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Robert I lenderson Clapperton

and

William I lenderson

BASIL BLACKWELL - OXFORD

First edition, 1929
Second edition, 1941
Third edition, 1947

MONT*© V* <3 MAT BRITAIN IN THS CITY Of OXFORD
AT DU AID BN PERM

FOREWORD

A siK'f'i'.ssi-ui paper mill must he dynamic and not static; lienee the need for a
periodic revision of any standard work like Modem Ptipcr-Makiup. After
reading this fascinating and exhaustive work the inclination is, like Oliver Twist,
to ask for more. We could wish that such experts on mill practice could have
-found space for a chapter on I.ahour and Management to help us to solve the
many problems which w i 11 arise after the present War is over. Our industry
will then have to find room for those who have been serving in the forces.
When the last War ended in mi.H the majority of mills were able to solve the
problem by changing from a two-shift system to three shifts. Are we prepared
to he courageous and change over to a four-shift system and work over the
weeks-etuls as some industries do now? If we do then we shall need more
Assistant Managers and extr/'foremen, ami for those who aspire to these
positions this hook should prove invaluable.

SYDNEY D. WHITEHEAD

Stoneci tHuat,

Augusl,

PREFACE TO SECOND EDITION

This second edition, in a revised form, was thought mvcssan on act ount o
the very great demand for the hook from students and paper-makers durtnr
the last few years, by which time the first edition was out of print.

Unfortunately, however, when the work was nearlv completed, the wai
intervened and caused unending delays and mauv difficulties.

Modem Paper-Making has practically been re-written in the light <>f fu-sli
experience and new methods which have been adopted during, the last ten seats,
and assistance has been sought from acknowledged experts in the various fields
covered.

We are indebted to Dr. Bates for the chapter on Wood Pulp, and also to
Mr, G. R Underhay for the very excellent chapter on the Manufacture of
Newsprint. Our thanks are also due to the many manufacturers of paper-
making machinery and others lor the loan of hloeks lor the illustrations, and
to Mr. A. Hugh Rutt for the section dealing with paper conditioning.

We should also like to express our thanks to Mr. Potts for his photograph
of the Suction C .ouch Roll, and to Mr. Bin us for great help with the chapter
on the lesting of Paper. We are also indebted to Kenneth Ross for hts very
painstaking assistance with the correcting of the proofs, ,uid to Mr. A. B. (‘allig an
for drawings and diagrams.

u. tt. ci At’i'tarroN

Ow-'ltNWma), Wil l JAM HI-NDI-KSON

Yorkshire,

April, ig.fi

PREFACE TO THIRD EDITION

Owinu to the great demand lor this book it has been net essury to tepunt it.
During the time which has elapsed between lo.p and imp. there has not been
sufficient change in paper-making practice in general to warrant re-writing the
book. It is, therefore, presented again in almost the same form, and it is
hoped that it will fill the want, which has freijuent l v been expressed, for uioic
copies of the book to become available, both in this country and abroad.

K. II. f!1 Al’I'KKTON

Grehnhkld, WiU.tAM HIsNUritSON

Yokkshiki-,

1947

CONTENTS

CHAPTER PAGE

I. Fibrous Materials used in the Manufacture of Paper 1

n. Paper from Rags. (Classes of Rags) 11

III. Treatment of Rags. (Sorting—Boiling—Washing—Bleaching) 21

IV. Boilers—Bleaching—Preparation of Bleaching Solution—Gas Bleaching 37

V. Reduction to Half Stuff—Wood Pulp—Esparto Grass—Straw 5°

VI. Beating. (Beaters—Beating—Refining) 74

VII. Beating of Various Fibres and the Characteristics they impart to Paper. (Cotton—Linen—

Wood Pulp—Esparto—Straw) 97

VIII. Repulping ‘Broke’—Effect of adding Broke to the Furnish—Broke and Waste io6

IX. Resin Sizing—Starch—Silicate of Soda—Alum—Loadings ii<s

X. Dyeing of Paper—Mineral and Inorganic Dyes—The Use of Aniline Dyes 128

XI. The Fourdrinier Machine ' *3<5

XII. The Fourdrinier Machine (Continued) *6°

XHL The Fourdrinier Machine (Continued) 182

XTV. Paper-Making on the Machine—Water-Marking 22 4

XV. The M.G. or Cylinder Machine—The Vat or Board Machine 241

XVI. The Manufacture of Newsprint 2 54

XVII. Hand-Made Paper 282

XVm. Gelatine-Sizing—Hand-Sizing—Tub-Sizing—Air-Drying 2 9°

XIX. Damping—Super-Calender—Plate-Glazing—Cutting—Guillotine—Slitting and Winding—

Sorting and Finishing—Paper Conditioning 3 02

XX. The Testing of Paper—Transparency and Opacity—Durability and Storage of Paper 326

XXI. Water Supply—Recovery and Re-Use of Water 342

XXII. Soda Recovery 355

Appendix of Tables 3<5i

Index 377

vii

ILLUSTRATIONS

FIG. PAGE

1 The Fibres of Cotton, Linen, Esparto, and Straw, with Characteristic Ceils 3

2 The Fibres of Wood Pulp 7

3 Latest Type Giant Heavy Rag Chopper 22

*4 Rag Willow and Duster, with Part of Cover removed to show Wire-Covered Drum and Spikes 23

5 Spherical Rag Boiler, holding up to Six Tons, Fitted with Large Manhole to Empty in One or Two

Revolutions ’ 25

6 Latest Type Heavy Duty Rag Breaking and Washing Engine 28

7 Latest Type High Capacity Rag Breaking and Washing Engine, with Two Extractor Drums and

Internally Driven Rolls 29

8 Sinclair Stationary Vomiting Boiler for Esparto Grass 39

9 Arrangement of Bleach-Mixing Plant, using Bleaching Powder 41

10 Battery of Masson-Scott Bleaching Towers with Potcher and Concentrator 47

11 Three-Drum Washing and Concentrating Machine for Wood-Pulp, Rags or Esparto Grass 49

12 Floating Logs down from the Forest 51

13 Towing a ‘Raft* of Logs across a Lake to the Pulp Mill 53

14 Battery of Kamyr Grinders 54

15 Transporting Logs into the Mill 59

16 Plan of Sciennes Patent Hollander Beater, showing the Well-Designed Shape of the Trough, which

eliminates Dead Spots and aids Circulation 75

17 Beater Roll, Front Elevation, showing Bars arranged in Clumps of Two 76

18 Elevation of Beater Roll, showing Two Methods of Filling 76

19 Basalt Lava Beater Roll with Cast-Iron Spider and Stone Segments 77

20 Front Elevation of Bed-Plate and Section of Roll, showing Roll Bars arranged in Clumps of Four

and Bevelled 78

21 Various Shapes of Beater Bed-Plates So

22 Umpherston Beating Engine 81

23 A Battery of Taylor Beaters, with a Range of Bleaching Towers in the Background 82

24 Elevation and Plan of the Tower Beater 83

25 Sciennes Hollander Beater, showing Three Bed-Plates placed up the Backfall, also Equally Spaced

Bars on Roll, and Very High Backfall 84

26 Sciennes Patent Beating Engine, showing Automatic Control Gear 85

27 The Thoksen-Hery Beater 88

28 Plan of Thorsen-Hery Beater 89

29 The Neythor Press 91

30 Mascot Refiner with Top Half of Casting removed, showing Cone 93

31 The Mascot Refiner 94

32 The Marshall Refiner, Disc End 95

33 The ‘Perfect’ Pulper: Section showing the Revolving Shaft and Fixed Arms 107

34 Watford Patent Pulper 108

35 Sectional View of Kollergang or Edge Runner, showing Driving Mechanism and Base Stone 109

36 Bewoid Mill, showing Steam-jacketed Pans and Measuring Vessels 119

37 Latest Type Fourdrinier Machine To face page 136

38 The Plunger Type Stuff Pump, Direct-Driven by Electric Motor 139

39 A Back-Water System of a Paper Machine 142

40 The Rotor Whitewater Circulation System *43

ILLUSTRATIONS

FIG. PAGE

41 Special Bends and Pipes of Rotor Whitewater Circulation System, to cause the Water to spin through

the Pipes Spirally, and thus keep the Discharge Opening Clear 144

42 The Erkensator, Size IV, showing Lid opened for Cleaning, and revealing the Inner Cylinders 147

43 Digram of the Erkensator, Size IV, showing the Path of the Stuff as it passes through 148

44 Vertical Elevation and Plan of the Purifuge Centrifugal Stock Cleaning Machine 149

45 Bird Centrihner 150

46 The Vortrap, showing the Complete Arrangement and Path taken by the Stuff 151

47 Diagrammatic arrangement of a Two-Unit Dirtec Installation 152

48 The ‘Leith Walk’ Full-Drum Inward-Flow Revolving Strainer 156

49 Latest Type Bird Screen iyj

50 The Watford Auxiliary ‘Tremor’ Strainer 159

51 Voith Sliceless Flow Box 164

52 Latest Adjustable Type Voith Sliceless Flow Box 165

53-54 Photographs at the Same Magnification of Plain Weave and Superfine Weave 72 Mesh 168

55-56 Photographs of Hand-Sewn Seams 170

57-58 Welded and Soldered Joints 171

59-60 Photographs of the Under Sides of Rand-Sewn Seam and Twill Wire, Both of which have been

ALLOWED TO GROOVE . 172

61 Wire Part of a Fourdrinier Machine To face page 17 6

62 Automatic Wire Guide 177

63 Automatic Wire Guide 177

64 Latest Type Shake Motion, with Variable Speed Motor for Speed Alteration 180

65 Suction Box Plan and Section 183

66 New Type ‘Vulture’ Vacuum Box Tops, wtth ‘End On’ Grain for Long Wear 184

67 Various Types of Sections of Suction Box Tops * 185

68 The ‘Aquair’ Vacuum Pump for Suction Boxes and Couch Rolls . 186

69 Suction Couch Roll working on a Machine making Fine Tissues at High Speed 19 i

70 Millspaugh Suction Roll, showing Springs for holding Box up to Shell and Adjusting Screws 192

71 The Press Part of a Modern Machine: Plain Press Rolls 193

72 Weil-arranged Presses on a Machine for making Fine Tissues 194

73 Rubber-Covered Suchon Press Rolls 195

74 Dual Press Arrangement, showing One Suction Roll and Two Plain Rolls arranged together 196

75 Sketch showing Usual Arrangement of Presses (Above) and Dual Press (Below) 197

76 Vickery Felt Conditioner with Two Shoes 198

77 Felt Conditioner designed for Mould and Board Machines 199

78 The Evans Rota Belt, with Three Suction Boxes, fitted beneath a Wet Felt 200

79 The Evans Rota Belt fitted under a Wet Felt. The Fluted and Perforated Revolving Rubber Belt

is clearly shown, also the Vacuum Gauges to the Suction Boxes 201

80 Arrangement of Drying Cylinders on a Machine making Fine Papers 203

81 Diagram of Steam in the Drying Cylinder, and Condensate Collecting Trough 204

82 Patent Steam Inlet and Water Outlet Nozzle for Cylinder and Calenders * 205

83 The V.J3. Steam Circulation Plant, showing the Complete System as applied to Drying Cylinders 207

84 The Holmes and Kingcome Steaming System „ 209

85 The ‘Happer’ Patent Dry Felt Drying Cylinder 213

86 Vickery Flexible Doctor applied to a Press Roll 214

87 Vickery Patent Flexible Doctor applied to a Breast Roll 215

88 Harland Drive on 200-lNCH Board Machine 219

89 The Harlan d Intersection Speed Regulator Unit 220

90 Harland Driving Unit 221

91 Variable Speed Electric^ Reel-up, enabling Hard or Soft Rolls to be made 222

92 Wove Roll 227

ILLUSTRATIONS

FIG. PAGE

93 Laid Roll, Ordinary Journal Type 228

94 Wove Dandy Roll, Hollow Type 228

95 Dandy Stand, Bearings and Adjusting Mechanism for Hollow Dandies 229

9<5 Water-Mark Devices used in Certain Sizes of Sheets 236

97 Showing how the Water-Mark fails in a Large Post Upright 4T0 Sheet, 4 on 237

98 Showing how the Water-Mark falls in a Large Post Svo 238

99 Position of Water-Mark in Broad Quarto Sheet 238

100 Position of Mark in Staggered Quarto Sheet 239

101 Drying Cylinder of a Large M.G. Machine, showing Two Press Rolls and Complete Hood 242

102 Electric Drive fitted direct to Journal of a Large M.G. Cylinder 243

103 Sheet-forming Vats of a Multiple-Vat Board Machine 248

104 Vats and Couch Rolls of a Multiple-Vat Board Machine 249

105 Mux for making Boards To face page 250

106 A Battery of Chests for supplying Stuff to the Vats of a Multiple-Vat Board Machine 250

107 Stacked Drying Cylinders, Calendars and Reel-up of a Large Board Machine 251

108 The Two Wire Parts and Press Part of a Twin-Wire Machine, showing the Method of bringing the

Under Sides of the Two Sheets together at the Main Press To face page 252

109 2J-T0N Cranes used for unloading Pulp, Coal, and China Clay direct from Ocean-Going Ships 259

no Typical Clay Slurrying Plant, showing Two Mixing Tanks from which the Slurry flows by Gravity,

through a Direct-Driven Rotary Strainer, to the Storage Tank 261

in Breaker and Beater Floor for the Preparation of Stock for Two Modern Newsprint Machines 262

112 Sturtevant Bale Pulper 263

113 The Rotospray for Cleaning Clay and other Loadings, and Colours. Tins also has a homogeniser

FOR SEPARATING THE PARTICLES AND GIVING AN EVEN FLOW OF CLEAN SLURRY 2&J

1 14 Latest Type of High-Capacity Bird Screen for Newsprint Stock 268

115 A Typical Strainer, Breast Box and Projection Slice Assembly for a Large Newsprint Machine 269

1 16 Section through a Typical Flow Box and Slice for a High-Speed News Machine 270

117 Arrangement of Millspaugh Duplex Vacuum-Forming Machine with Stacked Suchon Press 271

118 Diagram of Millspaugh Automatic Couch which eliminates the Draw between the Conventional

Couch and First Press 2 74

119 View of a Neatly Designed Hood fitted over the Dryer Part of a Large Newsprint Machine 27 6

120 Diagram illustrating the Circulation and Removal of Ant in the Dryer Part of a News Machine 276

121 View of the Dry End of a Fourdrinier Machine equipped with a Minton Vacuum Dryer 277

122 View of the World’s Largest Paper Machine 2 78

123 Diagram illustrating an Arrangement for damping Newsprint prior to Super-Calendering 279

124 The World’s Largest Super-Calender 2 &>

125 Hand-Made Paper-Making 2g 4

126 Hand-Made Paper-Making 28 5

127 Tub-Sizing Vat and Squeeze Rolls 2 95

128 Section of Tub-Sizing and Air-Drying Machine, showing Hot-Air Blower on Top Section 297

129 Tub-Sizing and Air-Drying Plant, showing Tub and Squeeze Rolls, also Sparred Drums of Dryer 299

130 Orion Spray Damper with Adjustable Nozzles 3 02

131 Watford Patent Aquamist Damper with Adjustable Nozzles 303

132 Large Super-Calender for Newsprint 305

133 Modern High-Speed Super-Cutter with Layboy 3 12

134 Voith High-Speed Slitting and Rewinding Machine 316

135 Dixon Slitter for Slitting Narrow Coils and Winding on Alternate Bars 317

136 A Weil-Lighted Sorting and Finishing House 3*9

137 Examining, Cleaning, Banding and Packing Cons of Cigarette Paper 320

138 Hall and Kay Patent Paper-Conditioning Plant for conditioning Paper continuously in Machine '

Rolls t

ILLUSTRATIONS

xii

FIG. PAGE

139 Paper-Conditioning Plant, showing the Paper passing round the Sparred Drums 324'

140 The Mullen Paper Tester for Testing the Bursting Strength of Paper 328

141 Schopper-Dalen Bursting Tester 329

142 New British Bursting Tester, with Latest Type Diaphragm Control Mechanism 329

143 Schopper Tensile Tester arranged for Electric Drive 330

144 Tensile Strength and Stretch Testing Machine 331

145 Folding Tester 332

146 Elmendorf Tearing Tester 333

147 Micrometer Thickness Tester 334

148 Water Clarification and Filtration Plant at a Paper-mill (Capacity 15 Million Gallons per Day) 343

149 Bell Pressure Filter ' 344

150 Section of Pressure Filter, showing Under-Draining System 345

151 Typical Vertical Water Softener, Lime-Soda Type 346

152 Chemical Dry Feeder, for the Accurate Addition of Chemicals for Water Treatment 347

153 The Adka Patent Save-All 353

154 Scott Quadruple Effect Evaporator for Caustic Soda Liquor 356

155 Two Scott Rotary Furnaces with Patent Soda Grates 357

156 Causticisers, and in Rear Rotary Vacuum Filter 358

157 Flow Diagram of Caustic Soda Recovery Process 359

CHAPTER I

FIBROUS MATERIALS USED IN THE MANUFACTURE OF

PAPER

A sheet of paper consists chiefly of a collection of vegetable fibres, of different
lengths and sizes, twisted and interlaced with each other, and finally squeezed
together, to make a sheet or web with a surface suitable for wri ting and
printing. - .

The strength of paper depends to a great extent, though not entirely, on
the length and strength of the individual fibres which go to make it, and also
on the character of the fibres themselves.

The quality, or kind of paper made, depends on the nature of the fibres. As
the fibres from different plants are in themselves different in structure, length and
purity, it is necessary, first of all, to have some knowledge of the nature and
appearance of the various fibres.

Fibres are the ‘bones’ of all plants. Just as the bones of animals are the frame¬
work on which are built up the living bodies, so are the fibrous elements of
plants the supporting framework of the living plant.

Fibres from plants are the raw material of the paper-maker, and to obtain
these fibres free from the protoplasm, or living juices and matters which are
contained in and surround the fibres, is the first work he has to undertake. When
so obtained, the fibres are termed ‘cellulose’.

Fibres are too small to be seal distinctly with the naked eye, but the
characteristics can be readily distinguished and examined with the aid of a
microscope.

We shall concern ourselves chiefly with the five principal materials illus¬
trated: Cotton, Linen, Esparto, Wood and Straw.

With the single exception of Cotton, all these fibrous materials are made
up of varying proportions of cellulose and lignin, together with rosin, silica and
plant juices, and it is this substance, cellulose, to which they have to be reduced
in the pulp or paper mill.

Cellulose, as we know it in the mill, is a white, fibrous substance, having the
chemical formula CeHioOs, which means that six atoms of carbon are combined
with ten atoms of hydrogen and five atoms of oxygen, to form one molecule
of cellulose.

MODERN PAPER-MAKING

In isolating cellulose from plants, chemical and mechanical processes are
necessary,. differing for the various plants under treatment. These processes
are chiefly directed to the removal of the various' impurities, gums, resins,
starch and other natural products of growth from the plant, leaving the cellulose
more or less pure. Lignin is the life juices (or their resulting gums or resin?) of
the plant, intimately bound up with the cellulose. Being, therefore, cellulose
imperfectly formed, or in process of being formed, it may be removed by
chemical means, which, in some cases, just fall short of the destruction of the
cellulose proper.

Cotton is the purest form of cellulose which nature produces. It requires
practically no preliminary treatment to render it fit for paper-making.

Each of the celluloses produced from the various raw materials mentioned
is, however, different from the others in the size, length, strength and structure
of its fibres. They have therefore different paper-making properties.

As a simple illustration, these different fibres may be likened to the various
sticks or branches which may be cut from different trees or bushes; for although
all these consist of wood, yet they are far apart in texture, strength and form;
one stick may be hard and brittle, such as elm or beech, another tough and
whippy, such as ash or willow, a third long and straight, such as bamboo or
cane. All these grow in various but definite forms, and each has its use in a
different way.

All fibres are tubular—that is, they have an outside wall and a hollow centre.
The thickness of this outside wall and consequent narrowness of the central
canal or ‘lumen’, as it is called, varies with the different fibres, and has its effect
on the ultimate properties or quality of the finished paper.

Cotton (Fig. i, No. i).—The cotton fibre is a single slender hair or cell,
which grows out from the end of the cotton seed. It was probably evolved as a
covering or protection for the seed, or an attraction for the insects which transfer
pollen from one plant to another and so fertilize the seeds. The cotton plant
is cultivated principally in India, Egypt and America, from whence the fibre
is exported to such places as Lancashire for spinning and making into cotton
goods. The latter, in the form of rags of all descriptions, is our raw material,
but it is also used in the natural form, when we receive it as the refuse of cotton¬
seed oil and cake works, mixed with seed husks and dust. T his ‘recovered’ fibre
is called cotton ‘linters’.

The cotton fibre is a comparatively long, flat tube, its average length being
about i inch, while its width is about 7555 or 7^5 part of an inch; in other
words, 1000 or 1200 fibres placed side by side would take up 1 inch of space.

The central canal of this tube, during the period of growth, contains the
juices which build up the fibre. When growth ceases, these juices dry up and

FIBROUS MATERIALS

the tube collapses on itself and takes on a twisted form, something like a cork¬
screw, or a rubber tube which has had the air sucked out of it. This peculiar
formation is of great interest and value to the paper-maker.

The fibre has a thin outside wall and a wide canal. The twisted, corkscrew
form taken up by the cotton fibre is very characteristic, and may be clearly
seen in the illustration. This is the chief reason why cotton produces a paper
that is soft, flexible and bulky. The fibres will not pack closely together as

flat fibres do. They are opaque, white in colour, with no pores or cross¬
markings, and the ends are round, blunt points.

In the process of paper-making, the appearance of these fibres is very much
altered. The blunt ends are often destroyed, and are rarely seen under the
microscope. The curious twist is not so prominent, and the fibres are tors
and shredded.

Although, as mentioned already, cotton fibres will not lie closely together
owing to their twisted formation, nevertheless, under the influence of theJfews

MODERN PAPER-MAKING

and shake on the machine wire, this formation causes them to become inter
locked with each other, and adds great strength to the paper, in addition t(
flexibility and bulk.

In order to give a clear explanation of this fact, we will again take th<
illustration of a number of sticks cut from different trees or bushes.

Suppose we have a dozen sticks or faggots cut from a thorn tree or hedge
They will be more or less twisted and irregular in shape. On the other hand
a bundle of canes will be composed of pieces more smooth and straight. Th<
faggot bundle will be more bulky than the other, because the sticks will no
he so closely together. Further, if we try to pull out the sticks from the firs
lot, we will find it very difficult to do so, but we can pull the canes out quin
easily.

Good new cotton (from rags, not raw fibre) when carefully beaten wil
produce the strongest papers, as strong as those made from linen. It requires
however, less drastic treatment in the beater than linen, because it is not sc
easy to make ‘wet’ or ‘greasy’ without cutting the fibres too short. The cottor
fibre is used for making a very great variety of papers, either alone or mixec
with other fibres.

It is ideal for filter- and blotting-papers, being easily and quickly cut; its
wide central canal and the spaces between the irregularly-shaped surfaces make
plenty of room to be filled by the ink, or to allow liquids to pass through.

In short, the cotton fibre is one of the most adaptable that the paper-maker
has at his command.

Linen (Fig. i. No. 2).—Linen is the fibre obtained from the flax plant,
which is grown in most parts of the world, and especially in the North of
Ireland, Russia and Central Europe.

The fibre is what is known as a bast, or inner bark fibre, and it is obtained
from inside the stem of the flax plant by removing the bark or outer covering.
The removal of this bark is a somewhat difficult operation, and is accomplished
by leaving the cut flax lying in ditches or water to rot or ‘ret’. This is known
as the ‘retting’ process. In this way the outer bark is softened and rotted away.

After the retting is completed, the flax is collected and sent to the spinning
and textile factories, where it is spun into linen thread.

A linen thread is never so even and regular as a cotton thread, owing to the
hardness of the linen fibre and the knots which it contains; it is, however,
smoother and more ‘shiny’ on its surface. The length of the linen fibre is
about the same as cotton; it is about 1 inch long and grows in tight bundles
inside the stem of the plant; it is very narrow, about 1200 to the inch, but it is
much thicker-walled than cotton, and in consequence its central canal is much
narrower.

FIBROUS MATERIALS

The fact that it is thick-walled accounts for its being much stiffer and stronger
than the cotton fibre. It is round, or rather polygonal, in shape, and not flattened.
Its curious shape is due to tight packing of the fibre bundles in the stem during
growth. As cotton may be distinguished under the microscope by its flatness
and corkscrew bends, so the linen fibre may be distinguished by its knots
or nodules, which give it the appearance of a piece of bamboo, by its small
central canal, and, under high magnification, by cross-markings caused by the
bending of the stem during growth. These characteristics may be easily seen
in the accompanying sketches.

Linen fibres were among the first to be used for making paper, thousands
of years ago, by the Chinese. Nowadays linen seldom forms the entire furnish
of a paper, one reason being that it is scarce, and consequently expensive,
and another its extreme ‘wetness’ in working, which renders it very difficult
to make strong, thick or even medium-weight papers with it on a Fourdrinier
machine.

Linen is used chiefly in such papers as strong loans, thin banks, tissues and
cigarette papers, and in bank-notes and currency papers such as Bank of England
notes. Its great value is in conjunction with cotton, to stiffen up and give
strength to loans, ledger papers and tbin banks.

Wood'Fibres (Fig. 2, Nos. 1, 2, 3 and 4).—The fibres obtained from wood
may be said to consist of two kinds, for although they are ultimately the same,
the fibres from mechanical wood, as they come to the mill, are different, both
in appearance and properties, from those which come in the form of chemical
wood pulp.

Mechanical wood pulp is distinguished from chemical wood pulp in that
it is prepared from the tree or log by purely mechanical means; that is, it is
ground up into a sort of sawdust in water, and receives no chemical treatment
whatsoever to free it from liquid resins, etc. It is very impure, and the fibres
are short and brittle and often united in clumps by medullary rays.

The illustrations show clearly how these mechanical wood fibres differ
from the chemical wood fibres, and a glance at them will make it apparent
how very different are their properties as paper-making materials. The fibres
obtained from wood by one or other of the chemical processes are fairly long—
they vary very much in length—although shorter than those of cotton or linen.
They are wide in comparison to their length and they are flat and sometimes
twisted. The fibre walls are usually ‘pitted* with small pores or holes.

There is also a decided difference in the fibres obtained from the two classes
of trees. The fibres from coniferous trees, such as spruce and pine, are longer
and stronger than those obtained from deciduous or foliage trees, such as
poplar and aspen. The former are more like cotton, and the latter resemble

MODERN PAPER-MAKING

esparto in that they are short and fine, but they are much flatter than esparto
fibres, and do not give such good bulk, for the same finish and substance.
When suitably treated (by the soda process) these pulps from poplar wood
make fairly good substitutes for esparto, and they are extensively used for the
manufacture of better-grade printing papers in America.

The fibres of strong sulphite are used chiefly for giving strength and binding
properties to newsprint, and also for the manufacture of strong envelope, bag
and wrapping papers.

The fibres of bleached or easy-bleaching sulphites are used alone or in
conjunction with esparto in printings and writings, and also with cotton and
linen in writings and ledger papers.

From the foregoing remarks it will be gathered that the fibres from trees are
of many kinds and have many different uses, which may be roughly tabulated.

TREES

Deciduous (or Foliage)

Poplar

_ ! _

Sulphite Process Soda Process

Short and Free like
Esparto

Printings and Blottings

Coniferous
Spruce, Pine

Mechanical or Chemical Wood

Ground Wood I

Newsprint and Brown Mechanical

Cheap Printings, |

Boards, etc. Cheap Coloured

Papers

Sulphite

Soda

Sulphate

Strong and Flexible

j suitable for

Same as

Strong

Bleached

Easy-bleaching Kraft Papers

Soda

Writings Banks, etc.

Wrappings

Newsprint

M.G. Sulphite
Bag Papers

Best Printings
(with esparto)

Thin Banks, Manifolds,
G.I.P., and Tissues

Writings (with
or without
rags)

We therefore see that the two classes of trees, treated in different ways,
will give us fibres suitable for making practically every kind of paper, from
tije strongest ‘manilla’ wrappings to the most brittle and weak newsprint.
They will also produce fairly good blotting-paper.

The wood fibres are easily distinguished under the microscope, for mechani¬
cal wood fibres can almost always be recognized by the medullary rays or

FIBROUS MATERIALS

cross-bindings which can be seen in the diagram (Fig. 2, No. 4). Further, if
the fibres are stained with a solution of iodine and zinc chloride they give a
bright yellow colour.

Cellulose pulps from coniferous woods consist entirely of fibrous elements
(tracheids). The fibres of spring or summer wood are broad, flat and thin-
walled, owing to the quicker and more juicy growth of these seasons. Those
of autumn growth are thicker-walled and rounded, with pointed ends. The

I. Birch, with cell. 2. Spruce. 3. Poplar, with cell. 4, Mechanical Spruce.

Fig. 2.—The Fibres of Wood Pulp

fibres have circular pores surrounded by depressions, and these are very charac¬
teristic, and may be distinctly seen under high magnification (Fig. 2, No. 2).
In pinewood cellulose the pores are oval-shaped. Some of the thick-walled
fibres are very similar to cotton, and they vary greatly in length.

The fibres of deciduous (foliage) trees (Fig. 2, Nos. 1 and 3) are quite short
and rounded, with fairly thick walls, and narrow slits or pores disposed diagon¬
ally. Poplar fibres sometimes have nodes, or knots, like linen. The structure
does not lend itself to beating or tearing into fibrillae.

MODERN PAPER-MAKING

All the juices contained in the fibre cells are boiled out, leaving spaces
ready to be filled with water. Very exhaustive research work has been done
on wood pulp, so far as its value to the paper-maker is concerned, by the Wood
Pulp Evaluation Committee of the Papermakers’ Association of Great Britain
and Ireland, and the results of their work are contained in a report published
by the Technical Section.

Esparto, or Alfa Grass (Fig. i, No. 3).—The botanical name of esparto grass
is Stipa tenacissima, meaning Very strong blade’; Algerian ‘Alfa,’ Arabic
‘Haifa’. This grass grows only in a hot, sunny climate, where the rainfall
does not exceed 24 inches annually, and at a high altitude—between 1000 and
4000 feet above sea level. It is a product of Northern Africa, but a superior
quality, though less quantity, is grown in Southern Spain. The nature of the
soil, altitude and ramfall modify considerably the qualities of esparto. On
siliceous soil, the plant fibres are hard and brittle; on sandy soil, they are finer,
lighter in colour, longer and stronger; salty earths produce thicker but less
tenacious fibres. Iron in the soil accentuates colour. Altitude varies the weight
and size of the leaf blade. The heaviest and longest comes from sandy clay
alluvia, medium from higher strata, and the lightest and smallest from moun¬
tainous regions. The medium is the kind most used by the paper-maker. The
longest and heaviest is worked into mats, ropes, etc., and the lightest and finest
is best adapted for basket-work.

Green or partially ripened leaves produce the best paper-making fibres.
Fully ripened leaves contain more silica and absorbed iron, which resist the
action of bleach, and make it difficult to obtain a good white colour. The grass
itself is a long, flat blade, curled by the heat of the sun into almost cylindrical
shape, with innumerable fine hairs or filaments on its surface. These can easily
be felt by drawing a blade slowly through the fingers. When harvested it
is not cut, but plucked, and this accounts for the quantity of roots found amongst
it. If pulled at the proper time (i.e. unripe) the grass comes away more easily,
with less roots.

The fibres are distributed through the mass of the blade, together with small
fibrous particles, termed cells. These may be serrated, or pear-shaped and
pointed. They are of little or no value to the paper-maker, most being lost or
washed away in the boiling, washing and bleaching. The pear-shaped cell,
however, is peculiar to esparto and forms a sure indication of that fibre when a
paper is being examined under the microscope.

_ The fibres themselves are very, fine, cylindrical and smooth, with a
minute central canal. Their average length is 1.5 mm. and their diameter
0.012 mm.

Their shortness prevents them from imparting any great strength to paper,

FIBROUS MATERIALS

but we have no reason to doubt that esparto papers produced by modem
methods are reasonably permanent.

Though esparto may be ‘beaten’ to a certain extent, the action of the beater
roll is confined mainly to brushing or drawing out the fibres, very litde ‘cutting’
being done. Spanish is shorter in the blade than African, smoother in surface,
more springy and shows superior strength and colour. It stands treatment
better, yielding a whiter and cleaner fibre.

It may be used in thin writings and banks where African would be practically
useless. The latter comes to the mill in hydraulic-pressed bales of about 3 cwt.
each, and must be stored under cover. Care must be taken to isolate any bales
that are wet (which occurs very often to ‘deck cargo’ during a voyage). These
may heat and take fire and should be used immediately if possible.

Spanish is delivered more loosely packed, bound with esparto ropes, and
for this reason is less liable to heat and rot. It is usually in a drier condition
than African.

Esparto papers are distinguished by their refined silky texture and bulk and
close uniform surface or finish. This latter quality is their most outstanding
point, and makes them eminendy suitable for fine printings and other papers
that are required to take a fine impression from plates. The best body papers
for surface coating are made mosdy from esparto. It is not a fibre that will
run well over the machine without a stiffening of wood pulp. Its ‘greasy’
nature and shortness cause it to stick to the press rolls, causing breaks and waste.
A charge that has been too harshly treated in boiling and bleaching soon makes
itself known in the machine room. In this connection it has been found that
granite press rolls are a very great advantage.

It is a very absorbent fibre, taking up and retaining a great deal of resin size,
and may be made into quite a hard, ‘tinny’ paper, very suitable for E. S. Laid
and Wove Writings. The fine surface obtained on some of the cheaper rag
papers is due to the small percentage of esparto paper ‘broken’ used as a filler.

Esparto fibre is very easily water-marked, is very regular in expansion and
contraction, and is generally considered the best for making papers that must
be accurately and finely printed and cut. For the ‘offset’ printing process esparto
papers are unsurpassed.

A peculiarity of this fibre is that after being beaten ready for the machine
it very readily runs into knots or balls, which the strainers (even with 3 to z\ cut
plates) are unable to keep back. These appear as clear spots in a high finish,
and utterly spoil the paper, so that if a chest of stuff is affected in the least degree
there is no thing to be done but to run it off at the press rolls and re-pulp. This
is caused by too much agitation in the stuff chest, either by the agitators being
run too quickly, or by the stuff taking too long to work out. The rubbing on

MODERN PAPER-MAKING

the walls of the chest and the blades of the agitators causes the softened fibres
to roll up on themselves, forming little balls.

Esparto very readily absorbs colours, and very brilliant tints may be pro¬
duced. Though the ‘Hollander’ beater may be used for this fibre, a lighter
tvpe of engine gives better results and is far more economical. The ‘Taylor’
or ‘Tower’ beaters with their lighter rolls and separate circulators are very
efficient and capable of giving all the treatment that esparto requires.

During the last few years straw has been used in very large quantities by all the
esparto mills, owing to the impossibility of obtaining esparto grass consequent
upon the war. Many of these mills have made a very great success of straw as a
suitable fibre for printing and writing papers, using approximately the same
treatment and the same equipment as they previously used for esparto. Owing,
however, to the low yield, and the longer time taken in washing, it has not been
possible to keep up the same output, and additional plant has had to be installed
to enable the mill to keep up production.

The length of the straw fibre is less than that of the esparto fibre, although they
resemble each other to some degree. Straw fibres are greater in diameter, and
are always associated with the serrated cells characteristic of both kinds of fibre.

It seems possible that many mills, after their experience of the last few years,
may continue to use straw even after esparto again becomes available, and this
would be very desirable in view of the fact that it is home-produced and gives
the farmers a greater return from their cereal crops.

CHAPTER n

PAPER FROM RAGS
Classes oe Rags

Linen and cotton rags constitute the ideal raw material for the production
of paper, but on account of their high initial cost they can be used only for
the manufacture of papers of the highest class, such as hand-made and machine-
made writings, bank-notes, ledger, and filter-papers.

The chief reasons for their suitability and value, for papers of this class,
are, that they can be so prepared as to produce papers which are extremely
good to write upon, which will stand a great deal of wear and tear, and are
probably everlasting.

When rags are properly prepared they will produce a white paper which
will keep its colour for hundreds of years without showing any signs of fading
or discoloration. The rags in general use may be divided into two classes, new
cuttings and old used rags.

New cuttings consist of trimmings and cuttings from textile factories, and
are the waste from the cutting out of shirts, shoes, canvas goods and many
other articles of clothing, etc. These new cuttings may be divided again into
linen and cotton, and below is a list of the various qualities generally met
with.

New White Linen (damask) cuttings, obtained from factories making table¬
cloths and fine linen goods. This is the most expensive form of raw material
used in the manufacture of paper, and is used only for the very best thin bank¬
note papers, which have to combine great strength and durability with lightness
.in weight. Even in the manufacture of these papers the linen cuttings are
• seldom used alone, but are blended with cuttings of other materials, such as
white cotton.

The designation white’ serves to distinguish these cuttings from another
quality known as ‘unbleached’. In the former case the cloth has been bleached
white during the course of manufacture, so that it is usually .unnecessary
for the paper-maker either to boil it with chemicals or to bleach it, when
reducing it to half stuff. All that is required, generally, is for the cuttings
to be picked over for the removal of dirty pieces, threads or other objection-^
able materials, which invariably find their way into the bales or bags from the

MODERN PAPER-MAKING

textile factory. The rags may then be dusted, and boiled to remove any
starch or loading which may have been added during the ‘finishing’ process.
If the rags are really good, they may be furnished straight into the breaker
or beater.

If after washing and breaking they are of a sufficiently white colour for the
paper required to be made from them, they are ready for the beater. If not,
they are bleached with bleaching solution until the required degree of whiteness
is reached.

New White Cotton Cuttings are almost as valuable material for the manu¬
facture of the best papers as the new white linens, except that they do not
give quite such a strong or firm handling paper, and in consequence they are
cheaper. The method of preparation of half stuff is generally the same as for
linen, though less drastic.

New Unbleached Linen.—This material consists of linen which has been
freed from a good deal of the undesirable shive or bark with which it was
associated when in the form of flax plant. It comes to the paper-maker in
the form of new linen threads, linen canvas cuttings and brown linen cuttings.
These are capable of producing papers of great strength, but in order to obtain
papers of a good white colour, drastic and prolonged chemical treatment is
necessary, and for this reason they are much cheaper than the white cuttings.

The threads or cuttings are first overlooked and, if necessary, cut up by
hand; they are then cut and dusted prior to boiling. If they are examined
before boiling, they will be found to be of a dark grey or brownish colour,
and, on close examination, large quantities of shiny brown or yellow shive or
lignocellulose will be seen, closely interwoven with the linen threads.

It is necessary for these impurities to be destroyed before the linen fibres
are ready to be made into paper. This is effected by bo iling the rags, under
pressure, with a high percentage of caustic soda for as long as io to 12 hours.
The percentage of caustic soda required is sometimes as high as 20 per cent,
and the pressure may be from 15 to as much as 45 lb. per square i nch .

When the rags are removed from the boiler, they will be found to be very
much softened, to have lost a good deal of their grey or brown colour, and
the particles of shive will be seen to be softer, and lighter in colour.

The rags are now washed with water and bleached with a bleaching solu¬
tion. If, when the bulk of the fibres has turned almost white, a handful is
removed from the breaker, it will be seen that the shive is still present, although
paler in colour; In order to destroy it further, dilute hydrochloric or sulphuric
acid may be added in small quantities. This causes the formation of hypo-
chlorous acid, which attacks and destroys the brown or yellow colour of the
shive. This shive or lignocellulose may also be destroyed by subjecting the

PAPER FROM RAGS

half stuff to treatment with chlorine gas in a gas chamber, but it is better, if
possible, to remove it subsequently by mechanical means in a centrifugal machine.

In order to obtain half stuff of a good colour from such linen or flax, and
also as free as possible from shive, it will generally be found advantageous
to use more caustic soda in the boiling, and subsequendy less bleach, than
vice versa, as by this means the rags are not so liable to become tender. Such
stock can rarely, if ever, be bleached to such a good white colour as cotton.

New Unbleached Cotton Cuttings, sometimes known as new greys’ or ‘yellow
cottons’, are the waste from factories using unbleached calico, and they vary
greatly in quality and value. The best ‘board cuttings’ are usually excellent
material, containing litde or no loading or starch, and being free from shive
and dirt. They are often nearly as expensive as new white cuttings.

On the other hand, new greys may consist of shoe cuttings or the waste
from shoe factories, consisting of inside linings of leather shoes and t rimming s
from canvas shoes, and ‘Swansdown’. While some of this material is ex¬
cellent and equal to new board cuttings, a great deal of it is coarsely woven
and full of loading. The loading in some cases is as high as 70 per cent of the
weight of the rag. This loading is, however, by no means the greatest draw¬
back to this material; leather dust and small clippings of leather, and, above all,
rubber solution, so difficult to detect in the rag room, make the use of it very
risky indeed.

Unbleached cottons are picked over by sorters, and the long strips are
either cut up by hand into suitable lengths, or the whole may be put through
the chopper and dusted prior to boiling.

Caustic soda is used for boiling, the amount varying according to the quality
of the rags, and the amount of starch and loading which they contain. From
2 to 5 per cent of caustic soda will generally be sufficient, when the pressure
employed is about 25 lb. and the length of boil about 6 hours.

New Lace Curtain Cuttings are a valuable material, being strong, clean and
easily prepared. Their chief drawbacks are the amount of starch which they
contain, and also the small hard knots, which have to be carefully broken up.

They require to be overlooked, on account of floor sweepings from the
factories, which sometimes find their way into the bales and introduce chips
of wood, straw, etc. A small amount of soda ash (sodium carbonate) is usually
sufficient to reduce them during boiling, which may be completed in 3 or 4
hours. They require careful handling in the breakers and very little bleach.

New Unbleached and White Cotton Healds can sometimes be obtained, and
they form a valuable substitute for new ‘greys’. These consist of cotton strings
about 6 to 12 inches long, plaited together at one end. Those from Egyptian
cotton are best, and they give a pulp of great strength and cleanliness.

MODERN PAPER-MAKING

They are usually very free from foreign matter; they require gentle treat¬
ment in the boiler, being almost pure cotton; and apart from the hard strip
of twisted strings at one end, they are easily broken in, but they must first be
cut up small by hand.

New Oxfords and New Light Prints are the cuttings from shirt and dress
factories, and at one time they were an important raw material for the better
classes of rag papers where strength was required. Nowadays, however,
some paper-makers are inclined to view them with suspicion, on account of
the so-called ‘fadeless’ dyes used in forming the stripes and designs on the
material. Although these dyes can generally be removed by the usual methods
of treatment in the boiler and breaker, yet there is no doubt that some of them
are very tenacious and require fairly drastic treatment, both in the boiler
and more especially during bleaching, if all the dye is to be removed. Some
mauves, yellows and blues are particularly hard to bleach out, and even when
the blues are removed from the material in which they were originally fixed,
they seem to pervade the whole mass of half stuff and give it a bluish tinge.
Of course, if the oxidizing treatment is suffrciendy drastic, the whole of the
colour can be destroyed, especially if chlorine gas is used, but it then becomes
questionable whether this has not led to such tendering of the half stuff as to
render the material too expensive compared with the results obtained.

There are many other new rags which might be described in detail, but the
foregoing is a fairly comprehensive list.

Among others may be mentioned flannelettes, which are cotton cuttings;
‘tab-ends’, or the ends of new pieces of cotton goods; linen threads, cotton
canvas cuttings, new blue jeans, etc.

We now come to the second class of rag material—namely, used or old
rags. These rags differ essentially from new rags in that they are very mixed
in quality, no matter from what source they are obtained, and they are
always dirty—the only difference between one lot and another being in
degree. They are, on the whole, much softer and incapable of yielding
a half stuff of such strength as that obtained from new rags. They contain
contraries, and impurities of all kinds, all of which have to be removed by the
paper-maker.

Ta kin g the used rags in order of ‘quality’, clean white linens and cottons
come first.

No. i Linens consist of such articles of domestic use as tablecloths, pillow¬
cases, sheets, handkerchiefs and clothing of all kinds. They are only fragments
of the original article and are fairly clean and free from impurities.

They require to be overlooked and cut up, prior to bo iling , for the removal
of buttons, elastic, etc. They also require gentle treatment in the boiler and

PAPER FROM RAGS

breaker, and yield a pure and clean half stuff of good strength, which will
become easily fibrillated and give a firm handle to the paper.

No. 1 Fines, or Best Fines, consist usually of a mixture of linen and cotton.
They are always white and clean and of fairly good strength—that is, they
are not absolutely worn out. They consist of much the same classes of articles
of domestic use as the No. 1 Linens, and often include collars and cuffs, white
shirts, etc. When of good quality they are heavy rags, and contain many
large pieces and few strips. They must be overlooked for buttons, fasteners
and elastic, and they are cut up by hand prior to being put through the chopper.

They are boiled with a very little caustic soda—say, 1 per cent—or a little
soda ash is often sufficient. The pressure used need not be high and the boiling
need only last for 2 to 4 hours at most. They require very little bleach, and
give a beautiful pure and clean half stuff, which can be beaten off very quickly
without getting too wet.

These rags are used chiefly for the manufacture of superfine writing papers
which have to be pure and bright and ‘pretty’.

Outshots and Second Fines are the same as the previous quality, but are not
so clean, or so large in size, and are more worn out. They are, in fact, thrown
out by the rag sorters when grading for Best Fines. They need to be carefully
overhauled for buttons and fasteners, elastic and ‘dress preservers’ which con¬
tain hidden rubber solution. They often contain a great many strips of clothing
which have rows of buttons and minute metal fasteners attached.

They need more caustic soda and longer boiling than Fines. They give
a fairly bright white half stuff, but it has not the strength of the Fines, and they
need more bleach.

These rags vary a good deal according to the source of supply, and great
care must be exercised in the buying of them.

Soiled Curtains .—These are often packed separately, although they are also
included among outshots and seconds. They are a soft cotton rag, very often
tender on account of frequent washing and exposure to light and air when
hanging in windows. They are, however, very uniform in quality. They
require to be carefully sorted to remove pins and elastic and metal rings. They
require little caustic, gentle boiling, and very little bleach. When carefully
handled they give a much stronger half stuff than would be expected, con¬
sidering how easily they tear before treatment.

They can be made to give a very free working stuff, suitable for blottings
and filterings.

Seconds .—There can surely be no class of raw material used by any manu¬
facturer which varies so much in quality and price as ‘Seconds’. All rag
merchants sort and pack them in vast quantities, but no two merchants sort to

MODERN PAPER-MAKING

the same standard, and for this reason the task of the rag-sorting department
of the mill is made extremely difficult.

It is impossible to give even a general definition of Seconds to cover the
whole of the packings of rags sold as such. Suffice it to say that they are all
supposed to be derived from cotton, and they consist of clothing of all kinds,
from tropical suits to imitation woollen underclothing, and from bed-ticking
to dishcloths. Ever)’ imaginable article of textile manufacture is included
among them, and in colour they range from one end of the spectmm to the
other, with the addition of black and white. So much for the rags themselves.

If the trouble ended here the task of the paper-maker would be compara¬
tively easy. It is, however, in the matter of contraries that a great deal of
trouble arises, and by contraries is meant the mulch’ or .useless material which
is often included in large quantities. It is quite impossible to refer to these
in detail, as their name is legion, but a few of the commonest may be mentioned.
These are silks and wool, string, bones, orange-peel, whalebone, feathers,
horsehair, rubber, straw, etc.

Even in the best packings a certain quantity of these is always present, and
it is simply amazing to see the amount of rubbish which is thrown out of what
appears at first sight to be a fairly decent lot.

There is only one basis on which these rags may be bought with satisfaction,
and that is on a pre-arranged standard of percentage of ‘mulch’, any excess
over the agreed maximum percentage being debited to the seller, or returned
to him after the parcel has been overhauled.

In fairness to the merchants, however, it must be admitted that there are
some who grade their rags regularly within close limits, and these packings
can always be relied upon to contain a maximum of about 5 per cent of
mulch, and very often much less. These rags are, of course, much more
expensive than the ordinary run of so-called Seconds, but by the time they
are converted into half stuff they will be found to be considerably cheaper,
and what is of as much importance to the paper-maker, they will yield a much
more uniform stock.

Seconds are always divided into several grades, such as Country Seconds,
which are the largest and best; Selected Seconds, which are usually fairly clean
and free from dark colours; and London Seconds, which are invariably dirty,
strippy and generally poor, worn out and often actually rotten.

In judging Seconds it is quite useless to depend on a post sample; at least
a ton must be bought and carefully sorted before any real estimate can be madp
of their value.

There are many different things which must be taken into consideration
when estimating their value, some of which may be given in detail:

PAPER FROM RAGS

(a) The general colour of the consignment must be taken into account, as
on this will depend the amount of caustic soda and bleach required to bring
the half stuff to a sufficiently good colour. The more caustic soda and bleach
required, the more ‘tender’ will be the resulting half stuff.

(b) The amount of ‘mulch’ which will have to be thrown out as useless,
such as silks, wool, etc. A large quantity of these contraries will reduce the
ultimate yield of cellulose.

(c) The ‘weight’ of rag—that is, the weight of a given bulk—determines
in a rough way the ultimate strength of the fibre, or, in other words, shows
whether the rags have been well worn or not. Naturally, rags which have
hot been much worn or washed will yield a stronger and harder fibre than
those which have been well worn and often washed.

(d) The general size of rag is also very important. When the pieces are
large they are quickly sorted, and when the garments are fairly complete the
sorters find it much more easy to discover the buttons and fasteners. On
the other hand, when the rags are strippy and contain large quantities of small
pieces, such as the fronts of shirts, cuffs, seams, etc., they take much longer
to overlook, and the chances are that many more buttons, metal fasteners
and pieces of elastic are missed, and ultimately find their way into the half
stuff.

With Seconds, the amount of caustic soda and the length of boiling vary
greatly, and in order to keep these regular, or within reasonable limits, the
rags must be sorted to a uniform standard in the rag loft, and this should be
regularly checked. If insufficient caustic or too short boiling is given, the fact
will soon reveal itself in the breakers, as the bleaching will require to be more
drastic and some of the colours will be difficult to destroy.

If, on the other hand, more caustic has been used than is necessary, it may
not be noticed, but it will certainly cause the half stuff to be very soft and
tender, and strength will have been unnecessarily wasted.

There is another grade of soft coloured rags sorted and sold as distinct
from Seconds. These are called Prints, or more usually Old Light Prints, or
Extra Light Prints, and they consist of much the same kind of material as
Seconds, except that they are mostly, ‘printed’ cotton, as distinct from the
white-and coloured rags of Seconds.

These rags are often stronger than Seconds, and they frequently cost a
litde more, but they require more drastic treatment to remove the colours,
many of which are nearly unfadable nowadays, and bring up the colour of
the half stuff.

The aforementioned constitute the most important grades of old soft rags
in general use.

MODERN PAPER-MAKING

Mention must be made of the several grades of Continental rags, which
find their way in large quantities into the stores of the rag merchants of this
country, and are sometimes used to 'adulterate’ the home-produced article.

These consist for the most part of white cottons of several grades, which
correspond roughly in order of precedence to English second fines, outshots
and white seconds. They are less clean, less consistent in quality, less strong,
and they invariably contain more rubber than the English grades, and they
are consequently less expensive in first cost.

Old Light Prints are imported in large quantities, but the packings vary
considerably, even from the same source, and are less dependable even than
the English grades.

Unfortunately, these prints are frequently mixed with home-produced rags, •
and almost always they reduce the general quality of the consignment.

Continental white linen rags are, however, of great value, and form an
important raw material. They are composed chiefly of home-spun clothing
of a grey colour, always'well worn, and varying in coarseness of texture from
rough ‘sacking’ to a fine linen cloth.

The chief trouble encountered with these rags is shive, or the outer bark
of the flax plant, which has not been properly removed in the ‘retting’ pro¬
cess. The presence of a large quantity of this reduces the value of the rags
so far as strength is concerned—and it is for strength that they are used—as it
means more caustic soda and more prolonged boiling than would otherwise
be required.

Nevertheless, these linens are often a welcome addition to the furnish on
account of the great scarcity and consequent high price of English linens.

General .—The quality of rags obtained in any district reflects to a remark¬
able degree the prosperity or general habits of the inhabitants. Rags from
prosperous seaside towns, or fashionable health resorts, are always far superior
to those from poor industrial areas. Scotch rags are generally better than
English rags, and country rags are cleaner than those collected in London and
other large cities.

Old Strong Rags .—These consist of linens and cotton canvas in various forms,
and the consignments contain a mixture of each.

Linen sail-cloths from the seaports are, as a rule, in large and often unwieldy
pieces, difficult for the women to cut up into strips. They are very hard,
contain many ‘eyes’, often lined with metal rings, are covered with tar, pitch
and paint, and have hard edges bound tightly with tarred string. The con¬
traries consist chiefly of those things mentioned above, which have to be cut
out.

This canvas requires a high percentage of caustic soda and prolonged

PAPER FROM RAGS

boiling, but it yields a strong and tough half stuff suitable for making strong
thin papers.

Hose canvas, both cotton and linen, is obtained from the dockyards and
from municipal authorities. It is clean, usually almost new and little used,
and nowadays rarely contains rubber as insertion. It is cut up into short strips
before boiling, and gives a strong clean half stuff of excellent colour.

Cotton tentage yields a useful strong half stuff of good colour. It is fairly
reliable in quality and contains few contraries beyond metal hooks and eyes.

It is usually clean and white, although it is sometimes covered with water
paint, which is easily removed. It requires a comparatively small amount of
caustic soda, not very drastic boiling, and gives a strong white half stuff.

Linen canvas consists of a mixture of all kinds of linen from post office
bags to tarpaulins and sailors’ hammocks. It is usually greasy and contains
varying amounts of shive, to remove which it requires a large percentage of
caustic soda and prolonged boiling.

It gives a ‘greasy’ and easily fibrillated half stuff, which cannot be bleached
to such a white colour as cotton canvas.

Cotton canvas is packed in various grades from No. 1 downwards. The
best grades are white, clean and free from contraries. They do not require
such severe treatment as linen canvas, and they produce a pure and white
half stuff, which gives hardness and strength to the paper. They contain a
good percentage of fairly new canvas. The lower grades contain all manner
of coloured pieces, from ‘Willesden’ green to brown tanned, and they are
always dirty, covered with paint, soot, tar and grease. They contain metal
hooks and eyes, buckles and rings.

This material is very difficult to sort, as it is always questionable what to
throw out and what to leave in, owing to the uncertainty of the action of the
lime, caustic soda, etc., on the various substances coating the canvas. It is
always best to throw out anything about which a doubt exists—at least until
a test has been made in the laboratory—as it is most annoying, and indeed
wasteful, to have a whole boiling spoilt by allowing a few pieces of stuff to
pass when there is any question as to its suitability.

