in guides formed by the side housings. Attached to the cross- 
head is a large face plate, to which the dies can be bolted. A convenient 
arrangement is provided to raise and lower this plate so that it can be 
adjusted to suit different dies and to regulate the thickness of the ware. 



GEOLOGICAL SURVEY OF OHIO. 263 

The main table upon which the lower die is carried rests on a heavy 
casting or bed plate which extends from housing to housing. The die 
table is conveniently arranged to move out from under the press to 
facilitate the filling and dumping. The press is built so that either a 
single or a double dumping table can be used. 

Experience in the past has been that it is more satisfactory to op- 
erate any trimmings press from one side only. The better practice where 
greater output is desired is to use two presses. 

The Rogers press has found a wider use than any of the other 
trimmings presses described in this report. It has, however, been on 
the market longer than most of the others, but in turn it has a number 
of excellent features. It is self-contained, double back-geared, the main 
housings are heavy and large, thus forming exceptionally good bearing 
surfaces for the guides. The adjustments of the upper die can be quickly 
made, and furthermore the lift of the upper die is ample to care for 
ware of high projections. 

Mueller Hand Press» — This press is quite small and is arranged for 
hand driving. It is operated by taking a previously prepared blank 
of clay and placing the same on the lower die, which is between the 
hand crank and the large gear wheel. The upper die is then pulled down 
into position. The roller pins at each end of the die engage with the . 
cam or eccentric wheels attached to the main gear wheel shaft. The 
crank, which is back-geared against the main gear wheel, is then turned 
until the cams have made one complete revolution. The roller pins 
of the upper die thus being released, the die is raised. A pallet is now 
placed over the tile resting in the lower die. This die is so hinged that 
it can easily be turned over, thus emptying the freshly made tile onto 
the pallet. The die is then turned back into its proper position ready 
for a second tile. 

There is little that can be said in favor of this press, although by ar- 
ranging to drive it by power so that its speed would be increased it is 
quite possible that it could be used on special or complicated tiles and 
trimmings. As it stands though, it is quite foreign to the American 
way of doing work. While a number of these presses have been placed 
in drain tile and brick plants for the manufacture of a few roofing tiles, 
none of them have found their way into any of the true roofing tile 
plants. 

Laeis Trimmings Press* — It will be observed that this press is dif- 
ferent from the American presses. Its essential parts are as follows: 
The driving pulley at the right is carried on a shaft supported by an 
outbearing and a boxing attached to the main housing or frame of 
the press. This primary shaft is back geared against the large gear 
wheel shown on the upper right hand side of the press. The shaft 
to which the large gear is attached extends through to the 
other side of the press, carrying at the center an eccentric hub which 



BULLETIN ELEVEN 




Fig. 74 — The Rogers Trimmings Press. 



Fig. 75— The Mueller Hand Press. 



GEOLOGICAL SURVEY OF OHIO. 265 

works against a roller attached to the cross head or plunger. Thus as 
the eccentric hub on the shaft revolves, the plunger is alternately raised 
and lowered carrying the upper die with it. The lower die which rests 
on the bed plate is provided with a sliding track to enable the operator 
to change and empty it easily. Probably the strongest feature about 
this press is the placing of the greater part of the gearing above the dies, 
thus keeping them free from the scrap clay. 

Jaeger Trimmings Press* — This press is of the same type as the im- 
ported German trimmings press used at the Chicago Heights plant of 
the Ludowici-Celadon Company. 

From figure 77, page 268, it can be seen that the press is built low, 
heavy and self-contained. The power is transmitted from the driving 
pulley to the plunger through a long lever or walking beam. While 
the latter is continuously in motion, the pressure only takes place when 
the small lever above the upper die is pushed into position by the 
operator. After each stroke, however, the lever is automatically dis- 
engaged as a safety precaution. 

It will be observed that this press is so constructed that the dies 
operate at right angles to the body of the press, and furthermore, the 
dies are accessible at any point on the sliding track. This feature is 
of value in case the piece of ware should fail to fill out perfectly and it 
is necessary to add more clay and press a second time. In the ordi- 
nary press the lower die will have to be pulled out from under the plunger 
in order to add the extra clay. 

In this case as in the press shown m figure seventy-six, the gearing 
is removed as far as possible from a point where it would be in danger of 
becoming fouled with the scrap clay. 

The Klay Trimmings Press* — By reference to the cut (Figure 78) it 
will be seen that this press is entirely different from any others thus far 
described. 

It consists of four upright frame posts, connected at the top by a 
heavy casting, which carries the upper die and the mechanism for ad- 
justing the position of the same to suit dies of various sizes. The 
lower die rests upon a movable table, or plunger, working between 
guides. Just below and connected to the table, are the toggle joints 
which transmit the pressure to the die. 

The toggles are operated by a long connecting rod which is operated 
by the cam gears shown on the left of the cut. These cam gears and 
all the balance of the driving mechanism are attached to an extension 
of the main frame work. 

While the press is undoubtedly very powerful, it has some bad 
features. Among them are, first, the lower die is moved instead of the 
upper; secondly, the press is very bunglesome, requiring an undue 
amount of floor space to accommodate the driving mechanism. More 
space is taken up by this part alone than is used by the press proper. 



266 BULLETIN ELEVEN 

One press of this make was found in use during the season of 1908. 

Tile Trimmer. — Mention was made of a trimmer in connection 
with the deseripion of the Klay roofing tile press, used to make the 
sides or edges of the tile smooth and perfect without subsequent work. 



Fig. 76— The Laeis Trimmin 

With the ordinary dies used on tile presses, it is customary to 
have the edges of the upper and lower dies meet at a point about midway 
in the thickness of the tile; that is, the tile is half in the upper, and half 
in the lower die. It is impossible to keep dies in such perfect condition 
that they will shut absolutely tight along their sides for any length of 
time. The issue of the clay soon wears the sharp edges away. Thus, 
after a tile has been pressed in such a die, it will be found upon being 
removed to have a ragged seam or "feather edge" on the line where 
the two dies divided. This feather edge of clay must be trimmed off, 
and as a rule two boys or men are required at each press to do this work. 
With plaster dies, the trouble is much worse than with metal dies. To 
do away with the expense of "skinning" the tiles, as it is called, large 



GEOLOGICAL SURVEY OP OHIO. 



Fig. 77-^The Jaeger Trimmings Press. 



Fig. 78 — The Klay Trimmings Press. (National Works, Lin 



268 BULLETIN ELEVEN 

sums of money have been expended to perfect a trimmer that would 
do the work automatically on the press. The great trouble has been 
to prevent the clay from squeezing out between the trimmer and die; 
in this case the feather edge is only changed in position. A trimmer, 
to do good work, has to be made to fit the die snugly, and if so, at times 
it will bind, failing to pass over or release from the die, and it or the 
press is then broken. 

So far the only successful trimmers that have been made to work 
are those used on metal dies. 

The trimmer giving the best satisfaction was in use at the plant 
of the United States Roofing Tile Company, at Parkersburg, W. Va., 
and was devised and worked out by them. In outline the trimmer 
ia about as shown in the following drawing: 



{W- 




Fig. 79 — Tile Trimmer, in Use at the United States Roofing Tile Company. 



The trimmer consists of two parts, the frames A and the track 
D. A represents a top view of the trimmer. It is nothing more than 
a steel frame made to encase the die. At the two ends of the frame 
are shown rollers, C. The side view B of the frame shows the position 
of the rollers in reference to the frame; they are attached by lugs pro- 
jecting downward. 

D represents the track, in which the rollers of the frame work. 
At E is shown an end view of the press pentagon with the five dies and 
trimmers attached. The track as indicated by the dotted line is placed 
out of center with the pentagon, being highest at the upper and feeding 



GEOLOGICAL SURVEY OP OHIO. 269 

side of the press. The track of course is attached to the side frames 
of the press, and does not move. 

The operation of the trimmer is as follows: The blank of clay 
used to make the tile is fed into the die at F. The trimmer at this point 
is nearly at its full height. The pentagon revolves to G, and the trimmer 
is at its highest point. The top die comes down, entering the trimmer- 
frame by a very tight fit and the pressure is made. The top die then 
lifts and the pentagon turns. When the die has reached H, it will be 
seen that the trimmer is drawn back to the full depth of the die, thus 
releasing the tile w-hich is caught on the pallet. The fact that the 
trimmer has held the edges of the clay in while under pressure, and 
while moving downward it has smoothed the sides, makes it possible 
to produce tiles that do not need trimming. 

Much could be done along this line that would be of great benefit 
to the industry. 

PATENTS ON ROOFING TILE MACHINERY. 

The records of the Patent Office show that great quantities of 
machines have been devised and patented. Few have become of more 
than temporary importance. For the convenience of others who are 
looking up this subject, the following list has been prepared, of the 
patents taken out on roofing tile machines. 



270 



BULLETIN ELEVEN 



Date of 



Nanttof IxLvcnisK, 



Serial 



L I 



Remarks. 



June 12 
1855 



Dec. 29 
1868 



April 13 
1869 



Aug. 2 
1870 



Aug. 23 
1870 



Jan. 10 
1871 



June 27 
1871 

Aug. 27 
1872 



Sept. 9 
1873 



Mar. 13 
1877 



G. Graessle , 

Address not given. 



P. A. Brown 

Indianapolis, Ind. 



Charles Messenger 
Cleveland, Ohio. 



John B. Hughes. . . . 
Terre Haute, Ind. 



Joseph Christen . . 
New Orleans, La. 



John Koehler . . 
Warren, Ohio. 



John B. Hughes . . . . 
Terre Haute,- Ind. 

Calvin J. Merril . . . . 
Upper Alton, 111. 



13,059 



85,362 



88,795 



106,062 



106,550 



110,859 



116,447 



130,856 



Calvin J. Merril . . . 
Upper Alton, 111. 



Jacob Greenawalt 
Pittsburgh, Pa. 



142,576 



188,291 



Dies attached to endless 
chains, and made to pass 
between rollers for the nec- 
cessary pressure. 

Die boxes or frames in which 
the tiles are formed. Pres- 
sure applied by levers. 

Design of a pentagon press to 
be operated by hand; pres- 
sure being aelivered 
through levers. Probably 
the first design of a penta- 
gon press in the United 
States. 

A table and frame in combi- 
nation with die boxes upon 
which tin and muslin were 
used to prevent the clay 
from sticking. Presstire ap- 
plied by levers. 

Design for a pentagon press; a 
better design than that of 
No. 88,795. 

A roller having the die or one 
face of the tile impression 
attached. The other half of 
die with its clay charge was 
pushed under the roller, 
thus receiving the imprint. 
A very poor machine for 
the work. 

Similar to No. 110,859, 
though more practical. 

Dies for diamond tiles at- 
tached to segments of roll- 
ers, which in turn are re- 
volved through a short arc 
bringing the dies together. 

Dies attached to large rollers 
or wheels which press the 
dies together as they re- 
volve. 

Design of a press having a 
three-sided die holder in- 
stead of the usual pentagon. 
Tiles to be delivered onto a 
belt beneath the press. De- 
sign is of doubtful value. 



GEOLOGICAL SUEVEY OF OHIO. 



271 



Date of 
Issue. 


Name of Inventor. 


Serial 
Number. 


Remarks. 


Dec. 4 


Horace B. Camp 


197,718 


Design of a press having a 


1877 


Cuyahoga Palls, 0. 




horizontal revolving table 
to carry the dies under a 
plunger for the pressure. 
For some classes of roofing 
tile work this press would 




















be of value. 


Dec. 23 


Carl Schlickeysen 


309,568 


An after cutter and former for 


1884 


Berlin, Germany. 




a u g e r-m a d e interlocking 
tiles. 


April 5 


John E. Donaldson . , . 


472,189 


Design for a metal tile die. 


1892 


Montezuma, Ind. 






Dec. 13 


George H. Babcock .... 


488.049 


Design of a press upon which 


1892 


Plainfield, N. J 




the dies are brought to- 
gether as a pair of jaws. 
This press was for several 




















years in use at Alfred,N.Y. 


Mar. 14 


Wilhelm Ludowici 


493,366 


Design for a pentagon press. 


1893 


Jockgfrim, Germany. 




The pressure is applied by 
power through eccentric- 
shafts. This design shows 
the *spider and trip wheel 
for dumping the dies. 


Jan. 23 
1894 


Toseph RapD 


513,140 


Design of a machine or cutter 
for cutting auger-made 


New Phuadelphia, 0. 








Spanish tiles. 


April 14 


Karl Thomann 


558,326 


A hand press better adapted 
to cement tiles than those 


1896 


Halle, Germany. 










of clay. 


Dec. 22 


Gustav Krebs 


573,604 


A complicated hand press; 
would be better for cement 


1896 


Halle-on-the-Salle. 




Abraham Weil, 




than clay. 




Steinheim, Germany. 






June 15 


Franz Kunzemann .... 


584,374 


Design of a pressing table for 


1897 


Eilenburg, Germany. 




molding tiles in dies by 
hand m connection with 














tamping and scraping 
arms. Would probably be 
of more service for cement 
than clay tiles. 

• 


Jan. 18 


Abraham Weil 


597,447 


Hand press for forming tiles. 


1898 


Steinheim, Germany. 




very complicated. 


July 26 


John C. Merrill 


607,870 


• 

A press having a horizontal die 


1898 


Alfred, N. Y. 




table which carries the dies 


■ 






under the plunger. Was 
originally designed for the 
manufacture ot dry pressed 














tiles. 



272 



BULLETIN ELEVEN 



Date of 
Issue. 



Name of Inventor. 



Serial 
Number. 



Remarks. 



Dec. 6 
1898 



Mar. 7 
1899 

April 10 
1900 

Oct. 2 
1900 



Mar. 12 
1901 



Nov. 26 
1901 



Aug. 12 
1902 



Mar. 22 
1904 



May 31 
1904 

Nov. 7 
1905 

Nov. 14 
1905 

Nov. 21 
1905 



Nov. 13 
1906 



July 30 
1907 

Oct. 13 
1908 



A. B. Klay, G. Jennings 

and F. Ewing 

West Cairo, Ohio. 

Carl H. D. Wicke 

Lehe, Germany. 

Abraham Weil 

Steinheim, Germany. 

Richard Lesch 1 

Bruno Polte j 

Konstadt, Germany. 

Wilhelm Ludowici 

Jockgrim, Germany. 

Abraham B. Klay . . . . 
Ottawa, Ohio. 



Xavier P. Gilardoni . . . 
Choisy- Le- Roi, France 

Louis Strenli 

Zurich, Germany. 



John W. Campbell . . . 
Colorado Springs,Col. 



William P. Meeker 
Newark, N. J. 



Henry Meyer 

Warren, Ohio. 

Alfred Gaspary 

Markranstadt near 
Leipsic, Germany. 



Alfred Gaspary 

Markranstadt near 
Leipsic. Germany. 



Samuel A. Jones 
Deshler. Ohio. 



William Pugh. 
Streator, 111. 



615,560 
620,817 
647,431 
658,791 



669,535 



687,688 



706,926 

755,253 

761,201 
803.700 
804,753 
804,944 

835,858 



900,778 



Toggle joint press, for descrip- 
tion, see Fig. No. 71, page 258 

Hand press for forming 
cement tiles. 

A drop or hand tamping press 
for cement tiles. 

A ' machine consisting of a 
roller die under which pass 
the opposite dies moved by 
endless chains. 

Improvement on trip and 
escapement wheel of penta- 
gon presses. 

Toggle joint press illustrated 
and described in Fig. No. 
71. An improvement over 
patent No. 615,560. 

Design of a pentagon press 
for making hollow inter- 
locking tiles. 

Design of a revolving hori- 
zontal table press for 
cement tiles. 

A screw press and die for 
making cement tiles. 

Mold or casing for making 
tiles by hand. 

Dies or forms for making 
cement tiles. 

Outfit for making cement 
tiles. 



An improvement on patent 
804,944. 



Hand press with die forms for 
making cement tiles. 

A die frame or box over which 
a roller is passed to press 
the material, cement or 
clay, into the proper form. 



GEOLOGICAL SURVEY OF OHIO. 273 

NOTES ON THE MANUFACTURING OPERATION. 

The foregoing descriptions have set forth more or less superfi- 
cially the types of machinery used in the preparing of blanks for roofing 
tiles and for actually making the tiles and finishing them. In apply- 
ing the machinery to the different shapes of tiles, a great variety of 
practice was found, of which it is the intent to give a resume. 

The Forming of Shingle Tiles* — The use of shingle tiles has made 
its greatest development in Germany, and naturally its greatest de- 
velopment in its method of manufacture has there occurred. 

As shown in Chapter II, there are many forms of shingle tiles. 
The plainest and simplest are merely the flat slabs of burnt clay, usually 
three-eighths of an inch or one-half inch in thickness, by five or six 
inches in width, and twelve to fifteen inches in length. They may 
be made with ribs, lugs, interlocking features, ornamented and grooved 
surfaces, etc. The more complicated they are made, the less distinction 
remains between them and the regular interlocking tiles. 

Plain Tiles vs. Lugged Tiles. — Plain shingle tiles may be fastened 
to the roof by two nails, driven through perforations made when the 
tiles are soft, or by hanging the tiles by lugs on their under surface, which 
hook over the edges of the roof purlins. The former method is in use 
almost exclusively in America, while the lugs are the usual method in 
European countries. 

There are several points in favor of each method. Taking up the 
lug method first, the following points may be made: 

First. Nails are dispensed wuth. It is claimed that nails will 
in the course of a few years rust off, allowing the tiles to slide down off 
the roof. 

Second. It is difficult to insert new tiles on roofs that are nailed 

on. It is impossible to raise the tiles that are in place sufficiently to 

allow putting in new ones. With lugged tiles, it is only necessary to 

push the new tiles up under the old ones, until the lug catches over the 

purlin. 

Third. Tiles with lugs are less apt to break when on the roof than 
nailed ones. In nailing tiles it frequently h^^ppens that the roofer drives 
the nails down too tight on the tiles. This lifts the outer ends, and puts 
the tiles under a strain, so that it takes only a slight jar or a load applied 
to the outer end of the tiles to break them. In the case of the lug tiles, 
each *one hangs loose and free, thereby allowing for expansion and 
contraction and for irregular loading, as in walking on the roof while 
under erection or in the process of cleaning, removing snow, etc. • 

In favor of nailing shingle tiles in place the following reasons may 
be brought out: 

First. For siding purposes the nailed tiles have the advantage; in 
fact, lugged tiles cannot be used for this purpose unless other provision 
than the lug is made to hold them in place. 

18— G. B. 11. 



274 BULLETIN ELEVEN 

Second. In manufacture the lugged tiles are somewhat more compli- 
cated than the nailed tile. In the lugged tiles it is necessary to provide 
special cutters to remove that part of the rib of clay along the back of 
the tiles that is not needed for the lug. The Germans, in particular, have 
in use many excellent cutters for this class of work. 



<» 



They not only have cutters that will take care of a single bar of 
clay, but cutters that will handle two bars of clay with two tiles to 
each bar. 




Third. Tiles with lugs require more clay than nailed tiles. In a 
plant producing twelve thousand shingle tiles per day, from five hun- 
dred to eight hundred pounds more pjay will be used making tiles with 
lugs than would be required in making the straight bar. This extra 
material takes up a proportionately increased amount of heat in drying 



GEOLOGICAL SURVEY OF OHIO. 275 

and burning. This item is not of serious weight, but its effect is adverse 
to the lugged tile. 

Fourth, Tiles with lugs are more troublesome to handle in the set- 
ting of the kiln and at other points, on account of the fact that every 
other tile must be reversed in order to allow them to nest tightly. 

It can be seen from the above that each shape has its shortcomings. 
The American tile manufacturer seems to be very much in favor of the 
plain shingle tiles with nail holes. Not a single instance of the manufac- 
ture of shingle tiles with lugs was to be found in this country in 1908. 
It would seem, though, that the manufacture of lugged shingle tiles, 
could be profitably taken up by our factories. This style of tiles would 
unquestionably meet the approval of the architects, and at the same 
time would be gladly accepted by the roofers as soon as they found 
that a roof could be covered in much less time. Of course the roof 
would have to be stripped with purlins, but these would not require 
one-tenth of the amount of nailing that a complete covering of tiles 
would require. 

As to the cost of manufacture, it is believed that lugged tiles can 
be made as cheaply as the ordinary hand-punched kind if cutters of 
proper design are employed. 

Popularity in United States. — In the United States, the manufacture 
of shingle tiles is not very extensive. There were only two plants work- 
ing exclusively on this style of tiles in 1908. Nearly all of the other 
roofing tiles plants also make shingle tiles, but they are only an unimpor- 
tant side line in most of them. Hence at the above two plants, 
where the entire output is of shingle tiles, it is natural to expect to find 
their manufacture developed to a much better degree than in those 
plants where only a few are made. 

The manufacture of shingle tiles has given more trouble to the roofing 
tile manufacturers than all other styles combined. At first thought it 
would seem that the simplicity of shape and the small size of the tiles 
would decrease the difficulties of manufacture, but the reverse has proved 
true. It is doubtful whether there is in the entire clay industry any 
ware more difficult to produce with good degree of mechanical perfec- 
tion at the proper degree of vitrification than a plain, simple shingle 
tile. The fact that it is plain is what makes it a hard problem. To keep 
it perfectly straight and true during the drying and burning is the 
trouble. It will be found that tiles with reversed curves, like the Spanish 
or interlocking forms, are much easier to hold straight, owing to the 
curves acting as braces on the ribs to prevent warping. In the plain 
shingle tiles there is nothing to prevent their warping like a green board 
exposed to the sun. 

Then, too, the shingle tiles are very prone to a trouble known as **side 
checkinj^" These are cracks proceeding in from the edges of the tile 



276 BULLETIN ELEVEN 

about one or two inches. Also, the shingle tiles are the most apt of all 
kinds to "centermark" during the burning. 

The side checks are due very largely to faulty die construction; 
that is, the clay along the sides of the tile does not receive the same pres- 
sure, while passing through the die, that the central portion of the tile 
does; hence the two portions are of different density, and will shrink at 
a different rate, producing cracks. Even if no difference in density can 
be found, the difference in pressure results in a difference in speed of 
flow. The bar of clay is like a stream w^hose current is swiftest in the 
center and slow^er along the banks, where it is retarded by friction. 
If the center of the clay bar flows even one-eighth of an inch faster 
in twelve inches than the sides, this difference is likely to result in 
cracks aggregating one-eighth of an inch in width. But the crack also 
leads to the bar tearing and ruffling up so that no smoothing down by 
hand or otherwise will eradicate the defects thus initiated. 

Methods of setting and burning also play a large part in side-checking 
shingle tiles. As a rule, in the endeavor to set them so they cannot warp 
or twist they are set too tight for the heat to penetrate them rapidly, 
and are then burned altogether too fast. This means that a compact 
mass of tiles will act about as a solid block of clay would do. The ex- 
terior of the pile, receiving the heat first and longest, will shrink and 
vitrify more than the central parts, resulting in side checks. This point, 
however, will be treated more fully under the heading of methods of 
setting tiles. 




Fig. 82— Hand Mold for Shingle Tiles. 

Early Modes of Manufacture* — In the beginning, shingle tiles were 
no doubt roughly formed by the hands upon a flat area of bare ground, 
or upon flat stones. Following this, it would only be natural for man to 
carve out of wood molds or possibly molds of burnt clay, into which he 
could press the soft clay, and at this state of development, the industry 
must have stood for many centuries. With the discovery and use of 
cast iron, the use of this metal fpr dies naturally entered the field, and 
still remains an important, but not exclusive, material. 

Hand Pressing in Marginal Ring, — In figure 82 will be seen an outfit 
still in use in many of the smaller plants in Europe. It consists of two 
parts, first, a piece of plank, over which is spread a piece of canvas 
or other cloth. This cloth as shown, is tacked along one edge of the 
block, and is spread upon the surface, covering it completely. It is 



GEOLOGICAL SURVEY OF OHIO. 277 

is held smooth and taut by' an iron rod B, which is sewed into the 
margin of the cloth, like a curtain pole. The second part of the outfit 
is the iron frame C. This frame is made with the inside shape and 
dimensions of the desired tile in the green condition. This frame is 
placed on the canvas surface of the block, and the previously prepared 
clay is batted into the iron frame by the hand or by a wooden paddle 
or "batter," until all parts of the frame are filled. A straight edge or 
stick or metal scraper is then drawn over the top surface of the clay, 
cutting it down to the level of the sides of the frame, which thus con- 
trols the thickness of the tile produced. A board or pallet of about the 
same outline as the tile, is now held upon the surface of the clay, which 
is usually well smeared with a fine red-burning sand. The iron mar- 
ginal frame is now raised until free from the tile and the tile is **de- 
livercd" on the pallet by placing the right hand on the pallet and 
raising the free edge of the canvas and thus upsetting the slab of clay. 
The bottom side is then sanded and the , pallet carried out to the yard 
to dry in the sun and wind. 

Hand Pressing in Plaster Diest — Another method for making 
shingle tiles by hand employs moulds made of plaster of Paris. 

These moulds are made in one piece, so that after pressing and 
pounding or "batting*' the clay into the mould, and scraping off the 
excess, much as in the case of the preceding method, the clay must 
remaiit in the mould for possibly an hour to allow the moisture to be 
absorbed by the plaster mould and the clay to shrink loose from it. 

« 

Each workman must, therefore, be provided with enough moulds to 
keep him busy for an hour or more, i. e., enough to enable him to 
work continuously. 

The above methods are of course very crude, and would prove 
impracticable in this country with our expensive labor, unless it might 
be on some special order, where genuine hand-made tiles are desired 
and the price paid is sufficient to warrant making them after this old- 
fashioned manner. Such cases do arise, and with increasing frequency, 
as architects give more attention to the reproduction of old types of 
buildings. 

Shingle Tiles by Hand Power Presses* — While it is possible to 
make shingle tiles on hand presses as perfectly as on any other, very 
few if any are made in that manner in this country. In foreign coun- 
tries, where labor is cheaper, some forms of shingle tiles are still made 
on the hand-power press, but in the nature of the case, since the shingle 
tile is the easiest form to make by expression through flow dies, very 
little work is now done by hand-power presses except for odd pieces, 
such as miter tiles, valley tiles, gable, and sometimes tower tiles. 

Shingle Tiles Manufactured by Flow Dies* — It can safely be said, 
that at least ninety per cent, of all shingle tiles are now made by this 



278 



BULLETIN ELEVEN 



method. The general simplicity of outline of this variety of tiles would 
indicate its adaption to this method of manufacture. Shingle tiles, 
as made in this country, are cut from a ribbon or thin flat bar of clay, 
usually three-eighths to one-half inch thick by five to six inches wide, 
in lengths of twelve to fifteen inches. The types of machinery used 
have been discussed earlier in this chapter. 

Sidnglc Tiles by Plungfcr Machines* — The sole plant using this 
method of manufacture in 1908, the Cincinnati Roofing Tile and Terra 
Cotta Company, of Winton Place, Cincinnati, Ohio, has been described 
with care in connection with the plunger machine and will not receive 
further consideration here. 




Fig. 83— Plaster Mold for Shingle Tile. 

Shins:Ie Tiles by Auger Madiines» — As the only two plants occupied 
solely in shingle tile manufacture are both using the auger machine, 
it follows that the larger part of the shingles in this country are pro- 
duced by this method. These plants are the Huntington (W. Va.) 
Roofing Tile Company, the oldest, and the Murray Roofing Tile Com- 
pany, of Cloverport, Ky. 

The dies through which the tile bar is extruded, constitute really 
the only critical or characteristic feature of an auger machine for roofing 
tile purposes: 

Shingle Tile Dies. — Much attention has been given to the matter 
of shingle tile dies by the various roofing tile manufacturers, each in 
turn having devised a die that in their estimation is the acme of success. 
They usually guard the details of their die with much secrecy. It 
is questionable, however, whether this policy is a profitable one. 

Without doubt, each die in successful operation has its points of 
excellence, and represents an asset to the company using it, but to 
any other concern, with clay of different physical properties, it is 
quite unlikely that it would prove satisfactory. . Hence, by an open 
discussion and comparison of notes on this point, much valuable infor- 
mation could be given and received, and each concern would be estab- 
lished more safely with a knowledge of the principles rather than of 
unassorted facts. 



OEOLOQICAL SURVEY OP OHIO. 



279 



The Qncinnati Shingle Tile Die,— The shingle tile die in use by the 
Cincinnati Roofing Tile and Terra Cotta Company is a dupHcat* of 
tlieir Spanish tile die (see Figure No. 98) with the exception of the 
form of the tile. Hence a description is unnecessary at this point. 




r g H4 Muell r SI ngle T le D e 

The Mueliei Shingle Die. — From the illustration it can be seen 
that the die is a very simple one, nothing more than a plain casting 
with the necessary opening for the clay. The corners are belled or 
coned out as shown, to increase the flow of clay at those points. There 
is a serious objection to this styfe of die, that is, the die cannot be closed 
in as it wears away. Thus in a short time the entire die must be dis- 
carded, while if made in halves, it could be closed in and made to do 
service much longer. 

The Parfcenbutg Die. — The die in use by the United States Roofing 
Tile Company at Parkersburg, W. Va., is one devised by themselves. 

By reference to Figure No. 86 it will be seen that it consists of two 
parts, a head plate for the auger machine, and the die proper. The 
head plate is made with friction bosses to hold back the flow of the clay 



280 BULLETIN ELEVEN 

at the center of the tile, while the comers or edges of the die in the head 
are rounded out to allow a greater flow of clay to enter these parts. The 
real opening through the head plate is somewhat larger than the mouth 




Fig. 85 — The Murray Shingle Tile Die. 



piece that is attached by bolts to its face- The mouth piece is made 
in two parts, to permit closing in as the die wears away. 

It will be found in the constructing of a die for running tiles, that 
provision must be made to restrict the flow of clay at the center of the 




Fig. 86— Shingle Tile 



.ates Roofing Tile Company. 



tiles, and to facilitate it at the sides. The extent to which this will be 
necessary will vary with different clays. 

Another style of die that was for a long time used at the plant of 
the Chicago Roofing and Siding Tile Company, at Ottawa, III., and 
made by H. Brewer & Co., of Tecumseh, Mich., was similar to Figure No, 
87, The only essential difference between this die and the one before 
mentioned is that the former is known as a dry die; that is, no heat or 
lubricant is applied to facilitate the flow of clay, while in the latter, 
the use of oil is provided for, making what is known as a wet or lubricat- 
ing die. By referring to the cut it will be seen that the feed of oil takes 
place at the edges of the stream of clay and at an opening between the 
head plate and the mouth piece. This die gave satisfactory results. 

It is believed that our manufacturers should make more use of 
steam heated and lubricated dies than they do, and that less trouble 
would be encountered from side-checked tiles than now exists. 



GEOLOGICAL SURVEY OP OHIO. 



281 



Shingle Tile Cutters* — The problem of cutting the shingle tile bar 
as made by the American manufacturer, is much more simple than 
that of the foreign countries, especially Germany, where it is not only 




Fig. 87— The Brewer Shingle Tile Die. 

necessary to cut off and remove the lug strips from the bar but also to 
cut the tiles with a rounded end, and as mentioned before, often double 
or quadruple streams are t6 be cut- by one movement of the cutter. 
This feature has been shown in Figure ^o. 81. 

The American auger-machine shingle tiles are run out from the die 
in single streams only, and are cut with a square or straight end. This 
simplifies matters very much; all that is necessary to do this is a 
form of reel cutter. The one most in use is shown in Figure No. 88. It 
is made by Mueller Bros, of St. Louis, Mo., but is also sold by the Illinois 
Construction & Supply Co., of St. Louis. 

The clay passing over the roller A, causes the reel to revolve. At the 
ends of the reel arms are stretched the wires, which come in contact 



282 



BULLETIN ELEVEN 



with and sever the tile at B. A pallet is inserted on the endless belt 
at C. As the tile moves forward on the rollers the front end is caught 
by the up-coming pallet and as they both move forward the tile is trans- 
posed to the pallet. The attention of one person is required to feed in 
pallets and help to press the tile onto them. The pallet and tile move 
along on the belt to the off bearer, who places them on a near-by rack 
car. 




Fig. 88 — Mueller's Reel Shingle Tile Cutter, sold by the Illinois Construction 

& Supply Company, St. Louis, Mo. 

This style of cutter is very satisfactory and economical to operate, 
it being possible to cut and place on pallets with the labor of one man, 
the entire output of an auger machine, or in the neighborhood of 
twelve thousand tiles per day. 

At the plant of the Ludowici-Celadon Company, New Lexington, 
Ohio, where a Bonnot auger machine was being used to make shingle 
tiles, it was noticed that a reel cutter was being used to cut the shingle 
tiles, but instead of using the system just described to get the tiles onto 
the pallets, two men were employed with special trowels to take up the 
tiles from the endless belt, and place them on the pallets. 

This method cannot be recommended for several reasons, one 
being that it requires the labor of two men in the place of one, and 
secondly, in order to get the trowel under the tiles on the belt, the opei> 
ator is very apt to mar the ends of the tiles, or possibly start cracks by 
twisting them or allowing them tp bend. 

Again, in removing the tiles from the trowel and onto the pallet, he 
is apt again to bend the tiles or possibly not place them straight on the 
pallet. In the latter method, however, it is possible to place two or 
more tiles on the same pallet, while in the case of the self placing system, 
only one tile can be put on a pallet. 

While some of the reel cutters in use were home-made, such firms 
as the J. D. Fate & Co., Plymouth, Ohio; Mueller Bros., St. Louis, Mo.; 
and the Illinois Supply & Construction Co., of St. Louis, Mo., have 
furnished cutters of the type most in use. 



GEOLOGICAL SURVEY OF OHIO. 283 

Other Methods of Makingf Shingle Tiles by Flow Dies* — There are a 
few other methods of manufacturing shingle tiles that have been used 
with more or less success from time to time in this country, but more 
frequently in the old world. All of these methods involve running out a 
bar of some other cross-section than that of a shingle roofing tile slab, and 
then cutting this bar up lengthwise, as well as crosswise to inci-ease the 
yield of tiles and decrease the power consumed in expressing a bar of 
such small cross-section. There are four such processes worth mention. 

Splitting a Simple Rectangular Bar* — Only in one instance is this 
method known to have been successfully carried on in this country. 
During 1899, the Celadon Terra Cotta Company, of Ottawa, 111., was 
producing tiles by running a stream of clay by auger machine through 
a Brewer die of approximately one inch by six inches cross-section. A 
fine piano wire was attached to the mouth piece of the die, in such a 
manner that the clay column was split horizontally into two streams, 
each being one-half inch thick (see Figure No. 87.) This split stream 
was then cut into lengths by a home made cutter which worked from 
side to side of the stream, punching and counter sinking the nail holes 
in both the upper and lower tiles, as it did so. The two companion tiles 
were placed on the same pallet and dried together, but just before 
going to the kiln, they were separated by inserting the blade of a case 
knife between them. 

While this method of producing shingle tiles was cheaper, it was 
found the tiles did not sell as well as the single stream tiles, owing to their 
under surface being rough from the wire cut. The tiles were also seem- 
ingly somewhat weaker than the regular single stream tiles. 

The principle of forming two tiles at once was good. It would seem 
that its use could well be extended, but it would he better to have the 
tiles issue from the machine separately, one above the other, thus giving 
two perfect tile bars, from which tiles with both surfaces finished could 
be cut. The streams would come together before reaching the cutter, 
"and from there on could be handled as a single tile, thereby saving 
pallets, dryer and kiln space and labor. 

Cutting a Solid Bar Into Several Tiles* — It is not known that this 
system has been used at all in this country, but in the foreign countries 
where tiles with lugs are in favor, it has been largely used on account 
of the cheapness of handling the tiles, and also because it is much 
easier to hold the tiles straight durijig the burning by keeping them in 
the block form. 

Figure No. 89 shows the form in which the tiles are run from the 
auger machine. As the column issues it is cut into lengths suitable for 
the tiles, usually fifteen inches. The block is passed along to a second 
cutter, where wires are so arranged that they cut the false ribs, leaving 
a small portion at one end of each tile to form the lugs by which the 
tiles are to be hung to the roof. The block of tiles is then taken to the 



284 



BULLETIN ELEVEN 




Fig. 89— Roofing Tile Bar in Block 
Form, with points indicated at 
which the cuts are made to Di- 
vide it into Separate Tiles. 



dryer, and finally burned without separating. It will be readily under- 
stood that the portions of the ribs cut away are burned along with the 
tiles, but upon separating the tiles after burning, these waste strips are 
easily removed, and can be reground with new clay and used as grog. 

This system of handling shingle 
tiles is better in some respects than 
any yet discussed, in that they are 
handled in large units, and will give 
less trouble from side checks, owing 
to the fact that the blocks permit a 
moderately open yet solid and sta- 
ble setting, which will not tip or 
rock easily and will permit the free 
circulation of the gases. Time being 
given for the heat to fully penetrate 
each of these blocks, there will be 
no side-checking. 

By this system center marks on 
the tiles — that is, dark blue or black 
spots so often seen in the central area 
of tiles that have been burned too 
fast — when set flat or tight will be entirely obviated, because each tile 
is Separated from its neighbor, thus allowing an easy access of oxygen 
and heat to the central face of the tile. 

Under the heading of setting tiles it will be seen that resort to this 
same method has been had in part by the manufacturers of the ordinary 
flat shingles in this country to overcome side cracks and center markings. 

It is true that fewer tiles can be set in a given kiln space, but the 
per cent, of firsts will be higher, due to the favorable conditions under 
which the tiles are dried and burned. Hence , in the long run the output 
is likely to be larger than in the case of tiles set flat or tight together. 

Cutting; Hollow Blocks Into Tiles, Horizontal Delivery^ — In this 
system the tiles issue from the machine in the shape of a rectangular 
column, the sides of which form the tiles, four in number. As the col- 
umn issues from the die it is cut nearly through by the small steel blades, 
so arranged that they cut the corners of the column. A small web about 
an eighth of an inch thick is left to hold the adjoining sides together. It 
is usually necessary to run the clay rather stiff, to prevent the block 
from collapsing upon being cut. This cutting is usually done straight 
down, and not from side to side. After the column has been cut into 
tile lengths, a wooden form that fits the inside opening is inserted the 
full length of the newly cut block. The form has a handle attached to 
it, whereby the off bearer lifts the block from the cutter table, and stands 
't on end on a pallet either on the floor or a truck. Before removing 



GEOLOGICAL SURVEY OP OHIO. 285 

the form, the necessary nail holes are punched by hand. The form is 
then withdrawn, and the block passes on to the dryer and kiln, where it 
is burned in its original form, that of a hollow block. After burning, the 
block is given a sharp tap with a hammer, when it collapses, forming 
four separate tiles. In this system there are no waste strips, or ribs, 
as in the one previously described. There are, however, some other 
drawbacks. First, great care in handling must be used, to prevent the 
collapsing of the hollow block while cutting, punching and moving it 
to the dryer; second, the blocks are bulky, and much space is lost both 
in the dryer and in the kiln, though it usually happens that much small 
stuff, such as hip-rolls, tower tiles and special cuts, can be nested inside 
the hollow blocks, utilizing much of the otherwise lost space. It is 
obvious that center marks wull not be encountered under this svstem. 
Also, there will be less likelihood of side checks than in single tiles, 
because the corner is the thickest part of the block. Again, tiles 
burned in this manner are less apt to warp, the tiles being held fast to 
each other along their edges. 

Vertical Delivery^ — This method does not differ from the preceding 
except in the method of delivery. 

In Figure No. 90, A represents the auger chamber, or plunger, part 
of the machine. The clay is first tempered in some other machine, then 
fed into the chamber A, where it is caught by the plunger, or auger, and 
forced down through the die. A pallet, B, is placed upon the platform, 
C, directly under the descending hollow column. As the advancing clay 
comes in contact with the pallet, the platform, which is delicately 
counterweighted, moves downward at the same rate of speed as the 
issue of the clay. After descending a distance sufficient to produce one 
length of tile, the platform stops, and at the same instant the auger is 
automatically thrown out of gear, which stops the flow of clay. The 
cutting wires, D, are a part of the movable platform, so that they are 
always at the proper level to cut the column of clay into the desired 
length without waste. At E a shoot, or waster, is made by a wire cut- 
ting off the lower end of the pipe next to the pallet. The purpose of 
this waster is to secure tiles of uniform length if the pallet is uneven or 
warped or if the lower end of the column of clay becomes upset or 
marred by too heavy contact with the platform on which it rests. The 
waste cut also assists in holding the block true during the shrinkage 
period while drying, serving the same purpose for w^hich sewer pipe 
manufacturers put rings of w^et clay under their pipes. In the case of 
shingle tile manufacturers, it is usual to remove the waste cut before 
placing the tiles in the kiln for burning. 

This method is, in some respects, better than that of the horizontal 
delivery. First, the manner in which the form is received, direct upon 
the pallet without rehandling, is better; second, there is less loss from 



286 BULLETIN ELEVEN" 

collapsing; third, the small waste ring is advantageous in that It tends 
to prevent the tiles from separating or warping at the lower end upon 
drying. 

There is, however, one feature that 
is possibly not so good as the horizontal 
delivery, namely, the output will be 
smaller, owing to the fact that the ma- 
chinery must be thrown out of gear or 
stopped at the end of -each tile length to 
allow for the cutting and removal of the 
tile, while in the horizontal delivery system 
the issue can be continuous. 

In Figure No. 91 it will be seen that 
the inventor provided a reeutting appa- 
ratus to cut and remove these parts of the 
lug strips not needed for the lugs. This 
he accomplished by making a form carry- 
ing four wire cutters substantially as 
shown in the drawing. This form was 
inserted in the hollow block, until the 
block F rested upon the pallet. The 
handle H was then given a partial turn, 

^^Ji- ^9~yf^'?*^i?^'7^iy °* so that the arms I engaged with the springs 
Shmgle Tiles in Block Form, ,..,.. , i *u ** t.- . 

J, which in turn pushed the cutters K out- 
ward to a position where they would cut the lug .strip free from the tile. 
Upon withdrawing the form, the severed strips were then removed by 
hand. In the case of tiles with nail holes, it would only be uecessarj' 
to insert a form at the upper end a short distance to hold the pipe in 
shape while punching. 

Shingle Tiles by Powei Presses. — By the use of a power press it is 
possible to make many forms of shingle tiles that are impossible to 
make on the flow die machines. The greatest difference lies, however, 
more in the matter of ornamentation, or outline of the tiles, than any- 
thing else. 

The use of auger machinery to run out and cut off the blanks, fol- 
lowed by the power press to give them any desired finish, or lugs, or 
shape, or ornamentation, therefore constitutes the most modern and 
effective equipment for shingle or any kind of roofinR tiles. Whatever 
part of the output that can be used in the form in which it comes direct 
from the auger machine can be so made. Where the trade demands 
more ornate shapes, the use of a different die and different reel cutter 
and power press immediately permits this line to be made also. 

The best example of the press-made shingle tile is found in the plant 
of the United States Roofing Tile Company, Parkersburg, W. Va, This 
company is manufacturing a tile of somewhat unusual shape, being 



GEOLOGICAL SUKVBT OP OHIO. 287 

patterned after the ordinary wooden shingle; i. e., tliick at the butt end 
and tapering down to quite a thin section at the other end. The object of 
this shape is to allow the tile to fit more closely to the sheathing boards. 





Fig. OI^The Robinski Lug-Cutting Apparatus. 

Not only does the tile vary in thickness from end to end, but in 
some of their patterns, the monotony of an otherwise plain tile is broken 
by an outline of gutters and raised parts on the portions of the tile which 
extend from the next superposed 
tile on the roof. Suiih shapes ex- 
clude any other method of manu- 
facture than that of pressing. 

In the manufacture of these 
tiles, the company first runs blanks 
on one of J. D. Fate & Go's, com- 
bined double shaft pug mill and 
auger machines. The blanks are 
about one inch thick by five 
inches wide and are cut fifteen 
inches long by a reel cutter. 

From the cutter the clay 
blanks are conveyed by an end- 
less belt conveyor to the presses 
(see Figure No. 93J. 



288 * BULLETIN ELEVEN 

• 

Just as the blanks leave the cutter, they are coated or painted on 
their upper face with an oil especially made for this company by the 
Upson Soap Company of Parkersburg, W. Va. The oil is applied to 
prevent the clay from sticking to the metal dies of the press. As the 
blank reaches a point opposite the press, it is picked up by the press 
feeder (see Figure No. 94) and fed onto the nearest die of the pentagon 
on the press. As the pentagon of the press revolves one-fifth revolu- 
tion, it brings the blank of clay under the top die where it receives a 
pressure that causes it to flow out and fill every part of the die box, 
each blank being cut to a length that is just sufficient to exactly make 
one tile. After the pressure has been applied, the pentagon revolves 
one-fifth revolution, the tailsman or off-bearer places and holds a receiv- 
ing pallet on the tile, and as the pentagon moves to its next position, 
the tile loosens from the die resting on the pallet (see Figure No. 9o). 
The off Ixjarer then places the laden pallet on a rack where the tiles are 
examined and the nail holes punched by boys. This company is manu- 
facturing three styles of pressed shingle tiles, one form of which is shown 
in Figure No. 96. Other companies are making various forms of pressed 
shingle tiles. Among them arc the Ludowici-Celadon Company, Mound 
City Roofing Tile Company, Alfred Clay Company, and the Detroit 
Roofing Tile Company. 

Shingle Tiles by the Dry Press Process. — While this fascinating 
method of working clay has on several occasions been tried 
in this country in the manufacture of roofing tiles, it has never 
yet proved successful. The trouble has been that the tiles 
could not be made dense enough to withstand the weather. In addition, 
the roofing tile dies are usually of complex enough shape, so that the 
dr}*^ powder filling the die would have a variable thickness in different 
parts. On the descent of the plunger, the thick part of the powder 
layer would be much more densely compressed than in other parts where 
the clay was thin. Grave irregularities of structure are thus produced, 
and the process is not practical. By packing the die with the powder 
in advance of the descent of the plunger, and cutting out the excess clay 
in the thick parts by hand, it is perfectly feasible to make a tile of irregu- 
lar cross section and of uniform density, but the cost of hand packing 
the die for each tile is too great. 

If any success is reached, it will be by the use of previously tempered 
plastic clay, partially dried, granulated, and pressed with enough water 
in it to make a dense bod}^ which flows under heav}' pressure and forms 
a i^erfect bond. Such a process is used in electrical porcelain manufac- 
ture, and it seems possible that it might be introduced in roofing tile 
manufacture, especially for the simple forms. Exactness of shape, 
a great desideratum in roofing tile manufacture, would be secured in 
the highest degree. 



OEOLOGICAL SURVEY OP OHIO. 



Fig. 93— Cutter and Tile Blanks, United States Roofing Tile Company. 



Fig. 04 — Feeding Side of the Roofing Tile Press, United States 
Company. 



290 BULLETIN ELEVEN 

THE FORMING OF SPANISH TILES. 

.The roll tiles in their various forms have been used more widely 
than any other single style or shape. Among the most ancient tiles, 
traces of the roll or normal tiles arc to be found. Their use has been 
not only very extensive, but satisfactory from both the artistic and 
practical point of view. 

In the manufacture of this style of tiles in the United States, many 
improvements in form and methods of manufacture have been made. 
It is rare to see this style of tiles made in this country in any other 
manner than by power machinery, while in the old world many are 
made by hand either in plaster moulds or on hand presses. 

Hand Pressing in Plaster Moulds, — In making this shape in hand 
moulds, it is necessary to have the clay prepared quite soft and well 
kneaded, with the plaster mould on a low bench or table. The presser 
takes up a mass of clay sufficiently large to make one tile with a little 
to spare, and rolls or works it into a **grub" in shape like a loaf of rye 
bread. This roll is then thrown into the mould with considerable 
force, and batted by the hand and forearm until it fills every part of 
the mould- The excess is then scraped off, or cut away by means of 
a straight-edge or wire-cutter. The necessary lugs or nail holes are 
made, and the inside is ''slicked" with a rubber card or sponge. The 
mould is then set aside, until the clay shrinks loose from the plaster. 
The tile is then emptied out onto a pallet, while the mould goes back 
to the bench to be refilled. 

With an ordinary granular clay, not too adhesive, that will give 
up its water freely to the plaster mould, from ten to twenty moulds 
will be found sufficient to keep one presser busy, but should the clay 
be extremely plastic, a much larger number will be required. 

This method of manufacture is the most expensive of all, and at 
the same time the tiles are apt to be weak, because very little pressure 
can be applied in the manufacture, and the clay is worked very soft 
and rather lean and sandy. 

Pressing in Hand Power Pfess*--The next method used in the 
manufacture of Spanish tiles is by hand-power press. While this method 
is perfectly possible, it is not used at all in this country, at least on 
regular tiles. Special Spanish tiles, like tower tiles, eave tiles, hips and 
valleys, etc., are to some extent made on hand presses. In the plant 
of the Cincinnati Hoofing Tile and Terra Cotta Company, all special 
Spanish tiles are made on a Perfection Hand Press, manufactured by 
the C. W. Raymond Company, Dayton, Ohio. At the Western Roof- 
ing Tile Company, special Spanish tiles were made on a small hand press 
of the eccentric type. This press had been formerly used in a glass 
works for pressing glass and had been fitted with new dies for the clay 



GEOLOGICAL 8UBVET OP OHIO. 



Pig. 96— Press-made Shingle Tiles, Uoited States Roofing Tile Company. 



292 BULLETIN ELEVEN 

business. The name of the manufacturer could not be obtained, but 
it is not important, as the machine is not regularly on the market. 

Spanish Tiles by Flow Die Processes.— The simple straight ''S" 
tiles, without lugs or interlocking features, permit the use of flow die 
methods, and as this method is always cheaper than pressing, it is cer- 
tain to be used whenever it is available. Both types of flow die ma- 
chines, plungers and augers are used. 

Spanish Tiles by Plunger Machine* — The plunger machine itself 
has been described to some extent earlier. The only example of the 
use of this machine for the manufacture of Spanish tiles found in the 
country in 1908 was seen at the Cincinnati Roofing Tile and Terra 
Cotta Company, Winton Place, Cincinnati, Ohio. 

At this plant, much attention is paid to having the clay well tem- 
pered before reaching the plunger machine. It is ground until it passes 
an eighteen-mesh screen, then enters a storage bin located on the second 
floor of the building. From the bin, the clay is introduced by spout 
into a seven-foot wet pan, manufactured by the American Clay Ma- 
chinery Company. 

In the wet pan the clay is tempered with water for a period of 
ten minutes or so, and is then unloaded onto a belt conveyor which 
delivers it to a hopper placed above the charging hole of the plunger 
machine. This hopper will hold about two wet pan charges at a time. 
A man is stationed at the hopper, where he feeds the proper amount 
of clay into the machine on each stroke by a shovel. The output of the 
machine depends upon the feeder, for he can, by overfeeding, cause 
much waste and loss to occur. In the case of the Spanish tile the amount 
of clay needed for each 'tile is, roughly speaking, about an ordinary 
shovelful, but as the clay is in lumps of more or less irregular size and 
shape, it is not always possible to feed the proper amount. In order 
to have a sufficient amount, the feeder feeds what he thinks will be 
a little more than enough. 

The output for this plunger machine, under the most favorable 
conditions, will not exceed 5,000 Spanish tiles. More often the daily 
output does not exceed 3,500. With an auger machine and the same 
number of operatives, these figures can easily be doubled. 

Cincinnati Spanish Tile Die* — In Figure No. 98 is shown a line 
drawing of the Cincinnati Spanish tile die. The drawing on the left 
represents the outward face of the die, from which the finished tile col- 
umn issues. On the fight is shown the rear or inside face of the die, 
with the beveled shoulders and the belled or coned corners, each of 
which is necessary to control the proper flow distribution of the clay. 

The sectional drawing more clearly shows the amount of bevel on 
the main part of the die. The corners, however, receive a slightly 
greater increase of bevel. 



GEOLOGICAL SURVEY OF OHIO. 293 

It will be seen that this die is made in two parts, which divide at 
the eJitrenie edges of the tile, as indicated in the drawing on the face 
side of the die. The two parts are fitted very carefully together, arid 
are then held in that position by the two bolts, as shown. 

When the die wears away, allowing the tile to come too thick, the 
halves arc taken apart, and the points of contact dressed off until the 
projjer thickness is again secured. By this means it is possible to pro- 
long the life of the die very materially. 

Ordinarily these dies arc made of cast iron, though at times chilled 
iron and steel have been used. Jn the latter materials the dies are ex- 
tremely difficult to dress or file in order to get the proper feed of clay. 



Fig. 97— Hand-power Press, Western Roofing Tile Company. 

Periodic Cutters. — It will be found very necessary to have a well- 
constructed and accurate cutter for handling Spanish tiles. At the Cin- 
cinnati plant a cutter manufactured by the American Clay Machinery 
Company is being used. 

Figure 99 shows the cutter in detail, except that the angle clippers 
are not required on the cutter as used at Cincinnati. In operation 
the cutter works about as follows: As the "S" sha])ed bar leaves 
the plunger, it passes over a wool-covered, oily roller, shown in cut, 
which lubricates the under side of the bar, so that it moves freely over 
the cutter table without sticking. The bar is allowed to run out until 
its outer end has passed the second slot shown in the cut. The lever is 



294 



BULLETIN ELE\TBN 



then pulled down, the block A comes in contact with the top of the clay 
column, where it rests, while the two cutting wires pass on down through 
the clay into the slots. As the wires descend, the bolts, or pins, encir- 
cled by springs, descend also, punching the nail holes. The handle is 
now released, the counterweight raises the cutting frame clear of the 
tile. The block A remains on the tile until the cutting wires have 
cleared the clay, then the block moves up out of the way. This is done 
to prevent the wires, on their return through the clay, from "feathering" 
the ends of the tile. Immediately at the outer end of the cutter the 
off bearer stands with a trowel (see Figure 100). 

This trowel he inserts under the pan of the tile while on the cutter 
table, then lightly supporting the roll of the tile with the other hand 
he lifts the tile from the table and places it on a pallet near by. 

The work of off bearing is not only very tiresome, but very exacting 
as well. Much pains must be taken to see that the tiles are placed on 
the pallet straight, otherwise they will dry crooked, and must be re- 
turned to the dry pan as scrap. 

At the Cincinnati plant the tiles are placed three deep on a single 
pallet. Formerly they were placed five deep, but this was abandoned. 






Fig. 98— Spanish Tile Die, Used by the Cincinnati Roofing Tile & Terra Cotta 

Company. 



In Figure 101 can be seen the three tiles on the pallets in place on 
the truck. The pallets will be discussed under the section on dryer 
cars and pallets. 

Spanish Tiles by Auger Machines* — The manufacture of Spanish 
tiles on the auger machine differs from that on the plunger machine 
in that the column of clay moves continuously from the auger, instead 
of intermittently, as from the plunger. It will be understood that with 
the moving bar a cutter must be provided that moves with the bar, 
while with the plunger machine the cutting table remains stationary, 
and cuts only when the bar is at rest. It would be impossible to make 
a straight cut through a moving clay bar unless the cutting wires were 
moving at exactly the same speed as the clay. The backward and for- 



GEOLOGICAL SUBVEY OF OHIO. 



295 



ward movement of the cutter does not move to exceed eight or ten 

inches, because ample time is given to make the vertical cut and return 
the cutting wires to the original position while the clay bar travels 
that distance. By a small lever, under control of the operator's foot, 
the entire table is returned to its original starting point after each cut. 
At the plant of the Ludowici-Celadon Company, New Lexington, 
Ohio, where more auger- machine Spanish tiles are made than at all other 
American plants combined, it was found that they are using four auger 
machines of various sizes, the largest one of the four being used on 
Spanish tile. It is not meant by this that the particular machine in 
use by them is any better suited to the work than other machines of 
equal capacity, but it indicates the strength and power required to force 
clay out from so small and so irregular an aperture. The Ludowici- 
Celadon Company is using wooden pallets, as shown in the figure, and also 
places tiles three deep on one pallet. Their cutter is of their own de- 
sign. In general it is not widely different from the American Clay 



Pig. 99— Spanish Tile Cutter, by the American Clay Machinery Compatiy. 

Machinery Company's cutter (Figure No, 99), except that it is much 
stronger and is movable. The cutting wires pass through the tile with 
a downward shearing motion instead of straight down. 

Spanish Tiles by Power Presses, — ,4t the present time there is 
only one type of press in use for the manufacture of regular Spanish 
tile— namely, the revolving pentagon press. 

Revolving Table Press. — A number of years ago, at Ottawa, 111., a 
press of the revolving horizontal table type was used for making small- 
sized Spanish tiles. This press was manufactured by D. J. C. Arnold, 




296 BULLETIN ELEVEN 

of New London, Ohio. Metal dies were used on this press, lubricated 
by a light oil applied by hand. Blanks were first made on an auger 
machine. These were fed, one at a time, onto the dies of the revolving 
'table. In due time the blank crime 
under the upper die, where it re- 
ceived the necessary pressure to 
shai)e the tile. The table in its next 
move brought the die with its newly 
pressed tile to the "dumper," who 
placed a pallet upon the tile with one 
hand, and turned the die half over, 
or until the tile loosened and dropped 
onto the pallet. The dies were Fig. 100 — Trowel Used for Remov- 
hinged at one side to permit of i'lg Spanish Tile from Cutter. 

dumping. To operate the press under the conditions at Ottawa three 
men and a boy were required — a press man, oiler boy, feeder and 
dumper. The daily output was from thirty-five hundred to five 
thousand. 

This press was not a success, economicall}*^, the output being too 
small for the number of men employed. If it were improved by sup- 
plying an automatic dumping device and automatic oiler, it would 
probably be thoroughly practical and satisfactory. 

There is a class of work that could be done on it cheaper than by 
the ordinary drop presses used on special work. 

The Pentagfon Press* — Five different presses of this type were 
found in use for the manufacture of interlocking Spanish tiles: at the 
Western Roofing Tile Company, one press manufactured by Crawford 
& McCrimmon, Brazil, Ind.; at the Detroit Roofing Tile Company, one 
press, manufactured by the Illinois Supply & Construction Co., St. 
Louis, Mo.; at the Ludowici-Celadon plants, Chicago Heights and 
Ludowici, Ga., presses manufactured for them in Chicago, copied from 
the Ludowici tile press of Germany; at the Ludowici-Celadon Com- 
pany's plant. New Lexington, Ohio, presses manufactured by the 
Rogers Machine Tool Company, of Alfred, N. Y. 

In three of the above plants, plaster dies were being used. In the 
other two cast iron. 

The methods employed by the various plants in the production of 
press-made Spanish tiles are the same, with the exception of the lubrica- 
tion of the metal dies. 

The first step is that of producing the blank from which the tile is 
to be made. In every one of the above plants this is done by auger 
machines. The J. D. Fate Company, of Plymouth, Ohio, has five 
double-shaft combined pug mill and auger machines at work on Spanish 
blanks, and the Bonnot Company of Canton, Ohio, has one. 



GEOLOGICAL SURVEY OF OHIO. 297 

Neither of these companies claim that its press or auger machine 
is specially or exclusively for the production of Spanish tiles. They 
use the same machinery on any and all of the styles of tiles they produce. 
For instance, The Detroit Roofing Tile Company is making six or seven 
styles and sizes of tiles on a single press, it being customary to run a 
good stock of one kind of tiles, and then change the dies and run another 
style. Similarly in the production of blanks of Spanish tiles, the auger 
machine must make blanks for all kinds and oftentimes prepare 
the clay for the modeling floor as well. The clay coming from the pug 
mill or other tempering device, or if it has been aged after the temper- 
ing, coming from the cellar, is fed into the auger machine, which forces 
it through the mouth piece in a bar of the desired shape. In the case 
of the Spanish tile blanks, it is usual to have a double stream die, wdth 
tw^o columns issuing from the machine at the same time. These streams 
are usually about two and one-half inches by four inches in cross section, 
with rounded corners. Upon leaving the die they pass under a reel 
cutter, which cuts the two bars into lengths of about twelve inches, 
which will furnish a slight excess of clay over that needed for a single 
tile. 

As the blanks pass from the cutter, they are carried by an endless 
belt to the pressman or feeder. Immediately behind the feeder or a 
little to one side, is a low bench, upon which a boy ''hacks'* the blanks 
as they are delivered by the belt. It is usual to keep a stock of fifty 
to one hundred blanks on the bench at all times, to tide over short stops 
of the auger machine. Before commencing work it is necessary to see 
that the plaster dies are well saturated with water. This being done, 
the feeder takes up a blank with both hands and slams it with con- 
siderable force onto the face of the die in front of him. The pentagon, 
making one-fifth revolution, brings this newly filled die under the top 
die, which descends, forcing the blank to fill all parts of the space between 
the top and bottom dies and squeezing out all excess clay. The pentagon 
again moves, the off-taker or talisman places a pallet upon the tile, 
and waits for the die to reach the third position, when the tile releases 
very easily. 

The pallet (see Figure No. 153) with its tile is then put on 
a belt conveyor driven from the pentagon shaft in such a manner that 
it moves forward about two feet with each movement of the pentagon. 
Thus, between intervals, the edges of the tiles are ''skinned,*' or trimmed 
by boys or girls, one on either side of the belt. It is usual to have another 
known as the "puncher" whose duty it is to punch the nail holes, or to 
perforate the small lug on the under side of the tiles by which they are 
wired to the roof purlins. Another boy or man is required to take the 
tiles from the belt after they have been trimmed and put them into the 
dryer cars. 



BULLETIN ELEVEN 



Fig. 101 — Plunger Machin 



Fig. 102— Tiles Delivering from Press. Detroit Roofing Tile Company. 



GEOLOGICAL 8UBVEY OP OHIO. 299 

The output of Spanish tites on a pentagon press will run from four 
thousand to six thousand per day. The latter figure can seldom be 
attained. 

Lubrication of Dies. — Where metal dies are used for Spanish tiles, it 
is necessary to keep the dies hot to assist the clay in releasing. This is 
done in one plant by steam, which passes directly through the backing 
of the die. At another natural gas flames were used, the flames 
coming in direct contact with the face of the dies. The oil used for 
lubrication was the Atlas press oil, made by the Standard Oil Company. 

Where steam was used to heat the dies, the oil is sprayed onto the 
dies by compressed air. In the other plant the under side of the blank 
was oiled by passing over a wool-covered roller, which was dipped in 
oil. Instead of oiling the upper face of the blank the oil was applied 
to the top die itself by hand. 



Fig. 103 — Home 

FORMING OF INTERLOCKING TILES. 

The interlocking tiles in this section refer to the regular inter- 
locking tiles of commerce, such as those known as the French A, T-1, 
D-l, etc., manufactured by such firms as the Ludowici-Celadon Company, 
The Mound City Roofing Tile Company, The l^troit Roofing Tile Com- 
pany, The Xational Roofing Tile Company, The Alfred Clay Company 
and others. It must also be understood that these same companies 
manufacture interlocking tiles of both the shingle and Spanish va- 
rieties, and various other patterns already discussed. These forms 
of interlocking tiles are becoming the most widely manufactured 



300 BULLETIN ELEVEN 

at the present time in this country, if not in the world. This is due to 
the universal use to which they can be put; that is, they can be applied 
on almost any kind of roof construction, such as open or closed con- 
struction, either wooden or steel. They are considered the cheapest 
tiles to manufacture per square, on account of their large size, can be 
sold at the lowest price, and are the cheapest to apply. Hence, it is 
easy to see why they are so popular. With the use of proper principles 
in designing the locks they also make one of the best roofs. 

The methods of manufacture in the various plants are but slightly 
different. In every case the blanks are made on auger machines, which 
are undoubtedly the most efficient for this work. Of the various auger 
machines found in use for this work, there were six plants using Fate 
machines, one plant using a Bonnot machine, and two using the Ameri- 
can Clay Machinery Company's machines. 

Shape of Blanks* — As to the shape of the blank, six of the plants are 
running bars of about two and one-half inches by four inches, which 
are then cut into suitable lengths, about fifteen inches, by reel cutters 
of the type to be seen in Figure No. 103. 

These bars are made both in single stream and double 
stream dies. There is something to be said for the double 
stream die here, which perhaps does not apply with equal force 
where it is expected to use the bar after cutting as a finished 
product, viz.: the die pressure is much less, and the power required to 
run the auger machine is materially decreased. Since the blank under- 
goes a complete rearrangement in pressing, any faulty structure, if any 
exists due to double stream dies, is eliminated. On the same reasoning 
a side-cut brick die and cutter could be used equally well, with still less 
die pressure, but no instance of this was found. It is possible that the 
wire-cut surface of the side-cut brick might still persist in some degree 
after pressing, which of course would not do. 

At two plants the blanks are run wdth outlines t^onforming to those 
of the tiles to be made. The blanks have the side-tongues and grooves, 
and the press then only has to form the head and heel locks. 

As to the relative merits of shaped vs. unshaped blanks, it can 
be said that where plaster dies are used, the thick two and one-half 
inch by four inch block form is the better. The die fills better if the 
clay has to flow vigorously, than if the blank is nearly shaped in ad- 
vance, and changes shape but little in pressing. Also, the tiles seem 
to release from the die with less trouble where the clay flows, than 
when fed in pre-shaped blanks. 

In the case where metal dies are used, the reverse is certainly true. 
With metal dies, oil must be used to prevent the clay from sticking. 
If the clay has to flow vigorously under pressure in the die, it will 
scour the oil from the metal, leaving the surface bare in the central 
part, where the flow has been longest kept up. The tile will then stick 



GEOLOGICAL SURVEY OF OHIO. 30 1 

in the center. Also, the oil that has been pushed along ahead of the 
clay enters the tongue grooves, and prevents the clay from properly 
filling them. 

It will thus be seen that it is better to run the blanks for metal 
dies of approximately the same outline as the finished tile, leaving the 
work of the press as light as possible. 

The mere forming of the end locks does not cause any extensive 
motion of the main part of the clay and hence the oil is not disturbed, 
and still acts as a separating medium between the metal and the clay. 
Each form of blank therefore has its proper place, depending on the 
kind of die used. There is one objection, however, to the plan of run- 
ning blanks of a shape to conform to the tiles, viz., it is not possible to 
store very many of them in advance owing to their thin section and 
the ease with which they dry out and are broken. This requires the 
auger machine to run almost continuously to supply the blanks as 
needed. 

In the case of the simple rectangular blank, large numbers of them 
can be piled up ahead of the press consumption, thus making it possi- 
ble to change dies on the auger machine and run other kinds of ware 
a part of the time. In plants of moderate size, this latter point will 
be found of considerable weight. 

Pressing* — The pressing of the interlocking tiles is not different 
in any but the most trivial details from the pressing of such tiles as have 
already been discussed, and no further tinie need be spent on it at this 
point. 

Forming Interlocking^ Tiles on the Auger Machine* — There is a 
great field for the introduction of interlocking tiles made on the auger 
machine in this country, which is not receiving as yet any attention. 
Not a single plant in this country is making tiles of this kind at the 
present time, and only one instance was found where work along this 
line had been done in the past. 

Just why our tile manufacturers have not taken to the auger-made 
interlocking tiles can only be surmised. Foreign roofing. tile makers 
have for many years seen the possibilities of the auger machine on this 
class of goods, and have perfected many ingenious devices in the matter 
of dies and cutting tables to properly form the bar and cut it into inter- 
locking tjles. 

In the nature of the case, it is only possible to run the locks along 
two parallel sides of the bar. If side locks were made by the flow die, 
the end locks cannot be made, and vice versa. It is quite probable 
that the lack of end locks has been the objectionable feature of auger- 
made interlocking tiles which has prevented their adoption in this 
country. This objection has weight, of course, but not more weight 
than it has in the case of auger-machine Spanish tiles, so popular at 
the present time. 



302 BULLETIN ELEVEN 

By laying such tiles on closed-roof construction, with roofing proper 
beneath, they can be made to give satisfaction. No one would think 
of applying the auger-machine Spanish tiles on an open construction 
roof, i. e., on purlins only; neither should anyone think of so doing 
with the auger-machine interlocking tiles. The auger-machine interlock- 
ing tiles provide a cheap material for cheap structures, a field that is 
only occupied at present by the culls of the other styles of tiles. Any 
one undertaking to enter a cheap auger-machine interlocking tile into 
the field of the pressed variety would unquestionably fail in his 
attempt. 

The firm that at one time mode interlocking tiles on the auger 
machine was the Ludowici Celadon Company, at their New Lexington 
plant. The tiles as manufactured by them were of such a cross section 
that the under side of one tile would fit the lines of the upper side of 
the next below. 

One style of auger-machine interlocking tiles does provide a partial 
head lock. These tiles are made from a rectangular pipe, the two interior 
faces of which are separated by some little space. After the bar has 
been cut into lengths, as shingle tiles are cut, it passes to a second cutter, 
which notches out the ends of the tiles as shown in the cut below. 

These notches allow the lower end of the upper tile to lap over the 
upper end of the lower tile, thus making a partial lock. 

Plaiter Dies vg. Metal Dies. 
^The first use of plaster of 
Paris for roofing tile dies dates 
far back into the past. It is 
doubtful whether any material 
will ever be found to supplant 
it. At least on most clays it 
is the only material that will 
give a perfect tile. Metals of 
various kinds have been tried, 
and are being u.sed at the pres- 
ent time, but no single case has 
yet been seen where tiles made . 
on metfil dies arc free from- 

flaws and checks due to the pig. 104— New Lexington Auger-made 
necessary use of some kind of Interlocking Tiles, 

lubricating oil. With tiles from plaster dies, this cannot be said. 

By analyzing the conditions in the two cases, it will be clearly 
understood why the above is true. 1st, with plaster dies, it is necessary 
to work the clay softer than with metal dies; 2nd, plaster dies are neces- 
sarily kept saturated with water. With metal dies, their surface must 
be oiled with a heavy oil. When a blank is fed onto either kind of die. 



GEOLOGICAL SUKVEY OF OHIO. 



303 



and the pressure is applied, the blank is squeezed very quickly down 
to the thickness of the finished tile. In undergoing such a radical 
change of shape, many small checks and seams will infallibly develop. ' 
On the plaster die, which is saturated with water, the water will find 
its way to these newly developed checks, softening their edges and 
helping them to mend or unite while under pressure. In the case of the 
metal dies, the oil used for lubrication will enter the checks just as the 
water does with plaster dies, but instead of assisting them to knit, 
they are prevented from doing so. There may be certain clays, high 
in froe silica, which would prove an exception, but for fat, plastic 
clays, such as roofing tiles are usuall}^ made from, the above certainly 
holds true. The fat clays work much the best on plaster dies. Another 
fact comes into consideration in this connection, viz., the clay must be 
in a markedly more plastic condition for forming on plaster dies than 
for metal. This assists powerfully in preventing as well as in mending 
checks or flaws. 

On metal dies, the stiffer the clay can be worked, the better it will 
release from the die, but the more numerous the checks will be. It is 
true that metal dies are being used with more or less success on some 
cla3's. What the properties of a clay are which determine whether 
it can be successfully worked on metal dies or not has never been satis- 
factorily worked out. 

Roughly speaking, the 



more plastic, fine-grained 
clays, low in gritty sub- 
stances, are best suited to 
plaster dies, while clays of 
the opposite physical prop- 
erties are best suited for 
metal dies. The strongest 

objection to plaster dies is 

that they are expensive to Fig- 105- Auger-made Interlocking Tile. 

keep in repair. It is necessary on most clays to renew them every day. 
Top dies are often renewed twice per day. 

To keep this work up requires the work of one man and a helj^er 
in a five-press plant. The same workman, however, also makes all the 
plaster dies needed about the plant, such as crestings, hip-rolls, copings 
and special pieces. Every roofing tile establishment has to be able to 
meet calls for these ornamental pieces, and at least one plaster worker 
is a necessity, anyhow. 

The plaster of Paris used should be of a good grade, and should be 
very finely ground for the best results. The average price per barrel 
of suitable plaster is from $2.25 to $2.10, or often less when bought in 
carload lots. 



' uiujrjjujfimuiMMUffM 




304 



BULLETIN ELEVEN 



Making Plaster Dies* — The art of making plaster dies for roofing 
tiles is by no means a simple thing. Much experience is required 
to work the plaster so that when cast the resultant dies will not be full 
of air-blebs, known to the trade as ''rat holes." If blebs appear on the 
surface or in the body of the die, the plaster will have to be chipped 
out and the casting remade. 

To make the die, three parts are required, the upper and lower die 
shells and the tile matrix. 

The shells are cast iron boxes, made to conform roughly to the 
shape of the tile. They are made about one-half inch longer and wider 
on each end and side than the tile, and about three-fourths inch deeper 
than the thickness of the tile. The thickness of the iron in the shells 
is usually about three-eighths to five-eighths of an inch on the sides and 
three-fourths of an inch for the bottom. 





D Q^E 



3 — I 




Fig. 108— Die Shells and Matrix for Making Plaster Dies. 



In Figure No. 106, A represents the matrix of the tile. This matrix 
is an exact pattern of the tile to be made. It is usually made of cast 
iron — though aluminium is better — and is finished off perfectly smooth 
and to size, with dividing lines on the sides and ends to mark the depth 
to which the matrix is to be set in the die shell when casting new dies. 



GEOLOGICAL SURVEY OF OHIO. 



305 



B and C represent the upper and lower die shells, with the plaster in 
place. D shows a cross section of the dies when pressed together. E 
represents the clay necessary to form the tile, shown by the heavy 
shading. F represents the plaster facing of the die, and G the cast iron 
die shells. Assuming that the new die shells are to be lined with plaster, 
the steps to be taken are as follows: 

First. Swing or adjust the matrix to its proper level in one of the 
die shells. This is done by blocking it up on small pieces of wood to 
about the proper level, and then adjusting it by small pats of clay on 
the top of the wooden blocks. The matrix is then tapped with a mallet 
until it takes a good bearing and is on the right level. 

Second. The space surrounding the matrix and separating it from 
the shell is noV filled in with plastic clay. When filled, it is carefully 
smoothed and finished so that it coincides with the line of the matrix. 

Third. The upper surface of the matrix is now painted or coated 
with a dressing called *'dope," composed, as a rule, of soap and some 
sort of fat, preferably lard, boiled in water to a creamy consistency. In 
some cases paraffin dissolved in kerosene oil is used. Each plaster worker 
has his own preparation, which he thinks is best. One receipt runs: 




Fig. 107 — Press for Plaster Dies. 

For four pounds of soft soap, boiled in four gallons of water, add one 
pound of tallow, and stir thoroughly. In any case the function of this 
dressing is to keep the plaster from adhering to the surface of the matrix. 
It is always of a greasy nature, but the use of a greasy soap solution 
seems usually preferable to the use of oils direct. This dressing is ap- 
plied to the matrix face, and rubbed off until it has just a thin film left 
upon it. 

Fourth. Preparation of the plaster is next. Should the die require 
one pailful of plaster, take between one-third and one-half pail of soft 

20— G. B. 11. 



306 BULLETIN ELEVEN 

tepid water, and sprinkle handfuls after handfuls of loose, fluflfy plaster, 
free from lumps, into the water. This must be done somewhat slowly — 
not much faster than it will sink beneath the surface of the water. Con- 
tinue to sift plaster with the hand into the water until the plaster ap- 
pears to build up in a cone above the surface and only a narrow ring 
of water is showing around the edges of the cone. This is allowed to 
stand for a few moments, sometimes for several minutes. The plaster 
and water are now to be worked and stirred with the hand, first seeing 
to it that all parts of the mixture are free from lumps. By a peculiar 
twist of the hand and forearm, the plaster can be made to boil up, so 
to speak, from the bottom of the pail to the top. This working of the 
plaster allows entrapped air to escape, and must on no account be done 
in such a way as to chum more air into the mixture. Th6 stirring con- 
tinues until .by the feeling of increasing density, or viscosity, and also 
of warmth, the plaster worker knows that it is time to cast. 

Fifth. Carefully coat the surface of the matrix with a layer of 
plaster to the depth of about one-half inch. Be very careful not to 
entrap any air bubbles on the face of the matrix under the plaster. The 
balance of the plaster is now poured into the empty upper die shell. 
At the moment when the plaster assumes sufficient set so that it will 
not fall out of the shell, the upper shell is turned over onto the lower 
one. Then slip the two cases under a screw press, and bring a pressure 
to bear until the two shells meet at their parting lines. The excess 
plaster escapes. In ten or fifteen minutes the screw is released, and the 
dies taken out and separated. It usually happens that the matrix will 
adhere to the newly made die. If so, it is gently loosened, but not 
removed. 

Sixth. The lower shell is now cleaned of the clay used to hold the 
tile matrix in position, and is placed ready for its charge of plaster. 
The matrix and the exposed parts of the newly made upper die are now 
coated with "dope." Another pail of plaster is prepared, and the work 
repeated. When taken from the screw press, the shells are opened, 
and the matrix is carefully removed from the last made die. 

Sevefith, The dies are now allowed to stand for some time — a half 
day if possible — and then, before Ubing, they are placed in a tank of 
water and allowed to soak up all the water possible. This takes ten or 
fifteen minutes, sometimes more, depending on the hardness of the 
plaster. 

The hardness and strength of the cast die varies with the density of 
the plaster or in other words with the lack of porosity, produced by work- 
ing all the plaster possible into a given quantity of water. Plaster made 
up with the minimum of water consistent with full hydration and ap- 
plication is called "strong" plaster and is relatively dense. When as 
much water is used as will permit the plaster to set, a spongy soft cast 
is obtained and is called "weak." Both kinds have their particular 



GEOLOGICAL SURVEY OF OHIO. 307 

£eld. For instance, in dies, it is desired to have a die that will stand 
wear or abrasion, and it is not necessary for the plaster to absorb much 
water. Therefore, in dies, the plaster should be strong. At times it 
has been recommended to use lime water, that is, calcium hydrate solu- 
tion, in the working of the plaster dies, to harden them. Shellac or 
gum, as used in stucco work, has also been tried, but the hardening 
of the die must not be carried too far, or the clay will stick to it instead 
of releasing as it will from a die of moderate hardness. 

For plaster molds to be used in hand pressing, it is desirable to have 
the water absorb water from the clay rapidly. Hence, the plaster is 
worked with more water, producing a relatively weak or porous mould. 
The foregoing process represents the common one in use in renewing 
plaster dies. 



Fig. 108- 

Itoo Maiter Moulds, — A better process for the renewing of worn out 
plaster dies is to use master dies or moulds of iron or steel, from which 
the real dies are made. A master die or mould is the cast or impression 
taken from a die with a tile in it. With dies thus made of both the 



308 BULLETIN ELEVEN 

upper and lower surface of the tile, it is only necessary to spread plaster 
on the face of the master die, fill the empty die shell and press the two 
together, instead of having to build up the empty die shell with blocks 
of wood and clay and to adjust a loose matrix in position each time. 
The use of master dies is to be strongly recommended, not only from 
the economy in labor, but because more accurate and better dies can 
be made. 



GEOLOGICAL SURVEY OF OHIO. 309 



CHAPTER VI. 

THE MANUFACTURE OF SPECIAL SHAPES AND 

ROOFING TERRA GOTTA* 

In no other line of structural clay ware manufacture is so great 
a variety of shapes required as in the roofing tile industry, excepting the 
manufacture of building terra cotta. In the latter, the use of stock 
patterns is very limited, and the manufacturer expects to make a com- 
plete set of moulds for each separate job he undertakes. As all of the 
decorative work of a building in which terra cotta is used is usually 
executed in this material, the number of special moulds which are made 
to be used once only is extraordinarily large. 

While the body of any tiled roof is covered with stock tiles of one 
shape, there are nevertheless an endless variety of shapes to make for 
trimmings and for adjustments between different parts of a complex 
roof, and these have to be in various sizes and various pitches to fit the 
angle of the roofs. Then, too, the roofing tile manufacturer is called 
upon to cover towers of every conceivable size and outline, so that the 
outlay for dies and moulds represents an important part of his necessary 
investment and one which is never completed. As long as he is in the 
business, so long will his stock of moulds and dies grow. It is of course 
impossible to describe all of this ever changing medley of shapes and 
sizes. There are, however, certain kinds of fittings that are very com- 
monly needed and these will be taken up one by one. 

Hip and Valley Tiles* — The only style of roof which does not require 
either hip or valley tiles, or both, is the perfectly simple variety, com- 
posed of two rectangular planes intersecting at a straight ridge-line, 
and finished at the ends with gables. All other roofs must have tiles 
specially cut to fit the angle of the hips or the valleys. In most instances 
this cutting is done at the plant, while the tiles are still in the green con- 
dition. In rare instances, with soft tiles, especially of the shingle pat- 
tern, the burnt tiles are cut at the roof, as slate is done. 