One of the worst evils of this material, and one of the most difficult to
detect, is rubber, either sewn or woven into the canvas, or coated on to it in
the form of waterproofing solution, and many a good boiling has been spoilt
by this troublesome bugbear of the paper-maker.

Hemp, man ilia, jute ropes and bagging are used in the manufacture, both
of the highest and purest, and also of die lowest grades of paper.

Ropes and bagging are used for making wrappers. Hemp and maniha
ropes come to the mill in thicknesses varying from quite thin rope to 12-inch

MODERN PAPER-MAKING

hawsers, which entail a lot of heavy work in handling and preliminary treat¬
ment. The largest ropes are cut up with felling axes, and then divided into
the smaller component strands, which are in themselves thick ropes; they are
then cut up by means of a mechanical rope chopper, of which there are several
varieties. The simplest form consists of a machine similar to a chaff-cutter,
which shaves off the rope into pieces of suitable length ready for the boiler.

There are not many contraries contained in ropes, but ‘shakes’ are often
included, and these consist of frayed ends and small rough pieces which contain
dirt or dust.

The boiling, of this material is far more drastic and prolonged than that
of any of the canvas previously referred to. Tarred hemp ropes and coal
sacks are often boiled several times with a high percentage of reducing agent,
and subsequently they are bleached and allowed to drain, and then bleached
again.

This treatment results in the production of a strong, tough, flexible half
stuff of a pure white colour combined with great opacity.

Manilla rope stock is prepared in the same way as hemp, except that the
treatment in the boiler is less drastic, as a white half stuff is not usually desired
nor is it easily obtained. The shive is very difficult to remove, but the half
stuff is very soft, flexible and silky, and capable of producing papers of enormous
strength and toughness—some, in fact, are almost untearable.

Jute cuttings, various strings, jute bagging, etc., are used for the manufacture
of brown wrapping papers, but very little chemical treatment is necessary,
as the papers to be made are very coarse and their colour is of comparatively
little importance. Lime is used in the boiling of such material to remove grease
and other objectionable matter.

Of course these materials may be resolved to a very pure cellulose, if re¬
quired, by using caustic soda and employing high pressures, and by using
chlorine gas as the bleaching agent, afterwards removing the cblorination
compounds by washing. The yield, however, is much reduced, and the
strength of the fibre much impaired in the process.

CHAPTER HE

TREATMENT OF RAGS

Sorting—Boiling—Washing—Bleaching

After the rags have been received into the mill they are carefully examined
to see that they are up to sample as regards colour and quality, in order that the
attention of the supplier may be called should the delivery appear to be below
the standard. A few bags or bales are opened, and thus a general impression
of the quality of the consignment is obtained. Should the rags be below the
standard of the sample, they are left on one side until the supplier has been
communicated with and given an opportunity of inspecting them. If the rags
seem all right, they are put into stock ready for use.

Before the rags pass into the rag loft to be overlooked they are passed through
a conical duster to remove grit, dust, and any loose dirt, buttons, etc. If this
method is adopted it makes the task of the women overhaulers much more
pleasant, and the rag loft is also rendered more free from dust.

When the rags have been rough-dusted they are passed to the rag loft to
be overhauled and examined by women.' The rag loft consists of a large room
equipped'with rows of sorting tables, having coarse-mesh wire tops and fitted
with large vertical fixed knives opposite each sorter, so that the large pieces
may be cut up and buttons, etc., removed. A vacuum pump must be installed
to draw away the dust from under the wire mesh. This also helps to give a
purer atmosphere to the room.

The task of the rag sorter requires a great deal of experience and skill, as
the rags often have to be graded into one or two or even more grades, and also
contraries in the form of silks, wool, etc., have to be thrown out. It is also
imperative that all rubber, whether in the form of elastic, solution or insertion,
should be carefully picked out, as it is without a doubt the worst enemy of the
paper-maker, and it is amazing to see the different ways in which rubber in
one form or another is used in clothing, and how it is concealed.

Next in importance to rubber come the buttons, hooks and eyes and metal
fasteners of all descriptions which are used on clothing. These are sewn in
all sorts of unexpected places, and the greatest care and patience is required on
the part of the women if they are to free the rags thoroughly from them. Any
carelessness on the part of one woman may spoil the work of twenty, as if the
buttons or fasteners get through and into the boilers, they have only the ‘button

. MODERN PAPER-MAKING

catchers’ on the breakers to deal with them, and although these are in many
cases quite efficient, they cannot catch everything.

If there is serious trouble in the mill from metal or rubber in the paper,
the rag loft is the root of the evil—it must be tackled there. Skilful super¬
vision and, above all, great tact are required in the management of the rag loft
if the best results are to be obtained.

It is usual for the overhaulers to be paid piece rates for sorting the rags,
the rates varying according to whether the rags are fines, seconds, canvas or

[Masson, Scott & Co., Ltd.
Fig. 3.—Latest Type Giant Heavy Rag Chopper

new cuttings, etc. After the rags have been overhauled, they are either bagged
up or stored in bins until required, and they are then overlooked again by other
women—paid daily wages—whose duty it is to run the rags through and pick
out anything in the way of contraries or buttons and rubber which may have
been missed by the sorters.

The rag loft should be fight and airy, and the women should have comfort¬
able .and convenient tables to work at, and they should also have a proper
arrangement of boxes or bags into which the separate grades may be sorted.
They should also be provided with boxes for rubber, buttons and contraries.
It is usual to pay the sorters extra for all the rubber and buttons which they
pick out, and these are weighed separately for each woman periodically and paid
for at an agreed rate.

TREATMENT OF RAGS

Great economy and efficiency may be introduced into the rag loft by the use
of a little care and thought, and by the provision of suitable and convenient
tables and appliances. In one case, the number of women employed was 80
for the sorting of about 52 tons of rags of various grades per week. By re¬
organizing the rag loft and providing convenient tables and receptacles, the
number of women was reduced to 30, and the same amount of rags was passed
through and dealt with far more thoroughly. Of these 30 women, only 16
were actually employed on overhauling the rags.

When the rags have been sorted they are ready to be cut up into pieces of
convenient size for the boilers and breakers. Formerly the rags were all hand-
cut by the women, but nowadays this slow method has been superseded by

[Bertrams Ltd.

Fig. 4.—Rag Willow and Duster, with Part of Cover Removed to show Wire-Covered

Drum and Spikes

the rag chopper. There are several types of machines in use, but they all
work on the same principle. The rags are .fed into the machine along a
travelling band, and pass first between ‘ripping’ wheels, which cut them up
lengthways into strips. They then pass between a heavy revolving knife and
a dead knife, and the strips are cut off into short square pieces. These machines '
are very efficient and will cut up any thin g from fine muslin to stout canvas
with equal facility. After the rags leave the chopper they are carried to a willow,
where they are tossed about and opened up, and they then pass to a conical
rag duster.

The rag duster (Fig. 4) consists of a kind of hollow tapering cone made
of iron or wooden bars securely bolted to circular metal ends. The ban are
fitted with iron spikes about 6 or 8 inches long, which project into the inside of
the cone, and serve to lift up the rags from die bottom as the cone revolves,'
and drop them down again on to the sides, which consist of coarse mesh, wire

MODERN PAPER-MAKING

cloth. This action loosens extraneous matter such as dust and dirt, and most
of it falls through the meshes of the wire cloth on to the floor below, from
which it is cleaned out at convenient intervals, of it may be sucked out by a
fan and blown into water.

The whole duster is enclosed in a dust-proof wooden box, the front side of
which may be removed for cleaning purposes. The cone is supported on four
wheels, on which it rides, with a steel band or tyre fixed to each end of the
cone to coincide with the wheels. In addition, there is a toothed wheel bolted
to the cone at one end, and this engages with a small pinion which transmits
the drive from the motor or shaft pulley.

The rags are fed in at the small end, and travel slowly down towards the
large end, from which they are discharged into suitable receptacles or on to a
travelling band.

After the rags have passed through the duster they may be again overlooked
by women, to remove buttons and other contraries which may have been
missed. This is best accomplished by having a travelling band about 3 feet
in width to carry the rags along after diey leave the duster. The women stand
on either side of the band and examine the rags as they pass.

Rag Boiling

It is necessary now to boil the rags with water under pressure, and in most
cases to assist the reducing action by means of caustic soda, soda ash or lime,
or sometimes by a combination of two of those chemicals.

The boiling is usually carried out in spherical or cylindrical revolving
boilers (Fig. 5), and in our opinion the best form is the spherical type, on
account of the ease with which it may be filled and emptied. While a spherical
boiler may be filled by one man, and almost empties itself, a cylindrical boiler,
even if it has two manholes, nearly always needs to be packed, and this necessi¬
tates the men entering it, and it also takes much more time and labour to
empty.

The boiler is first filled with the required amount of water, and the rags are
then put in. When the charge is complete the caustic soda liquor or soda ash
is added, the lid bolted on and the steam turned on.

The caustic soda to be used should be broken up and weighed, a nd then
dissolved in hot water, or a supply of the solution may be kept at the proper
density, and a known number of gallons can then he run into the boiler.

It is necessary that great care should be taken to ascertain the exact amount
of caustic soda which is being used for each boil, as otherwise endless trouble
will arise through too much or too little being used and the boil being spoilt.

TREATMENT OF RAGS

The steam pressure varies according to local conditions, such as the boiling
capacity of the mill, the nature of the rags, etc., but it can be taken as estab¬
lished that a long boil at a low temperature gives better results than a quick
and drastic boil at very high pressure and temperature. For all ordinary grades
of rags 20 to 25 lb. to the square inch is sufficient, and recording steam pressure
and temperature meters should be installed, so that the actual pressures and

[Messrs. R. Lord and Sons , Bury

Fig. 5.—Spherical Rag Boiler, Holding up to Sex Tons; Fitted with Large Manhole to Empty in One or Two

Revolutions

temperatures being used can be seen at any time. Thermostats are now available
for controlling the latter.

As soon as the pressure reaches the required level, the steam should be turned
off, and no more allowed in so long as the pressure keeps up. Reducing valves
and safety valves must, of course, always be fitted to prevent dangerous pressures
from being reached. The action of the alkalis on the rags is to remove grease,,
which is always present in rags, and to convert it into soluble soaps, which are
washed out in the washing water. The alkali also removes a great deal of
colouring matter, starch, size and other impurities.

2 6

MODERN PAPER-MAKING

When lime is used instead of caustic soda or soda ash, there is the risk of
the formation of insoluble compounds, and the rags are often hardened; never¬
theless, in some mills where the washing water is very soft, the addition of lime
seems to be absolutely imperative, otherwise it is impossible to get rid of all
the grease, and it is found coating the sides of the breaker. In other mills
where the water is very hard the use of caustic soda together with soda ash
gives the best results in practice.

Below is a table of the amounts of caustic soda and alkali used on various
qualities of rags where the pressure employed was 25 lb. per square inch. The
amounts were arrived at after long and careful trials, but of course they were
not always stricdy adhered to; the quality of the rags in each boil was always
taken into account, and slight alterations were made both in the quantities of
alkali and the number of hours of boiling. No more water than is necessary to
prevent the rags being ‘burned’ should be used, as the more concentrated
the alkali solution the more economical will the boiling be.

Booing Details for a i-Ton Boiler dealing with Rags for the Highest Grades of Writing Papers ■

(Pressure 25 lb. per square inch. Hot water washed)

Caustic Soda

Hours of Boil (Lb.)

Fines, ordinary. 4-5 25

Soda Ash
(Lb.)

Muslins, dean.

—

„ soiled .. .

—

5<5

New unbleached calico (‘greys*)

—

New white cuttings (second quality)

3-4

—

New lace cuttings .

—

Seconds, dirty white (outshots)

’ „ light .

100

5<5

„ low quality

125

Old light prints, good.

100

j» >» low .. ..

125

5<5

Cotton canvas.

125

Linen canvas.

250-300

112

French linens.

250

112

Cords, light.

125

S <5

Ticking, linings, etc.

150

Cotton healds .

—

White cotton tents.

100

Hlter-doths

100-200

56-112

Old white linens .

When the boil is complete the boiler is blown off, and the dirty water con¬
taining the dissolved grease, etc., is run away to the sewer or other convenient
place, unless the soda is to be recovered. The boiler is then filled up with hot

TREATMENT OF RAGS

water and rotated for a further period of about an hour. This washing water
is then run off, and the rags are ready to be emptied. It is advantageous if
they are then put through a conical washer of the same construction as the
duster already described. This washer rotates in running water, which carries
away more dirt and the remains of caustic soda, and greatly reduces the
time of the final washing in the rag breaker. The rags are emptied from this
washer into boxes on wheels and are ready to be taken to the rag breakers.

Rag Breaking

The rag breaker (Figs. 6 and 7) consists of an engine of exactly the same design
as a Hollander beater, except that it is always fitted with a washing arrangement,
and also contains a sand and button catcher. It has a bed plate and roll, which
can be raised or lowered. The sand catcher is formed by having a portion of
the bottom of the trough, along the midfeather and opposite the roll, cut
away, or cast below the general level of the trough. This cavity is about
4 or 5 feet long by 18 inches broad, and is covered with a perforated or slotted
plate.

The idea is that the sand and any heavy particles will sink to the bottom of
the trough and fall through the perforations of the plate, and thus disappear
below the level of the stuff and remain there until cleaned out after the rags
have been let down.

The button catcher is on the same principle, except that it is placed immedi¬
ately in front of the roll, and instead of a perforated plate it has a slotted plate,
so that the buttons, safety-pins, etc., may slip through sideways on.

Some breakers do not have these somewhat elaborate arrangements, but
depend simply on a narrow channel cut in the bottom of the trough, about
i£ inches deep by i£ inches wide, and extending from the comer of the mid¬
feather to the side of the trough. The washing is accomplished in two ways.
The first method is to have one or two drum washers, which may be raised
or lowered into the stuff at will by means of a worm wheel and pinion. These
washers are placed above the trough, as shown in the illustration (Fig. 7),
and they consist of a hollow drum, covered with perforated honeycomb bronze
plates, which are again covered with fine-mesh wire cloth. Inside the drum
is a bucket-lifting arrangement for catching the dirty water which comes
through the wire mesh, and for conveying it through one end into a trough
which carries it away to the drain. A later drum washer has one open side
connected to a pipe in the side of the trough.

The second method, which may be used either alone or in conjunction with

TREATMENT OF RAGS

MODERN PAPER-MAKING

the drum washer, consists in having a wooden cover placed on the roll, and
fitted with slots at each side, into which fit frames covered with fine-mesh
wire cloth. The water splashed round by the roll comes in contact with the
screens and a good deal passes through. To stop the washing action with this
apparatus it is necessary to have a wooden slide to slip in, in front of the
wire, so that the water splashes against the wood and falls into the trough
again.

The washing of the rags is effected in the following way. The breaker is
filled with water and the rags are thrown in, circulation being at first assisted
by means of a ‘stick’ or wooden paddle. When the required amount of rags
has been furnished, the drum washers are let down until the lower portion
of the drum is immersed to a depth of about 6 or 8 inches. The drums are
driven by means of a belt which is connected to the shaft of the breaker roll.
As soon as the drum is down, it starts to pick up dirty water and discharge it
into the trough, and so to the drain. In order to compensate for the water
being removed, fresh water is run in from the tap, and the washing proceeds
until the water leaving the trough is as clean as that coming in. When this
stage is reached the rags are clean and ready to be bleached.

The cover washing is earned on in much the same way. As the rags and
dirty water are splashed round by the roll against the wire screens, a con¬
tinuous flow of dirty water and small fibres passes through the screens and
away to the drains. This method is more drastic than the former, and a great
deal of fibre is lost through the screens.

During the period of washing the rags are being ‘broken in’ by the action
of the breaker roll on the bed-plate. The principle of the operation is to undo
the work of the textile manufacturer and brush out the rags into threads again.
The breaking goes on until all the material is ‘out of the rag’, and into
untwisted and brushed-out threads and fibres.

As the rags are cut and broken up, dirt and impurities contained in seams
and m the cloth itself are loosened and pass away in the water. At the same
time, any buttons and pieces of metal are cut or pulled off by the roll bars, and
sink to the bottom of the trough to be caught in the button catchers. Great
s is required in the breaking-in of rags, as they must not be cut up too much
or valuable fibres will be detached and will pass away in the washing water.

e ideal state is for the rags to be treated to such an extent that they are all

out o the rag, but that as many of the fibres as possible are still in a semi-
twisted state of yarn.

Irreparable damage may be done to the rags in the breaker if the breaker
man is careless m his handling of the roll. It is necessary for him to grip the
rags firmly at the commencement in order to tear them up, but as soon as

BLEACHING OF RAGS 31

this has been done the roll should be eased off" and the stuff brushed out
carefully.

Important fibrillation takes place in the breaker, and when strong rags are
being treated, care and skill in die breaking of them will make the beaterman’s
work much easier and quicker at a later stage. The washing and breaking
of rags should on no account be hurried, as this only means bad washing an d
often needless cutting up of the fibres, and consequent loss of small fibres,
besides preventing the proper defibring of the stuff in the beater, and making
the stuff work free on the machine.

Rags can never receive too much washing ; the more they are washed with
clean pure water, the better.

Rag Bleaching

After the rags have been thoroughly washed and broken in, they are ready
to be bleached, and this operation either takes place in the breaker itself, or the
rags may be emptied into potching engines on the floor below and bleached
with a bleaching solution.

Wherever it is carried out, the bleaching consists of adding to the rag stuff
a bleaching solution of known strength, which is prepared as described in the
chapter on bleaching. The dry weight of rags in the potcher is known, and
a sufficient quantity of bleaching liquor is added, in pails, to give the required
percentage of dry bleaching powder. Supposing the strength of the solution
is 6° Twaddell, then each gallon of liquor will represent \ lb. of dry bleaching
powder, so that if the breaker holds 100 lb. of rags, and it requires 3 per cent
of bleach to bring them to the required colour, it will be necessary to add
6 gallons of the liquor.

No hard-and-fast rule should be made as to the number of gallons to be
put into each grade of rags, but rather a standard for colour should be adhered
to, in order to give regularity to the stock. It happens often that one boil of
rags will only require 2 per cent of bleach, while the next may require as much
as 4 per cent to give the same colour. Such wide variations as this should
not, of course, occur if die sorting and boiling have been properly carried
out, but with some ‘prints’ great trouble is experienced in getting rid of cer tain
colours, due to the so-called fadeless dyes in use for printing shirtings and
such-like textiles.

It is the practice in some mills to run the bleached stock into steeps or
drainers and there to allow the bleach to exhaust itself. This method has the
advantage that it allows the bleaching in the potcher to be more rapidly carded
out, and it also enables the whole of the bleaching action of the liquor to be

32 MODERN PAPER-MAKING

exhausted, so that there is no waste. It entails, however, the provision of very
large draining tanlrs or chests, made of concrete and fitted with perforated
false bottoms. The liquor may be retained in contact with the stock for any
length of time, and then, by the opening of a valve the liquor is drained off
into a sump, and the rags are dug out and sent to the beater room.

One great disadvantage of this procedure is the fact that it exposes the
bleached rags to dust and dirt, which are always floating about, and it also
means that a great deal of labour has to be expended in digging them out
and conveying them to the beater room. To get over the difficulty of handling
the rags, they may be run, with the spent liquor, into hydraulic presses and
pressed into cakes ready to be taken up to the beaters or into a concentrator.
In this way they are more easily stored and kept free from dust.

The third method is to break and bleach the rags in a breaker situated
immediately above the beater. When the bleaching has been completed the
rags may be washed free of bleach liquor by putting down the drum washer
and r unning in fresh water for a quarter of an hour or so. When the beater
is empty the bleached stuff is run down straight into it, and so no time is lost,
no dirt comes in contact with the stuff, and no storage-room for half stuff is
required. This is satisfactory for good white rags, but to get the best colour
in low-grade rags the drainer method is by far the best.

The former method has the drawback that it is often necessary with a mixed
furnish of various grades of rags to break and bleach them together. It will
be obvious that this course is not always satisfactory, as such rags as linen,
canvas and cotton seconds do not require the same treatment in the breaker,,
or the same amount of bleach. This trouble is usually overcome by breaking,
bleaching and beating the various components of the furnish separately, and
then mixing them in the machine chests. This is the most satisfactory method
from every point of view, but it requires sufficient beaters, and, above all,
very large machine-chest capacity to take the contents of a complete battery of
beaters at one time. It is also necessary that the breakers should be of much
greater capacity than the beaters, as the density of stock in each operation is
very different.

Unless the bleached rags are carefully washed before being emptied to the
beaters, a small amount of ‘anti-chlor’ must be added to the beater when
fu rnishing , when it is otherwise permissible, in order to free the stuff from the
last traces of chlorine. If this precaution is not taken and much has been left
in the rags, endless trouble will be experienced from froth and variations in
the shade of paper.

The anti-chlors in general use are sodium sulphite and sodium hyposulphite,
and they depend for their efficiency on the percentage of sulphurous a dd, as

TREATMENT OF RAGS

S 0 2 , which they contain. The hyposulphite is more economical in use, but
is supposed to have an injurious effect upon the machine wires, owing to the
formation of free acid. This, however, does not seem to be really true in
practice, as we have run a wire for 18 weeks on a machine making 15 tons of
rag writing papers per week, and every beater was freed of excess bleach by
hyposulphite of soda.

Loss on Overhauling and Dusting

The following statistics were carefully made in the rag loft during 4 weeks,
in order to find the loss on each separate grade of rags from the time they
entered the mill until they were ready for the boiler.

Normally, the dust from both dusters was not weighed for each lot, as this
would entail a great deal of delay, but for the purposes of this trial the dust
was carefully weighed for each grade.

i* Second white cottons (dirty) (low-quality outshots):

Gross weight of bales .

Less tare (bagging, hoops).

Loss 4.34 per cent

Xess ‘mulch* and rubbish, buttons and unusable material
Loss 3.01 per cent^

Loss due to dust in first duster before sorting rags, 1.32 per cent \
Loss due to cutting by machine— i.e. second duster—2.7 per cent /
Total loss in passing through rag loft, 11.37 per cent ..

Cwt. Qr.

2 3

1 3

2 1

Lb.

Cwt.

Qr.

Lb.

Nett weight of paper-making material

$6 1 10

This would be considered a very good consignment.
The mulch is very low.

2. A good-looking parcel of old light prints (soft, coloured, clean
cottons):

Gross weight of bales .

Less tare (Hessian and hoops) .1

Loss 3.1 per cent

Mulch picked out . F .. .. 2

Loss 4.6 per cent

Dust from both dusters .1

Loss 3.91 per cent

Total loss 11.51 per cent .

48 3 13

2 4

0 15

3 1

5 1 20

Nett weight of paper-making material

43 1 21

A good parcel

MODERN PAPER-MAKING

3. A parcel of old light prints (mixed soft-coloured cottons):

Gross weight of bales .

Less tare .

Loss 4.06 per cent

Less mulch

Loss 7.77 per cent

Less dust from both dusters.

Loss 4.4 per cent

Total loss 16.23 per cent .

Nett weight of paper-making material
A fair lot.

Cwt. Qr. Lb. Cwt. Qr. Lb .

122 3 9

500
9 0 iS

4 3 3

18 3 21

103 3 16

4. English country seconds (mixed):

Gross weight of bags.

Less tare (bags) .

Loss 2.7 per cent

Less mulch picked out .

Loss 5.1 per cent

Less dust .

Loss 4.04 per cent

Less ‘thirds’ and low-quality cotton material
Loss 9.23 per cent

Total loss 21.07 per cent .

Nett weight of paper-making material
A very poo t r lot.

86 3 1

214
4 1 24

3 2 1

8 0 21

18 I 22

68 i 7

5. English country seconds (mixed):

Gross weight of bags ..

Less tare (bags)

Loss 2.02 per cent

Less mulch picked out
Loss 11.7 per cent

Less dfist ..

Loss 4.02 per cent

Less ‘thirds’.

Loss 11.3 per cent
Total loss 29 per cent

Nett weight of paper-making material

A very bad lot.

118 0 0

2 1 26

13 3 7

4 3 0

13 I 13

34 I 18

83 2 10

In addition to the various materials already sorted out as waste, there is a
further variety, usually called thirds, which consists of low-quality rags, darV
colours, very dirty pieces, etc., which, although not suitable to be included
in the grade being sorted, are nevertheless paper-making material.

TREATMENT OF RAGS

There are various ways of dealing with this. Some mills sell it back to the
rag merchants, while others use it in lower grades of paper, colours, etc., and
again, others boil it drastically and bleach it in gas chambers, and are thus able
to use it in ledgers and other coloured papers.

A certain amount of these rags was sorted out of some of the grades already
referred to during the trial, and the quantities are appended:

Cwt. Qr. Lb.

No. i.— _ _

No, 2. 3 o 15

No. 3

No. 4. 8 o 2i

No. 5

13 i 13

It will at once be seen that the amount of low-quality rags rises with the
mulch and rubbish.

The market value of the above rags is not more than 70 per cent of the
value of the original parcels from which they were extracted, and is often
much less. Besides the low-quality rags, another grade is sometimes sorted
out, consisting of strong pieces, such as light cords, canvas, ticking, brown linen
linings, etc. These rags are usually kept separate, and given more drastic
treatment and used for ledgers or strong thin papers. They may be boiled
and bleached in the same way as canvas, in which case they will not usually
come up to a very good colour, or they may be gas bleached. They will always
be yellowish in colour and not suitable for bright-looking papers, if their
strength is conserved.

It will be seen from the foregoing that the question of deciding on the
actual value of a'parcel of rags is a somewhat complicated business.

First of all the bulk of the rags has to be valued, then the various grades
picked out have to be given separate or lower values, and finally the prices
obtainable for the mulch, dust, and packing material, Hessian, etc., must be
taken into account.

As a result of many trials it has been proved, to our own satisfaction, that
it pays in every case to buy the best grades in the first place. This method
reduces to an amazing extent the number of hands required in the rag room,
and leads to much greater uniformity in the half stuif.

The following figures of ‘dust’ were obtained in four separate weeks. The
dust from each -duster was weighed separately. It may be noted that the heavy
dust, grit, etc., from the first duster has no value, while the fluffy dust from
the second duster may be sold as manure or for other purposes, for a pound
or two per ton.

MODERN PAPER-MAKING

Weight of Rags dusted and Dust collected at First Duster

Rags Dusted Dust

Cwt,

Qr.

Lb.

Cwt.

Qr.

Lh.

1st week

.346

2nd „

..290

3rd „

. 439

4-th „

. 339

(The dust is about 1.05 per cent and

is not very consistent)

Second Duster, after Rag Cutter

1st week

. 340

2nd „

. 333

3rd „

. 342

4th „

. 339

(The dust is about 2.7 per cent and is fairly constant)

CHAPTER IV

BORERS-BLEACHING-PREPARATION OF BLEACHING
SOLUTION-GAS BLEACHING

Boilers

There are three varieties of boilers in common use in the paper mill, Rotary
Boilers, Spherical and Cylindrical, and Stationary Boilers of many shapes and
sizes. The spherical rotary boiler is the most efficient, especially for dealing
with all classes of rags. The mixture of rags and liquor is most thorough and
continuous. There is less heat lost by radiation than in other types of rotary
boilers. They are very easily filled and emptied. The drastic churning action
which prevents clumps or balls of stringy rags being formed causes a certain
loss of fibre.

Owing to the difficulty of housing very large spherical boilers some mills
use those of cylindrical shape.

Owing to their shape and the great weight they have to carry, they have
to be built of thicker plates than the spherical boiler. Sometimes the larger
sizes are supported by revolving rollers on standards. Steel bands are fitted,
which make contact with the rollers. These help to take the weight off the
end plates and the trunnions. As the rags do not gravitate to the centre, but
roll continuously in one circle, there is more trouble with clumps of rags.

More labour and time are required in filling and emptying, it being neces¬
sary for a man to enter the boiler and spread the rags to the ends from under
the manholes, and drag them back when emptying. In both types steam and
water are admitted through the trunnions. They are also fitted with pressure
gauges and safety valves, and are revolved by worm and pinion gearing. -The
blow-off cocks are on the side opposite the manholes, and are shielded inside
by perforated metal plates to prevent loss of rags and fibre.

When used for scalding and disintegrating waste paper and broke, the
speed should be increased to' increase the internal friction. ’ One revolution
in three minutes is sufficient for rag boiling, but for broke scalding the speed
should be three to five revolutions per minute, which is about all that a heavy
boiler will safely stand.

Stationary Boilers for Rags .—The usual stationary rag boiler is dome-shaped.

MODERN PAPER-MAKING

The rags rest on a perforated plate at the bottom, and steam is admitted into
the space between the plate and the bottom.

The steam blowing upwards agitates the rags and forces the liquor through
the mass. The agitation is, however, very imperfect and the rags frequently
pack into dense masses, which then get little contact with the boiling liquor.

This type of boiler is very economical for use with good rags which do
not require very severe boiling. There is no loss of fibre through friction,
and litde expense for upkeep as compared with rotaries, which require power
to drive, oil, packing for glands, and repairs to running parts. The blow-off
steam may be used to heat water for rag washing, etc. It is safer to use, as
there is no mechanical strain apart from the boiling pressure. The rags may
be filled through an opening at the top, but they have to be dug out by hand.

There are still some mills, making hand-made papers, which boil their rags
in open tanks with wooden lids, but only rags requiring slight treatment can
be dealt with in this way.

For esparto, straw, etc., vomiting stationary boilers are u&d. These are
made much larger than rag boilers, a common size holding 5 or more tons of
esparto. When larger sizes are used, more elaborate and expensive devices
are necessary for washing. The stock rests on a perforated false bottom
through which the liquor drains and collects over the steam inlet pipe. The
latter is extended either outside or inside the boiler, so that the liquor and
steam are forced upwards to the top of the boiler and spread over the charge
by a spreader plate. A constant circulation of liquor is maintained by means
of this arrangement.

The boiler has the usual pressure gauge and steam fittings, and also a run-off
pipe to convey the spent liquor to the soda recovery plant.

It is usual nowadays to cut out esparto or straw from a Sinclair boiler by
means of a jet of water at high pressure.

Bleaching

In preparing half stuff for white printings and high-grade writing papers,
the colour obtained by boiling and washing the stock, whether it is wood,
esparto or rags, is dull or brown, and must be further whitened and made
pure. This is effected by the process known as ‘hipa rking ’

The laundry and washerwoman 1 bleach collars and other white garments
after washing. Bleaching has been in vogue for many years and the earliest
method is that known as sun bleaching; this consists in damping the material
to be bleached and placing it out in the sun, where ‘oxidation’, which is the

MODERN PAPER-MAKING

chemical reaction which causes bleaching to take place, occurs. This method
is very slow and uncertain.

Chloride of lime or ‘bleaching powder’ is still employed in man y milk
as a bleaching agent. It is prepared by passing chlorine gas over slaked lime.
The lime absorbs a large quantity of the gas and holds it so long as it is kept
dry and in air-tight packages, which consist usually of large wooden barrels.
The compound thus formed is called ‘bleaching powder’ and its formula is
taken to be CaOCl.Cl.

Ca—Calcium.

O—Oxygen.

Cl—Chlorine.

The powder contains about 35 per cent of available chlorine.

When this powder is mixed with water, two compounds are formed—
namely, calcium chloride, CaCh, and calcium hypochlorite, Ca(OCh). This
salt, Ca(OCl)*, is the actual bleaching agent, and forms oxygen by splitting
up thus:

Ca (O Cl) 2=CaCl a + 2 O.

When the oxygen splits off from the calcium chloride it is in the nascent state,
and it is then that it oxidises the colouring matter in the rags, esparto or wood
fibres.

Preparation of the Solution

The best way to prepare the solution for use in the mill is to have large
deep cast-iron tanks fitted with effective agitators. They should be tall and
narrow, and enclosed, except for an opening at the top to allow for the furnish¬
ing of the bleaching powder. The building in which the tops of the mixers
are situated should be well ventilated, as the operation of emptying the powder
from the barrel into the mixer is very unpleasant.

As the powder usually arrives at the mill in casks containing about 7 cwt.,
the capacity of the mixer should be not less than 1600 gallons. This will allow
plenty of room for sufficient water to be added to make the solution at standard
strength 6° Tw. (5 lb. to 10 gallons of water) with one cask of bleaching powder,
and allow for the lime sludge, which will occupy some space at the bottom.

An efficient and economical mixing plant is shown in the illustration
(Rg. 9). Though this seems a very elaborate arrangement and its working
at first sight rather complicated, it will be found that, by careful manipulation,
the utmost available chlorine will be extracted from the powder and the sludge
left quite innocuous, and there will be the mrmmnm of waste*

. - Weak L.*~a

BLEACHING

There are three mixers, fourth wash tank, etc.

42 MODERN PAPER-MAKING

The plant occupies part of three floors, the top floor containing the water
pipes and a weak liquor tank. Provision must also be made for lifting tackle
for emptying barrels, and driving gear for the agitators (not shown in the
illustration). The second floor serves as a support for the mixing tanks, though
an arrangement of girders is all that is necessary. Below the mixers is a tank
(No. 4), which is used as a final settling tank for the last mixing of lime sludge.
The store tank is covered in, and should be of ample size.

The method is to charge a mixer with water and bleaching powder. The
agitator is started and run for 20 to 30 minutes; it is then stopped and the lime
allowed to setde. This takes from 2 to 3 hours, often a good deal longer,
but plenty of time must be allowed for the lime to settle below the level of
the draw-off valves, which are about 12 inches above the bottom. If the solu¬
tion is drawn off before the lime has setded properly, the lime will foul the
pipes and store tank and get into the bleaching potcher, which is very un¬
desirable.

If the size of the mixing tanks (Nos. 1, 2 and 3) is taken at 9 feet deep
by 6 feet diameter, each will hold about 1500 gallons of solution, allowing
12 inches at the bottom for the sludge; the mixer is not filled to the brim on
account of the agitators splashing the liquid over the edge.

Two' barrels, approximately 7 cwt. each, are emptied into No. 1 with
fresh water. This ought to give a solution of io° to 12 0 Tw., which is too
strong for general use. To reduce it to 6° Tw. (working strength), No. 2
mixer is filled with water, and the two are run together to the store tank. If
the solution is under 12 ° Tw., of course a litde less water must be run from
No. 2. A Tw. hydrometer is constandy used to check this strength, and a
measuring stick marked off in ioo-gallon sections is necessary for the amount
of liquor or water in the mixers.

No. 1 mixer will now contain sludge, which must be again stirred up
with fresh water. If the mixer is half filled, the solution should stand about
working strength (6° Tw.). If it is stronger, a litde more water will correct
the density as it is let down to the store tank. If weaker, the strength may
be brought up from the charge in No. 2. No. 1 mixer may now be filled
with water and stirred for the third time, and the whole contents run into
No. 4 tank, with a light flush of water to wash out all the sludge.

This last lot, after settling, will give a weak solution, which may be pumped
to the weak liquor tank, from whence it can be drawn to furnish the mixers
instead of, or in addition to, fresh water. In the meantime, No. 2 mixer is
charged and worked in the same way, and then No. 3.

The mixers will thus be used in turn for making a strong solution, a work¬
ing solution and a weak solution for diluting purposes, and, by having three

BLEACHING SOLUTION

mixers, plenty of time is allowed for the settling of each charge. In fact, four
or more solutions can he made from each charge, the arrangements allowing
for endless variations of the procedure, besides keeping a constant and correct
solution in the store tank.

The three mixers, being regularly emptied to No. 4 tank along with the
sludge, are very easily kept clean. The store tank requires to be cleaned fre-
quendy, as a residue of Hme will be found at the bottom, which becomes
very hard and difficult to remove. No. 4 tank is fitted with a manhole or door
close to the ground level, to facilitate the removal of the sludge.

Where only a small supply of bleach has to be prepared, one or two mixers
will be sufficient, as the sludge can be stirred several times and smaller charges
of powder used.

Careful supervision has to be exercised over this process to see that the
stock solution is kept at regular strength, and that it is not run off to the store
tank until it is quite clear.

Liquid Chlorine may be obtained in steel cylinders holding about a ton, or
in tank wagons ready for use. It may be used either as a bleaching agent or
as an auxiliary to bleaching powder. As we have already seen, bleaching
powder contains only about 35 per cent of chlorine, the remaining 65 per cent
is simply the ‘carrier’ and of no use. It has, in fact, to be washed away as use¬
less sludge or lime mud, and it is difficult to get rid of in any case. About
75 per cent of this residue is lime, which can be combined again with chlorine
to form the same soluble bleaching agent as that which was extracted originally
from the bleaching powder.

By connecting a cylinder of liquid chlorine to the bleach mixer and allowing
the chlorine to run in while the agitation is going on, a very strong bleaching
solution is formed. The settling is much more rapid, and the chlorine will
have acted on the lime and combined with it, forming ‘hypochlorite’, so that
the amount of the lime left as sludge, in the form of calcium carbonate, is
very small indeed, only about 25 per cent of the normal amount left, when
liquid chlorine is not used.

This means that the mixers need not be washed out so often, and also it
reduces the number of mixings or agitations always required in the first method
to extract the whole of the chlorine. This process, as will be easily seen, is
simply the rechlorination of the free or ‘carrier’ lime present in the bleaching
powder.

Most mills have now abandoned the use of bleaching powder entirely, and
are making all their bleach liquor from lime and liquid chlorine.

Various special forms of plant have been devised in which this process
can be carried on, but as a general rule paper-makers have preferred to adapt

44 MODERN PAPER-MAKING

their existing bleach plant to the needs of the new process. This has been
done very successfully, and, in fact, when the bleach mixer is a plain cylindrical
tank, standing on end and fitted with a simple gate or horizontal type of agitator,
it makes what is possibly the best type of chlorination vessel for practical
purposes. It is desirable that the tank should be fairly deep (say at least 12
feet) and that it should have no baffles or other devices which may cause rapid
vertical currents.

The lime in the process should be a high-grade quicklime which slakes
easily. It is necessary that the temperature of the batch of milk of lime, before
chlorination commences, should not be more than about 65° to 70° F., and
thus a lime which will slake with cold or warm instead of hot water is an
advantage. The charge of lime should be slaked in as small a quantity of
water as possible. The thick milk so produced is pumped to the chlorination
tank and can then be cooled, as well as diluted, by filling up the chlorination
tank with cold water. During the chlorination the temperature should not be
allowed to exceed 90° F.

Chlorine is admitted to the chlorination vessel, in the liquid state, through
pipes reaching almost to the bottom of the vessel. A distributing device, such
as a coil perforated at regular intervals and lying close to the floor of the tank,
is a decided advantage.

The progress of the reaction between.the lime and chlorine is checked as
follows:

Remove a sample of the muddy liquor and allow it to settle in a hydro¬
meter jar.

Test with a Twaddell hydrometer graduated in fifths or tenths of a
degree.

When the test shows that the batch is nearing completion, samples
should be taken at close intervals and from these tests the actual end point
can easily be predicted.

This method of testing is quite accurate enough for works control purposes,
but the Twaddell to which the batch can safely be taken must be determined
in the first place by more exact (analytical) methods. A typical batch at one
mill was as follows (initial temperature 67° F.):

After i hour ..

»> * »» ■ -
„ 1J hours
„ 1 hour 40 min.

Temperature

Twaddell

70° F.

2.0° Tw *

78° F.

5-5° „

83° F.

9-4° „

84° F.

104 0 „

* These Twaddells refer to warm liquor five minutes aft^er sampling. They will, of course, be higher if the liquor
cools.

GAS BLEACHING

At this stage the batch was given five more minutes, and the control valve was
then closed. A sample was taken and twaddled. It was then 85° F. and 10.8 1
Tw. and the batch was finished.

When a batch is completed, it is allowed to settle, and is run off and the
sludge washed in the normal way. The quantity of sludge is small, and con¬
sists chiefly of impurities present in the original lime, with a little reserve lime
to maintain alkalinity in the solution.

In some mills where it is not possible to use liquid chlorine from tank
wagons, 17-cwt. cylinders may be used in an exactly similar manner. The
process control in these cases can be achieved, if desired, by weighing the
cylinder.

Gas Bleaching .—In this older method of bleaching by chlorine gas, the
chemical reaction is again one of oxidation. The chlorine gas passes through
damp half stuff, and the chlorine takes up hydrogen from the water or moisture
present, forming hydrochloric acid and setting free oxygen. This oxygen is
very active indeed, and will both remove colouring matter and reduce shive
or lignin, on which the ordinary bleach has had litde or no effect.

Great care has to be taken that the action is not too drastic and that the
stuff does not heat, or serious damage will be done to the cellulose.

For bleaching low-coloured rags and for destroying the shive in linen, a
gas bleaching chamber is very useful. A chamber holding 1 ton of rags is a
very good size, about 6 feet square by 8 feet in height, and having cross-bars
of wood on which the pulp is laid in order to allow the gas to penetrate all
through the mass. This chamber is closed and the door made air-tight by a
packing of wet paper. The retort should be on the outside and open to the
air, to obviate the risk of the attendant being gassed while putting in the charge.
The retort is of heavy cast iron and heavily lead lined. The top is also of lead
and is designed to fit on the base with a water channel, similar to a gas tank.
A lead pipe from the top communicates with the inside of the gas chamber.

For a ton of low-grade rags the following quantities of chemicals are re¬
quired: 30 quarts of sulphuric acid, \ cwt. of salt, £ cwt. of manganese dioxide.
The salt is placed in the retort with 6 gallons of water. The manganese dioxide
is added and the mass stirred into a paste. The top is then put on and the pipe
connected.

The sulphuric acid is filled in through a funnel on the top in, three separate
lots. Some steam is turned on and the chlorine gas and steam pass into the
bleaching chamber and mix with the rags.

" The process occupies about 12 hours and is very drastic. The quantities
are varied according to the stock being bleached.

Bleaching Methods .—There are two methods of bleaching, a rapid and a

4 6 MODERN PAPER-MAKING

slow. In the first, the bleach is run into the potcher after the stuff has been

broken in and washed. More bleach is required in this method to whiten the

stuff, and its strength suffers accordingly. In fact, an excess of bleach is run
in, and this excess has to be washed out and finally killed with anti-chlor.
With this method the colour of the pulp is said to go back’ a litde. The

second method is more economical. Sufficient and no more bleach is used

than is calculated to bring up the colour of the stock. The stuff is well mixed
with the bleach in the potcher and then run into tanks or steeps, where the
chemical action proceeds to its conclusion more slowly and naturally. This
gives a better colour and does not do so much damage to the fibres. Some
threads in rag stock that cannot be made to give up their colour with a rapid
bleach will be found to have become quite colourless in 24 hours. This system,
of course, requires a great deal of space for draining tanks, and entails more
handlin g of stock. Steam heating during bleaching is often resorted to, as
with esparto and wood pulp. While this is of great assistance in obtaining
a good white colour quickly, it requires to be used with caution; 90° F. is
the highest temperature that should be allowed. Above that the cellulose
will be attacked by the-bleach (oxidised) and lose strength to a very great
extent. The fibres will also return to a bad colour after cooling down.

Esparto fibres, in particular, are very apt to be destroyed by too high a
temperature, and will cause trouble by being slimy and soft and sticking to
the press rolls of the machine. A very little dilute acid is not to be despised
as an aid to obtaining a good colour, but great care must be taken when using
this. It should be added to the potcher very much diluted and in small quan¬
tities, otherwise chlorine gas will be evolved and escape into the atmosphere,
causing great discomfort to the workers besides loss of chlorine.

A very good accelerator of this type is about f pint of alum solution
(20° Tw.) in about 2 pints of water for 200 lb. stuff. Acetic or sulphuric acids
are sometimes used where the colour is difficult to bring up to a good white,
but none of these should be used except in unusual circumstances, and then
only with great care.

The cold bleaching of esparto and wood pulp is now generally carried
out in a series of bleaching towers. This system was introduced by Messrs.
Masson, Scott and Co., and has been almost universally adopted in esparto
mills. It takes up very little space and is economical and less cosdy than the
plants necessary for hot bleaching.

The towers are large vertical structures made of cast-iron or concrete,
lined with glazed tiles or glass, the usual size being about 8 feet in diameter
by 16 or 20 feet high. The bottom is sharply tapered, so that it is not possible
for the pulp to lodge anywhere. At the bottom of the taper is a bend, 2 feet

BLEACHING

in diameter, giving access to the circulating pump, which is a very efficient
apparatus, and can deal with the whole of the contents of the tower in a quarter
of an hour. There is a valve provided to shut off the contents of the tower
should the pump have to he dismantled, and also a wash-out valve for cleaning
.purposes.

The illustration (Fig. io) clearly shows the lay-out of the complete system.
The pulp or grass is broken up and washed in the breaker, and is then con¬
centrated by removing water with the drum washers, emptied and pumped
into the first tower, to which the strong bleach is added, or the first tower

may simply be used as a collecting tank for raw pulp, which is passed on and
bleached in the second tower. When the bleach is added, the pulp may be
circulated on to the next tower, and so on, until it reaches the last tower, or
if necessary it may be circulated round several times in the first tower by the
arrangement of pipes and a two-way cock. When the pulp is discharged
from the pipe into the top of the tower, it strikes a conical spreader plate,
which mixes it thoroughly and helps to exhaust the bleach. By the time the
pulp reaches the last tower it should be thoroughly bleached, and a sample
may be taken to examine the colour. If it is not suffidendy bleached, a further
lot of bleach liquor may be added, and the contents circulated round the last
tower several times until the bleaching is completed.

48 MODERN PAPER-MAKING

The battery shown in the illustration consists of a breaker fitted with two
ordinary drum washers, and is capable of dealing with the stock for 60 tons
of paper per week. The stuff is pumped from the breaker to the first tower,
which is fitted with two discharge pipes, one into the second tower, and one
back into the first tower. The first or fourth towers have this arrangement
of pipes and also spreader hoods for thoroughly mixing the pulp. The last
tower is fitted with a concentrator, by means of which the last traces of bleach
liquor are removed, after washing in the last tower, and the thickened pulp is
run or pumped direct to the presse-pdte chest.

All the pumps attached to the towers may be driven from the same shaft.

This arrangement of bleaching towers, worked in conjunction with a battery
of Taylor or Tower beaters, forms an excellent equipment for dealing with
esparto and wood-pulp stock.

The pulp is mechanically handled throughout, and is enclosed and away
from dirt and dust the whole time.

The first tower is used for adding the bleach and mixing, and the last tower
for washing. The capacity of the plant depends on the number of towers
installed, but with each tower holding 2 tons dry weight, and delivering this
quantity every. 4 hours it will be seen that the capacity of a five-tower plant
will be approximately 60 tons per week of finished paper.

Bleaching Wood Pulp— For bleaching wood pulp, an ordinary Hollander
type potcher of large capacity is generally used. This may be made of cast
iron or concrete lined with glazed tiles to assist circulation, and is fitted with
a large cast-iron roll with projecting bars.

Steam is always used to heat the stock after the bleach has been added,
but the temperature should not be allowed to exceed about 8o° F., or damage
will be done to the fibres and the colour of the half stuff will deteriorate if
it is allowed to He in drainers.

The action of the bleach is very rapid at first, so that a quick and thorough
mixing and circulation of the stock is necessary. When heat is used, the bleaching
is accomphshed in about 3 or 4 hours, but if drains are provided the stuff may
be emptied after about the first hour or so, and the bleaching completed while
the pulp is at rest. When, however, the bleached stuff is to be run straight
into the beaters, at least 3 hours has to be allowed, with from 6 to 10 per cent
of bleaching powder, calculated on the dry weight of pulp. The amount
required, of course, depends on how easily the pulp bleaches, the colour
required and the time available.

In this latter method, when the pulp is run straight to the beaters, the bleach
residues must be removed by the use of a drum washer and fresh water, and
it will usually be necessary to add a little anti-chlor until no trace of bleach is

BLEACHING

left. Unless this is done, endless trouble will be experienced in keeping the
colour of the paper from varying in shade.

In the former method, where the pulp is allowed to He in the drainer, it should
not be left for very long, otherwise it will begin to go back in colour, and that
part of it which is exposed to the atmosphere will turn yellow. The bottom
portion nearest the floor of the drainer will also discolour badly, and will retain
a good deal of water and bleach residues, unless the perforations in the false
bottom of the drainer are kept clean.

[Messrs. James Bertram and Sons Ltd .

Fig. ii.—Three-Drum Washing and Concentrating Machine, for Wooek-pulp,

Rags or Esparto Grass

Bleaching should always be carried out with the stock at as thick a con¬
sistency as possible. The density, of course, will depend on the type of marhinp
in which the bleaching is carried out, but even if it is in an ordinary Hollander,
die stock should be as thick as possible.

A cheap, speedy, and continuous method of drying bleached pulps to about
70 per cent moisture or less is sorely needed by many milk to-day. It is true
that there are several Rotary Vacuum Filters on the market, but these are
troublesome and inefficient in many ways. Some of them work quite well
on wood. On rag stuff and esparto there is the presse-pdte which does well in
some mills and is continuous. There are hydrauHc presses and hydro-extractors,
but these are both slow and intermittent. The continuous screw press has not,
unfortunately, been brought to a sufficient satisfactory state of perfection to
be suitable for all types of fibres. The multiple drum concentrator (Fig. 11)
is used in many mills, and this is satisfactory where the stuff can be taken straight
to the beater.

CHAPTER V

REDUCTION TO HALF STUFF-WOOD PULP-
ESPARTO GRASS-STRAW

Wood pulp is the most important raw material at present known to the paper-
maker. At the present time, the paper-maker in Great Britain need not
necessarily concern himself with the methods employed in the isolation of the
cellulose horn wood, for, unlike esparto, it comes, except in one or two cases,
into the country already prepared for making into paper. Wood pulp is divided
into two distinct classes: first, mechanical’ wood, which is simply ground soft
wood, and is in no sense a pure cellulose; and second, ‘chemical’ wood, which
is wood cellulose chemically isolated from wood.

It must be recognized that wood pulps cannot be rigidly classified and
graded. The physical properties are usually of chief importance, and the
fibrous nature of the material does not lend itself to precision testing in terms
of rigid specifications. However, the days of offering pulps merely by samples
are passing. Testing at the pulp milk is usually thorough, and careful control
is always rewarded by better results in the market. Testing by the paper mills,
board mills, and speciality consumers has now reached a high plane in many
laboratories. The test of practical use in the paper mill tells the second, and
decisive, half of the story.

The basic factor is the pulp wood, its species, rate of growth, condition, and
preparation.

The wood-pulp business was built up largely on spruce. The fibre length
(about 3 mm.) is just right for most paper and board products. Spruce is low
in resin content and therefore adapted to mechanical, acid, and alkaline pro¬
cesses. The wood is unusually uniform and the colour is bright. The various
species of spruce—‘whitewood’ (Picea excelsa ) in Northern Europe; white
spruce (Picea glauca), black spruce (Picea mariana ), and red spruce (Picea rubra)
in North-Eastern America; and Sitka spruce (Picea sitchensis ) on the west coast-
have much the same fibre characteristics, but vary somewhat in density and
pulping action.

The dosely related spedes, such as balsam fir (Abies balsamea), of lower
density, in. Eastern Canada and the United States, and white fir (Abies grandis)
on the Padfic coast, have naturally come into use to supplement the demand

WOOD PULP

for spruce type of fibre. Closely parallel, especially for chemical pulps, are
eastern hemlock [Tsuga canadensis) and western hemlock [Tsuga heterophylla),
very low in pitch, which is the main wood for the new industry on the west coast.

Pine has been taking a larger place by reason of its suitability for the alkaline
sulphate process, which dissolves the higher content of resins. ‘Redwood*

[Nokia Aktiebolag

Fig. i 2.—Floating Logs down from the Forest

[Pirns sylvestris) in Northern Europe and jack pine [Pinus banksiana) in America
are so much like spruce in fibre characteristics that they are now the usual
raw material for the best grades of kraft pulp. The southern pines, long leaf
[Pinus palustris), slash [Pirns caribaea), loblolly [Pinus toeda), and short leaf [Pinus
echinata), with coarser fibres and more difference between springwood and
summerwood, have become very important for liner board and medium-grade
papers.

52 MODERN PAPER-MAKING

Hardwoods are fundamentally different because the fibre length is so much
less (i to 1.5 mm.), and the pulp can therefore never take more than a minor
place in the pulp and board industry. For many years the main species was
aspen, or poplar (.Populus tremuloides), a soft hardwood, for the manufacture
of bleached soda pulp in America. The scope is steadily widening, and various
species of birch, beech, maple, chestnut, cottonwood, gum, etc., have been
added to the list. Aspen and beech are used in Europe. Eucalyptus and other
hardwoods are being developed in countries not endowed with suitable soft¬
woods. The trend seems to be towards sulphite or sulphate cooking, because of
their greater convenience and efficiency compared with the caustic soda process.
The use of hardwoods will probably extend in the field of fine papers and
perhaps considerably for chemical purposes where fibre size is of no importance.

In general it can be said that the limited supply of the spruce type of pulp-
wood in the different northern countries of the world is being, and should be,
reserved mainl y for sulphite and mechanical pulps. Other species will play
an increasing part in meeting the world’s pulp requirements.

On looking over a collection of wood samples it is interesjting to note that
the brightness, fine texture, and uniformity of the pulpwoods, particularly
spruce, fir, aspen, stand out as raw material giving the appearance of being
best suited to pulp manufacture.

Wood preparation deserves mention as a reminder of seasoning to reduce
pitch troubles and to aid penetration in the cooking of sulphite pulps, knife
barking to ensure best cleanliness and brightness for the highest grades of
unbleached sulphite, and careful chipping to aid uniform cooking of all chemical
pulps.

The chief countries engaged in the manufacture of wood pulp are Scandi¬
navia, Canada and the United States, Finland, Germany, ‘Czecho-Slovakia and
Russia—in other words, those countries which have extensive forests and
almost unlimited water-power. Water serves "as the chief means of transport
of the logs after they have been cut down in the forests, besides supplying the
power at the mill. The trees are felled and stripped, and rolled, dragged or
carried on light railways to the river, where in the winter they are piled on
the ice to await the spring thaws. They are then floated down the river to
large traps, formed of wooden booms, close to the mill.

Trees immediately required are floated into the mill. Those to be kept
in stock are built into huge piles to be used in rotation when the river is frozen
or when the felling ceases. During the passage downstream a proportion of
the bark is rubbed off, but this is not sufficient. They are cut up into short
lengths of about 2 feet, and are then ‘barked’ in a machine or by hand, when
they are ready to be made into either mechanical or chemical wood pulp.

WOOD PULP

Mechanical Pulp

Those intended for mechanical pulp are passed to the grinders after having
all knots drilled out. The wood pulp grinder consists of a revolving stone of
about 3f to feet diameter and 2 to 2\ feet on face. This is mounted on
a heavy shaft and enclosed in a heavy metal case on which are strong metal
boxes fitted with hydraulic pressure arrangements to hold the logs and keep

them pressed against the revolving face of the stone. Inside the case, behind
<* arh box, is a water spray which washes off the particles of wood as they are tom
from the log.

The stone is kept rough on the tearing surface by frequent dressing with
special tools; the quality of the pulp and the output depend very much on the
condition of the stone. If the stone is smooth the output will be small, and
the pulp will be fine and ‘dusty’ on the paper-making machine. Coarse stones
give a greater output of longer-fibred pulp.

There are several kinds of mechanical pulp, named according to the method
of grinding—viz. cold ground, hot ground, and cooked or steamed — i.e.

MODERN PAPER-MAKING

‘brown’. Hot-ground pulp is that which is tom off the log in the presence
of very little water, so that the contact point is made hot by the friction of the
stone and the pressure employed. This hot-ground pulp is said to work less
free than the ordinary cold-ground, but more difference is often observed
between two consignments of cold-ground than between hot- and cold-ground
pulp.

Cold-ground pulp is ground with a sufficiency of water to keep the stone

cool and carry off the fibres. The third quality-is made from logs that have
been steamed or boiled before grinding, and is a stronger-fibred pulp. About
25 per cent more power is required to grind the cooked logs.

The pulp fibres, after being carried away from the grinders, are put through
strainers and ova: a presse-pate machine or concentrator.

Any coarse particles which will not pass through the screen or strainer may
be collected and re-ground.

WOOD PULP

After the web of pulp has been concentrated it is pressed and wound up
on the top press roll until a sufficient thickness is obtained, when it is cut off,
laid in a pile about 2 feet long by 18 inches wide and pressed in hydraulic presses
for the removal of water. At this stage it contains about 50 per cent moisture,
and it is usually exported in this state, ready to be made into paper.

Mechanical wood pulp is used chiefly in the manufacture of newsprint,
of which it forms approximately 80 per cent; it is used also in the m anufa cture
of cheap printings, poster papers, boards and wrappings. It cannot, however,
be used alone, and must have a proportion of chemical wood pulp or other
stronger fibre mixed with it, in order to carry it over the machine.

Owing to the impure state of the cellulose contained in mechanical pulp,
papers made from it are gradually destroyed by oxidation, and they cannot
therefore be exposed to light, air, or damp atmosphere for any length of time
without being seriously affected.

The mechanical process is surprisingly successful in view of the direct
transition from wood to pulp by the wet grinding of pulp wood blocks on
abrasive stones. The grinder represents comparatively low capital cost, high
production, and moderate conversion cost where power is cheap. This is a
case where the best pulpwoods, such as spruce, have to be used for the cheapest
process, with serious loss of fibre length, but with preservation of bright colour
and cleanliness. The yield is over 90 per cent by weight of the dry wood
and over 95 per cent if screenings are taken into account. It would appear
that ground wood tonnages for world consumption will moderately increase
with the use of still higher percentages in newsprint and for further use in
board and low-grade prin ting papers.

To produce coarser fibres for insulation boards, hard-pressed board, and
other rapidly increasing substitutes for lumber, it is possible to disintegrate
wood waste by steam explosion, by dry shredding in ha mme r mills, by wet
refining, or in the case of wood blocks by crude grinding.

The semi-chemical processes have not yet reached great importance, but
much progress may be expected. Perhaps these pulps will not come into the
trading market in large tonnages, for the same reason that groundwood is
best adapted to direct conversion from slush pulp to the finished product. One
need only mention the wide range between mechanical pulp yield at over
90 per cent and chemical pulp yield below 50 per cent to realise the future
scope for medium cost pulps made by some combination of mechanical and
chemical treatments. Reasons for the delay in development have probably
been the low capacity and poor efficiency of refiners (compared with grinders
for pulpwood blocks), the tendency to lose bright colour of fibre in the presence
of weak chemicals, and the inherent difficulty of limi ting the cost of a two-stage

5 6 MODERN PAPER-MAKING

process. At the upper end of the scale is the attempt to make the wood fibres
flexible with minimum loss of yield. Longer fibres can be expected by pro¬
gressive removal of hemi-celluloses and lignin in conjunction with mechanical
separation of fibre bundles. High yields and cheap sources of wood are great
incentives to develop grades of semi-chemical pulps suitable for various boards
and papers.

Chemical Wood

The Sulphite Process .—The sulphite process dates back to about 1870 and was
first used in America. The process consists in treating vegetable substances
containing fibres with sulphurous acid in water, and heating them in a closed
vessel or boiler under pressure. This action dissolves the incrusting matters
which are bound up with the fibres, and a fibrous product is left, suitable for the
manufacture of paper. During subsequent years several modifications of the
original process were introduced, the chief among them being those of Parting¬
ton, Ritter-Kellner, and Mitscherlich. The preparation of the wood must be
carefully carried out; all rotten pieces, knots and blemishes have to be cut out
and the bark shaved off, usually by hand.

Some fresh knots may be left in during the boiling, which has little or no
effect upon them, and caught later in the screens. The cleaned and sorted logs
are passed to the chipper, which shaves them into chips about 1 by | inch.
They are then carried on a travelling band and over a chip screen to the digester
house, where they fall through hoppers into the boilers.

The wood used for each boil should be of the same kind and preferably
of the same age. It is also an advantage that it should all contain the same
amount of moisture. Green or freshly-cut wood is most easily reduced by
the sulphite process. The wood in most general use is spruce or fir, though
other coniferous woods may be used.

The boilers or digesters are built of steel, but on account of the corrosive
action of the bisulphites and sulphurous acid a lining has to be added for pro¬
tection. Innumerable experiments were tried, none of them very successful,
to utilise a lining of lead, but now acid-resisting tiles or bricks and coatings of
acid-proof cement are used.

The digesters are cylindrical in shape and for most processes they are vertical,
although horizontal boilers are used in some cases. They are usually very
large, 40 feet in height by 14 feet in diameter, or larger. They have manholes
at top and bottom for filling and emptying.

They are heated by direct steam or, as in the Mitscherlich process, by steam
coils made of lead, which are sometimes 2000 feet long. The digesters are

WOOD PULP

fitted with thermometer tubes, safety valves, blow-off cocks, etc., and also cocks
for drawing samples of the liquor and pulp for testing purposes.

The bisulphite liquor for digesting the wood is made in the following
way:

Sulphur or iron pyrites is burned in an oven with a carefully regulated
supply of air. In this way sulphur dioxide gas is formed, which, after being
cooled, is passed into the bottom of a tower, in which is stacked ordinary
limestone. Water is made to trickle down and over the limestone, and the
gas passing upwards mixes freely with it. The sulphur dioxide, or SOs, is
absorbed by the water, H 2 0 , and forms sulphurous acid, H 2 S 0 3 :

h 2 o+so 2 =h 2 so 3 .

This solution acts on the limestone (carbonate of lime) to form sulphite of lime,
water, and carbon dioxide:

H 2 S 0 3 +CaC 0 3 =CaS 0 3 +H 2 0 -t-COa.

Ultimately bisulphite of lime is formed by the further solution of limestone.
During the reaction free sulphurous acid is also formed, and it is this acid which
is required for the reduction of the wood.

The sulphite process is largely confined to softwoods of low resin content.
Notable advances are its advancement to pine of medium resin content, and
its increasing application to hardwoods. From the chemical point of view
the sulphite process represents a comparatively severe hydrolysis of the fibre
in removing lignin and part of the lower carbohydrates from the wood. The
pulp fibres are very flexible, but some strength is sacrificed. The great ad¬
vantages are bright colour of the unbleached pulp for direct use and ease of
bleaching, coinciding with the unconscious desire of the buying public for
white papers. Particularly in Europe long experience in operation and wide¬
spread adoption of digester circulation has resulted in high quality of sulphite
pulps. The yield of unbleached sulphite for paper-making usually varies from
45 to 50 per cent by weight of the chips, depending on wood species, bleach-
ability, and other factors. This is a considerable range, amounting to 10 per
cent difference in tonnage from the same weight of wood. There is no certainty
that world tonnage of unbleached sulphite will materially increase, but
bleached sulphite presumably will extend, for chemical uses in particular.

Here may be mentioned some of the modified sulphite processes. The
Mitscherlich method of indirect heating and long cooking has become too
expensive for general competition. The minimum change in the standard
sulphite cooking liquor is the use of magnesium base in place of calcium base.
Sodium bisulphite in America and Scandinavia is applied to resinous woods

5 g MODERN PAPER-MAKING

or in relation to the purification of the final bleached fibre. The ammonium
bisulphite process in Norway aids the recovery of valuable by-products from
the spent liquor, and also has a bearing on the pulping of resinous woods.
The sodite process in America employs alkaline sodium sulphite and yields
a more distinctive grade of bleached pulp.

Soda Process.—In this process the chipped wood is boiled with caustic soda
nnfW pressure. No attempt is made to drill out knots or rotten parts of logs,
as the soda process is so drastic as to eliminate these impurities. The resulting
pulp is of a brownish shade, and does not bleach to so good a colour as sulphite
pulp. The fibre is long, strong, and bulky.

Pulp from poplar, produced by this process, is very soft and absorbent.
It is used in certain papers as a substitute for esparto and for cheap blottings.

This was the first chemical method of boiling pulp. The caustic soda
treatment is satisfactory for aspen and harder deciduous woods to produce
bleached filler fibres. Actually these mills are confined to America and are
not expected to increase materially, because a greater number of sulphite and
sulphate mills in the various forest countries can handle any hardwoods within
reach. Yields are lower than by the sulphate process, which has the protective
action of sodium sulphide.

Soda Sulphate or Sulphate Process.—This is simply a variation of the soda
process. In the process of soda recovery, sodium sulphate is added to make
up the loss of soda, and the liquor comprises a mixture of caustic soda, sodium
sulphide, and sodium sulphate. This process has extended rapidly during recent
years. The alkaline nature of the cooking liquor (caustic soda and sodium
sulphide) makes it of universal application to all species of pulpwoods, including
the very resinous. The trend is naturally towards the pines which grow both
in northern and southern countries and which are subject to less competition
than spruce. This means that sulphate pulp mills have the widest distribution,
sometimes an advantage in proximity to markets. The special feature of the
sulphate process is the ease of preserving the inherent strength of the wood
fibres. The alkali resolves the bark and knot specks, and the shives to some
extant are obscured by the brown colour of the pulp. The yields are close
to those of unbleached sulphites, but tend to extend lower for easy bleaching
sulphates. Total consumption of sulphate pulp has now reached half the
sulphite tonnage, and promises to account for a larger proportion in future,
perhaps chiefly for boards and in terms of bleached sulphate grades for many
papers.

In connection with chemical pulp cooking processes there is a distinction
to be noted between sulphite and soda in the mechanism of penetration. In
the add process the cooking liquor enters the chips almost entirely along the

WOOD PULP

grain of the wood, whereas in the soda processes the liquor is able to penetrate
the chips in all directions.

After the pulping processes come the usual operations of riffling to settle out
heavy impurities such as grit, and screening to separate knots, fibre bundles,
and bark specks as carefully as possible. Kollerganging, rod-milling, or other
light brushing treatment is often applied to krafi: pulps. The coarser fraction

[Nokia Aktiebolag

Fig. 15.—’Transporting Logs into the Mell

of mechanical pulp will benefit in strength and uniformity if present attempts
to brush out the fibre bundles are successful.

Special mention should be made of fibre selection. Chemical pulps are
sometimes treated to separate the longer, stronger fibres of higher purity. In
the case of sulphite pulp, the removal of most of the pitch with the medullary
ray fibres is also a feature.

The drying of chemical pulp over cylinders has been superseded in a number
of mills by vacuum drying at low temperature in the absence of oxidising
atmosphere, or by hot-air drying at comparatively low temperature, with a
slight gain in ease of beating, brightness, and strength of pulp at the paper
mills. Care in the baling of pulp for shipment has reached a high standard.

6 o

MODERN PAPER-MAKING

Bleaching and other chemical treatments of pulp may be looked on as
processes of secondary digestion. Great advances have been made in recent
years with the better knowledge of cellulose chemistry.

The bleaching of mechanical pulp is based on the reducing action of bisul¬
phites or hydrosulphites, which brighten the yellowish colouring substances
in groundwood without affecting strength or yield to any extent.

Chemical pulp bleaching has undergone revolutionary changes during the
past ten years, based on laboratory methods known much earlier. The use
of over half the total chlorine in the first stage for direct chlorination of the
unbleached pulp at low temperature and consistency with thorough mixing,
permits rapid formation of lignin products without appreciable change of the
cellulose itself or reduction of shives and bark specks. Neutralising the hydro¬
chloric acid formed in this reaction brings the chlorinated products into solu¬
tion, and washing avoids the subsequent bleach consumption by coloured
liquor left in a single-stage process. Second stage bleaching with calcium or
sodium hypochlorite at low temperature and high density of pulp favours the
oxidation of colouring matter and resolution of bark specks and shives under
the mildest conditions. After again washing the pulp, a small percentage of
hypochlorite brings up the desired whiteness under the best conditions for
control. Caustic soda treatment, as a separate step or mixed with bleach
liquor, is applied to dissolve hemi-celluloses. Acid treatment as a last stage
reduces the ash content. It is perhaps superfluous to mention that numerous
modifications of sequence, chemicals, and conditions are practised in both batch
and continuous systems. The significant point is that multi-stage bleaching
has yielded higher strength and purity of bleached sulphite pulps in relation
to whiteness, and has permitted the economic bleaching of strong sulphate
pulps for the benefit of the paper and board industry. The usual loss of fibre
weight in the bleaching of paper-making grades is in the order of 5 per cent
of the unbleached pulp—more or less depending upon the bleachability and
other conditions—resulting in overall yields of 42 to 45 per cent from the wood
to ordinary bleached sulphite.

Next comes the detailed grading of wood pulps. The dividing lines are
not sharply defined because cooking degree, for instance, must be linked with
strength figures; special characteristics are sometimes the determining factor,
and uses overlap pulp qualities. It should also be remembered that grades are
sometimes interchangeable—for example, semi-bleached sulphate serving in
place of unbleached sulphite for certain papers.

Mechanical pulp grades may be named extra free, free, medium free, and
slow. The drainage rates become progressively slower, due to increasing
hydration and fineness of fibre. In general it can be said that the mechanical

WOOD PULP

pulps give maximum bulk, high opacity, good absorbency, comparatively low
burst, low tear, and very low fold.

Extra free groundwood extends through the range from short coarse fibres
of low strength, representing maximum production and economy of manu¬
facture, to long flexible fibres of good strength, representing high cost of
production. The board industry is perhaps the chief consumer, the desired
properties being bulk and fold. The small tonnage of dry mechanical pulp
for long-distance transportation is of this grade, as the fibre bonding properties
are low enough to permit easy breaking up of the dry sheets, and there is fibre
length to spare in the refining operation.

Free pulp is the standard grade for newsprint in this country. The strength
should be as high as possible, and the shive content at a mini m u m. Com¬
paratively high freeness is needed because the moist-baled pulp undergoes
slight refining in the breaker beaters and jordans; the use of china clay further
lowers the drainage rate on the Fourdrinier wire; and, furthermore, the sheet
is rather high in basic weight. In self-contained mills converting direct from
slush pulp, the free grade is usually made for boards and coarse papers.

Medium free groundwood is the general utility grade. Strength is higher,
fibre size is more uniform, and the drainage rate is rapid enough for printing
papers of various kinds, as well as for thin high-grade boards. The many
self-contained newsprint mills in forest countries aim towards this grade for
high-speed machines.

Slow pulp is a speciality for coating papers, telephone directory, tissue and
other better-class groundwood papers. Freedom from shives and grit, best
cleanliness, high brightness, and good strength are usually desirable, and the
slow rate of drainage is unavoidable. Opacity is highest by reason of fine
grinding.

Bleached mechanical is a special product which has reached some importance
and may increase in future with the demand for cheap book and magazine
papers. Pulp of the medium free grade is usually chosen for this after-treat¬
ment in the case of bale shipments, or slow pulp for the best possible printing
papers made from slush stock. Uniform brightness, high cleanliness, and
good strength are desired. Western hemlock is an example of a wood which
yields mechanical pulp of reddish colour, and bleaching is sometimes practised
to bring up the brightness to the spruce standard.

Semi-chemical pulps are not yet very important or definite as to grades,
but the following comments will serve as examples:

Brown mechanical pulp, based on the steaming of wood blocks before
grinding, is a border-line grade which might be classified with either mechanical
or semi-chemical pulp. Although the pressure treatment is with steam only.

MODERN PAPER-MAKING

the process involves the extra step of softening in addition to grinding. The
steaming results in a dark-brown colour which limits the i use of the pulp to
products of the leather board class. The drainage rate is in the range of very
high freeness. The fibres are comparatively long and.flexible, with much
better tear than with ordinary groundwoods, and about the same bulk.

Various methods of heating pulpwood blocks under pressure with weak
reducing liquors of the sulphite class have been tried to produce extra-strong
groundwood of bright colour. The fibre strength approaches that of unbeaten
sulphite, but the drainage properties tend to be slow. Cleanliness is excellent
because the laundering of the blocks removes adhering dirt and brightens the
exposed layers. Yields can be 80 to 90 per cent by weight of the dry wood,
as the screenings are easily refined. This general grade gives promise of finding
some economic use for low and medium grade white papers, and even suggests
the possibility of a straight line process for newsprint mills by treating all the
pulpwood without pressure.

In the intermediate range the most common example is short, brown,
bulky fibre produced by mild alkali cooking of extracted chestnut chips followed
by r efinin g to brush out the fibre bundles for the manufacture of corrugating
board.

Close to the border-line of chemical pulps is the quick cooking of southern
pine at high yields for the manufacture of bulky kraft liner board. Only part
of the inherent fibre strength of the kraft need be developed by the refining
treatment, and the product does not require thorough brushing out of fibre
bundles.

High-yield unbleached sulphite has recently been developed for use in the
self-contained type of newsprint mill. The digester is blown before the fibres
are thoroughly, separated, and the washed pulp is brushed out in a modem
type of refiner before going to the screens. Uniformity and cleanliness are
not the highest, but unbeaten strength and bulk are satisfactory, and an all-over
yield of 55 to 60 per cent means cheaper furnish.

Sulphite pulps are classified as unbleached, bleached, and semi-bleached.
The general characteristics are excellent whiteness, quick hydration, medium
strength, reasonable cleanliness, and low opacity of the fine flexible fibres.

Extra-strong sulphites represent minimum cooking to reach fibre separation
and best possible strength. Careful screening has to be practised to reduce
the shives and dirt. Depending pardy on the wood, cooking can be adjusted
to give either quick beating, maximum burst, and maximum tear. Ordinary
.uses are for M.G. papers and other extra-strong hard sulphite sheets.

Medium strong grades include many well-known brands of sulphite, and
the uses cover a wide range. Brightness, uniformity, and cleanliness have

WOOD PULP

reached high standards. Not all the desired characteristics can be combined
in any one brand, and this raises the general reminder (applicable to other
grades also) that it is sometimes better to choose another brand instead of
asking the pulp mill to depart from its established quality. The board pulps
are usually tough in relation to heavy beating, comparatively high in fold and
tear, and as opaque as possible. For printing papers, softness, high cleanliness,
and good opacity are desirable. Newsprint sulphite for sale in the European
market is much superior to the grade ordinarily used in self-contained news¬
print mills; the trend towards softer fibre for better printing is also in the
direction of higher cost at the pulp mills.

Greaseproof pulp is specially hydrated by cooking to develop good ‘blister’
at the end of the beating scale.

Bleachable sulphites in Europe range from about 14 to 20 per cent bleaching
powder consumption by single-stage test. In this grade it is customary to
hold the bleachability regular within reasonable limits, and two or three steps
through the range are recognised. Cleanliness is a particular feature, because
the pulp is so often to be bleached in single-stage plants. Strength naturally
tends to decrease with lower bleach consumption.

Easy bleaching sulphite in Europe is still more carefully cooked and sorted
for bleachability in three or four steps between 6 and 13 per cent bleach con¬
sumption. In America comparatively little sulphite is cooked below the 10
per cent figure except by the silk pulp mills, and the range up to about 18
per cent is known as easy bleaching. Cleanliness is again a vital factor because
the small requirement of calcium hypochlorite cannot deal with excessive
dirt. Unfortunately this soft cooking of sulphite distributes more specks
from ingrowing knots through the pulp, but on the other hand these softer
particles are more readily brightened by bleaching than in the case of stronger
sulphites. It is worth noting that pitch troubles tend to decrease from extra¬
strong sulphite at one end of the scale, down to soft easy-bleaching sulphite
at the lower extreme. Easy bleaching is particularly well suited to mix with
esparto.

In Europe, several brands of easy-bleaching aspen sulphite are available for
bleaching at-the paper mills. Another hardwood sulphite in this range is
eucalyptus. *

In the range of semi-bleached sulphites there are not many examples. It
is a question whether the pulp mills should develop a grade from strong sulphite
for direct use in the semi-bleached state, because bleaching to yellowish colour
consumes most of the bleach sufficient to reach high white colour and the
strength does not approach that of semi-bleached kraft. Recently the idea
has been modified to supply an easy bleaching sulphite of much better strength

64 MODERN PAPER-MAKING

than can be reached by soft cooking, this being accomplished by starting with
bleachable pulp.

Strong bleached sulphites include several varieties. Tough papers and
boards may call for fibre of yellowish-white colour which will stand up to
heavy beating. Bond pulps are adjusted to fairly quick beating and high
burst. Multi-stage bleaching has extended the range to the bleaching of com¬
paratively hard sulphites, and in general has given better strength and purity at
a given whiteness, as well as yielding whiter pulps of excellent stability compared
with earlier days.

Soft bleached sulphites are ordinarily used for book, magazine, and other
printing papers. High-white colour, high cleanliness, good bulk, and opacity
become more important than strength. This is the type of pulp which the
pulp mills with older equipment can continue to make. Speciality qualities
are made for genuine vegetable parchment, photographic papers, absorbent
tissues, and other uses with control of highest whiteness and cleanliness, low
pitch, low content of iron and copper, low ash, etc.

Bleached hardwood sulphites have been coming into more prominence.
In Europe, bleached aspen sulphite of excellent whiteness, cleanliness, and
fineness of fibre has been supplemented by bleached beech. In America bleached
hardwood sulphites made from birch, beech, and maple are on the market
to give much better strength and quicker beating than with bleached soda
pulp.

Silk pulp for viscose rayon staple fibre and viscose films has reached such
a large tonnage that it has become almost an industry in itself. The brands
of the older type are not very different from soft bleached sulphites made for
paper-making, except that greater care is taken to control viscosity and good
swelling characteristics in caustic solution, and to reduce resin, ash, and other
impurities. The use of alkali and other special treatments has resulted in a
higher grade of silk pulp with over 90 per cent alpha-cellulose content, less
degradation of the cellulose, better whiteness in alkali, and extremely low
impurities for conversion to stronger, brighter thread in the modem rayon
mills. This grade also involves special control of sheet size, moisture content,
basis weight, thickness, and absorbency. Although this grade has been largely
made from spruce and western hemlock sulphite pulps, there is a distinct
widening of the scope to include sulphite and sulphate pulps from pine and
hardwoods.

‘Alpha* pulps of alpha-cellulose content well above 90 per cent are
specialised in their characteristics and limited in their sources of production.
Sulphite and sulphate pulps from softwood and hardwoods are given special
treatments in addition to bleaching. In the range up to about 95 per cent

WOOD PULP

alpha-cellulose, the further removal of pentosans, oxycellulose, and hydro¬
cellulose tends to raise the whiteness, stability of colour, cleanliness, chemical
purity, permanence, tear, softness of fibre, and resistance to hydration. Soft¬
wood sulphite fibre is very suitable for high-grade bond, parchment, and other
strong papers, and the beating characteristics become closer to those of rag
stock. Hardwood fibre of exceptional softness, bulk, opacity, and brightness
is used in mixture for fine-textured papers and boards. Sulphate fibre at
moderate whiteness gives the toughest high-grade products. In this range also
are purified pulps designed for photographic paper, absorbent tissue, moulded
products, and high-grade viscose.

The scope of sulphate pulps has been greatly extended by including bleached
grades in addition to unbleached and semi-bleached. As is well known, the
general characteristics are high strength, resistance to beating, freedom from
pitch, relatively high freeness, and colour varying from dark brown to good
white. It should be remembered that not only are breaking length and burst
of sulphate pulps superior to the best that can be reached with sulphite parallels,
but also the tear and fold are outstanding. The properties of sulphate are
more standard for each grade than in the case of sulphite, because the alkali
cooking has a more specific action on the wood fibre with less hydration of
cellulose and pentosans.

Unbleached grades include kraft, fight and strong (‘L. & S.’) kraft,
easy bleaching, and aspen sulphates, according to the usual European
classifications.

Kraft pulp is the well-known, extra-strong brown fibre used in the toughest
grades of paper and board. The best brands for fine wrapping papers and
tissue must be cooked for a fairly long period from fine-fibred woods such as
northern pine or spruce to reach the stage of well-separated fibres. Fairly
long beating time must be expected with kraft pulps.

Light and strong kraft represents somewhat softer cooking to reach brighter
colour. The tear is high, but the fibre has lost some of its bursting strength.

Speciality grades made from kraft or ‘L. & S.’ kraft include pulp which
has received chemical treatment and thorough washing to reduce the electric
conductivity to a very low figure for the manufacture of condenser tissue,
and pulp which has been treated to swell the fibres for use in absorbent products
such as roofing felt.

Easy-bleaching sulphate is reached by more thorough cooking to yield
pulp which will bleach by single-stage treatment with 12 to 18 per cent bleach.
Bleached in this way, the final colour cannot be expected to equal the white¬
ness of bleached sulphite, but the high tear, good bulk, and good opacity are
very useful for soft printing papers.

MODERN PAPER-MAKING

Easy-bleaching aspen sulphate is an example of short-fibred hardwood pulp
for sale to paper mills having their own bleaching plants.

Semi-bleached grades may become more important as time goes on.
Present methods make it much easier to reach yellow colour with sulphate
than to attain the high whiteness of bleached sulphite, and very little strength
is lost.

Semi-bleached kraft represents the initial stages of chlorination and hypo¬
chlorite treatment applied to the best brands of strong kraft. This grade is
intended for the toughest papers of manilla colour as a substitute for rope and
hemp. The fibre has maximum strength, is less harsh than kraft or bleached
krafi, and lends itself to a wide range of beating.

Semi-bleached ‘L. & S.’ kraft is a softer grade. This is the kind of pulp
which may be economically made from southern pine to compete with
unbleached sulphite.

Semi-bleached soft sulphate may be a suitable name for easy-bleaching
sulphate which has been given preliminary single-stage bleaching. In this
case the pulp can be readily bleached at the paper mills to give better bulk,
opacity, and tear than is possible with easy-bleaching sulphite.

The most important advance has been made by the application of elaborate
multi-stage bleaching to sulphate pulps, with the result that good white colour
is reached without serious loss of strength properties.

Bleached kraft is the greatest achievement, and a number of well-standardised
brands are now available, mainly from the northern districts of Europe anrl
America. Colour equal to that of strong bleached sulphite is available if
maximum strength is not required, or a slighdy yellowish colour can be ob¬
tained with strength characteristics approaching those of kraft. Opacity of
bleached kraft appears to be much the same as with strong bleached
sulphite at equal freeness of fibre, but higher at equal strength of sheet. For¬
tunately, in beating time and power consumption, bleached kraft is inter¬
mediate between unbleached kraft and strong bleached sulphite. Although
the fibre can be successfully mixed with sulphite in the beater, separate beating
naturally gives better results whenever convenient. The fibre tends to give fuzz
and inferior sheet appearance with ordinary light beating, but sharp tarVb and
heavy roll improve the texture and opacity without seriously affecting the burst
and tear of the sheet. Longer beating increases transparency and toughness,
and the treatment can be continued to a very high end-point of bursting strength
without losing too much tear or freeness. Filler fibres such as bleached hard¬
wood sulphite can be mixed with bleached kraft to improve formation,
surface appearance and opacity without undue loss of strength. Experience
with bleached kraft can conveniendy be gained by using various proportions

WOOD PULP

with bleached sulphite or rag stock in present products being manufactured
at a paper or board mill. Bleached kraft by itself is ideally suited to extra¬
strong tough papers which hitherto it has not been possible to make from
wood pulps. Progress will undoubtedly also lead to the development of
specialities which have not been economic with rag or hemp.

Bleached ‘L. & S.’ kraft is a name chosen for the slightly softer grade.
At yellowish-white colour the strength should approach that of bleached
kraft. The usual aim is best possible whiteness, with appreciable decrease in
burst and fold. The fibre is somewhat finer in texture, softer and more opaque
than that of bleached kraft, making it competitive with strong bleached sulphite
for various papers and boards.

Soft bleached sulphate is the grade made from easy bleaching sulphate.
Single-stage bleaching does not produce high white colour, but the brightness
can be raised close to that of bleached sulphite by multi-stage treatment. Opacity
is very high. Softness and absorbency are also high. In addition to paper and
board competition with soft bleached sulphite, this grade may be expected
to take a share of the chemical uses after suitable purification.

Bleached aspen sulphate is the corresponding grade of short-fibred pulp.
Other hardwoods will also find a place in this grade.

Bleached soda pulp is the well-established grade in America, based on
caustic soda cooking and bleaching of hardwoods for mixing with soft bleached
sulphite in papers of the book and magazine type. The brightness is com¬
paratively low. The fibre is soft and bulky, and the pulp resists hydration to
maintain freeness, very good opacity, and low shrinkage.

Bleached soda pulp is perhaps the nearest wood pulp approach to esparto,
although the latter has superior burst, tear, opacity and fineness of texture.

A variation of the soda process is sometimes practised by mixing only a
small proportion of sodium sulphide. In this way there is an appreciable gain
in strength over the regular sock process, and the bulking properties are better
than in the case of sulphate pulp. Softwoods are sometimes cooked in this
way for bleaching purposes.

Pulp Qualities

Uniformity is the first on the list of quality requirements for all pulps,
regardless of process or grade. This refers to evenness of fibre qualities de¬
manded by the particular use for which the pulp is needed. It applies not
only to the regularity of quality from one shipment to another, but also
throughout a bale or batch. For instance, in a self-contained newsprint mill
one of the main technical problems is continuous control at.the grinders, of

MODERN PAPER-MAKING

freeness, strength, and running properties of the mechanical pulp, because
uniformity means so much on the paper machine for high speed, fewer breaks
and steady quality of newsprint.

In a mill using purchased pulp smooth operation is greatly aided by being
able to rely on the running properties of a brand. The difficulty of controlling
uniformity is a story in itself. Remembering the variations in wood, seasonal
conditions, and the many other factors in a pulp mill, the problem of ending
up with uniform pulp can be readily appreciated. Modem pulp mills have
elaborate organisation of staff and instruments towards this end, and it is a
tribute to their efficiency that pulp for sale is nowadays a remarkably uniform
product.

Cleanliness is also an item of vital importance in relation to most grades
of pulp. The very fact that paper and board meet the eye naturally brings
cleanliness to the front. The main problem of dirt is in unbleached sulphite
pulp, due to black knots softening in the acid process and spreading through
the pulp. Great precautions are taken to clean the wood as carefully as possible,
to blow the digester gently, and to remove the larger dirt particles by settling
and screening. Circulation in the digesters has helped to remove shives and
dirt. The mills are not resting content with the present methods, and there
is some hope that a centrifugal separation of dirt will prove economic. In
the case of groundwood, ordinary dirt is seldom criticised because the mechani¬
cal process has the advantage of finely grinding the hard knots and other dis¬
coloured parts of the wood, but the shives and small fibre bundles are naturally
prominent because of the very nature of the process (grinding process).
Sulphate pulps gain by the cooking liquor digesting the knots and bark specks,
leaving shives as the main item. Grit or metallic particles may find their way
into mechanical pulp from the grinders, into sulphite pulp from the digester
linings, and into pulp in general from wood, piping, and other sources. The
fact that pulp bales pick up extraneous dirt during transport and storage adds
, to the demand for extra-clean pulp sold in the open market, especially as the
paper machine screens are mainly for protection of the Fourdrinier wire.

*■ * The general demand for whiteness and brightness has led to much attention
along the lines of colour control. The brightness of unbleached sulphite and
kraft has been improved by studying the cooking conditions. Multi-stage
bleaching of chemical pulps has produced whiter products of wider range.
Furthermore, the chemical purity and stability of the bleached pulps are
higher, giving better resistance to light and heat. The colour after waxing
depends on the physical and chemical nature of the fibre as well as on the
apparent colour of the pulp. Pulp for rayon must retain good white colour
in caustic soda. An extreme case is the need for highly purified chemical pulp

WOOD PULP 69

for high white plastic products. In the field of ordinary paper and board the
colour after beating must also be considered.

Strength, breaking length, burst, tear and fold are very useful in controlling
the uniformity of cooking and bleaching. Breaking length and burst may be
said to depend mainly upon the fibre-bonding properties developed by the
process. Tear depends more on fibre length. The cooking process has an
important bearing on tear, kraft being inherendy much stronger than sulphite.
Fold, though hard to measure accurately, gives a further insight into the chemical
effects of cooking and bleaching. It is always well to remember that burst
and tear develop in opposite directions in both the cooking and beating pro¬
cesses, which means that attention should he paid to the overall strength of
a pulp.

Beating does not concern mechanical pulps to any extent, but the grinding
process is really a form of beating to develop hydration and fibrillation of the
fibres. Unbleached sulphite pulps can be controlled by the cooking process
within limits to give quick or slow beating as required. Sulphate cooking is
flexible in this respect, and in general the pulp requires more beating time and
power. The bleaching operation can be considerably varied in relation to
beating properties, the use of caustic soda in the second stage being a modem
example of improving the resistance to hydration.

Fibre size, opacity, porosity, absorbency, oil penetration, blister, bulk and
other characteristics can be controlled within limits both in pulp mill and
paper milL

Moisture content is a question which,, does not arise in self-contained mills
using slush pulp. In the case of pulps for shipment the problem is largely an
economic one. Mechanical pulp does not lend itself to drying, except the free
grades for board-making. Unbleached sulphite and kraft pulps shipped in
die moist condition break up more easily and beat more quickly to somewhat
higher burst, but suffer to some extent from danger of picking up dirt and of
developing infection. Dry pulp is an advantage for long storage, better
opacity, and more uniform control. Bleached pulps, except for greaseproof
and a few other uses, are shipped in the dry condition to ensure best cleanliness
and brightness.

Ash content tends to be high in sulphate pulps, but is not of particular
significance. The ash in sulphite is largely due to calcium compounds pre¬
cipitated during cooking or bleaching, and when necessary can be reduced
by add treatment, as is practised with bleached grades for chemical uses. Pitch
content has been given thorough study in the pulp mills. Mechanical pulps
seldom give running trouble, because the normal character of the wood resin
has not been altered by the grinding process. Sulphate and soda pulps are

MODERN PAPER-MAKING

practically free from resins by reason of the alkaline cooking. Unbleached
sulphite is the chief problem, because the acid cooking makes the pitch more
sticky. Great precautions are taken to avoid harmful character of pitch and
to lower the percentage in the pulp. The bleaching process greatly reduces
the pitch content. For chemical uses the bleached sulphite is treated with
alkali and sometimes with saponifying agents to remove practically all
the resins.

Small quantities of foreign matter have sometimes to be controlled for
special uses. Iron and copper, either in specks or in diffused form,-must be
kept to low figures in bleached pulps for the manufacture of photographic
paper, genuine vegetable parchment, and other special grades. Chemical
pulp mills are using more and more glazed tile, stainless steel, rubber, and other
resistant surfaces to avoid impurities. Sulphur residues must be reduced below
specified figures in sulphite and sulphate pulps for anti-tarnish paper and similar
products, but groundwood is naturally pure in this respect.

The reddening of unbleached sulphite is due to oxidation of colouring
bodies, and the tendency towards reddening may be judged by testing with
hydrogen peroxide. Reddening is usually greatest -with strong sulphites and
least with easy bleaching grades, but the wood species and the pulping conditions
also have a bearing. Reducing agents, such as sodium thiosulphate, have a
protective action.

Reduction of Esparto Grass to Half Stuff

The bales being opened out, the grass is put through a willow or duster
similar to a threshing machine, which breaks up the bunches and loosens and
separates the sand, dust, etc., from the blades. From the duster a conveyor
carries it to the boiler. The boilers are usually of the stationary vomiting
type. A revolving boiler causes too much loss of fibre through friction, and
packs the grass into hard heaps very difficult to deal with. A usual size holds
about 2 \ or 5 tons of dry grass. Boiling is conducted with about 14 to 15 per
cent caustic soda, from 3 to 4 hours, with 40 to 60 lb. steam pressure, depend¬
ing upon the quality of the grass and the capacity of the boiling plant to keep
up with the demands of the tnill.

The caustic liquor is run in with the grass, and some steam turned on in
order to soften it and get a heavier charge into the boiler. On the completion
of the boil, the steam is blown off and the used liquor is run to the recovery
plant. Further washes with hot water to remove the last of the liquor are
necessary, and these may also be run to the recovery plant or liquor tanks.
The grass is then dug out and filled into trucks, or it may be more conveniently

STRAW 71

cut out by a high-pressure water jet and washed, blown or pumped to the
washers or concentrator.

Washing and bleaching follow the same lines as for rag, but the potchers
have no plates, and the blades are blunt and waved, so as to prevent any cutting
or drastic beating taking place. Even then a very great loss of fibre takes
place in washing and bleaching through the washing drums; about 7 per cent
bleach is used and heat is permissible up to 90 1 F. Very dull-coloured
stuff may with care be heated up to ioo° F., but the risk of destroying
the fibre is very great, and only highly experienced men may be allowed to
take it.

Spanish esparto requires less bleach to bring up the colour. From the
potchers, after the bleach has been washed out and the last traces have been
killed with anti-chlor, the pulp is emptied into the presse-pate chests. The
presse-pate is the wet end of a Fourdrinier machine. There are long and deep
sand traps through and along which the grass flows with the water, loosening
sand, metal or any other heavy substance that may sink and be caught by the
felts on the bottom. Sufficient strainers to take the pulp through without
forcing are provided. These keep back all knots and thick untreated fibres
and lumps. The wire, of rather coarse mesh, then receives the pulp, and the
water drains out, assisted by the suction boxes. After passing the couch rolls,
the water is still further extracted by a felt and press rolls, and the pulp falls
into boxes ready for the beaters, or may be conveyed to the beater chest. The
yield of fibre varies according to the country of origin of the grass and other
factors, but it may be taken to be from 38 per cent for Oran grass to 45 per
cent for best Spanish. The amount of bleach required is usually between
7 and 10 per cent calculated on the weight of the raw grass.

Straw

Up to the present time, in Great Britain, at least, it has been the custom
to treat straw in much the same way as esparto—namely, to boil it in stationary
boilers with caustic soda, then wash in tanks of potchers, bleach and run the
fibres over a presse-pate.

Boiling is carried out at from 20 to 80 lb. pressure per square inch, with
from 10 to 20 per cent caustic soda, according to whether yield or colour is
more important. When the boiling process is drastic, the yield is small and
the pulp is capable of being bleached very white, but its strength is greatly
reduced, and it produces a ‘wet* condition in the furnish owing to the formation
of oxycellulose.

MODERN PAPER-MAKING

The straw may be cut up in a chaff-cutter or packed into the boiler in bundles.
It is best, however, to cut it up, as dirt is then much more easily loosened
and dusted out. It is unnecessary to remove the knots from the straw stems
before boiling, but in order to free it from com and hard particles of grit, etc.,
it is cut into short lenghts of i to 2 inches and blown through a trunk into a
hollow gauze chamber. The heavier particles remain behind and fall through
the gauze, while the lighter straw passes on and is filled into the digester. After
the digester is full, or while it is being filled, the straw is soaked with water or
with caustic solution in order to pack it down. The digester is then filled up
again with more straw, and the boiling commenced. The pressures employed
vary from 20 to 80 lb. per square inch, and the caustic soda from 10 to 20 per
cent. The resulting stuff is a pulpy mass which can be run through pipes to
draining tanks, whence the lye is drained away for recovery, and fresh water
is run on to the pulp to complete the washing. After draining, the pulp is dug
out, bleached in potchers, run off on a presse-pate, and is ready for furnishing
to the heater.

Another method, which, however, is very wasteful of small fibres, is to
wash the boiled straw in ordinary breakers with dram washers. The wire
cloth covering of the drums in this case must be of very fine mesh in order to
retain the smaller fibres and cells.

We are indebted to Mr. B. A. Poulie Wilkins, Managing Director of the
Stroostoffabriek ‘Phoenix’, Veendam, Holland, for the following particulars
of the treatment of straw for making fine writing papers:

‘The straw is cut into short pieces about an inch in length, and is then
boiled in rotary boilers with sulphate liquor of about the same constitu¬
tion as the liquor used for boiling kraft sulphate pulp. After cooling,
the contents are blown into washing tanks for the separation of the stuff
from the black liquor. The stuff is next run through a refiner into the
bleaching tanks, where it is treated with about 1 per cent of chlorine. It
is then run off on a pulp-drying machine and is ready for use.

‘The black liquor from the washing tanks goes to the soda recovery
department, first to the quadruple-effect evaporators, where it reaches a
strength of 25 0 to 32 0 Baume; the rotary furnace fully dries the black
mass, and this material is burnt in the smelting furnace to Na*CO* and the
Na.SC>4 is reduced to Na»S; the caustidsing plant does the rest.

‘The composition of the straw itself is of vital importance, and also
its state of cleanliness. In this country [Holland], for instance, the examina¬
tion of stalks of rye straw has revealed that those grown near the North
Sea—that is, on the land which contains a very high percentage of silicates

STRAW

—contain as much as 5 per cent by weight of silicate. Straw grown on
average soil contains only about 0.5 per cent.

‘From this it wall be realised that raw materials varying so much in
composition require different treatment. Great difficulty is experienced
in the soda recovery department when dealing with the waste liquors from
straw containing a high percentage of silicates, on account of the formation
of sodium silicate on the melting furnace.’

Excellent writing papers may be made from straw pulp manufactured by
the above method, in the furnish of which as much as 80 per cent of straw is
included.

At present there is a tendency to move out of the old rut in the preparation
of raw materials for making white papers, and to carry out the boiling and
bleaching on more scientific lines, and to take advantage of the advances in
the knowledge now available so far as the chemistry of cellulose is concerned.
Two processes have been largely developed in recent years, mainly for the pro¬
duction of bleached pulp from raw materials such as straw, hemp, flax, and other
plants and grasses. The first of these was developed and put on to a commercial
basis by De Vains, who originally applied his methods to producing satisfactory
pulp from straw about twenty-five years ago. This process has been further
developed, and now Professor Pomilio has also developed a process on rather
similar lines, which seems to have met with some success in various parts of the
world. Both these processes rely to a great extent on chlorine gas acting upon
the moist pulp and removing the lignin. Satisfactory results have been obtained
by both processes, but there are a certain number of difficulties to be contended
with in each case.

CHAPTER VI

BEATING

Beaters - Beating - Refining

The beater may perform several operations besides its chief function of actually
fibrillating the stuff.

First, it may have to break up sheets of wood pulp or lumps of rag stuff
This is done by feeding in or furnishing the sheets or lumps of stuff gradually
after the beater is about half or three-quarters full of water.

The sheets of wood pulp should be wetted first, or pushed under water
before they reach the roll, in order that they may be as soft as possible. In
the same way the lumps of rag half stuff, which are usually damp, should be
tom up small by hand as they are being thrown in.

During this period of .furnishing the roll is raised up well away from the
plate, to prevent it jumping up when any hard lump of stuff comes between
it and the plate.

In a surprisingly short time the sheets of wood or lumps of rag are reduced
to a fairly uniform pulpy mass. In the case of the rag stuff, the first treatment
depends to a great extent on how far the rags and threads have already been
reduced in the breaker. Usually, however, a great many twisted cotton threads
are still present, and these have to be drawn out by the roll.

As soon as this is accomplished the beating proper begins, and the roll
must be let down to a fairly hard rub. Just how much pressure can safely be
brought to bear on the stock, depends on the strength of it when it is furnished,
and this must be left to the skill and experience of the beaterman. When the
beating has been carried far enough, and it is found on examination that the
fibres on the whole are too long, the roll must be let down heavily on to
the plate for a short time to cut some of the longer fibres to a length suitable
for the paper which is to be made.

Finally, the stuff must be cleared—that is, the little clumps and knots of
fibres must all be separated out—otherwise hard lumps may get through, and
may either clog up the strainers or, if they are small enough, find their way
into the finished sheet.

The treatment of wood pulp is much the same as rags, except that there
are no threads to be drawn out; nothing but small clumps of fibres have to

BEATERS

be separated out before the actual beating begins. There is also much less
cutting or reduction of the length of individual fibres, as they are much shorter
than rag fibres to begin with.

The final clearing of knots and the reduction of the longer fibres to a uni¬
form length are often performed by a refiner or perfecting engine. This is
invariably the case in the beating of newsprint and cheap printings, and in
most cases where the object is to get the beaten stock as ‘free working’ as
possible.

Beaters

There are a great many different designs of beaters in general use, but these
may be divided, broadly, into two classes—viz. those which depend for the

circulation of the stuff on the beater roll itself, and those which have a separate
circulating apparatus, either pump, screw or propeller.

The first named are the most universally employed, and in fact they are
entirely satisfactory for making all kinds of paper. The second group are
used for those fibres which are not liable to form strings, and they find favour
with some paper-makers who use a large proportion of esparto grass.

The first and foremost of all beaters is undoubtedly the hollander (Fig. 16),
which is, so far as is known, the first advance which was made on the ‘stamr
pers’, and it was, no doubt, originally invented when the necessity arose for

BEATERS

greater output. This engine enabled the beating to be carried on continuously,
on a fairly large body of stuff, in quite a small area; whereas only a few rags
could be pounded at one time in the stamper trough, which was a very slow
business.

The hollander consists of a large oval trough with a partition, called the
midfeather, dividing it for some distance down the middle, but stopping short
a few feet from each end. The plan (Fig. 16) shows clearly the shape of the
trough and the partition.

The trough may be of cast iron, wood or concrete, and may be lined,
in the case of cast-iron and concrete types, with cement, glazed tiles, lead or

[Bertrams Ltd.

Fig. 19.—Basalt Lava Beater Roil with Cast-Iron Spider and Stone Segments

copper. The construction of the trough is such as will permit and encourage
the quick and regular circulation of the stock, and prevent the lodgment of
any stuff, which might thus escape proper and thorough treatment, and which,
getting emptied down into the chest with the water used to wash out the
beater, would spoil the paper or seriously clog the strainers. The presence
of sharp comers, hollows or projections in the trough is very undesirable.

The beater roll (Figs. 17,18 and 19) is placed on one side of the midfeather,
about midway between the ends, and consists of a cast-iron or iron and stone
cylinder, through which is fixed a steel shaft, which serves to support the
roll and also to connect it, by means of a suitable pulley, to the main driving
shaft.

A modem development is a roll driven by an internal electric motor which

78 MODERN PAPER-MAKING

does away with indirect drive and saves much room. This arrangement has
another desirable feature in that it eliminates the driving belt which may upset
the alignment of roll and bed-plate.

The roll can be raised or lowered on to the bed-plate at will by means of
a lifting gear attached to the bearings, and operated by a wheel or handle
through a fine adjustment screw.

The iron roll is cast with alternate longitudinal projections and spaces, or
grooves, around its circumference. The grooves serve as a housing for the
flybars, and are about 4 inches wide. There is also a channel left round each
end of the roll into which fits the iron ring used to hold the bars in place.

Fig. 20.—Front Elevation of Bed-Plate and Section of Roll, showing Roll Bars arranged in Clumps of

Four and Bevelled

The flybars may be of steel, bronze, or other alloy, and they are usually
arranged in clumps of two, three, or four, although there is no reason why
they should not be equally spaced around the roll. When arranged in clumps,
the bars are usually about 1 inch apart, and the clumps are about 4 inches apart.
The idea of leaving a space between the clumps is to make the first bar of the
clump act as a paddle to pick up stuff and carry it down into the nip between
the plate and the roll (Fig. 20). No doubt this arrangement of the bars in¬
creases the speed of the circulation, but it does not necessarily follow that
more fibres are treated in proportion to the increase of speed. In fact, some
consideration will show that die increase in circulating speed means that so
many more fibres pass untouched by the bars and plates. The bars may be
sharp at the edges, and bevelled down to ^ inch for beating free stuff, such

BEATERS

as blottings, filter-papers and thick papers required to bulk well, or they may
be broad and blunt (f inch), as for strong rag papers, thin banks, etc. The
basalt lava stone roll (Fig. 19) has no bars and does not cut the fibres. It is used
chiefly on wood-pulp furnishes for making very \vet’ and highly fibrillated
stock for greaseproof and kraft papers.

Immediately below the roll, in the floor of the beater trough, is a sunken
box, or ‘den’, into which fits the bed-plate. This consists of a heavy baulk
of timber or a cast iron tray into which is fitted a set of metal bars or knives,
similar to the flybars of the roll. This bed-plate (Fig. 21) is fixed, and the knives
in it are so arranged that the flybars. meet them at a slight angle, in order that
their action on the fibres may be a shearing or tearing process, and not a direct
cut or chop. This is effected by placing the knives diagonally across the box, or,
more frequently, by having them bent into an elbow shape as shown in the
illustration. This latter arrangement of the bars, besides giving a shearing action,
also performs the important function of taking some of the fibres from the inside
to the outside of the trough and so mixing them continuously, and thus pre¬
venting those on the inside from continually circulating round a much smaller
area than those on the outside. It should be noted, in this connection, however,
that the fact that the stuff near the midfeather makes a complete circulation
more frequently than the stuff round the outside edge of the trough has the
great advantage that all the fibres are not reduced to approximately the same
length, and thus a much better and closer felted paper can be made.

Just beyond the bed-plate is the ‘backfall’, which is a continuation of the
trough of the beater, carried up in the form of the arc of a circle, to correspond
with the circumference of the roll, and close to it.

The backfall should be about 4* to 1 inch away from the roll when it is
‘down’, and carried well up to about 3 inches above the centre of the shaft,
tapering away from the roll at the top until it is about 2\ or 3 inches away,
thus leaving no pocket of dead stuff at the top. These dimensions are clearly
shown in the accompanying illustration.

These measurements give the best circulation and fibrillation of high-grade
wood pulp and rag stock; if the distance between the roll and the top of the
backfall is great, there will be a heavy pocket of stuff lying dead and impeding
the flow of stuff coming away from the roll. It is important that the backfall,
should be dose to the roll, in order that there may be as much friction and
rubbings of the stuff as possible during its passage from the bed-plate to the
top of the backfall, where it is thrown out into the trough again.

The fact that the bed-plate bars wear down, however, makes it impossible
to have the roll always at the same distance from the backfall, unless the roll
is stationary and the bed-plates are hydraulic, so that the distance must be so

8 o

MODERN PAPER-MAKING

arranged that when the bed-plate is worn right down the roll will be about
| inch away from the backfall.

Another point of importance in the design of the trough is the amount
of rise from the lowest level at the emptying valve to the plate. Some beaters
are quite flat and have no rise at all, and in this case the roll is deeply submerged

[Messrs. Crookes , Roberts and Co .
Fig. 2 i.—V arious Shapes of Beater Bed-Plates

in the stuff and whips it continuously, without taking any more stuff through
between the plate and the roll bars.

This whipping, while doubdess aiding the fibrillation of the stuff, consumes
a great deal of power, and has the disadvantage of heating the stuff too much
for all the fibrillation it accomplishes.

Our experience with beaters of this type has convinced us that their circu¬
lation is very poor, and that the continual whipping of the stuff dulls the colour
and spoils the purity of the paper.

We have described our ideas of a hollander beater in some detail, but

BEATERS

experience shows that if the maximum efficiency is to be obtained, great care
must be paid to details of design and dimensions.

For a hollander holding 450 lb. of dry stuff and intended for general use,
such as the beating of wood pulp, wood and ‘broke’, wood and rag and all
rag furnishes, the weight of the roll should not exceed 3 tons and the circum¬
ferential speed of the roll should be about 2000 feet per minute.

The Umpherston beater (Fig. 22) differs from the hollander in that it is
placed ‘on end’ to save space; in other words, the stuff travels down from

In this type of engine the stuff circulates in a trough beneath the bed-plate

the roll and underneath it, and then up and back again, instead of round the
trough The midfeather is placed under the bed-plate and the roll is well
out of the stuff.

We are of opinion that there is little to choose between, a well-designed
hollander and an Umpherston, but the latter has three distinct advantages—
namely, its saving of space, its easier and quicker emptying facilities, and its
freedom from ‘lodgers’; it is also much more shut in —i.e. the stuff is not nearly
so exposed, to the dust and dirt which are continually falling about in a beater
room, as is the case with the hollander. Owing to its being so much enclosed,
when beating hard fibres, the stock heats up very quickly.

The Umpherston is a compact, well-designed and thoroughly efficient
beater.

MODERN PAPER-MAKING

The Taylor beater (Fig. 23) is used principally in mills whose furnishes
contain a large proportion of esparto.

In beating such stock as esparto and wood it is possible to dispense with
those factors which are an absolute necessity for beating strong rag stock.
The ultimate fibres of wood and esparto are short, and if the papers made from
them do not require to be very strong, their treatment in the beater is sharp

[Masson, Scott and Co, Ltd,

Fig. 23 ,—A Battery of Tayxor Beaters, 'with a Range of Bleaching
Towers in the Background •

and quick, and must be as uniform as possible in order to produce a very close
and evenly made sheet.

The Taylor beater fulfils these requirements admirably, and is being success¬
fully operated in many mills making esparto papers. The beater is entirely
different in construction and design from both the hollander and Umpherston
types, as will be seen from the illustration.

The stuff is fed into the vat and drops down to the bottom of the enclosed
trough, where it is collected by a centrifugal pump, and forced up again through
a pipe, to be discharged in front of the roll.

This method of -circulation relieves the roll of the necessity of performing

BEATERS

the whole of the circulating or propelling of the stuff, and therefore the roll
may contain many more bars, and these may be closely and evenly spaced.
It will be evident that this process
ensures quick and uniform beating
of the stock and saves a large
amount of time. The roll is also
much smaller and lighter than is
necessary with the hollander.

This type of beater is not suit¬
able for the treatment of long-fibred
stock, such as rags, as the circulator
will not deal with such material,
and in any case the treatment of
rags with such an arrangement of
beater roll would not be satis¬
factory.