It will be understood that where there is a hip or valley to fit with 
tiles, it has two sides and therefore requires '^right and left" hip or valley 
tiles. The number of lineal feet of hips a^d valleys that has to be cut 
in covering an average dwelling house roof runs into a hundred or more. 
Hence each roofing tile plant makes provision for executing this kind 
of work rapidly, though in some of the smaller plants the work is not 
done as cheaply as it could be by having the proper facilities. The 
work is charged for by the running foot, in addition to the usual cost 



310 BULLETIN ELEVEN 

per square for the tiles. The method pursued at the best equipped 
plants is to have a "laying out floor/' usually on the second floor of the 
building. The angle of the hip or valley is obtained from the plans 
furnished by the architect. All orders at modern roofing tile factories 
in this country are executed from plans for each separate job, and not 
by selling tiles by the square, or thousand, to be applied by the pur- 
chaser to suit himself. It is very unusual to sell from stock, unless for 
small and very simple orders. 

After obtaining the angle from the plans, a base line is struck on 
the laying out floor to represent the eave line of the building. The 
length of the rafter is then measured off at right angles to the base lin^, 
a nail or spike being driven into the floor at the apex or end of the rafter, 
and also at the point on the base line from which the rafter was measured. 

A protractor with its straight-edge set at the given angle is now 
moved along the base line, either to the right or left, as the case may 
be, to a point where a taut line fastened to the nail at the upper end 
of the rafter coincides with its straight edge. A nail is driven into 
the base line at this point, and a line is stretched from this point to the 
top of the rafter, high enough above the floor to allow tiles to slip in un- 
der it without touching or moving it. Taking tiles which have stiffened 
somewhat till they have reached the "leather-hard" condition, the 
cutter proceeds, beginning at the base line and the intersection of the 
hips, to lay up a section 'Of tile roof. Each tile is laid on the floor, as 
it would be on the roof, and under the stretched line. It will be found 
that the line will cut each tile in a different place, until after a number 
have been passed one is found which is cut in the same position as the 
first. This is known as a "repeat," and recurs on a certain number 
of courses, depending upon the angle. Sometimes the repeat will begin 
on the sixth course, and again it may not occur until the twentieth 
or even more. Of course the next tile succeeding the first "repeat" 
is a duplicate of the second tile, and so on until another "repeat" occurs. 
When a "repeat" is found, it matters not whether the hip or valley 
is forty or a hundred and forty feet long, it is only necessary to measure 
how many feet of the hip are covered by the distance from one repeat 
to the next, and then to divide this amount into the total length of the 
hip to be covered, and to cut the necessary number of sets of "repeats." 
The tiles are cut along the line by a sharp knife, and as they are taken 
up from the floor, they are numbered as to their position in the set, 
and marked "right" or "left" as the case may be. 

With one set of tiles properly cut for the angle as a pattern, it only 
becomes necessary to make from lath a set of angles which will coincide 
with the cuts on the pattern tiles. Then with a stock of leather-hard 
tiles and a thin-bladed case knife, the cutter can prepare and njimber 
the required number of pieces of each sort, for as many sets as are 
needed. In case hip tiles are being cut, the lower end of the tile only 



OBOLOGICAL SUEVEY OF OHIO. 



311 



is saved; if valley tiles, the upper end. It often happens, however, 
whe e there are hips and valleys in the same roof, that one cutting can 
be made to serve both, by saving each end of the cut tile. In this case 
they should be cut only part, way through, and bumed as one piece 
and then broken apart. 






Fig. 109 — 'Angle Frames for Cutting Hip and Valley Tiles. 

As before stated, some of the larger and more up-to-date firms 
have other and better means for doing this work. At the plant of the 
Detroit Roofing Tile Company, they employ an outfit shown in the 
following illustration: 



Fig. 110— Perspective View of Hip and Vallejf Cutting Table, Detroit Roofing 
Tile Company, Detroit, Mich. 

This table is made of planks, and is about thirty feet long. Ex- 
tending along the back side, shown clearly in the end view, is a guide 
rail, raised about fifteen inches from the table top. Directly parallel 
■ with this guide rail, and cutting through the table top for its entire 
length, is a narrow slot, through which a piano wire passes, with a weight 
attached to its lower end, and a wooden handle at its upper end. A 
number of one-inch by two-inch cleats are provided, shown under the 
tiles on the top view of the table. The slot in the table top represents 



312 



BULLETIN ELEVEN 



the axis of the hip or valley to be cut. The cleats are tacked onto the 
table top at the proper angle to represent the purlins of the roof. 

In operation, a string of green tiles is placed in proper position 
along and over the slot as though it were on the roof. Should the 
hip line be twenty-five feet long, the string of tiles is made of that length. 
The operator then gets up on a walk at the back edge of the table, and 
grasping the wire by its handle, lie raises the weight from the floor, 
thus bringing the wire under tension. He then proceeds to move along 
the walk, allowing the wire to drag along the edge of the guide rail from 
one end of the table to the other, cutting the tiles as it goes. After 
the tiles are once placed in position on the table, it only takes a minute 
or less to cut the entire lot. If cut by hand, as described earlier in 
this chapter, it would require an hour or two to do the same with much 
more likelihood of making errors. 

The cleats representing the purlins of the roof are changed from 
time to time, as the angle of the hip or valley may require. In cutting 
rights after lefts, the direction of the cleats is reversed. 








Fig. Ill— Table for "Closing" Hip and Vallev Tiles, Detroit Roofing Tile 

Company, Detroit, Mich. 

^Qoscd'^ Hip and Valley Tiles. — It very frequently happens that it 
is desirable to have the cut ends of hip and valley tiles closed to prevent 
the snow and rain from blowing back underneath the tiles. This work, 
as in the case of cutting ordinary hip and valley tiles, is charged for 
by the running foot. Before a hip or valley tile can be made with a 
closed end, it has to first be cut to the proper angle as though it were 
to be used in the regular way. The ends then may be closed by plates of 
clay welded on by hand, or by an arrangement for closing a large number 
at once. The Detroit Roofing Tile Company has in use a table of about 
the same dimensions as their cutting table; the top is solid and is pro- 
vided with a facing-board along one edge, which extends up at right 
angles to the top to a height of three or four inches, depending upon 
the tiles to be operated upon. 



GEOLOGICAL SURVEY OF OHIO. 313 

The tiles previously cut to the proper angle on the cutting table 
are placed in turn in their proper order upon the closing table, the cut 
end being placed against the back board, as shown in the illustration. 
The tiles are laid face up for hip tiles and face down for valley tiles. The 
operator then takes a scarfing tool and proceeds to roughen a strip of 
the face of the tiles about three-fourths of an inch wide next to the back- 
ing board. He then slushes the newly roughened surface with water or 
clay slip, to make the surface weld easily. A long strip or roll of clay 
of the proper temper is then placed against the backing board and brought 
into contact with the prepared ends of the tiles, and welded under pres- 
sure of the fingers. The entire table full of tiles is done at once, and as 
if it were a single tile. After smoothing up the work the operator care- 
fully cuts the backing strip between each two tiles, disengages them from 
each other, trims and smooths the lower surface of the joints; the tiles 
are then placed on pallets ready to go to the dryer. Each tile is given 
its designating number and letter, as well as the order number, so that 
it may be identified on its way through the plant and at the roof when 
ready for application. 

Much of this kind of work is still done in the slow and costly hand- 
mould process, in which moulds cut to the proper angle are used, upon 
which the tiles are placed one at a time and filled or closed by hand labor 
entirely. 

Ridg;e and Eave Tiles — Most tiles, such as the various forms 
of Spanish and interlocking, require a special starting tile at the eave 
line, and a finishing tile at the ridge, to make a proper appearing and 
a well fitting roof. Spanish tiles, for instance, if left open at the bottom, 
provide a series of holes or openings which are speedily utilized by birds, 
bats and vermin in which to build nests, and which also give rains a 
chance to beat in. 

In the Orient advantage has been taken of these closed eave tiles 
to apply decorations in the shape of fancy ends, or ''out looks." 

In our country, the closing of eave tiles has been treated as merely 
a business necessity, and no attention has been paid to using this feature 
for any decorative purpose, though rich ornamentation can well be 
used. The architects of this country have thus far overlooked this 
opportunity, but if they make a demand for fancy eave starters, which 
can at the same time be made to serve as snow guards, the manufactur- 
ers will surely meet it. 

The greater part of closed eave tiles are made either upon hand 
presses or the power pentagon press, using plaster dies. In some of the 
smaller plants, machine-made tiles are dropped into plaster moulds and 
the ends put in by hand, but this method is far too slow. 

The Cincinnati Roofing Tile and Terra Cotta Company, has devised 
an eave closer, as shown in Figure No. 115. It is nothing more than a 
small separate piece of tiling, made to insert under the hollow of the 



314 BULLETIN ELEVEN 



4 



Fig. 112— "Closed" Dip Tiles. 



r^ 



Fig. 113— "Closed" Valley Tiles. 



Fig. 114 — "Closed" Eave Tiles. 



Fig. 115 — Cincinnati Roofing Tile Company's Closure tor Eave Tiles. 



GEOLOGICAL SURVEY OF OHIO. 315 

eave tile, and tacked in position with nails. While this closer can be 
set back under the tile far enough to give a strong shadow line, its use 
cannot be recommended, on account of the method of fastening. It 
is nailed to an eave strip, which extends with the eave line and under 
the first row of tiles. It is only a matter of time until the nail heads 
rust or corrode away and the end piece falls out and is broken and the 
roof is left open. 

Ridge or "top" tiles are the same as regular tiles, except the upper 
half is flattened to a plane, which rests upon the sheathing boards, and 
is in turn covered by the cresting or ornamental finishing tiles. These 
flattened tiles leave no openings to be filled with cement, as would be 
necessary if ordinary tiles were used. In other patterns a flange is 
attached to the upper end of the tile (see Figure No. 116). 

These tiles, like the eave starters, are made largely by hand presses, 
but in some cases by the power presses. A press that is used on this 
class of work is that of the Illinois Supply and Construction Company, 
of St. Louis, Mo. (See Figure No. 72 for description.) The Raymond 
Perfection hand press has also been used largely on this class of work. 
(See Figure No. 120.) 

With shingle tiles, the cutting of hip and valley tiles is quite often 
done at the roof by the roofer, it not being much more trouble to cut 
them than it is to cut slate. Top and bottom tiles are, however, cut 
at the plant, the former being six inch by nine and one-half inches 
and the latter six inch by seven and one-half inches. These sizes are 
cut by the reel cutter, so that extra charge is not made for them. 

Hip Rolls and Oestingf* — To properly cover a roof and have 
all parts weather proof, it is necessary to make shaped pieces curved or 
otherwise to fit over the ridges and hips. These forms are called crest- 
ings or ridgings, and hip rolls. The forms of these coverings can be made 
very plain or highly ornamental, as shown in the following illustration: 

It will be seen that many of the cresting forms must be made to 
fit the pitch of the roof, while others will fit any angle or pitch. The 
same is true of the hip rolls. 

There are many forms of hip rolls that are made by hand in plaster 
moulds. Each plant, as a rule, has one man that models all new designs 
and then makes the working moulds for the pressers. 

The clay used in this pressing or ''terra cotta work" is usually 
specially prepared; that is, it is pugged by itself to a much softer con- 
dition than the regular clay for the machines, and in clays that have 
a high shrinkage it is very often diluted by ''grog" or "grit." This 
material is made of broken and cull burnt tiles and kiln waste, ground 
and screened to about the same fineness as the rest of the clay. The 
amount used is from twenty-five to fifty per cent. This mixture, 
after being thoroughly pugged, is carried or conveyed to the pressing 



BULLETIN ELEVEN 



floor, where it is stored in bins holding from one to two weeks' supply 
and kept well covered and frequently sprinkled with water to prevent 
drying out on the surface. 



Fig. 116" Ridge or "Top" Tiles. 

The operation of pressing in plaster moulds has been described 
before, and is substantially the same for wares of all sorts. A good 
presser will turn out in the neighborhood of 100 pieces of ordinary 
hip roll per day, but the more complicated ones take more time. It 
requires from six to twelve moulds to keep a presser busy. 



Fig. 117 — Section of Shingle Tile Roof Showing Top and Bottom Tiles in Place. 

The greater part of the hip rolls and crestings at the present time 
are made either on the drop power-press, or the various makes of hand- 
presses, and in most cases it will be found that plaster dies are giving the 
greatest satisfaction. In making hip rolls or crestings on the above 



GEOLOGICAL SURVEY OF OHIO. 



317 



presses, it ia necessary of course to have blanks of suitable size pre- 
pared by auger machines. 

The blank, or blanks, if two are used as is sometimes the case, 
are placed in the lower die, batted down by hand, and any parts needing 
extra clay are supplied. The lower die is then shoved into position 
under the upper die, the pressure made, and the die, with its contents, 
is pulled out on the sliding track. AH excess clay and adhering parts 
are cut away, a piaster saddle or form fitting the inside of the tile is 
placed in position, the die is turned over, or dumped, on its hinges, 
the hip roll coming out and resting on the plaster saddle. The form 
now goes to the finisher, who works it over, trims ofl parts that are not 
needed, smooths up the piece, and places it on a pallet or form to dry. 




Fig. 118— Crestings. 



An adjustable pitch-board upon which to dry crestings that havi 
to be given a certain angle, as in the well known "S" cresting, i 
shown in Figures 121 and 122. 



318 



BULLETIN ELEVEN 



It will be seen that there is a base frame of two-inch by four-inch 
stuff. The real pitch boards are of seven-eighths-inch by twelve-inch 
material, the two boards being hinged together on one edge, and one 
of the boards being hinged to the base frame. The free edge of the 
other board has iron attachments to it, which engage in notches cut 
in the base frame, or a cast-iron notched strip attached to it. Now, 














Fig. 119— Hip Rolls. 

standing the boards up in an inclined position, like a letter "A," the 
angle can be made sharper or wider by changing the distance apart 
on the base plate and it only takes a moment to make the change from 
one angle to another. It will be noted that there are one-inch by one- 
inch strips nailed on the pitch boards on which the lower ends of the 
cresting will be supported so that it will not slide down too far and be 
strained out of shape. Pitch boards made in this style are convenient 
from the fact that when not needed they can be let down flat, and stored 
away in a small space. 

Tapered Hip Rolls by Auget Maciiines* — Only one plant was found 
making this style of hip roll ,by power machinery, or, in other words, 
by a flow-die process. While this method is not at all new in the old 
world, it seems almost unknown in this country. 



GEOLOGICAL SURVEY OF OHIO. 319 

The Cincinnati Roofing Tile and Terra Cotta Company has for 
many years been making tapering hip rolls on their plunger machine 
by using a half-round die from ^htch the bar issues as a aemi-circular 
trough, having the proper thickness and with a cross-section the full size 
of the large end of the tile. Conical trough-shaped boxes or forms, 



the large end of which will just admit the clay bar aa it comes from the 
machine, are placed upon a low stand, or track, in front of the die, 
in such a position that they can be slid in, large end first, almost up to 
the die. The stream of clay being started, the operator holds one of 
the receiving boxes in position with one hand and guides the fiow of 
clay with the other. The stream is compressed by the tapering mould 
to a cone shape. The excess clay at the small end projects up above 
the form. The machine is then stopped, the tile is cut off at the die, 
and the entire form, with the tile, is handed to the trimmer, whose 
duty it is to trim off the excess clay along the sides at the small end, 



BULLETIN ELEVEN 



Fig. J21 — Adjustable Pitch Board tor Drying Crestings. 




Fig. 122— Details ot Pitch Board. 




Fig. 123— Cutting Table tor Handhng Half-Round Tile for Hip Rolls. 



GEOLOGICAL SURVEY OF OHIO. 



321 



cut the ends true with the form, punch the nail holes and place the 
piece on a pallet ready for the dryer. By having a half-dozen of the 
conical receiving forms, and two trimmers, it was possible to keep the 
machine in operation the most of the time. Three men and three boys 
would turn out from twelve hundred to fifteen hundred conical hip 
rolls per day. This method is practically only possible with a plunger 
machine; it would not be feasible with a continuous delivery. 

With the outfit shown in Figure 123, it is believed that the output 
could be more than doubled by using an auger machine and the 
same labor force. This would make hip rolls so cheap that they 
could be used largely on slate roofs in the place of the metal cresting 
and hip covering now usually employed. 





Fig. 124— Cutting Horse for Conical Hip Rolls. 

The cutting frame and track may be of any design, the main feature 
being that the form upon which the tile travels does not extend but a 
short distance beyond the last cutting wire. As the tile is cut, it is 
pushed along by the one following. After leaving the form it is held 
in position by the side lugs or tracks shown in the end section. This 
leaves the entire tile free and clear underneath so that a paddle or form, 
having its outside shaped like the inside of the desired tile, can be in- 
serted to remove it from the cutting table, and pass it on to the cutting 
horse for final trimming. The right angled triangles that come from 
the semi-cylindrical tile being made to fit down upon the conical shaped 
form are cut off by drawing the form and its charge over the wire on 
the form or horse once. Upon punching the nail holes, the hip roll is 
complete, ready for the dryer. By having a half dozen or more shapers 
or paddles, and a couple of cutting horses, the daily output could be 



21— G. B. 11. 



322 BULLETIN ELEVEN 

made to run up to two or three thousand per day without question. 
By using agood strong auger machine the clay could be run rather stiff 
to facilitate rapid handling of the tiles. 

In using the ordinary drop press, or hand press, for making crest- 
ings and the larger forms of hip rolls, it will be found that the daily out- 
put of one man and a helper will run about two hundred to three hundred 
per day of average size, and less for the larger and more complicated 
patterns. 

Hip Roll Starters, — The hiproll,like the regular tile, needs a "starter" 
or closed end tile at the lower end of the hip of the roof. More or less 
advantage has been taken of the opportunity to ornament the roof. 
An extra price is charged for fancy or ornamental hip ends, because in 
making them a complete regular hip roll is used, and the end is welded 
on extra, usually by hand in plaster molds. 




Fig. 125 — Hip ■'Starters' 



Fioiali. — A roof is not complete without some ornamental form 
of Bnishing piece at the junction of the ridge line with the hips, or the 
ridge line at the gables, or on the top of the towers. 

In this class of work the roofing tile manufacturer most closely 
approaches to the field of the terra eotta manufacturer. Here a real 
chance for decoration comes into play, and the modeler can show his 
skill and artistic ability in the designing and making of richly ornamented 
pieces, ranging in size from one font up to si.'^ or even eight feet high. 

In this class of work moulds are very seldom made, because archi- 
tects are so very prone to want variety. Not only will different archi- 
tects not use the same ornaments, but even the same architect will 
hardly use his own design in a second place. Also, it is scarcely ever 
that two towers of the same pitch or rafter length are designed, so that 
the tile manufacturer has learned from experience that to make moulds 
of all the work turned out would be a useless tying up of money. 

There are many simple finials that could be made and carried as 
stock finials, for the standard pitches and hip rolls, but even then, the 
customer is likely to want a different cresting from that used in combi- 
nation with the finial, and hence it Is scarcely profitable to try to carry 
stock. In the making of stock or ordinary finials, it will be found that' 
each plant is equipped with a large assortment of hip saddles, or minia- 
ture roofs upon which the finials are built. 



GEOLOGICAL SURVEY OF OHIO. 



323 




These hip saddles must be made up in many pitches to suit the 

varied orders that come in. It will be observed that it is made very 

simply, and at the same time light, for it must often be moved. This 

saddle is placed on a low work bench or table, with the hip end accessible. 

The modeler before sta^rting sees to it that he is provided with newly 

pressed hip rolls and cresting of the kind desired on the completed 

finials; he then takes a roll of clay and builds up the hip corners with a 

false support for the real hip roll as shown in the following cut. He then 

selects two hip rolls from his supply, 

places them on the newly made 

saddles of damp clay, which have 

been first covered with damp paper, 

in the position shown in the cut. He 

then takes a cresting of the desired 

size and style, and places it in the 

position shown. 
Fig. 126— A Plain Hip Saddle. xt 4. u 1 • xi. u „ 

^ ^ Next, he works m the * aprons 

which form the connecting piece between the two hip rolls, and be- 
tween the hip rolls and the cresting 
as shown in the cut of the completed 
finial (see Figure No. 128). The 
modeler is very careful to have the 
clay become firmly attached to the 
hip roll and cresting, so he often 
takes a pointed or wedge-shaped 
stick and works or knits the adjoin- 
ing parts together. ^'«- ' 27-First Stage of the Finial. 

After the "aprons'* are completed, the modeler builds up the neck 
for the finishing ball, which is to be added last of all. The neck is modeled 
onto the hip rolls and cresting in coil fashion; that is, he builds it up, a 
ring at a time, until of sufiicient height. If a ball is to be added, it will 
first be hand-pressed in a two-piece plaster mould, then taken from the 
mould, and carefully placed on the neck previously prepared to receive 
it, the modeler being very careful to see that it is firmly attached. 

The saddle carrying the finial is 
then set aside, and the work is 
allowed partially to dry before the 
smoothing and finishing takes place. 
Finally, it is carefully placed upon 
the cresting end and allowed to dry. 
The number of finials that a good 
modeler will turn out will range from 
five to twelve per day, depending on 
Fig. 128— Completed Finial. the size and style. 





324 BULLETIN ELEVEN 

Tower Finials. — In the making of round tower finials, if of the 
plain type, the work can be accomplished largely by a sweep revolving 
on a vertical axis. This was seen in use at the plant of the Celadon 
Terra Cotta Company, at Ottawa, 111., a number of years ago, 

A permanent table was erected about six by six feet; in the center 
of this table a trap door opening downward, about one foot square, waa 



arranged (sec Figure 132). Through this trap door was a hole, through 
which a three-fourths inch gas pipe was run to a step in the floor and 
through a hole vertically above in the ceiling. This pipe represented 
the center axis of the iinial, and served as a pivot for the sweep, or 
wooden shoe, which was carefully cut to the desired size and outline 
of the required finial. 

.\ piece of sheet iron, forming a band around the gas pipe at the 
upper end of the shoe, steadied it at the top. A one-by-four-by-twelve- 
inch sliding strip was nailed at right angles to the main shoe to act as 
a guide or support at the bottom. 

With the shoe in place, the modeler began to build up a central 
core of soft clay. This core was built out following the outline of the 
sweep at a distance equal to the desired thickness of the finial. This is 
clearly shown in the cut. After the core was complete, it was carefully 
covered with water-soaked newspaj)era. These papers were to act as 
a parting line between the clay of the core and the [lermanent exterior 
layer. 

The work of building up the real finial began at this point, being 
added layer by layer, occasionally using the sweep to true up the work. 



GEOLOGICAL SUHVEY OF OHIO. 325 

When all had been completed, the shoe was removed, the gas pipe 
takon out through the top, and the hole in the finial ball filled with clay. 
When the day had hardened to the proper set, the trap door in the table 



Fig. 130— Modelers at Work ai National Roofing Tile Company. 



was opened, and the core was dug out by hand, the newspapers acting 
as the division line. The hollow linial was then removed from the table, 
and, after turning over, was dried. For making large finials this outfit 
proved very satisfactory. 

Graduated or Tower Tiles. — In the covering of pyramidal, con- 
ical or dome-shaped tower roofs, it becomes necessary to make special 
tiles to conforni to the converging lines of the tower. These special 
tiles are known as graduated tiles; they are graduated in the sense that 
they start with full-sized tile at the eave line of the tower, and then 
become narrower, smaller and smaller with the diminishing circumfer- 
ence of each course, until they come to a common center at the top of 
the tower, or near enough so that the apron of the finial will cover them. 

When an order calling for tower tiles is received, the foreman in 
charge of the special or terra cotta department carefully scales the plans 
of the tower, obtaining the length of the rafter and the diameter at the 
base. He then computes the circumference at the base in inches, and 
then divides the weather or exposed width of his full-sized tile into this 
circumference. If it comes out in an even number of courres around the 
tower, his next work is to go to the laying-out floor, which is usually 



326 BULLETIN ELEVEN 

marked off m foot lines. If it comes out in uneven or fractional tile8, 
as is usually the case, he then makes use of what is known in the trade 
as a "closer" course — i. e., the extra space is either filled in with smaller 




^ 



Fig. 131— Finials. 

or wider tiles, as the case may require. Where smaller tiles are needed 
to complete the circle, it is usual to start with some other tiles in the 
first course than the regular full-sized tiles; i. e., one or more tiles from 



GEOLOGICAL SURVEY OF OHIO. 



327 



the third or fourth course may be used in the first. Thus, with a little 
care it is possible to make the courses come out even for any tower. 

Figures 135 and 136 represent a simple outfit used in laying out 
tower tiles, Spanish tower tiles in particular. 




Fig. 132— Tower Finial Table. 

A represents a block with two hooks attached to its top side. These 
hooks are spaced the exact distance apart as the width of the weather 
surface of a full-sized tile. The block is fastened to the floor so that the 
hooks are exactly even with the foot line on the floor. The part B is 




Fig. 133— Tools Commonly Used by Clay Modelers. 

then fastened to the floor, on a line perpendicular to the center of a line 
drawn between the two hooks on Block A, and so that its hook stands 
at a distance equal to the length of the rafter of the tower. A line is 
now fastened to one hook at the base block, A, passed around the top 
hook and back to the second base hook, where it is fastened after draw- 
ing taut. 

The rate at which the tiles diminish in width is quite different. The 
tiles made for a ten-foot tower cannot be used on a twcntj'-five foot 
tower, and vice versa. Hence, moulds or di?s must be made for each. 
This is true of nearly every different sized tower. Occasionally the 



328 BULLETIN ELEVEN 

tiles from fourteen-foot towers can be shifted to one of fifteen or six- 
teen feet. This is more easily done with Spanish tiles than with inter- 
locking. In the interlocking tiles one has but very little play in the 
locks of the tiles in which the width can he swell, d or diminished. 



Fig. 134 — Tower Covered with Graduated Spanish Tiles, 

In the making of the tower tiles it will be found that the older 
plants are equipped with a full set of dies (piaster) for rafters of ten, 
twelve, fourteen feet, etc. These dies are for the most part worked on 




Fig. 135 — Floor Hooks Used in Laying Out Tower Tiles. 



GEOLOGICAL SURVEY OP OHIO. 



329 



hand presses. The extremely small tiles at the top are more often made 
by hand in plaster moulds. 

On towers with twenty-five or thirty-foot rafters, where the tiles 
become extremely small and slender, the expedient of making double 
or quadruple tiles of the small ones is followed at times. Again, when 
two-thirds of the height of the tower has been covered, every other 
course will often be "jumped out;" that is, one tile takes the place of 
two, in order to reduce the number of slender pieces. However, this 
is a matter to be settled in each particular case and no law can be laid 
down. 




Fig. 136 — Perspective View of Method o£ Laying Out Tower Tiles. 



Rake or Gable Tile?. — It would tie useless to attempt to enumerate 
and describe the endless variety of special tiles and shapes that the 
roofing tile manufacturer is called upon to produce, or sees that he 
must make in order to properly cover a roof. 

Jn the regular tiles it is necessary to make rake or gable tiles in 
rights and lefts, to complete or close the roof at the gables of a building. 
In interlocking tiles, there are four different rake tiles — full right and 
left rake, and a half-right and half-left rake. These tiles are nothing 
more than the regular tiles with the side provided with a wing or lip 
which comes down about three inches over the facing of the gable. 



11 



Fig. 137— Spanish Tower Tiles. 

Miter Tiles.— It very frequently happens" that dormer window 
cheeks or sides are covered with tiles, and when such is the case it 

becomes necessary to provide a finish at the angles or corners. This 
is done by mitering two tiles together as one. Thus the courses of tiles 
run completely around the dormer and at the same time form a cover- 
ing for the c 



BULLETIN ELEVEN 



Hitered Hip and Valley Tiles. — With shingle tiles it is possible 
to make them fit in the valleys and over hips of roofs, thus doing away 



Fig 138— Mitered Valley Tiles. 

with exposed metal flashing. These rnitercd hip and valley tiles can 
be made on presses, but are most often made by hand in plaster moulds. 

Ventilator Tiles. — In some instances, where there is much smoke 
or steam, as in foundries and workshops, it is desirable to have some 
means of ventilation in the roof. This situation has been met by the 
roofing tile manufacturers very nicely by making ventilators of the 
cresting tiles. The making of these ventilator tiles is hand work; that 
is, they are pressed by hand in plaster moulds. Very often, however, 
thej' are made by using a regular cresting, and modeling the ventilator 
opening and hood onto it by hand, without any mould whatever. 

Deck Vlouliins or Coping Tiles. — In addition to the ordinary 
cresting, a line of deck mouldings or wall copings are commonly made. 
The trade in the latter is light, because wall copings are extensively 
furnished by sewer-pipe makers, in much heavier cross sections than 
the tile maker would regularly produce. 

Curvilinear Tiles. — For dome-shaped roofs, or domes of towers, 
tiles of the regular pattern, except that they are made with a convex, 
outer surface, are produced. Similar curved tiles, though concave, 
are required for pagoda and Moorish towers. The curvature extends 
lengthwise of the tiles. In making these tiles, plaster moulds having 
the proper curvature are used. Each dome is a special problem of 



GEOLOGICAL SURVEY OF OHIO. 331 

itself and requires a complete set of moulds, which, as a rule, are not 
used for any other job. 

Other Curved Tiles. — Very often in covering a curved section of 
roof, known as an "eyebrow," it becomes necessary to construct special 
tiles of extra width to allow for the increased eave line of the "eyebrow." 
These tiles are of the same pattern as those made on the regular ma- 
chines, except that they are somewhat wider, and on the underlap side 
the rib is made higher to prevent the water from overflowing. These 
tiles are all made by hand in plaster moulds, the number required being 
small, and the size and curvature of the "eyebrow" to be covered hardly 
ever being alike. 

Glass Tfks* — There is no roof so well adapted to admitting light 
without the use of sky-lights as the tile roof. For a number of years 
back, a glass tile has been made, of exactly the same pattern as the 
clay tile. In train sheds, shops and factories where it is desired to 
have overhead light, all that is necessary is to insert glass tiles, either 
singly or in units, along with the regular clay tiles; thus the light can 
be admitted at any point and in areas of any magnitude. The areas 
can also be changed from time to time, if necessary. 

There is no other way that light can be so cheaply introduced in 
a roof as by the use of glass tiles, the economy being chiefly due to the 
fact that the first cost is the only cost. The amount of light trans- 
mitted by the corrugated surface of a tile is far greater than what could 
be transmitted by a plain glass pane. Another advantage is that the lines 
of the roof are not destroyed by unsightly sky-lights of the ordinary 
pattern. 



BULLETIN ELEVEN 






£^ 



^¥\ 



Fig. 139 — Ventilator and Special Forms of Ridge Tiles. 



GEOLOGICAL SUBVEY OF OHIO. 333 



CHAPTER Vn. 

THE DRYING OF RCX)FING TILES- 

The drying of a soft, plastic and easily deformable clay ware is 
the first step in converting it into a hard and durable substance. It 
is a process in which much skill and knowledge of ph3'sical laws may 
be employed, and also one in which results are constantly gotten with 
little or no such knowledge. From the fact that the atmosphere is 
the medium by which the water of the clay is carried off in vapor form, 
and that this atmosphere itself will supply the necessary heat to make 
the vaporization of the water possible, it follows that the drying out 
of wet clay is certain to occur, whether desired or not, unless actively 
guarded against. Also, this natural drying may under some conditions 
exceed in economy any of the artificial processes involving use of fuel, 
artificial movement of air, and arrangements for controlling hu- 
midity, etc. 

For these reasons a great variety of practices exist in the drying 
of all kinds of clay wares. The selection of the best method for any 
given case is not always an easy task. It involves a consideration 
of the following factors: 

(1). The nature of the clay ware to be dried. Whether its shape, 
size and thickness are such as favor drying safely and rapidly, or whether 
it is necessarily a difficult material to get through the process without 
defects or loss. 

(2). The peculiarities of the clay itself. Whether it has good 
strength, moderate shrinkage, and safe drying properties, or whether 
it is weak, or warps badly, cracks on the least exposure, etc. 

(3). The climatic conditions of the place where the drying is to 
be done. 

(4). The fuel supply. Of what character, whether easily ob- 
tainable and cheap, or the reverse. 

(5). The quality of labor available, whether intelligent and pains- 
taking, or ignorant and careless. 

(6). The value of the product and whether its price will permit 
expensive work being done upon it. 

In general, in tropical countries where rains are frequent and exces- 
sive, and the air humid, artificial drying is general, at least to the extent 
of providing covered structures for protection. In tropical or sub- 
tropical arid countries, like our Southwest, and the highlands of Mexico, 
the most favorable conditions for outside drying that exist anywhere 



334 BULLETIN ELEVEN 

are found. In such countries, the use of any fuel is very often unneces- 
sary. But even here the warei may require conditions not naturally 
afforded, and dryers heated by combustion of fuel may be necessary. 

In temperate zones where dry warm weather is not likely to be per- 
sistent for long periods, and where rain and frosts are certain to be 
frequent for one-third to one-half of the year, outside drying can only 
be depended upon for crude products and at favorable seasons. Nearly 
all high grade clay wares require artificial drying, and the best that can 
be done is to be able to take advantage of natural conditions when they 
happen to be favorable, but to be able to dry artificially when they 
are not. 

In the northern countries, no hopes can be cherished of dr)ang clay 
wares in the open, because of the little heat, and the humidity prevailing 
at times of high temperature. Frost prevents such work most of the 
time, and artificial- drying equipment is necessary. 

Since all of the roofing tile industry of the United States, unless a 
very small output among brick plants of the Southwest be considered, 
lies in the north temperate zone and in countries which experience sharp 
winter weather, and highly humid weather in the summer, the use of 
artificial dryers is necessary everywhere. The nature of the ware, the 
difficulty and expense of rapidly moving it, the perfection required in 
the product, and the price obtained, all require and justify the use of 
dryers where heat and air supply can be controlled. 

The physical principles upon which drying operations rest have 
been carefully studied and set forth in various works.* For this reason no 
space will be used in this connection, except for such comments as come 
up naturally in connection with the discussion of roofing tile dryers. 
The object of this chapter is to show the clay workers what kind of 
driers are in actual use in the roofing tile industry, and in what respects 
they do their work well, and in what direction changes and improve- 
ments are needed. 

KINDS OF ARTIFICIAL DRYERS. 

There are four types of artificial dryers: 

First* The Room Dryer. — This system seeks to maintain the atmos- 
pheric conditions of a warm dry summer day, in a room or building, 
in which the clay Wares are exposed either on the floors or on racks or 
shelves of some sort. The heat may be supplied in any way desired, 
except that it must not be from the waste gases of combustion from 
any source, as men must work in the dryer atmosphere with safety to 
health and in comfort. For the same reason, the temperatures are 

*E. Hausbrand, Drying by Means of Air and Steam. (Translated from 
the German.) 

R. H. Mmton, Trans. Am. Cer. Soc. Vol. VI, p. 269. 
D. T. Farnham. Trans. Am. Cer. Soc. Vol. XII, p. 392. 



GEOLOGICAL SURVEY OP OHIO. 335 

limited to 100** F., or slightly above, and usually do not exceed 85® F. 
This system is used almost exclusively for sewer pipe, terra cotta, glass 
pots, gas retorts, and all large refractory wares, and to a considerable 
extent for pottery of all kinds, especially the large thick-walled wares, 
such as sanitary goods. It has even been used for bricks of various 
sorts, but is not well suited to wares which must be dried rapidly and 
very cheaply. This type of dryer has its highest example in the sewer 
pipe factories, and for this reason is often called the sewer-pipe type. 

Second* The Hot Floor Dryer. — This system uses a fire-proof floor, 
usually of masonry, but sometimes of cement, or metal, the surface of 
which is maintained at as high a temperature as the clays will by any 
possibility stand. The ware is placed directly on this floor, and is 
dried by the heat taken up by actual contact with the floor, and from 
the air currents, which the floor heats and sets in motion. This system 
differs from the preceding in that but one method of heating is employed, 
viz., the hot floor, and the ware is dried on it, and not by the main- 
tenance of a gentle diffused heat permeating the rooms or buildings. 
This system originated in the fire brick business, and is almost wholly 
confined to that industry still. Onlj' occasional instances of its use 
for any other purpose are found. 

Third. The Periodic Chamber Dryer. — This system includes all 
dryers which use a chamber of limited size, in which high tempera- 
tures can be maintained, with rigid control of the air supply, humidity, 
etc. The type of this sort of dryer is the potter's hot-closet, but the peri- 
odic tunnel dryers, used for bricks, are also good illustrations of this 
method. It varies from the first type in the high temperatures and 
high humidity maintained, making the dryers untenable for men, and 
from the general use of artificial circulation to increase the rapidity of 
operation. 

Fourth. The G>ntinuous Dryer. — This system includes all dryers 
in which the ware to be dried is fed into the structure at frequent inter- 
vals, and taken out of another part of the structure at the same intervals. 
It involves the idea of progressive movement of the ware through a 
series of automatically varying conditions of temperature and humidity, 
and differs from the preceding only in this continuous and progressive 
character. In both, the temperature and air supply must be under 
close control. The same structure may, in some cases, be either as a 
chamber dryer, or a continuous dryer, according to its mode of opera- 
tion. In general, however, the difference in operation requires con- 
siderable difference in mode of distributing heat and air supplies. The 
type of this method of drying is the continuous tunnel brick dryers, 
and the method is very largely employed for bricks of all sorts. The 
method is now applied to some extent to sewer pipes, drain tiles, pot- 
tery, and roofing tiles. It is the most rapid and most economical of all 



336 BULLETIN ELEVEN 

methods for wares of suitable shapes and sizes and for clays which will 
stand the treatment, but very man}'^ clays will not stand the method 
at all. 

ROOM DRYERS. 

Nearly all roofing tile works use this method in part. Nearly all 
of the terra cotta pieces, such as the finials, large cresting and special 
shapes, modeled free-hand or pressed by hand in plaster moulds, are 
dried at the point where they are made. These products are not put 
into any special dryer, but are left in the open workroom, at least until 
they can be safely handled, when, in some few plants, they are moved 
into smaller, hotter rooms, and placed upon racks or slatted drying 
floors, under which are placed steam pipes. These auxiliary rooms are 
usually about ten by ten feet, and have a single deck only, and are used 
only to complete the drying of the ware after it has gotten beyond the 
slirinkage period, and to make it ready to go to the kiln. 

This system of drying is the typical one for this part of the prod- 
uct. In some of the later plants, where tunnel dryers are used, the terra 
cotta room is built over the cool end of the dryer. As the ware is made 
it is set along the floor (the roof of the tunnels made level) at a point 
where the temperature is best suited to the style or size of the piece in 
question. By this system it is possible to dry a considerable amount 
of ware without extra cost, there being sufficient radiated heat escaping 
from the tunnel at all times to do the drying of the shapes and terra 
cotta. There is a little inconvenience arising under this plan, from the 
fact that the clay for modeling the terra cotta must be elevated to get 
it to the terra cotta room on the dryer, and the finished ware must be 
brought down to the ground floor for loading in the kilns. The excel- 
lent drying space afforded and the waste heat here available more than 
offset the cost of elevating and lowering the clay and ware, which can 
be done very cheaply by conveyors or elevators. 

Another advantageous feature of the dryer above the tunnel is that 
the plant can be kept more compact and better arranged. The clay 
comes to the end of the dryer nearest the pugging machinery, and when 
manufactured and dried passes down at the end nearest the kilns, where 
it is needed. In some plants the terra cotta work is made in a room 
at right angles to the main machinery room, and when the ware is 
dry it has to pass out around the drier and be carried its full length 
before reaching the kiln yard. 

In the illustrations showing an outline plan of the United States 
Roofing Tile Company's dryer, the use made of their dryer top for a 
terra cotta molding and drying room can be seen. The same method 
was also found in use at the plant of the Western Roofing Tile Company. 
Coffeyville, Kansas. 



GEOLOGICAL SUBVEY OF OHIO. 337 

PERIODIC OR CHAMBER DRYERS. 