The Taylor beater does not
necessarily depend on gravity for
discharging the stuff to the chests,
as, by the arrangement of cocks and
emptying pipe, the stuff can be
pumped by the circulator to the
machine chests, so that the beater
may be on the same floor level as
the machine, if necessary.

Very litde floor space is required
for this beater, and, being enclosed,
the stuff is not exposed to dust and
dirt from the beater room. The
roll and plate are fixed to the floor
of the beater room, independently
of the pan, in a square casing.

Another beater of a slightly
modified design, but working on
the same principle, is the Tower
beater (Fig. 24), made by Masson,

Scott and Co. Ltd. It differs from
the Taylor beater in that it occupies
less floor space in the beater room, and, being supported usually from the
ground floor, the beater room floor can be of much fighter construction.

[Masson, Scott and Co. Ltd.
Fig, 24*—Elevation and Plan of the Tower
Beater

MODERN PAPER-MAKING

The stuff is discharged from the roll down on to a conical hood fixed at
the top and inside the tower. This spreads out the pulp and mixes it con¬
tinuously during the whole of the beating. The bottom of the tower tapers
down to a bend, at the end of which is fixed the circulating pump, which
throws the stuff up a pipe and discharges it again in front of the roll.

The beating is performed in the same way as in the Taylor beater, and the
same remarks apply as to the roll and emptying of the stuff.

The pump circulator of the Taylor and Tower beaters is a great help with
short-fibred furnishes such as esparto, since it materially helps ‘wetting’,
and in fact the roll can he lifted quite clear and the circulation by the pump
will induce quite a large degree of wetness. Furthermore, the beaters may

[Messrs. Bertrams Ltd.

Fig. 25.—Soennes Hollander Beater, showing Three Bed-Plates placed up the Backfall, also Equally Spaced

Bars on Roll, and Very High Backfall

The path of travel of the stuff is dearly shown, also the unusual shape of the wooden cover. Note the baffle plate in
front of the roll, to prevent the roll from splashing in the stuff before it reaches the plate

be filled with stuff of comparatively high consistency, and this is a great help
in beating esparto furnishes to a given length and wetness. Unless a Tower
beater is filled to a point below the conical hood ‘lodgers’ will collect above
and cause trouble.

The Saennes patent beating engine, evolved after careful thought and
trial by Samuel Milne, is a great advance in beater design, and is giving good
results on a wide variety of furnishes. Of the hollander type, it has several
modifications of the usual standard models, and some innovations (see Figs.
25 and 26).

The tough itself is extremely well designed, in order to promote rapid and
even -circulation, and it is not the usual ‘2 semicircles joined by 2 sides’, in
which a great deal of stuff either lodges permanently until moved on by the

BEATERS

potching stick, or only moves very slowly. The shape of the trough is shown
in Fig. 16, and paper-makers will see at once that the ‘dead spots’ in their beaters,
which they have often had to fill up with cement or concrete, have been entirely
eliminated.

The height of the trough is arranged to coincide with the general height
of stuff as it travels round the beater, and it is low in front of the roll and high
behind the backfall.

The roll itself is very heavy (9 to 10 tons in a 1000-lb. beater), and the roll
bars are equally spaced and not set in clumps. The reason for the heavy roll
is to give pressure on the bed-plate, and to prevent jumping and vibration
when lumps of stuff pass through, while the fine adjustment provided for
lowering the roll prevents all risk of the roll being too suddenly or heavily let
down on to the bed-plate. A heavy roll is better for beating strong stuff,

[Bertrams Ltd.

Fig. 26.—Sciennes Patent Beating Engine, showing Automatic Control Gear

which has to be well fibrillated, than a light roll, for it is steady and can be
kept at the correct distance from the bed-plate all the time.

As it is impossible for a beaterman, who has a battery of beaters to super¬
vise, to operate them all in exactly the same way each time, an automatic
operating gear has been fitted.

The front main lever is operated by compound levers, and the weight is
adjusted by hand wheel and screw, so that any desired pressure may be applied.
The pressure may be maintained constant from start to finish if need be, but
can be easily adjusted to suit requirements.

The bars, as mentioned above, are equally spaced, and not clumped, as has
been the usual practice for many years. The reason for this is obvious, for,
as every beaterman knows, the first bar of the clump carried most of the stuff
and the following bars not enough. Well-separated single bars, especially for
long stuff, are the best.

MODERN PAPER-MAKING

Eighty-eight bars are fitted in this beater roll, which is 60 inches in diameter,
and this gives about 2-inch pitch. As a general rule, a bar with a wide edge
would be most suitable for beating strong stock which had to be well fibrillated,
and a narrower bar for short, free stuff. The wider the bar the greater will
be the pressure and cru shin g action exerted upon the fibres, but a thick bar can
be made to cut up stuff quickly enough, provided it is lowered down quickly
and kept hard on for a short time.

The bed-plate is very wide, almost one-quarter of the circumference of
the roll (in fact, there are two or three bed-plates placed close together), and
this, together with the weight of the roll and the well-designed trough, is
responsible for the efficiency and great economy of power achieved with the
beater.

The chief reason for making the bed-plate so wide is that it is now realised
that a large amount of the power consumed by a beater is used in circulating
the stuff. In other words, it is wasted so far as actual beating is concerned.

As the beating is done only during the quick passage of the stuff between
the bars of the bed-plate and the roll, the way to increase the amount of beating
done in a given time is to increase the size of the beating area— i.e. the total
area of bars in the bed-plate and the area of bars in the roll.

The position of the bed-plate is also different, in that it starts almost exactly
under the centre of the roll and takes the place of the usual backfall up to a
point. The short backfall takes up an angle of 15 0 , and is arranged to ensure
the pulp being thrown out at the proper place. It will be readily understood
that, with this design, the stuff is thrown clear immediately it leaves the last
bar of the bed-plate, and there is no heavy pocket of stuff lying between the
backfall and the roll, impeding the passage of the stuff back into the trough.

With the usual type of bed-plate and backfill, stuff is flowing into the
spaces between the bars all the way up the backfill, and being thrown out
again by centrifugal force. This not only impedes the forward flow, but also
adds to the power required to drive the roll, and instead of the stuff being
quickly got rid of once it has received its treatment, as in the present beater,
it is slowly pushed up in rolls to fall over the top of the backfill and into the

In order to obviate the objectionable splashing of the roll in a deep pond
of stuff immediately in front of the bed-plate, a baffle board may be carried
right down to within about 12 inches of the bed-plate, and the floor of the
trough is shaped up to the bed-plate, so that the stuff is forced through this
narrow space in sufficient quantity to allow of a fibrage being taken on by
each bar of the roll. A smaller opening than 12 inches would be sufficient,
but lumps of stuff would be liable to choke it when furnishing.

BEATING

Modem beaters are designed to circulate in the quickest possible time, and
at the same time to possess a large bed-plate area in order that a greater amount
of work may be done during one circulation of the stuff. This is done by
having a very wide bed-plate, or more often by having a series of bed-plates.
There is also a tendency at the present time to use lighter rolls, as it is claimed,
apparently with some authority, that the work can be just as well done with
lighter rolls and less power.

Beating

Among all the various processes which are used in the manufacture of
paper, none has aroused so much- controversy and discussion as beating.

‘What takes place in the beater?’ is still a question that has not yet been
answered to the satisfaction of the chemist, the engineer, and last, but not
least, the paper-maker.

■ We propose, however, as paper-makers, to offer an explanation as the result
of our experience, aided by the results of the investigations of those who have
of late years devoted so much time and careful thought to the subject.

At the outset we propose to divide the subject into two phases, ‘free’ beating
and ‘wet’ beating.

By ‘free’ beating we define those processes where such fibres as mechanic a
wood, esparto, straw, etc.—very short and poor in themselves—require no
more than to be separated from clumps or clusters, and are sent in almost, if
not quite, their original forms to the stuff chest.

The term ‘free’ we regard as denoting the result of this elementary ‘beating.’
The fibres, when passing over the wet end of the machine, part from the water,
in which they float, easily and freely.

The power required for treatment can be calculated,- and special engines, such
as the refining engine, can be used to achieve successful and satisfactory results.

The action of these special engines is not, in the true sense of the word,
‘beating’, although there is no doubt that some actual beating can, and does,
take place when the fibre is of such a form and structure as can stand it This
class of beating suffices for newsprint and other printing papers, and also for
all those papers made from esparto with a small percentage of chemical wood.
It is when we come to deal with papers of a better class, such as writings, banks,
ledgers, cartridges, tissues, and ‘Manillas’, and, in fret, most papers that require
to be water-marked, or to have strength, transparency, or any other special
feature, that the second phase of beating becomes of paramount importance.
Then, in various degrees, the stuff must be what has been called by the older
paper-makers ‘beaten wet’. We by no means dismiss the first class of beating

88 MODERN PAPER-MAKING

-namely, what we call ‘free’-as of no account or unworthy of investiga¬
tion, but will confine ourselves to the second class, as being what is admitted
by all concerned to be the representative process for all ‘beating’.

When the first prehistoric member of the Paper-makers’ Association started
to make paper he found that one part of the process entailed a great deal of
heavy work, and no doubt delegated the pounding or beating of the fibres to
his sturdiest employe. Up to the present day, to produce a strong paper from
‘rags’—we will assume this to be a representative of the whole class—the

inspection port-hole

fulcrum point of
bedplate carrier seam

COMPRESSED AIR CYLINDER,
ALTERNATIVELY PRESSURE
BY LEVERS AND WEIGHTS.

RAISING AND HOLDING QEAR,
WITH MICROMETER REGISTERING.
GAUGE INDICATING SPACE
BETWEEN ROLL AND BEDPLATE

TROUGH WITH
STREAMLINE CURVES
TO ENSURE UNIFORM
TREATMENT OF STOCK

ABSENCE OF
STOCK COLLECTION
IN ENCLOSURE AND
THUS NO BRAKING EFFECT. GEARS.

Fig. 27.

ft’OLL CARRIED IN
FIXED SEARINGS.
PERMITTING, IF SO
DESIRED, THE DIRECT
CONNECTION OF MOTOR
THROUGH REDUCTION

ROLL REVOLVES IN
OPPOSITE DIRECTION^
TO FLOW OF STOCK,’
EAdUTATIMG THE
FILLING OF SPACES
BETWEEN BARS.

MINIMUM BAFFLE AREA
SUFFICIENT ONLY FOR
filling SPACES
BETWEEN BARS.

OUTLET ’VALVE

[Bentley and Jackson

greatest power is consumed by the heating process. To reduce this great con¬
sumption of power, to ‘beat’ the rags to produce what we require, with the
minimum expense for fuel, is the ultimate object of all investigators of the
process.

Before we can do this, we must find out what takes place in the beater.
We can do this only by examining results, and formulating a theory which
will agree with these results. Now it is agreed that if two beaters furnished
with identical quality of stuff are run off at the machine, and one is beaten
‘wet’ and the other ‘free’, the one that is called ‘wet beaten invariably pro¬
duces the strongest paper. This brings us at once to the point where we must
define what we mean by ‘wet beaten’ stuff. In a word, it is stuff which parts
with its water very slowly. It will go from the breast to the suction boxes
without losing much of the water in which it is suspended.

BEATING

When passing over the suction boxes a high vacuum is required to
withdraw sufficient water to allow the web to be couched without being
crushed. This is what a machineman will understand by ‘wet’ stuff, and
for practical purposes the word will express the idea to most paper-mill
men. However, for more scientific men the w r ord did not correctly define

the condition, and they renamed it
‘hydrated’ stuff, a word which really
means ‘combined with water’ in a
chemical sense.

The question then arose as to
whether this so-called combination of
stuff and water is caused by the
mechanical action of the beating
engine or by some obscure chemical
process.

The theory of ‘fibrage’ pro¬
nounced by Dr. Sigurd Smith was
hailed as a great discovery by the
paper-making world. Without in any
way wishing to detract from the value
of this investigator’s patient labours,
we are of the opinion that he leaves
us, for any real explanation of the
subject, just where we were before.
He has not shown us how to beat stuff
‘wet’, or hydrated, by using less power.

He does indeed indicate how power
and time may be saved by using two
plates, and causing one circulation of
the stuff in the engine to give results

A BELT OR TCX ROPES

*cr from" main unit or

COUPLED DIRECT
THROUGH REDUCTION
GEARS TO MOTOR

BELT OR TEX ROPES THOM
OVERHEAD MOTOR.

hitherto ob tain ed by two circulations, pig. 28 .—plan of thorsen-hery beates

but the fact remains that the actual

power that is necessary to ‘beat’ remains the same. He gives us no explana¬
tion of beating which will enable us to get ‘wet’ or ‘hydrated’ stuff by any
other means than the beating engine.

As for the ‘chemical’ or ‘physical’ question, we should think that, after
the published results of the researches by James Strachan, no one will seriously
claim that chemical combination of stuff and water can take place, except in
an extremely limited degree.

This being so, we venture to assert that the term ‘hydrated’ stuff is

MODERN PAPER-MAKING

misleading and erroneous. It has been presumed that stuff must be wet or
hydrated before it is in that condition which makes the strongest paper.

Mr. Strachan, in our opinion, conclusively proves that ‘hydration* is
merely the sign that the stuff has attained that condition, and our personal experi¬
ence in beating entirely coincides with his proof. He shows that when the
fibres are subdivided into fibrillaz and partly crashed into very fine particles,
.more water adheres to their surfaces, or that the mixture of stuff and water
has become more intimate; each minute particle of stuff has its superficial area
increased by subdivision, and that additional surface area is covered by a film of
water. Therefore, the fact that extra water has been attracted to the stuff is
not the reason why the paper will be stronger, for the strength is caused by
the fibres being fibrillated’, and this, we think, is the proper word to describe
the condition.

It can certainly never be asserted that water adds strength to fibres; therefore
it must be that they gain strength by being fibrillated.

Now let us describe what does actually take place in the beater from this
standpoint. We will presume that we have got a hollander furnished with
linen fibres. This stuff has been boiled and gas-bleached to remove all sbive.

We may presume that in these processes the fibres have been thoroughly
saturated with water. Indeed, it is inconceivable that thorough saturation has
not taken-place. Every pore, canal and surface of each individual fibre has
its full quota of water; yet it cannot be said to be hydrated in the true meaning
of the word.

To return to the beater. We know that if we simply clear the fibres of
knots, etc., and run them over the wire, the sheet will look raw and cloudy,
and the fibres will be too cumbrous to felt with each other, and may be easily
pulled apart. The dandy roll will be unable to make a proper impression on
the sheet. Therefore we have to bead the linen fibres—and ‘linen takes a
lot of hammering, as every beaterman knows—in other words, we must
have the fibres well fibrillated. If our beater bars are too sharp we have great
difficulty in fibrillating the fibres; instead, we may cut them and have free
stuff, which is not at all what we set out to obtain. But if our tarkfe is dull—
i.e. the plate is well worn and . the bars are blunt—we can put our roll down
on the plate. Then, whether through fibrage on the bars, or the stuff being .
drawn through by the vacuum of the beater-roll spaces, the process of ‘fibril-
ktion commences. As every beater bar passes the plate, so many fibres will be
struck and bruised between the flattened surfaces of the bars and plate.

If a fibre is struck longitudinally, it may be divided into several fibrillae; if
across, it may still be fibrillated where the blow falls, thus exposing more surfaces
to the water in the beater. But it is bound to be the case that many fibres

BEATING

will be so heavily struck that they will be partly fibrillated and partly bruised;
the bruised portion will give up some of its particles to float in the general
mass, other particles remaining attached to the fibrillae. If the beater is run
long enough, all the fibrillae will in time be crushed into these fine particles
and become quite useless for paper-making. Therefore, our object is to stop
the action when we have most fibrillae and a good proportion of these particles
amongst them. Our engine of stuff will be fully fibrillated. These fibrillae
and many fibres partly flattened, and some cut through with fibrillated ends,
are obviously what will interlace to, make a tenacious sheet, and the finer
particles will setde into the minutest spaces between the larger fibres and still
further entwine them together.

By this latter action we lose
bulk but gain strength, solidity-
shown by hardness of rattle—and
transparency. Now in the making
of our fibrillated stock into paper
our greatest difficulty lies in
getting rid of the extra water
carried by the stuff. Some is
drained out by the sucking action
of the tube rolls of the wire, some
is drawn out by the suction boxes
and suction couch. The pressure
of the press and couch rolls
accounts for a great deal. But all
the extra surfaces of the fibrillated
fibres retain some surface water, and part with it only by evaporation on the
hot drying cylinders.

It simply amounts to this: we have to dry a much greater surface area
when the stock is highly fibrillated than when the stuff is free beaten.

Again, it is a matter of great difficulty to run heavy substances, say 72 lb.
Imperial, when using a rag stock highly fibrillated, to produce a strong paper.
The maximum strength obtainable from the stock is limited to the capacity
of the machine to extract this unwanted water bn the wire before the couch
nip— i.e. the stuff must, in most cases, be let down to the chest before it has
been beaten long enough to get all the good out of its fibrillating capacity.
To overcome this difficulty it is common mill practice to use steam heat in
the stuff and water. This is said to ‘dehydrate’ the stuff, but this dehydrar
tion does not reduce the strength of the paper. The increase of temperature
reduces very greatly the viscosity of water, and it is this viscosity of water

[Bentley and Jackson
Fig. 29.—The Neythor Press

92 MODERN PAPER-MAKING

which is the cause of the trouble at the machine when making thick papers
from highly fibrillated stock.

The finished sheet has its strength from the ‘fibrillated’ condition of its
mass, which is the essential factor, and not from the water which has clung to
the fibrillae, and, being only incidental to the condition, has been removed.

This explanation of what happens in the beater is supported by paper¬
making practice and common sense, and it seems to us that in no way, except
by the exercise of power, can we achieve this particular condition of stock.

Attempts have been made to reduce the time and power required for the
fibrillation of the stock by producing a formation of mucilage or slime by means
of acids or alkalis.

No success seems to have attended these experiments, which were, indeed,
doomed to failure, because they were based on a false hypothesis—namely,
that wet, greasy or slimy stock must be productive of a strong paper.

A moment’s thought would have shown that the reduction of a fibrous
material to a starchy paste could not increase its strength. The condition
aimed at in these experiments does, however, come nearer to that to which the
true meaning of the word ‘hydrated’ may be applied. But it is of interest
to note that the wetness obtained gave no additional strength or quality to
the paper, or, at the most, only what would have been achieved in greater
degree by mixing a quantity of good starch with the fibres in the beater.

There are, however, well-known methods of improving the strength and
hardness of paper by adding adhesive substances to the pulp in the beater.
These substances simply glue the fibres together at the presses and drying
cylinders of the machine. None of these in general use at present, however,
will give the increase in strength which may be obtained by skilful fibrillation.

We think that, instead of trying to fit mysterious explanations to what is,
after all, a very simple mechanical process, chemists should turn their attention
to the discovery and application of some substance, or chemical compound,
which, when mixed with, ordinary cheap paper-making material, will give a
paper with strength and qualities equal to those of a well-fibrillated sheet made
from cotton and linen fibres.

Fibrillation, with its great consumption of power, would then give place
to the cheaper method we call ‘free’ beating, and our object would be attained.

Refining

After stock has been beaten in the hollander or other beater of the same
type, and before it can be let down to the machine chests, it is necessary to set the
roll so as to ‘dear’ the fibres. This clearing consists in breaking or brushing out

REFINING

fibre clusters or particles of pulp or paper that have in some way escaped the
action of the roll and plate, or have been packed into knots or lumps by the
violence of the beating. The roll is raised so as to be just clear of the plate, and
the beaterman uses the stirring-stick fieely to turn up the stuff in those portions
of the trough that experience has shown to have a sluggish circulation. The
clearing proceeds until a sample of stuff examined in a hand-bowl shows no
lumps or knots or paper ‘bits’. This may take from 15 minutes to 1 hour,
according to the fibres or stock being treated and how it was prepared previous

[Masson, Scott and Co . Ltd.

Fig. 30.—Mascot Refiner with Top Half of Casing removed, showing Cone

to beating. Broke filled into the beater without preliminary treatment is very
difficult to clear; in fact, sooner or later uncleared bits, notwithstanding every
precaution, will get to the machine chests and spoil the paper.

A lump of pulp or paper may lodge about the plate or backfill or stick
about the bottom of the beater, and be flushed down to the chests when the
beater is emptied. This danger, and the time and power required for clearing,
brought the ‘refiner’ into being.

The refiner (Figs. 30 and 31) is a machine expressly designed for clearing
beaten stock, and its proper working position is exactly the same as the beater
roll ‘clearing’.

When the beating proper has proceeded fir enough, the action is stopped
and the refiner takes up the work. Instead of the whole charge circulating
round the beater, for the purpose of treating what is relatively a very small

MODERN PAPER-MAKING

amount of stock, and consuming time and power, the charge is let down to
the refiner chest, the stuff is immediately started on its way to the machine,
and the beater is refilled.

The refiner usually consists of a cone-shaped shell or case (Fig. 30) on the
inside of which are set, longitudinally, bars similar to those in a beater plate,
with knees or zigzag formation. An internal conical rotor fitted with straight
bars is mounted on a shaft so arranged that the bars may.be brought into close
contact with the bars on the inside of the outer shell. In some refiners there
is also a disc with corresponding blades on the rotor disc. The central rotor is

adjustable by a hand-wheel and traversing gear, which moves the shaft and
cone into the outer cone, bringing all the bars on the rotor and disc into contact.
The illustrations clearly show the arrangement of bars.

_ When properly set, stock that is clear passes readily through the marhinp
without being cut or injured; larger or uncleared fibres, knots of stuff, etc., are
caught by the bars and rubbed out or cut before they can pass through.

The stuff enters at the small end of the cone, and is discharged from a
pipe on the circumference of the disc. It is obvious that the action can be
made more drastic, though at a very great expenditure of power. The rotor
may be pressed harder against the outer cone, when the refiner takes on the
action of a beater with extreme cutting characteristics, especially as the stuff is
at a much lower consistency than in the beater. To overcome this difficulty
concentrators are sometimes used to extract water from the stock before it
enters the refiner. After passing through the refiner in a highly concentrated
condition, the stock and the extracted water are again mixed together. Under
these conditions there is no doubt that fibrillation takes place with some fibres,

REFINING

notably those that are soft and well boiled. The fibres that are most success¬
fully treated by refiners are, however, those that we have already mentioned
as requiring free beating’— i.e. mechanical pulp, esparto, etc. The fibres
from broke and waste paper, which have been already treated for paper- makin g,
and require only to be defibred, form another class which can be ‘beaten’ by
the refiner, provided always that they are well saturated with water in the
beater or breaker.

The use of the refiner has been extended in many mills using the above
classes of stock, to cover nearly the whole of the beating, the beaters or breakers

themselves being used for little more than the preliminary mixing of the stuff,
alum, size, dye, etc.

The wisdom of this method is open to question, because the refiner is
worked hard up, and fibres that ought to be brushed out and fibrillated (the
proportion of chemical wood in newsprint, for example) are cut fine to give a
close sheet, and so their full value is not obtained.

The refiner being a modified type of beating engine, it is, of course, possible
to beat certain papers by means of a series of refiners, the stock being passed
from one engine to another. A strong ‘bond’ paper may be produced from
chemical wood pulp in this way, especially successful being those mills which
can get their pulp straight from the digester. It is difficult to see what is gajo&d

96 MODERN PAPER-MAKING

by this method; a series of, say, Tower beaters would probably be more efficient
and use less power.

The refiner is a very excellent machine for certain purposes, if used with
extreme care and intelligence, but it produces disastrous results if carelessly
handled.

It is now the practice in some mills for the refiner to be placed in the
machine house and under the control of the machineman. The reason for this
is that it is becoming recognised that it is possible, by the use of refiners, to
alter slightly the appearance of the sheet and also assist the machineman in
closing up his sheet when necessary. Previously the use of a refiner was to
clear die stuff after it had been taken from the beaters into a refiner chest; the
stuff then passed from the refiner into a machine service chest. The new
practice calls for a different arrangement, which is as follows:

The refiner is placed after the stuff pump and immediately before the head
box; the stuff is left slightly longer by the beaterman than would be the case
if there were no refiner. The machineman on starting up examines the sheet
and then sets his refiner to reduce the length of fibre if necessary, and to clear
the stuff of knots. The beaterman is thus relieved of the necessity of clearing
his engine, sometimes a long and difficult business with certain furnishes, and
a lot of power is saved in the beater room. It was quite a common thing,
especially in rag mills, for a knotty engine to be let down, and thus spoil a
whole chestful of stuff. There was no alternative other than to run the stuff
out as broke. With the refiner arranged as part of the machineman’s equip¬
ment this is not so likely to happen, as the stuff from the knotty engine can
usually be cleared in a minute or two. Further, the placing of a refiner in this
position, where it deals with the stuff immediately before it passes on to the
machine, gives a far better separation of fibres, and enables a much more close
and even sheet to be made.

We are of the opinion that the time is not far distant when this method
will be universally adopted for many classes of papers. The Marshall type of
refiner (Fig. 32) seems to be peculiarly well adapted for use in this position, as
it has the additional advantage of the disc as well as the cone.

CHAPTER VH

BEATING OF VARIOUS FIBRES AND THE CHARACTERISTICS

THEY IMPART TO PAPER

Cotton—Linen—Wood Pulp—Esparto—Straw

Cotton .—Cotton may be used to produce a great variety of papers. In
practice the use of new cotton fibres is limited to the making of high-class
papers, on account of the high cost of the raw material, and the power and
labour consumed in beating, making, tub-sizing and finishing. This fibre is
supreme for very strong loan, ledger paper, thin banks and the best qualities
of writing and drawing papers.

The most durable, though perhaps not the most absorbent, blottings are
made from new cottons. The degree of fibrillation given to these papers
varies to extreme limits. Thus, for a strong loan of the substance of Large
Post 21 lb., from 6 to 8 hours’ beating may be required, while a very close
and clearly water-marked writing paper of the same substance and quality
will take from 2 to 4 hours.

Since in most ‘fine’ mills both of these papers will have to be produced
by the same beating engines, it is a matter of the highest skill to manipulate
the rolls to fibrillate the loan properly if the tackle is moderately sharp. On
the other hand, the cutting rather than fibrillating of the fibres, for the writing
paper, would be much easier to accomplish. If the tackle is dull and blunt,
the difficulty would be to get the fibres for the writing paper cut fine enough
without too much fibrillation taking place. Again, the plates and bars wear
down and become dull as time goes on, and this renders all records of roll
pressure useless, since the conditions are constantly changing. Thus we are
left, in the long run, dependent on the skill of the beaterman who knows the
conditions and beats according to his judgment. Therefore, though state¬
ments of beating time might conceivably be given for different weights and
qualities of paper, they would be correct only in a very general sense, and
only in that sense can they be given. For instance, if the paper we are con¬
sidering (a strong loan) were being dealt with by four beaters, of which one
had a fresh and consequently sharp plate, the beaterman could not by any
possible manipulation of that beater give the stuff in it the same fibrillation as

98 MODERN PAPER-MAKING

in the others in the same time. It is doubtful whether by having less pressure
on the plate and giving the stock longer time he could ever accomplish it.

Besides the condition of the tackle and the beating pressure, the concen¬
tration of the stuff makes a very great difference to the result. The strong loan
and the fine writing paper may again be instanced. In a beater nominally of
400 lb. capacity, the quantity of the former may be as much as 4 cwt., and
of the latter not more than 3 cwt. The writing paper will not have the strength
of the loan, but this is not expected, or required, the main consideration being
a close and clearly water-marked sheet. The lower the concentration of stuff
in the beater the more chance it has of being cut, owing to the fibres passing
through between the bars and plates in a thin stream, instead of a thick layer.
An exactly similar effect is seen when finishing a thin paper on the calenders.
When putting through a thicker substance with the same weight of rolls,
the finish is not so high. The thinn er paper has fewer fibres in its bulk to form
a cushion, and therefore each individual fibre has the weight more directly
applied to it.

Again, by the higher concentration of stuff, the fibres are subjected to
more pressure and rubbing on each other and against the sides and bottom of
the beater, which helps to roughen the surface of the fibres and separate the
fibrillae that have been opened up by the roll. Also, the head of stuff in front
of the roll is subjected to a battering effect by the roll bars, which is absent
when the stuff is rushing through, suspended in water. Between the plate and
the oudet of the backfall, a good deal of pressure and rubbing takes place.

Although we have taken cotton fibres as an example, these remarks are
applicable to all kinds of fibres. Cotton fibres, especially those from new
cotton cuttings or rags that have not been subjected to frequent washing and
bleaching, are very opaque and bulky. Even when well fibrillated, as in a
thin bank, this is apparent. As we have shown previously, the cotton fibre has
a peculiarity which is of the highest value in giving the qualities of strength,
bulk and opacity. This is its twisted form, which even after drastic treat¬
ment in the beater is seldom entirely lost. As an illustration of these qualities
combined, let us take a ledger paper of a substance equal to about 27 lb. Large
Post, with a water-mark. The beating time would be about 4 to 5 hours,
and our beater would be filled to about 3! cwt. of stuff. We would then
expect to find that the stuff would be rather wet on the machine, but die fibres
would be fairly long, or at least a good proportion of them. If some of these
long fibres are examined under the microscope most of them would be
readily recognised as cotton by their more or less twisted form. These are
the fibres that have escaped being much cut or fibrillated during their time in
the beater, and they form the backbone or framework of the sheet. While

BEATING COTTON

they are firmly bound together by the fibrillae, they serve to prevent the close
packing of a more highly fibrillated paper. At the same time the wetness or
fibrillation of the other fibres allows the dandy roll to make a good impression.
Thus we have the natural strength, bulk and opacity of the long fibres, and
the felting strength and clear water-mark given by the fibrillae.

While we have this illustration before us, we may just touch on a point
in beating which seems to have been overlooked by many so-called beating
experts, who seem to consider that the perfection of beating is to have the
fibres of a uniform length. This is true only so far as the beating for printing,
litho and such-like papers is concerned. But the ideal ledger paper, and indeed
many other papers, cannot be properly made by fibres beaten to a uniform
length. This is one of the factors that have kept the hollander beater in the
highest place as an efficient beating engine. Its irregular and unequal circula¬
tion, even in the best designs, ensures that many fibres are little touched, while
others may be driven through the nip many times.

Unless there were a fair proportion of long fibres to form the framework
of the sheet, there would not be much strength and bulk, and without the fine
fibrillae there would be poor water-marking and felting.

Reverting, however, to our writing-paper example, uniform length of stuff
is of more advantage, because strength may be considered of secondary impor¬
tance. The fibres being ait to produce fine stuff still retain their original charac¬
teristics, opacity and bulk. The quicker circulation of the less concentrated
and lighter-charged beater will ensure that fewer fibres escape being cut.
Cotton beaten quickly— i.e. cut fine—carries the water well up to the dandy
roll owing to the close packing of the fibres. The roll makes a good im¬
pression because there are fewer long fibres to prevent the sinking in of the
protruding letters or designs. After passing the dandy roll, however, the suction
boxes are seen to take the water out of the sheet very easily, showing that
little fibrillation has taken place in the beater.

If, however, we intend to make our writing paper of thinner substance,
say 18 lb. Large Post, we have to alter our beating a little. We must fill in
more stock and allow a litde more time to beat, so that we may have some
long fibres and more fibrillae, to help to run the paper over the machine, without
having breaks and ‘pick ups’ at the dandy roll. We can do this because the
thinner substance allows and requires more water to be used cm the machine
to close up the sheet, and the impressions of the dandy roll are more trans¬
parent. From this a step further, higher concentration of stuff and still longer
time beating, give us stock suitable for a bank paper of 15 lb. Large Post, and so
on down to thin banks of 11 lb. and under.

Reversing the process, as we increase the substance of our paper to, say.

100

MODERN PAPER-MAKING

a ledger paper of 72 lb. Imperial, we have to beat with less fibrillation. This
is not because we do not require strength, but because we find it very difficult
to get the water out of the fibrillated stuff when we run it over the wire. There¬
fore the beating is required to be a very skilful compromise between cutting
and fibrillating the fibres. We must not cut them too short or strength wifi
be badly down; we cannot leave them long and raw or we will have trouble
in getting them through the strainer plates and get a poor water-mark. In
general, with a fair quality of cotton fibres, if we treat them as for a ledger
paper of about 30 lb. in Large Post, by heating the stuff to about 90° to 95 0 F.
on the machine, a successful result will be achieved.

With substances heavier than this, strength has to be proportionally sacri¬
ficed to the capacity of the machine to extract water, and the fineness of the
strainer slits. A good cotton furnish beaten for 1 hour with sharp plates may
be run up to 150 lb. Imperial on a 40-foot wire of 66 mesh at 15 to 20 feet
per minute without heating at the machine. Heating up to 90° to ioo 0 F.
allows the stuff to be put down with a little more length, as more water can
be used to run it through the strainers.

When dealing with cotton fibres from old rags, more gentle treatment is
necessary. Fibres that have been subjected to prolonged wear and repeated
washing and bleaching before coming to the mill, and then to a fairly drastic
treatment there, have lost a great deal of their stability and bulk, and—worse
still—have become partly oxidised. Fewer twisted fibres are seen, and the most
careful beating cannot make up for the loss of their original strength. They
are also frayed apd bruised (i.e. fibrillated), and therefore work wetter on the
machine. They serve to make rag papers that may be sold comparatively
cheaply and fulfil a more modest standard of quality, and they form the basis of
the great majority of writing and ledger papers.

Old soft rags, suitably treated and beaten with very sharp roll bars and
plates, make the softest and most absorbent blottings. The beating time is
from f to 3 hours, according to substance. Blotting Demy (17^x22) varies
from 18 to 120 lb.

Owing to its absorbency and the purity of its fibres, cotton takes most
dyes very readily and produces very brilliant shades.

Cotton fibres blend extremely well with the fibres of chemical wood, and
very beautiful and useful papers of all types, from the thinne st, banks to the
thickest chromos, may be made from a mixture of the two.

The strongest form of cotton rag is that known as ‘new unbleached calico
cuttings’ from doth which has been woven from Egyptian cotton. The half
stuff from this material bleaches up to a beautiful snowy white and may be
beaten to yield very strong papers of all substances.

BEATING LINEN

IOI

In general, papers made from cotton fibres are more bulky, and ha ndle
better than those made from any other fibre, or mixture of fibres, and it is this
quality which renders them very valuable, and in fact indispensable, for papers
which are required to bulk well.

Linen .—The value of the linen fibre to the paper-maker lies in its great
capacity for fibrillation. Its thick walls are fundamentally striated and its
canal is small in comparison with its bulk. Obviously it will require heavy
beating to disintegrate it. Unless the bars and plates are very sharp it splits
more readily than it cuts. For this reason, compared to cotton, its use is rather
limited except for special papers. It is seldom, if ever, run as a whole furnish,
but it gives, even in a small proportion, „a certain ‘feel’ to paper which can
be readily distinguished by a skilled paper-maker. This feel is very difficult to
describe, but may be attributed to the cool, glossy surface of the fibre.

It does not readily take a good water-mark unless highly fibrillated, but in
the latter case the binding effect of its fibrillse gives great strengdi and hardness.
For a good ledger paper, up to 25 per cent may be used with advantage. It
must be beaten separately, and not in a beater with the other components of
the furnish, as the heavy treatment it requires would destroy the strength of
these components to a greater extent than the linen could compensate. Perhaps
neglect of this very obvious precaution is the reason why many paper-makers
assert that linen has less strength as a paper-making material than cotton.

A blend of chemical wood with 10 per cent of linen gives a paper of sur¬
prisingly good strength and hardness, and—judging from the frequency of this
combination in many papers we have examined—it is a very popular one.

Although an all-linen paper is very seldom met with, in thin papers the
proportion of linen may be greatly increased with excellent results. With
about 8 to 12 hours’ beating with dull tackle and high concentration of stuff
in the beater, a furnish of 75 per cent linen will produce a pulp that will work
extremely wet on a 66-mesh wire at 7 lb. in Large Post and give a very strong
paper.

The hardness of the linen fibre renders it more immune from serious damage
in the beater than is the case with cotton; for while a careless manipulation
of the roll during the first hour or two in the beater will ruin a furnish of cotton,
the linen seems capable of standing the weight of the roll better, and is not
so likely to be spoilt unless all the tackle is very sharp.

There are various reasons for the linen fibre bang more easily fibrillated
in the beater than cotton. In the first place, as we have already said, the structure
of the fibre lends itself to longitudinal splitting, and in addition die fibre con¬
tains knots or bulbous swellings which split and become fibrillated by the
weight of the rolL

102

MODERN PAPER-MAKING

There is, however, another reason which accounts in no small measure
for the easy fibrillation; it is, in fact, that the linen cloth, in the case of new
cuttings or used rags, has had much more hard usage during its existence prior
to its arrival at the mill .

The linen fibre, being itself hard and harsh, produces a correspondingly
hard thread and cloth. This cloth is so harsh and lacking in suppleness that
it is unsuitable for clothing or household use until it has been softened and
made pliable by the linen cloth manufacturer. To effect this softening the
cloth is beaten, or ‘beetled’, as it is called, by wooden beetles, or clubs, so
that someone else has a hand in the fibrillation of the stuff before it is put to
its various domestic uses. Again, linen being hard wearing, it lasts many years
in the form of sheets, tablecloths, etc., and in consequence it is laundered many
times more than a similar article of cotton.

All these things help in the preparation of the rags for the beater, so that
by the time the linen stock has been broken into half stuff in the beater, it is
already well fibrillated and feels wet and greasy to the touch.

The amount of linen which can be used in the furnish is really limited by
the length of the machine wire and the efficiency of the suction boxes; for if,
with 25 per cent of linen, the paper can just be couched without crushing, it
is no use to bring up the proportion of linen to 35 or 40 per cent. This will
only give the machinemen endless trouble trying to get the water out, and the
appearance of the sheet will be spoilt without any appreciable gain in the ultimate
strength of the paper.

In general, if linen is to be used, it will be found advantageous not to use
too much, but to get full value from a moderate amount by carefully beating
it with blunt tackle, and so defibring it that it will entwine and bind together
the rest of the furnish and give that characteristic hardness to the finished sheet.

When the furnish is to be 25 per cent of linen and 75 per cent of other
fibres, beaten separately in four engines, it will generally be found best to
furnish the linen first and leave the other fibres till last, as it will be the last to
reach a satisfactory state of fibrillation, providing that the tackle in all beaters
is in the same state.

Never beat a mixed furnish of cotton and linen in the same beater if it ran
possibly be avoided, for, unless the amount of linen is small, the amount of
roll required to beat it will destroy the cotton, and the result will be worse
than if no linen had been used.

Wood Pulp. So fir we have been dealing with materials that require heavy
beating or cutting. That is to say, a great deal of power is consumed by the
beating engine, in the one case for fibrillating and in the other for cutting
fibres.

BEATING WOOD PULP

103

Wood pulp fibres are short enough in themselves to need little cutting,
and they have not the structure or stability to produce extensive fibrillation.
This brings us to the obvious conclusion that it is possible to find beaters more
economical than the hollander for the treatment of wood fibres. Not that any
improvement in the quality of the paper made from wood pulp in a hollander
can be looked for by using any other type, but because it is uneconomical to
have to drive a heavy roll, whose weight is never fully used, and because of
the slow and uncertain circulation of the hollander.

The beating of wood fibres is confined in a very great measure to clearing
fibre clusters and ‘brushing’ the fibres so that they are roughened by the partial
fibrillation of their surfaces.

This suggests a type of beater with a lighter roll and quicker and more
perfect circulation than the hollander. Many good beaters of this lighter type
are now in use, such as the Taylor and Tower beaters, which have separate
circulators and light rolls, and are found to be perfectly efficient in beating
wood, esparto, and straw.

Many qualities of chemical wood pulp show a surprising degree of fibrilla¬
tion when examined under the microscope, after careful heating, and run well
on the machine. They are suitable for the cheaper kinds of typewriting papers,
and down to 15 lb. in Large Post will take nice water-marking. Under that
substance it is difficult to water-mark an all-wood furnish without a great deal
of trouble with dandy ‘pick-ups’, but very thin papers may be made with
a plain wove dandy roll. The reason for the trouble with dandy picks is the
shortness of the fibre. Certain qualities of wood pulp are, however, now
available which take a good deal of beating and produce long, wet stuff.

Wood pulp produced by the soda or sulphate processes has better bulking
qualities than sulphite pulp, but tends to be too free and raw for these papers.

Under the beating of wood pulp comes the important operation of treating
newsprint stock and stuff for cheap printings and supercalendered papers.
In these cases we have the best examples of ‘free beating’ as opposed to the
beating of cotton and linen for the manufacture of writing papers.

The beating of newsprint is usually divided into two operations; the first
consists of soaking and mixing the strong sulphite and mechanical pulps in a
large hollander type engine, which has a roll with single and equidistant bars,
as opposed to the usual clumps of three or four bars. The sulphite is furnished
first and then the moist mechanical and broke, or the broke may be mixed
up in a separate engine. The chief requirements are maximum speed in fur¬
nishing and the elimination of wire bands and bits of wood from the bale
wrappings, as these are liable to do damage later when the stuff is passing
through the refinas.

104

MODERN PAPER-MAKING

To save time in furnishing the engine all the bales of pulp required should
be stacked close round the beater, or on a wooden stage at the edge, and before
the previous lot of stuff has been emptied the hoops should be removed and
taken away.

As soon as the stuff is let down the white water is turned on and the pulp
thrown in—so many bales of sulphite followed by the required amount of
mechanical. The proportion is usually in the neighbourhood of 20 per cent
sulphite to 80 per cent mechanical.

As soon as the pulp is properly broken up and mixed, say in about 1 hour,
the valve is drawn and the stuff let down into the refiner chest. Here it is
diluted to a consistency suitable for pumping through the refining engine. It
is during its passage through the refiner that the beating (such as it is) and
clearing of the stuff are effected, and the beaterman manipulates the disc of the
refiner in the same way as the roll of the hollander is manipulated when beating
cotton and linen rags.

The consistency of the stuff as it passes through the refiner is important,
just as it was in the beater, and the more concentrated the stuff the more ‘beating’
will it get, and vice versa .

It is usual to have two refiners coupled together, the stuff passing through
the first and then straight through into the second and into the machine chests.

The chief requirements for the satisfactory production of newsprint stock
is absolute uniformity hour by hour and day by day, so that the marking can
be kept going at full speed for very long periods without breaks. Consistency
regulators should always be fitted, in order to check and maintain the uniformity
of the stuff.

Once the machine has started up and got into its stride it is up to the beater¬
man to keep his stuff absolutely regular and at a uniform degree of ‘freeness’,
so that just sufficient water will be carried to enable the sheet to be put together
and no more. Once the web reaches the suction boxes it must part readily
with its water so that it may be easily couched.

The beaterman must see that his assistants use care in furnishing so that
no pieces of wood or foreign matter get into the beater, as these things, when
broken up by the refiner, pass into the web in the form of small splinters and
shive, and cause breaks.

Properly beaten with suitable tackle, sulphite wood pulp can be made to
produce beautiful banks and bonds; and thin tissues, down to a substance of
5 lb. Double Crown, may also be made, their strength and toughness being
comparable with tissues made from rags.

The production of these thin papers necessitates long and careful beating
and proper tackle; blunt bronze bars or, better still, stone rolls give the best

BEATING ESPARTO

IP5

results, as the original length of the fibre is preserved and the long-continued
brushing out of the fibres gives the necessary fibrillation and subsequent wetness.

Esparto.—Esparto fibres are very fine and short; nevertheless they require
a certain amount of beating. This amount depends on the quality of the
grass and the treatment it has previously received. The fibres of Spanish grass
are tougher than those of African, and will stand more beating, thus giving a
stronger and harder paper. In order to eli mina te shive, esparto fibres must
be well brushed or rubbed, with as little cutting as possible. This must not
be carried too far, as they are naturally slimy, and if the process is overdone
small knots will form in the chests and strainers and the web will stick to the
press rolls of the machine.

Sometimes a charge that has been overboiled or overbleached will defy the
efforts of the beaterman to make it into a good running paper, and then the
only remedy is to increase the proportion of wood pulp in the furnish. Esparto
is not suited for running over the machine without a proportion of chemical
wood fibres to form a base or framework for the paper.

As might be expected, esparto papers are very close and regular in com¬
position and take a very dear water-mark. They take a very fine finish with
fight calendering, and give a more bulky paper than wood pulp with the same
finish. For this reason they are most suitable for fine printing papers.

Esparto is very absorbent and requires a great deal of resin size to make a
hard-sized sheet. It produces an excellent tub-sized paper with a good hard
rattle and more strength than might be expected. The uniform size of its
fibres makes it very useful for the production of stamp and cheque papers, and
such papers as must have a very accurate register of the water-mark, and the
close even surface, which no other fibre can give, is very highly prized for fine
lithographic work. Some of the ‘imitation art’ papers made in this country
with a very large proportion of esparto are the finest papers in the world for
magazine printing.

The question of the proportion of sulphite wood and esparto used in the
furnish is often decided by the respective price of the two materials. It is in
the beating of esparto papers that many experiments have been carried out
with new and revolutionary designs in beating engines.

Some of these have been quite successful, notably the Taylor and Tower
beaters, in which the stuff is circulated by a pump, up a pipe to the roll, which
stands at the top (see Figs. 23 and 24, pp. 82 and 83). The main objects of these
beaters seem to be saving of floor space, quick circulation and a saving in power.

To get the best results from esparto it is essential that the preliminary
treatment should be regular, and beater tackle should be kept in a uniformly
correct condition.

CHAPTER Vm

REPULPING ‘BROKE-EFFECT OF ADDING BROKE TO THE
FURNISH-BROKE AND WASTE

Waste paper, properly treated, is an important and valuable raw material
for the paper-maker, yet it would seem, from the inadequate space and appli¬
ances for dealing with the disintegration of broke which are found in most
mills, that this department was seldom planned out at the beginning, but was
added when the necessity was realised. Yet it is in this department that a great
deal of money may be lost or saved. There are several methods of dealing
with broke or waste paper so that it may be again used in the furnish. Wet
doctor broke horn press rolls may be carried to the beaters and packed in with
the next charge. Broke that has been dried but not tub-sized is sometimes
filled in and cleared with the other items of the furnish.

This, however, is a risky process, as even with the greatest skill and care
it is often the case that uncleared bits get into the chests.

The method employed must be one that is best adapted for the particular
qualities made, and will depend on whether waste paper bought from outside
the mill is used. So we find that nearly all mills have their own methods, of
which the following are typical:

1. Soaking in tanks.

2. Boiling or scalding (either in stationary or revolving boilers).

3. Breaking in potchers with hot water, followed by steeping in draining

tanks.

4. Boiling, followed by breaking, in edge runners, kneaders or pulpers.

.5. Breaking in pulping engines with steam or hot water, without pre¬
liminary treatment.

From the above it will be seen that there are two essential requirements:
(<*) the soaking in water (generally hot) and (b) the mechanical action of de¬
fibring. To get good results these two must be combined in the process:
(a) alone takes too long a time and too much space for tanks, with imperfectly
soaked bits left to be dealt with by the beaters; (b) requires too much power
without (a) and is useless for reducing hard-sized papers.

106

PULPING BROKE

107

1. Soaking in Tanks.—This method is used mostly in mills making low-
grade papers, such as middles or wrappers, where the presence of uncleared
bits is of little consequence. The paper, mosdy waste paper of low quality,
is put into tanks with water, the charge being pressed down with poles in
order to save space. After soaking for one or two days the pulp is dug out
and filled into the beaters.

2. Boiling in Rotary Boilers .—The two essentials are combined by this pro¬
cess, but the disintegration is not complete unless after prolonged treatment.
Paper that has been boiled is reduced in Quality’; if the boilers revolve at
a sufficiently high speed—3 revolutions per minute—excellent disintegration is
obtained, if too much water is used, size is boiled out and is lost, and the strength
of the fibres is very much lessened.

For this reason, many paper-makers prefer to defibre the broke by means

[Messrs. Masson, Scott and Co . Ltd .

FiG.33 .—The ‘Perfect* Puiper: Section showing the Revolving Shaft and Fixed Arms

of a kollergang or kneader after a light boil in either a stationary or rotary
boiler.

3. Breaking in Potchers followed by Steeping in Draining Tanks.—An old
hollander beater is generally used. The broke is filled in with water and heated
by blowing in steam to nearly boiling point. After the potcher has been fully
charged the broke is roughly broken for a short time and then run into
draining tanks. When the water is drained away, the pulp is dug out for
the beaters. This is a very expensive way of treating broke, owing to the
power required to break the paper and the steam used to heat the consents
of the potcher.

4. Breaking in Special Pulping Engines with Steam or Hot Water, without
Preliminary Treatment .—This is the best and cheapest method and is now being

MODERN PAPER-MAKING

108

used by all up-to-date mills. Among pulpers one of the most popular is the
Perfect Pulper (Fig. 33). This machine consists of a cast-iron shell of
conical shape, within which is a revolving shaft, on which is fitted a series
of curved iron teeth or arms. The inside of the conical shell is also studded
with shorter teeth, between which the revolving arms turn. At the smaller
end of the cone is a hopper into which the broke is fed together with a supply
of hot water for hard papers or cold for softer stuff. At this end the teeth are
short and stout, gradually increasing in length to fill the cone, so that the
pulp travels towards the larger end as it is broken up, the longer ones having
the more disintegrated pulp to work through. The revolving shaft and teeth
have a speed of 50 to 60 revolutions per minute and form a sort of screw,
which gradually draws the stuff to the discharge opening. The conical casting

Fig. 34.—' Watford Patent Pulper

is in two parts, of which the top half is hinged for obtaining access to the
interior. The action is continuous, but may be made intermittent if desired
by closing the discharge doors. The output is from 6 to 20 cwt. per hour,
according to the size of the pulper and the quality of the broke. The power
required is from 15 to 36 h.p. Hot or cold water or steam may be used while
feeding in the stock, but only soft papers can be properly pulped without
heat. No colour, size, loading or fine fibres are lost by this method of
pulping. Another very popular machine of the same type is the Watford
pulper.

Some pulpers are still in use which work with intermittent charges. These
are similar in construction to the dough mixers which are used in bakeries.
They consist of metal troughs in which revolve two curved ar ms with serrated
edges. The trough is gradually filled with the stock and a supply of hot water.
The broke is usually disintegrated by the time the pulper is fully loaded, which

PULPING BROKE

109

is a slow process; when ready, the whole vat is tilted with the help of heavy
counterweights, and emptied into trucks.

The Edge Runner or Kollergang (Fig. 35).—This machine is peculiar and
clumsy-looking in construction. It consists of a rather shallow circular vat
the bottom of which is of hard stone, usually granite. Through the centre is
a vertical shaft, driven from below. At right angles to this shaft, and forming
a T, another shaft carries two stone rolls, which partly roll and partly drag
on the stone bottom of the vat.

These rolls are on opposite sides of the vertical shaft, and cover all the stone
bottom, slightly overlapping each other. A usual size of roll is 6 feet in dia¬
meter, 10 inches across the face and weighs about 3 tons. They are usually of

[Messrs. Masson* Scott and Co . Ltd .

Fig. 35. —Sectional View of Kollergang or Edge Runner, showing Driving Mechanism and

Base Stone

granite with the running faces roughened to grip the pulp. They are driven
from 10 to 15 travel revolutions per minute. The power required is about
30 h.p. and the output with strong papers 4 to 6 cwt. per hour.

A steel scraper or blade follows the rolls round the vat and pulls the stuff
from the outer edges under the rolls for treatment. Sometimes the stone
bottom is made concave and the faces of the rolls are cut to correspond to
induce the pulp to fall under the rolls by its own weight.

The action of the edge runner is not only a rolling one—it is something
more. The stones being pulled round in a small circle, there is also a twisting
or screwing motion going on, similar to what takes place when a garden roller
is turned in a small space.

IIO

MODERN PAPER-MAKING

In fact, the action is about the nearest that can be obtained by mechanical
means to the pestle and mortar of the primitive paper-maker.

Although the power consumed is rather high compared to that of the
pulper for its output, it must not be forgotten that the pulp is not only defibred
but fibrillated, which is power saved in the beating engine. Therefore it is still
popular among paper-makers who are wise enough to recognise its value in
this respect. For some qualities of broke and waste paper it is a necessity,
such as imitation parchments, krafts, or other specially treated papers, which
it is nearly impossible to defibre by any other means. As against this, it has
the disadvantage of reducing to fine particles any foreign materials in the pulp.
These cannot then be got rid of very easily, as the fibres carry them round
the sand traps and through the strainers.

Also, the edge runner requires a very heavy and secure foundation and
constant and close attention from the engineer to ensure safety for the workers.

In dealing with miscellaneous waste paper, the edge runner produces results
which more than compensate for all its faults. A very important matter in
connection with the kollergang is its proper lubrication; it must be carefully
and regularly lubricated and the bearings kept cool, otherwise the stones may
crack and become useless.

In order to get the full value of broke from various qualities of paper, a
great deal of space is necessary.. It is obvious that the broke from an all-rag
paper is of much more value than that from an esparto printing, and to take
full advantage of that value, the former must be utilised in a similar paper.
This necessitates the broke being kept in separate lots until that, or a similar
variety, is again being made. This applies especially to coloured broke, which
may have to be kept separate for quite a long time.

Very few mills have space for this purpose, and a great deal of good quality
broke is sacrificed by being put into cheaper grades of paper.

All broke that is being kept for future use should be packed in good dean
bags or press packed into bales and stored in a dry place, well away from dust
and oily machinery. Before going into the boiler or pulper, all broke should
be passed over a sorting table with coarse wire mesh top, and well shaken
to get rid of dust and foreign material.

Bought waste paper requires to be sorted by skilled sorters in the same
way as rags, if it is to be used in good papers, even when bought from waste-
paper merchants who grade their paper into spedal qualities.

The Effect of adding Broke to the Furnish.—A great diversity of opinion is
observable among paper-makers as to the effects of adding repulped paper
to the furnish. No general statement can, in our opinion, be made. The
circumstances of each particular case may differ so much that quite opposite

ADDING BROKE TO FURNISH

effects may be obtained by apparently the same causes. The only way of giving
any sensible explanation is to give instances.

In the case of a machine making waterleaf paper, high-class writings or
drawings for hand-sizing, or blottings, with no resin size, alum or loading, it
would seem that no doubt would arise as to the effect of adding, say, io per
cent of the same paper in the waterleaf condition.

It is the fact, however, that the stock may be made either more ‘free’ or
more ‘wet’. If the broke is taken straight, from the machine to the beater
and added to stuff nearly ready to be put down to the stuff chest, the result
will be a freer paper. Under these conditions blotting paper will acquire a
hard and harsh ‘feel’.

This is owing to the fibres having lost their saturated condition coming
over the drying cylinders, and to the time in the beater required for pulping
being insufficient for them to become again saturated to the same extent. Also,
no doubt, some of the finer fibrillae will have been lost through the wire and
suction boxes.

Now, if the broke is filled in with the furnish at the commencement of the
beating, the fibres will become thoroughly saturated with water and become
more highly fibrillated than when first run over the machine, producing a
wetter stock. Thus the same quality of broke added at different periods of
beating will give two different results. Waterleaf broke that has been stored
long enough to have regained its normal hygroscopic condition will invariably,
on being repulped, reach the machine in a wetter condition than when it was
first made. In this instance the fibres have had time to soften and lose the
tension or stress set up by the heat of the drying cylinders, and in a lesser degree
by the pressure of the couch and press rolls, and are immediately susceptible
to additional fibrillation.

If the broke is packed into the beater in sufficient quantity to increase
materially the consistency of the stuff, higher fibrillation is certain.

Broke from tub-sized papers always produces wetter stuff. In most cases
it is added in a given quantity with the furnish in the beater, and if it has not
been boiled or overheated, the size (gelatine and resin) will still be effective
and give hardness and cohesion to the sheet.

Also it shortens the beating time considerably, since its treatment in the
pulper or edge r unne r has produced more fibrillation, and the beater takes up
‘the work at a point a good deal further advanced than when the stock was
fir.t made into paper. The other items of the furnish will not require so much
beating as they otherwise would, the fibrillae necessary being supplied from
the broke. For this reason all broke from strong papers should be kept far
use in the same quality.

II2 MODERN PAPER-MAKING

Engine or resin-sized broke, usually a lower grade of stock (wood or wood
and esparto or straw), has rather a different effect. It produces a paper that
feels more pliable and refined than can readily be obtained without it, even
after longer beating of fresh fibres. This is especially noticeable with broke
that has been through the edge runner, but pulper broke has this effect also,
though in a lesser degree. This is no doubt owing to the action of these machines
having more of a softening and fibrillating effect on the fibres than the
beater.

A very great deal depends on how the broke was beaten in the first place.
Broke from fine, free-beaten stuff will usually reduce the strength of any paper
into which it is introduced, since the operations of pulping, clearing, etc., must
of necessity reduce the length of the fibres still further. This must be borne
in mind when using broke in the furnish for thin substances, particularly those
with a water-mark, when the too lavish use of poor broke will cause a deal
of trouble with pick-ups at the dandy roll. With heavier substances, water¬
marking will be assisted, the letters on the dandy roll sinking well into the
layer of soft, fine fibres on the surface of the web.

Again, broke, even fine, short-fibred stuff, will increase the strength of
paper as in the following instance:

It sometimes happens that a chest of stuff is found to be too raw— i.e. in¬
sufficiently fibrillated. The resulting paper will have a dull water-mark, a
harsh feel, and be lacking in strength. An esparto paper beaten thus will give
trouble by sticking to the press rolls.

By adding about io to 15 per cent of well-cleared broke, the rawness of
the stuff will be overcome and the water-mark improved. The strength will
be increased because the broke fills up the interstices of the sheet and forms a
binding for the long raw fibres. The surface is made more level and uniform
and the press rolls do not so readily pluck up individual fibres. As broke
usually causes increased shrinkage on the drying cylinders, it may be used to
assist in getting the correct register of water-marks. Increased retention of
loadings, heavy colours, closer finish, etc., are also gained. Most paper-
makers will agree that they would always add broke to the furnish if it were
available.

Broke and Waste—la a mill where there are a great many changes of deckles,
etc., owing to the making of small lots, and many different grades and colours,
there is, unavoidably, a great deal of broke and more or less waste of fibres.
It is essential that this broke and waste be minimis ed as much as possible, and
this depends on the efficiency of the machinery and the skill of the workers
in handling it; also on the care taken in the handling of rags, half stuff, reels,
sheets, etc. Trucks of rags and half stuff should never be overloaded or piled

BEATING

up above the level of the edges. An overloaded truck is hard to push about and
pieces from its load fall on the floor and are carelessly put back, with sand,
dirt, or grease adhering, or flung away as waste.

In fi lli n g the beaters, no stuff should fall on the floor, but as it is not possible
to avoid this on occasion, the floor at the beater side should be kept perfectly
clean. There is no reason why this cannot be done, as, with any decent flooring,
a flush with water and a sweep off with a broom ought to remove all dust and
grit that can adhere to half stuff.

The beaterman should watch his stuff chests carefully so as to avoid over-

The making machine department is where waste is most likely to be caused
and broke to be made. Some of the broke is unavoidable; the paring that is
left in order to cut off the deckle edge is an instance, and the paper run while
changing deckles, dandy rolls, etc. But though a certain amount of broke is
unavoidable, a machineman who takes an interest and pride in his work will
try to carry through his changes so that the least possible broke is made. He
should make certain in good time that the dandy roll he is going to put on
is all correct, so that it will not be necessary to take it off again for cleaning
or repairs. As to changes of deckles, etc., it is a good plan for him to work
these out on a sheet of paper beforehand, and inform his assistant exactly what
he is going to do, and why, so that he can have intelligent assistance at any
moment in response to a signal, without loud shouting and confusion.

With regard to the paring or allowance made for cutting off the deckle
edges of the web, this must be closely watched. With deckles of about 72
inches, 2 inches are sufficient for rag papers of ordinary quality. This gives
1 inch each side before tub-sizing and | to f inch after sizing. Very strong
all-rag papers ■will require 2\ inches, to allow for the greater shrinkage in
sizing. Banks, which are apt to have ragged and lumpy edges, and do not,
on account of their thin substance, stand well up to the ripping discs of the
cutter, may with advantage be allowed 2j to 2\ inches. Engine-sized papers
of fair substance ■will be all right with 1 to i| inches. Reels that are wound
unevenly or slack are a prolific source of broke during later operations, and
reach the cutters in such condition that accurate cutting becomes a matter of
the greatest difficulty, the cutterman having to keep shifting the brackets in
order to keep the web in a central position. It would be an endless task to
enumerate all the causes of broke in the machine room, such as ‘pick up’,
‘felt rubs’, etc.; it must be left to the attention and skill of the machineman to
keep these in check. A few words might be said, however, about the waste
of fibres in starting up and shutting down the machine.

In shutting down a machine to ‘wash out’ for a fresh lot, the machine-.

MODERN PAPER-MAKING

114

man will be guided by circumstances. If colour and furnish permit, the stuff
service system need not be emptied, and here the sequence of colours, furnishes,
etc., is important.

Waste occurs every time a chest has to be washed out, and by arranging
lots in proper sequence, starting from a low shade and working up to yellows
and blues, for instance, this waste will be cut down to the minim um. The
stuff gate being shut, more water should be put on and the level of the shutes
and strainers maintained until the stuff loses so much consistency that the wire
can no longer form it into a web. The machine may be slowed and the stuff
run up the press roll when the proper substance is lost. This will save a great
deal of fibre that might otherwise be run down the drain.

When it is necessary to empty the chests and service system, the simplest
plan is to run a good supply of water into the chest when the pump shows
signs of losing grip. The pump will take the water from the chest and flush
the remainder of the' fibre from the pipe and stuff box. The pulp recovered
by these means may not be so clean as the ordinary broke, owing to the flush
of water disturbing the sand traps, but it may be used with care in lower qualities
of paper. When it is realised that in the bottom of the chest, in the stuff pipe,
stuff pump, stuff box, shutes, strainers and connecting pipes, there may be
from 50 to 200 lb. of fibres, the importance of a little care in this .connection
is manifest. A careless shut-down may easily cost the mill -£50. Ag ain, when
starting up it is a very wasteful and reprehensible practice to run the first flush
of water and stuff down the drain in order to get full weight on putting the
wire in gear.

The machine should be slowed down, so that a start can be made with
the first flush of stuff. It is quite a simple matter to speed up after a few
minutes.

When starting up the machine it will be found that the paper does not
come up to the proper shade for some time. This is due to the use of fresh
water at the start, and when the backwater begins to circulate, the colour
loading, etc., gradually work round. In very deep shades the colour will be
nearly f hour before it is quite settled. Ordinary white paper coloured with
a little ultramarine blue will come up in 15 to 30 minutes.

Also, no doubt, however well the machine has been washed up, the paper
will contain specks of dirt, strings of fibres from the strainers and bits of coloured
pulp from the previous lot. In some mills it is customary to run the web up
the press rolls for a time on starting. Others get the web right away to the
reel as soon as possible. In the first case the wet broke is easiest to repulp,
but has the disadvantage that the handling of it is more difficult and often leads
to its getting dirty. In the second case the machinemen, once the paper is

BEATING

115

on the reel, can get the substance, dandy register and drying right, and by the
time the colour has been approved the paper is correct. A fresh reel can then
be started and the first piece tom up.

Most paper-makers are unwilling to tear up as broke any paper that has
been run on the reel, and are tempted to let the doubtful start go through
in the hope that some of it will be good. But if the paper is intended for tub¬
sizing it must be remembered that the size used for the bad sheets is waste,
and so is the labour of cutting and sorting.

In the following operations of tub-sizing, drying, etc., close attention on
the part of the workers is necessary at all times to prevent blemishes and breaks.
Slips or sheets, tom from the reel at the machine, are frequent causes of broke,
and the fewest possible should be taken by the machinemen, and these should
be flagged.

Broke must not be allowed to be about on the floors to be trodden on
and thus rendered useless for repulping; cleanliness of the floors, machinery
and the hands of those who touch the paper is imperative.

CHAPTER IX

RESIN SIZING-STARCH-SILICATE OF SODA-ALUM-

LOADINGS

Resin, rosin or colophony is the solid residue of the gums or juices of coni¬
ferous trees after the evaporation of their moisture and volatile substances.
It is a weak add, to which the name abietic acid is given. Its colour ranges
from a light pale yellow to a dark brown, according to its source and the tem¬
perature used to drive off the volatile substance. It is insoluble in water, and,
when broken, the fracture shows a clear, glassy surface.

When exposed to light and air, resin changes into a crystalline substance,
becomes friable and loses its amorphous quality. This explains why resin-sized
papers gradually deteriorate, losing colour, strength and ink resistance.

Resinate of soda, resin soap or resin size is made by boiling resin with soda
ash or with caustic soda. Resin size is soluble in water, but there is always
a certain amount of free resin present, unless the soda has been used in such
proportion as to balance exactly the acid resin, when the size is called neutral.
Size which has much free rosin (20 to 25 per cent) is of a creamy or white
colour, and is called white size’, to distinguish it from the other, which is
brown in colour.

Resin size is generally made by boiling powdered resin with a solution of
soda ash in an open steam-heated vessel, the proportions being about 1 lb. of
soda ash to 6 \ or 7^ lb. of resin. This would produce a size with about 10 to
15 per cent of free rosin with 7 hours’ boiling. Those paper-mills which make
their own size have found by experiment the proportions that are most suitable
for their stock and for the hardness of their water.

Although it is about 130 years since resin was first found to have sizing
qualities, it still remains a matter of controversy as to the exact action which
causes it to be a sizing agent. It was held for a long time that resinate of
alumina (the precipitate of resin size and sulphate of alumina) was absorbed
by, or stuck to, the fibres, and filled up air space in the paper in much the same
way as gelatine size does.

Modem chemistry offers another and more probable explanation. In the
mixing of the relatively small quantity of size in the beater of stuff and water,

116

SIZING

117

the size is so much diluted as to be resolved into its component parts, free
resin and sodium hydroxide. In the same way, hydrolysis of the sulphate of
alumina produces, in its place, sulphuric acid and aluminium hydroxide. The
sulphuric acid and sodium combine to some extent to form neutral salts, thus
leaving as effective agents for sizing the free resin particles and particles of
aluminium hydroxide.

Now, research into electro-kinetics has shown that some substances are
charged with positive and some with negative electricity. Substances of opposite
charges attract each other. It will at once be seen that this has a vital bearing
on the subject.

Fibres suspended in water are charged negatively, so also are the minute
particles of resin. Therefore the addition of resin particles to the beater will
not result in the fibres being covered by the resin. They will be repelled
instead, and anyone who has watched the behaviour of stuff and resin size in
a beater before the alumina has been added will at once perceive that some
disturbing action is taking place which seems to be too great to be accounted
for by the formation of gas, causing an increase in bulk.

The particles of aluminium hydroxide, on the other hand, are charged with
a positive charge. On the addition of the alum solution the disturbance in
the beater subsides and the stuff contracts in bulk. The cellulose has attracted
to itself the positively charged aluminium, and as this is always added in excess,
it may be concluded that the negatively charged fibres have now become
positively charged, or at least coated with the positively charged aluminium
particles. Thus the fibres are now in a condition to attract the negatively
charged particles of resin, when we may assume that the action has ceased.

The excess of alumina assures that no resinous particles will remain
unattracted by the fibres or by the alumina particles.

On passing over the machine, some of these wandering particles of resin
and alumina will pass through the wire with the water, but the bulk remains
on or between the fibres, forming an ink-resisting coating or filler for air
spaces.

It has generally been assumed that the resin size must be first added to the
stock in the beater, so that it may be ‘beaten into the fibres’, but this theory
seems to indicate that the opposite would be more effective. Indeed, many
mills do hold this to be the case, and put the sulphate of alumina solution into
the beater first, to neutralise the hardness of their water, and find their sizing
improved thereby.

Bewoid Size— For years paper-makers have been looking for a method by
which resin may be incorporated in the finished sheet without the use of alkali
and alum. Until the advent of the Bewoid sizing process the nearest approach

Ii8

MODERN PAPER-MAKING

to this ideal was the making of resin size with the alkali so proportioned to the
resin that a certain percentage of the latter was uncombined. This can be
carried only to a very limited extent (the product being called white size 5 ),
as, in practice, the less alkali used the greater is the liability for the ‘free 5
resin to coagulate and cause specks to appear in the sheets on its being glazed.
As the alkali is increased to prevent this happening, so also must the quantity
of alum required to neutralise it be increased. The greater the quantity of
alum required, the greater will be the amount of sulphuric acid liberated in
the beater. Besides being a very active agent in the deterioration of the paper,
this free acid is very destructive to the beater plates and bars, and the paper
machine’s wires and equipment generally.

The ideal size, therefore, is one which requires no more alum than is neces-
■ sary to neutralise the alkaline substances in hard water, and to attract the particles
of resin to the fibres.

The Bewoid process, which was the result of years of research by Dr. Bruno
Wieger, of Brunswick, Germany, goes far towards fulfilling these conditions.
Bewoid colloid is practically a mechanical mixture of resin and water. It
contains 45 per cent resin, all of which is free—that is to say, in its natural
unhydrated state. In manufacture the resin is first melted, then mechanically
dispersed in the special Bewoid mill. From 1 to U per cent of caustic soda
is ruii in, and a small quantity of casein or gelatine is added, which covers the
particles of resin with a very thin protective coating and maintains them in
suspension. The finished size is a pure white colour and only slightly alkaline.
The alum required is therefore very much reduced, in some cases by 50 per
cent, and frothing is eliminated. As this size does not require to be ‘beaten
in it may be added to the beater as it is being emptied, or run into the stuff
chest with the alum, this avoiding the corrosive action of the alum in the
beater.

The Bewoid mill consists of the following parts: A steam-jacketed cylin¬
drical pan of 125 gallons capacity, with a manometer, safety valve, blow-off
cock, and steam trap. The vertical spindle jextends through the bottom of
the pan to a ball-bearing, and continues through the top, with bevel wheels,
to a horizontal shaft fitted with two specially designed impellers. This is
arranged to run at 70 to 200 revolutions per minute by means of a two-speed
motor. There is also a measuring vessel of 130 litres capacity graduated in
20-litre divisions, with a 2-inch and f-inch run-off pipe to run into the Bewoid
mill. The measuring vessel is supplied with a steam- and water-pipe. There
is also a small copper measuring vessel of 7 litres capacity on a tripod stand.
The method of preparation is as follows: The resin, 560 lb., is melted without
water in the Bewoid mill. Melting is assisted by circulating at the slow speed.

BEWOED SIZE

119

When European resins are used, the resin should be brought up to a tem¬
perature of 140° C. during melting, so that any crystals of a high melting-
point will be melted and dissolved. When the resin is melted the steam is
turned off, and agitation started at the high speed; 9 lb. of caustic soda in
solution is run in slowly through the 7-litre vessel. While this is running
in the casein solution is prepared; 20 litres of water is run into the 130-litre
vessel. The steam which is taken to a jet at the bottom of the vessel is turned
on and 12 lb. of casein tipped in. With the steam still on, 1 lb. 2 oz. of caustic
soda in concentrated solution is added, and the solution stirred quickly. The

[Becker and Co.

Fig. 36. —Bewoed Mill, showing Steam-jacketed Pans and Measuring Vessels

temperature should not be higher than 82° C. This is diluted to 60 litres at
33 p to 43 0 C., depending on the melting-point of the resin. When mixed, a
further 1 lb. 2 oz. of caustic soda is added.

When the 9 lb. caustic solution is all added to the resin, it is necessary to
cool the resin further to ioo° C. This can be done with water, or more con¬
veniently by using part of the casein solution through the f-inch pipe. The
correct temperature is easily observed by the sudden drop in the amount of
steam given off. If casein solution is used for this cooling, the amount used
must be replaced with water, and the bulk and temperature of the casein solu¬
tion brought up to the original figures. This 60 litres of casein solution is
run into die resin through the 2-inch pipe.

A rosin-wax size can also be produced by the Bewoid process. This mgf;

120 MODERN PAPER-MAKING

be used for special papers, but has the effect of reducing strength and making
a limp and flabby paper.

After 5 minutes the dispersion is diluted with water at 38° C.: first, 70 litres
through the f-inch pipe, and the remainder through the 2-inch pipe. As the
colloid rises up the sides of the pan during dilution the slow speed is started,
and the mill is finally filled and the agitation stopped. When filled, the size
is of 45 per cent concentration.

■S kin glue can be used as a colloidalisator in place of casein. This gives
improved sizing, but the colloid is less stable.

When usin g glue, only 8£ lb. are used at 50° C. in 60 litres, without caustic
soda. The glue should be soaked for £ hour before using. Only 8 lb. 6 oz.
of caustic soda is used instead of 9 lb., as when using casein, for the first cooling
and neutralising of the resin.

Starch—In very ancient times starch was the only material known for the
sizing of paper. It is now used in addition to other sizing agents to give a
hard rattle and an improved finish to paper. A slight increase in strength may
also be obtained by its use. It increases transparency, especially in highly
glazed papers.

A great deal must be used to get much result, as it readily drains out on the
wire and suction boxes. As it is carried mechanically by the fibres, the size
of starch granules is important. Those of potato starch are largest, maize
smaller and rice smallest of all.

Each granule is a little capsule or container filled with a gelatinous sub¬
stance. The heat of the drying cylinders, acting on the wet granule, causes it
to swell and burst, the contents fusing and binding the fibres together. Starch
is better retained by the stock in the presence of sodiuin silicate in the propor¬
tion of 1 pint of sodium silicate to 5 lb. of starch. These may be mixed together
with warm water, then heated until the starch is partly ‘burst’ and cooled
with a little cold water to stop the action. This is called starch silicate; the
precipitate is very white and has more hardening effect on the fibres than starch
or sodium silicate used alone. About 2 pints of silicate and 10 lb. of starch are
required for 4 cwt. dry weight of stock. Less resin size is used in this case.

The usual amount of alum has to be slightly increased to precipitate the
starch silicate thoroughly. Starch is, however, an expensive material to use,
and in free beaten stock its effect may be entirely lost. In well-fibrillated stuff,
which carries the granules in greater quantity, its results are more apparent.

Silicate of Soda .—The use of silicate of soda (‘waterglass’) as an auxiliary
sizing agent is gradually becoming more general, and excellent results may be
obtained by using the silicate either alone or, more often, in conjunction with
resin size and starch..

SILICATE OF SODA

121

The silicate is a compound formed by the fusion of silica with carbonate
of soda, and at ordinary temperature it is a thick, syrupy, sticky liquid which
hardens on exposure to air. It is readily soluble in warm water, and it is often
necessary, especially in cold weather, to add warm water to it before furnishing
to the beater. If this precaution is not taken, the silicate sinks to the bottom
of the trough and lies there, forming a hard, glass-like coating.

Silicate of soda is an alkaline substance, and is precipitated by alum, in
much the same way as resin size. It does not actually resist aqueous inks by
itself, and for this purpose requires the addition of resin size, the retention
of which, along with starch, colour and fillers, it greatly assists, so that it may
ultimately help in the production of a more ink-resisting paper.

Silicate increases the strength of most papers, drying hard and white, and
it also gives a greatly increased rattle and firm ‘handle’ to all papers. It
may be used with advantage to assist in making the stuff work ‘wet’ on the
machine, as it helps in the retention of water in poorly fibrillated or ‘free’
stuff.

As it is very resistant to oils, the silicate may be used to great advantage
in the making of printing papers and posters which have to resist an enormous
amount of coloured and oily inks. It also has the effect of assisting the paper
to resist the deteriorating action of sunlight.

While resin-sized papers are often inclined to be sticky at the press rolls,
silicate of soda helps to eliminate this trouble, and it also reduces cockling and
drying defects and helps the paper to He flat when cut.

The cementing action of the silicate on the fibres keeps down fluff, and
this is very beneficial in papers which have to be clearly punched or perforated
with small holes or cut into narrow strips.

Silicate of soda may be used to replace part of the resin size, and thus reduce
considerably the cost of sizing, or it may be used as an auxiliary sizing agent,
along with the usual amount of resin size. In this way it will impart additional
qualities to the paper, such as hardness, ‘snap’ and increased strength.

When the silicate, along with the requisite amount of alum, is added to the
beater, a light and bulky precipitate is formed in contact with the fibres, and
as the precipitate sticks to the fibres themselves, most of it is carried across the
wet end of the machine and is not lost in the back water.

It is also claimed that the precipitate of silicate, which consists of aluminium
oxide, aluminium silicate and silica, retains 25 per cent of its weight of moisture
when passing over the machine under the normal conditions of drying,
and this would assist in the subsequent calendering where a high finish
is desired.

It is most important that sufficient alum should be used in the preqpatatioii

122

MODERN PAPER-MAKING

of the silicate, as the silica itself gives a slightly alkaline reaction with litmus.
The contents of the beater must therefore show a definitely acid reaction,
otherwise a great amount of the value of the silicate will be wasted.

The proper order for the furnishing of the beater is to add first the silicate
of soda and, after it has become thoroughly mixed with the stuff, sufficient
alum to precipitate it completely. If resin size is also being used it should be
added later, and, finally, the alum for the resin.

As silicate of soda is manufactured in many different forms of solution,
differing in viscosity, density and alkalinity, great care must be used in selecting
the most suitable kind for sizing paper.

The amount of silicate to be used depends upon the kind of paper being
made, the substance of the paper and the effect that it is desired to produce.
If it is desired to make a paper with a very hard rattle, as much as 3 or 4 per
cent of silicate may be used, but to improve the hardness of a well-sized writing
paper,. I to 1 per cent will be sufficient.

Silicate may be used with great advantage in conjunction with starch. The
starch-silicate is made by mixing the two substances in a predetermined pro¬
portion and heating with water to about 65° C. until the starch has burst. The
mixture is then added to the furnish and sufficient alum added to precipitate
the silicate.

Starch being much more expensive than silicate of soda, the proportion of
silicate to starch should be carefully regulated in order to ensure the best sizing
and hardening results at the lowest cost.

Paperine .—Paperine is a preparation of farina which is treated with caustic
soda and acid to produce a cold water-soluble starch substitute. This material
is much more economical in use than starch, being retained in the paper to a
remarkable degree. Normally £ to 1 per cent on die dry weight of the beater
is sufficient to give increased strength and handle. It is best to add it dry to
the beater, when fiimishing in very small amounts, through a small open sieve,
which prevents the formation of coagulated lumps. These are very difficult
to dissolve and cause sticking at the press rolls, but with normal care there should
be no trouble from this source.

Alum .—This important chemical compound finds many uses in the mill ,
and it can be truly said that it is an indispensable ingredient for most
papers.

Aluminium, sulphate, Al»(SO«)», is made in three grades. The best grade,
which is used in good quality writing papers and other papers which have
to be free from iron, contains 17 to 18 per cent aluminium oxide (AhOa)
and is practically free from iron. The second quality contains 14 per cent of
alumimum oxide and a small percentage of iron, usually about 0.12 per cent

ALUM

123

or less. The third quality, usually called alumino-ferric, contains considerably
more iron than the other two, and is only used in low grades of paper; it is
also used for the purification of water.

For the highest grades of writing paper, potash alum, Al ! K,(S 0 «) < , 24 H ! 0 ,
or crystal alum is still used. This is an almost colourless salt of aluminium
and potassium sulphates, but it is very much less soluble in water than the
aluminium sulphates and much more expensive.

Alum or aluminium sulphate is generally made into a solution with
water before being added to the beater, although it is the practice in some
‘news* mills to buy it ‘kibbled’ or in powder and put it dry into the
breakers.

The best way to prepare the solution is in wooden or lead-lined tanks or
chests having lead pipes and taps. Iron or brass must not be used, as the free
acid will eat these away. Wooden tanks are usually provided, two for dis¬
solving the alum and a third and larger tank as a store, from which the solution
is run by gravity to the beater room or carried in wooden buckets.

A satisfactory method is to have a wicker cage or basket which will con-
veniendy hold the contents of one or more bags of alum, and suspend it by
means of a wooden pole across the top of the tank at such a height that the
water in the tank can reach well up the cage. The alum is put into the basket
and the tank filled with water. As soon as the water reaches the alum it readily
dissolves, and the saturated solution sinks down in the chest, allowing fresh
water to reach the alum. The action may be accelerated by rocking the basket
on the pole or by causing the circular cage to revolve.

The saturated solution will stand at about 62° to 64° Tw., and a gallon of
the solution will contain about 3^ lb. of aluminium sulphate. For convenience
in working in the mill, the solution may be diluted to 20° Tw., in which case
a gallon will contain about 1 lb. of alum.

The chief uses to which alum is put in the mill are:

1. For the precipitation of resin size.

2. For the precipitation of starch.

3. For the precipitation of silicate of soda.

4. To brighten the colour of the paper.

5. To help the resistance of the paper to ink.

6. To soften the water if it is hard.

7. To prevent or lessen frothing at the machine.

8. For the preparation of gelatine size for tub-sizing and to prevent

putrefaction.

9. To assist in the bleaching of rags.

10. As a mordant for certain dyestuffs.

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MODERN PAPER-MAKING

The acidity of sizing agents is now controlled by pH value, as are many
other reactions in the paper-mill.

A solution of alum is always dirty and full of jute, hairs, etc., from the
bags in which it comes, so that it must be carefully strained through flannel
over a fine-mesh wire cloth when it is being put into the beater, or it may be
strained when being run from the dissolving tanks to the store tank.

The furnishing of dry alum direct into the heaters is not to be recom¬
mended, even in news mills, as the hairs and other impurities contained in it
foul the sheet, and also are frequently the cause of breaks at the machine. The
provision of proper dissolving tanks is a simple and inexpensive way of avoiding
this trouble, and it is also more economical in the long run.

Loading .—There are two reasons for the loading of paper with mineral
substances. The first, and no doubt original, reason is for the purpose of
producing a cheaper paper by substituting loading for fibre. As there is no
record of the introduction of this process, we may conjecture that some astute
paper-makers kept the secret to themselves and reaped a rich harvest until it
leaked out.

The second is that the use of loading, or fillers, imparts special properties
to papers, and it is therefore a necessity for some classes of paper.

The most important of these fillers is china clay or kaolin. This is die
remains of very ancient deposits of felspar or granite. Its chemical composition
is about half silica (Si 0 2 ). The other half is made up of about 35 to 40 per
cent of alumina (AhOs), 12 to 15 per cent of water and traces of various sub¬
stances such as calcium, magnesium, iron, mica, etc.

It is found in Cornwall and Devon, but huge deposits exist in many other
parts of the world. It is usually found close under the surface, and is dug out
so that great pits are made. It is not usable without treatment, as it is mixed
up with sand and grit, mica particles, etc., and must be refined and cleaned to
be of any use to the paper-maker.

The clay is broken from the face of the pit banks by directing against it a
jet of water at high pressure, or by men with picks, who break down the
clay and direct it into a flowing stream of water. It is allowed to settle
at the bottom of the pit long enough to let the heavier substances fall to the
bottom and the clay suspended in the water is pumped to the surface. It then
passes through ‘mica drags’ or shutes; the finer particles pass through
screens, leaving mica behind. The stream of water and clay is then run to
settling ponds or pits. From thence it is run to storage tanks and the clay
falls slowly to the bottom, leaving the dear water at the top. The water
being run off, the clay is dried in drying pans or kilns and broken up for use.

As may be expected, there are many grades of clay. The best qualities

125

are free from grit and sand, and the particles are very fine and white. These
are used for coating papers. Most paper-makers’ clays contain more or less
mica, according to the quality, and this shows up in paper as glistening specks.
Clay is of a colloidal or plastic nature when mixed with water. The old cir¬
culating tanks used in some mills, combined with strainers, to separate the
clay from grit, etc., have in many mills given place to centrifugal machines,
which are more positive and continuous in their action.

Another important filler is calcium sulphate (CaSOi), known also as gypsum,
terra alba in its natural state, and as pearl hardening, crown filler, satinite, etc.,
in the artificial production. Gypsum and terra alba are the ordinary mineral
ground fine and have a crystalline structure. Pearl hardening is prepared by
precipitation with acid and is of a fine white colour, clean and free from grit.
It is partly soluble (1 lb. to 45 gallons of water), and therefore a great deal is
lost if the back water of the machine is not well conserved. It can be used to
improve the colour of high-class papers. As satin white, in paste form, it is
used for paper coating.

Magnesium silicates in the form of asbestine, agalite and talc are sometimes
used as fillers, the particles being of a fibrous form, and well retained by the
paper; they are also ‘soapy’ and give a high finish. Barytes and blanc fixe
are forms of barium sulphate. The latter is the precipitated quality and is sold
in paste form for paper coating.

Almost every paper of any substance, except hand-made and some very
expensive all-rag papers, contain mineral loading. All printing papers require
china clay, which enables the paper to have a close regular finish, and is very
absorbent of printer’s ink, besides allowing a cheaper paper to be produced.
It also takes colours well and brings up the brightness of the shades. Used in
moderate quantity in blottings, it gives a soft smooth feel, taking away a good
deal of the harshness of the fibres, and helps in the retention of the dyes, which
in this case have to be used without a mordant.

Calcium sulphate fillers are not used to such an extent as china clay, but
produce much the same results, except that they do not give the same limp
feeling and are less inclined to make the paper soft and flabby.

All these loadings, however, reduce the bulk of the paper, being twice the
weight of fibre, bulk for bulk.

A loading which has received much publicity during recent years is titanium
oxide. The particular merit claimed for this material is that it imparts a greater
degree of opacity than the commoner forms of loading. There is no doubt
that used in the correct proportion, which varies according to the degree of
opacity required, a superior result can be achieved in this respect, but it is a
very expensive material, and it is doubtful whether the weight saved by e n ab lin g

126

MODERN PAPER-MAKING

you to get an opacity 7 equal to a thicker paper pays for the cost of the titanium
oxide which is necessary to achieve this result.

It has a very small particle size, and a closed back-water system or an efficient
form of hack-water recovery plant is necessary if the maximum economy in
its use is to be achieved.

Opacity being necessary for papers such as envelope papers and printing
papers, these are usually well loaded, china clay being the filler most in use.
Writing papers may have up to 15 per cent of loading, usually china clay and
terra alba in equal proportions; S/C printings up to 25 per cent of china clay,
and in the case of imitation art, as much as it will carry, which, of course,
depends on the substance and may be as high as 30 per cent. A good heavy
filling of china clay reduces the expansion and contraction of litho papers.

The retention of loading varies considerably. China clay may be retained
to the extent of 80 per cent of the quantity put in the beaters, but is usually
about 50 per cent unless a closed back-water system is used. The retention
is governed by many factors, the chief being the degree of fibrillation of the
stock, the thickness of the paper, the nature of the loading, the characteristics
of the fibres used, the formation of the sheet on the machine, the size or other
binding substances put in the beater, the conservation of .the back water and
the length and flow of the machine shutes.

Well-fibrillated stock, and fibres that are very fine and pack closely in
paper, such as esparto and straw, have a high retention. Free stock for
blottings and harsh fibres like soda pulp from coniferous wood have a low
retention.

Papers that are heavily resin-sized or have starch, silicate of soda or other
binding substances will carry a heavy percentage of loading.

The formation of the sheet on the machine will, of course, depend on the
beating of the stuff, but too much water on the wire will mean a loss of loading
by excessive suction on the boxes. Up till recently it has always been an estab¬
lished practice to add the loading—whether it was clay, chalk, or other mineral—
to the beater, it being always maintained that if the loading were well beaten
into the stuff a greater proportion was carried through into the paper, and less
came away in the white water; this theory has been found erroneous. Much
better results are now being obtained by adding the loading with water in a
thin continuous stream to the stock before it goes on to the machine, before
the strainer. In this way there has been found to be a saving in the amount
of loading required to give a predetermined quantity in the paper. Opacity
has been improved, and less loading has had to be dealt with in the back water.
There is the additional advantage that the beaters hold more stuff and the
beater bars and plates last longer, owing to the absence of the abrasive action

127

of the clay. The bottoms of the chests and shutes are not filled with loading,
and lastly the centrifugal machines are not rapidly filled with large quantities
of loading in the bolsters. This method of adding loading gives much greater
control over the quantity, and the amount being carried in the paper can be
altered in a minute or so instead of having to wait for another engine, or a
chest of stuff to be worked out.

CHAPTER X

DYEING OF PAPER-MINERAL AND INORGANIC DYES-THE

USE OF ANILINE DYES

Dyeing of Paper -The colouring of paper to shade is the most baffling
process in paper-making. It is intricately connected with quality, beating and
making. By quality we mean not only difference in fibres as between, say,
cotton and esparto, but any difference in quality of the same fibres. No two
consignments of fines, seconds or other kinds of cotton rags are ever so much
alike as to produce identically similar fibres. All other paper-making materials
are subject, more or less, to variations, both in the condition in winch they
come to the mill and in their subsequent treatment there. For example, wood
pulp, which is the most regular of all supplies of fibre when obtained from the
same source and of the same brand, will be found to vary in colour, strength
and purity. This may be from causes quite beyond the maker’s control, such
as the condition of their raw materials, the logs from the forest, the chemicals
they use to reduce the wood to fibres, their water supply and many other
causes, some of which are known and guarded against as far as possible, while'
others are still matters of mystery. The paper-maker knows this, and if the
variations are not great, he has to accept the supply and make the best he can of
it. Unfortunately, he does not find die paper consumer quite so complacent,
and must direct all his skill to eliminate these differences and make up deficiencies
in colour, quality and strength by any means he can devise.

Rags are by far the most variable of raw materials, and unless great care
is taken in their mill treatment, the resulting half stuffs may have extreme
differences in quality. Apart from other things, colour will be the greatest
difficulty. Suppose a high-grade writing paper is being made from fines, and
the natural white colour of the bleached rags gives the correct shade to a standard
sample. The next making from a different lot of rags may be dull or yellow
compared to the first. The paper-maker may try to match his sample by
tinting the stock with blue, or blue and pink. A fair match may be obtained,
but careful examination in comparison with the previous making will show it
to look coloured instead of pure white. Then he may have to alter his
furnish to get the desired tint by adding a certain percentage of white Tags,

128

DYEING

129

perhaps new cuttings, which brings up his costs and may absorb his profit for
that making. In the meantime, as he must keep his machine running, he will
have on his hands .the paper made the dull shade when starting up, the
‘coloured’ paper and the paper made with the more expensive furnish, which
may or may not be correct.

Thus the lot will have several ‘shades’, of which he will be notified in
due course by the salle foreman, the paper salesman, the customers and his
employer, all of whom will receive his explanations with obvious incredulity.

Paper made from uncoloured rag stock has a creamy tint. If the paper is
desired to be whiter, we have to add colour to the stuff in the beater. The
dye generally used is ultramarine blue.

This colour when used in small quantities gives a bluish-white tint, verging
on green in some qualities. If the tone is desired to be creamy white, some
pink must also be added.

Cheap printing papers and other papers made chiefly from mechanical
wood are coloured with aniline dyes. The shades obtained with this mixture
of blue and pink are infinite in number. The higher the quality and purity
of the fibres, the less dye is required and the more brilliant is the colour. With
good cotton fibres £ oz. in 200 lb. of stuff makes a decided shade, but that
quantity would have little or no effect on wood pulp.

When we get to 3 or 4 oz. ultramarine blue in 200 lb. of stuff, the paper
begins to show an azure tint, which gets deeper as more blue is added, until
we arrive at what is called in the trade ‘yellow’— i.e. half-way between azure
and blue. Here again pink is employed to tone the azure to a richer shade
as required.

The beating of the stock has a great influence on its retention or absorption
of dyes. Free-beaten stuff requires more colour than fibrillated stuff. As no
two beatermen beat exactly alike in making, the shade will probably vary as
the differendy treated stuff comes to the machine.

Other causes which produce differences in shade are insufficient or irregular
bleaching, lighter or heavier filling in of the beaters, different shades of ‘broke’
in the furnish, careless weighing or measuring of the dyestuffs, too prolonged
beating, insufficient or too much sulphate of alumina and resin size, dyes not
thoroughly mixed with the stuff in the beater, stuff lying too long in the chests,
agitators running too fast or too slow, changes made in amount of water used
on the machine, and variations in weight, suction, couching, pressing, tub¬
sizing, damping or finishing.

Those mills which use surface or river water are subject to variations of its
purity, which makes it very difficult to get the same colours in summer and
winter seasons or in flood times. Where a machine has to run from one stuff

MODERN PAPER-MAKING

130

chest, even- beater that is let down is liable to upset the shade. Where two
chests are used alternately, there is less risk of shades varying except on changing
from one to another.

As for the dyes, most of them the products of intricate chemical
processes, the paper-maker has to take them on trust and find by experiment,
often costly enough, their suitability for his stock and the matching of his
samples. On long runs, apart from the start, when alterations to match the
sample are being made, there is a fair chance of producing a lot with few
variations in shade. But when making small lots, which most fine mills are
compelled to undertake, the matching of samples quickly and accurately with¬
out making many shades is a serious and difficult task, which calls for long
experience and knowledge of paper-making, and an artist’s eye for colour
or shades of colour. In a paper which may have half a dozen different dyes
combined, the paper-maker has to judge quickly and accurately which one is
out of proportion, and by how much or how little, and immediately put his
judgment to the test by making the alteration.

Unlike the artist, who can alter the tints on his canvas as often as he pleases and
presents only the finished picture as the result of his work, the paper colourman’s
alterations, correct or otherwise, are all shown by the shades in the paper.

The quantity of colour used to obtain the deeper shades of azures, blues
and tints depends on several other factors besides quality and beating. Some
of these factors are very obscure; for instance, the electrical charges in the
dyes, and their relation to the electrical charge in fibres and in the chemical
used to fix them. Certain dyes will dye or be absorbed by certain fibres very
readily; others will require the aid of alum or other mordants before they will
be of any use.

Colours that are not held by the fibres either mechanically or chemically
are lost to a great extent in the back water of the machine. In addition to the
actual value wasted, there is the difficulty of dealing with the effluent, which
is so very obvious when allowed to run into a river. Inorganic dyes such as
Venetian red, the ochres, umbers and paste pigments act mostly as fillers or
loading, and are retained best by well-fibrillated' and heavily-sized stock with
an excess of alum. Ultramarine blue is of this class.

Aniline or coal-tar dyes are more readily absorbed by the fibres, and are
retained so much better that the ‘two-sideness’ of deep tints is very much
reduced. Unfortunately, this type of dyestuff is seldom fast to light and is
therefore not often used for fine papers.

‘Two-sideness’ in paper is for the most part a beating question. Free stuff
allows the drainage of water on the machine wire, and little suction is required
on the first box to allow of a good water-mark.

DYEING

131

On. passing over the other boxes, the air is drawn readily through the sheet
and carries the coloured water along with it. With highly fibrillated stock
there is little loss of water on the wire, consequently a heavy suction is used to
bring the stuff to the right consistency for water-marking. This pulls down
the fine fibrillae into the air spaces of the sheet, and the second and third boxes
pulling heavily, take the colour from the fibres nearest the wire, but cannot
influence the surface layer very much. In this case it is little use to instruct
the machineman to ‘use less suction’. He must use suction according to the
wetness of the stock. If a paper equally coloured both sides is essential the
stuff must be beaten free, so that it is not necessary to use so much suction, and if
possible a dye used that is absorbed by the fibres instead of being mechanically
held as a loading.

Also, the drying cylinders should be so regulated that the first really hot
one comes in contact with the top side of the sheet. This ensures that if any
reduction in colour is caused by the heat, the highest coloured side will suffer
most, and the steam passing to the under side will diffuse some of the dye and
convey it to that side.

Ultramarine blue suffers some decomposition by heat and steam, therefore
it is inadvisable to use very hot water to dissolve it when putting it through
the strainer cloth or to heat the stuff on the mac hine when running azures or
blue. Smalts blue, which is entirely a loading, being really blue glass ground
fine, makes a very two-sided paper, but it is perfectly fast to light, and resists
acids, heat and moisture. It does not necessarily follow that a paper coloured
with Smalts blue will never fade, but the fading will be due to the deterioration
of the stock, which gives the same effect by lowering the tone of the ground
shade.

During the last few years some dyes have been evolved which are practically
sun-proof, but they have not yet come into general use in paper-n^aking, chiefly
owing to the extra cost.

Mineral and Inorganic Dyes .—Ultramarine blue is the principal colour used
by paper-makers to counteract or hide the natural yellowish shade of the fibres.
It is simple to use and fairly permanent, though not perfectly so. It is manu¬
factured in many qualities and shades from a purple or reddish to a green tint.

It is not affected by alkalis, but is sensitive to the action of acids. Manu¬
facturers of colours direct their energies to produce a blue that is little affected
by alum. Some very good qualities of alum-resisting ultramarine may now
be obtained at a very reasonable price, and it will be found cheaper in the long
run to use a really good grade, even though it costs a good deal more than a
doubtful one. Generally speaking, the finest ground blues are most efficient
in colouring power. Before being added to the beater, the blue should be

MODERN PAPER-MAKING

132

strained through a fine-meshed strainer cloth or bag. Warm, but not hot or
boiling, water can be used, and the colour well diluted, not more than 1 lb. to
3 gallons of water, and this only when a large quantity is being used. The stock
must be definitely acid to litmus or the colour will not hold on the machine.

For this reason it is not suited to the colouring of blottings, which require
a huge quantity to make any appreciable effect. Also, a blotting coloured
with ultramarine in any quantity will be found to emit a disagreeable odour
when used to absorb ink.

Smalts Blue is finely powdered cobalt-blue glass. It is quite unaffected by
acids or alkalis, exposure to light or by atmospheric conditions. It is expensive
to use, owing to the fact that about twenty times the quantity is required
compared to ultramarine, and its first cost is high. It is found in hand-made
writings and ledgers, and sometimes in high-class machine-made paper. In
the latter case a great deal sinks in the sand traps and is lost, so that the modem
paper-mater does not look on it with much favour and uses it only when it
is specially asked for.

Prussian Blue.— This is a chemical pigment of a green shade. It is too green
to use in white papers, but is very useful in small proportions in azures and
blues that must have a greener tint than can be obtained with ultramarine.

It is affected by alkalis, but not. by acids. Formerly it was produced by a com¬
bination of chemicals in the beater, but it can now be obtained in the form
of paste or powder, which give more regular results.

Yellow Chrome.— This also is a chemical pigment which may be made in
the beater, but it is less trouble to buy the colour in paste form. It is a lead
chromate and is very poisonous. The shade varies from a canary yellow to a
brown or orange tint.

Carbon Black.—This is a very useful pigment to have in the mill. It produces
grey tints and can be employed to sadden too brilliant tints or give darker tints
of blues, greens, etc., than can be got by these dyes alone. The paste form of
carbon black is much to be preferred to the dry condition. The latter has an
oily and fluffy character, which prevents it from mixing well with paper stock,
resulting in specks and streaks appearing in the paper after it has passed through
the presses and calenders of the machine.

Ochres and Earth Colours.—This’ is a very extensive class of mineral colours
ranging from a light yellow to a dull brown or red. They owe their tints
mainly to the presence of iron oxides. Many are of natural origin, others are
produced by burning or calcining various earths, ochres and days. They are
all heavy colours, practically permanent, and act as fillers more than dyes.

Nitrate of Iron or Iron Liquor is a chemical combination of iron and nitric .
add. It acts on fibrous materials to produce a brownish-yellow tint. Used

DYEING

133

with ultramarine blue, it turns the latter to a greenish shade and reduces the
brightness of too brilliant colours. The yellow shade is permanent and tends
to deepen with age. It is very valuable for toning down mixed furnishes, as it
acts on most fibres equally well, and does not produce the motded appearance
which is caused by toning with aniline yellow.

Carmine or Cochineal Paste is the only colour of its kind, being made from
the bodies of cochineal insects, which are parasites of the prickly pear. While
not so powerful as the brilliant pinks of the aniline class, it is peculiarly adapted
for dyeing high-class papers, owing to the ease of its manipulation and its
purity. It requires to be treated with ammonia and cream of tartar (12 lb. of
paste, 2 \ pints of liquid ammonia, 2 oz. of cream of tartar), and allowed to
stand for a week or two to mature. It is very fugitive and is seldom used alone,
being chiefly of value in combination with ultramarine for shades of white,
high-class papers.

Aniline Colours

These are produced by intricate chemical processes from coal tar in prac¬
tically every colour and shade. They are of add, basic or neutral character,
but all are fairly easy to manipulate and are fixed by alum. They are absorbed
by the fibres, but are mosdy very fugitive and susceptible to light. They
require to be dissolved in very hot water, and carefully strained to prevent
specks of undissolved colour showing in the paper. When combinations of
aniline colours are used, add and basic colours will predpitate each other in
the fibres and help to reduce die waste in the back water. They are used for
very brilliant shades, alone and with natural colours. They dye mechanical
pulp very well and more cheaply than mineral dyes. They are very useful
for blottings and other spedal papers where alum is inadmissible.

Within the last few years some very permanent dyes of this type have been
discovered, and it seems likely that in course of time the old-fashioned mineral
colours will be superseded by the modem products. It is hardly necessary to
give any list of anilin e dyes. The leading manufacturers will supply catalogues
of their products and send samples for trial; also, they will, on request, match
a sample and supply all particulars as to quantities and treatment.

Practical Notes on the Use of Aniline Dyes

- Before fibrous materials can be effectively and economically coloured with
synthetic dyes, the nature of the fibres and dyes has to be considered in relation
to their scalability. Certain dyes are said to have an affinity for certain fibres.

134

MODERN PAPER MAKING

as, for instance, basic dyes for mechanical pulp and unbleached chemical wood.
This affinity 7 has not been explained, but it seems to us that the state of the
electrical charges in the materials may have more influence than is generally
supposed, and a study of dyes and fibres in this light might be productive of
illuminating results.

Basic dyes are less fast to light, but have greater colouring power than
acid dyes. They 7 should be put into the beater before the alum and size, as
they are sensitive to alum. This latter should be used with care, no more
than is absolutely necessary 7 for sizing being put in the beater. Where the
water is very hard, a small proportion of ahim put into the beater before the
dye is added will protect the colour in some measure from the lime salts. No
other mordant is required.

Basic dyes are most suitable for soft-sized papers of cheap quality, such as
S/C tinted printings with furnishes of unbleached strong sulphite and mechanical
pulps, but may be effectively used on all papers of low quality.

Where a mixture of dyes is necessary, they should be carefully chosen so
that basic and add are well balanced. Basic dye is first added, then the acid,
and no alum or size until the beater has made a good mixture. Half the usual
alum is then put in and, after a few minutes’ run, the rest of the alum and size.
With add dyes alone the same practice should be followed, but if possible
the size should be put in with suffident time to be thoroughly mixed before
the stuff is let down to the machine.

Add dyes are best held by hard-sized papers, with a slight excess of alum.
A good white-coloured china clay greatly assists in brightening both binds of
dye. Soft water just under boiling point (190° to 195 0 F.) is most suitable and
safest for dissolving aniline dyes, with the exception of auramine, with which
water at about 140° F. should be used.

It is a bad practice to throw the dye into the beater in a dry condition,
though this is too often done to save the time and trouble of dissolving it.
Also it should not be put in altogether, but be spread round the vat or run
in slowly before the roll, otherwise there are undissolved specks of dye in the
finished paper and often motded fibres caused by the concentrated dye falling
on the fibres.

Direct dyes, which are neither acid nor basic, dye the fibres without any
mordant. They are much more light-resisting than the other aniline colours,
but do not work well with mechanical or unbleached fibres. They are chiefly
used for better-class papers, for the production of 'motded* papers, and for
coloured fibres for blottings. Sodium sulphate is the most suitable fixing agent
for use with unsized papers, the usual alum and size being sufficient to fix them
in other classes.

DYEING

135

All fibres for mottling should be dyed with direct dyes and well fixed with
sodium sulphate or common salt. After the mixture is complete, the surplus
colour should be washed out and the pulp well sized with resin size. The
coloured fibres can then be put in the beater in time to mix before the stuff is
let down to the machine.

CHAPTER XI

THE FOURDRINIER MACHINE

The modem paper-making machine is a very complicated affair. We will
not in this chapter go into the subject of any specially built machine, such as
the huge machines that are designed to make newsprint at 1500 feet or more
per minute (see Chapter XVI). We will confine our remarks to the usual
type of Fourdrinier capable of making a wide range of papers, from wood
pulp alone, wood pulp and rags, wood pulp and esparto, or those fibres in any
combination (cj. Fig. 37).

The machine actually begins at the stuff chest. These are constructed in
sizes varying according to the output of the beaters and the machine itself. For
a general purpose machine, say 92 inches wide, and running the above furnishes
at speeds up to 150 feet per minute, a chest holding tons of stuff (dry weight)
is a very convenient size. Two such chests will be necessary. They should
be set so that the bottoms are well above flood level. The waste valves will
then be safe from being dislodged by pressure from outside, and it will be
possible to wash out at all seasons of die year. Their dimensions may be such
as are most convenient—deep and narrow, or shallow and wide, but the latter
are best.

The bottoms should be concave, with all edges bevelled, the pipe to the
stuff pump connected to the lowest part, and the waste valve in a similar
position. This ensures that, when a chest is to be emptied and washed out,
no stuff will be left where the pump cannot get it. It is very important that
the last pound of stuff be taken up and over the machine. Where there are
many changes of colour, etc., a very great loss may easily occur if this point
is neglected. Both chests ought to be lined with glazed tiles, but copper or
well-glazed cement will do very well. A connecting pipe and valve between
the two chests are very useful. When the machine is stopped longer than usual
for any reason, both chests may be filled with stuff and circulated by the pump
through the connecting pipe, thus ensuring a large quantity of stuff of the same
consistency and shade. Where the chests are capable of containing not less
than 1 ton of stuff, the best plan is to run from one while the beaters are filling
the other. Then shade, weight, etc., remain constant while the whole quantity

136

THE FOURDRJNIER. MACHINE

137

in the chest is being made. The pump and overflow may then be changed over
to the second chest.

Some of the older mills are compelled to work the stuff as it is put down
from the beaters, owing to their chests being too small to hold a reasonable
quantity. Then colour, consistency, and quality of the beating may change
with each beater. This occasions a great deal of trouble with ‘shades’ and
‘weights’ in a making, as all these may alter several times in one shift. Where
a refining engine is used, the chest from which it works ought to be about
30’ cwt. capacity and kept well filled with stuff. Then, as the beaters are put
down, the change in colour, etc., if it does happen, does so gradually, and the
machineman and colourman can make correction before it gets far off the
sample. In the same way, if a machine is provided with chests that are too
small, by emptying the stuff into one and letting it come gradually through
the connecting pipe to the other from which the stuff is being worked, the
chance of differences is somewhat lessened.

But it is the worst policy for a mill making ‘fine’ papers from rags and
mixed furnishes to have to do this, for no matter how skilled the beaterman
may be, irregularities in makings (weight and especially shades) must always
follow. Also, as no two beatermen treat their stuff in the same degree as to
length, wetness, and even the quantity of water they let down with the beaters,
there are bound to be at least three upsets in the colour, make, and weight
every 24 hours. Where two chests are used alternately, it is possible to get
more strength from a mixed furnish; for instance, a paper made from £ strong
canvas, £ cotton seconds, £ wood, £ broke, and intended for a water-marked
bank, about 13 lb. Large Post substance.

By putting these fibres into separate beaters, the utmost value in length and
wetness may be got from each. But if they have to be beaten together in
one beater before the strong canvas is milled and properly cleared, the
other and softer fibres will be reduced far below their greatest possible
strength.

Agitators.—-There are two types of agitators or stirrers used in chests. The
old type is a gate-shaped contrivance with cross and diagonal bars, which
simply stirs or mixes the stuff by travelling round. The newer and more
efficient is composed of two blades, preferably copper-covered, shaped like the
propellers of a ship and fixed to a driven shaft near the bottom of the chest.
The circulation and movement of the staff may be observed when colour is
added. Put in at the side of the chest, it travels round in a spiral streak until
it reaches the centre, when it is seen to disappear downwards. Therefore,
besides the travel of the stuff round the chest, it is being thrown up from the
centre bottom to the top sides, and from there round, inwards, and down to

i 3 8 MODERN PAPER-MAKING

the bottom again. It is very important that, where esparto fibre is used, the
agitators should be run slowly, otherwise the fibre wall be rolled into little
knots or balls. As efficient stirring is absolutely essential for the mixing of
colour, loading, etc., it may be necessary to have two additional wings or
blades half-way up the centre shaft to keep a full chest properly mixed. The
top of the chests should be covered and made water-tight, leaving only a
manhole with a properly fitted lid or cover. Generally, the agitator shaft is
driven by bevel wheels on the top, and proper precautions must be taken
to prevent grease, oil or dirty water from finding their way down the shaft
or through the opening left for the shaft. This may be accomplished by having
a disc of metal r unnin g over the opening. Another, shaped like an inverted
umbrella, may be bolted on the shaft close inside the top and cleaned out every
time an opportunity occurs. Though a rinse out with the hose-pipe is sufficient
in washing out a chest on most occasions, all chests should be thoroughly
cleaned and brushed at every opportunity.