The preceding dryers have in both cases been used for the drying of 
the special tiles and roofing terra cotta, but not for the regular tiles 
which compose the bulk of the output of the plant. For the latter pur- 
poses the room dryer would be scarcely applicable, because of the slow 
drying which it is specially designed to give. Slow drying is neces- 
sarily correlated with small output. However, there were found two 
dryers for roofing tiles, which are almost as closely related to the room 
dryer as to the chamber dryer under which they are here classified. 

The Bennett Dryer* — This dryer was employed by the Bennett 
Roofing Tile Company, Baltimore, Md. It was the simplest dryer 
found in use. It consisted of permanent shelves, or racks, in a closed 
room. The tiles were pressed on a small pentagon press, caught on 
wooden pallets, then pallets and tiles were placed on a continuous 
belt elevator, which took them to the second floor, where they were 
removed by boys or men who took them to the shelves of the drying 
room. The rooms were about twelve by twenty feet, divided into 
narrow walkways between permanent built-in racks, having slatted 
shelving. The racks were about four feet wide, so that tiles were put 
in and taken out from both sides. The heat was supplied by steam 
pipes laid under the racks a couple of inches above the floor. The 
racks being slatted, the ascending currents of heated air were able to 
pass among the tiles more or less freely. 

This dryer was very similar to the finial or terra cotta dryers pre- 
viously described. It differed in the quantity of ware crowded into a small 
space and in the fact that the dryer was loaded, closed, heated by piping 
until the contents were dry, and then emptied. The room dryer always 
had ware in all stages at the same time, and its conditions permitted 
all parts of the process to go on safely together. The Bennett dryer 
dried a charge at a time, and had to be cooled down for drawing and 
recharging, and therefore is a periodic or chamber dryer. The Bennett 
dryer was defective in that no particular provision was made for venti- 
lation other than the natural leakage of any rough boarded room. The 
air in the dryer undoubtedly soon became fully saturated with moisture, 
and then drying would only take place as new and dry air leaked in to 
take the place of the water-laden atmosphere inside. By using venti- 
lator stacks or a fan, it would have been possible to have gotten much 
more work out of this amount of dryer space. The cost of loading and 
unloading this dryer was much too great. 

It should be understood, however, that in this particular case, the 
plant was not really run as a strictly business proposition. It was main- 
tained largely as a hobby by its owner, Mr. Bennett, whose major time 
was taken up by the cares of a large and successful white-ware pottery. 

22— G. B. 11. 



338 



BULLETIN ELEVEN 



The Gncinnati Dryer. — The dryer used by the Cincinnati Roofing 
Tile and Terra Cotta Company consisted of rooms fourteen by forty 
feet by about eight feet high. Figure No. 141 shows a side view and 
cross-section of one room. Along each side, and parallel with the floor, 
are spiked two by four inch cleats at intervals of about eight inches. 
These cleats extend the* full length of the room on each side, and act as 
the supports for the movable shelves tiiat are put in as the filling of the 
dryer progresses. The shelving is pine composed of plain seven-eighths 
inch by ten-inch boards. « 

It will be noticed that though the dryer room is ceiled, it has three 
ventilators which extend up above the real roof of the building. At 
the back of the dryer, at the left-hand end, is a six-inch steam pipe or 
"header," out of which, at intervals of eleven inches, one-inch pipes 
are taken. These pass along the floor of the dryer to the other end, 
where they empty into a smaller header, which drains into a steam trap. 
The floor of the dryer is perforated with auger holes, to admit air under 
the pipes. 





c 


=L 






















































r 








Fig. 141 — Dryer Used by the Cincinnati Roofing Tile and Terra Cotta Co. 

Cincinnati, O. 



The operation of this dryer is strictly periodic. The tiles are placed 
three-deep on a pallet. The pallets in turn are placed on a two-wheeled 
''buggy'' (Figure No. 101), and run down the hallway to the room that 
is to be filled. A runway for the buggy extends the entire length of 
the dryer room. The first stand or tier of portable shelving being in 
place, the pallets with their tiles are unloaded upon them as shown 
in the end views of dryer (Figure No. 141). When the entire first stand 
is filled, a new one is started by putting in boards, three incjhes in ad- 
vance of the front of the stand just filled (see side view in Figure No. 



GEOLOGICAL SURVEY OF OHIO. 339 

141). In order to keep the shelves from sagging down in the center* 
portable uprights are inserted between shelves, one above the other, 
as shown in the end view of the dryer. These uprights are eight inches 
by ten inches, with one-inch cleats nailed on both sides at each end to 
give it stability. Stand after stand is erected and filled until the entire 
length of the room is occupied. It takes from two to four days to fill 
a room. It is then closed by .sliding doors, steam is turned into the 
pipes, the dampers in the ventilators are partly opened, and the drying 
proceeds, using live steam at night and exhaust from the engine in the 
daytime. The drying out of a room full of tiles takes from six to fifteen 
days, depending on the conditions. After the tiles are dry, they are often 
allowed to remain in the dryers as storage rooms until needed for setting. 
The rooms each hold in the neighborhood of fifteen thousand tiles. In 
drawing, the door is opened, a temporary bench set up, and the tiles 
from the outside stand are taken down, beginning at the top, pallet by 
pallet. Each tile is then carefully looked over, and if true and perfect 
is placed on a pile from six to twelve deep on a pallet; set on a buggy and 
trucked to the kiln. 

This dryer is certainly a very crude and cumbersome affair. So 
far as can be seen, it has no advantages over other forms, and it cer- 
tainly has disadvantages. For drying a very tender clay, its action 
is slow and gentle and would probably avoid much cracking, but there 
are better types for this purpose. 

Its greatest disadvantage is in the great cost of time and labor 
in filling and emptying. It is necessary to put up and take down the 
entire shelf-and-stand equipment. If an auger machine were used 
to make the tiles, one man could not put up the stands fast enough 
to take care of the output, but the plunger machine used in this plant 
is of small capacity and the dryer has been evolved to work under these 
conditions. The construction is all cheap wood work and hence- per- 
ishable by fire or rot.* The rate of drying is exceedingly slow, very fre- 
quently taking twelve to fifteen days to get tiles ready for the kiln. The 
heating surface of the pipes is entirely too small for the amount of w^ork 
to be done, and the circulation of the air through the densely packed 
room is too sluggish. An exhaust fan system to increase the venti- 
lation would be a marked improvement, either with or without in- 
creased heating capacity. 

This type of dryer is not practical for any but small plants. A dryer 
after the Bennett plan, having fixed shelves, would prove more economi- 
cal to operate in the large way, and owing to the opener arrangement 
would be more rapid, provided proper facilities were made to heat 
and ventilate the rooms. 



♦Since this was written, it has been destroyed by fire. — [Ed.] 



340 BULLETIN ELEVEN 

The Huntingdon Dryer. — A periodic dryer of somewhat his/her type 
in construction and operation was found at the Huntington Roofing 
Tile Company. The tiles are here placed on steel pallets, which are 
loaded on rack cars, which are then run into the drying room. They 
pass through the dryer in from twelve to twenty hours, and are then 
unloaded, repiled on wooden pallets, and allowed to stand in racks 
in an open shed until air dry. This system is quite unusual. The 
dryer proper was designed by the Barron Dryer Company, of Chi- 
cago, III. It consists of a low rectangular room, high enough to 
hold the rack dryer cars; and filled with parallel tracks. Steam 
coils are placed under the car tracks at the outlet end of the dryer, 
extending back three or four ear-lengths, or about twenty-five feet. 
The heat is furnished by exhaust steam in the day time, and live 
steam at night. At the inlet end of the dryer is a large stack, 
which extends up twenty or more feet. The ears of tiles on entering 
pass directly under the stack, and thus come in contact with the escaping 
moisture-laden air from the cars farther down in the dryer. The 
cool green tiles often condense moisture on their surface before com- 
mencing to dry. The tiles receive the greatest amount of heat on 
reaching the zone over the steam coils. The dryer is provided with doors 



Fig. 142— Buggy of Dry Tiles on Way to the Kiln. 

at each end, and the ventilating stack is controlled by a damper, so 
that the flow of air through the dryer can be regulated. The dryer 
thus far described is about the ordinary tunnel dryer with the parti- 
tions left out. ]iut as used at Huntington, it is different from the usual 
operation of a tunnel dryer. The time that the tiles are in the dryer 
varies from ten to twenty-four hours. The tiles still show marked 
signs of color on the surface, from the remaining moisture, and are in 
the so-called "leather-hard" condition. The cars are then run out 
on to a transfer car, moved over to open rack sheds, and the tiles are 
transferred from the metal pallets which are one-eighth inch thick 
by about sixteen inches long. The tiles lie on these in single thickness 



GEOLOGICAL 8UBVEY OF OHIO. 341 

only, but are now stacked from twelve to twenty deep on other pallets 
in the shed, where they remain sometimes many days, jo at least until 
the tiles are air dry. The sheds therefore serve not merely as dryers, 
but also as storage for tiles ready for the kilns. For setting, they are 
loaded, still on their pallets, on to trucks and taken to the kiln. 

The advantages claimed by the company for this method are several: 
First J a much smaller number of cars and iron pallets are needed, which 
materially reduces their investment. Secondly, owing to the small 
kiln capacity, they would be obliged to run the plant frequently for 
short periods, whenever they had a kiln empty, but by their ample 
shed storage they can run the present plant continuously for a time, 
until everything is full, and then shut down for a considerable time, 
until the sheds are nearly depleted. They consider this more econom- 
ical than the other plan. 

There are, however, some stronger reasons why this method is 
locally a success. As stated elsewhere, this company has been running 
exclusively on flat shingles, and without doubt is turning out a greater 
per cent, of number-one goods than any other concern on this style of 
tiles. 

In studying the conditions under which they work, we must turn 
back to their raw material. They work two shales, one a fat plastic 
body which lends strength and good color; the other is a very sandy 
shale, which is used to control the shrinkage. The blending of these 
two shales is carefully watched. The grinding and screening is to one- 
sixteenth inch mesh. The clay is pugged rather softer than usual, as 
they have only small machines for making the shingles and cannot work 
the clay very stiff without breakdowns. The tiles come from the auger 
so soft that the pallets must be perfectly straight, or the tiles will be 
warped by the pallet. This soft condition of the clay permits the grains 
of hard shale to find water so that they slake or soften before the drying 
takes place. This permits the internal strains to adjust themselves. 
The drying proceeds slowly; only enough of the water is evaporated 
in the dryer proper to bring the tiles to a condition where they can be 
handled without marking. Thus very few if any drying strains have 
been developed in the tiles, and if there are any such, upon being placed 
in the oiKjn sheds, the extremely slow drying in piles allows them to 
readjust themselves. So that, when the tiles go to the kiln, they are in 
the best possible condition. 

This method of drying as a whole, while producing very good results 
in this plant, can not be recommended for general application. The 
cost of the extra handling is considerable, and we have no evidence that 
the clay mixture would not produce equally good straight tiles in as 
high proportion by rapid drying in an efllcient dryer as by this plan. We 
can only say that good results are secured by the present cumbersome 
and expensive process, made necessary by the lack of correlation of the 



342 BULLETIN ELEVEN 

making and burning departments. Another bad feature of the system 
ia that it can only be operated during the warm months. This, however, 
could be easily improved or overcome by having the sides closed by 
doors or canvas curtains, and with a few lines of steam pipe, or a little 
wast« heat from the kilns, the sheds could be kept at a temperature well 
above freezing during the winter months. There are some objections 
also to the dryer itself. The steam pipes under the floor are extremely 
hard to get at in order to make repairs. The draft or the circulation 
of air through the dryer is created entirely by the stack. Under favorable 
atmospheric conditions, the ventilation will be sufficient, but on warm 
damp days the draft will become very sluggish, and the drying in con- 
sequence will almost, if not entirely, cease. 

Another bad feature is that the interior space is one large open 
room, in which the natural liow of the hot air will be along the lines of 
least resistance. This most frequently is along the ceiling, and at times 
it crosses the dryer at various angles to the point in the vent stack having 
the best draft. If the space were divided into single or double track 
tunnels, the air currents would be much more under control. 

The Qoverport Dryer. — A similar dryer is in use at the Murray 
Roofing Tile Company. The tiles at this plant are made in the same 
manner as at Huntington. They are loaded on iron rack cars, and run 
into an eight track single room dryer about seventy feet long. The 
heat for this dryer is supplied from two sources: first, steam pipes placed 
on the floor, and second, a fan and steam- 
coil system, furnished by the Green Fuel 
Economizer Company, Matteawan, N. Y. 
The u.se of the fan tends to produce a bet- 
ter circulation, but the dryer is largely 
open to the same objections as the Hunt- 
ington dryer. There is no direct control 
of the movement of air through the room. 
The use of both steam pipes on the floor 
and a hot air fan system is unusual, and at 
first sight, might seem unnecessary. But 
the presence of the hot pipes all over 

.,- ,.., ^. ^ -. the floor insures circulation by con- 

Fig. 143— Steam Coils. ,,.,,, 

vection currents, and while the fan may 

be sending volumes of warm air into the dryer, it nmy be following 
lines of least resistance around or across the tops of the cars, and thus 
without the .lid of the piixss a poor result might be attained. The 
o[)en room is chiefly responsil>le for this, and if the space were cut up 
into tunnels, the double heating system would be less likely to be of use- 
One thing may be said of the large open room, viz., the mass of 
ware contained at once is great, and the proportion of ivalls and dead 
work to heat up and cool down with each charge is much reduced. The 



GEOLOGICAL SURVEY OF OHIO. 343 

ware is slower to dry in such a mass and is safer from cracking on that 
account. It is a method which might be considered with a tender clay, 
where it would be rejected for a strong, safe drying clay. 

CONTINUOUS DRYERS. 

• Tunnels Heated by Steam.— -This style of dryer is used in five of the 
roofing tile plants, a larger proportion than any other type. It is possi- 
ble that this large use is not due to any special superiority over other 
styles, but to the fact that it can be very easily adapted to plants of 
various sizes, and with less initial expense than the waste heat system. 
Continuous dryers are usuallj^ built in the form of single track tunnels, 
from eighty to one hundred and twenty feet long, and from three feet 
six inches to four feet six inches in width, to suit the cars. The matter 
of single or double tracks is not of much importance as far as the drying 
is concerned. There is less wall to keep hot in the double track tunnels. 
The real advantage of the double track tunnel is that it is easier cleaned 
and more accessible in case of a breakdown, or some other trouble with 
any of the cars. In cost of construction, it is a littje cheaper to build 
the roofs of single timnels than with double, when either brick arches 
or reinforced concrete is used as the cover. If brick arches are used, 
the rise of the arch gives a waste space above the tops of the cars, and 
the hot air, unless prevented by stoppings fitted in at intervals, will 
tend to pass along over the top without coming into much contact with 
the ware. Flat roof construction, either of book tiles, or blocks, or 
cement concrete, are all perfectly feasible, and free from the above dis- 
advantage. 

The length of the tunnels should depend on the particular clay to 
be dried; shorter for the easy quick drying clays, and longer for those 
more plastic and difficult to dry. It is very rarely that the dryer need 
be over one hundred and ten feet long, exclusive of the loading and 
unloading tracks at either end. These tracks as usually built are of 
two car lengths at the receiving end, and three or four at the unloading 
or cooling end. 

The outside walls are usually nine or thirteen inches thick and the 
inside or partition walls are four inches for single track and nine inches 
for the double track tunnels. The arch of the roof, if of brick, is usually 
from four to eight inches thick, and is coated with cement if to be ex- 
posed to the weather. If used as the floor of the terra cotta drying 
room, it is either made level with sand or cinders and then cemented, 
or a slatted board floor is laid over it. 

The heat necessary for these dryers is supplied by either live or ex- 
haust steam, or both at the same time. The heating system consists 
of a series of independent steam coil units arranged along a header in 
a compact group. These coils are contained in a metal hood or case. 



344 BULLETIN ELEVEN 

and the air is blown or sucked through the coils, coming into intimate 
contact with them. These heating coils are so cloee spaced, and the 
frictional resistance they offer to the passage of air is so great, that they 



Fig. 144 — Fan for Dryer. 

cannot be operated without power draft in some form. Fans are gen- 
erally used to pull the air in among and through the coils. The air takes 
up heat rapidly as it passes through, and is often too hot and is diluted 
with cold air at the fan so that a mixed and tempered air current of 
greater volume is obtained. The air is delivered to the tunnels through 
underground flues usually, which connect into the lower end of the dryer 
near the door. 

In some dryers of this type the hot air is all liberated at a single 
opening in each tunnel; in others it is liberated through smaller holes, 
at intervals of each two feet or so, back to a distance of twenty to thirty 
feet from the outlet end. The distance that these hot air vents in the 
floor can be carried back up the tunnel will depend very largely. upon 
the drying quality of the clay. ' The safer the clay, the farther toward 
the incoming end can the hot air be carried. Tender claj's do best when 
only one opening is made at the lower end. 

The fact that the steam coils are in independent sections admits of 
easy adjustment as to the quality of heat furnished. The source is also 
under control, as either exhaust sleam or steam direct from the boiler, 
or both, can be u^ed at the same time by admitting them into separate 
sections of coila. This feature, in connection with regulation of the speed 



GEOLOGICAL SUBVEY OF OHIO. 345 

of the fan, gives the operator almost perfect control of the drying con- 
ditions. It is common at the upper end of the dryer, where the moisture- 
laden air is discharged, to have a small auxiliary fan to assist in moving 
the wet air out of the dryer. In some cases ventilators are used, but 
these are not so satisfactory as the small fans. There seems to be no 
first choice as to the selection of fans. The following firms have each 
installed one system in a roofing tile plant: The American Blower Com- 
pany, Detroit, Mich.; The New York Blower Company, Bucyrus, Ohio; 
The Green Fuel Economizer Company, Matteawan, N. Y.; The Buffalo 
Forge Company, Buffalo, N. Y.; The Garden City Fan Company and 
The Sturtevant Company, Boston, Mass. 

The Parkersburg: Dryer. — The equipment for this dryer was fur- 
nished by the New York Blower Company. The above sketch was 
taken largely from their drawings. The terra cotta room above the 
tunnels was added by the owners. 

It will be seen that this dryer is of the single track type, the tun- 
nels being forty-four inches wude, six feet high and eighty feet long. 
The large exhaust flue at the upper end is fifty-four inches by fifty-four 
inches, and is provided with a low stack at one end for ventilation. 
In most cases it would be better to have an exhaust fan at the stack 
end, but in this particular case the tunnels are comparatively short, 
and the fan is only lightly loaded, so no trouble is experienced from 
sluggishness on the part of the dryer. 

The hot air ducts under the floor of each tunnel are eighteen inches 
by twenty-four inches at the intake, and taper up to about six inches 
by eighteen inches at the inner end, which is about twenty-five feet from 
the main flue. The latter, leading from the fan to the dryer, is forty-one 
inches by forty-one and one-half inches, the bottom rising gradually 
until it is only about twenty-four inches deep at the tunnel furthest 
from the fan. 

The fan is a regular ten-foot three-quarter housing, bottom dis- 
charge steel fan, the wheel of which is six feet in diameter by three and 
one-half feet face. The power necessary to operate the fan is furnished 
by a small twelve horse power horizontal slide-valve engine, made by 
the company that made the fan. 

The heater for this outfit consists of eight independent sections of 
steam coil. During the daytime exhaust steam from the engine operating 
the plant is used, being brought to the dryer through a five-inch asbestos- 
covered line. The exhaust from the small fan engine is also turned into 
the heater, so that very little loss of steam takes place. At night the 
heater is supplied by a three and one-half inch live steam line direct 
from the boiler. The usual time of dr3^ing in this dryer is twelve 
hours, although ten hours have been found sufficient. 



BULLETIN ELEVEN 





or 



Fig. 145— Plan of Dryer ; 



United States Roofing Tile Company, Parkersburg, 
W. Va. 



GEOLOGICAL SURVEY OF OHIO. 347 

While there are roofing tile plants with dryers of much larger size 
than the above, they are the same in principle. About the only objec- 
tion to this type of dryer is that during about one-half of the time it is 
necessary to furnish live steam to the coils. The engine of the plant 
is not in operation more than ten hours, so that a boiler must be kept 
in commission for no other purpose than to furnish steam to the coils 
and fan engine. 

There are many points in favor of this type of dryer: 

First, It is suited to roofing tile plants of moderate size, where 
there are not sufficient kilns being burned to give a steady supply of 
waste heat. 

Second, Its supply of heat is under perfect control — by opening 
or closing steam valves it can be increased or decreased at will. 

Third. The rapidity of the process is favorable to the avoidance 
of scum. 

Fourth, The economy of the dryer, if worked to its capacity, is 
very great. If worked to only a half or a quarter of its capacity, how- 
ever, the loss of heat by unsaturated gases escaping is very high. 

Fifth, The dryer is substantially independent of outside weather 
conditions, either for temperature or draft. 

Sixth, The system is elastic — by building more tunnels, adding a 
few more coils of heating pipe and speeding up the fan, a considerable 
increase in output can be secured at small cost if the original installa- 
tion was at all generously designed. 

After the dryer is once filled, and the work is properly started, it 
will be found that the cars entering the dryer pass at once into a warm, 
moist atmosphere, where the tiles warm up without starting to dry. 
After a car or two has been pulled out at the lower end, and the car of 
green tiles is moved down into the dryer a couple of lengths, the drying 
commences, and from time to time as it moves forward, it encounters 
constantly hotter, dryer air, until it passes out at the lower end, with 
the tiles perfectly dry and hot, ready for the kiln. 

The tunnel dryer using steam is and will be the One most largely 
used in roofing tile plants. It cannot be claimed as the best in economy 
of fuel, but its convenience and freedom from dependence on the kilns 
for heat make it .more popular. The fuel cost of drying is not a serious 
item in the roofing tile business anyway, and convenience is very apt 
to outrank it, with most manufacturers. 

Tunnels Heated by Furnaces. — This form of dryer, originally 
brought out as a patent by Sharer, and at one time extensively used, 
has given place largely in later years to others which derive their heat, 
in part at least, from the waste heat of engine rooms or kilns. Only 
one plant, that of the National Roofing Tile Company, Lima, Ohio, 
was found using a furnace-heated dryer. This dryer contains thirty 
single track tunnels, sixty-seven feet long, and about three feet wide 



348 BULLETIN ELEVEN 

and six feet high, each. The method of applying the heat differs from 
the usual Sharer dryer type, in that the flues under the floor are at 
right angles to the tunnels, instead of coinciding with their length- 
wise axis, as usual. The furnaces are built on both sides of the dryer, 
alternating with each other; i. e., the furnaces on the right-hand side 
deliver into flues, which pass under the floor to chimneys at the 
left-hand side, and vice versa. Thus a furnace and a chimney alternate 
along both side-walls. The idea of having the furnaces alternate in di- 
rection was to equalize the temperature from side to side of the dryer. 

The furnaces are of the common flat-grate type; the dimensions 
of each are about eighteen by thirty-six inches. When this dryer was 
first installed, it was gas-fired, but as gas became more expensive, 
resort was had to coal. The air for ventilation is let in on the floor level 
at the outlet end. The escape is through numerous vent pipes or 
stacks in the roof. 

In firing the dryer under normal conditions, the furnaces nearest 
the outlet end are fired much harder, or at shorter intervals, than those 
at the inlet end, in order to adjust the temperature to the continuous 
dryer principle, and not have the green tile entering at once with an 
extremely hot, dry atmosphere. The use of small individual stacks all 
over the roof instead of the single delivery at the inlet end is contrary 
to the continuous principle, and resembles the typical periodic dryers 
for bricks. The dryer is therefore not true to either type, but in opera- 
tion most nearly resembles the continuous type. 

The advantages of this method of heating a dryer are fev.- , if any, 
for the roofing tile industry, while the disadvantages are very apparent. 
In the first place, the cost of operation is ver}'^ high. The consumption 
of fuel takes place under yery wasteful conditions, and at the same 
time requires the attention of one man, day and night. The propor- 
tion of the heat generated which finds its way up through the fire-brick 
floor and performs any useful work in passing vertically upwards from 
the floor to the roof and out, is very small indeed — probably not ten 
per cent. The largest piirt of the heat passes out of the stacks at the ends 
of the flues, without ever entering the dryer at all, and what docs enter 
the dryer is not brought into contact with the ware for a long enough 
time. 

The control of the temperature is not at all close. The tunnels 
along the sides and over the furnaces receive much more heat than the 
central ones. There is no means of regulating this difference. 

The provision for admitting and controlling the air in this dryer 
is also poor. The low vent-stacks furnish but a slow circulation, and 
as the air is admitted on the floor, and not under it, and all at one end, 
the opposite end is nearly devoid of draft, which causes the deposition 
of dew on the tiles, and tends to bring out whitewash from the soluble 
salts in the clav. 



GEOLOGICAL SURVEY OF OHIO. 349 

There is still another feature not to be overlooked, viz., the flues 
are very apt to become choked or clogged up with soot, when the firing 
is done with coal. Even though they may not become so choked as 
to stop operations, they will l)ecome coated with layers of soot, which 
is an excellent non-conductor. Radiation through this soot layer 
is verj'' slow, and the greater part of the heat passes up the chimney 
into the air. 

In any case, it certainly is poor economy to consume fuel for drying 
purposes when there is daily much more heat wasted around the kilns 
and exhaust steam from the engine than would be needed to do all 
such work. 

Tunnels^ Usingf Waste Heat from Kilns« — It is the usual plan in 
this country, after a kiln of clay wares has been burned off, to allow 
heat contained in the ware and kiln itself to escape or radiate into 
the air, without any attempt being made to utilize it. Hence the 
term "waste heat" has been applied to heat obtained from this source. 

While the use of waste heat for drying is the most economical 
in the sense that no new fuel is consumed to dry the ware, and should be 
everywhere used if possible, it is only recently used in America in any 
important way, and up to the present the roofing tile makers have 
been slow to adopt it. The limited use of this method can be explained. 
Many of the roofing tile plants are only of moderate size, having from 
two to four kilns; hence the supply of waste heat is not continuous, 
and other provision would have to be made to furnish heat, when there 
were no cooling kilns available. This is accomplished in some of the 
plants that are using waste Jieat, by having steam coils in connection 
with the waste heat system. At most clay plants, an auxiliary fur- 
nace, often of large size and considerable cost, is used to supply heat 
in connection with the fan system, when no hot kilns are available. 
The auxiliary furnaces, if constructed to heat the air indirectly, by radia- 
tion, are satisfactory as to quality of hot air produced, but are costly. 
If constructed so as to utilize the waste products of combustion, or 
direct heat, they are economical in fuel consumption, but scum the ware 
by sulphur fumes if there is the least chance. Hence, for wares which 
are sold on their looks, the direct heater is justly feared. The ne- 
cessit)'^ of constantly having to shift from waste heat to other heat 
and back again has no doubt held back the use of this system as much 
as any other one condition. 

The first cost is considerably over that of the steam system, and this 
has probably held some plants back in adopting the waste heat system. 
However, this reason should not stand in the way, for in the end any 
other system will exceed the waste heat system in cost of operation and 
maintenance. 

The equipment for a waste-heat dryer, as usually constructed, con- 
sists of either single or double track tunnels built on the same plans as 



* 



350 BULLETIN ELEVEN 

for steam drying. The underground flues in the tunnels and those 
from the dryer to the fan remain the same. The fan and engine will 
differ very little. They may bo furnished a little larger, and it is advisable 
to have the main shaft bearing of the fan water-cooled. A trunk flue, 
or tunnel, leading from the fan house to the kiln yard, with side branches 
reaching out to each kiln, must be constructed. This system of flues 
can either be underground or overhead, the former being the general 
practice. Only one plant was found using the overhead system. By 
referring to the illustration of the Western Roofing Tile Company 
(Figure 183), the large overhead flues, or ducts, can be seen leading 
from the kilns to the fan house. The heated air mav be taken from un- 
derneath the kiln by a cross-flue. This method is the best, because the 
air coming in at the top of the kiln or over the bags has to pass down 
through all of the ware before reaching the flue, thus accomplishing the 
most work. However, one drawback to this method has been experi- 
enced, viz., to find a damper that will hold tight, so that when the kiln 
is burning the gases of combustion will not be sucked through into the 
waste heat flues by the fan. These gases of combustion art?. quite likely 
to form whitewash or scum on the green tiles in the dryer. Also danger 
arises from their escaping into the factory workroom, thus making the 
air unhealthful for the men. 

There is no serious mechanical difficulty about making air-tight 
hot-air valves to stand temperatures exceeding 800 degrees centigrade, 
but it cannot be done with simple iron castings, for they will warp, 
crack, oxidize and get leaky. The best method is to use well-made, true 
fire-clay slabs, covering a hole in the flue. bottom. If iron is used it is 
best to depend on a hemispherical bell to cover the opening in the flue, 
and let this bell seat itself in an annular cast-iron ring filled with fine 
sand. If, when the valve is open, the bell is pulled up out of the path of 
the gases, it will not warp or crack, and can be used for a long time. 
The sand joint is tight enough for such work as is here under discussion. 

Another method of drawing the heat aut from a cooling kiln is 
through the wicket (door) by a portable gooseneck. Instead of having 
the waste heat flue lead back under the kiln bottom, it is carried to a 
point in front of the wicket, where it ends as a well hole, which is carried 
up to the yard level. A cast-iron manhole with a tight lid, such as is 
used for cistern tops, is used to cover the well hole. When a kiln has 
been burned off, and is ready to draw upon, a hole is worked through 
the lower part of the wicket, the lid to the manhole is removed, and the 
coupling is made between the two with the gooseneck. The latter is 
merely a heavy sheet-iron elbow, fifteen to twenty-four inches in diam- 
eter, with handles for lifting while hot. The joint between the gooseneck 
and flue is made tight with mud. After all available heat has been 
taken from the kiln, the gooseneck is removed, the lid put back in the 
manhole, and the kiln is entirely isolated from the drying system. 



GEOLOGICAL SURVEY OF OHIO. 351 

There is no possible chance for back draft into the waste-heat flues. The 
hole in the wicket for insertion of the gooseneck can best be pro\nded 
for by having a large drain tile or sewer pipe built in upon setting up 
the wicket. This is then stopped with bricks and mud daubing. On 
removal of these the balance of the wicket remains in a good, tight 
condition. 

With rectangular kilns, or round kilns having two doors, it is com- 
mon to keep the fire holes and crown hole closed, and admit the cold 
air through the door or wicket in the opposite end or side of the kiln, 
so that the air has to pass through all of the ware on its way through. 
This is a doubtful expedient, however, especially in the beginning, when 
the kiln is at its highest temperature. The admission of cold air through 
the wicket is very likely to chill and crack some ware. It is safer to 
take the air in, for a time at least, through the fire holes or crown. At 
the fan it will be found necessary to have a cold air inlet, whereby the 
hot air from the cooling kilns can be diluted to suit the needs of the 
dryer. 

The Gfovcport Dryer* — Where the heat is not sufficient from the 
cooling kilns, a system can be installed whereby a considerable portion 
of the heat can also be extracted from the combustion gases of the burn- 
ing kilns as well, without allowing the combustion gases themselves to 
enter the dryer. The idea is not new, but is very little used in the 
ceramic industry, and not at all in the roofing tile plants. A plant was 
installed in 1906 at the plant of the Columbus Clay Product Co., Grove- 
port, Ohio, by W. G. Worcester, in collaboration with W. D. Richard- 
son, of Columbus, Ohio. 

The system required two fans, one to create the draft for the kilns 
and to deliver the hot combustion gases to the heater, and the other 
to pull the waste heat from the cooling kilns or the heater, or both, 
and deliver it to the dryer. The system as installed at Groveport pro- 
vided a double set of flues from the fan house to the kilns. One flue 
handled the waste heat of cooling only, and its neighbor the gases of 
combustion. The waste heat was taken from the wicket of the cooling 
kiln by a gooseneck, and after passing through the flue entered the dryer 
fan, which delivered it direct into the tunnels of the dryer. 

The gases of combustion, upon reaching the kiln bottom, as they 
would under natural draft, passed into the smoke flue, which was directly 
underneath the waste-heat flue, being separated from it -only by a four- 
inch fire-brick arch. Some of the heat of the combustion gases was thus 
radiated through this arch all the time into the hot-air flue overhead, 
but the bulk of it passed on to the heater. 

This was a brick structure, resembling roughly a tubular boiler on a 
large scale. The hot combustion gases were delivered by the fan into 
the lower part of one end of the heater, and passed through six-inch 
iron horizontal gas pipes to the opposite end. They then were turned 



352 



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GEOLOGICAL SUBVEY OF OHIO. 353 

back through the upper half of the structure, through more six-inch 
piping, from whence they went to the fan, which was of the vertical 
discharge type, with a six-foot wheel. The space surrounding the six- 
inch iron pipes was also divided into two sections and connected to the 
dryer fan. Cold air was admitted into the space surrounding the iron 
pipes at the end where the combustion gases escape, and then passed- 
through the apparatus in reverse direction to that of the combustion 
gases. It passed out of the heater near where the hot combustion gases 
entered it, thus coming in contact with hotter pipes the further it traveled 
in the pipe system . The total travel in the heater for both air and com- 
bustion gases was about thirty-five feet, which was found sufficient to 
take the hottest gases from a burning kiln and cool them to a point 
where one could easily hold the hand in them at the discharge of the fan. 
This shows that the heat had been largely extracted from them, but it 
does not prove that much was actually effective in the dryer. 

In Figures 146 and 147 the waste-heat flue system has been left 
unshaded, and the lower or combustion product flue system has been 
shaded to enable the plan to be more easily understood. The success 
of the system is by no means bound up in this particular construction. 
The flues could have been built separately with equal ease, but it was 
thought that the placing of the hot combustion gases in the lower set 
of flues would not only be cheaper in construction, but would assist in 
preventing the loss of heat from the hot-air flues overhead. The fans 
were located close together with a view to driving both from the same 
shaft. 

While this system as constructed at Groveport was proved econom- 
ical as a whole, it developed several objectionable features. First, the 
metal pipes through which the combustion products were drawn were 
constantly contracting and expanding with temperature changes, and 
were pulling loose at their point of passage through the brick partition 
walls. Even with plastering the joints, using magnesia, asbestos and 
similar materials, the constant change of size and length was too much, 
and mixture of the two gas streams ensued. Second, the iron pipes 
were subject to constant attack from sulphuric acid in the combustion 
gases. Third, replacement of the metal parts would make the cost 
high and the shut down of the plant necessary while repairs were in pro- 
cess of installation. 

Resrenerative Hot Blast Stove Dryer. — The above faults could be 
largely or wholly overcome by the substitution of a regenerative fire-brick 
hot stove, such as is used by the iron blast furnaces. This plan would 
call for the use of two stoves, or possibly more, one of which would be 
in service heating the air that would be flowing through it, while the 
other would be taking up heat by the passage of the kiln gases through 

23— G. B. 11. 



BL'LI,ETIN ELKVBN 




GEOLOGICAL SURVEY OF OHIO. 355 

it. By valves, the direction of the gases could be shifted at proper in- 
tervals, and the cool stove reheated and the hot one used for the air 
supply for the dryer. There is. nothing about this plan which is not per- 
fectly feasible from the mechanical standpoint, and well worked out in 
the daily practice of the blast furnace. The novel feature consists in 
applying the idea to a ceramic instead of a metallurgical problem. The 
only difference of operation between the two places would lie in the lower 
temperature at which the stove would operate in the clay works. Using 
kiln combustion gases from any ordinary battery of kilns, the temper- 
ature would hardly exceed 500 or 600° C. after leaving the kiln and 
reaching the stove by a more or less lengthy underground flue. These 
gases would then be cooled to 200 or 300° C. in passing through the stove, 
before being discharged at the exit end. At this temperature range, 
500 to 200° C, there would be danger of sooting the surface of the 
checker-work of the stove, and if soot did deposit upon the checkers it 
would speedily defeat the purpose of the stove, as it is a powerful non- 
conductor. The stoves of the iron furnace are heated directly by the 
combustion of the waste gases of the furnace, and in each shift any soot 
deposited would become thoroughly burned out by the red-hot air flow- 
ing over it. 

The general travel of the combustion gases from the kilns would be 
through the main flue* D to the flues E, E, which in turn connect the 
chambers. A, A, of the stoves. As noted, the stoves are divided into 
three compartments. A, B and C, and so arranged that the gases would 
pass up through the checker work of ohamber A to the top of the stove, 
thence downward through chamber B, under the partition wall and up 
chamber C to the fan G (see small sketch). 

The draft fan, as noted, is placed upon a bridge between the stoves, 
and connected to each by suitable dampered flues. These flues in turn 
would be so constructed that when either stove was being drawn upon 
for heat, cold air would be admitted at the top and would pass down 
through chamber C, then up through B, and down A, thence out through 
flue F to the dryer fan and dryer. 

While there are many possible ways to arrange the stoves and their 
flue systems and connections, the one suggested is the most simple and 
obvious one. If three or more stoves were to be used, some rearrange- 
ment would be needed, but the changes would all be easy to make and 
operate. 

The strong argument in favor of the regenerative stove, for utilizing 
the waste combustion gases of burning kilns, lies in the fact that all parts 
of the stove coming in contact with the gases would be constructed of 
fire brick or tiles, thus preventing the destruction of metal parts as in 
the Groveport system. 

There is no reason why the life of the stoves should not be indefinite; 
thus the first cost would be practically the only one. The fan at the 



356 



BULLETIN ELEVEN 



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GEOLOGICAL SURVEY OF OHIO. 357 

exit ejid of the system would necessarily corrode from the sulphur of 
the kiln gases, but this would happen equally in any system where com- 
bustion gases are utilized, and it would be an item of minor importance 
in any case. It is hoped that this suggestion may be taken up by some 
clay works and tested. Its chances of success are best, of course, in a 
plant where a considerable number of large, kilns are in use, so that 
there would be at least one kiln available at all times whose waste gases 
would be coming off at a temperature of 1,000° or above, reducing the 
sooting problem to a minimum. 

The New Lexington Dryer.— This dryer (Figure 149) is the largest 
in any of the roofing tile plants of this country. The equipment was 
furnished by the New York Blower Company, Bucyrus, Ohio, whose 
drawings were largely used to make up the plans shown. 

It will be seen that this dryer is of the double track tunnel type. 
There are at present thirteen tunnels, or twenty-six tracks. Each 
tunnel is eight feet wide, six feet high and one hundred and sixteen feet 
long, holding about thirty two cars of standard make. The ducts under 
the tracks are eighteen inches wide, and twenty-one feet or three car- 
lengths long. At the main flue they are thirty-six* inches deep, and at the 
upper end twelve inches deep. The main cross duct is fifty inches by 
eighty inches, tapering to twenty-four inches by thirty-six inches at the 
ends. The main flue leading from the cross duct to the fan is eighty 
inches by ninety inches. The fan wheel itself is thirteen feet in diameter, 
with a six and one-half foot face, and it is driven by a forty horse power 
slide valve engine, direct connected. 

This dryer is provided with a set of steam coils in connection with 
the waste heat, so that the drying can be done by either system, although 
waste heat is the one mostly used. 

In Section AA it can be seen that between the fan and the steam 
coils there is an inclosed space provided with a damper. This damper, 
when down, shuts off the waste heat system, and when up it shuts 
off the steam coils. It can be operated so as to allow them both to 
furnish heat at the same time. In case cold air is needed for dilution, 
the coils l^eing shut off, the damper is lowered to a point where sufficient 
cold air is let in to temper the hot waste gases to the proper degree. 
The dryer is generally operated at about 140° F., though it often runs 
above this at the hot end. 

The main trunk tunnel, leading out to the kiln yard, is six feet 
four inches by eight feet, connecting to sixteen round down draft kilns, 
part of which are twenty-six feet in diameter and part thirty feet. 

Other Dryers.— The Ludowici-Celadon Company, at Alfred, N. Y., 
has a waste heat dryer of ten double track tunnels in use. The equip- 
ment in this case was furnished by the Buffalo Forge Company, of 
Buffalo, N. Y. The tunnels at this plant are only seventy feet long, 
the drying being accomplished in twenty-four hours. At the New 



BULLETIN ELEVEN 




,f--f--=l 



GEOLOGICAL SURVEY OF OHIO. 359 

Lexington plant of the same company, the ware is from thirty-five to 
forty-eight hours in passing through the dryer. The time of drying, 
however, is regulated by the clay in use. The Alfred Clay Company, 
of Alfred, N. Y., has a small waste heat dryer consisting of four single 
track tunnels eighty feet long. The fan at this plant was furnished by 
The Buffalo Forge Company, of Buffalo, N. Y. The ware was being 
dried in twenty-four hours. 

At the Western Roofing Tile Company, Coffeyville, Kan., the 
equipment for their waste heat drying system was furnished by the 
New York Blower Company, Bucyrus, Ohio. They use a small auxiliary 
furnace, fired by gas, to supply direct combustion products to carry 
them over times when no hot kilns are available. 

In the aboVe cut can be seen the waste heat fan and the gas engine 
for operating it at night. During the daytime the fan was run by a 
belt from the main line shaft as shown in the illustration. To the right 
of the fan can be seen a small furnace built of brick. The large pipe 
leading down to the furnace is the waste heat flue leading out to the 
kilns. 

Claims for waste heat dryers: 

First — That they will dry ware at less cost than any other style. 

Second — The first cost is practically the only cost, except for the 
small cost of operating the fan engine. 

Third — It makes a direct saving out of an otherwise total loss. 

Fourth — It increases the kiln capacity by cooling them off faster, 
so that they can be reused earlier. This point is well worth considering. 

Fifth — It gives better burns in the kilns, by carrying the heat more 
vigorously to the bottom at the conclusion of the firing. 

SUMMARY. 

The foregoing description of the dryers found in use among roofing 
tile makers brings home the lesson that it is unwise to condemn the 
equipment of any plant on purely academic grounds, until all of the 
local conditions are carefully considered. These conditions frequently 
explain, even if they do not wholly justify, the use of inefficient or poorly 
designed equipment. 

It is, of course, impossible to prescribe the best dryer for the roofing 
tile business. But we may go so far as to say: 

First — That for handling the terra cotta and trimmings, a simple 
room dryer, equipped with ample shelving or rack room, and with pro- 
vision for maintaining pleasant work-room temperatures at all times, 
is all that is needed. The source of this heat should be from the waste 
of other departments, either by building the room above the general 
dryer, or by use of exhaust steam piping. It is not usually economical 



360 BULLETIN ELEVEN 

to try to heat a work-room from waste heat of the kilns, unless the latter 
are located inside of a t-overed buiidin"; and the radiations of their ex- 
terior can be thus utilized. 



Second — As the source of heat for drying the regular output, the 
most convenient, elastic and positive arrangement, consistent with 
high fue! economy, is tlie use of the waste heat of cooling kilns as 
the main supply, employing the waste heat of the exhaust steam as the 
source when no kilns are available. The amount of fuel consumed 
purely for drying purposes would, with this equipment, be reduced to 
that necessary to run the fans, and supply such live steam at night as 
would be necessary in excess of the exhaust of the fan engine, and electric 
light engines when the latter are used. Such amounts would be small. 

It would be possible to equip the kilns so as to utilize the waste 
heat of the combustion products for drying purposes, but this heat 
could be used more economically and effectively for water smoking 
other kilns, etc., rather than for drying. The danger in using combus- 
tion products for water smoking purposes, or for direct use in drj'crs, 
lies in cooling these gases below their dew point, and thus depositing 
acid dew upon the wares and scumming them. 

Third— The form of dryer in which this most economical heat 
supply should be applied must depend on the clay. Where the latter 
is safe and easy drying, the tunnel sj'.'itcm, operated as a continuous 
dryer, with both forcing and suction fans, gives the finest results both 



GEOLOGICAL SUBVEY OF OHIO. 36I 

as to speed, quantity and freedom from scum. With clays more or less 
tender, departure from this type to any required degree must be made. 
Usually a periodic tunnel will handle a moderately tender clay. If 
not, a room equipped with tracks will perhaps answer. 

Fourth, In dealing with tender clays, the safety of the product 
is always first, and fuel economy secondary, and it is not to be expected 
that methods for tender clays will give any high-grade results as to fuel 
economy, for such methods involve small outlay, slow drying, liability 
to scumming, and extensive capacity in proportion to output, and 
hence expensive heat distribution and much heat loss. 

Fifth, The use of new fuel, burnt for drying purposes only, with 
no effort to apply the waste heat of engines or kilns, and especially by 
such methods as the indirect radiation of hot floors, with no positive 
provision for creating or distributing draft, represents the lowest grade 
of practice, and is utterly unjustified on any grounds. The clay cannot 
require such treatment, for it is severe on a tender clay, and any clay 
that would stand this would stand better methods. Economy of 
first cost cannot be urged, for the dryer is expensive to build. Economy 
of operation cannot be urged, for it is the most costly to operate. Sim- 
plicity cannot be urged, for it requires more labor and as much man- 
agement as a good dryer. In short, it represents only bad manage- 
ment and low intelligence. 

Sixth, The selection of a plan of drying involves the considera- 
tion of the system of handling the ware: (a) from the machines to the 
dryer; (b) in the dryer; and (c) from the dryer to the kiln for setting. 
The economy of the drying cannot be considered apart from the 
handling system. 

Seventh. The use of cars, or some sort of portable racks or pallets, 
rather than fixed racks or shelves, is consistent with even the tenderest 
clays, and should never be omitted. The extra handling alone in some 
roofing tile plants costs more than the whole drying ought to cost. 

DRYER CARS AND PALLETS* 

Pallets. — The nature of roofing tiles requires that they shall be 
well supported when first made or taken from the press, and this support 
must continue until the tiles are dry enough to handle. 

All roofing tiles, coming from either auger machine or presses, 
are far too soft or pliable to retain their shape without the use of a 
pallet or form. It is not only essential that tiles be supported, but 
they must have enough freedom of movement to allow for shrinkage 
while drying. . 

The choice of materials for use in constructing pallets has been given 
much consideration and experiment in the various roofing tile plants. 
So far, wooden pallets have, on the whole, proven the most satisfactory. 



362 



BULLETIN ELEVEN 



on account of their cheapness, lightness, and strength. They also 
offer good resistance to sudden blows or shocks, if suddenly dropped or 
roughly handled. Other materials, including heavy sheet iron, cast 
iron, slate, and wire mesh, have from time to time been used. Some 
of these are still in use to a small extent. 

Taking up first the pallets for fiat shingle tiles, the most simple 
form of all, we find in use at the greater part of the plants the plain 
lath or wooden pallet shown below. 




Fig. 151— Wooden Shingle Tile Pallet. 

This pallet is best made of white pine or poplar. The two end strips 
or tie-pieces are about one-half by one and one-half inches, while the 
main top slats, three or sometimes four in number, are from one inch 
to one and one-half inches wide by three-eighths inches thick. The 
length should suit the tile, with about one-half-inch surplus at each 
end, to permit the necessary play while placing on the rack cars. The 
whole pallet is securely nailed, and costs in the neighborhood of four 
or five cents. Hence with pallets sufficient for a three days' run, allow- 
ing an output of twelve thousand per day, it will be seen that there 
is a considerable investment represented. Their rapid rate of dete- 
rioration makes it very necessary to get the best. 

From time to time, a good straight slate of the proper size has 
been used, but it has been found very difficult to get straight ones, 
and the worst feature about them is the breakage which in a year's 
run is enormous. The high breakage makes them too expensive and 
their weight is objectionable. At the Huntington Roofing Tile Com- 
pany, it* was found that iron shingle pallets were being used. This 
pallet was six inches wide, about fifteen inches long and one-eighth-inch 
thick. Except as to weight, they make very serviceable pallets; they 
require very little space on the car or in storage, hold their shape well, 
and if bent can be straightened back again, so that their life is indef- 
inite. For * 'curvilinear'' tiles for domes, it is only necessary to have 
a number of them bent to the proper curve, and then put the tiles on 



GEOLOGICAL SUBVEY OF OHIO. 



363 



the same as though it were a straight pallet. While their first cost 
is a little above that of wooden pallets, their durability is very much 
better, and by keeping them protected with good metallic paint they 
will outlast the wood so much as to make their ultimate cost less than 
wood. 




Fig. 152— Interlocking Tile Pallet. 

Pallets for interlocking tiles are all practically of one style, viz., 
plain slatted wooden affairs, in various sizes to suit the tiles. With 
some designs of tiles, it becomes necessary to increase the thickness 
at certain points to support irregular parts of the surface and locks, 
but the main features of the pallets are not changed. 

It will be seen in Figure 152 that the interlocking tile pallet is 
only an enlarged form of the shingle tile pallet. The slats or cleats 
are usually one-half inch or five-eighths inch thick, and two inches 
wide. The material is either white pine or poplar, well seasoned and 
surfaced on both sides. 

During the days of the Chicago Roofing and Siding Tile Company, 
at Ottawa, 111., a pallet like the above was used, except that the end 
cleats were put on edgewise, so that they formed legs. The pallets, 
when loaded with tiles, could then be stacked one above the other for 
drying. Their dryer was that of the slatted-floor type, commonly used 
in sewer-pipe manufacture, and the pallets were trucked into the dryer 
on two-wheeled trucks, and set off on the floor ten to twelve courses 
high. Hence legs were necessary. For drying on cars or racks, the 
pallets shown in the illustration are of the proper style. 

The most trouble is experienced in providing a pallet for Spanish 
tiles which will not only hold the tiles true to their curves, but at the 
same time will allow them to shrink. The pallet shown in Figure 153 
has proved the most satisfactory of all. 

These pallets are very ingeniously constructed. They are made of a 
single base-board, about seven-eighths inch by twelve inches, cleated 
with two strips on the under side. On the left-hand upper side is nailed 
a strip of wood having a curve to correspond with the curvature of 



BULLETIN ELEVEN 



the tile at that point. On the right-hand side are two strips, the inner 
one being nailed fast to the base, the outer one loose or movable. It 
is necessary to have this 6ut«r strip movable to allow for the drying 




Fig. 153— Spanish TUe Pallet. 

shrinkage of the tile. In order to hold the movable strip in the proper 
position while putting the tiles on the pallet, the false block tn the right 
in Figure No. 153 is inserted, upon placing the pallet ready to be filled. 
After the tiles are placed on the pallet, usually three deep, the block 
is remo\-ed and the pallet with its load is ready for the dryer. In case the 
outer or movable block is made fast to the base-board, the tile will 
be spread or flattened out at that point. If not flattened, they will 
crack lengthwise of the tile. 

Metal pallets of this same general outline have been used, but it 
was found that they soon lost their shape, and, also, no provision could 
be made to allow for the shrinkage. Hence, many of the tiles wer^ 
spoiled in the drying. 

For Spanish tiles made on presses, it becomes necessary to con- 
struct a pallet which will allow for the head or heel locks of the tile. It 
will be seen in Figure 154 that this pallet is copied after the form 
used for shingle and interlocking tiles. The only real diSerence is that 
the right hand slat is made enough thicker than the others to hold the 
roll of the tiles at the proper level, and a slot or groove is cut crosswise 
of the pallet to provide depth for the heel lock. This slot is made about 
twice as wide as the lock lug, so that ample room is given for shrinkage. 

Each plant finds it necessary to have many other pallets than the 
ones used for the regular tiles. There are pallets for eave tiles, top or 
ridge tiles, mitre tiles, tower tiles and various other shapes, all of which 
must be provided for specially. The number of any one of these special 
forms is not very large, but the aggregate is very considerable. 

Dryer Cars. — The question of dryer cars has been worked over about 
as thoroughly as the matter of pallets. Natural selection has reduced 
the surviving types to about two forms, both of which are rack cars. 
On one, the cross racks or strips are movable or loose, while on the other 



GEOLOGICAL SURVEY OP OHIO. 365 

thej' are fixed. A rack dryer car, to meet the demands of a roofing tile 
plant, must be easily adjustable to suit the various spacings needed for 
the many sizes of tiles made. 



Fig. 154 — Pallet tor Press-made Spanish Tile. 

There are in use at the present time in the various roofing tile plants 
of the country about two thousand five hundred cars, the greater part of 
which have been made by standard car builders. Among them were the 
following First, The Cleveland Car Company, Cleveland, Ohio, having 
the largest number in use; second. The .Atlas Car Company, Cleveland, 
Ohio, with the next largest number in use; third, The Ohio Ceramic 
Engineering Company, Cleveland, Ohio; fourth, The American Clay 
Machinery Company, having cars in two plants. Two roofing tile 
plants have built or assembled their own cars. 

The average dryer car for roofing tile is of twenty-four inch gauge> 
the rack is thirty-six inches wide by seven feet long and a height over 
all of about six feet. 

The racks are divided cither into two or three sections. The num- 
ber of shelves that are put in a section depends on the tiles manufactured, 
most of the cars holding from one hundred and fifty to two hundred 
interlocking tiles, or two hundred and fifty to three hundred shingle 
tiles. 

The main truck of this car may be of any make. The uprights 
are of narrow channel iron, usually two inch, and are riveted to the 
truck, and secured by gusset plates as shown. At either side of the 
top, a longitudinal tie bar of iron fastens the uprights together, while 
at the ends it is usual to put on cross braces, as shown by the end view. 

Running across the car, from upright to upright, and riveted to 
the same, are one inch angle irons which act as brackets upon which 
the one inch wooden strips rest. These wooden strips are loose so that 
upon loading a car at the press, the strips on the side nearest the press 
are left out, thus allowing the placer to reach more easily the opposite 



366 



BULLETIN ELEVEN 



Side of the car with the pallets. When the further side of the car is 
filled, he puts in the strips on the near side and fills them. It is usual 
to have about three rows or tiers of pallets, running crosswise of the 
car, so that it would be difficult to reach through and put the further 
row in place. 





Fig. 155 — Three-Section Dryer Car, with Loose Racks. 



The objection to this style of rack system is that there are too 
many pieces to handle, not only at the press, but in the kiln. This 
point has been overcome by some in having two section cars with strips 
reaching the full length of tho car. The trouble in this case is that the 
strips cannot be taken out of the car without pulling them out from 
the end, which takes up much time. 

Probably the best style of rack car, where loose strips are used, 
has a rack containing loose sections, and has the strips reach half the 
length of the car. They can then be easily taken down, or put up, as 
occasion requires. 

Where a plant is running continuously on one style of tiles, a rack 
car can be devised, as has been done by the Ludowici-Celadon Company, 
at New Lexington, Ohio, which comes very near meeting all require- 
ments. In this car the strips are fixed. 

It will be observed that this car is constructed much like the one 
just described. The upright members are made of channel iron, well 
braced and riveted. Instead of the one inch angle irons being fastened 
to the uprights, and forming supports for wooden strips, they are carried 
by two inch channel irons extending lengthwuse of the car on either side. 

The one-inch angles are held in position by having a short section 
of pipe put under the top leg, to act as a spacer. The rivets which hold 
the angle pass through the pipe washers also, making a very solid, w^ell 



GEOLOGICAL SURVEY OF OHIO. 



367 



built car. The pallets are slid in on the one-inch angles, the first one 
being put in part way, then pushed over by the ones following. The 
pallets are put in four wide, filling the width of the car. 



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Fig. 156 — Two-Section Dryer Car with Fixed Racks. 

In the case of the car having loose slats, the tiles are placed cross- 
wise of the car, and hence at right angles to the flow of air in the dryer, 
while in the car having tight slats, the tiles are placed so that they are 
lengthwise of the car, hence the flow of air in the dryer passes length- 
wise of the tiles and not across them. Thia latter plan is probably the 
better, for the ends of the tiles are more able to stand unequal strain 
from sudden drying than the sides. 

The main objection to the car with fixed racks is the inability to 
adjust it to suit the various styles of tiles made about the plant. If 
sufficient cars can be supplied to handle all necessary varieties, it is 
much better to use fixed racks. The value of a dryer car will vary 
materially with the style and the kind of rack wanted, but a fair average 
price is about $20.00 each. 

In selecting a car the bracing and the rack construction should be 
well looked to. The axles should by all means be equipped with roller 
bearings and automatic oiling facilities. The roller bearings should be 
made of true, perfect cylinders or rollers. The kind that ar»3 sheared 
from rod iron or cast, as are used on the cheaper cars, are very unsatis- 
factory. The sheared roller is sure to be flattened at the ends, from 
the pressure of the shears in cutting, and hence they can not run easily. 
The boxing should be such that the oil cannot escape as soon as it becomes 
warm in the dryer. 

The entire car should be well coated with a good metallic paint, 
especially if the cars are to be used in a waste heat dryer, for the corrod- 
ing action of even diluted sulphuric acid while in the damp atmos- 
phere of the dryer is very severe on unprotected iron. 



368 BULLETIN ELEVEN 

It can be positively stated that roofing tile companies cannot make 
their own cars as cheaply, or as well, as the firms that are making cars 
all the time. In the first place, no ordinary clay works has the proper 



Fig. 157 — A Home-made Car. 

tools for doing the work. Their men are not skilled in such labor. A 
plant may be able to save a trifle on the first cost of the cars, but the 
loss comes in later in the short life and extra labor to use the car. In 
other words, every man to his trade, and always at it. 



GEOLOGICAL 8UBVEY OF OHIO. 



CHAPTER Vffl. 

SETTING OF ROOFING TILES. 

The first thing to consider in connection with the burning of a clay 
ware of any sort is the proper mode of placing the ware in the kiln so 
that each piece may receive the heat treatment necessary to develop 
its strength and color and at the same time not be damaged by sinking 
out of shape under its own weight. 

The process of placing is imiversally known as ''setting*' in the 
United States, and it is one of the most important things which a suc- 
cessful clayworker has to consider. The difference between expert set- 
ting and ordinary setting may easily make the difference l[)etween suc- 
cess and failure of a whole establishment. It is a place where crafts- 
manship counts very heavily in any clay working enterprise. The prob- 
lem of setting roofing tiles is more akin to that of setting terra cotta 
or pottery than it is to bricks, sewer pipes or other crude forms of ware. 
The distinction hinges on the question of tha ability of the ware to sus- 
tain weight. In the case of bricks or pipes the ware is self-supporting. 
Bricks, being of thick, heavy cross-section, are admirably designed to sup- 
port great weights, even when approaching viscosity by vitrification. 
Bricks are set twenty-five to thirty courses high, without any supports 
whatever when firing to vitrification. When firing only to good build- 
ing brick hardness, forty-five or even fifty courses are piled up without 
supports. This corresponds to a crushing pressure of from twenty-five 
to thirty-five pounds per square inch on the lower courses, owing to the 
uneven distribution of the load, and to the fact that all parts of the 
bricks are not carrying weight. This load must be borne not only by the 
dry bricks, but also when the bricks are softened by steaming in the 
water-smoking stage of burning and when softening from heat during 
vitrification. 

Sewer pipes are usually placed four or five tiers high, with about 
one-half of the above pressures, but their shape is less favorable for 
resisting pressure. 

In the case of wares of thin cross-section, like roofing tiles, it is im- 
possible to make the ware carry its own load after the manner of bricks, 
provided it is desired to develop any great amount of vitrification in 
the firing. Warpage and deformation are certain if the tiles are so 
placed that they are free to move and are called upon to bear any but 
trifling weights. Some forms of roofing tiles which are not vitrified can 
be treated more roughly than the average. 

24— G. B. 11. 



370 BULLETIN ELEVEN 

The methods employed in setting roofing tiles may be divided into 
three general classes: 

1st. Those using kiln blocks for supports. 
2d. Those using no supports. 
3d. Those using saggers. 

There were eight plants using the supports, and five plants were 
found using no supports. One plant, now defunct, had been using 
saggers. The plants not using supports are making porous or soft-burnt 
tiles only. 

SETTING WITH KILN BLOCKS. 

Blocks* — The blocks used for kiln furniture in the roofing tile 
business are most usually made of No. 2, or easily vitrifiable fire clays. 
Sometimes, to make them harder, so as better to resist handling, various 
per cents of ordinary red burning clays are added. 

In dimensions the blocks are, of course, made to suit the sizes of 
tiles manufactured. The thickness of the block is usually two and one- 
half inches, remaining the same for all sizes. The blocks mostly used 
for Spanish tiles are eleven by fifteen by two and one-half inches. For 
shingle tiles the horizontal blocks are as a rule the same as the Spanish 
blocks, but the risers, or uprights, are seven by eleven by two and one- 
half inches if the shingle tiles are six inches wide and are set on edge. 

While some of the roofing tile plants buy fire clay and make their 
own kiln blocks, it is in most cases better to purchase the blocks from 
the fire brick companies that are fitted for handling this class of work 
and this is most commonly done. On inquiry. The Chas. Taylor Sons Co., 
Cincinnati, Ohio; The Harbison- Walker Co., Portsmouth, Ohio; The 
Stowe-Fuller Co., Cleveland, Ohio; the Federal Clay Products Co., 
Mineral City, Ohio, were found to have supplied the bulk of the blocks 
used by the roofing tile manufacturers, but the ware is of a kind that 
any fire brick manufacturer could readily supply. 

The kiln block should be well made; it should be straight, with 
sharp corners well filled out, true to size, and burned to a point where 
it will stand rough usage without undue crumbling along the edges. 
These blocks are not destroyed by the heat they are called on to endure, 
but by the constant handling in setting up and taking down each time 
the kiln is fired. 

In preparing a kiln for setting, should it be a new one, the first 
thing done, starting at one side in round kilns or the end in rectangular 
kilns, is to place ordinary fire bricks in rows upon the floor of the kiln. 
The first row is placed about three inches from the wall or end of the 
kiln. Each individual brick is placed on its side, and is so spaced from 
its neighbor that the kiln blocks to be used will reach from the center 
of one to the center of the next. This will leave five or six inches be- 



GEOLOGICAL SUBVBY OF OHIO, 371 

tween the ends of the bricks. They are thus continued across the kiln. 
A parallel row is placed so that the surfaces of both rows will be covered 
by one of the kiln blocks. After both rows of bricks are down, blocks 
are then paved on them from end to end. (See Figure No. 163.) 

After the first stand is laid out, a five or four inch space is left, and 
a second stand is put down parallel with the first. In this manner the 
entire floor space of the kiln is laid off. The object of this false floor is 
to elevate the position of the lowest til<;s above the main floor, so that 
they shall not be cut off from contact with the currents of hot gases as 
the latter are deflected over the floor in finding a passage out. Ware 
set on the actual floor would be apt to be spotty and irregularly burnt. 



Fig. 158 — End or Bench Braces in Round Kiln of Spanish Tiles, 

The setter now stands a riser block on the first stand of bottom 
blocks, and against the left hand wall of the kiln. Then he places tiles, 
which are handed to him two at a time, against the riser block. After 
the required number have been placed in a pile, a second riser is put in 
at the point where the two floor blocks meet (see Figure No. 163), and 
a cover block is laid across, connecting from the center of the first riser 
to the center of the second. The rectangular space thus created is called 
a "box." A aecond box is made and filled, using the second and third 
risers and a cover tile. Thus the work proceeds. 

A vertical tier of boxes, reaching from the floor to the top of the 
setting, is called a bench or stand. The latter is the better name, as 
"bench" in other clay industries refers to a horizontal division, not to 



372 



BULLETIN ELEVEN 



a vertical one. When the first stand reaches a level where the setter 
can no longer conveniently reach to put on more boxes, he starts the 
second stand. After one or more courses of boxes has been placed 
across the kiln in the second stand, the setter uses this as a platform to 
carry up the first stand still higher, and so on, until the kiln is filled. 

In round kilns, at the intersection of the stands with the walls 
of the kiln, it becomes necessary to put in braces against the stands 
at each course, to keep them steady and from toppling over endwise. 

It will be seen from the figure that these braces are made by using 
two kiln-blocks, turned at right angles to the other risers, at the begin- 
ning of the last box. Considerable space is thus lost, but it affords 
a secure way of holding the risers in place. 

To hold the benches from reeling or falling over sidewise, no pro- 
vision is made except to keep the stands perfectly plumb, so that no 
tendency to fall is developed. 

The foregoing gives a general idea of the method used in most 
roofing tile works. It will be found that the various styles of tiles, shingle, 
interlocking and Spanish, require some modifications of treatment 
due to their form and there is some element of choice also; i. e., shingle 
tiles are sometimes set in different wavs. 



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Fig. 159— Ordinary Way of Setting Shingle Tiles. 

Setting of Shingle Tiles» — The setting of shingle tiles appears to 
the outsider the easiest and safest of all, but in setting, as in manufactur- 
ing, it is about the most difficult. The actual handling or placing is easy 
and simple; the skill comes in knowing the best method of placing to 
prevent side-checks, center-marks and warpage. There is, however, 
no single l^est method. One plan will best suit one clay, and an en- 
tirely different one some other clay. In the majority of cases, th3 
plain ordinary setting shown in Figure 159 is used, on account of its 
simplicity and cheapness. 

The tiles arc placed in the boxes, on edge, and packed as tightly 
together as possible. It is necessary to pack them snug, in order to 
prevent them from leaning over sidewise as th« shrinkage takes place. 
In some instances, a little sand is scattered under the tiles to assist 
thorn in drawing together during shrinkage, but mortj frequently the 
blocks are left bare. ' 



GEOLOGICAL SUBVBY OP OHIO. 373 

While this style of setting tiles is largely ueed, it has certain ob- 
jections: 

First. The packing of tlic tiles in this manner makes to all intents 
an almost solid block of clay, six by twelve by fifteen inches. Jf a 
really solid block of clay of the above dimensions were to be burned. 



Fig. 160 -Showing High Shrinkage in Boxes of Burned Shingle Tiles. 

it would be considered a very difficult task, and very truly so. It is 
also true to nearly the same degree with a mass of shingle tiles, set 
solid. Many of the standard roofing tile clays have been shown to 
contain considerable amounts of carbon, which must be very carefully 
burned out, at low temperatures. The thicker the individual piece 
or the more solid a group of pieres, the more difficult does it be- 
come to get rid of this carbon from the renter ot the mass. The be.st 
burning temperature for this carbon is at a rather low, clear red heat 



374 



BULLETIN ELEVEN 



(-750° to 800° C), 1380^ to 1470° F. Higher temperatures increase the 
danger of center-marking, and lower temperatures delay the process 
unnecessarily. 

A second difficulty is that of securing contemporaneous shrinkage 
in large masses. As the teniperature increases, the top of a block 
of tiles (in a down-draft kiln) will become hotter than the bottom or 
center of the mass. Therefore the shrinkage will start first on top, 
and unless time be given to allow the heat to soak into the block of 
tiles side-checks will result. 

A third trouble with this method of setting is caused, especially 
in clays of high shrinkage, by the tiles becoming separated and leaning 
over as the shrinkage takes place. It is not unusual for the shrinkage 
to amount to a full inch in a single box, so that the deflection of the 
tiles from the vertical is sufficient to allow them to warp or twist. 

In the case of a clay low in carbon, properly prepared, and of not 
excessive shrinkage, it is perfectly possible to burn shingle tiles in this 
manner of setting in perfect safety. 



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Fig. 161— Method of Setting Shingle Tiles Flat, in Use at Murray Roofing Tile 

Company, Cloverport, Ky. 



The flat method of setting shingle tiles is shown in the above 
illustration. The mass of tiles is set flat, one on the other, instead 
of being set on their edges. Two blocks are set in one box. This 
method of setting was in use at the plant of the Murray Roofing Tile 
Company, Cloverport, Ky., at the time this plant was visited (July, 
1908). While there are some good features about setting shingle tiles 
in this manner, there are at the same time some bad ones. 

In the first place, the block upon which the tiles are placed must 
be perfectly straight, or sand must be provided upon which to bed 
the tiles. This method of setting is faster than the edge setting. Less 
kiln blocks are used, and no attention need be given to keeping the tiles 
from falling over. The fact that both edges of the tiles are exposed 
to the kiln gases, makes the liability to side-check less than by setting 
on the edge, in which case the upper side is sure to heat much faster 
than the lower. 



GEOLOGICAL SURVEY OF OHIO. 375 

The danger of center-marks is for the same reason a trifle less, 
but it is still great. One of the strongest points in favor of this method 
of setting is that the tiles upon reaching a fair state of vitrification 
will have a tendency to straighten out any slightly warped or bent 
tile by their own weight. Increase of the temperature increases the 
danger of warpage where the tiles are on edge, but decreases it as the 
heat increases in the flat-setting method. 

If the tiles happen to be already warped when piled or blocked 
up, it will be found that considerable breakage will result from the 
weight on the warped members. 

With nice straight tiles, and clay of average quality or above, 
this method of setting is unquestionably the best of any seen for shingles. 
It takes, however, ten or twelve days, from the time of lighting the 
fire to closing down, to safely burn a kiln of tiles set in either of the 
preceding ways, while other shapes of tiles can be burned in half the 
time or less, because the setting is more open and free. The relative 
tonnage per kiln would be much in favor of the shingle tiles, and when 
the fuel consumed in firing two or more kilns of other shapes in 
short burns is balanced off against the quantity of fuel consumed in 
firing the shingle tiles in their long burn, the probability is in favor 
of the fuel consumption per ton being less for the shingles. 

On the other hand, on account of the heavy overlap of shingles 
it is likely that the fuel cost per square would be heavier than for inter- 
locking or Spanish shapes.* 

Another method of setting shingle tiles has been used to some 
extent in a few plants, where it has been desired to burn shingle 
tiles in the same kiln with other styles, or, in other words, to hasten 
the time of burning. The plan as used a number of years ago was to 
set the shingles only on the top of the stands or benches, and not in 
boxes. Starting at the side of the kiln, on top of the stand, the first 
shingle was placed flat on a light bed of sand. The next shingle was 
placed in the same manner as the first, parallel to it but with an inter- 
vening space of about four inches. The third tile was placed in the same 
way, and so on, clear across the kiln. Upon reaching the further side, 
the setter returned and placed a second layer of tiles over the first, but 
instead of stacking the tiles one on the other, they were placed so as to 
cover the spaces, each tile overlapping the edges of those beneath by 
about one inch. The setting continued thus until ten or twelve layers 
had been laid down. A couple of tiles were lost on each course owing 
to ^'stepping in" the ends. 

This method had some very good features: First, the tiles were 
set very open, allowing the kiln gases to circulate among them very 
freely. There was consequently no trouble from center marks, as the 
central area of each tile was exposed; second, the chances for side 
checks were reduced to the minimum, as the sides overlapped and car- 



376 



BULLETIN ELEVEN 



ried the weight, thus forming the thickest part of the setting, which 
would naturally shrink more slowly, thus giving the center of the tile the 
advantage and creating a tension there, rather than on the edges. 

The objections to this method of setting are, first, only a limited 
number of tiles can be placed in each kiln (twelve to fifteen courses) ; 
second, being at the top, they were exposed to the direct flash of the 
flames, and many were lost by flashing and overburning. 

An outgrowth of the above method of setting shingle tiles has been 
shown in the following cut. 



r 












1 










h n^Vn n^ 




1 





Fig. 162— Waste- Strip Method of Setting Shingle Tiles. 

It will be seen that this method is a combination of the second and 
third methods, with the difference that straps, or narrow strips of newly 
made shingle tiles, are used as spacers. 

The setter is provided with a trowel and a pallet full of tiles fresh 
from the machine; wuth the trowel, he cuts the narrow strips which he 
places as shown, lightly bedding each pair of tiles down, as he places 
them on the straps. Slight irregularities of the tiles are thus taken up 
by the yielding of the damp straps. 

The advantages and disadvantages of this SN^stem are obvious: 
The dangers of side checks and center marks are obviated as in the pre- 
viously discussed methods. The time of burning is greatly shortened 
from that required to burn shingles set in the ordinary way. And, of 
great importance, the entire kiln can be set Avith shingle tiles if necessary, 
or only portions, as may be desired. On the other hand, it is the most 
costly method of setting shingle tiles, as it requires so much time to cut 
and place the straps. The straps also consume heat, and are a loss at 
the end of the burn. The only use that readily could be made of them 
would be to grind for grogging the body. 

About one-third of the space is lost in each kiln by the use of straps, 
which runs up the fuel consumption per ton. Lastly, the drawing or 
unloading of the tiles from the kiln is more costly, it being necessary to 
separate the tiles and straps. Many of the straps are badly checked or 
broken into short lengths. These pieces fall to the floor and get into 



OBOLOQICAL STTBVBY OP OHIO. 377 

the flues of the kiln, thus causing extra expense in cleaning out the 
kiln bottoms oftener than nould be otherwise necessary. 

For the general manufacture of shingle tiles, this method of setting 
could hardly be recommended. In special cases, where only a few 
Bhingles are required to go with other styles and must be burned at 
the same time, it is certainly the most secure method of getting a high 
yield and good quality. The additional cost is to be endured under 
these circumstances. 

Setting Literlocking; Tilet. — There is practically only one way of 
setting interlocking tiles, viz.; in the "boxes" previously described, as 
built from kiln blocks. The method is very similar to that of setting 
fiat shingles on their edges or sides. 



The interlocking tiles, however, are nested by reversing every 
other tile to make them tit more snugly together, i, e., the head lock 
of one tile is turned to mesh with the heel lock of its neighbor. All 
interlocking tiles are handled in this way in pairs, from the time they 
are dry until they are shipped. 

By referring to Figure 163, it will be very easily understood how 
the tiles are set. The illustration is of a rectangular kiln; below the top 
of the bag walls no side braces are neressary to support the benches. 
Above the bag walls extra heavy blocks made for the purpose are used. 

It is readily seen that in tiles with as much open space between 
them as the interlocking must have, very little if any trouble will result 



378 . BULLETIN ELEVEN 

from center marking or slow oxidation. For the same reason, and also 
on account of the shape, side checks are almost unknown. 

Setting Spanish Tiles* — In setting Spanish tiles, there are two 
methods, one for auger machine tiles, and the other for the pressed tiles. 
While the setting is not widely different, the auger-made tiles require 
more care and experience. The auger-made tiles do not have the 
end locks or ribs, so they are much more apt to warp or twist. The 
locks very materially strengthen the press-made tile. 

By referring to Figure 164, the general method of setting auger- 
made Spanish tiles can be seen at a glance. The tiles are placed on end 
in the boxes, in pairs, a narrow space being left between each pair. If 
the tiles were set tight, it would make a cubic mass of clay 11 x 12 x 14 
inches, which would be very difficult to burn safely. 

It has been found by experience, that for most clays, it is not safe 
to stand the tiles directly on the kiln blocks. Some cushion or yielding 
material must intervene. Should the tiles be placed directly on the 
blocks, the lower end of the roll will be flattened pr spread out during 
the burning. This trouble comes from the inability of the tiles to shrink 
freely. It will be remembered that precautions have to be taken in 
drying this kind of tiles to prevent the same trouble there. 

The liability to spreading of the rolls of the tiles, during burning, 
will be more intensified if the tiles are not set perfectly plumb. If a tile 
leans, it will throw more weight on the corner, or roll, and thus cause 
it to spread more. By placing a blank (called a strap) of damp clay 
on the block before setting a tile, the trouble is usually entirely ob- 
viated. The straps that are used are flat pieces of the same clay as 
the tile, about five-eights of an inch thick by eleven inches wide and 
fifteen inches long. These blanks are run at such times as is necessary 
to have them fresh; they must not be too dry, or they fail to accomplish 
their end. 

In operation the setter places a strap on the bottom block of the 
box to be filled. As the tiles are passed to him, a pair at a time, he 
carefully stands them, as shown in the cut, against the last upright 
block. The next pair of tiles is set about one-half inch from the first 
pair and so on until the box is filled. The soft strap underneath makes 
it possible for the setter to get each pair of tiles vertical. Should the 
end of the tiles be irregular, it will be taken carj of by the pliability of 
the strap. By examining the cut closely the straps can be seen under 
the tiles. 

When the tiles have all been carefully set in the box, the setter 
takes an extra strap, and cuts three strips one inch or more wide from 
it. These strips, also called straps, are equally spaced across the top 
ends of the newly set box of tiles. With a trowel they are spatted down, 
so that they mesh into the openings between the tiles to a depth of one- 
fourth inch or more. This is done to hold the tiles at the proper distance 



GEOLOGICAL SURVEY OP OHIO. 379 

apart, and to pre\'ent them from leaning or falling over, as they other- 
wise would be very likely to do. 

When thekiln has been burned, the tiles and straps separate very 
easily; no trouble ever comes from this source. 

At different times sand has been tried to take the place of the clay 
straps, but it has not been successful. The movement of the kiln gases 
will draw it away from under the outside corners of the tiles, and allow 
them to sag. Also, the sand very soon chokes up the kiln flues. 

While the making and using of straps is an added expense, it is 
necessary, because it has been found next to impossible to burn the tiles 
safely in any other way. With clays of exceptionally low shrinkage, 
or where the vitrification is not carried very far, it may be possible oc- 



Roofing Tile Sc 



casionally to avoid their use. The setting of press-made Spanish tiles 
differs from that last described in that straps are not used. The tiles are 
placed on end in the boxes, with the top end down. The first one is set 
as tight against the riser as possible, the second is set tight against the 
first, and so on until the box is filled. The next riser is then put up, 
the cover block laid on, and the setting of the ne\t box begun. Noth- 
ing is used to bind the tiles together. 

In some cases, where the shape or looks of the tiles will permit, they 
are nested in the box, with every other tile rever.sed, end for end. This, 
however, will depend on how they will nest best, the complete utiliza- 
tion of the space being the object in view. It is impossible to sjt press- 



380 BULLETIN ELEVEN 

made Spanish tiles so tight that they will renter-mark. At best they are 
rather bulky in the kiln; it is impossible to set more than about two- 
thirds as many tiles in a given space as can be done with the auger-made 
Spanish tiles. 

The reason that press-made tiles do not need to be set on straps is 
that the strong lugs, or locks, on the ends stiffen the rolls of the tiles 
and prevent their warping. 

SETTING ROOFING TILES WITHOUT KILN BLOCKS 

As stated before, there are five roofing tile plants that are setting 
their ware without the use of kiln blocks, saggers or other means of sup- 
port. 

In foreign countries this method of setting is used almost exclusive- 
ly; the use of supports is familiar to them, but they do not care to make 
much use of this plan. In the European plants it is the general prac- 
tice to burn their product only till it is weather proof, and their ware 
is what is called in the United States '^porous'' ware. It is th'irefore 
quite possible to set such ware without supports. If producing real 
vitrified ware, such as many of our American plants arc doing, they would 
be compelled to use kiln blocks or other supports. 

The situation as explained for European plant.-) is exactly the case 
with the five plants in this country that are not using supports. They 
are all producing porous ware, and they could not set their ware as 
they do if it were tp be carried to anywhere near complete vitrification. 

By examining Figure No. 165 it will be ^een that on the 
floor of the kiln are placed three courses of fire bricks, cross-hacked and 
very open. This is to allow the hot gases to distribute over the floor 
more evenlv. 

Beginning on these bricks, the tiles are placed on their side in packs 
or bunches of ten each. The first pack is parallel with the kiln walls, 
the next pack is reversed, and so on. It is necessary to wedge them 
tight at the side of the kiln, so that there can he very little chance of 
their rolling. ' 

Upon starting the second course, the first pack is turned at right 
angles to the pack below it; thus every other pack is alternated from 
bottom to top, as well as from side to side. The ends of the tiles in the 
separate stands come close together, so that the chance of rolling in this 
direction is also reduced. In the case shown the tiles are set eight courses 
high. The spaces between the bags aie filled by reversing the direction 
of the rows, as can be eeen behind the man on the left side of the illus- 
tration. 

In drawing the kiln, the bricks on the floor are taken up and piled 
in the spaces between the bags after the tiles have been removed. Thus 



OBOLOGICAL 8URVBY OP OHIO. 



382 BULLETIN ELEVEN 

they are out of the way of the cars in setting, and are placed only as fast 
as new stands are to be begun. 

In this plant it will be seen that the tiles are set directly upon the 
floor. The small opening at the floor line is the **peep hole" for observ- 
ing the heat distribution and for draw trials or cones. It will also be 
observed that very few tiles are reversed — just enough to steady the 
benches. Where it is desired to burn glazed ware and is necessary to 
keep the ware from sticking together, a combination of the t\so meth- 
ods is employed. The glazed ware is placed in boxes in the lower part 
of the kiln, and the open setting without supports is used for the un- 
glazed wares on top of the boxed courses. 

In this case, shown in Figure 167, fire bricks have been edged on 
the floor of the kiln, and upon them boxes made of rectangular fire- 
proofing blocks have been placed. The boxes extend down both sides 
of the kiln, and then across the kiln with each bench. 