On a change from blues or colours to white, this is compulsory. Where
the water is hard, it will be found that limy ‘scale’ will form on the side
walls and blades of the agitators. Soft water is productive of ‘slime’. The
machineman should always satisfy himself that his assistant has cleaned the
chest properly before allowing the stuff to be emptied into it. The beaterman
should see that the waste valve has been replaced, and when a chest is to be
cleaned he may take the opportunity of flushing out his stuff pipes with a
copious rush of water. Complete co-operation between the machineman and
the beaterman is essential, if mistakes are to be avoided, in the matter of waste
valves, changing pump from one chest to another and having the overflow
running into the correct chest.

Portable lights should be provided for covered chests, to allow of proper
observation of the quantity of stuff and for efficient cleaning.

The Stuff Pump (Fig. 38).—There are two kinds of stuff pumps in use—the
ordinary plunger pump with lifting valves, and the centrifugal pump. A badly
fitting or dry plunger or barrel will roll up the fibres, and for this reason it is
necessary to have a jet of water constantly playing on the barrel and washing off
the little bits of fibre that may come up with each lift.

The centrifugal pump has none of these faults. Indeed, the action of the
swifdy moving blades has a certain ‘clearing’ effect on knotty or badly
cleared stuff. There are no leather or other moving valves to get out of order.
By regulating the chest pipe-gate, it may be made to supply more or less as
desired, and to keep a good level in the stuff box as the level of the stuff in the
chest goes down. Driven by one belt, it occupies very litde space, and its
simple construction ensures cleanliness and few breakdowns.. A glance at the

STUFF PUMPS 139

driving belt occasionally, however, may save the machineman an unexpected
shut.

The pipes leading from the chests to the stuff pump, and thence to the high-
level stuff box, do not, as a rule, get very dirt}’, but a scrub out once in six

.rw.

* >- ■

(

\ I

I'.'c

[Bertrams Ltd.

Fig. 38—The Plunger Type Stuff Pump, Direct Driven by Electric Motor

months is necessary to get rid of bits of metal, buttons, chips from the bars of
the beater plates, etc., which collect in the lower levels.

The Stuff Box.—This should be situated where it can easily be got at for
cleaning purposes, and in such a position that the machineman can reach it in

140

MODERN PAPER-MAKING

the shortest possible time, as it is often necessary to shut off stuff in a hurry.
Sometimes a pipe is led from the stuff box to a convenient position, and the
stuff gate made more accessible, but this entails another pipe to clean, or another
source of scale and slime. Very often very large, elaborate stuff boxes are
provided, but all that is really required is a box about 3 feet deep and 3 feet
wide, tile- or copper-lined. Larger than this means waste of stuff when running
out or changing colours.

The overflow from the box should be wide, so that there will not be a great
change in the level of the stuff with the possible variations of the stuff pump.
The overflow shute runs to the chests, with a slide or gate to direct the stuff
to either chest. The whole box and overflow pipes or shutes need very frequent
cleaning. The waste valve of the stuff box should be replaced carefully and
examined by the machineman before he starts to pump up stuff. A problem
which confronts the machineman is how he can deal with the stuff in the box
when it is left from Saturday to Monday. The stuff left in the box may be
found to have lost its water by leakage through the stuff gate. He must then
either lift it out or risk having the overflow block up by pumping up fresh stuff.
On the other hand, if the stuff gate is quite watertight, the thick stuff will
he on the bottom of the box and may-block the valve after he has started up
the machine.

If the stuff pump has a loose pulley he may stop the pump and let the stuff
run out of the box. If not, he risks broken valves if he shuts the chest valves
to stop the supply of stuff. To empty the box after the machine has been shut
down means wasting valuable material.

With a centrifugal pump the chest valve may be shut without risk of any
damage, but in both cases there still remains the contents of the pipe from the
pump to the stuff box. This shoots up, on starting again, in a thick column
and makes a mess all over the place.

The best way out of the difficulty is to try to run a chest empty when shutting
down on Saturday. The hose-pipe may then be run into the chest, or the
beaterman may put down a flush of water and clear the stuff through the pipe
and pump, and run it over the machine. In any case, when running out a
chest and changing colours, when it is necessary to shut and wash up, the pipes,
pump, stuff box, etc., should always be emptied and all the fibre possible
run over the wire. The fibre recovered in this way may be run up the press
rolls and taken back to the beating room. A very valuable help is a water
connection between the chest valve and the stuff pump; the valve may be
shut and the water run into the pipe, thus driving the stuff in front of it to
the stuff box.

The Stuff Gate .—This important valve is not apparently considered worthy

STUFF GATE

141

of much attention by the engineers who fit up our machines. It is too often
just a valve opened by a rough-threaded screw and without any gauge attached
for the machineman’s guidance. Those men who run machines making fine
papers, where there are many changes, would appreciate a valve opened by
a micrometer screw, with a good gauge, showing clearly the difference made
by the slightest alteration. A record of makings can then be kept by the
machineman with the approximate readings of the stuff-gate gauge. This, of
course, will not give the correct position for weight, speed, breadth, etc., from
one making to the next, but if carefully kept will be of very great assistance
in giving the machineman a good idea of what he may put on for a start. As
no machine is immune from stoppage through foreign substances or clumps
of uncleaned fibres coming through, or not coming through, the opening of
the stuff gate, provision should be made for a quick and full opening to clear
awav the obstruction.

It is important that the stuff gate should always be w r orked as wide as possible
to lessen this risk. Thin papers, of course, require a small opening, but the
beaterman and machineman should have a setded consistency for thick and
thin papers worked in conjunction with a written record. In this way a paper
that normally would require a small opening would be put down with more
water from the beaters and the stuff cock could then be further opened up.
The very little trouble required to keep a record of stuff-gate opening is very
amply repaid by the smarter working of the machine, quicker and more
accurate changing of sorts, and less broke. Where two chests of the same
size are worked, the consistency of the stuff, which just means weight per
ream, may be kept practically constant by careful filling to the same level.
Various devices have been tried, w 7 orked by the density or consistency of the
stuff, for regulating the stuff gate and keeping steady weight. But this is one
of the many points in paper-making where human skill cannot be replaced
entirely by automatic means. While several firms have produced many types
of consistency regulators, none of these has proved entirely satisfactory for all
kinds of paper. The very fact that there are so many varieties of these regu¬
lators on the market, and that new ones are always coming out, seems to
confirm this. A point that is worth noting is that fine stuff requires less opening
than strong stuff for the same weight per ream, and heavily loaded stuff less
than unloaded.

It is remarkable that remote controls for stuff and water gates are not standard
equipment in every paper-mill.

As these gates are usually in an elevated position by the head box, much
time and effort is wasted by the machineman when making changes. When
it is considered that until he makes an adjustment, the paper may be the wrong

142

MODERN PAPER-MAKING

weight, or otherwise badly made, with too much or too little water, the s mall
expenditure involved in fitting controls which operate at the front of the wire
is soon recovered.

The ‘Back-water 3 System (Fig. 39).—The ‘back-water system is composed
of the following main parts: A centrifugal water pump to raise the water to
the high-level ivater box. A low-level water box to collect the water from the

In this diagram are shown the essential parts of a back-water system of a paper machine. All water collected at the wet
end is pumped up to a distributing head tank, which is divided oflfby a partition. The whitewater from the smallest
compartment returns to the mixing box, and keeps the machine supplied constantly. Any excess overflows into the
large compartment of the head tank, and is distributed as shown in the diagram.

save-all trays under the wire, and from which the pump draws its main supply.
Suitable Watergate on the high-level water box to regulate the supply of water
to the stuff going over the machine. Overflow pipes at a certain level on high-
and low-level boxes. A better idea of the water system may be gathered if
it is described in action. The fresh water is turned on full to obtain a h^d of
water sufficient for the working of the stuff until its place can be tak en by back
water. The water gate and stuff gate are then opened to the estimated extent

BACKWATER

143

and the mixture of stuff and water is run to the wire. As soon as the wire is
moving, and the water begins to drain through it and fill up the low-level box
through the save-all trays and shutes, the fresh water may be partly shut off.
Sufficient overflow is left for a few minutes to compensate for any change the
machineman may make. As soon as he has got the correct proportion of the
stuff and water, the water valve may be closed, so as to leave little more than
the surface froth going down the overflow from the high-level box. This
will have the effect of overflowing the low-level box, and the fresh water
may be turned off to reduce the overflow" in the same way. If the adjustments
are correctly made, it will be found that no fresh water will be required.

The whitewater from the save-all tray and the back-water from the suction boxes are both collected in pit ‘A\ By means
of pump ‘B’ this water is conducted through the supply pipes ‘a’ to the Rotors 4 C\ and is used as spray water. The
trays ‘D’ collect this whitewater again and conduct it through the supply pipes ‘V to die existing pump for diluting
the stuff in the mixing box. Fresh water, which is necessary during the starting of the machine, is automatically
added by the floating valve *E\ ‘F’ is the turbine which causes the water to spin.

The back water will gradually attain to its full saturation of size, loading,
colour, etc., and the stuff coming from the chest will get all the benefit of
these things returned over and over again. It is an advantage to have a con¬
nection from the suction pump which deals with the suction boxes. The fine
fibres, loadings, starch, colour, etc., may then be led back to the low-level
box and any overflow pumped to a tank in the beater room to be used in
furnishing the beaters. Some ‘fine’ mills, however, prefer to lose the suction-
box water rather than risk having in the paper dirt and bits from the suction-box
packing. Still, as the machine may have a run of engine-sized or printing
paper, these otherwise wasted materials could be used.

Rotor Whitewater Circulation System (Kg. 40).-A new method of recovering
fibre and loading from excess whitewater has recently been introduced, and
quite a large number of the plants have been installed on paper machines.

144

MODERN PAPER-MAKING

Obviously the ideal conditions for a mill would be to work with a system
whereby no excess whitewater would accrue. The flow diagram shown
on p. 143 indicates where the water enters the system at the wet end. By
using a closed whitewater system it is possible in many cases to eliminate almost
entirely the use of fresh water. The whitewater flow diagram shows the scheme
of a closed whitewater system, where whitewater is used for cleaning the
strainers, killing froth, and for cleaning the wire. The use of whitewater for

Fig. 41.—Special Bends and Pipes of Rotor Whitewater Circulation System, to cause the Water to spin through
the Pipes Spirally, and thus keep the Discharge Opening Clear

this purpose makes it necessary to find special devices, which are needed to
do all this work with the same efficiency as if fresh water were used. This
system, which has been developed successfully, is known as the British Rotor
Whitewater Circulation Plant, and it makes it possible to utilise whitewater
from the save-all trays and suction boxes—before it is used for diluting the
stuff—for cleaning the strainer, killing froth, and cleaning the wire.

The principal object of this plant is to prevent the accumulation of fibre
and loading in the pipes, and also to avoid choking the holes in spray-pipes,
and further to prevent the fine fragments of fibre and loading which have
passed through the meshes of the wire and are floating suspended in water
from clustering together. This object is achieved by installing circular bends
in the piping, which give a strong spinning or spiral motion to the water
in the pipes, which keeps all the fibre and loading in suspension; Fig. 41
shows this device. The spray-pipes are of a similar construction, and have at
each end devices which create this spiral motion. The advantages which will

SAND TRAPS

145

be derived from a completely closed whitewater system are obvious, and, in
fact, all mills have always strived to achieve this end, which is so intimately
bound up with the very important saving of fresh water and the elimination
of effluent which may have to flow eventually into rivers.

If steam has to be used to heat the stuff for heavy or wet beaten papers,
the high-level water box is where it will give the most economical and efficient
results. The pipes of the water system, and indeed all pipes conveying back
water and stuff, must be copper with brass or copper bolts and nuts throughout.
The back-water pipes should be taken apart and thoroughly scoured out fre¬
quently. A tight bundle of strips of old machine wire pulled through by a
good strong rope makes a very efficient scrubber.

The water system of a machine should never be allowed to get dry. If
this happens during a shut down, or over the week-end, a quantity of scale or
slime is sure to break away when the water is put on, and may continue to
come through and get into the paper for hours. The pipes should be left
full, with a trickle coming through the water gate and a little overflowing.
It will be found, in many mills, that the pipes are allowed to go uncleaned for
months, in order to save the few hours this takes, or the few shillings paid for
overtime to the fitters who take down and replace the pipes. This is the worst
possible mistake, for a machine cannot produce clean paper if the water system
is neglected.

From now onwards we must deal with the stuff and water mixed in paper¬
making proportion, which may be from 4 to 2 parts of stuff to 100 parts of
water.

The Sand Traps .—These are the wooden shutes through which the stuff
and water flow, leaving in their passage all heavy foreign matter, such as sand,
specks of metal, etc., and any substances heavier than fibre.

A difference of opinion exists as to whether deep, narrow shutes, or wide,
shallow shutes are most efficient. It is contended by some that deep, slow-
moving stuff gives the best chance for, say, a piece of metal to fall to the.bottom.
Others say that the stream must be shallow and ripply to break up the clusters
of fibres and allow the piece of metal to drop. The truth may be with both
views, but there seems to be no reason why shutes should not be made with
a deep channel in one part and wide and shallow in the other. There ought
to be several depressions in the bottom of the shutes at intervals about 3 or
4 inches deep, in which dirt, metal, etc., may be trapped, otherwise it will
gradually travel to the end of the shutes and get into the strainers. ,

It is a very good plan to have the bottoms covered with strips of old wet
felt with a good nap and of a handy length to facilitate washing. These are
held down by strips or bars of lead. Two sets of strips should be available.

MODERN PAPER-MAKING

146

of which one set is kept clean and ready to replace the other. This will save a
few minutes’ time when washing out. The ‘hairy’ surface of the felt is very
effective in holding back sand and all solid particles. Sometimes ladders’
are laid in the bottoms of shutes. They are not much good and generally
become sources of dirt through neglect. Some mills, making fine papers,
have installed electro-magnets in their sand traps.

These magnets attract and retain all particles of iron, and even rust, so
effectively that the rusty specks and spots so often seen in tub-sized papers are
entirely eliminated. Strangely enough, specks of all kinds of metal seem to
be attracted and stick about the poles of the magnet. A good substitute for
this machine can be made by magnetising a number of old files and arranging
them on the bottom of the shutes. Though not by any means so powerful
as the-electro-magnet, these magnestised files help to do their bit in giving
clean paper.

The sand traps may be utilised to catch a little of the paper-maker’s worst
enemy—rubber. _ A board or boards fixed with their under edges just below
the level of the stuff, across the shutes, retain a great deal of scum or froth in
which may be found specks of rubber that have floated to the surface. If these
.boards are inclined at an angle away from the flow of the stuff, floating particles
of all kinds will be washed up and stranded on their sloping surfaces.

It is generally agreed that the longer the shutes the more chance has the
stuff to get rid of dirt, but there is a limit which must be set for economical
reasons. "Where very frequent changes of sorts are necessary, long shutes may
be wasteful both in stuff and time, since every alteration of stuff or water alters
the level of the stuff flow, and may even cause the dirt to be disturbed and
begin to come through with the stuff. When this happens, the only cure is
to shut and wash out the sand traps. The best plan for die machine is to have
about 50 yards of shutes, with a by-pass at 25 yards, and a short cut for very
thick or wet beaten papers. Banks and all thin papers may be run with the
full length, as they have proportionately a heavy flow of water with the stuff.
Medium weights and small orders may be run the 25 yards, and those papers
which must be run with very little water take the shortest way. If it is
attempted to run the latter class through too long shutes, the flow will be
sluggish, and most probably will follow a narrow channel in the centre, leaving
thick stuff stagnant at the sides. In connection with this, it may be mentioned
that when the machineman opens the water gate to run more water with the
stuff, the weight of the sheet increases for a few minutes, owing to the slight
flooding effect driving the stuff in front of it. Conversely, if he shuts off
water, the weight fills temporarily, owing to the checking of the flow. It
is, therefore, important that the machineman should keep accurate note of the

CENTRIFUGAL CLEANING MACHINES

147

time he makes the change and be prepared for the results, which, unless under¬
stood, may mislead him into altering his stuff gate. The best method for
keeping in touch with the weight is to follow the change by altering the driving
speed.

At one time it was considered necessary to have an elaborate ‘mixing
box’ where the stuff and water emerge from their respective gates. This
opinion still persists, but many machines have none, and never experience any
difficulty from their absence. The best mixing may be obtained by causing

the water to strike the flow of stuff as it
leaves the stuff gate at right angles on an
inclined plane, or the water may be
made to fall on it from above. The
force of the water effectually breaks
clumps of fibres and carries them well
mixed into the shutes. Any good that
a mixing box may accomplish in the
way of retaining sand or metal is counter¬

balanced by the fact that it is usually
under the level of the shutes, and in an
awkward position for being cleaned.
Adso it has to be emptied, and this means
losing stuff. The shutes should have a
fall of about 2 feet into the strainers,
and this will be ample for mixing the
fibres and water.

Centrifugal Cleaning Machines

Most mills nowadays which make IBlatkjriars Engineering Co.

fine papers rely almost entirely for the Fig - 43 —the emensato*, see iv, showing in>

r E J OPENED FOR CLEANING, AND REVEALING THE INNER

Cylinders

it from foreign matter such as metal,

sand, shive, rubber, etc., on centrifugal machines, such as the Erkensator, which
was the first of these machines. These machines depend for their efficiency
on the action of centrifugal force. The fact that cellulose, water, and to a less
extent loadings in general, have specific gravities sufficiently near to each
other, enables these to pass through the machine together, while heavier and
lighter substances are retained behind projecting rings, or in the case of lighter
particles are removed by skimmers.

The machine (Fig. 42) consists of the following parts: An outer container
with lids for access, and a trough running right round the top for receiving the

cleaning of their stock and the freeing of

MODERN PAPER-MAKING

148

clean stock. Inside, a series of phosphor bronze cylinders or rings, which fit one
inside the other, and are driven by a motor from underneath. The stuff is led
over the centre of the machine and pours down to the bottom of the innpr
container. The whole of the inner vessel is revolving at a very high speed,

THROUGH

The shaded portion represents the foreign matter trapped behind the collecting rings

so that the stuff-when it reaches the bottom is immediately flung out in all
directions against the inner wall of the innermost cylinder. The spinning
action causes the stuff to drop to the bottom of the ring, where it meets with
the opposition of a lip or ring, over which it has to pass. Behind this first lip
the heaviest particles are trapped, because their specific gravity is so great that

CENTRIFUGAL CLEANING MACHINES

149

they are unable to overcome the action of the centrifugal force, and climb
inwards over the lip. The w r ater and lighter cellulose fibres pass this lip, and

are immediately flung out fur- <-

ther into another ring, up

which they travel on account ! ‘ •

of the pressure behind them,
until they meet another pro¬
jecting lip half-way up the
second ring. Here other im¬
purities, less heavy than those
retained at the first lip, are
trapped, and the fibres and
water, passing over the lip, are
flung out still further into a
third ring of still greater diam¬
eter. They proceed to climb
up the inner wall of the third
ring, where they meet yet
another projecting lip, and it is
in this ring where most of the
shive is caught. By the time the

fibres and water have reached
the end of this third ring they
are practically entirely free from
all foreign matter which is of
a higher specific gravity than
cellulose.

At this point it is possible to
remove lighter things, such as
rubber, cork, etc. This is done by
causing the nozzle of the skim¬
mer to plough the inner surface
of the water and fibre just as it is
passing out of the final ring on
its way to the collecting trough
of the machine. This top skim¬
ming contains, of course, valu¬
able fibre, and it is at once led

Fig. 44.—Vertical Elevation and Plan of the Pusifuge
Centrifugal Stock Cleaning Machine

This machine has three internal cylinders, and is very
accessible for cleaning

into an auxiliary strainer, where the impurities are separated out of the stock,
which then goes back to the mixing-box chest or back-water supply service.

150

MODERN PAPER-MAKING

It is often argued that these centrifugal machines are wasteful of stuff, bui
when it is remembered that these machines need to be cleaned out, say, only
once every 12 hours, and in many cases at much less frequent periods, it wili
be seen that the loss is negligible, and that the greatest portion of the loss con¬
sists, in any case, of impurities.

Against this loss also must be considered the fact that the paper can be
guaranteed to be absolutely clean and free from specks, and that it is also no
longer necessary in, for instance, the case of a rag mill to employ any sorters
to sort the rags in search of buttons, metal fasteners, pins, etc. The rags, in
fact, unless they have to be sorted to remove certain qualities, can be passed

straight from the bale into the chop¬
ping machine, and all the subsequent
removal of impurities may safely be
left to the Erkensator.

To get the best results from these
machines, it is necessary that stock
passing through them should be very
dilute; in the case of wood pulp,
densities should not be greater than
0.75 per cent, and for rag stuff about
0.5 per cent or less. At these con¬
sistencies the machine will remove
practically the whole of the shive,
which has very little greater specific
gravity than the cellulose itself.

The latest centrifugal machine is
the Purifuge (Fig. 44), which works
on more or less the same lines as
the Erkensator, but it has the advantage that it is made in England by Messrs.
Vickerys.

The Bird Centrifiner, which is made by the Bird Machine Company of
Canada, is of similar design to the aforementioned centrifugal stock cleaning
machines, and has a high capacity.

It is sometimes said that the centrifugal machine removes immediately the
heavy loading material, and it must be admitted that it does this immediately
it is started up, in order to fill the ‘bolster’, as the lining inside the rings is
called. This only takes a few moments, and after that no more loading is, in
fact, removed. In order to get over this difficulty, it used to be common
practice to put in a bucketful of loading before the stock was turned on; now,
however, it has been found to be much more satisfactory, from every point

[Bird Machine Co.
Fig. 45.—Bird Centsifiner

A centrifugal stock cleaning machine, working on the
same principle as the other centrifugal machines

VORTRAP

151

of view, to add the loading in a continuous stream after the stuff has passed
through the centrifugal machine. The section of the latest type of Erkensator
can be seen in Fig. 42, and the path of the stuff can be easily traced through
the machine (Fig. 43).

The maintenance costs of these machines are extremely low; there is nothing
to go wrong with them, except, perhaps, a bearing, and there are many of

these machines running continuously which have been in operation for 20 years
without having broken down, and with no expense for repairs.

The Vortrap

The Vortrap (Fig. 46) has been produced with the idea of separating
dirt and other impurities from the stock without employing the power
anrl apparatus required in other centrifugal machines. The principle of
it depends on centrifugal action. As will be seen in the accompanying
drawing, it comprises a vertical cylinder of small diameter divided in
sections by perforated partitions. The stuff is injected into the cylinder
tangentially, causing it to spin round rather like a vortex. This action
throws the heavy particles to the outside of the cylinder, and they rise up
to the top where they meet the upper partition. Here they are deflected

152

MODERN PAPER-MAKING

downwards through the centre hole of the partition, only clean stock passing
upwards along the axis of the cylinder to the trumpet-shaped outlet. The dirt
which has passed down the centre falls into the funnel at the bottom and
thence into the waste receiver. This waste receiver can be shut off and
emptied while the Vortrap is still in operation.

It is claimed for this apparatus that it is very low in first cost compared
with other centrifugal machines, and that it separates a large quantity of the
dirt usually contained in paper stock.

Fig. 47.— Diagrammatic arrangement of a Two-Unit Dirtec Installation

The Dirtec (Fig. 47) is a static type separator for the removal of dirt from
pulp and paper stock. The machine has no moving parts, the separation being
obtained by the employment of the differences in pressure of the stock itself. It
is effective and suitable for all except the very highest grade stocks, both heavy
and light dirt being removed continuously without stopping for cleaning.

It is, however, still necessary to keep the strainer in use. Froth is produced
in great quantities by the excessive aeration in the machines. Coagulation takes
place when the stuffhas a long distance to travel to the breast box, and creates
difficulties in the formation of the sheet on the wire. Knots, s mall clumps of
unseparated fibres, and shives, such as are found in esparto and wood-pulp papers,
and which are of the same specific gravity as cellulose fibres, are still to be dealt
with. It is therefore inadvisable to run a strainer with a more open cut than is
required for getting the stuff freely through, though in some cases the cut may
be much more open.

STRAINERS

153

The earlier forms of strainers were flat boxes with perforated metal plates
forming the bottom, the perforations being in the form of narrow slits about
2 to 3 inches long. The slits vary in width according to the form of pulp which
has to be strained, and the ‘cuts’, as they are called, are known by numbers,
such as ‘3 ’ cut, or by their width in thousandths of an inch. The cuts are spaced
about J inch apart, or far enough to prevent long fibres from getting their
ends through two different slits. Flat strainers of a modified and improved
type are used extensively in America for straining all kinds of stock, and they
still have adherents in this country, especially among paper-makers dealing
with strong rag stock. These strainers consist of a flat trough, the bottom
of which is formed of the strainer plates with slits. Underneath is another
trough, the bottom consisting of a flexible metal diaphragm, attached under¬
neath to rods which in turn are in contact with cams on a rapidly revolving
shaft. These cams lift and drop the rods, and this causes the metal diaphragms
to oscillate up and down, thus causing an alternate sucking action through
the strainer plates, causing a partial vacuum on the downward stroke and a
reflex action on the upward stroke.

The suction downwards draws fibres and water through the slits, but it also
causes fibres to be drawn over the narrow slits and so clogs them up. The
‘reflex’ or upward flow on the upward stroke of the diaphragm pushes them
away, mixes them up with water, and some are thus ready to flow through
the slits at the next downward movement of the diaphragm.

If there were no ‘reflex action’, the strainer would quickly become
completely clogged up with a coating of stuff, just as in the case of the
revolving drum or mould on a ‘mould’ machine. This ‘reflex action’ is
an essential feature of all strainers, and many different methods are used to
promote it.

The slits are always narrowest at the side on which the fibres enter, and
they open out towards the opposite side. This prevents them becoming clogged
up by congregations of fibres trying to squeeze through.

The passage of the fibres and water through the slits is brought about by
two chief causes: First, gravity, or the weight of the water in which the fibres
are suspended; secondly, by the sucking action of the diaphragm.

The older type of jog strainers are operated by ratchet wheels, the teeth
of which engage and lift rods fixed to arms projecting from the sides of the
vat. The opposite side of the vat is hinged, so that the vat moves freely up
and down. The action is, therefore, actually a tipping motion. These strainers
are still much in evidence, as they are to be found in most mills, being used
in conjunction with the more recent revolving strainers as ‘back knotters’ or
auxiliary strainers, to which we shall refer in greater detail later on.

154

MODERN PAPER-MAKING

The greatest drawback to the use of these flat strainers is that they are con¬
stantly becoming filled up with the coarse stuff, shive, rubber, dirt, etc., which
they have prevented from getting through and into the paper.

In order that the strainer will still continue to pass sufficient stuff to keep
the weight right at the machine, it is necessary that it should be frequently
cleaned and rubbed over by the machineman. This is very unsatisfactory,
and it leads to lots of dirt, etc., being let through; it also takes time and inter¬
feres with the weight. Various devices have been resorted to in order to
make this cleaning automatic and continuous, but none of them is really
adequate.

In some forms a trough is provided at the opposite end to that at which the
stuff flows on, and in this the coarser and un cleaned stuff collects, along with
rubber, and is led away.

There is no doubt that one of the chief necessities which caused the inven¬
tion of the revolving strainer was the need for automatic cleaning of the plates.
In the revolving strainer the plates form the circumference of a skeleton
cylinder, which revolves partly submerged in a semicircular cast-iron trough,
and is called the drum.

There are two types, the inward and outward flow, and in both the slits
or cuts are kept clean with a strong shower of water applied by means of a
perforated pipe.

In the case of the ‘inward flow’ die stuff is led into the trough, and has to
pass through the slits into the inside of the drum, and the cuts are cleaned
by a shower pipe inside, which forces water upwards through the drum either
at the top or at the sides, well away from the stuff in the vat. Some of this
water and die fibres which it dislodges are caught in a trough and led away
to the auxiliary strainer. The remainder of the water which is not caught
and the hanks and knots of fibres fall back into the vat, and those knots which
are not broken up sink to the bottom of the vat, and either He there until cleaned
out or pass away with the dirt, etc., to the a uxiliar y strainer through a tap at
the lowest point of the trough.

In the ‘outward-flow’ strainer the shower is apphed from above and
outside the drum, and the dirt, knots, etc., fall back into a metal .trough placed
horizontally along the inside of the drum, and are washed away to the auxiliary
strainer.

The inward-flow strainer is superior to the outward-flow, especially for
better-class papers, where freedom from dirt and blemishes of all kinds is of
the first importance. It is much more easily cleaned, because most of the
objectionable stuff never gets into it, but re mains outside in the trough.

When die stuff flows in from the sand tables, any heavy dirt, grit or knots

STRAINERS

155

will naturally sink to the bottom, or if they come in low down they will be
inclined to stay down. A deep channel is provided in the bottom of the vat
in which these things collect, and a cock is usually provided, which can always
be kept partly open to allow them to be carried away to the auxiliary strainer.

Further, in some strainers an adjustable sluice is provided at about the
normal level of the stuff in the vat, and this can be so raised or lowered as to
allow the top scum, in which most of the rubber floats, to run off into the
auxiliary strainer. Thus two means are provided for getting rid of some of
the various causes of blemishes in the paper.

The principle of working of most of the inward-flow strainers is much the
same. The water in which the fibres are suspended flows through the slits
to the lower level inside, carrying fibres with it, but in order to prevent a film
of waterleaf being formed on the outside of the drum, the reflex action already
referred to has to be set up. This is done in one type of strainer by vibrating
the flexible drum itself, and so causing waves and ripples to ebb and flow
through the slits. More fibres and water will pass through than will be passed
back again, owing to gravity and the flow of water to its own level. In
the Reinicke and Jaspar, and Banning and Seybold, types of inward-flow
strainers the reflex action is caused by die oscillating of flappers, or large per¬
forated plates fixed to a strong shaft. This shaft is placed immediately under
the lowest part of the revolving drum, and it moves backwards and forwards,
causing the plates to flap like wings in the stuff and send it in waves up against
the slits of the drum.

The motion is very effective in passing the stuff through, but the mechanical
action is very drastic and, being also erratic, it entails the use of very heavy
shafting and strong metal plates, which consume a large amount of power and
lubricating oil and cause a good deal of wear.

Another excellent type of inward-flow revolving strainer is that made by
James Bertram and Sons, and known as the Leith Walk Full-Drum Strainer
(Fig. 48). This is the simplest inward-flow strainer we have seen, and it has
many advantages to recommend it. It is noiseless, simple in construction,
easily maintained and efficient in working. It consists of the usual cast-iron
vat lined with glazed tiles, and the drum may be either driven by a ratchet
mechanism, to give an intermittent motion, or it may revolve slowly and
continuously.

The method used to produce the reflex action, to induce the passage of the
stuff, is much the same as that used in the lata: models of the flat strainer;
a vibrating brass diaphragm is situated immediately below the drum, and is
actuated by two arms fixed to the vibrator and driven by a completely enclosed
driving gear below. The stroke given to the vibrator may be varied at will

MODERN PAPER-MAKING

156

while the strainer is working, and the vibrator may be removed from the
bottom of the vat without disturbing the drum.

All the driving mechanism is entirely enclosed and works in oil, so that no
water can get near it.

The pulp enters the vat below the level of the diaphragm, so that heavy
particles and dirt are inclined to stay down in the lowest part of the trough.
The stuff is pushed upwards against the lowest part of the drum, and passes

[ James Bertram and Sons Ltd.

Fig. 48.—The ‘Leith Walk’ Full-Drum Inward-Flow Revolving Strainer

through into the drum, from which it is poured out at the ends into the shute,
which takes it to the breast box.

A strong shower of water is played against the slits at the top of the drum
to clean it. This strainer is giving universal satisfaction, and possesses distinct
advantages over most of the other inward-flow strainers, not the least of which
is its freedom from a large collection of exposed working parts, belts, etc.

One of the latest strainers, and one which is giving great satisfaction in
mills using short-fibred stock, is the Bird screen (Fig. 49). This is a
large inward-flow strainer capable of passing a very large amount of stuff.

STRAINERS

157

The vibrating motion in this strainer is given to the whole vat, the drum re¬
volving without shake, and no vibrating diaphragm being necessary. The
body of the vat rests on semicircular brackets which are attached at one end
to a spring, like the wire-frame spring support of a Fourdrinier wet end; the
other end of the bracket is pivoted to the shake arm, which is actuated by a
rod connecting to an eccentric shaft. The moving vat is connected to the
fixed parts by a rubber connection.

The stuff runs into the strainer from above and flows against the revolving
drum, passing through the slits to the inside and thence out at the ends to the
breast box. There is no violent action about the vibrating movement as in
the case of the ‘Leith Walk’ and Banning and Seybold flappers, the shake
given to the vat being easy and effective. It is claimed that only 25 per cent
of power is required to drive this

strainer compared with the diaphragm
or vibrating drum type.

The plates are interchangeable. The
strainer drum is closed at one end
and discharges stuff at the other, and
double packing strips are used to make
the joint between the drum and vat,
to prevent the mixing of screened and
unscreened stock. There is a spray pipe
at the top, and the water and loosened
stuff are caught in a winged trough.

The Box Strainer is a very old, but

extremely useful, type, which is capable
of dealing with almost any class of
fibres. A metal tank is set very firmly

[Bird Machine Co. and Vickerys Ltd.
Fig. 49.— Latest Type Bold Screen

on a good solid base. Inside this is a brass rectangular framework, on which are
bolted the strainer plates. These may be of any suitable ‘cut’. They are
arranged in rows of four, sixteen in all, and form an oblong box. This
box revolves inside the ^ank, being connected at the back side through
packing glands, with a worm and screw gearing. The front side is open
through glands, and connected to a receiving box outside the main tank.
A series of rubber diaphragms or ‘bellows’ is arranged inside the plate
holder, and vibrated by a small crank and shaft which passes through the
centre of the revolving gear. The first disc or bellows makes the back

end of the plate box air- and water-tight. The strainer being set in motion,
the stuff is ran into the outer tank. The vibration of the diaphragms
soon fills the inner box, and the level of the stuff in the receiving box

158 MODERN PAPER-MAKING

outside rises until it reaches the desired level, when it is run down to the lowest
breast box.

This is an excellent strainer for high-class papers, as the plates are easily
changed for finer or coarser cut, according to die quality of the stuff, and for
cleaning. The plates may be well immersed in the stuff, and light substances
such as rubber, chips of wood, etc., float to the surface and are run off to the
auxiliary. Every part is easily accessible for cleaning purposes, and if it is
kept in good order there is no waste of stuff from rubber ends, etc.

No spray pipe can be used, therefore all the uncleared fibres and knotty
stuff collect on top of the plates and must be periodically removed by
the machine assistants. This always causes a rush of stuff to the wire,
together with tangled masses of fibres and dirt, and is the worst feature of this
strainer.

The strainer vat may be cleaned out, the plates taken off and blown by
the steam force jet and replaced in 2 to 3 hours by two men. It is not advisable
to run this type of strainer uncleaned for more than a week. Long strings of
fibres collect about the inner surfaces of the plates, and are very apt to come
away in lumps which do great damage to the wire. Also, it is not unusual for
one of the bolts holding a plate on to break or come out, leaving a hole through
which the stuff will pass unstrained. It will be readily seen that these strainers
are rather expensive to run and keep in good condition, but nevertheless they
have proved very efficient in fine mills.

Auxiliary Strainers.—In almost every mill auxiliary strainers or ‘back
knotters’ are used to deal ’with" the stuff rejected by die machine strainers, and
they do not usually receive as much attention as they should, either from the
machineman or those in authority. The idea of the auxiliary strainer is that it
should deal with all the lumps, and heavy stuff rejected by the machine strainers,
and also with any scum which may run over, and with the water used to clear
the slits. All these contain valuable paper-making material or chemicals, such
as size, alum, etc., and if they can be recovered there is a great saving and also
a reduction in the mill effluent.

This strainer usually consists of an ordinary flat jog strainer, with a fine cut
plate, and it is often placed away in a comer at the back of the other strainers,
out of sight and out of mind’. It should be placed in a pro min ent position
whenever possible, so that the machineman may see it always receives proper
attention, and that others' who pass may also see it.

In the case of rag stock, the heavy uncleared lumps and strings which gather
in the trough of the strainers, together with the top scum, containing rubber,
wood, etc., and the water from the spray pipes, should all be run into it and
strained. A good many of the lumps and strings will be broken up, especially

STRAINERS

159

if plenty of water is used, and will pass through and into the back-water system,
to be used’ again.

The rubber and pieces of wood and other light particles will float, and can
be scooped off periodically, and thus, besides the great saving which is effected,
valuable additional straining is also achieved.

The Watford Engineering Works have given a great deal of attention
recently to the production of an efficient auxiliary strainer, and these work very
well on fine rag stock and printings. This strainer (Fig. 50) consists of a cast-
iron trough, and the strainer plates, which may be either flat or curved, are

[Watford Engineering Works

Fig. 50.—The Watford Auxiliary ‘Tremor* Strainer

suspended from a shaft which runs in a tube, thus preventing the leakage of
any oil from the plummer blocks. A ‘tremor* motion is imparted to the
shaft, which passes on the ‘dither’ to the plates. The strainer works very
efficiently and is easily cleaned, as the straining portion tips up and exposes
the plates. If it is desired, the strainer can be made to work on the ‘inward-
flow’ principle, the strained stuff being passed out through a flexible tube to
the back-water pump. In this latter type the heavy stuff remains below the
plates in the bottom of the vat, and can be washed out periodically with the
hose-pipe.

This strainer, although primarily designed as an auxiliary strainer, is being
used successfully hr many mills as an ordinary strainer for the stuff itself.

CHAPTER XD

THE FOURDRINIER MACHINE (Continued)

Connecting Pipes and Shiites .—The height and situation of the strainers usually
decide whether the stuff is run to the breast box through pipes or open shutes.
Open shutes are easier to clean, but where pipes must be used they should be
of copper, have very smooth interiors and be easily taken apart for cleaning.

Dirt or any rough surface inside the pipes causes clumps of fibres to form.
This is very often the cause of a great deal of broke, as these lumps show up
very plainly as clear specks or spaces when the paper is finished. For the
same reason all shutes must be kept very clean, with no ragged wood or scale,
and inside edges should be bevelled or rounded.

The Breast Box —This is an oblong box extending across the width of the
machine. It receives the stuff from the strainers and, overflowing along its
whole length, discharges it equally over the breast board. Some machines
receiving the stuff from low-levelpipes have a series of holes in the bottom of
the box. These are connected by smaller pipes to the main stuff pipe. The
stuff then flows over the edge of a board on to the breast board. This board
is sometimes the cause of clumps of fibres forming in the stuff, especially if its
edge is badly trimmed or dirty. The best form of box is V-shaped, whether
the stuff falls into it from above or enters at the bottom.

The consistency of the stuff should be equal at the sides and the centre.
Where it enters from a series of holes in the box, from one side only, the side
of the machine where it enters has always the closest and clearest water-mark,
owing to the finest fibres coming first over the edge. The longer and heavier
fibres are flung to the other side, and the machineman is often puzzled to know
why he cannot get a uniformly made sheet all across the machine.

The whole object of the breast box is to keep the fibres in suspension in
the water, and to prevent them from coming together and forming lumps, or
settling down, and to ensure an even flow on to the wire, and that all stuff is
of equal consistency across the whole width of the machine.

From the breast box the stuff passes on to the breast board, and thence to
the apron, or the projection slice. Where an apron is used some sort of con¬
necting device is necessary to bridge the gap from the stationary box to the

160

BREAST BOX

161

oscillating board. This may be accomplished by having the breast box: at a
sufficiently high level to allow the stuff to pour over the lip into the recess of
the breast board. Another way is to bridge the gap with a strip of some strong
flexible material which is fixed to both the stationary and the moving board
by a continuous strip of metal and counter-sunk screws.

The material called ‘moleskin’ used to be very popular for the purpose,
but its hairy surface makes ‘drags’ in strong papers. Thin and flexible
leather may be obtained for the purpose, and if carefully fixed and used will
be found to give good service for about twelve months before having to be
renewed. In an emergency, a strip of good old rubber apron will answer the
purpose.

The connecting strip should be examined for any cracks or holes when the
machine is shut—about once a week, otherwise a loss of stuff may occur and
remain undetected for a long time. It should be kept wet over the week-end.

From the breast board the apron receives the stuff and delivers it to the
wire. The apron should conform with the following requirements: It must
be thin, tough, smooth, non-elastic, composed of a material that will not rub
off in pieces or flakes, or wear to a frayed surface, or edge, or wrinkle up with
changes of temperature or humidity. Fibrous materials, varnished or water¬
proofed, are sometimes used, but these cause trouble, since threads at the extreme
edge where the material is worn by the wire make streaks and lumps, especially
in tinted papers and blues and azures. Even one cotton fibre streaming from
the edge, and so small as to be almost invisible, will do this.

The life of the apron depends in a great measure on whether there are
many changes of deckle and the care which is taken by the machinemen in
making these changes; also on the method of making a reasonably water-tight
joint at the first deckle pulley. The best method is the roller apron. The
apron is taken underneath a brass plate just inside the pulley and rolled up on
a small cylinder which is kept at tension by a cord and weight. This plate is
made to be adjusted as close as possible to the wire, leaving just enough space
to let the wire run without nipping the apron. The latter is fixed to the breast
board by a brass strip and countersunk screws, except for that length at both
sides of the machine that is allowed for the maximum and minimum breadth
of deckle. A slip of brass, bent to a knee shape, keeps the loose part down
on the breast board, and may be pressed down to make a water-tight joint.
When drawing out the deckle, the roll on the cylinder must be eased off to
let the apron pay out freely and the plate and brass slip put carefully down
after the change is made.

When putting the deckle into a narrower width of sheet, the plate and dip
should be raised up and the cylinder helped to roll up the loose apron. The

162

MODERN PAPER-MAKING

reason for this is that, generally, the weight of the slices and pulleys will cause
the cross-bars to sag down a little as they are moved towards the centre, and
this must be allowed for, or the apron will be nipped between the plate and
the wire.

When the brass plate is fixed or cast in one piece with the deckle pulley
fittings, the upright pillars of the cross-rods may be raised. There is usually
provision made for this adjustment by having the pillars threaded and held by
two nuts.

It is generally found necessary to pack a handful of soft stuff at the outside
of the apron on the breast board to prevent fibres coming out and getting under
the deckle straps. This arrangement is very efficient and gives a sharp, clean
deckle edge to the web of paper. Another method is to fix the apron down
on the breast board all across its length and arrange a piece of well-wom old
couch cover on the brass plate, so that the empty space between the deckle
pulley and deckle strap and the apron is closed up. This projects in a knee
shape about ij inches over the apron, and allows the deckle to be changed
without so much risk of tearing the apron, but is not very effective and requires
very skilful handling to give a clear deckle edge.

When changing deckles, the apron ought never to be strained or pulled
very strongly, or it may then refuse to lie flat. Stuff will then run under the
raised part and make continuous streaks or rolls in the paper. A very good
plan for getting the apron to lie and remain flat is to utilise an old apron for
supporting the new one. The old apron should be cut to about two-thirds of
its width and put on underneath and along the new one. This helps to bridge
the gap between the lip of the breast board and the highest part of the breast
roll, and takes a great deal of strain and wear off the top apron. The lip or
wire edge of the apron must coincide with the centre of a tube roll, and all tube
rolls under the apron should be kept well oiled and r unnin g freely, otherwise
air will be drawn through with the wire, causing little holes or clear spots in
the paper.

After being put on and once made wet, the apron should never be allowed
to get dry; a trickle of water ought to run on to it during the week-end and
when there is a shut long enough for it to dry up.

When shutting down, all fibres and any dirt, sand, etc., must be washed
off with the hose-pipe from the apron, breast board and connecting devices,
towards the breast box. If allowed to get on the wire, it will often be found
that these hard substances will pass to the couch rolls and stick in the cover
or the guard and score or cut the top couch jacket. A very soft brush or piece
of soft felt ought to be sufficient for cleaning the apron, if cleaning is done as
often as it should be. This is one of the jobs that the machineman should do

MODERN PAPER-MAKING

164

thickness of the stuff stream can be regulated either as a whole, across the full
width of the sheet, or locally at any point on the sheet, where for some cause
or other there may be a thick or thin place.

The whole stuff gate may be opened or closed at one operation by turning
the hand wheel on the front side. The local adjustment is done by vertical
screw-threaded spindles secured to the flexible bronze upper lip of the discharge
opening (Fig. 52). The adjustments are simple, and can be made by the
machineman while the machine is running, and without having to use pieces

of paper on the slice or bits of lead on the apron, or any other troublesome and
unsatisfactory makeshifts.

A revolving, perforated copper roll, seen in the illustration (Fig. 51), is
placed just behind the discharge opening, and helps to release air bubbles; it
also keeps the fibres in a state of agitation, and therefore properly suspended in
the water.

The absence of an apron altogether on fast machines, and the use of only
a very narrow one on slow machines, saves a great deal of drag on the wire,
apart from dispensing altogether with the numerous troubles caused on all
machines by aprons, no matter how well they may be fitted.

FLOW BOX

165

There is a great saving of wear on the wire, especially on very fast machines,
where a very heavy head of stuff has to be maintained behind the usual high
slices. No pond at all has to be supported by the wire when a flow box is
used. This fact gives also greater ‘making* length of wire to the machine,
as the stuff has more room to felt and begins to drain at the breast roll itself.
The box keeps back the froth which continually forms behind the slices, and
comes away with variations in the amount of water or state of the stuff from
the beaters. It is very easily washed down when changing, and if good sprays

[RemU hti.

Fic. 52.—Latest Adjustable Type Votth Sucelbss Flow Box
Hie fiexibJe Hp 2nd adjusting rods are dearly shown

are kept in operation above the stuff behind the box there is very little trouble
from air bells.

The flow box is giving great satisfaction on many machines at present, and
is especially satisfactory on fast machines, although it is equally effective on
slow and ‘fine* machines.

Usually the principle of getting stuff satisfactorily on to the wire from the
breast box is to cause it to flow on at the same speed as the wire is travelling
except when special features are required, such as cloudiness in a ledger paper.

166 MODERN PAPER-MAKING

It thus becomes a question of adjusting the weight of the head of stuff to giv<
a pressure sufficient to force the stuff forward at the correct speed. Until the
introduction of the Voith box very litde attention had been paid to this im¬
portant subject, and in most cases the stuff came slowly forward until caughl
by the wire, and it was then whisked suddenly forward and rolled into waves
and generally disturbed, when it should have been coming under the action
of the shake and been properly felted together.

It can therefore be said that the use of the flow box helps very considerably
in forming a better and stronger sheet. The amount of stuff for a given sub¬
stance and speed is, of course, still regulated by the stuff and back-water taps,
but the head of stuff behind the box, to give the required speed of discharge
on to the wire, is regulated by the opening of the lips of the gate.

The correct adjustment of the gate and head of stuff must, of course, be
found by the machineman himself, according to the substance he is making
and the speed of the machine, just in the same way as he had to find these
adjustments with his slices. The adjustment, however, is far more easily con¬
trolled, both for the whole width of the machine—by turning a wheel—and
for any individual unequal patches by screwing the adjusting spindles up or
down. It has one great disadvantage, however, in that it cannot be used satis¬
factorily where there are many changes of deckle width. When a slice is used
it should be high, so as to allow a deep pond to be worked; 18 inches is not
too high for a machine running up to 650 feet per minute, and very much
higher for fast speeds and free stuff.

The Wire .—The wire is the most delicate and expensive part of the machine
equipment. It may be described as a sheet of fine wire gauze, joined by a
seam to form a continuous band.

The fineness of the wire, its texture and mesh, are made to suit the class of
paper for which it has to be used, and the speed at which it is to be run. The
wire is made of bronze of various alloys of copper, tin, etc., and these are
varied by the makers to obtain a combination of strength, durability, and
wearing qualities.

Machine wires may be obtained in a wide range of mesh and quality, and in
various types of weave. The old weave seems now to be giving place to long
crimp, flat-warp; and twill types of weave for which various advantages are
claimed, and the wire-makers are continuously experimenting with different
weaves, to give strength and wearing qualities, and smoothness to the under
side of the sheet of paper, so that the surface of the under side may be as nearly
as possible equal to that of the top side.

Great praise is due to the energy and extensive research work of the paper
machine wire manufacturers, who do their utmost to give the paper-makers

THE WIRE

167

exactly what they want, and enormous strides have been made in the improve¬
ment of wires and in the method of making the join during the last few years.
At this stage it is desirable to outline briefly some of these developments.

The first radical change in the construction of paper machine wires was the
introduction of long crimp or twill weave. This was done with the object
of increasing the life of the wire, and was first introduced for the manufacture
of newsprint. It remained as such for a considerable number of years. The
wire mark caused by this particular weave of wire was different from anything
previously known, and in a number of early cases was considered objectionable.
Various improvements in the weaving, however, have modified this mark in
the under side of the paper, and in nearly every case newsprint is manufactured
over twill wires, certainly on the wide machines 19 feet and over in width.

Various developments and improvements of the twill weave permitted its
application for the manufacture of finer papers, and various weaves are now
on the market known under the different titles applied to them by their various
makers, such as Superfine Quality, Flat Warp, etc., the object of these fine
weaves being to present as many places of support as possible to the under side
of the sheet during formation, and so prevent any prominent knuckle imprinting
itself into the web. The question of wire mark is no longer the source of worry
that it used to be to the fine paper-maker, and in some cases in paper
made on these new weaves it has been almost impossible for anybody but the
expert to say which was the top side and which the under side. The paper-
maker, therefore, who wishes to avoid wire mark must co-operate with the
wire-makers to provide him with the most suitable formation of weave for
his purpose.

Another very valuable attribute of these wires is the improved shape of
hole. In the ordinary plain weave the hole is of a very oblong shape, whereas
with the newer weave it is very much squarer, with a consequent reduction
in the loss of fine fibres. This can be readily seen by a comparison between
Figs. 53 and 54, both of which are 72-mesh photographed at the same magnifica¬
tion, but No. 1 is the old plain weave and No. 2 a Superfine equal to 72. It
is particularly interesting to note that the use of 90, 80 and practically all 76-
mesh wires of plain weave has been discontinued in favour of these new weaves,
with none of which it is necessary to go finer than 72.

It is not unusual, however, for mills making a wide range of papers, both of
quality and substance, to keep to one mesh and to vary the furnish and beating
to prevent ‘wire mark’, or to enable the paper to run on a fine mesh wire.

When there is more than one machine, it is more economical and efficient
to use wires with different meshes and run on each the quality that is best
suited to it

i68

MODERN PAPER-MAKING

The length of the wire depends on various circumstances, chief of which
are the speed of the machine and the quality of the paper. It is obvious that
the longer the wire the more water will drain from the stuff through the action
of the tube rolls before it reaches the suction boxes. Hence for heavy sub¬
stances and rag papers a long wire is indicated, to run at an economical speed.
On the other hand, if banks have to be made on the same machine, too little
water would be carried to the dandy roll to have a good control of the water¬
mark. Therefore a compromise has to be made, and the length of the wire
has to be decided by all the circumstances, including very often the space
available. From 40 to 60 feet give good average results, with from 16 to

[The United Wire Works Ltd.

Figs. 53 and 54,—Photographs at the Same Magnification of Plain Weave and Superfine

Weave 72 Mesh

30 tube rolls, according to their size and the speed at which die machine is
to run.

This question of length of machine wire has always been a subject of con-?
troversy among paper-makers, but before stating definitely what length of wire
is most suitable for a machine making certain classes of paper it is necessary
to take a variety of subjects into consideration.

Other things being equal, the machine on which very wet or highly fibril—
lated stock has to be worked will require a longer wire than one on which only
free stuff is worked.

The reason for this is that the wire is simply a filter for removing the water
and receiving the fibre deposit upon its surface. It is true that the sheet or

THE WIRE

169

web is formed on the wire, and that sheets of different formation and appearance
may be made on the same wire by altering slightly the lateral movement of the
wire frame and/or the amount of water in the stock, but the formation of the
sheet—even of a very strong sheet—is accomplished in a very short distance
dong the wire. After the stuff has settled down—say half-way along the wire-
no change in the position of alignment of the fibres appears to take place, and
the wire is simply carrying the web along to the first suction box. There is
something else happening, however—i.e., the removal of water by each of the
tube rolls. This water can be just as well removed by an extra suction box or
two, so that the difficulty of a short wire can be easily overcome.

On these machines where a Voith slice is used it is no longer necessary to
take up 2 or 3 feet of wire by covering it with an apron or pond of stuff behind
the slices, so that this gives more actual paper-making length on the wire.

It must be remembered, however, that there is a tendency now to prevent
water being taken out by the first few table rolls, in order that the effect of the
shake may be brought to bear on the fibres while they are still floating in water
which is not passing away through the wire. There is also a tendency for
table rolls to be substituted by flat boards or smooth surfaces of stationary
metal for the first 12 inches or more of the wire after it leaves the breast roll.

There are a good many fairly old machines running at the present time
on which very strong rag papers are made, where great difficulty is experienced
in getting the water out before the dandy and couch roll, resulting in ‘crush¬
ing’ and spoiling of the sheet. Sometimes it is quite impossible to make the
required sheet for the following reasons:

1. The stuff is too wet and the wire too short for water extraction, if suffi¬
cient water is put on to ‘make’ the sheet.

2. If water is put off at the stuff box the stuff is too inert and greasy to
shake together properly when it reaches the wire. It will also be found that
if water is put off the stuff cannot be got through the strainer, especially if it
is long as well as wet.

3. If sufficient water is put on to get the stuff through the strainer and to
make the sheet on the wire, then there is too much water at the dandy and
couch rolls. Heating the stuff will help matters, but in order to get over the
difficulty per mane ntly there are two alternatives only. First, to put in one or
two more suction boxes, with separate vacuum pumps, or increase the length
of the wire and the number of tube rolls.

Really wet, thick stuff, for strong ledgers, parts very slowly with its water,
and gradual but not too fierce suction is necessary if the work is to be properly
done.

■ The Seam .—This is the place where the two ends of the wire doth have

170

MODERN PAPER-MAKING

been joined, and whilst not so many years ago this was a source of worry and
trouble to everybody connected with the use of machine wires, the enormous
improvements which have been made in the construction of the seam due to
the research work expended has altered the position entirely. Perhaps no one
particular type of modem seam has any advantage over the other. Some are
welded, others soldered, but those constructed in the newest manner with the
latest available technique should be equal to the strength of the wire itself, nor
should they make any mark in the paper, or if they do it should be the very
minimum.

As a matter of interest a plan view (Fig. 55) is shown of one of the very

[The United Wire Works Ltd.

Figs. 55 and 5 6 . —Photographs of Hand-Sewn Seams

Fig. 55 shows how drainage is interfered with in the old type of seam, while Fig. 56 shows a more modem sewing,

in which the drainage is much improved

early types of seams, and Fig. 56 of a little more modem seam, both hand-sewn.
Fig. 57 is a modem welded joint; Fig. 58 is a soldered joint. It will be observed
that in the welded or soldered joints there is practically no obstruction to the
drainage.