The regular setting, without supports, begins on the top of the 
boxes, and continues six courses high. Tile-packs set crosswise for 
braces are placed about every twenty tiles. The tiles which are placed 
directly over each other are not exacth' parallel with each other, but 
are set at slight angles, reversing with each course. This mode of set- 
ting is similar to what is known as *'skintling" in brick setting. It 
avoids any opportunity for the tiles above crushing down between those 
below, and also prevents sidewise rolling in the stand. 

SETTING OF ROOFING TERRA GOTTA* 

The roofing tile manufacturer, as a rule, sets his terra cotta trim- 
mings in the odd space that is left after the kiln has been set as compactly 
as convenient with the regular shapes. This extra space is most usually 
found on top, where the terra cotta is exposed to the most severe heat 
treatment, and where it is most likely to be ruined. This ware, which 
has cost the most to make of any produced in the plant, should be given 
the most favorable opportunity to pass through the kiln safely, rather 
than the least favorable. 

The reason that the terra cotta is as a rule placed on the top of the 
benches is on account of its large size and irregular shape. Hip rolls 
and much of the cresting can be set in the ordinary boxes, but often at 
great loss of space. The finials are too large and ungainly to go into 
regular boxes, and therefore are placed on the top. 

The method of setting finials is clearly shown in Figure 168. They 
are placed on the flange or cresting end, and the ball or head is supported 
by the low pile of kiln blocks or brick, with a damp strap of clay on top 
so that the finial can shrink freely. Gable finials stand on end. Special 
shapes and odd ware has to be set as best it can. An effort should 
always be made to support it equally in all parts. Large tower finials 



GEOLOGICAL SURVEY OF OHIO. 383 

are always burned with the bell up, and the smallend down, the supports 
being built up under the bell- 

Instead of placing the terra cotta on the top of the kiln, it would 
seem the rational thing to provide large kiln blocks of a suitable size 
to aecomniodate it, and then set these large boxes in the center of the 
kiln where the terra cotta would get the most favorable treatment. 
In fact, this is being done at one plant at the present time. 



Pig. 167 — View ii 

The setting of terra cotta in the plants where porous ware is made 
18 a more simple proposition from the fact that there are no boxes to 
limit the number that can be nested together. 



Fig. 168 — Drawing of Typical Terra Cotta Setting, 



384 BULLETIN ELEVEN 

In Figure 169 it will be seen that three courses of loose brick 
work are set on the floor, then five courses of regular tiles, upon which 
are placed two layers of cresting. Then, to protect these courses of 
trimmings, a layer of regular tiles is placed above. Some precaution 
is taken in this plant to protect the expensive ware, but in many of 
the plants producing vitrified ware, no shield or protection whatever 
is given. 

In this illustration it will be seen that the tiles start on the floor, 
no loose brick work being used. First ^ there are three courses of inter- 
locking tiles, then two courses of Spanish tiles, then the special shapes, 
and finally a course of interlocking tiles to protect them, the latter 
being placed flat, simply to act as covers. 

It will be noted also, that straps have been used between the inter- 
locking and Spanish tiles, and between the Spanish tiles and the trim- 
mings. These straps furnish a better foundation to start upon in 
changing the setting from one style of tiles to another, and also permit 
necessary movement between dissimilar surfaces in shrinkage. 

SETTING IN SAGGERS. 

There yet remains one method of setting that has not been touched 
upon directly, though the use of rectangular hollow fire-proofing as 
already described, borders closely upon it. 

A sagger is a fire-clay box, or receptacle, made for containing and 
protecting clay wares in firing. Saggers are naturally of a variety of 
shapes and sizes, according to the ware they are to contain. They are 
used most largely in the pottery industry. Nearly all pottery, ex- 
cepting flower pots and the cheapest grades of stoneware, are saggered. 
Any other clay ware, which by reason of its light cross-section, is not 
able to stand the weight in piling to the necessary height in kilns, or 
which must be protected from flying ashes, dust and soot, or from the 
burning off of its glaze, or damage to its color by direct impingement 
of the currents of kiln gases, may be saggered with the same propriety 
as pottery. Saggers are usually made without lids or covers, Eeing 
stacked one above the other in tall piles or "bungs," the bottom of 
the second forms the cover to the first. At the top of the bung, an 
empty sagger is usually inverted over the last, as a cover. Sometimes 
cover slabs are made for the top course. 

Only one plant was found in this country which had used the sagger 
system; viz., the Bennett Roofing Tile Company, of Baltimore, Md. 
This plant was running in connection with a white ware pottery, and 
it is not to be wondered at that many of the pottery methods were 
carried over into the tile plant. Other roofing tile plants in their begin- 
ning are known to have used saggers, but none have persisted in it. 
The great objection to using saggers is the expense. They are quite 



GBOLOGIOAL aVBTET OF OBIO. 



386 BULLETIN ELEVEN 

expensive to make; their breakage is very heavy; they do not nest close, 
and hence use up kiln space rapidly, and they weigh a good deal, and 
hence consume much heat on each burn. 

To make them more durable they are usually made in oval or 
round shapes, rather than squaire, as would best suit tiles. With the 
round saggers much space is lost in the kiln, making the capacity of a 
kiln very small when compared to the regular setting. 

While the use of saggers cannot be advocated for the setting of 
regular roofing tiles, more can be said in their favor for glazed wares 
and the subject will be taken up m the chapter on glazes. 

SUMMARY* 

While very little, if any comparison can be made as to economy, 
between the two principal systems, the class of ware burnt in one case 
could not be burned by the other method, and in the other case, it 
would not pay to use kiln blocks for setting ware that is not to be burned 
hard. 

The proper method to use will depend on which kind of ware the 
manufacturer wishes to make, vitrified or porous. The clay to be 
used will very frequently govern the details of setting within the general 
system. Some clays begin to vitrify so early that they could not be 
burned except in kiln boxes. 

As between kiln blocks and saggers, everything is in favor of the 
kiln blocks. When drawing a kiln, they can be stacked to the sides 
of the kiln in a comparatively small space, while the saggers are very 
bulky and most of them must be removed from the kiln, thus inaking 
an additional cost of handling and incidentally more breakage also. 
The kiln blocks are heavy and strong and resist handling well, while 
saggers are fragile and of short life at best. Both kiln blocks and saggers 
materially increase th^ fuel consumption per ton of finished clay ware 
produced, and the blocks probably weigh more in proportion to the 
ware they support. 



GEOLOGICAL SURVEY OF OHIO. 387 



CHAPTER IX. 

KILNS FOR BURNING ROOFING TILES. 

The burning of clay wares — or baking as it might more properly 
be called, since the wares themselves do not burn — is the last, most 
difficult and most critical step in the whole process of manufacture. 
By it, the solid, but still soft and easily destructible dried ware is con- 
verted into a hard, more or less vitreous w^eather-resisting artificial 
rock. The process is accomplished by bringing the ware through a 
series of increasing temperatures, affording time at each stage for the 
chemical reactions to take place, and finally reaching a point, in vit- 
rified wares at least, where the body is in a state of incipient fusion, 
and ready at the least strain or least increase in temperature to undergo 
deformation and loss. 

The chemical processes concerned in the burning, and the way 
that the qualities of the product are affected by and dependent on 
burning conditions, have been set forth somewhat fully under testing, 
in Chapter III. The present discussion will deal chiefly, therefore^ 
with the apparatus and methods by which this work is accomplished. 

Since clay burning has been going on in all parts of the world since 
the earliest stages of culture, when man had hardly risen above savagery, 
and since for some hundreds of years at least, this work has been carried 
on on a large scale, and as one of the prominent and essential industrial 
arts, it would seem natural to expect that experience would have elimi- 
nated the more crude, inefficient, and uneconomical methods and enabled 
clay workers to limit their selection of kilns to a comparatively few well 
proved types. To some small extent this has occurred, but there still 
remains an astonishing variety of kilns, of old and well known types, 
and not including those newer phases w^hich have not yet had time to 
fully win their permanent place, and it is not yet possible to prove 
beyond mere unsupported opinion which are really economical and which 
are not. 

Beyond question, there are many kilns in existence, whose type 
is unscientific and whose performance is poor, and yet they are not 
only still used, but new ones are built. The problem of deciding on 
what is really good and what is not, is much complicated by several 
factors — 

1st, — The inherent variation in clays. Some clays are fired rapidly 
and some slowly. Some are very sensitive to the least over-firing. 



388 BULLETIN ELEVEN 

some stand punishment without much effect. Some require very strict 
cooling conditions, and some may be chilled recklessly. 

2nd. — The variety in the products. Every kiln must be suited to 
its charge. It would hardly be natural to expect to fire gas retorts 
weighing tons, and table-ware weighing ounces, in one and the same 
structure. The form, size, cubic capacity, doors, arrangement of fire 
holes, etc., will all have to be adjusted with reference to the ware habitu- 
ally fired. 

jrd, — The inherent variation in fuels. Furnaces must naturally 
be adjusted to fuels, wood, soft coal, hard coal, lignite, coke, oil and 
gas, but in addition, the kiln chamber will require adjustment, accord- 
ing to the flame length of these various fuels. Some fuels will compel 
the use of a muffle to protect the ware, while with other fuels a muffle 
kiln will have to be abandoned in favor of an open type, in order to get 
the heat distributed safely. 

4th. — The unwillingness of clay workers to publish and compare data. 
Trade secrecy in the past has had a strong control of the clay-working 
arts. And today the feeling still. holds to a very surprising extent. 
Even if clay workers v/ere anxious to eliminate poor methods, and low 
grade kilns from their factories, there are enough barriers in the way 
of making comparisons sufficiently exact to thoroughly prove either 
for or against many fine points in kiln design. But when manufacturers 
are unwilling to discuss and compare data, for fear of giving each other 
a fancied advantage, or of exposing their own lack of knowledge, the 
problem of "deeding out inefficiency becomes mountain high. 

Without doubt, other causes in explanation of the status quo might 
be brought forward, but enough has been said to show why burning is 
still so little of an exact science. 

If the countless variations in kilns which have been or are in exist- 
ence are studied, and indeed it is rare to find two alike except on the 
same plant, it will be found that these variations are classifiable to a 
considerable extent, and that the classes thus made w-ill include large 
numbers of kilns varying in small or immaterial details, while agreeing 
in fundamental principles. Such a classification recognizes two main 
subdivisions, I, periodic or intermittent kilns, II, continuous kilns. 

The names indicate the nature of the distinctions. In intermittent 
kilns a charge of ware is fired to the finishing point, cooled down, dis- 
charged, the kilns are reloaded and the same cycle is repeated. In con- 
tinuous kilns, by movement of either the ware to the fire or the fire to 
the ware, masses of ware are always being brought to their finishing 
point, and hence in other parts of the structure, ware is being heated 
up and cooled down, so that all parts of the burning cycle are going on 
at once in different portions of the continuous kiln, while in the periodic 
kiln one thing at a time is done, and so far as possible, the same thing 
'n\ all parts at once. 



GEOLOGICAL SURVEY OF OHIO. 339 

PERIODIC OR INTERMITTENT KILNS. 

This group is the numerous and commonly represented one. A 
very large percentage of all ceramic kilns belong in this group. Though 
admittedly a less scientific and perfect apparatus from the fuel combus- 
tion standpoint, they have certain virtues which will always guarantee 
their use. They are cheap to construct, and therefore require less 
capital to begin operations. They are rapid and independent of each 
other. They produce just as good, and in some kinds of ware better 
products than the continuous. 

The intermittent kiln is almost the sole resource in the roofing tile 
industry of America. In Europe, the situation is reversed, or at least, 
continuous kilns are vastly more common than here. Intermittent 
kilns, as found in use in roofing tile plants in the United States, may be 
classified as follows: 

rSinple stack /Interior (a) 

[Chimney Draft ! ^ ^ Exterior (b 

Round . . . . { [Multiple stacks Exterior(c) 

[Mechanical Draft (d) 



Intermittent 
or Periodic ^ 
Kilns I 



rChimnev Draft /Single stacks (e) 

'[Rectangular T "'"^ """"'' l^ultiple stacks (f) 

[Mechanical Draft (g) 

There are numerous other types of intermittent kilns, but as none 
of them are now used in roofing tile plants, or seem to be in any sense 
an improvement of the kilns now in use, no effort will be made to make 
this classification more comprehensive. 

ROUND KILNS, 

A. Round Down Drafts with Interior Stacks. — While tliere are some 
very good features in this tj'^pe, it has been but very little used in this 
industry. One firm, the United States Koofing Tile Company, is the 
only one in the United States using it, although it has been quite ex- 
tensivelv used in other branches of ceramic manufacture. 

A clear conception of this kiln, as used by the above company, can 
be obtained by reference to the drawings shown on page 391 (Figure 
171). 

The kiln as built is twenty-four feet inside diameter. The walls 
consist of a nine-inch fire brick lining, and a thirteen-inch outside wall 
of common brick. From the floor to the spring of the arch, is seven feet 
six inches. The crown has a rise of five feet three inches, thus making 
the total inside height from the floor to the apex of crown, twelve feet 
and nine inches. 

The foundation walls are four feet wide by three feet deep, measur- 
ing from the grade line. The ''hub," as that portion of the kiln in which 
the furnaces are construct^ed is called, is thirty-six inches wide. 



390 BULLETIN ELEVEN 

By referring to the sections showing the ground plan, the flue 
system of the kiln can be readily understood. It will be seen that below 
all other parts of the floor is the large four-way or cross flue; this flue 
is twenty-four inches wide by thirty inches deep. At the junction of 
the four-arms, and carried by the side walls to the large flue, is the 
center stack, which is twenty-four inches in diameter, w^ith four inch 
walls of circle bricks. 

Connecting the four outer ends of the four-way flue is a circular or 
ring flue, twelve by twelve inches, shown insection D-D. This ring flue 
intersects the main cross flue, so that their upper surfaces are on the 
same level. On top of the ring flue is a system of radial flues shown in 
sections E-E and F-F. The radial flues are sixteen in number, nine by 
nine inches in cross section, consisting of eight long flues reaching from 
the stack to the side walls and eight short or intermediate flues that 
reach from the ring flue back almost to each bag. 

The covering to the radial flues is of stock floor or flue bricks, 
twelve inches long, part of them having an open slot one by five inches 
on one side. (See Section FF.) 

The space between the radial flues is filled in solid and paved level 
with the top of the bricks covering the flues. Thus the kiln has a solid 
floor over about one-sixth of its area. The flue bricks can be taken out 
at any time in order to clean out the flues; no other part of the floor need 
be disturbed. The slotted bricks can be shifted about to secure the 
best distribution of the gas currents. 

It will be observed that the bag walls, G, are ver)^ low in this kiln, 
only about two feet above the floor. It has been found by experience 
that a higher bag throws too much heat to the top of the kiln. With 
the present bag the heat equalizes very nicely. The firing is done with 
natural gas. 

The small sketch shows the style of furnace used. A two-inch gas 
line is carried around the kiln on the hub. At each furnace a one-inch 
drop line is carried down to a point where the blast from the burners 
will strike just above the floor level. There are two stop-cocks in the 
drop line, one in the down pipe and the other between the burners, thus 
one burner can be lighted at a time. The burners are of the ordinary 
type, having a cast iron mixer, into which short lengths of two-inch 
pipe are put to form the burner nozzle. 

Just above the burner can be seen two openings, five by six inches. 
When the kiln is first lighted these openings are closed, but as the burn 
progresses they are opened more and more until wide open at the finish. 

The heat generated in the bags passes up into the kiln, is draw^n 
down through the ware into the radial flues, then into the ring-flues, 
which in turn carry it to the four-way cross-flue, and thence it passes 
up the stack and out to the open air. 



GEOLOGICAL SUBVEY OP OHIO. 




Cxciioit fi-OS 



392 BULLETIN ELEVEN 

In an ordinary burn, lasting from four to five days, about 400,000 
cubic feet of gas are consumed. 

Advantages of this Kiln. — First: The flue system lends itself very 
easily to changes found necessary from burn to burn to regulate the dis- 
tribution of the draft. Second: The flue system can be very easily 
cleaned. All that is necessary to do is to lift out the flue brick, and then 
with a small fire shovel remove the debris. Third: The center stack 
becomes heated very early in the. burn, thereby furnishing a good draft 
at a time when it is needed to remove the water smoke and prevent the 
deposition of scum or whitewash. Fourth: The fact that all waste heat 
must pass through the center of the kiln insures that the center will 
not be materially lower in temperature than other parts. Fifth: In com- 
parison with kilns having their stacks outside, it is very much cheaper 
to build. The center stack is only four inches thick and is very short. 
There are no underground flues to connect it with the kiln, as in outside 
stacks. 

Disadvantages. — First: The available kiln space is reduced by about 
twice the cubic contents of the stack each burn. This, however, is not 
large, rarely over five per cent., and often less. Second: The strongest 
objection is due to the stack being in the way of setting and drawing 
the kiln. This objection is valid, especially with roofing tiles set in kiln 
blocks. It becomes very troublesome to work around the stack. Also, 
the dry w^are to be set can only be brought half way in the kiln on a car. 
With trucks this trouble disappears. If the kiln were built larger it 
would be possible to get a car of tiles past the stack, but wuth small 
kilns it is not. 

While the stacks as built by this company have no dampers on 
them, this type of kiln admits of very easy control by a top damper. It 
is a much more economical plan to have a damper fitted to the top of 
each stack than in any other way, and the draft can be kept under con- 
trol as the heat increase^. 

B* Round Down Draft Kilns with Exterior Single Stacks. — There are 
three plants using kilns of this type. One that has been in use for the 
past ten or twelve years in the plant of the Cincinnati Roofing Tile 
Company, using coal for the fuel, is shown in the drawing, Figure 172. 

The kiln is twenty-two feet in inside diameter, with walls twenty- 
two inches thick above the hub. The hub has two offsets. The inside 
height is seven feet to the spring of the crown, with a five foot rise, mak- 
ing twelve feet high at the apex. The bags in this kiln extend up five feet 
above the floor, differing from the gas-fired kiln previously described. 
It was found better here to carry the gases from the coal furnaces up 
into the crown of the kiln, and allow combustion to complete itself at 
that point and then pass down through the ware. The quality of the 
fuel is therefore the determining factor in this change. 



GEOLOGICAL SURVEY OF OHIO. 




SeeT/en R-O-B 
Fig. 172— Round Down Draft Kiln. Cincinnati Roofing Tile & Terra Cotta Co., 



394 BULLETIN ELEVEN 

The flue system is in part like the kiln just described. In the cen- 
ter of the kiln, and under the floor level, is a well-hole thirty inches in 
diameter. Leading from the well-hole out under the w^all of the kiln to 
a stack is a large flue, twenty-four by thirty inches. Opening into the 
top of the well-hole are four cross-flues, twelve by sixteen inches, in 
cross-section, which lead to the walls of the kiln. Just above, and cross- 
ing the four flues at right angles in each quarter of the kiln, are a set 
of small, narrow flues four by twelve inches. (See Section EE.) Above 
these narrow flues is another set of cross-flues upon which the open 
floor bricks, shown in FF, are placed. 

The heat, in passing through the kiln, enters the bags, is carried 
well up into the crown, passes down through the ware, sieves through 
the floor bricks into the first small flues, then into the lower ones, and is 
thence conveyed to the four cross-flues, which carry it- to the center well 
hole. From here it passes by the large. flue out to the stack. A vertical 
damper is placed between the kiln and the stack. In the sections marked 
FF, the flpor bricks should be shown in parallel rows, and not staggered, 
as indicated. 

A rather peculiar feature of this kiln, not seen on any other, is the 
small vent stacks over each furnace bag. These stacks are about three 
feet high, and nine by nine inches in cross-section. During the most 
of the burn they are kept covered with slabs, but in the early part or 
warming-up period they are more or less open, allowing much of the 
smoke from the coal fuel to pass out. This gain is at the expense of 
much of the heat which the coal has generated. The idea is not worthy 
of imitation. 

The furnaces of this kiln are also unique, in that step-grates of 
brick arches are used. No iron grates are employed. The arches 
are each about five inches lower than the one above, and sit back into 
the furnace about five inches farther. In firing a furnace of this type, 
the fire is lit on the floor, under the bottom arch and well back into, the 
bag. As the fire increases, fuel is fed in from above the uppermost arch. 
Instead of raking out the ashes, they are allowed to fill up, until at 
last the fuel fills the fire hole completely, drawing its supply of air 
through the spaces between the arches. The furnace is like an ordinary 
dead-bottom one, but the arches act as a substitute for the mass of 
clinker which holds up the fire and lets air get through it. The brick 
arches, or step-grates, are widely used abroad, but are uncommon in the 
United States. For some coals, they offer great advantages over the 
clinker grate. The only disadvantage they offer is in cleaning out the 
fire hole, either during or after the burn. With a very clinkering 
coal, this trouble might be rather serious, but with ordinary fuel, it 
would be unimportant. 

This company uses these fire-holes as miniature gas producers. 
That is, they generate the gas in the fire-box, and complete the com- 



GEOLOGICAL SUHVEY OF OHIO. 



Fig. 173-Gas Produce 



Fig. 174 — Double 



396 BULLETIN ELEVEN 

bustion in the kiln. It will be seen in Figure 173 that the entire lower 
part of the furnace has been shut up wuth bricks and kiln blocks. 
The fuel is piled up until it nearly shuts off the air space under the 
arch. As the fuel roasts and cokes, it gives off gas which passes up the 
bag; meeting a supply of air at the inlet-pipe shown above the furnace, 
the two mix and pass on into the kiln, burning as they go. Complete 
combustion does not take place until the gases have traveled a con- 
siderable distance. 

Advantages. — First. The entire flue-system, except the stack- 
flue, is above grade, thus insuring a dry bottom to the kiln. Second. 
The furnaces are cheaply constructed. 

Through long experience with this kiln, it has become possible 
to obtain very uniform burns, with but a small percentage of loss. 

Disadvantages. — First. The flue system is rather expensive to 
construct. Second. The flues are verv hard to clean. It is necessarv 
to take up the upper set in order to reach the low-er ones. Third. The 
draft is very apt to be stronger over the four cross-flues than elsewhere. 
No provision has been made to prevent this. Fourth. There is no 
provision made to control or shift the hot gases to various parts of the 
kiln, other than the manipulation of the fires. Fifth. The small 
stacks are an added expense, and when opened only serve to carry the 
heat from the bag direct into the air. It would be better not to gen- 
erate the heat in the first place, if it has to be gotten rid of. Sixth. 
The furnaces are very hard to keep in repair. The small arches are 
very easily knocked out, while cleaning out ashes and clinkers. 

As to the method of firing; viz., working the furnace as a gas pro- 
ducer, if properly handled, it is a very good plan. It puts the combustion 
of the fuel and the evolution of the heat at a point where needed, and 
w-here the greatest benefit can be derived. Another strong point in 
its favor is that very little ash or dust is carried over into the kiln. 
The air in passing through the thick fuel-bed creates an intense local 
temperature, which makes the ashes sticky and there is little tendency 
for the ash to fly along into the kiln as in flat-grate furnaces. It takes 
about five days, using the best Pocahontas coal, to fire off a kiln. De- 
pending on the climatic conditions and the kind of ware set, the amount 
of fuel consumed runs from fifteen to twenty tons per burn. A com- 
parison of fuels used in various plants is of little value, unless all con- 
ditions are considered. 

The Ludowici-Celadon Company, at its New Lexington, Ohio, 
plant, uses kilns twenty-six and thirty feet in diameter, and about 
twelve feet high in the center of the crown inside. Their main difference 
from the preceding is the construction of the flue system, which is in 
reality a combination of the two previously described. The gases 
are all collected in a center well-hole, and sent to the stack by a 
flue leading out under the kiln wall. Leading into the well-hole are 



GEOLOGICAL SURVEY OF OHIO. 397 

radial flues, which reach out to the outside wall between the bags. 
About midway between the well-hole and the wall is a ring flue, inter- 
secting all of the radial flues. From the ring flue, shorter radial flues 
are led off between long ones, and terminating at the point of the bags. 
Thus the kiln bottom is well served with radial flues. On top of the 
radial flues is a zone about eighteen inches high, traversed by parallel 
cross-walls, supporting the paving course or floor proper. These 
walls are built with spaces between each brick, as open as consistent 
with stabilitv. The common name for this is **feather work" or **mid- 
feathers." The purpose of the * 'mid-feathers" is to permit the gases 
which have passed the floor to flow laterally in any direction to the 
point of escape with the least resistance. The clogging of one avenue 
leaves manv others available in kilns in which this mid-feather con- 
struction is used. The mid-feather, however, is not a mode of forcing 
the gases to flow to definite points or to insure distribution in passing 
through the floor. It has no such function, but in many kilns it has 
been used as if it had. With no means of controlling the distribution 
of the draft except the **checker-bottom" and **mid-feathers," the 
worst sort of distribution is likely to result. 

There were two sets of furnaces on these kilns, one set using coal 
and the other natural gas. The kilns were heated up with coal and 
finished off with gas; the reason being that gas was more expensive 
than coal. The gas, being less apt to flash the ware than coal, was 
used to finish the burn, rather than start it. 

It will be observed (Figure 174) that there is a large three-inch 
gas line around the kiln. From this line, one-inch lines pass down to 
the furnaces, which have been built in between the regular coal fur- 
naces, which are shown closed up with kiln blocks. Since the above 
notes were taken, the company has been enabled to obtain a greater 
supply of gas, and has discontinued the use of coal. 

Advantages. — First, The flue system is largely above ground, 
insuring dry bottoms. Second. The radial flue system, covered by 
mid-feathers, allows the heat to move freely under the floor, and thus 
to equalize. Third. The floor or flue bricks, being easily movable, 
enable the draft openings to be rearranged, by inserting solid bricks 
in place of perforated ones. They also facilitate the work of cleaning 
the bottoms. 

Disadvantages. — It has a weak draft in the early part of the burn. 
This is typical of all kilns having deep bottoms and outside stack con- 
nections. They also are subject to weather changes. As a whole, 
it can be said that these were the best round kilns found in use. 

One other plant was visited in which round kilns with outside 
stacks were used. The kilns in this instance were of twenty-six feet 
inside diameter, and of the usual height. The exact arrangement 
of flue svstcm in the bottom could not be obtained. It was much too 



398 BULLETIN ELEVEN 

deep-seated; that is, the floor was at grade-line and the flue system was 
all below grade, and certainly would be likely to be very damp. The 
tiles that were being produced in this plant had all the indications that 
such was the case, for they were not only soft burned in the lower part 
of the kiln, but were very badly scumme<l. 

C Round Kilns with Multiple Self-contained Stacks* — There was 
only one plant using this style of kiln. In this instance, the kilns 
were of two sizes, twenty-four feet and twenty-eight feet in diameter 
inside, an<l having a central inside height of about twelve feet. The 
bags were about thirty inches high above the floor. The. floor itself 
was nearly solid, except for openings five inches by .five inches, about 
twenty-four inches apart, along radial lines from the center of the kiln 
to the walls. These openings led into flues running from the base 
of small stacks, located in the kiln-wall between each fire place, toward 
the center of the kiln. These flues did not meet in the center, or else- 
where. They were about twelve inches by twelve inches, inside di- 
mensions. The stacks were carried independently above the side walls 
of the kiln about six or eight feet. 

In theory, the multiple stack appears good, but the actual operation 
is otherwise. The idea is that each stack will drain one section of the 
kiln floor, and that by regulatrion part of the floor can be brought up 
or held back at the will of the operator by merely using a damper. 

In practice it is found that in order to drive the heat to any one 
or two sections of the kiln it would be necessary to shut all the other 
sections off, and in doing so the draft would not be sufficient to main- 
tain oxidizing conditions. 

The building of the stacks in the vvall of the kiln is a source of 
weakness to the walls. Tlie stacks become hotter than the adjoining 
parts of the wall, and hence expand more, bringing about a continual 
strain, which in time will rack and materially weaken them. 

The above described multiple-stack kilns are using natural gas. 
The burners are of a patented type, known as the Kearns Automatic 
Gas Burner. The burning is of three to four days' duration, and con- 
sumes frojn 140,000 to 160,000 cubic feet of gas. 

Advantages. — First. It is claimed that the draft can be localized 
to any particular part of the kiln. Second. No yard room is taken up 
by the stacks. Third. They are cheaper to construct than outside 
stacks, being shorter. Fourth. The kiln has no deep flue s^^stem, as 
the stack openings may be on a level with the floor if desired. 

Disadvantages. — First. The draft control is not nearly as exact 
or sati3factory as the projector of the idea expected, as explained above. 
Second. In starting off the burn, the stack areas are in excess of the 
kiln needs, and reversion of the draft is very common; i. e., a stack 
will suck cold air into the kiln instead of carrying hot gases out. This 
is difficult to prevent, and takes a great amount of care and watching. 



GEOLOGICAL SURVEY OF OHIO. 399 

D. Round Kilns with Mechanical Draft* — At no point were kilns 
of this variety being used, but this system could very well be applied 
to many of the round kilns now in use, which now have a sluggish 
draft and are giving poor results at high fuel cost. The system will 
be discussed in connection with rectangular kilns. 

Summary on Round Kilns. — It can safely be said that the use of 
the round kiln in the roofing tile industry has passed its climax, and is 
rapidly being replaced by the rectangular kiln. 

While the round kiln can be built cheaper, and has a longer life, 
it has drawbacks that more than outweigh these advantages. The 
great objection for roofing tile purposes is that they interfere so seriously 
with convenience in setting. The curved walls do not lend themselves 
readily to the system of setting necessary. It is impossible to brace 
the stands at the side walls in the proper manner. Too much valuable 
space is lost by having to insert so many side braces in the tile benches. 
Also, the individual fire-bags or ^'pockets" around which the ware has 
to be built interfere seriously. A circular flash wall is possible and is 
undoubtedly better, but is seldom used, on account of difficulty in 
keeping it up. 

A much greater per cent, of flashed ware is obtained in round kilns 
than in the rectangular. This is due to the fact that about one-half 
of the fire-bags are throwing their hot gases into the kiln at right angles 
to the benches, that is, against the sides of the tiles, while in the rect- 
angular kiln all hot gases come into the kiln parallel with the benches. 

It cannot be denied that excellent results can be obtained with 
the round kiln. It has an unquestionable advantage in the ease with 
which a flue system can be made to give even draft over the whole 
floor. 

Fuel consumption is less in the round kiln than in a rectangular 
kiln of the same superficial floor area, owing to a proportionately less 
wall area. This difference is probably offset by the less lost space in 
the rectangular kiln, by which the heat that is generated is made to 
do more work. 

But notwithstanding all the good qualities of the round kiln, it 
is on the average impossible to turn out ware as cheaply as in the 
square kiln, or of as good quality and quantity. 

If built at all for burning roofing tiles, the round kiln should be 
large, about thirty feet in diameter, so that the loss in setting will be 
reduced to a small factor. The height of the kiln should also be greatly 
reduced from that in general use at the present time (twelve feet). 
It would be better to build eight feet, 'and at the outside figure nine 
feet in height at the center of the crown. The kilns built in the past 
arc so high that it is extremely hard to get the heat to the bottom. 



400 BULLETIN ELEVEN 

Very frequently the top ware is overfired in the effort to bring up the 
bottom temperature. With a lower crown this would be largely 
overcome. 

As to 'the flue system, it should be of the radial type, leading to 
a central well-hole. The floor should be as near solid as possible, on 
account of the large amount of scrap that will otherwise fill up the flues. 
The so-called checker floor is not recommended. 

The chimney, if one is used, should be outside of the kiln. One 
large stack for four kilns is satisfactory. Miechanical draft should be 
used where possible. 

The furnaces of course will depend on the nature of the fuel. If 
coal, either the flat or inclined grate-bar type is preferred. While 
the flat grate-bar furnace will require more labor and attention, it will, 
if properly attended to, give the best results, and use the least fuel. 
The main trouble with the flat grate-bar furnace is, that the bed of 
fuel, if kept thin, burns through in patches every few moments, thus 
allowing streams of cold air to enter the kiln. If the fuel layer is 
not kept thin, all the advantages which belong to the flat grate type 
are lost, and one might as well use the inclined or dead bottom types 
at once. The inclined grate-bar furnace, on the other hand, is more 
likely to prove better in the hands of a careless burner, because the 
fuel layer will slide down the bars, and automatically prevent leakages 
of air to a large extfent, and thus does not require such constant 
attention. 

RECTANGULAR KILNS. 

This style of kilns is at the present time most popular amoAg the 
roofing tile manufacturers, and is likely to remain so. There are at 
present over half of the plants using rectangular kilns; those rebuilding 
or putting in new kilns at the present time are all installing the rectan- 
gular kilns. 'This tends to show where the general opinion rests, and 
it has not come from the desire to try something new, but as the result 
of actual experience with both types of kilns in many different plants. 

The general objections to rectangular kilns are: First, that they 
are more expensive to build and keep in repair than the round kilns; 
second, that it is more difficult io get an even distribution of the draft 
over all parts of the kiln, the ends and corners of the kiln being the most 
difficult to bring up uniform with the rest. Both of these objections 
are real, but are overbalanced by the advantages, 

E* Rectangular Kilns with Single Exterior Stacks^ — Two plants 
were visited in which kilns of this type were in use. The kilns themselves 
were very closely like that of the Detroit Roofing Tile Company, which 
differ only in the use of mechanical or fan draft instead of a stack, and 
the description and drawings will be given under that heading (G.). 



GEOLOGICAL SURVEY OF OHIO. 401 

The points in favor of a single stack vs. multiple stacks are much 
less pronounced in rectangular kilns than in round ones. If rectangular 
kilns were square, it would probably be better to use one stack per kiln, 
as in round kilns, and for the same reasons. But as nearly all rectan- 
gular kilns are not square, but much lengthened on one axis (in one in- 
stance three hundred feet long by only eighteen feet wide), the problem 
of securing uniform draft distribution over the whole floor surface is much 
altered. 

In general, the advantages which accrue to one stack for a circular 
or a square kiln can be retained in long rectangular kilns by making 
the kiln's length equal to two, three or more times the width, and di- 
viding the floor by cross walls into squares, each of which has a stack 
and a complete flue system of its own. For instance, with a kiln eighteen 
feet wide the length might be* made thirty-six feet, and two stacks used, 
or fifty-four feet and three stacks, or seventy-two feet and four stacks, 
etc. The kiln thus becomes in efifect a series of contiguous square kilns 
in line, surrounded by exterior walls and roof in common. The general 
principles found useful in round kilns obtain with rectangular kilns, 
also, viz., floors above grade level, shallow flue systems to avoid damp- 
ness and excessive fuel consumption, exterior stacks to save loss of 
interior space, a flue system extending to all parts of the floor with equal 
frictional surface, solid floors covering the flue system, perforated to 
admit the gases so as to give to every square yard of floor area an 
equal draft, a stack adequate to give a good draft in the beginning of 
the burn, when the temperature is low, and damper arrangements which 
will give entire control of the draft at any stage. 

F* Rectangular Kilns with Multipk Stacks* — By this is meant the 
use of stacks in more frequent proportion than one per ''unit square of 
floor space" (i. e., a length of space equal to the width of the floor). Mul- 
tiple stack kilns use from two to five times as many stacks as are 
recommended in the "unit floor space*' plan. 

The Eudaly Type* — The type of the multiple stack kiln is the 
Eudaly, originally introduced as a patented kiln, and sold extensively over 
the country on the yard-right plan. For years the essenfial features have 
been pirated in so many ways that many kilns can now be found which 
are Eudaly in type, but not in details, and built without authority from 
the owner of the original patents. This '^'"^n took place while the orig- 
inal patents were still comparatively new. 

A kiln of the Eudaly type is in use at the Huntington Roofing Tile 
Company's plant, Huntington, W. Va. It is eighteen feet wide by thirty- 
eight feet long inside, by seven feet to the spring of the crown. The 
crown has a rise of five feet, making the total height twelve feet. The 
floor system is the characteristic feature. The rectangular bottom is 
divided by a center wall extending lengthwise of the kiln bottom from 

26— a. B. n. 



402 BULLETIN ELEVEN 

end to end. At right angles to this dividing wall are cross walls, spaced 
opposite each furnace, and extending from the kiln wall to and connect- 
ing with the center wall. Thus the kiln bottom is divided up into sec- 
tions, each of which has its own flue system, connecting with its own 
chimney in the side of the kiln wall, midway between each furnace. 
These blocks are usually about seven or eight feet wide by eight to ten 
feet long. The area of the stack draining this area Is small, about twelve 
by eighteen inches. 

These stacks connect with flues running straight. through the mid- 
dle of each section to the center wall. The bottom of the stack and the 
flue are on the same level, generally about thirty-six inches below the 
floor line. The flue is about eighteen inches deep. The whole section, 
seven feet wide by eight feet long, is now covered with small four-inch 
mid-feather walls parallel to the axis of the kiln and five inches apart. 
These mid-feather walls cross the flue in the center by arching, or by 
tiles on edge, or even lapping each course till one brick will bridge the 
gap. The mid-feather walls are now covered with perforated floor brick. 
This makes a floor through which the gases pass with perfect freedom 
at any place, and therein lies the vital defect of the system. 

The claims made for the Eudaly kiln were that by having each sec- 
tion of the floor drained by a stack of its own, perfect control of the 
draft was assured, it being only necessary to operate the dampers on 
the stacks to force the draft to any particular section of the kiln. This 
idea appears plausible, but in actual practice it does not work out as 
expected. The hot gases, being able to pass the floor at any point, will 
take the shortest road to the stack. The central area of the kiln, fur- 
thest from the stacks, and the floor along the cross-walls are practically 
without draft. There is another trouble, viz., the stack area is extrav- 
agantly great. The result of this great stack area and the open or "check- 
er" floor is that the gases supplied to the kilns by the fire boxes rush to 
the base of the stacks by the ''short cut," and leave the more distant 
parts of each floor section stagnant. 

Closing a damper on one stack does no good. Unless practically 
two-thirds or three-fourths of the dampers are closed, no compulsion 
is exerted on the draft movement, for the excess of stack area is so 
great. The cross-walls in the bottom are absolutely ineffective as a 
mode of control of the draft distribution. There are also too many 
dampers to regulate. Too much of the burner's time will be consumed 
for the results obtained. 

Ordinarily the Eudaly kiln is fired with coal, but in this instance 
gas is used. The time of firing is extremely slow, about twelve to fifteen 
days being spent for the entire burn. It must be remembered that the 
Huntington Company is manufacturing flat shingle tiles exclusively, and 
this style of ware and the method of setting at this plant require a long, 
slow burn to get proper results. 



GEOLOGICAL SURVEY OF OHIO. 403 

A bad feature of this kiln, iis constructed in the above plant, is the 
height. It is from three to four feet too high. The top area becomes 
excesaively hot and by its radiations down onto the ware there is con- 
stant danger of spoiling the top courses. With a low crown filled full 
of ware, the gases would flow among the ware and heat it much more 
evenly. 

Stewart Kiln. — The National Roofing Tile Company were using 
Stewart kilns, the inside dimensions oE which are fourteen feet wide by 
twenty-five feet long. They are six and one-half feet high to the spring 
of the arch, with a three foot rise, giving a kiln of nine and one-half feet 
in total height, which seems an excellent proportion. Their novel 
feature is the method of bringing the heat into the kiln, and out again. 



Fig. 175— Stewart Kiln, National Roofing Tile Co., Lima, O, 

Along each side of the kiln are flat-grate furnaces, of which the flues 
lead under the kiln floor to the opposite side, where they deliver the 
gases up into ordinary fire bags. The furnaces on the right hand side 
of the kiln furnish the heat for bags on the left hand side, and vice versa. 
These flues passing under the floor become intensely heated, and trans- 
mit a great deal of heat upwards by conduction through the floor, and 
radiate it among the wares piled above. The gases entering the kiln 
at the tops of the bags heat the ware from the top downwards. The 
zone of least temperature is between these two sources of heat, usually 
about one-fourth of the way between the floor and the top of the setting. 

The construction of the flues and the floors requires more care than 
usual, because they carry the greatest weight and the highest tempera- 



404 BULLETIN ELEVEN 

ture. Any softening or failure means great loss. The thickness of the 
floor varies from nine to four and one-half inches in diflferent cases, de- 
pending on the wares to be fired. The less sensitive the ware, the thinner 
the floor may be made. 

The gases are then taken out of the kiln at the floor level by stacks 
opening into the kiln walls. No floor system of any sort for regulating 
the distribution of the draft is used. This is the weakest point in the 
Stewart kiln, and has been much improved at the plant of the Colum- 
bus Brick and Terra Cotta Company, Union Furnace, Ohio, by bring- 
ing in a flue system which is not a part of the Stewart system. 

Advantages — First, the main claim for this kiln by its makers is 
that it is possible to burn the bottom as hard as the top; second, that the 
bottom of the kiln warms up first so that the ware in the lower half of 
the kiln does not sweat in the early part of the burn and become kiln 
marked or scummed by dampness; third, the solid floor makes cleaning 
very easy and the draft is always unobstructed. 

Disadvantages — First, the distribution of draft is ver}*^ poor. In- 
stead of passing down through the .ware to the flo9r at all points in the 
kiln equally, it tends to pass over the top of the ware, and down near 
the end where the outlet flues are located. Thus a large part of the 
central area of the kiln must be heated by conduction and secondary 
convection, and not by direct flow of hot gases; second, the loss of heat 
due to radiation downward into the ground from the flues under the 
floor is not to be overlooked; third, where necessary to reach a high 
temperature in the ware, it will be found that the throat to the under- 
ground flues will burn out, owing to the heavy fire that must be main- 
tained in the furnaces, in order to carry it under the floor and up the 
opposite side. This kiln as a whole cannot be recommended, unless its 
flue system for discharge of gases be materially altered. Even then 
its fuel consumption is probably pretty high per ton of ware. 

Grath Solid Bottom Kilns. — This kiln was found in use at the West- 
ern Roofing Tile Company, Coffeyville, Kan. It is fourteen and one- 
half feet wide by forty-two feet long and nine feet high inside. It has 
eight gas fired furnaces on each side. 

The main difference between this kiln and the one last described 
is, that part of the heat is carried through under the floor and a part of 
it can be taken up direct into a bag on the same side where generated. 
In this respect the kiln is superior to the Stewart, because the furnaces 
do not have to be forced so hard to get the temperature in the kiln. 
The amount of heat that need be taken up direct, and not passed under 
the floor, is regulated by a sliding damper at each furnace. 

After the hot gases have entered the kiln, either by one route or 
another, they are supposed to travel down through the ware and along 
the floor to the end walls, where they enter openings leading to two 



GEOLOGICAL SUHVEY OF OHIO. 




Fig, 176— Mitchell Kiln in Use at Detroit Roofing Tile Co., Detroit, Mich. 



406 BULLETIN ELEVEN 

small stacks at either end of the kiln. The same objections hold here 
as for the Stewart kiln, namely, too much radiation loss from the under 
floor flues, and a very poor draft distribution. 

Hence,, for economical reasons and uniformity of burns, this kiln 
is not to be recommended, though it should be given preference over 
the one last described. It is susceptible of improvement by use of 
proper flue systems to collect and carry out the gases. 

G. Rectangular Kilns with Mechanical Draft* — The Detroit Roofing 
Tile Company is operating a kiln in a way which may be instructive 
to others. The drawings of the kiln are shown on page 405. The 
kiln is fourteen feet wide by fifty-six feet long inside, with a height 
of ten feet. The walls are twenty-seven inches thick, including the 
four inch fire brick lining. 

The furnaces are now fired with crude oil, but are made large enough, 
so that grate bars can be inserted, and resort be made to coal at any 
time. The bag walls are continuous, extending the entire length of 
the kiln on either side, so that there are no odd corners in the setting. 
In this kiln it wuU be observed from the end section D-D that the bag 
walls are carried w^ell up to the crown; in fact, a four-inch space is all 
that is left open. Hence, the greater part of the hot gases are thrown 
well up into the crown of the kiln, before turning down among the ware. 
The flue system, however, is the important part of the kiln. It con- 
sists, first, of a large flue crosswise of the kiln at the center, leading to 
the fan, which furnishes mechanical draft. Leading out towards the 
end of the kiln from the cross flue are smaller flues (see section E-E). 
These flues are about eight inches by sixteen inches, and are covered 
with kiln blocks, so spaced apart over each fluie that openings about 
two inches wide are left near the center of the kiln close to the main 
flue. These openings are made larger and larger until at the ends of 
the kiln they are from four to five inches wide (see Sections E-E and 
B-B). 

After this sub-floor of blocks has been constructed, the mid-feather 
flue walls are carried up about twelve inches more (see Section D-D). 
On the top of these mid-feather walls, are placed the open floor bricks 
or * 'checkers'' (see Section .^-A). Immediately over the main cross- 
flue, the floor is made solid for about five feet wide (see Sections A-A 
and E-E). 

The idea in having the sub-openings through the floors into the 
flues made larger near the end walls and closer at the center is to equalize 
the draft distribution, which is always likely to concentrate at the 
opening into the main draft flue. In this case, the tendency would be 
to leave the ends and corners cold, and the center hot, if the floor were 
not built as described. The fact that the floor bricks are laid dry enable 
them to be moved or shifted at will, and the draft to be changed by insert- 
ing solid bricks in place of perforated bricks at any point in the floor where 



GEOLOGICAL SURVEY OF OHIO. 407 

the draft may have been too great. After the kiln floor is once properly 
adjusted to suit the local conditions, it will very rarely need to be changed 
or moved except to clean out the flues. The flues are easily cleaned 
out; nearly all of the dirt falls upon the kiln blocks separating the upper 
and lower flues. Hence all that is necessary is to take up the floor 
bricks and remove the accumulations of scrap and dust. It is not an 
expensive kiln to build; while the flue system is rather deep, it is of 
straight brick work, very little chipping or cutting being necessary. 



This kiln as constructed at the above plant is too low in the ground. 
It will be observed from the drawing that the floor is on a level with 
the yard grade. The flues are therefore all below grade. In a dry soil 
this would not be a matter of great importance, but very few localities 
are so dry that the lower flues are not quite apt to be damp. 

In case of coal firing, this question of level of kiln floor to yard 
level would be very troublesome. It will be noted that the ash pit 
and furnaces are below grade. Of course, as long as oil or gas is the 
fuel, this point does not matter. 

In Figure 177, the depressed furnaces can be seen, with the oil 
and steam pipes on the grade line. 

The system of staying the kiln is very poor. The large channel 
irons which serve as buck-staves have been placed on the flat, against 
the kiln. A channel iron on the flat is very weak. The same amount 
of iron as has been used in the large channel, if distributed between 



408 BULLETIN ELEVEN 

two smaller ones placed on edge and using the same tie rods, would 
support the kiln very much better and the life of the kiln would be 
greatly prolonged. The proper staying of a rectangular kiln is of vital 
importance to its durability. 

The time of burning this kiln at Detroit is rather remarkable, being 
about thirty hours from the time of lighting. The temperature is car- 
ried to Seger cone 06. Rarely does the time exceed thirty-five hours. 

There are several reasons for this very short time of burning: First, 
the clay will stand rapid firing; second, the fuel used permits steady 
firing with no time lest for ckening fires, the oil being vaporized by 
steam; third, the excellent draft in the kiln, maintained by a fan. The 
same conditions could no doubt be obtained with natural draft, but it 
would have to be very strong, and a tall stack would be needed. 

Mound Qty Kxin* — A kiln is being used at the Mound City 
Roofing Tile Company at St. Louis, which differs from any other in 
use in the country. It was designed as a continuous kiln, but owing 
to failure to get satisfactory results from it, its continuous features 
have been abandoned and the kiln is now used as a compound periodic. 
It greatly resembles the Dunnachie continuous kiln which was erected 
in two or three places in this country about twenty years ago, and 
wliich also failed as a continuous kiln and was ultimately used as a 
set of independent units. The Mound City kiln is built in block form, 
consisting of a double row of chambers four to a row, or eight chambers 
in all. Each chamber is approximately fifteen feet wide and eighteen 
feet long. It is fired by four flat grate furnaces, two on either end of 
each chamber. The two rows of chambers are placed about twenty-five 
feet apart, so that there is ample room for firing between the rows. 
Doors are placed at each end of the chambers so that the setting can 
be done from one side and the drawing from the other. 

As originally designed, the heat from a burning chamber was to be 
carried forward through the next chamber ahead, and then out into the 
main draft flue. The furnaces are built into the walls as in ordinary 
down-draft kilns. The heat generated in the furnaces is conducted well 
up into the chamber by high bag walls. After passing down through 
the ware, it reaches the floor, which is covered with regular open floor 
bricks. These floor bricks cover lateral floors extending from end to end 
of each chamber, and at the center connecting with a larger cross-flue. 
This latter flue in turn has a 'T" connection to the main draft flue 
leading to the stack or fan. In the case of the Mound City Roofing Tile 
Company a mechanical draft fan is used. 

The kiln to be operated on the continuous plan should be so de- 
signed that the heat from the first chamber would pass down through 
the floor as usual, and then b}*^ flues should be carried forward and enter 
the bags of the second chamber. It would then pass through the ware 
of chamber 2, and out to the draft fan at once; or, if conditions permitted. 



GEOLOGICAL SURVEY OF OHIO. 409 

it should be carried through the third chamber as well. Upon reaching 
the end chamber of one row, the heat should be carried across the in- 
tervening space by a connecting flue, and enter the bags of the opposite 
chamber on the other row. 

Advantages. — First. Only a small yard space is required, the 
chambers being arranged in the most compact form. Second. The kiln 
is cheaper to construct than an equal number of individual kilns on 
account of saving one wall for each chamber except th(3 first; also, the 
cost of building a shed over the kiln is greatl}^ reduced, on account of 
its compactness. Third. It can be built in any size to begin with, and 
then can be extended by the additions of new chambers as occasion 
demands, without any interference with the original chambers. 

This kiln could easily be so arranged that it could either be operated 
in separate periodic units, or for most of the time as a partially contin- 
uous kiln. 

For some reasons the continuous kiln proper is more desirable than 
the above, but for the average roofing tile plant, making a large variety 
of ware and possibly not operating continuously, the latter is to be 
preferred. One chamber can be operated at a time, or all at once, to 
suit the output. With the true continuous kiln the amount of ware 
set and drawn each day must be very closely regulated. While the 
fuel consumption in the partially continuous kiln will, of course, be 
greater than in the regular continuous kilns, this does not offset the 
conveniences above pointed out. It is so much more economical than 
ordinary periodic kilns that its use should be attractive in many quarters. 

CONTINUOUS KILNS. 

In the ordinary periodic kiln the waste of fuel is prodigious. The 
gases passing out of the kiln are discharged into the atmosphere at 
a temperature but little below that of the ware itself, and their heat 
is lost. The kiln, on reaching its finishing point, contains a great 
quantity of heat stored up in the wares, its walls, roof and floors and 
fire-places. This, also, is commonly thrown into the atmosphere and 
wasted. In recent years a part of the waste heat of cooling is often 
utilized for drying purposes, but under the best conditions there is still 
a heavy heat loss in cooling. 

The continuous kiln in its fundamental form seeks to obviate these 
two sources of heat loss — first, by using the hot products of combustion 
through chamber after chamber until they become so cold as to be 
useless; second, by using the heat of cooling chambers to pre-heat 
the air currents passing into the kiln, so that the amount of fuel 
needed to raise the temperature of these currents to the highest tem- 
perature required in the burning of the clay wares is only a small amount. 
No more thoroughly economical device than the continuous kiln for ac- 



410 BULLETIN ELEVEN 

complishing a thermal reaction on a large scale is to be found in the 
field of metallurgical or ceramic engineering. 

Only one plant in America is using a continuous kiln exclusively 
for the burning of roofing tile, viz., The Ludowici-Celadon Company, 
at Chicago Heights, 111. It has had a continuous kiln for several 
years. The Alfred Clay Company, Alfred, N. Y., also has a contin- 
uous kiln, but is using it more for the burning of pressed bricks than 
for roofing tiles. The latter are nested in among the bricks when burnt 
in this kiln. 

A true continuous kiln is constructed in ring form, or at least a 
closed loop of some sort. It may be circular, oval, oblong or square, 
and even have parallel chambers connected across the adjacent ends to 
establish the circuit. It may be a continuous tunnel, or a row of com- 
partments separated by cross-walls and connected by flues. The cross 
section of the tunnel or compartment may be as little as eight feet 
by ten feet, or as much as twelve feet by forty feet. Where the 
chamber form is used, the arches may be turned lengthwise or cross- 
wise — the latter is usual. It is necessary to construct very thick but- 
tresses at the end walls or side walls to hold the strain of the arches, 
or else other means of bracing. Where the kiln is one continuous 
chamber the arch is continuous with the kiln chamber. In this case 
it is better to brace the entire side wall of the kiln very strongly 
with *'I'' beams and cross tie-rods in order to carry the side thrust. 

The kiln at Chicago Heights is a considerably modified Hoffman 
kiln. The firing is done entirely from the top of the kiln, through 
small fuel holes spaced equally over the top of the chamber, about four 
feet apart. Directly under each of these fuel holes it is usual to build 
a kind of chimney of checker brick work, from bottom to top, so that 
the fuel, which in these instances is fine coal, when fed into the firing 
hole, rattles down through the checker work, lodging as it goes and 
burning where it lodges. 

In these kilns the tunnel is not cut up into lengths by cross-walls, 
or even dropped arches in the roof to mark off the length of the cham- 
bers. Hence it is usual to consider the distance from door to door 
as a chamber. The doors usually open through the kiln walls at about 
twentv foot intervals. 

It is usual in operating a kiln of this kind to set one or two chambers 
each day. At the end of each chamber it is necessary to form some 
sort of draft regulator. For this purpose a temporary partition is made , 
of light strips of wood, upon which a cheap and rather heavy paper is 
fastened in place, often daubing the joints with soft clay. This parti-, 
tion must close the entire cross-section of the kiln. When the paper 
partition is in place, the setting begins again until the proper distance 
is reached for a second paper partition, which is then put up, and thus 
the setting goes on. 



GEOLOGICAL SURVEY OF OHIO. 411 

In the side wall or floor of the kilns, short connecting flues open 
into the principal duct leading to the stack, or fan when one is used. 
This duct may be below the floor, or in either side wall, or even in the 
roof of the kiln, but the commonest construction is to make the main 
tunnel in two parallel sections, connected across the ends by smaller 
flues, and arranging the draft duct between the two tunnels, so that 
connection with it can be made freely from either side. These con- 
nections between the tunnels and the draft duct are provided with 
valves, or slide dampers, by which the connection can be opened, or 
shut, or regulated. • * 

When the gases from the fire have traveled through the tunnel to 
the point where they become cooled down nearly to their dew point, 
the valve in one of the connecting ducts is opened, and they are carried 
off through the main draft duct. The paper partitions burn away 
when the heat gets sufficient, and as each partition disappears the draft 
valve next ahead of it is opened to carry the gases into the new chamber 
just connected. 

The length of tunnel under operation at once varies, but usually 
is the equivalent of seven, eight or nine chamber lengths, or from one 
hundred and forty to two hundred feet. In some kilns this may be 
shortened down somewhat, but less than one hundred and forty feet 
is apt to mean that the fullest heat economy is not being attained. The 
number of chambers ahead (i. e., in the direction the draft is going) of 
the firing chamber is usually four or five. Three is too few and rarely 
can the gases be passed through more than five chambers, or an equiva- 
lent length of straight tunnel, without being chilled to their dew point, 
beyond which it is not feasible to use them without heavy damages 
from staining, scumming, efflorescences, kiln marking, etc. The number 
of chambers (or equivalent length of tunnel) behind the firing chamber 
is usually three to five, the number depending on the temperature of 
the incoming air. 

The air passing through the cooling wares can usually be brought 
to a temperature of 900° to 1000° C, before any fuel is used in heating 
it to a higher point in the firing chamber. The gases passing from the 
firing chamber usually drop in temperature from the finishing point to 
about 900° to 1000° C. in the first chamber, 600° to 700° in the second, 
300° to 400° in the third, 100° to 200° in the fourth, and 50° to 125° in 
the fifth. 

The fuel used is from one-fifth to one-third of the amount used in 
an ordinary periodic kiln of good construction. One quarter represents 
the average amount. 

In the foreign countries where fuel is very expensive, the con- 
tinuous kiln now has the most frequent use. All classes of ware, from 
the most common brick to porcelain, are burned in continuous kilns. 
It was stated by one of the firms mentioned above that their continuous 



412 BULLETIN ELEVEN 

kiln was carried through a month's burning on a single car load of slack 
coal, weighing about thirty-five tons. However, this figure would 
vary widely with the necessary temperature to be obtained, the weight 
of the wares to be heated, etc. 

The greatest objection to the continuous tunnel kiln is the lack 
of control over the course of the draft. The natural tendency of heated 
air is to rise, and as the draft in the kiln is necessarily horizontal, the 
gases are sure to tend to flow along the top or crown of the kiln, over- 
burning the ware at the level and underfiring the lower portion of the 
setting. 

Another trouble, often serious for the manufacturer, occurs in the 
tunnel kilns. The usual mode of firing is by dropping the fine coal or 
"slack'' through holes in the roof, through the vertical checker-work 
flues before mentioned. The rapid combustion of the coal in small 
pieces, especially at temperatures below the highest reached, tends to 
liberate the coal ash in feathery, flying particles, which are picked up 
by the draft and carried along, lodging in eddies of the draft on the 
surface of the ware. All coals do not cause this difficulty equally. Some 
tend to fuse and stick together, and in this case the difficulty takes a 
new form — that of cleaning and reusing the checkers. The expense of 
setting up and taking down the checker work is to be considered also. 
With a kiln of this type it is a very difficult problem to burn glazed 
ware, largely due to the dust or ash settling on the sticky surface of the 
molten glaze. 

Haig^h Kfln* — The Haigh Kiln is one of the continuous variety, 
but it differs from most others in that the fuel is fed into fire holes on 
the exterior of the kiln wall, instead of being dropped in among the 
ware as just described. The kiln is usually built in a U shape, with 
duct connecting the two extremities. This open court permits of having 
doors for loading and unloading the kiln on both sides of the tunnel, 
and as the tunnel is fired from both the top and the sides it permits 
of an equal distribution of the heat over the cross section. The cham- 
bers are marked off by drop arches which come down into the kiln a 
matter of a foot or more, and act as a check or baffle to the gases flow- 
ing along the crown of the arch. The side firing is advantageous, in 
that it has a tendency to help bring up the temperature of the floor of 
the kiln equal to that at the top. 

The same objections apply in general to the Haigh kiln as to the 
kiln first described, but it has some advantages over the other in the 
ease of heat distribution and less flying ash. 

As stated earlier, the Haigh kiln in this particular instance is being 
used for burning roofing tiles and dry-press bricks in the same chamber. 
This is a practice not to be endorsed. Clay which has been worked in 
the plastic condition will develop a vitreous structure at a lower temper- 
ature than the same clay worked by the dry process. And again a thin 



GEOLOGICAL SURVEY OF OHIO. 413 

piece of clay ware can be fired in a shorter time than a thick piece. 
Hence, the idea of nesting thin plastic wares like tiles among dry pressed 
bricks, and expecting to burn both at the same time, is entirely wrong. 
One or the other must suffer as a result. It would be much better to 
set one chamber of bricks and another with tiles, for then each ware 
could be given a somewhat modified treatment in firing. 

In summing up, neither of the continuous kilns mentioned can be 
said to be doing particularly high grade work in burning roofing tiles, 
but there is no reason why the continuous kiln cannot be made ideal for 
the burning of roofing tiles in this country as well as in Germany and 
France. 

The proper kiln should be rather low, and not very wide; the fuel 
must not be distributed among the ware, but should be burned in sep- 
arate furnaces,, and fed to the kiln chamber as a gas. 

The draft must be under full control by dampers, and should be 
created mechanically, so that it can be made constant or varied at will. 
The cooling chambers should be so arranged as to furnish heat for the 
drying and to assist in warming up the newly set tiles, before the com- 
bustion products are admitted to them. While the continuous kiln 
composed of separate chambers is more expensive to build and keep 
in repair, it will be found better for the burning of roofing tiles. The 
construction of a continuous kiln should be in the hands of a properly 
trained engineer. The problems involved are too numerous and varied 
to make it at all a safe thing for a clay worker to attempt, unless pre- 
pared as a constructing engineer. 

SUMMARY* 

In considering the best type of kiln for a roofing tile plant, the 
size of the plant and the provision for the regularity of operation are 
naturally of paramount importance. For small plants, with but little 
capital, and without means for storing up a winter's supply, or wet 
weather supply of clay, investment in a continuous kiln would 
not be at all warranted. It must be kept in constant operation, or 
its economy and its convenience disappear. The small, cheap, and 
autonomous periodic kiln has far the advantage for such a plant, even 
though it uses three or four times as much fuel. Among the periodic 
kilns, the rectangular are to be preferred to the round, on account of 
economy of space in setting. The draft distribution can be made 
virtually as good, and the slightly increased losses of radiation and 
slightly more costly building of the kiln will not be serious items in 
the cost of the product. 

In large plants with ample capital, good clay storage, or a supply 
independent of weather, the continuous kiln, with all of the best devices 
for preventing poor draft distribution, using waste heat of cooling ahead 



414 . BULLETIN ELEVEN 

of the combustion gases, using furnaces which will prevent flying ash, 
and using mechanical draft, is unquestionably the proper one to 
install. The reduction in the cost of burning is what should control, 
where quality is not at the same time sacrificed. The roofing tile man- 
ufacturer, in order to compete with lower-priced roofing materials, 
will soon be compelled to make tiles cheaper than can be done in many 
existing plants. 

The final cost of production can generally be best reduced by 
studying to handle the burning with ease and certainty and with the 
minimum quantity of fuel of the less expensive sorts. 



GEOLOGICAL aUKVEX OF OHIO. 41 5 



CHAPTER X. 

RCX)FING TILE SLIPS AND GLAZES. 

The coloring or glazing of roofing is not at all new. The art dates 
far back into history. Probably the oldest example we have of glazed 
tiles, are those from the temple of Hera, which was built about one 
thousand years B. C* According to Graeber, in a memoir, these old 
tiles were covered with a black glaze. It is probable that the cover- 
ing was a black slip like that used on Grecian pottery, and not a true 
glaze, as understood today. 

Kashiwagi,' a Japanese antiquarian, of Tokio, has records of a 
green glazed tile of the normal pattern, which he claims is over one 
thousand years old. Morse also records the finding of tiles covered 
with a brown glaze at Bizen, Japan, known to have been made at least 
two centuries ago. 

Persian' roofs from the thirteenth to the fifteenth centuries were 
covered with highly glazed tiles. While a few glazed tiles have been 
made in this country for many years, it has only been within the past 
decade that any particular attention has been given to the subject. 
With the introduction of polychrome architecture, there has been an 
increasing demand for glazed tiles in the various colors, largely greens. 

SUPS AND ENGOBES* 

The coatings known as slips (in German and French, engobes) 
and those known as glazes, differ merely in degree of fusion. A slip 
is a coating, applied to a clay ware, which does not fuse in the subse- 
quent burning process. It is usually a clay, or a mixture of natural 
clays, which on firing, preserves a burnt clay texture on its surface and 
fracture, and does not soften to the point of flowing, or assume the 
smooth surface of a fluid. It may be soft and porous, or steel-hard, 
or even vitreous, but its changes have been such as occur without flowing, 
or mingling by movement while at high temperatures. As stated before, 
slips as a rule are natural clays or mixtures of such, which vitrify at 
low temperatures, forming a more or less impervious coating. The 
purpose of a slip may be two-fold: 1st, to give a desirable color to a 
clay of otherwise undesirable color; 2nd, it may be used to give 
a smoother surface by filling up irregularities, and thus getting a tile 
which will remain clean longer. 

^Morse, E. S. American Arch. & Builder, 1892. Vol, 36, p. 7. 

^Ibid. Vol. 36 p. 5. 

^Encyclopedia Brittanica. Ninth Edition, Vol. XXIII, p. 389. 



416 BULLETIN ELEVEN 

Roofing tile plants using calcareous, glacial or alluvial clays, which 
on burning develop a light-pink, buff or greenish mustard color, are 
practically compelled to make use of slips to mask or cover the surface 
of their wares. 

Natural Slip Clays* — For ordinary slip coloring, the requirement 
is for a clay which will easily disintegrate and beat up to a state of 
fluid suspension in water; which is naturally very fine grained; which 
will not shrink too much in drying, and hence will not crack or peel 
when applied in a thin coat to another clay already partly or wholly 
dried; which possesses a fine red color, when matured at a low tem- 
terature (900° C. or below), and remains good to as high a temperature 
as the body to which it is to be applied will require in burning; which 
develops a more or less glossy, but not glassy, surface; which will natur- 
ally wash clean by rains and offer the minimum opportunity for the 
lodgment of soot and dirt. Such clays are not common, and when 
found, acquire a certain value as a commercial commodity, being bought 
and sold by the ton or barrel. Good ones are sometimes even imported 
from Europe. 

Two of the American plants are using the Helmstedt clay from 
Germany, which burns to a fine red at a low temperature. To cheapen 
the cost of the slips it has been the practice of late to substitute a part 
of the foreign material by some local clays. There is no reason why 
slips composed wholly of local clays could not be used. Two clays 
have been tried in an experimental way in the Department of Ceramic 
Engineering of the Ohio State University with promising results. One 
is found a few miles east of Columbus, and is known as the Bedford 
shale. The other is a soft shale from South Webster, Ohio. Both clays, 
when made into slips, burn to a very beautiful cherry-red color at their 
respective finishing points. The Bedford shale has a longer heat range 
than the South Webster shale. The drying shrinkage in each case is 
a little high, but by using a part of the clay in a calcined condition, 
and ground to an impalpable powder, this point could be corrected to 
fit any average roofing tile clay. While the Bedford shale in the quarry 
is in so hard a condition that it would need grinding and screening 
before it could be blunged into a slip, the weathered outcrop of it will 
often yield great quantities of fine soft clay which will blunge without 
grinding. The South Webster shale, as seen so far, could be blunged 
into a slip direct from the pit, but it would also probably need grinding 
when mined well under cover. 

The usual practice at plants where slip clays are used is to ship in 
a considerable quantity of their slip clay once or twice a year, and store 
it in a dry condition, each day taking what is needed. This is put into 
a blunger, where water is added, and the charge blunged or stirred 
until the clay is thoroughly broken up and suspended in a thin, creamy 
condition. It is then sieved through a screen of from forty to one hun- 



GEOLOGICAL SUEVEY OF OHIO. 41 7 

dred meshes per lineal inch, and stored in barrels or tubs, where it is 
allowed to settle. The supernatant water is then tapped off until the 
slip has the proper density. This varies, however, with each clay. A 
tub of the prepared slip is placed upon a bench at the end of the dryer, 
from whence the dry tiles are being taken. In some cases the slip is 
poured over the outer or face side of the tile only, by means of a dipper. 
In other cases the entire tile is immersed in the slip for an instant, not 
long enough to soften, but long enough for a layer of the suspended 
clay particles to be deposited on the tile by the absorption of the water. 
As soon as the tile is removed the water soaks into the tile, and it ap- 
parently dries, usually in a minute or two. The tiles then go direct to 
the kiln for setting. 

In the past much controversy has occurred over the use of slips. 
This has come very largely from faulty slips and the misuse of the same. 
There can be no more objection raised to the use of slip clay on a tile 
than there can to the use of a true glaze, and in some respects not so 
much. The slip coat should be used as a true means of decoration, how- 
ever, and not to hide a poor tile. 

The application of a slip coat over the surface of a whitewashed 
tile is sure to end with bad results. The scum acts as an insulating 
barrier to the slip, preventing it from coming in contact with and 
fluxing fast ta the tile body. Hence, in a short time after such a tile is 
exposed to the weather, water gets beneath the slip, and on freezing, 
shells or pushes it off. A very noticeable example of this defect can be 
seen on the roof of the Art Museum in Eden Park, Cincinnati, Ohio. 

It has been claimed by makers of slipped tiles that their product 
does not become dirty on the roof as unslipped tiles do. This point 
applies chiefly to tiles of porous body. It does not apply to strictly 
vitrified tiles, which wash as clean with rain as any clay surface, glazed 
or unglazed. 

The reason that a slipped porous tile will remain clean is that the 
slip, on becoming vitreous, or vitrified, acts in a sense like a glaze, 
allowing the tile to be washed clean by rains. 

If for any reason a manufacturer has selected a clay which in itself 
does not burn to a good color, but otherwise makes a sound, perfect 
tile, there can be but one objection to his using a slip to give him a red 
color, viz., the chipping of the tiles in transportation and handling re- 
veals the body color beneath the red surface, and makes an unsightly 
blotch on the color. This objection holds equally true for any kind of 
superficial coat, glaze, enamel or slip. The objection is of much more 
real weight in pottery and other wares which are to be handled at close 
range, than to a roofing tile or building terra cotta, which is ordinarily 
so far removed from the eye that small imperfections become invisible. 
Much injustice has sometimes been done in applying too exacting stand- 

27— a. B. 11, 



418 BULLETIN ELEVEN 

ards to the judging of these wares. Obviously the soundness of the 
body and the appearance of the product when in position are the two 
important criteria, and defects which cannot be recognized or seen, and 
which have no effect on the life of the product, should be ignored. 
On the other hand, there are strong economical objections to slipping — 
the cost of the slip clay itself, its preparation, the expense of applying the 
same, with the resultant breakage of a percentage of the tiles, which 
will certainly take place during the shipping, are all to be considered. 
There are so many natural red burning clays of excellent color that it 
would seem entirely unjustifiable to locate on and use a clay for roofing 
tiles which must be given a coating of slip to cover up its poor color. In 
localities where natural red burning clays are lacking it may be justi- 
fiable, but not elsewhere. The plants now compelled to use a slip on 
their tiles were in most cases established without adequate knowledge of 
the roofing tile business or of the clays they were to use, and the present 
owners as a rule have bought the plants in at forced sales after heavy 
losses had been incurred by their projectors. The present owners have, 
therefore, to make the best of what they have, and use slip as one way 
of doing so. 

The use of a clay naturally burning to any other color than red is 
not known in the American roofing tile industry. It is a very common 
and important process in terra cotta manufacture, where every shade 
of browns, grays, yellows, whites and speckled mixtures of the same 
are used. There is not much more difficulty in obtaining clays which 
will form desirable light-burning slips than for red-burning slips, but 
, the market now offers no opening for such materials. 

Artificially Colored Slips* — The commonest practice in coloring 
slips has been to attempt to produce a better red color by use of oxide 
of iron in the slip. Sometimes salts of iron, like copperas, are employed. 
As a rule such attempts fail, either when applied to the slip coating 
alone, or to the entire body of the clay. As a rule the expense of such 
a course is too great, and the results are not satisfactory as to the color 
obtained. Instead of getting a good red, most generally a brownish 
or dirty gray is secured. Red oxide of iron changes to dark brown or 
black on heating, and does not act as a red pigment. Iron can be intro- 
duced in other forms which will color a clay red, but its use is costly 
and also leads to other defects. Manganese oxide can be used with 
success, but the color produced is dark, not red, and the expense again 
comes into serious consideration. 

The use of colored slips other than red for roofing tiles has been 
up to the present practically unheard of. One plant. The Bennett 
Roofing Tile Company, of Baltimore, produced on a small scale a 
few shades of green in true slips, during the latter part of its career, 
but at no other plant was anything of this sort being attempted in 190S. 



GEOLOGICAL SURVEY OF OHIO. 419 

The use of colored slips for roofing tile is sure to come, however, and 
with its advent will be opened up a wonderful field for polychrome 
decoration to the architect. With colored slips, a soft delicate appear- 
ance, so much desired and but poorly imitated by most glazes, is avail- 
able. Where stained wooden shingles are now used for roofing and 
siding purposes, it will be possible to use an everlasting absolutely non- 
fading material. 

For dark colored slips, such as brow^ns and blacks, the same clay 
that is being used for the body of the tiles, or any good red-burning slip 
clay may be used. By blunging into this clay, or better still grinding 
the clay to a cream with various per cents, of iron oxide for the browns, 
and with manganese oxide and a small amount of cobalt oxide for the 
blacks, these colors are readily secured. 

The amount of coloring matter will depend upon its source and 
fineness of grain. For oxide of iron, there are two sources of supply j first, 
the natural red hematite or limonite ores, which yield a fine red color 
when ground to a powder. Of these the **Clinton Metallic," ground 
from the fossil Clinton iron ore of New York state, is an excellent type. 
There are several such on the market. Analysis of this ore, as furnished 
in ground condition for "mortar colors" and similar uses is — 

Siliceous matter 15.37 

Aluminium Oxide 4 42 

Ferric Oxide 62.08 

Calcium Oxide 6.85 

Magnesium Oxide : 3«1 5 

Water and Carbonic Acid 8.08 

Total 99.95 

Second. ''Venetian red" is produced by the calcination at low tem- 
peratures of ferrous sulphate, or copperas, or iron vitriol, which is a by- 
product in enormous quantities in the pickling vats of tin-plate mills. 
This copperas at lowered heat gives off its water and sulphuric acid and 
the spongy ferrous oxide remaining oxidizes into red ferric oxide, of 
great beauty of color. It is, however, always impregnated with un- 
decomposed sulphuric acid salts, and is a fruitful cause of scumming 
in consequence. In composition, it is nearly pure ferric oxide, but its 
impurities are very detrimental. 

Manganese oxide can be obtained in abundance from a number of 
dealers in heavy chemicals in this country. It is prepared for the brick 
trade, especially, in sizes ranging from twenty to thirty mesh granular 
powder, up to the finest floated pulp w^hich cannot be measured by a 
screen. The commonly used sizes are twenty to thirty, forty to fifty, 
sixty to seventy, ninety to one hundred; and the floated or paste form. 
These powders are mostly ground ores of manganese, pyrolusitc, 
wad, or psilomelane. They vary pretty widely in composition, not 



420 



BULLETIN ELEVEN 



only from brand to brand, but also in the same brand. The most reliable 
brands are said to be English and German, which vary very little in 
their character. The American producers can undoubtedly produce 
an article of the same quality and uniformity whenever they appre- 
ciate the necessity of doing so. Up to the present, they do not all 
seem to see the need of strict uniformity and chemical control of their 
output. 

The composition of a standard brand on the market, as fur- 
nished by the courtesy of The Harshaw, Fuller & Goodwin Co., of Cleve- 
land, Ohio, is as follows : 

Analysis of Manganese Oxide. 



Ingredients. 



Peroxide of Manganese . 
Protoxide of Manganese 

Peroxide of Iron 

Oxide of Lead 

Oxide of Copper 

Oxide of Nickel 

Alumina 

Barytes 

Lime 

Magnesia 

Potash 

Soda 

Silica 

Carbonic Acid 

Sulphuric Acid 

Phosphoric Acid 

Arsenic 

Combined water 

Totals 



Ordinary. 


Selected. 


84.44% 


85.42% 


0.50% 


0.83% 


0.93% 


0.86% 


None 


None 


0.02% 


0.02% 


0.05% 


0.05% 


1.71% 


1.06% 


1.21% 


1.41% 


1.15% 


0.88% 


0.18% 


0.04% 


0.22% 


0.21% 


0.68% 


0.58% 


5.60% 


5.45% 


0.70% 


0.50% 


0.418% 


0.555% 


0.360% 


0.330% 


None 


None 


1.90% 


1.75% 


100.068% 


99.945% 



For the other colors, such as buff, yellow, blue, green, gray, white, 
etc., it is necessary to start with light or white-burning materials as a 
base, to which the various coloring oxides can be added to give the 
desired color. 

The first problem is to prepare a white engobe or slip which will fit 
the roofing tile body and at the same time vitrify suff;ciently to cause 
it to adhere tightly. It must not be so vitreous as to have a glassy 
surface or sheen. 

An ordinary white engobe prepared of the following ingredients 
will require a much higher temperature to vitrify it than the average 
red-burning roofing clay will stani 

Kaolin 150 

Flint 100 

Feldspar 50 



GEOLOGICAL SUE VET OF OHIO. 421 

Hence, to soften it down to a point where it will vitrify at the 
desired temperature, a flux must be added. The one most available 
is some form of lead, either white lead (the basic carbonate) or an oxide, 
like red lead. Other ingredients, such as lime, more feldspar, or feld- 
spar of more fusible variety, may be added to assist in lowering the 
vitrification temperature, but they are not sufficient without the use 
of lead. 

After a white engobe has been obtained which will sufficiently 
mature and harden at the rather low temperatures at which the red 
roofing tile body-clays mature, and which fits the body as to shrinkage, 
the production from it of a series of colored engobes is a comparatively 
simple task. It is only necessary to add the raw coloring oxides to 
the base engobe, grind them fine together, and apply as an ordinary 
slip. The great advantage in favor of using slips instead of glazes is 
that the tiles can be faced or set in the usual way, no attention being 
necessary to prevent them from sticking. For other reasons to be 
discussed later, it is firmly believed and strongly advocated that the 
roofing tile manufacturer should devote more attention to slips than 
to any other mode of tile decoration or coloration. 

At the laboratory of the Department of Ceramic Engineering of 
the Ohio State University, slips of a few of the more common colors 
have been developed with good success after being fired in an experi- 
mental way in the University kilns, and finally in the actual roofing 
tile kilns at several plants. It is deemed safe to give them out as 
starting points for others to use in developing similar slips for their 
own purposes. 

Base Engobe. 

White Lead (basic Carbonate of Lead) 17.80 

Soda Feldspar from the Sparvetta Co 25.40 

English Whiting (Carbonate of Calcium) 1.90 

Edgars Washed Florida Kaolin 39.70 

Golding's Ground Silica (Potters' Flint) 15.20 

100.00 

This mixture, well ground together in ball mills, and passed through 
a one hundred-mesh screen and fired at cone 02, becomes steel-hard, 
though it does not run or fuse in the least. It is of a creamy white. 
A better white might be secured by varying the kaolin, and perhaps 
the other minerals above. Coloring oxides can be added, however, 
without being at all affected by the lack of purity of the white color 
of the base engobe. 

A good green was produced by adding ten per cent, (dry weight) 
oxide of chromium to the above base engobe. 

A good yellow was obtained by adding ten per cent, of oxide of 
uranium. 



422 BULLETIN ELEVEN 

A good light blue was produced with from two to three per cent, 
and a dark blue with six to eight per cent, of cobalt oxide. 

Some excellent greens were produced by blending various propor- 
ions of the uranium engobe with the chromium engobe. The colors 
obtained were yellow or olive greens. 

The amounts of the coloring oxides used in the above formulas 
are large, and hence the recipes would be expensive to use on a large 
scale. But the experiment has not been carried to its completion, 
and doubtless great improvements can still be made. For instance, 
instead of using the pure oxides direct, it would be better to mix them 
with glass-forming materials, and fuse them into a melt or fritt. These 
fritts, containing from twenty-five to fifty per cent, of the coloring 
oxide, and being themselves of a fusible nature, could then be ground 
to a very fine powder and added to the engobe. The result would 
undoubtedly be to obtain a more lively color with much less coloring 
oxide, and resulting economy. The details of these fritts have not 
been worked out, but in general, if soda, borax, a little lead, and a 
little potters' flint be used as a flux, the coloring oxides will dissolve 
or amalgamate freely. The proportion can be easily worked out by 
a few trials. The melting should be done in crucible furnaces where 
the materials can be kept covered and kept under treatment as long 
or short a time as is needed. The melts should be poured into water 
to crackle, then dried, and ground to an impalpable powder before use. 

The work of properly fritting and making colored slips or glazes 
should be in the hands of a competent person, who has had training 
in ceramic chemistry. If the work is carried on in a systematic and 
economical manner, much money can be annually saved, which is now 
wasted in obtaining ceramic colors without a knowledge of the proper 
ingredients. 

GLAZES. 

The fundamental requirement of a glaze, as distinguishing it from 
a slip, is its fusibility at the working temperature. A hard glaze suit- 
able for a body requiring a high fire, might act as a slip if applied to 
another body maturing many cones lower, and so also, a satisfactory 
mixture for a slip at a low heat, might fuse to a glaze if carried much 
too high. But, if the substance is not more than a vitrified solid when 
finished, it is a slip, and if it has been fused, it is a glaze. Of course, 
there are all manner of intermediates, which it is difficult to refer to 
either class with certainty. 