There is, however, one condition which even welded or soldered joints will
not withstand, nor for that matter any wire, and that is grooving or freezing
to the suction boxes. This is a point which should be understood by every
paper-maker, foreman and machineman who wishes to get the best results,
from his wires. By the term 'grooving* is meant that each individual warp
wire as it travels across the boxes wears a channel into the top. If there are

THE WIRE

171

60 warp wires, then there are 60 channels formed in the top of the boxes,
which, if the trouble is allowed to continue, will have a formation like a minia¬
ture piece of corrugated paper. Obviously when this condition has arisen it
is impossible for the wire to travel laterally across the boxes, an essential factor
to the successful running of a paper machine wire. It will be readily under¬
stood that when the slightly thickened blobs of the weld at the joint meet the
grooves they will not fit into the grooves, as they are larger in diameter than
the wire which formed the groove. This consequently raises the wire a small
fraction off the top of the boxes, making a momentary break in the vacuum,
with a consequent mark in the paper. This is also applicable to a soldered

Fig. 57 Fig. 58

[The United Wire Works Ltd

Figs. 57 and 58.—Welded and Soldeied Joints.

joint. Not only does this objectionable feature wear out the joint, but it also
wears out the whole wire by causing grooves in every under-side warp knuckle
as it tries to travel to right or left across the boxes.

Fig. 59 is a plan view of the under side of a hand-sewn seam which has
been allowed to groove, and Fig. (So is a plan view of the under side of a twill
wire similarly worn.

Close observation of the wire when in operation should readily reveal when
it is grooving. In the first place a knock can often be heard as the joint hits
the front of the suction boxes, but apart from this the under side of the wire
shines and glistens very brighdy as compared to a wire running in the normal
manner.

172

MODERN PAPER-MAKING

The remedy, of course, is to shift slightly the offending box or boxes, or
if this fails to overcome the trouble, then it may be necessary to remove the
suction boxes from the machine and face up the tops.

Machine wire manufacturers have their own methods of overcoming this
objectionable feature, but up to date it appears that whilst they have been
successful in 99 per cent of cases, there are still the odd few which give trouble,
and when they do it is trouble indeed unless immediate steps are taken to
counteract the fruit.

The life of a wire is the length of time it runs or, more correcdy, the weight
of paper made during that time. But it can readily be understood that no

[The United Wire Works Ltd.

Figs. 59 and 60.—Photographs of the Under Sides of Hand-Sewn Seam and Twill Wire, Both of which

HAVE BEEN ALLOWED TO GROOVE

definite time or weight can be calculated on, since a machine making thin
papers will wear out a wire with less output than one making heavier sub¬
stances with the same width. The factors that influence the life of a wire are
of two kinds. First, the care taken of the wire by the machinemen and their
skill in its use, and accidental damage; secondly, those agencies which are con¬
stant and unavoidable.

In the first may be placed the putting on of the wire when new. Without
going into all the details of putting a new wire on the machine, we will just
mention some of the items where damage may be done and how to avoid it.

The box containing the wire must be carefully opened. The screws which
fasten the lid should be withdrawn entirely by the screw-driver and removed. ’

THE WIRE

173

The wire will be found packed with straw or fine wood shavings, and jammed
mdways by means of two pieces of wood nailed to the ends of the rollers or
Doles on which it is wound. It is lifted out of the box and laid on a long table,
m which there are no other objects, such as spanners, nails, etc. The two
Dieces of board are then knocked off—a smart blow with the palm of the hand
will suffice—and the rollers firmly held until both ends are clear. The covering
wrappers, on which will be found the ‘certificate’ (number, date, etc.), are
upped off with the fingers, never with a knife or other hard tool. There will
be three poles or rollers, two of which are in the centre of the web; the other
is inside, and protects the loose end, and all three are firmly bound in position
it the ends. The binding is cut while the third pole is held in position by one
man at each end, and no attempt must be made to move the position of the
pole until both ends are loose. It should then be laid gendy on the table, thus
unwinding the first turn, and withdrawn. When doing this, the machineman
should superintend and make sure that it is slowly and evenly drawn out,
and that nobody knocks the end in the process. Though the lid of the box
may be unscrewed, it is safest to leave the wire in the box until the machine
is quite ready for its reception.

The most difficult part of the work is then proceeded with. Two men
with strong hands and wrists lift the wire, by means of the ends of the two
remaining poles, slowly upwards from the table, and the loose end swings free
and must not be touched. It is advisable to steady the wire and assist in
supporting its weight by placing two men opposite the loose end, with the
palms of their hands under the roll. All obstacles should be removed from
the floor, in case a man should trip. The wire is held in line with the bottom
couch roll, which is supported by a jack or block near the centre and stands
pointing clear of the frame or brackets of the machine. The roll of wire is
then unwound far enough to allow the loose end to form a loop big enough
to receive the couch roll. This loop must be opened out by a machineman
standing inside the frame, but there should be another man at the opposite
side of the wire acting in concert and keeping the wire tight from side to side;
otherwise, if it is attempted to open out the loop at one side only, the wire
will be buckled and the mark will be permanent. In this position the wire is
advanced as far as the supporting block, when an extension is put through the
loop and takes hold of the couch-roll spindle. The weight of the roll is then
taken with this extension shaft, the block removed, and the wire slowly and
carefully carried over the roll. It will be found that if the latter is jacketed
the edge of the wire will not slip over it freely, but will be held by the
hair of the cover. This must be watched for and guarded against Once
safely on the bottom couch roll, there is not much danger of damaging

174 MODERN PAPER-MAKING

the wire if ordinary care is taken in putting through the breast and other
rolls.

The wire must be supported by two poles when putting in the ‘tube rolls’.
These poles must be held at the same height and tension, and when moved
forward as the tubes are placed in position it should be done slowly and in the
same parallel, or the wire may be buckled or wrinkled. When all the rolls
are in position and the suction boxes are levelled, the stretch roll should be
allowed to tighten the wire by its own weight only.

Then the machinemen should examine all the arrangements and see that
no pieces of wood from the save-alls or suction boxes, etc., have fallen on the
inside of the wire. The wire rolls will, of course, have been cleaned and
washed before being put in, but the hose-pipe should be freely used again.
A very wise precaution is to start the machine slowly and run the wire round
a few turns to allow it to straighten itself out, all watching carefully for any
defect or damage.

No attempt should be made to straighten the seam if it is out of square
with the edge of the wire. A slight slope is an inherent feature in some forms
of twill-woven wires and causes no trouble or difficulties in running.

If there is a top couch roll which has the effect of tightening the wire, the
stretch roll has to be freed to keep no more tension than its own weight until
the machineman finally tensions it.

Care of the Wire .—It is necessary at all times to keep a close watch on the
wire, and more especially when starting up. The wash roll under the wire,
which is cleaned by a doctor board, does not always start if the wire is not very
tight, and this may be the cause of stuff getting on to the next roll and making
a ridge in the wire. A very sharp spray of water is essential here; it should
strike the wire from the inside and impinge on the roll itself, or, better still,
two sprays are more effective, one spraying through the wire a few inches
before it reaches the wash roll, and the other after it passes the roll and impinging
on the roll at the contact point of the doctor board.

The breast roll also is a source of danger if the doctor board is not true
all across, since a very small piece of pulp or foreign substance may pass, or
even a layer of scale form, from the water getting through. Water passing
the doctor at a part where the latter fits badly will cause a ridge in the wire, if
the speed of the roll is high enough to carry the water round and under the
wire. Where wood pulp is used a very stiff and close-fitting doctor board is
required to scrape off sulphite pitch.

Before he starts the wire, the machineman ought to have a good hose-pipe
handy, with the water turned full on, ready to wash off the.-wire rolls as soon
as the paper is on the felt If the stuff should run up the top couch roll, this

THE WIRE

175

hose-pipe may be immediately used to wash it down the wire. In this case, if
my stuff has got jammed in the nip of the guard board, when the board is
lifted to free it the piece must be caught before it drops down on the wire.
It is the practice in some mills to use a ‘starting sheet’. This is laid on the
stuff as it reaches the suction boxes and may be easily caught coming through
the couch rolls, and serves to lead the w’et sheet on to the felt. If the machine
is started with the dandy roll running on the wire, this introduces an unnecessary
element of risk, since the stuff is seldom correct for taking a water mark when
it first reaches the first suction box.

Bits will be picked up by the roll, and may attain some thickness, layer by
layer, before they can be got off, generally to fall on the wire and go through
the couch rolls. Or it may happen that the stuff is more wet or more free than
the machineman has calculated on, or he may have too much or too little stuff
or water. The presence of the dandy roll then adds immensely to his diffi¬
culties. If the roll is not down, the suction boxes have a far greater chance of
taking water out of the sheet. When the machineman has got his stuff and
water suitably proportioned and his level approximately correct, he may lower
his dandy roll on to the paper with confidence. On moving the ends of the
suction boxes, or when packing them with stuff, bits may be carried round
and on to the wire rolls. An accident that is not uncommon happens when
a piece of some foreign substance, such as small stone, piece of cement, or
sandy particle, is washed into the wire by the indiscreet use of the hose-pipe
on the floor in front of the wire.

The hose-pipe, when washing up the floor, must always be directed to send
the jet away from the wire.

An uncovered strap or pulley may fling a piece of fibre, or even a belt
fastener or rivet, into the wire, or on to the table. A machineman should be
careful to have all the buttons on his clothing firmly sewn on and to remove
his collar studs when he takes charge. Any one of these may fall or jerk on to
the wire when he leans over the slices or other adjustments. When putting
on or repairing connecting strips or aprons, all tacks, screws, pieces of rubber,
etc., and all tools should be picked up and accounted for before moving the
wire again. When removing stringy fibres from the dices, no hard, pointed
instrument may be employed. The best method is to run the tip of the finger
along the edge.

No spanners, broke, etc., should be thrown down near the wire, and the
space both at back and front should be kept dean and as dear of all machine-
house fittings as possible. Shake must be stopped as soon as paper is off the
wire.

When the machine is shut for the week-end, sufficient sprays to keep the

MODERN PAPER-MAKING

176

wire wet should be left on. Some managers insist that all water be shut off
in the machine room, but when this is done suction boxes, couch-roll covers,
apron and connecting straps dry up and get spoiled by shrinkage, etc., with
loss of time and bad work when starting up again. But unless every part of
the wire is kept wet, or if a draught dries up a space, a ‘tide mark’ will be
formed which is very difficult to clean. A very old custom is to leave the wire
seam over the week-end in the nip of the couch rolls, ‘to keep it flat’, but it
is obvious that it can do no good, but only harm, for the seam to be under
heavy pressure for any length of time. The best place to leave the seam is on
the breast roll.

The second set of factors which influence the life of the wire are, generally
speaking, constant and unavoidable, though some may be minimised if proper
precautions are taken. One of the worst enemies of the wire is the necessity
of using hard water, which forms deposits of calcium carbonate. The latter,
however, and the general clogging up of the mesh of the wire by loading, size,
etc., are to a very great extent preventable and depend on several things, which
will be touched on later.

As far as the machineman is concerned, it will be found that if he adjusts
his back-water system carefully he will use the same water over and over
again, with very little addition of fresh water, which causes the deposits. Except
where special treatment of whitewater is carried out, fresh water must of
necessity be used in the sprays of the wire rolls, so that after a period the wire
clogs up and must be cleaned. A steam force jet, judiciously used—say once
a week—will help to lengthen this period, but there are now special cleaning
agents on the market which clean the wires with less damage than sulphuric
add.

Hydrochloric acid may be used to clean the wire of limy deposits. A
50 per cent solution from an earthenware or glass bottle should be applied to
the top of the wire with an old scrubbing brush, and washed out with the force
jet before the solution reaches the couch roll.

Then there is the wear of the wire by the rolls and tops of the suction boxes.
As for as the rolls are concerned, they should be kept well lubricated, and
especially the tube rolls which form the table. Also, any side play on their
spindles or brasses must be watched for, as in this case the action of the shake
will make the wear much greater. The weight of the breast roll is important.
Very often it is made too heavy, thus imposing an unnecessary strain on the
wire in pulling it round, and more so when starting up. Deckle straps, where
there are many changes of sorts, make the wire dirty and cause more or less
ridging; so also do the movable ends of the suction boxes, owing to there being
a pull over their inner edges. The shake has a twisting action on the wire

RUNNING THE WIRE

177

(list before it is held by the suction boxes. Dandy rolls that are too short and
have prominent discs on their ends are a source of trouble. Cracks on the
edges of the wire are often caused by the ‘spades’ of the guide roll stick.

Setting and Running the Wire .—After a new wire has been put on, and all

fittings have been replaced, it is necessary to tension and ‘set’ the wire, so
that it will answer to the guide (Figs. 62 and 63), keep in the centre of the
machine, and make an equally couched and uniform sheet. With the stretch
roll swinging freely and the top couch roll with equal weight on both sides, the
new wire should run for a few minutes and be worked by hand guidance to the

\Jmtts Bertram end Sorts Ltd.
Fig. 63. —Automatic Wats Gun*

centre of the rolls. The guide-bar spades are then fixed dose to the edges of
the wire. There is no need to leave any space for the wire to move, unless
it has an irregular or a waved edge, when sufficient is left to keep the edges

MODERN PAPER-MAKING

178

from being rubbed and frayed. A few more turns will show whether the
guide roll is set so as to be able to keep the wire in position.

The stretch roll may now be put down a little if it is light and experience
shows that it is necessary. A heavy roll will not require to be put down,
but its spindles should have enough pressure to keep it from jumping. On
starting again, if the seam is fairly straight and the tension from the boxes to
the couch rolls is equal on both, sides, it may be assumed that the wire is correct
for a start-up with paper.

There is, however, a very great difference in the running of a wire without
stuff and with stuff. In the latter case the suction boxes hold the wire, and
the couch rolls have to pull it across them, thus creating a tension which is
very much greater at this point than anywhere else. Therefore the top coucher
has the most important influence on the wire. The slightest difference in the
pressure applied alters the tension between the boxes and the nip. This may
possibly be so much that the wire is extremely tight at one side and so slack at
the other that it is impossible to keep it in the centre of the machine, the guide
roll being unable to send it back to its place.

Then the tension of the stretch roll will be found to be greatest on that
side where the tension from the boxes to the nip is least. It is here that a
machineman may make a mistake by altering the stretch roll in an attempt to
straighten the wire. Instead, weight must be taken off the couch roll on the
side which is slack, between the boxes and the couch roll, until both sides have
the same tension. Then the seam should be carefully watched, and if any
alteration is necessary, the stretch roll may be put down on the side which is
leading. The alteration may change the tension at the nip a little, and both
sides of the wire must be carefully watched until the tension remains the same
and the seam is straight. It will then be found that the wire will keep well
in position and be guided by die ordinary automatic movement of the guide
roll.

If the stretch roll is not quite level, this is immaterial so long as the seam is
straight and the tension is correct, since some wires appear to have a slack side.
This is very difficult to decide, because it is possible for this appearance to be
caused by the inclination of the couch rolls or wear in any of the brasses of
the wire or breast rolls. For this reason it is very much worth while for the
engineers to test these things when the wire is being renewed. In particular,
the back-side brasses of the bottom couch roll tend to have more wear owing
to the pull of the dutch, and perhaps to having less attention paid to them in
regard to deaning and oiling. When this happens the back shaft and the couch
rolls are not in alignment, and the result is an eccentric action in the dutch
which causes a rise and fall of the couchers.

THE WIRE

179

It often happens that a wire will travel slowly to one side of the machine
md cling there, in spite of the guide roll being fully set to bring it into its
dace. This is more inclined to be at the back side than the fore side, because
he guide roll has to turn on the back side as a pivot, and therefore has less
rontrol of the wire at that side. There is very great danger in this situation,
ind a machineman has to be very much on the alert lest the wire turn suddenly
md come over too quickly, doubling up its edges on the guide-bar spades.
3 ut assuming that no further alteration of the guide roll is possible, and the
vire shows an inclination to go too far, then the suction may be partly shut
jff the last box, or the air valve opened a little. Then the wire will return to
ts place with a run, which can be quickly checked by again putting on the full
;uction and squaring up the guide roll. This will seldom take place if the
:ension from die boxes to the nip is properly adjusted, but it must be clearly
inderstood that the coucher must not be used to control the wire.

It may happen that a wire will run very well with the sides at the nip not
equally tight, so long as the paper and suction are on it; but couching will be
inequal, because the tight side has the least weight on it. In this case, if the
machine is shutting down and the wire runs empty for a few turns, the heavier-
weighted side may slacken so much more as to run through the nip in wrinkles,
when the wire is rendered entirely useless.

For this reason it is very inadvisable to run the wire empty for more than a
aim or two to clean it off, unless the machineman is very sure that his coucher
weights are perfecdy adjusted.

The level of the guide roll to the last suction box has a very important
bearing on the steady and trustworthy guiding of the wire. If the guide roll
is too low, the suction box will control the wire in spite of the roll. This is
shown by a wire running to one side and coming back with a dangerous run
whan the suction is eased off. The guide roll may work very far forward to
send the wire back, or vice versa , and this introduces another complication which
makes matters worse. The roll being too far advanced—say at the front side—
and the wire tending to come to that side, the wire is thereby tightened up
between the box and the coucher. This in itself ensures the tendency of the
wire to come forward, since a wire will always run towards the side on which
the wire is tightest, between the box and the couch roll. The guide roll should
in all cases be just so much under the level of the last suction box as not to
interfere with the suction; & inch is quite sufficient. Most of the machine-
man's uncertainty as to the guiding of his wire will be eliminated if this vital
point is amended to.

The Tube Ralls.—The tube rolls have two functions: First, they support
the wire from the breast roll to the suction boxes, and form a table with the

i8o

MODERN PAPER-MAKING

wire on which the stuff and water are evenly spread and formed into paper.
For this purpose they must be accurately levelled from side to side and to
each other, and at even’ renewal of the wire, examined and thoroughly cleaned.
Great care should be taken in replacing them in their proper order. They

are usually numbered for conveni¬
ence. A safe place should be
selected for them to lie until they
are put back.

Although paper machines will
run satisfactorily and make good
paper with stationary tube rolls, it
is usual to have these rolls fitted
with very free-ru nnin g bearings.
If the bearings are ordinary brass,
they should be kept well and
regularly greased or oiled. Ball
bearings are now available which
will withstand the conditions and
keep out water, and they are in
every case to be recommended.

It is important that the tube
rolls should be of a sufficient dia¬
meter to enable the usual speed to
be run, without the throwing of
water from the rolls. In some
cases it is necessary to put doctors
on the tube rolls, or baffle plates,
to catch the water thrown off by
the roll and prevent it being taken
up to the wire again.

Their second function is to draw
water from the sheet. A layer of
water forms on the under side of
. the wire, a tube roll mbs or drains

a partial vacuum in each minute pore of the wire. This mulle¬
ts filk with water and is emptied by the next roll. Thus it will be seen
BBoabcr of tube rolls has a definite relation to the length of the wire.

A short wire, closely tubed, can deal with wet stuff) as far as extraction of
water is cockxxik 4, nearly, if not quite, as well as a longer wire with the gam**
number of tube rolls.

[James Bertram and Sons Ltd.
ftc. < 4 -—Latest Type Shake Motion, with Variable
Spied Motor for Speed Alteration

Hie stroke is altered by the hand wheel

THE SHAKE

181

The Shake .—For the purpose of closing up the fibres into a compact sheet
it is necessary to impart a sideways shake to the wire. This is accomplished by
a crank and shaft driven through cone pulleys so that the speed may be adjusted
to suit the stuff. On old machines the frame of the wire at the breast roll was
supported on rocking standards. The fault of this arrangement was that the
brasses of the crank, etc., had to withstand the shock of changing the direction
of the throw very suddenly and soon wore down and developed a knock.
An excellent shake motion (Fig. 64) is now manufactured by Messrs. James
Bertram and Sons Ltd.; in this the eccentric runs entirely enclosed in an oil
bath, and the wear in consequence is practically nil. This shake motion has
no cone pulleys, as it is driven by a variable speed motor.

On modem machines the frame is hung or supported on flexible steel
hinges or springs, so that the action becomes a soft swing, instead of a hard
jerk. About J to & inch is an average length of throw, but it is a great advan¬
tage to have an arrangement to allow of the length being altered, when running,
to suit different papers. A loose pulley or clutch is necessary to stop the shake
when the wire is not running.

The level or slope of the wire from the breast roll to the suction boxes
depends on the speed of the machine, and in some degree also on the quality
of the paper made.

Machines for high-speed work have the wire frame supported by adjustable
standards, to alter the slope of the wire as the speed is put up. A machine
making newsprint at 1000 feet per minute may require a slope down from the
breast to the suction boxes of as much as 18 inches.

Slow-running machines making strong ledger papers from rags, with a
40-feet wire, may need a rise of 2 inches from the breast to the boxes. A rise
of 1 to if inches on a 40-feet wire making good-class water-marked papers
up to 120 feet per minute would be about right.

CHATTER XHI

THE FOURDRINIER MACHINE (Continued)

Deckle Straps to Machine Drive

Deckle Straps.—These are the endless rubber bands which keep the stuff
on the wire. They are composed of flexible rubber with a core of harder and
stronger material to give them stability. They should be of sufficient weight
and bulk to prevent the stuff from flowing under or pressing them outwards.
They are carried on flanged pulleys, movable outwards or inwards to suit
different widths of web. Often deckle straps are far too big and heavy, and
they cause a strain on the wire, and frequently damage it. A deckle strap
should never be heavier or longer than is absolutely necessary. It is possible
on some machines to manage with deckle straps only about 7 feet between
centres, depending on how the stuff parts with its water. Various means have
been suggested and tried out in order to supersede the rubber deckle strap, but
in our experience these have been very’ unsatisfactory on the whole, and we
are inclined to think that, at the present time, there is nothing available which
will give such general satisfaction as the ordinary rubber deckle strap.

A trickle of water must be continually run on the inside of the straps; other¬
wise they will soon become dry and stick to the pulleys. If this happens a
strap may stop, and this often means a ruined wire, owing to hard rolls of
pulp going through the couch rolls. Bruises or cracks on the edge next the
wire will result in a little ‘leaf being formed on the edge of the paper, with
a corresponding thin place behind it.

This may be picked up by the press rolls and cause a break there or at the
dry end of the machine. If the edges of the strap are rough, uneven, dirty,
or have a hard lump, the same trouble will result. If a strap is too long, the
return portion will swing and sag and cause it to move forward on the wire
with a jerky motion. If too short, or with perished and sticky places, it will
drag ami make rolls of pulp on the deckle edge.

It is important that the side that runs on the wire should be slightly concave,
otherwise there will he a continuous bad edge. It often happens that a strap
is bruised or otherwise damaged when changing a wire. Therefore too great
care cannot he taken to see that they are skilfully handled, placed where there

183

SUCTION BOXES

183

is no probability of their being made greasy, and well away from the work
going on, until they are replaced. If spare straps are kept, and this is a wise
precaution, they must be stored in a cool damp place, and kept in such a posi¬
tion that they have not to take any acute bend or twist, as after a time this will
become permanent and render them useless.

When changing deckles, the pins holding the deckle pulleys may be slacked
off and the pulleys assisted to move in the required direction. If the strap
runs off the pulleys, the wire may be scored and the strap damaged. It must
not be forgotten to tighten up the pins again; they may drop out and be carried
through the couch rolls, with disastrous results.

The deckle pulleys ought to be oiled and wiped clean at every opportunity.
A stiff-ranning pulley will make

and cause a lot
the source is dis-

the strap jerky
of breaks before
covered.

Suction Boxes—Many machines
have only two suction boxes. For
making paper from rag stock, when
we sometimes get very wet stuff,
two boxes are insufficient. In any
case, three or more boxes are better
than two. Even if the paper we
make could be worked with two,
it is wiser to have a little suction
on each of three or four than a
strong suction on two, for then less
pressure is put on the wire, which
lengthens its period of use.

The usual type consists of an air-tight, oblong box (Fig. 65), very solidly
built of some hard, durable wood or brass. It is divided down the centre by
an open frame, which supports one or more bars according to its width. The
top edges and the bars are covered with very hard wood to take the wear of
the wire. The ban are usually about 1$ inches apart and should not be more,
or the wire will be drawn down and over their edges. At the ends where the
edges of the wire travel, brass plates a few inches in length are let in to take
the wear of the rough edges. A pipe from the suction pump is connected to
the centre of the box at die bottom or the side. Movable ends are provided
to enable various widths of deckle to be followed. These are adjusted by a
heavy brass screw extending through the outer end of the box. The box is
made as rigid as possible, and is bolted and very firmly wedged in

Fig. 65.—Suction Box Plan and Section

MODERN PAPER-MAKING

184

the frame of the machine. Each box has a valve to regulate the suction
admitted by the pipe, and a small pipe comes from the centre of the box to the
fore side and is used as a fine adjustment for admitting air to the box. The
space between the movable and fixed ends is kept full of water to prevent air
leakage, and sometimes the suction may be kept more steady by, in addition,
a packing of soft doctor broke.

There is another type of box, used chiefly on 'news’ machines, which has
one solid board forming the top. This board is drilled with holes or slits en
echelon, and has movable ends of expanding rubber.

The ideal method of operating suction boxes is to have a separate p ump

[James Atherton (Sycamore) Ltd.

Fig. 66. New Type ‘Vulture’ Vacuum Box Tops, with ‘End On’ Grain for Long Wear
The top is in sections which can be easily fitted

for each suction box. This is especially the case where other results besides
the removal of water are required.

"Where a dandy roll is used, it is absolutely essential that there should be
, a very fine control of the suction box immediately in front of the dandy.
This is necessary even with a plain roll when it is important to get a fine, clear-
fooking sheet, but it is more important still when water-mark designs have
to be put into the paper. The usual method is to have one suction pump for
all the boxes, up to even five or six, and to rely on regulating the vacuum on
or two of the boxes, in order to control the sheet This is not satisfactory,
.because foe moment the vacuum is altered on one box it is automatically
altered on all the others. 7

TOie suction pomp attached to vacuum boxes has to deal not only
with air passing through the sheet, but also with a large quantity of

SUCTION BOXES 185

water, and up till recently very little attention seems to have been paid to
this point.

There is a tendency, however, nowadays for a large suction pump to be
employed with a large receiver between the boxes and the pump. The bottom
of this receiver has a drain-pipe leading to a water pump which draws the
water away from the receiver as it enters from the boxes, and leaves the air
pump to deal only with air, which is drawn out from the top of the receiver.
By adopting this method a much more satisfactory vacuum is obtainable, and
when the vacuum is altered on any one box it does not affect the others as
readilv.

Fig. 67.—' Various Types op Sections of Suction Box Tops

There is also another method in which barometric legs or syphon pipes
are used in the system for the withdrawing of water.

We are still of the opinion that to have infinite control over the sheet when
making fine papers, a separate vacuum pump to each box is desirable. The chief
difficulty, however, is to get a sufficiently small pump, which is so constructed
that it will stand up to the long hours of usage necessary on a paper machine,
and deal equally effectively with air and water.

Some machines still have steam ejectors on their vacuum boxes in place of
air pumps, and these give excellent results, but they are extravagant in steam,
and they are sometimes blamed for being responsible for making pin-holes in •
the paper. The least cosdy arrangement is to employ a barometric leg, and
where the machine is built on the first floor and has a deep basement, it seems
that there should be no difficulty in adopting this method, especially as the

MODERN PAPER-MAKING

186

vacuum required on a suction box is never very high, and where there are long
runs on the same furnish with the same amount of water.

When a wire is being changed, all the boxes should be cleaned, examined
and tested for loose or worn bars or protruding ends, and if necessary these
should be carefully planed level, or changed by a man experienced at this
work. All bars with hard, soft or damaged places, or with knots, should be
discarded, as they will make ridges in the wire and cause loss of suction.

To obtain efficient and steady suction, the boxes must be carefully levelled
to each other and to the last tube roll. The guide roll should be slighdy lower
than the last box, little more than the thickness of the wire; the latter will not
then be dragged hard over the edge of the last box and the guide roll will have

'Fig 68.—The ‘Aquair* Vacuum Pump for Suction Boxes and Couch Rous
This pump is specially designed to deal with air and water

a good grip of the wire and have more control over it. Sufficient space is left
after the first box to run the dandy roll; all succeeding boxes should then be
as close together as possible.

The first box is the most important. It is often said: The first box makes
the paper. While this is far from being correct, there is no doubt that the
appearance of the sheet is mosdy controlled by the regulation of the suction
on this box. Too much suction gives a cloudy-looking paper, too litde a
crushed or greasy appearance; in the first case, the water mark will be faint
or absent altogether; in the second, it will be very muddled.

Apart from the first box, which has this special function, the other Boxes
should have the suction divided between them as far as possible, though in
practice it will be found generally that one will stand more than the other.

If one box is being overworked, it will commence to vibrate with a hum-

SUCTION BOXES

187

ming or howling noise. This has the effect of upsetting all the others, as the
vibration will have the same effect as putting very excessive shake on the wire,
and the stuff will ‘flood’ into the couch. The boxes, after the first, should be
very close together, so as to keep up a continuous pull on the web, one box
taking it up the instant the other leaves off, and leaving little space or time for
the water to rise again to the surface of the sheet.

It is often advised in making certain papers: ‘Do not use too much suction.’
But no one can use too much suction without causing the wire and boxes to
vibrate. If the machine is making paper with the boxes not drawing up to
their ‘maximum’, it means the machine is running too slow, unless held back
by lack of drying power or other causes. It should be put up in speed so as
to be able to make the paper, and no more, with all possible suction in use.
Of course, wear on the wire is increased, but so is production , and a paper-mill
is not run to keep a wire on the machine for a long time, but to get the greatest
possible output of paper in the shortest time, and of the best quality. With
regard to the latter, the drier the stuff can be made before it goes to the couch
the more bulky and less wire-marked it will be. The couch-roll jackets and
felts will last longer and the felts will not get dirty so soon. There will be
fewer breaks at the presses and the whole work of the machine will be made
easier. Therefore in all cases work your suction boxes, after the first, to the
utmost limit of their capacity without vibrating them. Very often a good
water-mark is crushed and made dull by the stuff being too moist when going
into the couch rolls.

While dealing with suction boxes it should be mentioned that when a
suction couch is in use, it is possible, and indeed often desirable, to leave much
more water in the sheet after the last suction box than would be possible when
a top couch roll is in use. The reason for this, of course, is that with a top
couch roll, if too much water is left in the sheet, there is a risk of crushing at
the couch. With a suction roll this trouble does not arise, and the excess water
is removed satisfactorily by the vacuum of the suction couch roll.

Couch Rolls and Jackets ,—The bottom couch roll is driven by the gearing
and pulls the wire round. The top couch roll gives the first pressure which
squeezes the pulp into the first semblance of a sheet of paper. The bottom
roll is strongly built with a brass shell well stiffened with spokes and ribs. The
top roll is greater in diameter and may have a brass shell or may be built of
mahogany. Both rolls are, or ought to be, slightly crowned to work a certain
weight at the spindle ends. Couch rolls are not set right on top of each other;
the top roll sits well into the wire, for the reason that pressure of the wire
against the circumference of the roll starts the pressure which culminates in
the hard nip between the two rolls.

188

MODERN PAPER-MAKING

Though no water can be seen to be squeezed out until the nip is reached,
there is no doubt that the pulp comes under the pressure sufficient to give it
a certain stability and allow more weight to be put on the top couch roll.
Most modem machines carry the top roll on swinging brackets, and levers
for additional weights are attached to these. This is quite a mistake. More
efficient couching can be obtained by putting the connections for the levers
on the spindle itself so as to bring the line of pressure through the centres of
both rolls as nearly as possible. Many ‘machines do not use a cover on the
bottom roll. This may not matter for cheap papers, where wire-marking is
not considered of much consequence, but it is false economy where fine papers
are concerned. A cover prevents crashing, gives more bulk and a closer under
side, and does not obliterate the water-mark to the same extent as a bare roll
does. This is accounted for by the increased pressure surface owing to the
‘give’ of the woollen cover.

When putting on a new cover, the roll should be thoroughly cleaned with
hot water and the perforated holes in the shell cleaned out. If the water has
been hot enough the roll will soon dry, or it may be wiped dry with a clean
rag. The end over which the cover has to be drawn requires special atten¬
tion, lest any bit of stuff or grease or chip of wood from the wooden end be
pulled in and thus make a lump inside it. The cover should be temporarily
fixed at the front side. It must then be pulled tight to the back side and per¬
manently fixed there. The front side is then loosened and also pulled tight
and permanently fixed. Whether it is tacked on to the wooden ends or roped
on, it should be free to travel round the roll. Boiling water is necessary for
the proper shrinkage of a new jacket, and quantity should not be stinted. If
the cover has a nap—though this is not a necessity for a bottom roll—it should
be in the running direction of the wire, so that the drag of the latter smooths
out the fibres instead of ru fflin g them up. Sometimes a cover is tight and
difficult to pull over the roll. Powdered starch or dry china clay well rubbed
over the roll will help to make it slip on more easily. But if this happens
often the manufacturer should be notified and will be able to correct the size.
After the cover has been shrunk, it is very necessary to go all over it carefully
wiih the fingers lest there should be any hard knot in the wool or any substance
wdemcath. Hard knots and wood splinters are not uncommon in covers
and should be picked out with a sharp-pointed knife. Neglect of this precau¬
tion me a ns a ridged wire in the space of an hour’s work. This applies to both
coother covers.

assist the starting of a new top jacket if the nap is gently
crashed the naming way, more especially' on the two places where the jacket
has been folded, and which have a tendency to stand up. If the covers are

COUCH JACKETS 189

tacked on to the wooden ends, the latter must be perforated to allow the escape
of the water coming through the perforations of the shell, and holes corre¬
spondingly punched in the covers. If roped on, the water will find its way
through the open folds between the stitches. It sometimes happens that a
cover works over one end of the roll. This may be owing to weight being
applied unequally on the levers, insufficient shrinkage, or to the cover not
having been pulled tight from side to side. If correcting the weights does not
send it back again, the best remedy is to loosen the tacks and refix, or put
in a fresh rope, tighten up and apply hot water to the rope. Rope for this
purpose can be obtained which tightens up and remains tight with the applica¬
tion of moisture, and roping is the quickest and safest method of fixing. When
first put on, the coloured line of the cover will be approximately correct across
the roll, but later on will show a bend in the centre. This is to be expected
from the slight crown of the roll and die fact that the wire is tightest in the
centre. But if one side should take the lead a litde there is no cause for alarm.
It may be that the guard board is not so hard down, or so well fixed, or the
inclination of the couch rolls may not be exactly correct at both sides. The
roll may be more smooth at one side than the other, or the weights unequally
adjusted. If all arrangements are fairly accurate, the difference in the line will
be very slight, and will only go a short distance and may be discounted. But
if the line continues to go farther off the straight, the machineman may be
sure that some one or more of his adjustments are seriously wrong, or the
inclination of the two rolls requires skilled attention and correction from the
engineer.

In starting up with a new top jacket, unless the stuff is very ‘free’ and
can be well dried at the suction boxes, it will be found that the new nap picks
up fibres from the sheet. These accumulate until a small, flat patch of pulp
is formed, and a new jacket may be covered all over with these patches in a
few minutes.

The best remedy is to have the guard board well adjusted and hard down
at the start. (It should be eased off again as soon as the jacket has become
‘seasoned’.) The suction should be used to the utmost and as little weight
as possible put on the roll. If the cover is run for a few minutes before starting
up, with a hot mixture of resin size and china clay in the water channel of the
guard board, there will be less trouble of this sort. Where it is possible, warm
water, in place of cold, should be used in the water channel to dean off the
patches of fibres.

In any case, it is best to start up with a new jacket at a speed slow eaougjb
to have a good control of the stuff at the suction boxes, and the wire as tight
as safety permits.

MODERN PAPER-MAKING

190

Many machinemen prefer to run an hour or two with no water on the
cover until it fills up to a working condition.

At all times it is inadvisable to rub the hair or nap of the jacket the wrong
way if the stuff shows signs of going up the roll. Only a momentary improve¬
ment is obtained. A hot and strong solution of soda ash is far more effective,
and this should be used when the cover requires cleaning, instead of using
the force jet. As one of the chief causes of wear in a cover is the plucking
out of the nap by the meshes of the bare wire, the new cover should, if possible,
be started with a full-w T idth deckle and fall widths should also be run as long
as can be arranged.

The Guard Board .—The function of the guard board is to clean and dry, as
far as possible, the cover of the couch roll. As pressure is the integral part of
this action, it will be readily recognised that its use will be the chief factor in
shortening the life of the cover. For this reason various kinds of appliances
have been tried, and many ways of fixing, pressing and covering the rubbing
edge of the board have been resorted to. We will not go into details of these,
or the special designs applied to high-speed machines, but confine ourselves to
the types that are commonly used for machines in general. A guard board is
usually constructed from one piece of good wood (pitch pine), strengthened
and made rigid by another piece at right angles, fixed at the back of the board;
or in some cases this is replaced by a rod of iron used as a ‘stringer’. It is covered
on the rubbing edge by a piece of old couch cover, and there are two ways
of fixing and using it. It may be fixed to the brackets which hold the couch
roll, sliding in a guide, and being pressed down by springs; sometimes there
are no springs, and the board is pressed down by hand and fixed in position by
bolts. If the brackets are of the modem type which swing with the couch roll,
the board will of course rise and fall with the roll; but if the brackets are of the
older fixed type, the roll is apt to lift the board and let water pass.

A board of this kind must be very carefully used. The machine man is
sometimes tempted, when running very wet or fine stuff, to squeeze it very
hard down on the cover, when he may very easily reduce the life of the latter
by half. A safer and more efficient type is the swinging board. This is hung
on pivots on the brackets and the pressure is applied by weights hung on short
fixttl fevers on the back of the board. Being free to rise and fall, it does not
require to be so heavily pressed on the roll, and the pressure is more easily
controlled and observed. This kind, owing to the angle at which it touches
the roll, has the advantage of allowing a deeper flow of water to he used to
dean the cover, and therefore washes away any fragments of fibre that may
come up the roll. A fixed hoard requires to be set opposite the point of pressure
of the coochers, ami the angle admits of a very shallow flow.

COUCH ROLLS

191

The board may be used without a cover, but though the wear of the jacket
is less and the joint is more water-tight, the jacket fills up with size, loading
and fine fibres, and requires frequent cleaning and blowing with the force jet.
The efficiency of the couch roll is greatly reduced, and any saving in covers
is nullified by the waste of time and extra ‘broke’. The flow of water is

[Rjfcrt Fletcher mtd Son Ltd.

Fig. $9.—Suction Couch Ron wobkxng on a Machine making ftus Tissues at High Spsbd

supplied by a spray-pipe close to the guard board, but the spray must not play
on the couch-roll cover, or it will raise the nap and the fibres will be pulled
off by the board. A frequent cause of damage to the cover is that, when
shutting down or starting the machine, bits of pulp or foreign matter stick
to the roll, and become jammed in the board, cutting or scoring the covet in

I92 MODERN PAPER-MAKING

3. few turns, or, passing the board in hard rolls, spoil the wire. Brushes or
strips of old jacket are sometimes fixed in front of the guard board to loosen

these and allow the water to wash them away.

A very good combination is a swinging board and a rubber-covered squeeze
roll just after the couch roll clears the board. Then the board may be used as
a light cleaning agent and the roll will take the water out of the cover before
it touches the paper, far more effectively than a board can. With this arrange¬
ment higher speeds and more output can be obtained, without the necessity
of increasing couch-roll weight.

OF gocnriOM

Fig. 70.—-Millspaugh Suction Roil, showing Springs for holding Box up to Shell and

Adjusting Screws

Suction Couch Rolls— The suction couch roll (Fig. 69) has now almost super¬
seded the couch press, and although some people still use the press method
of couching, it seems that the suction roll will soon be universally employed.

The suction roll has many advantages over the plain couch, the chief of
which is that there is no top roll and no jacket. The eliminating of jackets
saws a great deal of time, and a great deal of spoilt paper, because jackets always
gave some trouble when starting up new, and further trouble when becoming
worn. The eh miration of the top roll has entirely done away with crushing
of wet stuff, and the damage done to the wire by the pressure of the nip, due
to bumps of stuff or foreign matter, has entirely disappeared.

PRESSES

193

The guiding of the wire is much simpler and, in fact, presents practically
no difficulty with a suction roll, and the danger of running the wire out of
square, due to uneven weights on opposite sides of the couch press, does not
arise when a suction roll is used. Much longer life is generally obtained from
the machine wires, and in most cases a drier sheet is delivered on to the wet
felt, which latter in turn naturally has a longer life, by reason of the fact that it
has not so much water to deal with.

There are now several very satisfactory suction couch rolls available, and
experience seems to show that they will run for many years without any atten¬
tion whatsoever. While some of these rolls consume a fair amount of power
through their vacuum pumps, very efficient pumps are now available, and the
power consumed is nothing when compared to the efficiency of the roll and

[Wahnsirys (Bury) Ltd.

Fig. 71.—The Press Part of a Modern Machine: Plain Press Rolls

its many advantages in the saving of time and the maintaining of production
at a high level.

Presses.—After passing through the couch rolls, though the sheet is now,
for the first time, in condition to be handled, it must be further pressed, so as
to be so far freed from water as to stand the heat of the dryers.

This is accomplished by running it on woollen felts between ‘press rolls’.
Two sets of press rolls and felts are used, though machines designed for high
speed or for making special papers may have three or four. Since pressure
means loss of bulk, it is not desirable for machines making high-dass paper or
bulky printings to have more than two sets. The first set of press rolls and
the ‘wet felt’, as it is called, do the bulk of the work. The second set is so arranged
as to smooth out the wire mark.

Underneath the bottom roll is placed an oblong box or tray to catch and

MODERN PAPER-MAKING

194

lead away the water squeezed from the web. The bottom roll is driven and
the pressure of the two rolls pulls the felt round. Before the felt and paper
enter the nip there are often air pockets between them. A small suction box
with perforated holes on the top is arranged at this point and extracts the air
so that no wrinkles are formed in the paper. Sometimes, a roll of 2 to 3 inches
diameter, called a ‘blow roll’, is used to raise the paper from the felt and allow
the air to escape.

Of late years, press rolls of granite have become popular. The cold, crystal¬
line surface does not pick up ‘greasy’ or fine stuff as easily as the brass shell

1695

<1. -HL. -ffV xjL

[Miner

k Fig. 7 1 .—W eil-arranged Presses on a Machine for making Fine Tissues

does. For this reason they are valuable for use with esparto, straw, and mechani¬
cal fibres, which have very little strength or length to carry them over the
machine. They are usually run with non-metal doctors to obviate ‘pencilling’.

The top press roll may be made of iron, brass, granite, or wood. The
bottom roll is usually rubber-covered. Sometimes two brass rolls are met
with, hut these are very destructive to felts, since a small lump passing through
will cause the felt to be damaged. The rubber covering of the bottom roll
lessens this danger considerably. With a rubber-covered roll there is a less
severe nip of the felt and paper, but even so quite satisfactory removal
of water is effected and longer life obtained from the wet felts. The

SUCTION PRESSES

195

top press roll is fitted with a doctor, either iron or composition, the
purpose of which is to clean the roll and also to hold up the stuff which
may stick to the roll, and prevent the sheet from go ing round if a
break occurs.

Suction Presses (Fig. 73).—The tendency is nowadays for the ordinary press
to give way to the suction press. This press consists of a bottom roll containing
a suction box and perforated shell, which is the same as the suction couch roll,
with the exception that it is usual for this suction roll to be rubber covered
over the bronze shell. Where suction presses are used, it is not generally found

Fig. 73.— Kwm-cormso Suction Press Rolls [Mitbpmigk

necessary to have such a heavy top roll, or to use such pressure, as was often
found necessary with the ordinary press. Some paper-makers maintain that
if they had the option of having a suction couch or a suction press, they would
prefer the suction press. The reason for this is that all felt troubles are prac¬
tically eliminated, very much longer life is obtained from the wet felts, very
even drying of the paper results, and a much more uniform sheet is obtained.
It is usual to have 14 to 24 inches of vacuum in the suction roll, and the hard¬
ness of the rubber used varies between 30 P-J. and 50 P-J., the first being
comparatively hard, and the second much softer.

196

MODERN PAPER-MAKING

The Dual Press (Figs. 74 and 75), which is now being taken up in this country,
has actually been in use for some years in America.

It consists of three press rolls, two of which may be suction rolls, with a
plain roll in between, as clearly shown in the photograph and drawing.

There is a great saving in space with this arrangement, but there are also
many other advantages claimed by those who are using this design.

The pressure is applied laterally by levers, instead of vertically, and much
greater felt life is being obtained.

[Wdmsleys

ft®* 74-—Dual PttESS ARRANGEMENT, SHOWING ONE SUCTION ROLL AND TWO PLAIN
Roils arranged together
The third roll can be arranged for suction if necessary

A doctor blade should be made to move from side to side by traversing
gear; the purpose of this is to prevent pencilling or scoring of the roll by
any particle of grit becoming embedded between the doctor blade and
the roll. The doctor is hung on pivots to enable it to be cleaned and
re fitted ,.

Tlie felts are pure wool fabrics and may be obtained from the makers in
many degrees of fineness and quality. Nevertheless, it is sometimes very
difficult to find a kind that is both efficient and economical to run, owing to

SUCTION PRESSES

197

peculiarities of the machine, the speed, the quality of the stuff and the system
of cleaning, etc. One of the questions that is being continually asked by
paper-makers of each other is: ‘How long do your felts last?’ Conditions
vary so much that the answer may be either ten days or ten weeks. To illustrate
this, suppose we are making a well-fibrillated bank at from 100 to 150 feet
per minute. We will perhaps find that we can have little pressure on the
coucher at, say, 120 feet, and still less at 150 feet. Then the sheet will enter
the press rolls with a higher percentage of water. This is throwing more of

[WthtiSeyi

Rc. 75 .—Sketch showing Usual Amangjement ckf Pmsses (Above) and Dual Pmss (Below)

The saving in space is very considerable

the work of water extraction on to the felt, not only by increased speed, but
in quantity, greater in proportion to the ratio of speed. In addition, the in¬
creased speed reduces the efficiency of the rolls and felt. The forward impetus
of the water carries it through the rolls in greater quantity. The time factor
of the nip is reduced. The water flowing through the felt and running
down the bottom roll has less time to get away and remains nearer the
nip. The porosity of the felt, though actually unaltered, is less able to
allow of the extra water getting through. The pressure of the nip must,
if possible, be increased to keep the paper relatively as dry as at the lower
speed.

198

MODERN PAPER-MAKING

Consequently, the felt will get ‘dirty’ in a shorter time and require more
drastic cleaning. In this case we must reckon the life of the felt on the quantity
of water extracted as well as on the weight of paper made and the time ran.
Conversely, with free beaten stuff and a heavier substance that can be well
couched, we may easily make ten times the weight of paper without being
checked by felt-crushing. Then there is the question of felt-cleaning. The
simplest plan is to run a felt until it gets dirty and replace it with a clean one.
The felt is then washed on a felt-washer and put back again in turn. The chief
objection to this system is the waste of time changing felts. Another plan is

Be. 76 .—Vickeby Felt Coneitionek with Two Shoe [Vickery s

to shut the machine and clean the felt without taking it off. This also is time-
wasting and really only saves labour in changing felts, since this latter operation
could be done almost as quickly as washing on the machine.

Felt-washers operating on the machine as the paper is being made offer a
solution of the problem, but are open to the objection that the continual washing
wears out the felt as much or more than the legitimate work does. The
usual felt-washing apparatus on the machine consists of a series of sprays
impinging on both sides of the felt, a pair of rubber-covered rolls to press
out the dirty water, and a small suction box to dry the felt again ready for
the paper.

Ttie Vickery felt conditioner (Fig. 76) is the best attempt to solve the felt
wadung problem, and is now in general use. It may be made very drastic in
its action and requires skilful and careful manipulation, since, of course, any

FELT CONDITIONERS 199

means of raising the nap and cleaning it by suction is bound to be more or
less destructive.

The Vickery Adjustable Friction Type Felt Conditioner.—This is an improved
type which has recently been introduced, and whereas in the case of the
standard conditioning unit the felt is drawn across the fixed top of the box,
so creating friction and consequent wear, in the case of the adjustable
friction type the box is divided into three suction chambers, the first and
last of which are operated at a very low vacuum, while the centre chamber
is operated at a higher vacuum.

Fig. 77.—Felt Conditioner designed for Mould and Board Machines

Friction between the felt and the conditioning unit is reduced to the
minimum necessary for efficient conditioning by means of revolving members
in the box itself, and travelling bands at each edge which carry the felt across
the face of the box.

Further, there are means for adjusting the degree of scraping action on
the free of the felt.

Some installations which have already been made show a remarkable
increase of efficiency and an increased felt life averaging up to as much as
50 per cent

The suction roll is now quite commonly used as a wet-felt cleaning device.
Usually it is made smaller in diameter than the suction press roll. To get

200

MODERN PAPER-MAKING

the best results the wet felt should be carried well round the roll, and there
should be a strong spray of clean water directed on to the felt immediately
before it goes to the roll. A very high vacuum is required in order to dry
the felt sufficiently to enable it to take up moisture from the paper when it
returns to the press. The chief advantage of this type of cleaner over the
travelling type is that it leaves the felt in the same condition right across the
machine.

The Evans Rota Belt type of suction box (Figs. 78 and 79) was originally
introduced to take the place of the fixed-top suction boxes under marbinp
wires, but it did not meet with very great success in the early days.

It was then developed for use under wet felts, in which position it has
thoroughly justified itself and become firmly established as an excellent means

[ W. P, Evans and Son Ltd.

Fig. 78.—The Evans Rota Belt, with Three Suction Boxes,

FITTED BENEATH A WET FeLT

of drying the wet felt, preventing blowing, and generally improving the per¬
formance of the press rolls, besides increasing considerably the life of the wet
felt.

It has been considerably improved lately, and is now being used with success
in place of the fixed-top suction boxes under the machine wire.

It consists of suction boxes, usually in sets of three, each of which can be
individually controlled. Over these a grooved and perforated endless rubber
belt passes, driven through friction with the under side of the wire.

Tne vacuum in the boxes draws water through the belt, and delivers
it to the backwater system in exactly the same way as the ordinary
suction box.

FELT CONDITIONERS

201

The chief difference between an ordinary suction box and an Evans Rota
Belt lies in the fact that the wire, instead of having to be dragged over hard
wooden or metal box tops, passes over the soft rubber band, which is moving
at the same speed, and therefore there is a tremendous saving in the friction
and consequent wear on the under side of the wire.

The advantages of this will be quite obvious, and it is this saving in
friction which was the chief reason for the introduction of the belt in the
first place.

It seems that this belt will now stand up well to the severe conditions of
modem paper machines, and that it may soon have universal application both
on felts and wires.

When passing through the first press, the paper, being very moist, takes
the impression of the cross-meshes of the felt fabric. In Drawing Cartridge
this is called the ‘tooth’ and is a distinctive feature required and expected by
artists and draughtsmen. Coarse mesh felts, specially made for the production
of various varieties of tooth, may be obtained from felt-makers, and this paper
is made in imitation of ‘hand-made drawing’. For ‘fine’ papers, such as
writings, banks, ledgers, etc., and body paper for coating and printing, the felt:
marking is very undesirable, as it prevents a dose finish being obtained. Use

202

MODERN PAPER-MAKING

second press is designed chiefly for eliminating felt and wire marks. For this
reason the rolls run in the reverse direction to the first press, and the paper is
reversed, so that the under side, which is impressed, by the wire and felt, is
made to come in contact with the top roll of the second press. This has the
effect of greatly reducing this fault, and as the second press is seldom pressed
hard, the paper is made more equal-sided for the reception of finish.

Second press felts are seldom washed as they run, but are kept in condition
by washing with the force jet at every opportunity, or changed for washing
on the felt washer. Although the second press does not often cause crushing
when the felt is dirty to the same extent as the first press, the felt must be kept
in very good condition. When it becomes the least bit clogged up, it affects
the drying of the paper, and is one of the chief causes of ‘cockles* and other
drying troubles.

When a new felt is put on a machine it requires to be thoroughly wetted
with cold water, in order to shrink it to its running tension. If this is not done,
it will begin to tighten up soon after the wet paper is run over it.

The tension has to be regulated to give the greatest porosity to the felt
If it is too tight it may run into wrinkles, and be less porous owing to the
meshes being pulled together. If too slack the meshes will not be opened up
and the felt will very quickly become dirty. The coloured line or lines must
be kept straight across the machine for the same reason, and the nap should
be in the running direction, both on the machine and on the felt washer. All
rolls require to be true and perfecdy parallel, as a felt is very difficult to run
if any one is not correct. Spiral felt rolls help to keep the felt free from wrinkles
and the meshes open.

Although it is very desirable to run felts as long as possible, it should always
be borne in mind that it is for cheaper to dry paper by the press rolls anfi felts
than by steam in the drying cylinders.

Apart from the loss through breaks and bruised sheets, caused by trying to
get an additional week or two out of a worn felt, the addition to the coal bill
will be very great, but this is unfortunately very often lost sight of, or it may
even be entirely overlooked. The use of felt rolls covered with vulcanite is
reco mm e nd ed, as the surface of the vulcanite is ‘kind* to the felt, and gives
it a ktiger life.

The Drymg Cylinders (Fig. 80).—Having pressed as much water out of the
sheet as posable, there is still anything from 64 to 72 per cent of water to get
rid o£ (See Appendix.} This is accomplished by running the paper over
steam-heated cyhnders, on to which it is pressed by dry felts. The cylinders
ate of cast iron with highly polished surfaces and may be from 3 feet (on old
machines) to 6 feet in diameter. Steam is admitted to the cylinders by various

DRYING CYLINDERS

203

types of pipes and glands. The most modem comprises the inlet pipe and the
condensed steam pipe, or outlet pipe, arranged to enter the cylinder together
through the hollow journal at the back side, so as to avoid having a pipe at
the front side. This gives more freedom in leading the paper through and in
putting on new felts. Formerly the inlet pipe entered at the front side and the
outlet pipe at the back.

Inside the cylinder it is necessary to have some arrangement for getting
rid of the water formed by the condensation of the steam. This takes the

[SiMfltf Sdmkcrt

Fig. 80.—Arrangement op Drying Cylinders on a M a chins maxing Fine Papers
Each cylinder is driven by a separate motor

form of a bucket or chute attached to the end of the cylinder, which scoops
up the water and raises it to the centre level, when it runs away through the
oudet pipe. A syphon pipe is often used, the outlet pipe being carried to the
bottom of the cylinder.