Glazes are divisible into two main groups — the bright or glassy 
and the dull or stony. The former include the transparent glassy 
glazes, of the kind employed in table wares, and the opaque glazes 
known as enamels. The latter include the so-called matt glazes, and 



GEOLOGICAL SUKVEY OF OHIO. 423 

certain others which are known as crystalline glazes, though they are also 
matt. Between the transparent brilliant glassy glazes, and the dead, 
lusterless stony matt glazes, ever}'^ possible gradation of luster,color,and 
surface texture may be found or produced, and it is impossible to classify 
all of these intermediates with accuracy into either one or the other of 
these divisions. 

Bright Glazes. — These glazes are the common or typical kind of 
silicate surface coating. For a long time the}' were almost the only 
kind made. Dull or matt glazes were only produced as failures 
in the attempt to get bright ones. But as has happened many times 
before, man has converted his failures into successes, and in the last 
few years the use of the dull glaze has greatly increased. From the ar- 
tistic point of view, as a coating for roofing purposes, bright glazes 
are now considered a complete failure. The reflection of light from 
their mirror-like surfaces is so strong under ordinary conditions that it 
is impossible to look at the roof, except at certain angles. The color 
cannot be seen at all, except on dull days or from special points of 
view. This very practical difficulty led to the introduction of the 
matt or dull glaze into the roofing tile field. 

Nevertheless, roofs have been covered with bright glazed tiles, 
and doubtless will be again. The general type of the glazes employed 
is known as the raw lead glaze, and usually the more fusible varieties 
are required, as the red burning tile clays mature at relatively low 
temperatures. 

Such glazes may be represented in chemical formulas as between 
the limits — 

1.00 to 0.50 PbOl r 

0.00 to 0.20 K^O SO. 10 to 0.25 Al^Oj^ 1.25 to 2.25 SiOg 

0.00 to 0.20 CaO J t 

Ihe ingredients most commonly employed in making such glazes 
are 

Red Lead or White Lead. 

Feldspar or Cornish Stone. 

Whiting 

China Clay or BaU Clay. 

Flint 

A typical raw lead glaze, falling within the above limits, which 
will melt and run bright at a temperature beginning about^ cone 08, 
and which will often remain good to a temperature as high as cone 02, 
has a formula as follows: 



0.85 PbO ^ r 

0.05 K-O ^0.10 AIA5 1-20 SiO„ 
0.10 CaO J I 



424 



BULLETIN ELEVEN 



This glaze (No. 1) could most easily be made up of the following in- 
gredients: 



White Lead 68.981 

Ground Feldspar 8.74 

Whiting 3.14 

China Clay 4.05 

Potters' Flint 15.09 



Unit weight 318. 



100.00 



Another typical raw lead glaze, which will mature at a little higher 
temperature, beginning at about cone 05 and remaining good to cone 
01 or 1, is as follows: 



0.70 PbO 
0.15 Kfi 
0.15 CaO 



0.20 ALjO, ]l.90 SiOj 



This glaze (No. 2) could most easily be made up of the following in- 
gredients: 



White Lead 52.10 

Ground Feldspar 24.00 

Whiting 4.50 

China Clay 3.80 

Potters' Flint 15.60 



Unit weight 345.9 



100.00 



A third typical raw lead glaze which will begin to mature at about 
cone 02, and will remain good to about cone 3 or 4 is as follows: 



0.60 PbO 1 
0.20 Kfi 
0.20 CaO 



0.25 AljjO, 



2.00 SiO, 



This glaze (No. 3) could most easily be made up of the following in- 
gredients: 



White Lead 45.401 

Ground Feldspar 32.61 

Whiting 5.86 

China Clay 3.78 

Potters' Flint 12.32 



Unit weight 340.9 



99.97 



By taking fractional parts of a unit weight of either glaze, any 
desired mean between any two may be obtained, viz: 



0.8 X 318 (unit weight of No. 1) 
0.2 X 340.9 (unit weight of No. 3) 



254.4 
68.18 

322.58 



which makes a glaze (No. 4) one-fifth of the way between the two ex- 
tremes, and which will be harder than No. 1 by about one-fifth of the 
difference in fusing point between No. 1 and No. 3. 



GEOLOGICAL SURVEY OF OHIO. 425 

With these starting points, a little experimenting will often lead to 
the production of a satisfactory simple, bright, raw-lead glaze. When 
the problem involves fitting the glaze to a body, and remedying crazing 
and other defects, or matching colors, the matter becomes too complex 
to deal with by rote, and it should be put into the hands of one acquaint- 
ed with the theory of the subject. 

These mixtures all mature at their respective temperatures to form 
bright transparent glazes. If applied over a red body, the red color will 
show through; if over a buff bod}^ the glaze will appear yellow, though 
the yellow is due to color of the buff body showing through the clear 
glaze. 

Should it be desired to make a glassy green glaze, using one of the 
above type glazes, it would only be necessary to add various per cents, of 
copper oxide. It will, however, be found impossible to produce satis- 
factury bright green transparent glazes over a red body direct. The red 
color of the body will show through and interfere with the desired color. 
To overcome this, it is necessary either to use an opaque glaze or enamel, 
or else first to slip the tiles with a white or buff slip or engobe and then 
apply the colored transparent glaze upon them. The true color of the 
glaze will then persist. 

The amount of copper oxide required to make one of the above 
glazes into a good strong green is about one and one-fourth per cent. 
Lighter tints are obtained of course with smaller quantities, even one- 
fourth per cent, will be quite clearly green, on a clear light background. 
No advantage will be found in running the copper higher than two per 
cent., unless it is desired to produce bluish ^^gunmetal" effects, in which 
case the amount may have to be three per cent, or above. 

A number of plants, are making a very satisfactory bright glaze, 
variously known as '*red brown," '*fox red,'^ ^'mahogany'* or ^*tea-pot.'' 
This glaze, to be at its best, should be applied on a body which naturally 
burns to a light red or pink, and requires a red slip to strengthen its 
color to a saleable point. 

The base of the glaze can be the same as any of those just given. To 
it is added one per cent., or a little less, of iron oxide, or better still from 
two to three per cent, of manganese oxide. The glaze when applied 
over the red slip coating of the tiles seems to dissolve or take into solution 
parts of the slip clay, thus allowing the color of the main tile-body to 
show through feebly in irregular streaks, while the parts not dissolved 
show a dark red color. The combination of the light and dark red 
presents the appearance of the grain to be seen in mahogany wood. 

These red-brown glazes nearly all show beautiful spangled crystals 
in places — not on ever}' tile, but in frequent instances. These crystals 
are due to the excess of the iron dissolved in the glaze. The glaze while 
fluid takes up the oxide of iron from the slip clay in- addition to what 



426 BULLETIN ELEVEN 

has already been added, and becomes supersaturated, so that upon 
cooling small glittering flakes of some iron compound crystallize out. 

Other colors which can also be produced from these same glazes 
are plain blue with oxide of cobalt, plain brown with oxide of manganese, 
and plain orange yellow with oxide of uranium. The cobalt is a very 
powerful oxide, and only a few tenths of a per cent, are needed. Uranium 
is also used sparingly on account of its cost. One per cent, or less is 
as much as would be used ordinarily. Manganese produces a fainter 
color and several per cent., even up to five per cent., may be needed. 
Of course, mixtures of the different oxides produce mixtures of their 
colors — cobalt and copper produce blue-greens; cobalt and iron produce 
black; cobalt and manganese produce purple, -etc. The field open to 
the experimenter in producing new shades is practically endless. 

Matt Glazes* — With the introduction of the dull glaze, which does 
away with the painful brilliance of the early types, has come a much 
wider use of glazed tile roofs. Color schemes are now possible which 
could not be realized with bright glazes, or which could not be seen even 
if produced. 

The true matt glaze is one .whose chemical composition is such 
that on cooling it cannot retain a glassy structure, but changes to a 
stony or crystallize(i mass instead. There is a group of matt glazes 
which are not to be distinguished readily from true matts, but which 
are merely immature or partially fused. These come very close to 
slips or engobes, though generally they are more completely fused than 
the latter. The true matts, however, are much more satisfactory to 
work with, have the widest temperature range, give the best colors and 
leave fewer defects in covering the ware properly. 

The surface of the true matt glaze is crystalline or rough, often not 
to the eye or the feel, but if examined closely %vith a glass it would be 
seen that the surface resembles the peel of an orange or an egg shell. 
This roughness causes an absorption or breaking up of rays of light, 
instead of a reflection back as from a mirror, so that what the eye 
sees is a solid mass of color, soft and velvet}'' to look at. 

The roofing tile manufacturers have not found it a very easy task 
to produce matt glazes of satisfactory color and surface texture, which 
would mature at the low temperatures at which they are mostly com- 
pelled to work. Matt glazes in other industries, maturing from cone 2 
up, are common, but the latter are expensive fritted glazes, not suitable 
for a product like roofing tiles. In order to bring the maturing point 
of the cheaper matt glazes down to about cone 06 or 05, more fluxing 
ingredients like lead oxide have had to be resorted to, and with this 
increase has come trouble from the glaze drying up through volatiliza- 
tion when fired in the open kilns, and also bright glazes are produced 
by a little extra heat, and the matts would.vary in degree of their matt- 
ness. 



GEOLOGICAL SURVEY OF OHIO. 427 

The following formulas have been tried on several roofing tile clays 
with a fair degree of success. They require about cone 02 to mature, 
which is a little higher than desirable: 

0.70 PbO 1 f 

0.10 K^O fO.34 AlaOg h.eosio, 

0.20 CuO J ( 

Add 0.10 to 0.12 CaO for color. 

This glaze (No. 5) can most readily be prepared by grinding 
together the following batch: 

White Lead 50.80 

Ground Feldspar 15.40 

Whiting 5.50 

China Clay 17.05 

Ground Flint 8.65 

Copper Oxide 2.60 

100.00 

This glaze gives a rather light green matt, which would be im- 
proved with a little more yellow color. 

A glaze which will mature at a slightly lower temperature, about 
cone 05, is given below. 



1.90 SiO^ 



0.45 PbO 

0.12 Kfi (0.28 AljO, 

0.35 CaO 

0.08 ZnO 

Add 0.12 CuO for color! 

This glaze (No. 6) could most readily be prepared by grinding 
together the following batch: 

White Lead 36.40 

Ground Feldspar 20.80 

Whiting 10.85 

Zinc Oxide 2.05 

China Clay 12.80 

Ground Flint 14.15 

Copper Oxide 2.95 

100.00 

This glaze produces a matt green, and on account of the lead con- 
tent being lower than No. 5, it should stand the heat treatment with less 
volatilization. If the copper oxide is left out of the glaze, it will be a 
rather yellowish white and not at all pleasing. In the place of the 
copper oxide various amounts of cobalt oxide may be added for blues, 
iron oxide and uranium oxide for yellows, manganese carbonate for 
purples and browns, and nickel oxide for gray. The amounts of the 
various oxides to use will vary, but aside from cobalt, which requires 
very little, the quantities are not ver}- dissimilar to the amount of 
copper used in the preceding batch. . 

Beside the production of matt glazes by the proper means; viz., 
proportioning the ingredients correctly and giving the glaze the proper 



428 BULLETIN ELEVEN 

heat treatment, there are a number of ways of dulling the surface of 
of a glaze and thus producing what for lack of a better name we may 
term artificial matts. One of these processes is to add raw sand or 
ground calcined clay into matt glazes in various per cents, givinc: the 
glaze a very rough and stony appearance. For some purposes this 
method, it is believed, has decided possibilities for good. In repro- 
ducing the moss-covered tiles so much admired in Europe, this is prob- 
ably a good mode of attack. 

A similar mode consists in artificially roughing the surface of the 
clay by cutting it with a wire, and allowing the rough surface formed 
by the dragging of the grains to remain unsmoothed. This of course 
could only be applied to flat tiles like shingles. 

Another method is the use of the sand blast on the surface of a 
bright glaze. The glass is cut away, leaving a rough dull finish, very 
much liked by many architects for certain color schemes. The blasting 
machine is the same as is used by the glass manufacturers in producing 
etched or frosted glass. It consists of nozzles through which a powerful 
current of compressed air is blown, carrying sharp glass sand in sus- 
pension. This sand strikes with such force that it readily cuts away 
the surface of any substance, metallic or non-metallic. The tiles to 
be treated are laid together the same as if placed on the roof, on an 
endless belt, which moves very slowly, carrying them under the nozzles 
of the blasting machine. The speed requisite to allow the sand to cut 
away the surface of the glaze as the tiles pass by is determined by 
experiment. The sand used must be renewed quite frequently, on 
account of its wearing away to dust under the severe treatment to 
which it is subjected. While this method is rather slow and costly, 
it gives a characteristic and not unpleasing finish. 

Another and very objectionable way of producing a matt finish 
was found in use at one plant. Tiles with bright glassy green glaze 
were being washed with hydro-fluoric acid, one of the most powerful 
and dangerous acids known, whose special peculiarity is its power to 
attack silicates. The vapors or fumes of this acid are an irritant poison, 
and for this reason its use should be permitted only under special con- 
ditions, with the most perfect ventilation, and every precaution for 
the safety and health of the employes. Its use under other conditions 
and without these safeguards is little short of criminal. 

This powerful acid when applied to a glazed surface at once attacks 
the silicates that have been formed, dissolving or disintegrating them 
until the surface is minutely rough or stony looking. 

It is a curious fact that in cut-glass factories this same acid is used 
for the exact opposite effect; i. e., for polishing a piece of glass which 
has a dull or frosted surface after it has been cut. The difference comes 
in the lack of homogeneity in the glaze, some parts dissolving so much 



GEOLOGICAL SURVEY OF OHIO. 429 

faster than others, while glass is practically all the same thing and 
dissolves about equally. 

The possession of the mere recipe or formula of a glaze which is 
in successful use in one plant is but a very small step toward the instal- 
lation of a successful glaze in another plant. Some glazes are in use 
which can be applied to wares of considerable variety, and at a con- 
siderable range of temperature. But this is not the common thing at 
all, and most glazes have to be operated under such special conditions 
that they woufci be practically useless if transferred without alteration 
to another works. They are often traded or sold as if they were a 
commodity of value, and then subsequent failure gives rise to ugly 
suspicions or charges of bad faith in the transfer, whereas, in fact, 
the causes of the failure are purely natural. 

The fitting of a glaze to a body, i. e., its adjustment so that its 
rate of contraction in cooling or its expansion in heating up are about 
like that of the body upon which it is borne, is one of the great stumbling 
blocks in the path of the glaze maker, amateur or professional. There 
are many factors entering into its settlement, but the commonest, 
most useful, and in most cases a sufficient mode of control is by va- 
riation of the silica content of the glaze. For instance, in Glaze No. 
2, if the glaze were cracking or "crazing'' on the wares when drawn from 
the kiln, the silica in the glaze might be cautiously increased. The 
higher the silica can be pushed, without sacrifice of other necessary 
properties, the safer the glaze is from this trouble. But too much silica 
might produce the reverse phenomenon of crazing, viz., ^'shivering," 
where the glaze flakes off, carrying chips of the body with it, and pro- 
ducing a very undesirable surface. The silica must be reduced to 
overcome this defect. These additions or subtractions of silica to a 
glaze may and probably will affect its melting point, and the results 
cannot be considered as proved until the glaze has been fired at the 
temperature it requires after its alteration. Very many errors are 
made in this way by glaze makers altering the glaze composition and 
failing to alter the heat treatment at the same time. 

Besides the question of being made to fit, it should also be so con- 
structed that it will have a relatively wide heat range; that is, it should 
remain workable and good over a considerable increase in temperature. 
In regular roofing tile kilns, the temperature from top to bottom some- 
times varies as much as two or three cones, and a like difference may 
exist from side to center of the kiln. It is plainly seen that a glaze 
which passes through maturity and becomes overfired within the tem- 
perature range of one or two cones, will not prove at all satisfactory 
under such burning conditions. There should be at least a range of 
four cones in which the glaze is good, and even more would be better. 

Mechanical Preparation of Glazes* — Every step in glaze production 
should be methodical and systematic. This does not mean that changes 



430 BULLETIN ELEVEN 

may not be introduced, but that changes must not be allowed to creep 
in without the knowledge or consent of the glaze-maker. 

Weighing Out. — Each ingredient should be w^eighed separately, 
one at a time, in a scoop or weighing box, and the weights counted 
and recounted. When dumped into a common receptacle, one ingre- 
dient on top of another, there is much more danger of the ingredients 
getting mixed in taking out excess quantities of one or the other. The 
sum of all the ingredients, after assembling all in one receptacle, should 
be retveighed and the collective weight of the batch should equal the theoretical 
sum of the individual weights of the various ingredients. If this cus- 
tom is kept until it becomes instinctive and unconscious, many serious 
errors in the mixing room will be avoided. 

Grinding GUues* — In general, it is- important that the ingredients 
of glazes should be most thoroughly blended by fine and intimate grind- 
ing together. Especially is this the case where coloring oxides are added 
raw to a glaze batch, because the glaze is almost certain to be "specky*' 
if not ground. In fact, a better way to insure the fine subdivision of the 
coloring matter is to grind it with a small quantity of glaze, or of some 
one ingredient of the glaze, separately, until impalpable when tested 
betw^een the teeth. 

The prepared color slip may now be added to the glaze, and with 
comparatively little grinding become well distributed. The function 
of the grinding is to secure uniformity in distribution and uniformity 
in fusion. With coarse particles of dissimilar minerals making the glaze, 
the effect would be crude and patchy. 

There have beenj and doubtless will be again, instances in which 
very interesting and admirable color effects and surface textures on 
glazed wares are obtained by the use of unground or poorly ground 
glazes, or where some one ingredient is left unground or added to the 
mill just before a charge of glaze is removed as finished. But, in the 
broad way, there can be no doubt that it pays, from the standpoint of 
cost and perfection of product, to reduce the glaze to a fine-grained, 
homogeneous state before uee. 

On the other hand, too fine grinding is possible. Glazes may be 
ground so fine that they will crack and shrink in drying on the surface 
of the ware like a fat clay would, and these marks may not heal over in 
the subsequent fusion. In general, if a glaze is ground long enough so 
that it will pass through a sieve of 150 meshes per lineal inch without 
leaving any residue on the sieve, it is fine enough. If raw coloring oxide? 
are to be added, they should be preground as fine as possible before add- 
ing to the glaze batch. This insures good color distribution, without 
necessitating such long grinding of the entire mass of the glaze. 

The mills for glaze grinding are of two types, the old, familiar 
buhr-stone type and the recent ball-mill type. There is difference of 
opinion among potters as to which produces the glaze at less cost 



GEOLOGICAL SURVEY OF OHIO. 431 

in grinding, fineness being equal. It would be a laborious problem to 
definitely settle this contention. But it is certain that the quality of 
the work done by either is good enough. The ball mills are steadily 
replacing the older type, chiefly on account of their convenience and 
ease of cleaning. 

Iron grinding mills, such as are used by paint grinders for incor- 
porating dry paints and oils or varnishes, are occasionally used by glaze 
grinders, and also iron-ball mills. 

For some colors, especially the dark ones, very little, if any, trouble 
would be experiencd from this practice, but for the light colors much 
trouble will result. The metallic iron of the mill is ground off by the 
continual rubbing of the discs or the impact of the balls, and enters at 
once into the glaze as a part of it. When the glaze is applied and melted, 
the iron will form specks and discolorations. 

Ball mills of large size should be lined with vitreous lining of stone- 
ware or porcelain bricks, while the smaller ones are usually made of 
solid porcelain jars. The balls used in large mills for the grinding of 
glazes are, as a rule, flint pebbles gathered on the beaches of northern 
France. These pebbles are usually oval in shape, well rounded, and vary 
in size from an inch to three inches in diameter. In the smaller mills 
the pebbles are usually marbles made of porcelain. The dust worn 
from the linings and pebbles of porcelain or flint-lined ball mills is com- 
posed of silica or silicates, and being similar to some of the ingredients 
of the glaze, is absorbed without ill results, but in unlined iron mills 
this is not the case. 

The consistency, or thickness, of the glaze slip is a matter of im- 
portance. If too thick it will form clots, or *'blobs," of glaze in spots and 
along edges and in corners. If too thin it will not form a thick enough 
coat without more than one dipping, and will thus cost more labor. 
No law can be laid dow^n, either in weight per pint or in specific gravity 
by hydrometer, by which a correct thickness can be determined. Dif- 
ferent glazes vary so much in ingredients that they do not weigh the 
same per pint when at exactly the same relative fluidity. P'or any sin- 
gle glaze, the w^eight or specific gravity is constant at the same fluidity, 
and these measures are easily available for the guidance of the men. 
The practical sense of the dipper is usually sufficient to keep the glaze 
about right in this respect. The application of the glaze to the ware is 
done in very much the same way as slips are applied. As the dry tiles 
come from the dryer, they are taken to the glaze room, where a large 
tub of the prepared glaze is ready. The tiles are then taken one by one, 
and coated on the outer surface by carefully pouring the glaze over them 
while held in a standing position, allowing the excess to drain back into 
the tub. The tiles are then placed on racks or shelves, to allow the glaze 
to dry sufficiently for handling. 



432 BULLETIN ELEVEN 

The Setting; of Glazed Roofing: Tiles* — Glazed roofing tiles are at 
present set in very much the same way as the unglazed. In plants where 
the unglazed wares are set solid, without fire-clay supports or boxes, 
the use of boxes for the glazed part of their output is general. Only 
one plant was found in which glazed tiles were set solid, without boxes, 
and the results in this case were of a very low grade. 

It is the usual practice to set the glazed goods in the lower half 
of the kiln, where they are more protected from the flame or flying coal 
ashes. 

Figure No. 167 shows the method of setting glazed tiles in a kiln 
where the balance of the ware is set without supports. 

General Discussion of Burning G>nditions« — The limiting condi- 
tions of the glazed roofing tile business today is the one-fire burn. Man- 
ufacturers want to produce their glazes in the same burn with the reg- 
ular waie. They think they are obliged to do this by the present pre- 
vailing prices for glazed tiles. The temperature required by roofing 
tile clay is usually relatively a low one, and the composition of the glazes 
that can be used is limited in consequence. None of the roofing tile 
plants are burning as high as cone 1 regularly, hence only fusible glazes 
are possible. Highly fusible glazes can only be commercially produced 
by use of lead oxide, boric acid in some form, or the alkalies, potash or 
soda. Of these, the alkali potash is expensive, and as it does not do its 
work materially better or differently from soda, it is practically out 
of consideration. Soda is abundant and cheap and effective, but it 
cannot be used satisfactorily in a raw glaze. It must be previously 
melted with silica, or some equivalent substance, and converted into a 
glass no longer soluble in water, in order to work well as a glaze ingre- 
dient. The cost of this preliminary melting or fritting, and the grinding 
which follows, makes the use of a fritted glaze objectionable. 

Boric acid is open to the same objection as soda, viz.: solubility. 
A few insoluble forms could be made, but they are not commercially 
readily available, and moreover boric acid costs twelve to fifteen times 
as much as soda. 

This leaves lead oxide as the chief, in fact the only really con- 
venient and accessible resource of the glaze-maker for low temperature 
raw glazes. 

Lead oxide is quite volatile at red heat and above,. and its losses, 
depending upon the duration and temperature of the firing, are apt 
to be large. The longer the firing continues and the higher the tempera- 
ture reached, the greater loss of lead from volatilization. This loss 
of the chief active flux brings about a rise in the maturing point of the 
glaze. 

To prevent this glaze from becoming "too hard'* by the volatiliza- 
tion of the lead, potters have long since adopted the plan of placing 
tlieir ware in saggers, or fire clay boxes, the interior of which are well 



GEOLOGICAL SURVEY OF OHIO. 433 

coated with a glaze rich in lead oxide. These saggers are piled one 
above another and the joints coated with clay, making comparatively 
tight receptacles, so as the heat increases and the lead volatilizes, its 
vapors are held in the sagger, where they soon saturate the inclosed 
space and further volatilization is thus largelj' prevented. The ware 
itself is thus protected from the loss of much of the oxide lead from its 
glaze, because the "sagger wash" has already supplied all that the 
space will contain. 

With the roofing tile manufacturer, the case is very diflfereht. He 
sets his ware in an open kiln, or at best in kiln boxes, where the lead 
oxide that volatilizes will be quickly carried out of the kiln along with 
the gases of combustion. There is no completion to the process of 
volatilization, because there can be no saturation of the moving current 
of air; therefore, it is necessary for the glazes to be loaded with a sur- 
plus of lead, to allow for the loss and to be sure that enough will remain. 
Another trouble that very frequently happens in kilns using coal, 
is the sooting of glazes. The ware set in the open boxes becomes coated 
with soot or tarry matter in the early part of the burn. Now if the 
kiln should be burned pretty rapidly, or with a shortage of air, this 
deposited carbon will be caught and retained in the glaze. This may 
subsequently change the composition of some of the glaze ingredients 
and is very likely to ruin or spoil the glaze by forming bubbles, pin-holes 
and blisters. The potter, in saggering his ware, reduces and sometimes 
prevents the deposition of soot. 

Many clays contain minerals, especially iron pyrites, that upon 

being heated give off gases. In the case of one-fire wares like roofing 

tiles, these gases pass through the coating of glaze on the surface, and 

in many instances give rise to bubbles in the glaze, as well as other 

defects. Single-fired goods are much more subject to this trouble than 

those which are "biscuited" in one fire, and glazed in a subsequent 

burn. The two-fire process however, costs very much more, and is 

now thought too expensive for roofing tile manufacture. Unless the 

manufacturer has a clay which will glaze satisfactorily by the one-fire 

}^ process, he will either have to get a clay which will, or not attempt to 

! produce glazed tiles. 

I It has been shown by experience that lead glazed goods should 

/ be protected from contact with the kiln gases, and to prevent volatiliza- 

tion they should be inclosed. Roofing tile manufacturers are doing 

/ neither. They are not only applying their glazes to a raw body, which 

is a handicap to the process of glazing, but are also setting the glazed 
wares so that they are subjected to all the changes taking place in the 

I kiln fires, and generally in the bottom half of the kiln, where they get 

- the moisture and waste gases from the wares above. Under these 

circumstances, is it any wonder that the losses are enormous on glazed 

28— o. B. 11. 



i 



\ 

I 



434 BULLETIN ELEVEN 

wares? They usually condemn the glazeman, change fuels, try every 
glaze receipt that comes within their reach, in fact do everything but 
the right thing. 

While it is true that the roofing tile manufacturer should not under- 
take to set his glazed ware in saggers, he can at least burn them in 
separate kilns, designed for this particular work. Muffle kilns, built 
after the plan of those used by terra-cotta manufacturers, are the next 
and proper step in the direction of improved production of glazed roof- 
ing tiles. As a matter of convenience and economy, this kiln should 
be rectangular, narrow and low, and not of large capacity, so that it 
may be fired frequently, and thus not hold up orders requiring a small 
amount of glazed ware. It should be set with kiln blocks in the muffle, 
the same as in the regular kiln. The muffle merely acts as one big 
sagger, keeping the flame, soot and ash off the glaze, and at the 
same time confining the atmosphere inside the muffle, so that it might 
become partly saturated with lead vapors, thus reproducing or largely 
preventing the losses from volatilization of lead. 

The roofing tile industry will never produce glazed ware in an 
economic manner, either as to cost or quality, under the present pre- 
vailing conditions. Those manufacturers that first grasp this situation, 
and properly equip themselves for the production of strictly first class 
glazed tiles at a price where they can be more widely used, will be the 
ones to get the business. 

G>mpariaon of Slipped vju Glazed Tiles. — There are a number of 
advantages in favor of the production of tiles covered with colored 
slips, rather than with colored glazes, either bright or matt: 

First, The slip is much less costly than tlie glaze, pound for pound, 
from the fact that much less lead is required. 

Second. The slip has a wide heat range over which it is merchant- 
able. The green slip, of which the formula was given earlier in this 
chapter, matures in the neighborhood of cone 02, but the same slip 
when fired to cone 8 still remained perfect, the only difference being 
that the color was better, and more intense, and the surface of the slip ^ 

was smoother, bordering on a matt glaze. What is true of this slip is j 

true of the class as a whole. 

Third, The slips will not give as much trouble from volatilization 
or blistering or crazing or any of the common physical defects. 

Fourth. The slip is much more likely to prove a durable coating, 
so far as the weather is concerned, when applied to unvitrified tiles. 
Seger says, ''No one should use glazes, unless he knows that his ware 
has the necessary degree of durability to carry them. It is known 
that soft burned tiles, when they are exposed to the weather after 
glazing, generally shell off after a short time. Hence they are not 
improved by glazing. For this reason, it must be understood that 



GEOLOGICAL SUEVEY OF OmO. 435 

tiles must be hard burned if they are to be glazed, or at least medium 
hard, and it is better if they are vitrified, but under no circumstances 
should they be soft." 

The reason for these statements can be very easily understood. 
A soft burned tile, which has an impervious glassy coating on its face 
side will have opportunity to absorb moisture from one source or an- 
other through its unglazed side. If this moisture freezes, it tends to 
force its way out of the tile in both directions from the center, and 
an enormous force is brought in play on the under side of the glaze, 
very frequently shelling or spalling it oflf. With a well vitrified tile, 
no such trouble will occur. The slip however is preferably not made 
entirely vitreous, and the water which freezes in the tile can escape 
through the slip the same as through the body, leaving both tile and 
slip unhurt. On well vitrified tiles, the slip should also be vitrified, but 
not glossy. No frost danger will come to an}' vitrified tile by reason of 
the use of either glaze or slip, but for a soft tile, a porous slip is the 
preferable coating. 

Fifth. The slip coatings are duller in surface texture than any 
ordinary matt glaze can be made, and hence give the greatest freedom 
from reflection of light from the roof, and stand for their natural color 
in any and all lights better than a glazed roof can do. 

Sixth. The setting of slipped wares is much simpler, as the sur- 
faces should not become vitreous enough to stick. Glazed tiles offer 
a serious problem in this respect. 

On the other hand, the advantages of the glazed tiles are: 

First. They use less coloring material than slips will do to obtain 
an equal coloring effect, ^or the coloring oxides in the slip do not flux 
sufficiently to really develop their colors to advantage, and hence must 
be used in larger quantity. In the production of many colors this 
would be a serious item. 

Second. The glazed tiles, even rough niatts, if of good quality, 
will present an impervious surface to the weather and will not be readily 
stained by soot and dirty water which flows over them. A slip will 
ordinarily be porous enough to discolor easier from this cause, and 
cannot be cleaned again. Any surface, even of glass, is not proof 
against the gradual incrustation of greasy or tarry soot, and no roof 
will remain permanently clean and bright. But a well glazed tile roof 
can readily be cleaned by scrub brush, soap, and hose, and a slipped 
roof can not. 

The periodic cleaning of glazed terra cotta and enameled brick 
buildings by washing is now becoming a recognized necessity if the true 
character of the surface is to be maintained, and in this connection 
roofs will also need the same treatment. 



436 BULLETIN ELEVEN 

It is not the intention or desire to discourage the use of glazed 
roofing tiles. But if used, the plane of their manufacture should be 
raised, and they should be made as perfect in proportion as enameled 
bricks or glazed terra cotta, which is not now the case. 

There is however, a broad field for dull matt glazes, applied to the 
proper kind of bodies. They should be used as a means of decoration 
only,and not as a protection to the tiles, for experience has shown that 
if a tile is not itself safe, glazing will not make it so. 



GEOLOGICAL SUBVEY OF OHIO. 437 



CHAPTER XI. 

STOCKING AND SHIPPING ROOFING TILES. 

Drawing Kilns* — The removal of roofing tiles from the kilns is 
a simple operation incapable of much variation. At present, the work 
is wholly done by hand labor, and usually of the unskilled sort. The 
manner in which the tiles are set; i. e., with or without supports, or 
with or without strips, will of course vary the work in some of the minor 
details. Where supports are used, it becomes necessary to take the 
units down as the kiln is being emptied. To gain working room in the 
kiln, it is necessary to carry or wheel the blocks from the first five or 
six benches outside, and there pile them up. For the balance of the 
draw, the blocks can be stacked against the side walls, leaving a space 
through the center of the kiln for wheeling the ware out, and beginning 
the loading later on. Where tiles can be set without supports, the 
extra work of moving the kiln blocks at each burn is avoided, and the 
work of drawing can proceed rapidly from the start. The difference 
in time required to empty a kiln set with and without supports, is about 
as two is to one in favor of the latter method. 

No matter how the tiles are set, they are taken down from the 
benches in handfuls of four to six tiles at a time, and placed on a wheel- 
barrow, such as is made for brick works. The tiles are placed on ends 
or sides as their forms may require. Spanish tiles, for instance, are 
loaded on end, two rows to a barrow. Interlocking and shingle tiles 
are for the most part placed on the side or edge, one row wide and two 
tiers deep, with common plastering laths between the tiers. 

A wheelbarrow thus loaded with interlocking tiles will carry about 
thirty to forty tiles, and with plain Spanish tiles, about twice that 
number. 

In kilns where the tiles are set self-supporting, it requires about 
one minute on the average to load a barrow, while in cases where the 
block system is used, it will require from two to three minutes for the 
same load. In either case, two men as a rule work on the same load. 
Part of the time, one man standing on lower benches passes the tiles 
down to the second man, or wheeler, who places them on the barrow; 
the balance of the time, when working on the lower benches, both men 
place the tile directly on the load. 

It was observed at the plant of the National Roofing Tile Company, 
at Lima, Ohio, that portable four-wheeled trucks were being used to 
convey the tiles from the kiln. These trucks would hold from four to 



438 BULLETIN ELEVEN 

six wheelbarrow loads each, and a permanent runway of plank had to 
be used for them. Unless on a level or down grade, two men were 
needed to move a load. As between the wheelbarrow and the truck 
methods, much can be said in favor of the former, at least for ordinary 
distances. The facility with which a wheelbarrow can be moved about 
from place to place, the narrow spaces needed in which to maneuver 
it, and the comparatively large loads that one man can move, all tend 
to make it a very convenient and satisfactory tool for the work. 

With the building of larger plants it is quite possible that it may 
be found advantageous to use a conveyor system for the unloading of 
rooJSng tile kilns, such as is done in some brickyards at present, but 
such a provision would seem out of place on any plant now in existence. 

Sorting or Grading the Ware^ — The barrow loads of tiles are wheeled 
to a sorting table, or low bench, in the yard, where the wheeler leaves 
them, bringing an empty barrow away when he returns. The sorter has 
three or more wheelbarrows conveniently arranged about the table, upon 
which he places the tiles as he sorts them into firsts, seconds or thirds 
and into the various shades. As fast as a barrow is filled with tiles of 
one grade it is wheeled away by another man, and piled up in the car, 
stockhouse or yard, as the case may be. 

A good sorter, under ordinary conditions, can grade tiles as fast 
as two wheelers can load and bring them to him from the kilns. In a 
few of the yards the tiles are wheeled from the kilns, and stocked at 
once on general stock piles by the wheelers, the sorting being done at 
a later period by the regular sorter. This method makes more handling 
of the tiles, and has no advantages in particular to justify its use. 

The sorting or grading of roofing tiles on most of the yards is 
very poorly done. In some cases no further attention is paid to this 
feature than to throw out the obvious culls. Such a practice should 
be severely criticized, for tiles shipped after this kind of sorting are sure 
to prove unsatisfactory on a first-class roof, and are a detriment to the 
industry as a whole. The conditions in every plant at times are such 
that the temptation to ship everything that can by any possibility pass 
muster is very strong. Sometimes the demand for tiles has been above 
the supply. Sometimes, in a weak and struggling plant, the urgent 
need of money has brought about poor sorting, in order to get ship- 
ments on the way so as to be able to draw on the consignee earlier. 
The policy of high-grade sorting justifies its cost in the long run beyond 
any question. 

The careful sorting of tiles into shades is a matter of far less im- 
portance than the grading as to soundness, freedom from warpage or 
structural defects. There is a widespread and well-founded demand at 
the present time for a liberal range of shades in one order. In fact, calls 
are not uncommon for a much greater variation than is produced in the 
normal product of a kiln of ware. Architects have gotten away from 



GEOLOGICAL SUBVEY OF OHIO. 439 

the use of closely shaded colors, either in bricks or tiles, and it is not 
likely that the demand for close matching of shades will return, at least 
in this generation. Tiles, like bricks, when closely shaded prove monot- 
onous in appearance, while a variegated roof or wall has a texture or 
character" far more pleasing to the eye of a cultured observer. 

Yarding or Storing Roofing Tilt& — Up to the present time the 
carrying of large stocks of roofing tiles has been for the most part un- 
known. Many of the plants in the past have for the greater part of 
the time been behind in filling their orders. In such cases the stock 
piles, if any, represent only seconds and culls. 

While some of the plants have built large stock sheds, the larger 
number of them make no provision at all, except limited shed room for 
the trimmings. With a closer grading of the ware and larger outputs, 
it will probably become the practice to house all first grade ware at least. 
Where yarded in the open, the tiles soon become very dirty, and in 
the winter they freeze together in the piles, thus making shipments 
next to impossible. 

The method of piling the stock in the open is quite clearly shown 
in the accompanying illustration, Figure No. 178, where both inter- 
locking and Spanish tiles can be seen. 

Interlocking tiles are generally stacked on edge, with plastering 
lath between to keep the tiles from rolling and the courses level. 
Boards are usually placed on the ground for the first course of tiles to 
rest upon, otherwise the superimposed load will sink them down into the 
dirt. 

In Figure No. 179 can be seen the method of storing auger-made 
Spanish tiles. It will be observed that this company has provided a 
shed for the protection of its stock. The tiles are yarded by stand- 
ing on end about four courses high, with lath or strips between. 

The stocking of hip rolls and cresting is accomplished in much the 
same manner as for tiles. The larger sizes stand upon end, about four 
courses high. The smaller sizes that will not stand solidly are in some 
cases stocked in racks or bins, piling them up so that they cannot fall. 
Larger pieces, like finials and special ware, are in some cases stored on 
racks or shelves, but it is not uncommon to see them left standing 
about the yard, to become begrimed with soot and dust until they look 
like second-hand ware before they are shipped. 

Packing and Shipping Roofing Tiles. — With very few exceptions 
the roofing tile manufacturers of this country ship practically all of 
their output to distant markets, thus entailing the loading of the ware 
into freight cars. On the ideal yard, the loading switch is depressed 
to a point where the floor of a car is at the stock-yard level. This is 
very important, because the tiles are in all cases wheeled from the yard 
into the car, and in those plants where the men are forced to wheel the 



BULLETIN ELEVEN 



Fig. 178 — Stock Yard Showing Manner of Piling. Chicago Heights Plant, 
Ludowici-Celadon Co. 



Fig. 179— Storage Shed for Spanish Tiles. Cincinnati Roofing Tile & 
Terra Cotta Co., Cincinnati, Ohio. 



GEOLOGICAL SUBVEY OF OHIO. 44 1 

tiles up inclined runways, smaller loads will surely be wheeled and the 
loading will prove more expensive. 

In loading a car, the tiles are placed in the same position as for 
storing on the yard, i. e., the interlocking are packed on edge and the 
Spanish as a rule on end. The car loader begins by placing a row of 
tiles from side to side of the car at one end, leaving about a two inch 
space into which straw is packed tightly. In addition straw is wedged 
in at either end of each row to prevent lateral motion. Plastering 
lath are then placed on top of each row before the second or next one 
above is put in. When about four courses have been placed in the 
first row or tier, either straw or a lath frame is placed between the first 
and second rows as the latter is being filled. Both ends of the car are 
filled, until the open space between the doors is all that remains unfilled. 
Bracings are then put in across the space as in figure No. 180. 

To prevent the piles from being knocked over by the jolts in transit, 
as a general rule only plain tiles of regular shape are packed in rows 
and tiers as described. All trimmings, such as finials, crestings and 
special pieces, are packed on top of the regular tiles, while small pieces, 
like small cut hip and valley tiles, and tower tiles, are frequently packed 
in barrels in order that they may not be broken or lost between the car 
and building at the unloading point. 

Packing MateriaL — For the greater part, the packing material is 
either wheat or oat straw, preferably the latter on account of its soft- 
ness. The ideal material, however, is the so called prairie or wire grass, 
so extensively used for packing bananas. This material has very great 
toughness and at the same time is very soft and pliable. It makes the 
work of packing easy. At some points, sawdust and shavings have 
been used; of the two, the latter is the better, though neither is satis- 
factory. The constant jarring of the car causes the sawdust or shavings 
to work down, leaving the upper courses loose, in which case many of 
the tiles will be broken. 

In the loading of roofing tiles, it is usual to work a double crew, 
that is, the loading of th