The pressure of the steam forces the water up and out. In the case of
cylinders 5 feet in diameter, at a speed of 490 feet per minute, centrifugal force
carries the water round the cylinder wall, and both these types become inopera¬
tive. Each cylinder should have a separate steam trap, to prevent loss of
steam by the steam blowing straight out through die oudet pipe. The
simplest steam trap is similar to a water astern. A floating ball opens

204

MODERN PAPER-MAKING

closes a valve in accordance with the quantity of water coming through the
pipe. A great many varieties of steam traps have been put into use of late
years, but they all work on much the same principle, and, unless kept in good
order and regularly cleaned out, are more often than not steam wasters.

Steam and water nozzles without packing are now in general use. The
principal feature of these nozzles is the total absence of packing, all the joints
being carefully machined, and there is an ingenious system of lubrication by
which these joints are kept covered with a thin film of oil, which reduces the
friction to a minimum and keeps them both steam- and water-tight.

There are special patterns for drying cylinders, machine and supercalenders,

M.G. cylinders and boilers,
and they are made for func¬
tioning with either water
lifters or syphons.

On a machine where the
cylinders are few and con¬
stantly in use, the outlet pipes
may all be connected to one
large pipe and one
trap. But the objection to
this is that the steam blows
back and overheats those
cylinders that are not re¬
quired to be very hot, as it is
not advisable to have stop
valves on the outlet pipes.

Steam Circulation Plants.—
The old method of trapping
the steam from each cylinder
or section of cylinders has now
almost entirely given way to a
new method of steam circulation. There are two plants in use, the V.J.B.
steam circulation system and the Holmes and Kingcome. The principle of the
V.J.B. is that it injects steam into the cylinder, traps that steam when it leaves
the cylinder, separates it from the water, and reinjects the uncondensed steam
again into the cylinder, thus ensuring that all the latent heat of the steam is
made use of in heating the cylinder, and until condensed water passes away
through the trap to be returned to the hot well.

Very large savings in coal have been effected in many mills by the introduction
of this system, together with vastly improved drying on the paper machines.

long steam

Fig. 8i.—Diagram of Steam in the Drying Cylinder,
and Condensate Collecting Trough

DRYING SYSTEMS

, ‘ 205

t ,

The British V.J.B. Three-Stage Steam Circulation Heating System .^The
simple method of heating cylinders by blowing in steam, and afthr it.
has passed on some of its heat, exhausting the condensed steam through
a steam trap, has two disadvantages: First, rather a long time is required in
w T hich to drive out the cold air from the cylinder to be heated; and, second,
there is much inevitable wastage of steam through the trap. The original
V.J.B. circulation system was designed to eliminate these faults. Pro¬
vision of sufficient cocks in the system and skilful design of piping enabled
the air to be rapidly released from the cylinder to be heated, but the main
feature of the system lay in economy of steam consumption. This was effected

\^//// // /^ Ac?-rarjSvPiv 5 rfr-re-. r g*- 1 7? '.srr.f

( VA

Fig. 82.—Patent Steam Iniet and Wats* Outlet Nozzle for Cyundq and Caiendess

This nozzle remains perfectly steam- and water-tight at all pressures up to 260 lb. per square inch and is suitable for cither
syphon or bucket condensate ejection and for (he straight in feed on calender rolls. It is also made in single form
where the steam is fed in at one end and (he water ejected at the other

by separation of steam from the exhaust from the cylinder, and the continued
use of this steam until it had parted with all its available heat. Direct steam
was not blown straight into the cylinder, but was passed through an ejector,
which drew the exhaust steam from the trap, so using a mixture of fresh and
reduced pressure steam for heating. Steam entering a cylinder was con-
standy being drawn out and put back again, through the ejector, until it had
parted with all its available heat and become condensed. The two essential
features of the system were the steam trap, which incorporated a separation
chamber for the steam, and the ejector, which relied upon steam few its
operation.

206

MODERN PAPER-MAKING

The improved British V.J.B. three-stage steam circulation heating system
retains these two important features in unchanged form, but uses a different
cycle of operation. The extravagant feature of the original system lay in
the fact that the same temperature was attainable on all cylinders, and most
economical ■working was effected only when such conditions obtained. When
the last cylinders were required very hot and the first cylinders only just wanned,
the system suffered by the recirculated steam cooling the direct steam, its
original temperature never being fully utilised in the cylinder. In the latest
British V.J.B. three-stage steam circulation heating system, heating is done
in three separate stages, enabling still greater economy to be effected by the
more complete use of the heat of the steam.

The three stages are: First, the heating stage, which consists of the cylinders
using direct steam, undiluted by steam under reduced pressure, to heat the
cylinders requiring the highest temperature. Second, the mixed stage, con¬
sisting of the cylinders using the exhaust steam from these hottest cylinders
mixed with direct steam. This stage is very important, because, according to
the quality^ of the paper, the cylinders can be heated to any required tem¬
perature, high or low, thereby making the whole system very flexible. The
third or suction stage is divided into two groups: first, the cylinders receiving
a mixture of exhaust steam from the mixed and heating stages; and the
second group, which receives the steam evaporated from die hot condensate
exhausted from the cylinders, and using this ‘flashed’ steam to heat the low-
temperature cylinders.

In the first stage, direct steam is blown in, without the use of an ejector,
to the cylinders required to be worked at the highest temperature, so that
the full temperature of the steam is available. In the second stage, exhaust
steam from one group of the first stage, mixed with direct steam, is used for the
cylinders which are heated with a lower temperature, but which still have to
give a high evaporation of water. The steam exhausted from the first and
second stages after separation from water has sufficient pressure to be used as
the supply for heating the following cylinders with medium or low tempera¬
ture. Its pressure is also sufficient to introduce exhaust steam of reduced
pressure into these cylinders through an ejector. The steam exhausted from
ooe g^oup of cylinders is not put back into the same group of cylinders, but into
one using a lower temperature. The third stage is provided with a small
suction pump, which creates a vacuum sufficient to allow the use of evaporated
steam from the hot condensate of the steam traps. Suction is provided by
means of a pump-operated aspirator and assisted by a cooling coil. The
coolest working cylinders are virtually under suction sufficient to enable the
vac of evaporated steam from the condensate, and utilise dm steam as the

208

MODERN PAPER-MAKING

source of heat. The cooling coil in the aspirator assists the suction pump by-
condensing all steam and so avoiding back pressure.

Thus the system may be said to work on the counter-current principle.
The ingenious feature is that the cylinders are each arranged to work under
a graded scale of temperature, and steam horn one cylinder is re-used, but
only in a position where the greatest benefit will result from its reduced tem¬
perature. The use of steam evaporated under suction for the heating of the
low-temperatured cylinders is perhaps the most outstanding feature of the
system. The whole of the piping is arranged so as to allow easy release of
entrained air, and there are a sufficient number of cocks for this purpose.

Holmes andKingcome Steaming System (Fig. 84).—This steaming system is based
on the well-known principle of increasing the heat transference through any
heating surface by increasing the velocity of steam applied to the opposite side
of the surface; thus in the case of paper machines, the faster the steam is passed
through the cylinders the more heat is passed through the cylinder walls, con¬
sequently giving increased drying power.

The method used to obtain maximum circulation coupled with economy
of steam is shown in diagram.

The steam is applied to three jets, the bulk passing through No. 1 jet which
feeds all cylinders except the first three. As there are no steam traps or other
restrictions in the piping, the steam passes straight through the cylinders and
exhaust pipes to the flood vessel, where the condensate is separated from the
steam, air and COj escaping to atmosphere from a release valve. The separated
steam is sucked off by No. 1 jet and blown through the cylinders again, and
the condensate is sucked up into the vacuum vessel by No. 2 jet. As water
under vacuum boils at a lower temperature, the condensate boils again in the
vacuum vessel and the steam given off is used to feed the first three cylinders,
the surplus being boosted up to main manifold pressure by No. 3 jet to be used
again.

The resulting condensate left in the vacuum vessel falls down the fall-pipe,
which acts as a barometric leg, and trickles out of the sealing sump. As this
condensate has been under vacuum, its temperature is consequently very low.

Another valuable addition to this system is the use of an internal stationary
steam jet inside the cylinder, which blows steam direct on to the cylinder wall
at fine pressure. By this method a still greater velocity as well as a drier cylinder
is obtained.

All cylinders have to be very carefully balanced. A heavy side will cause a
jerky motion, which makes the paper wrinkle or break. They are also graded

® efimiiTffhmg towards the dry end to allow for the decreasing shrinkage
of the paper.

DRYING SYSTEMS

209

Besides the cylinders over which the web passes, each dry felt has one or
more additional cylinders over which it runs on its return journey, in order

to be dried. This is commonly called the ‘felt dryer. The number of
cylinders required on a machine depends on a great many things—the length
and mesh of the wire, the number of suction boxes, the weight of the couch

210

MODERN PAPER-MAKING

and press rolls, the quality and substance of the paper, the speed, the steam
pressure used for drying, etc. Obviously for a machine making a wide range
of papers it is very diffi cult to suit the number of cylinders to all these con¬
ditions. For some papers eight would be sufficient; for others, five times that
number would be wanted. From ten to twenty cylinders on an ordinary
Fourdrinier is a fair average.

Felt Dryers .—It is at last being realised that the conditioning and proper
drying of dr)' felts is a very important part of paper drying, and quite recently
a very excellent type of felt dryer has been made available. While it has
invariably been the case that certain cylinders have been added for the purpose
of drying felts, something more was wanted, and the Happer dryer is an
excellent solution of this difficulty of keeping dry felts in condition. It con¬
sists of a small drying cylinder rather like a suction roll and it is inserted between
the sections of dryers in the same way as the felt-drying cylinder or in place of
a carrying roll. As the felt passes over it, it is subjected to suction from a
vacuum pump, and this draws the moisture away from the felt surface, and
so dries the felt and leaves it in a condition to take any further moisture from
the paper. This has the double advantage of conditioning the felt and the
atmosphere around the dryers at the same time, for this reason: with the ordinary
felt-drying cylinder the heat of the cylinder drove the moisture from the felt
into the pockets, or under the hood of the dryers, still leaving this moisture to
be dealt with by hot air and fans. In the Happer arrangement the water vapour
is actually sucked away through the felt and exhausted to atmosphere outside
the machine house, an advantage which will be readily appreciated.

Dry Felts .—Dry felts may be of cotton or wool. The latter are most
efficient and last longer, but are more expensive in the first place. Cotton felts
mark the paper and shed cotton fibres on it after a time, and for this reason
may have to be discarded before they are quite worn out. Woollen felts shed
a brown dust towards the end of their life, but by the time this takes place
they are very much burnt and nearly useless. The cylinders should never be
run when the wet end is shut for washing up or changing. After a few turns
to get the felts thoroughly well dried the cylinders should be stopped, and
the felts slackened off a little, to release the strain on their fabric caused by
tbstr shrinkage cm drying. The felt-drying cylinders must have full steam on
when the mac h i n e is running. This is much more important than is generally
itoogaisedL Owing to the blocking up of a steam-pipe leading to the drying
cylinder, a woollen felt that would normally have run for six months became
rotten and went to pieces in a'fortnight. On many machines dry felts are
guided by hand, hut there is no reason why this should be so, as automatic
guides are simple and easy to fit The lines of a dry felt must be kept straight,

DRY FELTS

211

otherwise drying will be uneven, owing to the felt being tighter at one side
than another. In many cases guide rolls will be found in the wrong positions.
To check the felt, the roll has to be altered in such a way as to send the line off
the straight. All fast-running machines now have automatic felt guides.

The guide roll should be on a stretch of felt where altering its parallel does
not materially alter the tension of the felt. It is bad policy to run a felt too
long. A felt may look to be capable of a few weeks’ more work, but it may be,
and usually is, worn thin in the centre, and this makes drying very difficult.

This will be reflected in unequal finish later on, especially on machine-
finished papers, and cockles, etc., on thin papers. Much more steam is required
to dry paper if the felts are well worn.

The satisfactory drying of paper on the Fourdrinier machine and the pre¬
vention of condensation in the machine house constitute two difficulties which
until very recently have been unsurmounted by paper-makers and paper-mill
engineers. The extra output required during recent years, in order to keep
up with competition from new mills, has often been badly handicapped by
lack of sufficient drying power at the machine.

For whereas it has often been found possible to speed up an old machine
mechanically without detriment to the paper, it has usually been found that
there were not sufficient drying cylinders to dry the paper at a great speed,
and, what is more, no room to put in additional cylinders. In one mill at least
this trouble was overcome by adding a third tier of cylinders above the existing
two. To get over this drying problem the present tendency is to introduce
warm air into the machine room and blow it into the ‘dead pockets’ among
the drying cylinders.

Vapour absorption plants are in use in many mills and give very good
results, both in increased output and also in the saving of dry felts. They have
superseded the earlier method of introducing warm air through ducts under
the roof, for while this plan certainly helped very gready in reducing the con¬
densation of water on the roof and girders, it could not be said to add much
to the drying efficiency of the drying cylinders. The system of vapour absorp¬
tion by hot air both increases the drying power of die machine and at the
same time prevents condensation above the machine by absorbing the vapour
as it leaves die paper, thus preventing it from ever reaching the roof in a saturated
condition.

The vapour is chiefly released in the pockets between the drying cylinders,
where \here is very little natural movement of air, and fog or steam can nearly
always he seen hanging about there. With the Sturtevant and similar systems
warm air is introduced into the ‘pockets’ by means of specially d«igngd
perforated pipes. These pipes have perforations which ensure that the air

212

MODERN PAPER-MAKING

is discharged directly on to the felt, or paper, whilst at the same time sur¬
mounting the difficulty of projecting nozzles which interfere with the work of
clearing broke and feeding through.

The air is drawn from outside by a centrifugal fan, and is blown through
a steam heater. The apparatus may be placed in almost any position in the
machine house or even outside it. The heater can be fed entirely by exhaust
steam, or may be divided into sections, one using exhaust steam and the other
live steam.

The warm air from the heater is distributed throughout the length of the
dryer by galvanised sheet steel ducts, which in turn feed the various pipes
distributed into the pockets, or above and below the felts of the machine.
The drying capacity of the machine can be increased 15 to 25 per cent, with
a corresponding increase in possible output. Fog in the machine room and
drip from the roof are usually considerably reduced, and there is no need to
emphasise the importance of this latter benefit, for it is bound to save many
hundreds of pounds a year in breaks and broke, at least in mills where trouble
is experienced from roof condensation, besides the great saving in roof main¬
tenance costs.

The length of life of dry felts in one mill we know was increased as much
as three times when this system was installed, and the output was at the same time
increased by 15 per cent.

There is no doubt that it is a much cheaper and quicker way of adding to
the drying power of a machine than by the usually very inconvenient method
of installing extra dryers.

The ‘Happer’ Patent Felt Drying Roller (Fig. 85).—An important point to
ensure even drying of the paper and freedom from cockles is the keeping of
the dry felts evenly and properly dried.

Dry felts absorb a lot of moisture from the paper as it is driven out by the
heated cylinders, and they ought to be able to pass it away to the atmosphere
continually, in order that the wool may absorb further moisture on the next
revolution of the felt.

Originally felts were dried by passing them over separate drying cylinders
not hi contact with the paper. A further improvement on this was the blowing
of hot dry air on to the felt and into the pockets between the cylinders in order
that this air might absorb moisture. This air was subsequently drawn away
by fens. Both t h ese methods have the defect that only the surfaces of the felts
are dried, the moisture re m aining in the vicinity of the paper -making machine,
and some of it recondensing on to the felts. Also the hot and humid con-
dhxQQs hi the m a chine house, brought about by this method of dealing with
the moisture, make the working conditions unpleasant and cause troubles such

DRY FELTS

213

as condensation on any cold parts of the machine frame and roof and walls
of the machine house. This causes damage to steel work, and falling drops of
moisture, which are very troublesome when they fall on to the paper machine.

Several methods have been put forward to tackle this question of the con¬
ditioning of dry felts, but the one which seems to be the most successful and
which is very satisfactory in use is that known as the ‘Happer* patent felt drying
roller. These rollers, which are illustrated in Fig. 85, can be put on in con¬
venient places among the drying cylinders, and their construction is such that,
as the felts pass over the roller, the heat and moisture-laden air are drawn
right through the felt into the inside of the roller and conveyed by fan and

8KTK>W OW XX*

[Messrs. Hail mi Kay , and Bewdey mi Jackxm
Be. 85 .—The ‘Hatter* Patent Dry Felt Drying Cyundbr
{Tfrc iEnstration shows a complete section of the roll)

delivery duct out of the ma chine house* In addition, the rollers are wound
with a bronze wire in such a way that wandering of the felt is greatly reduced.

It will thus be seen that this method not only conditions the felt, but has
the added advantage of removing some of the mcasture-laden air from the room,
or at katf it does not allow this moisture-laden air to be blown into the room.

By plarmg a number of rollers at suitable positions among the drying
cylinders die felts are mamtainad at a much higher average standard of dryness
than can possibly be attained by some heated cy lin de r s, and there is not so much
danger of the browning oar burning of the felts. The felts are evenly dried
across the full width of the web, and the moisture is drawn right through*
thereby keeping the frit in much better condition, and more open and porous-

214

MODERN PAPER-MAKING

From our own experience we can say definitely that these ‘Happer’
rollers are by far the best method yet introduced for the satisfactory conditioning
of dr}' felts, and for ensuring evenness of drying across the full width of the
web.

The Heimbach system works on the opposite principle and blows dry air
through the felt into the machine house. This air becomes saturated by taking
up moisture from the felt, and has to be extracted from the room by means
of fans.

Smoothing Rolls .—These are two steel rolls, steam-heated, and are inserted

[Vickerys Ltd.

Fig. 86.—Vickery Flexible Doctor applied to a Press Roll

before the last section of drying cylinders. Their purpose is to smooth or flatten
die web of paper while it is still in a slightly damp condition. They reduce
bulk a good deal, but, if rightly used, are very effective in eliminating felt
*' marks, and, by closing up the under side of the sheet, produce a very equal-
aded paper. They should be run fairly hot, but not excessively so.

* doctor blades are necessary for both rolls, as any particle of stuff or
dkt may stick very firmly to their surfaces owing to the heat used.

The flexible doctor {Fig. 86) has revolutionised ^doctoring* of all rolls on
the paper m ac hine , and it is rapidly displacing die older forms of rigid iron

SMOOTHING ROLLS

215

doctors in most positions. It consists of a row of springs fixed to a rigid
holder, and these springs are slotted to take a flexible thin steel blade. It
will be easily understood that this flexible doctor blade readily accommodates
itself to any irregularities on the roll, and to variations in the position of the
roll—i.e., when paper is being led through at one end, and so tilting the roll
out of parallel with the doctor support.

In order that the blade may take up these distorted positions, it is obvious
that it must be capable of

moving sideways, as the distance
between the ends will be less in
these positions. The blade, being
only lightly held, can slide side¬
ways to make up for these
distortions.

Being thin and of fight con¬
struction, die doctor rapidly
responds to differences of tem¬
perature, such as the heat of
calender rolls, M.G. cylinders
and intermediate rolls. It keeps
the surface clean and polished
and in good condition.

The blades never need to be
filed and fitted and they last fairly
well, even on fast news machines.

The blade itself, when worn
out, is very easily replaced, only
a few minutes being required, in
place of the hours often neces¬
sary with the older types of
doctor, which had to be filed

\VtAuplM.

pj&. &7.-VlCKBttY PATBNT FlECTLE DOCK* AIYU8D
to a Bks&st Roll

until they fitted approximately.

A new type of blade is being used with great success for keeping rolls dean.
Hus is made of a bakdised cotton substance which takes on a very keen edge,
and seems to be self-sharpening. It can be used on breast rolls, wire rolls, and
press rolls, and fits more snugly to the roll than an iron doctor. It has many
advantages over wood and iron, and is less likely to groove the surface with
which it comes in contact

Calender Rafis.— Most machines making E.S. papers have three sets of
five rolls each. A very good machine finish may be got with these, but some

216

MODERN PAPER-MAKING

machines are fitted with as many as five sets, of which the first two sets may be
of three rolls each. All rolls are cambered to take an increasing weight towards
the reel end, and are fitted for steam heating, and have doctors and guards
before each ingoing nip. The bottom roll of each set is greatest in diameter
and is driven. The other rolls are driven by the friction between their surfaces
and the paper.

After passing through the calender rolls the paper will have received its
surface finish, and as a result of the heat and friction of the rolls, it is always
charged with static electricity. Sometimes this charge is very high, especially
so when the rolls are very hot and the paper has been allowed to get a little
too dry. Then trouble is experienced with the laying of the sheets when the
paper is being cut. They are attracted to parts of the cutter and also to each
other, which interferes with the ‘picking’ or overhauling later on. To cause
this electricity to be discharged the paper is led from the calenders over a
water-cooled cylinder or cylinders. Where these are not fitted, copper wires
are stretched across the machine, close to the surface of the web, and earthed
to a water pipe or to the frame. Conditioned paper is, of course, freed from
all static.

The web is wound round on a wooden or iron bobbin by means of a friction
winder. A square spindle or bar is put through the bobbin and the latter is
secured in its place by ‘keepers’. At one end of the spindle is a small cogged
wheel. The friction winder is composed of a shaft which carries a cogged
wheel to engage in that on the bobbin spindle. On the shaft: are two steel
discs, one of which is fixed; the other is free to move sideways. Between
these discs runs a pulley which comprises two polished sides. Leather discs are
interposed between the fixed discs and the running pulley discs.

The pressure between these discs is adjusted by a screw handle and the
friction gives the necessary tension to the spindle and web of paper. Drum
winders are also used.

The Machine Drive .—The drive’ is the term used to express the mparis
by which the various sections of the machine are connected to the source of
power, and includes the latter. Formerly one steam engine was used to drive
the various pumps, etc., of the wet end and also the machine itself. In still
earlier times it was not unusual to find a water wheel doing the work. The
mean s of power trans m ission was by belts and shafting geared to the engine
with spur wheels; as the wet end machinery cannot be varied very much in
speed, die range of speed for the machine was very limited
,^To overcome this difficulty, intricate arrangements of ‘speed wheels’
were used when very heavy or light substances were being made. This
entailed shutting down and lifting on and off heavy gear wheels, or putting

MACHINE DRIVES

217

intermediate wheels and shafts into action. Later on two steam engines were
used, of which one drove the wet end at a constant speed and the other the
machine itself from the wire onwards. This was a great improvement, but
the steam engines were of too heavy a type, with a limited range of speed, and
‘speed wheels’ were still necessary. Their heavy flywheels, parts and long
stroke prohibited a high speed, so there was only a limited range of speed at
which they could be used with any efficiency.

The reciprocating action of these heavy engines caused the belts to swing,
and the sections of the machine were very jerky and unsteady, and this was
the source of endless broke.

Many had no variable governor drive, and the speed was altered by hanging
more or less weight on the governor lever. As the necessity for higher speeds
arose, and to dispense with the inconvenience and loss of shutting down to
change speed wheels, the smaller type of high-speed light engines was developed,
and proved a great advance in steadiness and efficiency.

In the old type of belt drive the usual arrangement comprised a series of
gear wheels of various sizes, which had to be changed to suit the speed required.
The first press rolls were driven direct through a clutch on the main shaft. On
this shaft were three pulleys, from which one belt drove the wire shaft, one
the shaft for the main stack of drying cylinders, and the third the shaft for the
second press. On the cylinder shaft were the pulleys of the smoothing rolls,
the second stack of drying cylinders and the calender rolls. From one or other
of the calender roll shafts, belts extended to the cooling rolls, winder, etc.

The sections of the machine were put in gear by means of toothed clutches,
which started them up with a sudden jerk, imposing a great strain on the belts,
and specially on the teeth of the cylinder gearing. In fact, the engine had to
be slowed down to put the cylinders into motion, and unless this was done the
wheels were sure to be stripped of teeth.

The tension of the ‘draws’ was regulated by sticking on the pulleys, to
increase their diameter, pieces of ‘packing’, strips of old coucher covers, old
dry felts, etc., by means of resin boiled with oil and pitch. This had to be done
when the machine was running, and was a troubles© me,. difficult and dangerous
operation. The tendency of the pull of the belts was to drag the ‘packing’
into lumps, and in hot weather the resin refused to re m ain sticky enough, so
that pieces fell off and had to be continually replaced. When a piece of packing
could not be got off a pulley, a piece had to be stuck on the other to get the
draw correct, and the belts frequently stretched and broke under the strain.
The provisions of the 1937 Factory Act preclude the use of this type of drive.

Ihe introduction of the high-speed engine and variable speed electric
motors made it possible to arrange a drive which has none of these firin

218

MODERN PAPER-MAKING

Instead of heavy belts in series, the engine drives a shaft, usually overhead, from
pulleys on which each section is separately driven through bevel wheels, the
smaller of which is of hide, giving a smooth and noiseless motion. Light
belting (4 to 6 inches) is used, and cone pulleys supersede the packing method.

In another type—‘White’s drive’—the power is transmitted by a system
of ropes instead of an overhead shaft, and cone pulleys with light belts are
used to vary the speeds of the sections. No clutches are used, the driven cone
pulley being raised by a lever so that the belt is put out of action, and has no
wear and tear unless the section is being run. When starting up, the pulley
is lowered into the loop of the belt and the section starts gradually as the belt
is tightened up. This has shown itself to be a very efficient, smooth and steady
drive.

The Marshall Drive— The Marshall drive transmits power to the various
driving sections of the machine from a line shaft running parallel to the length
of the machine. Each unit allows a certain amount of speed adjustment, and
turns the drive through a right angle to couple to a driving shaft which lies in
a cross-machine direction.

In every stage of its development the unit has consisted' of a shaft carried
by bearings and stands horn the machine house floor, and driven from the
line shaft by clutch-operated cone pulleys, the latter being provided with
belt-regulating gear to give speed adjustment. The shaft of each unit has
fitted at one end a bevel pinion which gears with a bevel wheel on the section
driving shaft.

The advances made in the design of the Marshall drive since its first inception
consist mainly of improvements to the gear wheels, and the replacement of
ordinary bearings by anti-friction bearings of the roller or ball type.

The first arrangement of gear wheels would almost certainly have an iron
pinion with cast teeth, working in conjunction with a mortise wheel having
teeth of hornbeam or birchwood fitted into a cast-iron rim. Later, both
wheel and pinion would have cast teeth, and then in turn these would be
replaced by gears with machine-moulded cast-iron teeth, and eventually by
machine-cut teeth. Lip to this period the gear wheels had worked without
any serious attempt being made to enclose them, and lubrication consisted of
an application by hand of heavy oil or grease at frequent intervals. With
the advent of bevel gears made from high-tensile steel and having spiral teeth,
•®e M a rshall drive entered the field of precision engineering. Gears that were
now only about half the diam eter of the originals, but transmitting the same
power, required protection both from dust .and from the pflhrts of fruity
fab ric a t i on . It thus became necessary to enclose the 'gears in cases that were
both dust- and oil-tight.

HARLAND DRIVE 219

These modem units with gears running in oil, on shafts equipped through¬
out with roller bearings, occupy a minimum amount of space and are practically
noiseless in operation.

Most machinery manufacturers make a range of units of various power
capacities, each with variations in gear ratio. Their design allows ample
adjustment to be made to take up wear in the taper roller bearings, and also
has ball bearings fitted for the cone pulley to revolve upon when the unit is
not transmitting power.

[Hmlmi Eo gmem^ g Co. UL

Fta. 88.-Hajhland Drive on aoo Inch Board Machb*

Multi-Motor Drive .—The Harland drive (Fig. 88) is of the sectionalised
type with a motor on each section, the motors being coupled through double
helical gears to the paper machine driving-in shafts. Bor the purpose of main¬
taining relative desired speeds on the motors, a master reference is provided.
In the original system a light shaft was run along the full length of the machine,
this shaft being driven from the dryer section or by a separate master motor.
In the up-to-date version an ‘electrical master shaft’ is employed, giving greater
flexibility of layout aad control

Each section is provided with a differential regulator, one shaft of the
differential gears bemg coupled to a small synchronous motor running in
synchronism with the master alternator. The second shaft of the differential

220

MODERN PAPER-MAKING

Fig. 89.—The Harland Intersection Speed Regulator Unit

HARLAND DRIVE

221

gears is driven by means of a belt and cone pulleys from the motor to be
controlled, while the third member of the differential actuates the special shunt
regulator in the motor field.

The speed of the master alternator determines the speed of the paper marking
It is direct coupled to a small master motor.

As is well known, the speed of the third member of any differential gear
is the resultant of the speeds of the other two shafts. When the first and second

[HoHmd Engmeermg Co. Ltd.

Fig. 9o.-Hasolakd Dwtcng Uhtt

shafts are running at the same speed in opposite rotation, the third member,
which is connected to the regulator, will remain stationary. Immediately
there is any difference in the speeds of the first and second shafts, the regulator
will move in the required direction to correct the motor speed. If the load
changes—say, increases—the motor will tend to run slower, and as soon as this
happens the first and second shafts will not be in equilibrium, and the third
member will move the regulator and weaken the field until the two shafts are
running at the same speed again. If load is thrown off, the reverse action
takes place.

Hie system is absolutely positive, the three members of the differential
gear being mechanically locked together, and the smallest change in speed

222 MODERN PAPER-MAKING

between the first and second shafts is at once shown by movement of the
regulator.

Correction of an error in section motor speed is made very quickly, the
response of individual regulators being designed to take into account the
differing characteristics of inertia and frictional damping to give maximum
drive sensitivity without hunting, the accuracy of control being such as to avoid
strain on the web of the paper.

A view of the differential regulator unit and the small synchronous motor

[Siemens Schuckert

Fig. 91—Variable Speed Electric Reel-up, enabling Hard or Soft Rolls to be made

is shown in Fig. 89. The differential gears are housed inside the regulator
case, while the cone pulley shaft projects at the back of the case.

In Fig. 90 is shown a typical section motor •with interlock equipment and
cone pulley transmission to enable the draw of the section to be varied. Suppose
the belt is in position as shown in the illustration and it is required to alter the
draw by decreasing the speed of the motor, the belt must be moved by means
of the belt-shifter towards the large diameter of cone on the motor shaft; this
increases the speed of the second shaft of the differential gear and causes the
regulator to move and reduce the speed of the motor until the second shaft co¬
incides in speed with the first shaft. The regulator arm has now assumed a new
position on the face-plate, giving the required field strength for the new speed.

The draw is increased or decreased without breaking the paper or interfering
with the running of the machine.

MACHINE DRIVE

223

The drive takes up very little space, and may conveniendy be housed either
alongside the paper machine or outside the machine room in an annexe, with
the driving-in shafts passing through the wall or partition, as shown in Fig. 88.
It is very compact and accessible, and does away with all troubles from belts,
ropes and clutches.

-The drive is very efficient and provides great flexibility of layout both from
the point of view of mechanical arrangement and control. In particular, the
drive to each section of the paper machine can be designed to suit the inertia
and frictional loading characteristics to ensure equal accelerative response on
all sections to any common change in speed, thus relieving the paper of tendency
to tighten or slacken between sections .under such conditions. The speed of
the whole paper machine can be maintained so constant as to limit the variation
to a fraction of 1 per cent, a factor of considerable importance for high-speed
paper machines. All control can readily be arranged at the front of the machine
in the most desirable positions for machine speed as a whole, section motor
inching, crawling, starting and stopping and draw adjustment with local
indication of speed, power requirements and draw settings. Individual sections
of the machine can be shut down, inched or crawled without aflfecting the
correct interlocked running of the remainder. Heavy sections can be electrically
braked for quick stopping, thus minimising delays and tending for safety in
the event of accident.

The ease of control, speed constancy and reliability of this form of drive
combine to give maximum output of highest grade product, and it is not
surprising to find its application being extended to all classes of paper-making
machine, both large and small.

The British Thomson-Houston Company also make a sectional electric
drive which is in use on paper machines, and a recent improvement is the
separate driving of each individual cylinder which has bon developed by
Siemens, who were licensees for the Harland system. For certain papers this
system possesses definite advantages.

CHAPTER XIV

PAPER-MAKING ON THE MACHINE-WATER-MARKING

Notes on Machine—General—As paper-making on the machine varies so
very much with the qualities, substances, etc., of paper, it would he futile to
attempt to lay down hard-and-fast rules as to how the various parts of the
machine should be used. The machineman has to exercise his judgment, and
must have at his command numberless ‘dodges’, if we may be allowed to
call them so, for getting the results he wants.

As far as the strainers there is little that may be called paper-making’.
It is when we get the stuff to the wire that the art and skill of paper-making
commence. The slices are the first consideration, and these have more to do
with the look and strength of the sheet than may be supposed. On some
machines there is a lifting gear to raise or lower the breast roll end of the wire
frame. A low level will cause a deep ‘dam’ to form behind the slices, and a
deep pond will remain after them. Under the influence of the shake this might
be expected to close up the texture of the sheet, but it is not always so. The
rising slope of the wire will result in the stuff and water rolling over and turning
on itself, and a cloudy, though well water-marked, paper will be made. This
is what is generally wanted for laid ledger papers of a certain class.

By raising the breast end a little the stuff will flow out from the slices more
freely, and though not being so long under the influence of the shake, will
produce a closer-looking sheet.

The same result can be obtained by increasing the speed of the machine,
and taking the stuff away from the slices before it can get time to roll back.
Thus if the breast end is fixed at one level, the speed of the machine may be
used to do the same work as a lifting gear. Ag ain, if we have a deep dam
behind the slices—i.e., the slices dose down on the wire—the stuff will shoot
out and forward, and go well up the wire, and get very little good from the
shake. Also, the fibres will be turned round and set on edge by being forced
through a very fine opening. This makes a raw and badly water-marked sheet.

By rasing the shoes the fibres will flow gently on to the wire, and the shake
will get hold of them at once where the longest throw occurs. Then the fibres
will be well felted and dosed up, and the sheet will be found to be stronger
and closer in texture and have a dearer water-mark.

224

RUNNING THE MACHINE

225

Therefore, though a lifting gear at the breast end gives a little more chance
of varying the conditions, it is by no means a necessity for an ordinary machine.
By using the slices intelligendy and getting the proportion of stuff'and water
correct, its absence will not necessarily be a disadvantage.

The behaviour of the stuff and water on the wire is a very interesting study.
It will be found that in every case there are long fibres and fibrillae, some of the
latter so fine as to be nearly powdered. On emerging from under the slices,
if the water is nicely proportioned, the long fibres fell to the under side of the
sheet, and the fibrillae remain for a time in suspension with the water. The
action of the shake, contrary to what one might expect, keeps these finefibrillae
suspended for a time, until they are sifted into the spaces between the longer
fibres, and by the gradual drawing out of the water by the tube rolls they
remain there permanently. As the stuff approaches the first suction box, the
action gradually ceases, so that the suction sets the sheet without altering the
disposition of die fibres. It seems to be a fairly general belief that the shake
turns the fibres from their ‘end-on flow from the apron. But a simple experi¬
ment will show that this is a fallacy. Take a few matches and float them in
a rectangular tray. Give the tray a sideways shake and the matches will arrange
themselves broadside on to the direction of the shake. Close observation
will show a similar action on the wire when the stuff is beaten rather raw and
long. It must be remembered that the shake does not make a jiow, but, what
is quite a different thing altogether, a wave.

Actually, with a well-fibrillated stock, the longer (or any) fibres are not
moved much, if at all, from their endways flow. Moreover, the end-on flow
of the fibres from the apron is not so pronounced as is generally supposed.
The passage under the slices tends to turn round fibres that are pointed end¬
ways, especially the longer and bulkier ones. These, being entangled with
fibrillae, will naturally remain very much in the position in which they emerge.
If they do alter their position, it will be towards placing themselves end on,
because the shake is forcing them to this position.

An examination of paper made with and without shake will show this to be
correct. The increase in strength given by the shake is due to the fibrillae
being spread and sifted into what would otherwise be bare spaces, or air
spaces, and making a uniform in place of a ‘patchy’ paper. If there is too
little water with die fibres, the fibrillae will not be so sifted, because their
carrying medium is absent. If too much water, they will not have settled
before reaching the suction box, but will still be in a suspended state. Then
too much suction will have to be used, and the whole fabric of the sheet will
be disturbed.

A long wire is not always an advantage in m a kin g strong papers. Hit

226

MODERN PAPER-MAKING

extra water which is used and the extra time the stuff is under the influence
of the shake give the shake more opportunity of bringing the fibres into an end-
on position. Ledger and other strong papers made on a 50-feet wire have a
more pronounced difference in breaking strain across and along the sheet than
those made on a 40-feet wire, and it also is more difficult to give the sheet
the characteristic look of strength combined with clear water-mark which is a
feature of good ledger papers. If it is desired to give to a paper made from
rather poor stock the appearance of strength, a deep dam behind the slices will
cause the stuff to rush well up the wire and get very little result from the shake.
It will then look strong because the dandy roll has no nice level surface to
impress, and the fibres will be arranged in all directions, but it will have less
strength than if made a closer-looking paper.

In trying to make a close, well water-marked sheet from stuff that is not
well fibrillated, exttja water and shake will be effective only up to a certain
point. That point has been reached when- the fibres are not settled into a com¬
pact body before reaching the suction box. Less shake may be tried, or if
shake is known to be not above normal, less water is wanted.

Too much water and too little shake, or either alone, are shown by the
formation of water drills. These are thin streaks made by the water running
in channels along the wire and refusing to amalgamate with the stuff. More
often too much water is the cause. But a wire that is dirty in streaks, or badly
beaten stuff, will also give the same trouble.

Stuff that is beaten very fine— i.e., very much cut by the beaters—is easily
water-marked, and looks ‘wet’ on the wire, but is shown to be free when
passing over the suction boxes. This style of beating and paper-making makes
a very nice close sheet and a clear, bright water-mark, but the strength is very
poor for the quality of the stock used. Water drills are very often prominent
in stuff of this description.

It may be mentioned in passing that fresh water is more productive of water
drills than the softened back water of the machine; also, if fresh water has to
be used to supplement the back water of the machine, it is much more difficult
to make a close sheet.

In making an engine-sized paper the slices have to be closer to the wire
than would be otherwise desirable, in order to keep back the froth which
forms on the breast of the machine. Very often with strong stuff, and with
papers containing a large proportion of wood fibres that have been kept a good
length in the beater, numberless clear specks and spots appear in the paper.
These are caused by the chemical action of resin, alumina, hard water, etc.,
forming carbonic add gas (COt). This formation of gas takes place on the
wire itself as well as before it. The little bubble of gas keeps the fibres from

RUNNING THE MACHINE

227

settling on the wire, and when it hursts, it is usually too far advanced towards
the suction box for the hole to be closed up again. The remedy is to use as
much water with the stuff as is possible, to fill the space again that has been
made by the bursting of the bubble. Beating the stuff finer, or running at a
slower speed, will also effect an improvement. Entrained air and other gases,
sometimes caused by the chlor-lignins, also cause these froth spots.

Froth is often a great nuisance on the machine, and sprays should be pro¬
vided to keep it down as much as possible.

A litde extra alum will sometimes be of great assistance, or a little par affin

[Gram, So* mi Wmtt
Fig. 92.—Wote Ron

run into the stuff from a tin above the chutes by means of a woollen thread,
where this is otherwise permissible.

Steam Heating of Stode.—The effect of raising the temperature of the stuff
and water on the fttachme is to make it work more ‘free’. Advantage is
taken of this fret when making heavy substances or running highly fibriflated
stock. By raising the temperature to about 90° to 95 0 F. an extraordinary
change in the working of die stuff on the wire can be observed. The fibres
swell up and become more rigid, the meshes of the wire open a little owing
to the expansion of the metal, and, chiefly important, the tenuity of the water
is increased and its surface tension lessened. The effect of these things is that
the work of the suction boxes, and consequently the strain on the wire, is
made much less. More water and shake can then be used and a closer and more

228 MODERN PAPER-MAKING

clearly water-marked paper can be made. The best situation for the steam-
pipe is in the top-level water box. A stronger paper may be made from heated
stuff than from the same stuff run cold.

The Dandy Roll and its Use.—The body of a dandy roll is a brass tube on

[Green, Son and Waite

Fig. 93 .-Laid Roll, Ordinary Journal Type

which are fixed a number of brass discs and a framework of cross-wires. A
cylinder of wire cloth similar in mesh to a machine wire is pulled over the
body and fixed at the ends. This is called a ‘wove’ roll (Fig. 92). The
centre tube is extended as spindles, which run in the bushes of adjustable

[Green, Son and Waite

Fig. 94.—Wove Dandy Roll, Hollow Type

brackets fixed at each side of the machine, between the first and second suction
boxes or in a position found most suitable. A ‘laid’ roll (Fig. 93), instead of
having a woven cover, has one made from parallel wires. These are kept
ajpart and in position by twisted wires round the circumference, from f to

DANDY ROLLS

229

1 \ inches apart. These are called the ‘chain’ wires. Letters and devices of
wire may be sewn or soldered on the surface of the roll.

Hollow Dandies .—Nowadays increasing use is being made of hollow-type
dandies having no spindles or journals (Fig. 94). These are very rigidly con¬
structed and have many advantages over the old type. In the first place they run
on a rim supported by rollers on ball bearings, and have a very fine adjustment
(Fig. 95). The bracket which is illustrated also has a quick lilt lever, enabling
the dandy to be lifted clear of the wire instantaneously. The fact that the dandy

[Grew, Swi md Wdk

Fig. 95.— Dandy Stand, Bearings and Adjusting Mbchankm *ot Bouow Da»d®

is hollow enables stationary steam- and water-pipes to remain inside the dandy
and to be used continuously or intermittently for cleaning it from the inside.
The advantage of this will be obvious. It is also possible to fit a stationary
tray inside to catch water and pieces of stuff and run them clear of the dandy.

The introduction of these hollow dandies has enabled much greater speeds
to be attained without deterioration in die quality of the paper, and it is possible
to run these dandies for 6 to 8 weeks continuously without having to remove
them from the machine for cleaning.

The function of the dandy roll is primarily to assist in closing up the sheet
by pressure on the fibres while in a wet state. For this reason a roll as heavy

230

MODERN PAPER-MAKING

and large as can be run on the substance should be employed. Where letters
or devices are on the roll, and require to be spaced for registering accurately
a certain size of sheet, the size of the roll has to be accommodated to the size
of the sheet. The letters or devices, being raised above the surface of the roll
cover, impress themselves on the stuff on the wire, and by making thin places
where they touch, cause the design to be transparent when looking through
the sheet.

This is called the ‘water-mark 9 . The clearness of the water-mark depends
upon a great variety of circumstances, among which the chief are the amount
of water left in the paper after passing the suction box or boxes in front of the
dandy; the quality of the beating; the quality of the fibres and their length;
the weight and diameter of the roll; the thickness of the wire forming the letters
or designs; the speed of the machine; the substance of the paper, and the skill
used in closing up the paper on the wire. Subsequent operations on the mac hine
and the finish, also affect the water-mark. The couch rolls and presses all
contribute a little tow r ards taking away the clearness, and so does a very high
finish, which may go so far as nearly to obliterate it altogether.

The proper amount of water to leave in the paper to get a good impression
from the roll is altogether a matter of experiment. The suction is altered until
the desired result is obtained. If too much water is left, the paper is crushed by
the dandy roll; if too little, the roll makes a faint water-mark. Very fine stuff
gives the best results in wove papers. The wires sink into the body of the paper
without encountering any long or hard fibres. Wdl-fibrillated stock is re¬
quired for the good water-marking of thin substances. A good laid mark
requires longer stuff.

The fine fibrillse on the surface take the impression well and long fibres
on the under side help to sustain the weight of die roll and prevent ‘pick up 9 .
Soft, fine fibres such as esparto are easily water-marked. The wires of a design
on a small diameter roll stand at a more obtuse angle from th e circumference
than they do on one of greater size. This makes them have a ‘digging-up’
action, which is very apt to cause ‘pick up’. The figures on a large roll fall
on the wire with more of an impressing motion, and are also supported by a
greater plain area, which helps to press the water through the wire and prevents
it returning to the impression and filling it up again.

Trouble is sometimes experienced from air bells with a wove dandy. A
stream of air or steam, impinging on the roE as it rises from the sheet, stops
the trouble, but i£ froth bells are coming along the wire their source must be
found and stopped; usually more water will stop them. A laid roll with the
laid lines arranged spirally round the circumference is used occasionally for
cheap papers to attain a higher speed, but it makes but a poor water-mark.

DANDY ROLLS

231

When using a roll with letters or designs on a thin paper it will be found
that the raised letters, etc., pick up fibres or bits of pulp, the size of wilich
increases with each revolution, until they fall or are brushed off by the machine-
man. These are termed ‘dandy picks’ or ‘picks’ and are responsible for a great
percentage of broke in thin papers. A small diameter roll, or one with heavy
designs, gives most trouble. The remedy is to raise the roll carefully, so as
to take as much weight off the stuff as possible without losing the clearness of
the water-mark, or to reduce the speed of the machine, or to increase the length
of the fibres, by altering the beating.

Therefore the character of the water-mark and the suitability of the roll
have to be considered when trying to increase speed on a thin paper. An
increase of speed is of no value if the proportion of broke from this cause is
also increased.

A strip of old wet felt, called the ‘wiper’, is suspended by a rod over the
dandy roll, and may be let down on it when running at a low speed. It is
an excellent device for keeping the roll clean and free from ‘picks’, if it can
be used. Wove rolls are liable to fill up with froth, when they have to be
taken off the machine and washed out. Fine sprays of cold water are sometimes
used on the roll to prevent the froth forming. A rubber roller running on
top of the dandy will be found of great use in collecting the bits of stuff picked
up by the dandy. This roller throws them on to a cloth fixed in front of the
dandy.

Dandy rolls with designs that must register correcdy have to be set in correct
parallel across the machine to bring the designs square with the cut sheet.
The draws or tensions between sections of the machine are used to bring the
water-mark correct with the cutting length or ‘chop’. Often a roll will be
found to be short in the draw, and after all the sections have been pulled tight
the draw is still too short. A few turns of tape, or one turn of' thin old wet
felt round the ends of the dandy roll outside the deckle edge of the paper, will
lengthen the dktanre between the designs, and it is more prudent to do this
than pull up the section^ too hard. If the wiper can be used, it will give a
fraction of an inch more length by slighdy dragging the roll. The register of
the water-marks across the roll is more difficult to alter. On narrow deckles
(up to 60 inches) they are seldom £iur outi, but cm wider sheets, such as four or
five sheets of 16I inches, the beating and quality of the fibres may alter the
shrinkage by as much as 2 inches. The beating of the stuff must then be altered
to bring the width into register with the roll. If the draws can be altered the
width may be controlled a little, so that by putting a turn or two of tape
on the roll the length may be brought out and the draws put hack, which will
give more space between names across the roll.

MODERN PAPER-MAKING

232

When ordering a new roll, the makers should be made aware of the quality
for which it is to be used, when they can produce a roll with the water-mark
spaced to come very correct.

Extra weight on the couch and press rolls will prevent shrinkage on the
drying cylinders to some extent; so also will tightening up the dry felts, hut
in these cases the shrinkage is apt to take place later— i.e., on the dryer after
tub-sizing.

A laid dandy roll is more tricky to deal with than a wove. It is customary
to have a small tube roll or a soft brush set exactly under the roll. This allows
a little more water to be used after the suction box. The tube roll or brush
takes away the extra water that is pressed through the wire by the weight of
the dandy roll. But if too much water passes under the roll, it will ‘lift* sections
of the sheet partly off the wire.

These sections may be even lifted off the wire and stick to the roll for a
few turns, when they come off and spoil the wire by passing through the couch
rolls. If a good water-mark cannot be got without this happening, the make
of the paper on the wire must be attended to. More shake and, if neces¬
sary, more water are required, so that more suction is used on the first suction
box. This will ensure that the sheet is pulled down on the wire with more
force than the weight of the dandy roll can exert to lift it up again.

A little manipulation of the tube roll or brush may be all that is necessary,
but care must be taken not to raise the roll or brush so high that the wire is
lifted off the suction boxes, or that the paper is made to look streaky. All
dandy rolls should be allowed 4-inch play between the brackets, so as to allow
for the slight movement of the shake, and to prevent them bang dragged.

Dandy rolls being very delicate and expensive, too much care cannot be
expended on their use and storage. They should be carefully washed out by
means of a good jet of water when they are taken off the machine. If they are
left standing for some time, while the machineman does something else, the
frothy matters in the meshes will quickly dry up, and be very difficult to get
rid of. Indeed, it is sometimes impossible to clean them without using strong
add, which is the worst possible enemy of the dandy roll.

A machineman who neglects to wash out and thoroughly clean a dandy
roll immediately on taking it off a machine does a grave injustice to his employer
and to his shift mates, who will perhaps be compelled to take drastic means of
ckanin g it before it can be used again. In any case, every machin eman should
carefully e x a mine the condition of a dandy roll before he puts it over the wire,
ami report to his foreman any damage it may have received.

When the web has passed tinder the dandy roll the paper is made. Subse¬
quent operations are simply water extraction, with the minimum of damage

WATER-MARKING

233

to the bulk and water-mark and the elimination of felt and wire marks. Finish
on the machine is a question of moisture, pressure and number of rolls used, and
practical experience and experiment on the part of the machineman. Moisture
content is controlled by the drying operation, and this again by the steam heat
admitted to the drying cylinders. Several systems may be used by the dryer-
man. A certain pressure may be admitted to several or all the cylinders and
controlled by the main Valve; or he may use the cylinders separately, admitting
more or less pressure, according to the feel of the paper, without altering the
main valve. The third and best way is to keep the pressure constant by using
the main valve and to make finer adjustments separately on each cylinder.

The heat of the cylinders should be so graded that the paper gets no sudden
heat, but is gradually raised in temperature as it travels towards the dry end.

It is very difficult to get and keep a regular finish on a paper-making machine.
There must be a certain quantity of moisture left in the paper before it enters
the calenders, and the condition must be the same all across the sheet. Any
unequal pressure of the couch and press rolls, worn and damaged wet or dry
felts, dirty or corroded places on the drying cylinders, unequal spread of the
stuff on the wire or ridges in the latter will affect the moisture content of the
paper and show up in the finish.

A change in the beating from wet to free, or vice versa, however slight,
changes the conditions of the pressing and drying and upsets the finish. Con¬
stant attention and good clothing are necessary if the finish is to be kept accurate
and constant to the sample.

Great care is required where using steam-heated rolls, as heat affects the
camber, sometimes expanding the ends of the rolls more than the centres. It
is best to heat the rolls thoroughly before starting the machine.

When the paper is put through, the result will enable the machineman to
alter the heat, or put on more or less pressure to get a level finish . If the rolls
are not h eated in time there will be the greatest difficulty in heating them
afterwards, owing to the cooling effect of the moist paper. As calender rolls
are cambered to a certain pressure, any pressure over or under that point will
cause uneven finish across the sheet. If the finish is not correct with the pressure
intended for the rolls, the spread of .the stuff cm the wire must be slightly
changed to suit the pressure required. Thus if an unequal spread gives a finish
too high in the centre, by putting down the slice in the centre of the wire
the paper will be slightly less in substance and will come along the machine
dryer and take less finis h. Too much pressure on the calender rolls, even when
well cambered, gives high finish at the sides and low finish in the centre, because
the rolls are sprung on the centre. This seems incredible with steel roils of
the usual diameter, but can be easily proved to be correct by experiment

234

MODERN PAPER-MAKING

When an equal finish across the web cannot be obtained, the spread of
the stock on the wire should be looked to. Too much pressure on the coucher
and press rolls will make the edges of the web too dry, because these rolls also
are cambered to a certain pressure and spring in the centre.

A badly worn felt which is most worn in the centre gives a high finish in
the centre and low finish at the edges, owing to the edges pressing the paper
against the cylinders harder on the edges than in the centre, this giving an
unequal moisture content. Constant attention is required to keep the finish
correct; when the exact finish is obtained the attendant should note the position
of the carrying roll over which the web passes after leaving the cylinders. The
spring will be found to tighten up when the paper is too dry, and to darke n
off when it is too moist.

The average position should be noted, and if necessary marked, and the
least change in moisture content will be quickly apparent. Another good
guide is the amount of steam coming from the last dry felt as it leaves the paper.
When altering the speed of the machine or the substance of the paper, the
man in charge should always tell his assistant so that he is not taken unawares,
but can shut off or put on steam beforehand.

Water-Marking .—The water-marking of paper is carried out in two distinct
ways, depending on whether the paper is hand-made or made on a Fourdrinier
machine.

In the case of hand-made paper, the design is formed on the wire cloth
of the mould by sewing or soldering designs or letters in wire upon it. When
the mould is immersed in the stuff, die wire designs or letters cause a thin place
in the stuff, and this appears as a transparent place in the finished s h e et.

A variation of this effect may be achieved by pressing or counter-sinking
a design into the wire cloth, and in this case a thick place is made in the stuff—
i.e., more stuff is deposited there—so that a dark or thick mark appears in the
finished sheet. A combination of thick and thin places may be produced on
the same sheet and very fine effects may thus be obtained.

The water-marking on some currency and bank-note papers made by hand,
and also on the machine, is very beautiful, and requires a high degree of skill
on the part of the wire-workers who make the moulds.

Ihc second method of water-marking is that used on the marking and it
dife from the previous one in that the impression is made on the web after
a good deal of the water has been removed and the web has become setded in
place on the wire.. It is carried out with the aid of a wire-covered skeleton
<hum made of brass and supported in brackets fixed to the wire frame. These
hraetcts have a fine adjustment screw, so that the drum or dandy roll, as it
is called, may be very finely adjusted upon the surface of the stuff. The roll

WATER-MARKING

235

is always placed after the first or second suction box, so that the amount of
water left in the web when it reaches the roll may be regulated.

It is in the careful and skilful manipulation of the water in the web when
the dandy roll touches it that the best results may be obtained, for if the web
is sucked too dry, no mark will show, and if left too wet it will be crushed
and ‘worms’ or ‘tears’ will appear in the sheet

The dandy roll performs two distinct functions. First, it closes up the
sheet, compressing the fibres together and generally improving the appearance
or look-through of the paper, and for this purpose it is not necessary to have
any design upon the roll; and, second, it is used for putting a name or device
into the paper. In a plain ‘wove’ roll the skeleton drum is covered with fine
wire cloth similar to the machine wire, and this roll does not actually water¬
mark the paper, but simply closes it up. Very high speeds may be attained
on ‘news’ machines, using a plain wove dandy, provided the roll is of sufficient
diameter and of correct weight and construction.

A different type of roll, and one used chiefly on ledger and thick writing
papers, is known as a laid roll (Fig. 93, p. 228). This roll, instead of being
covered with wire cloth, is covered with a collection of thick brass wires bound
together at intervals of an inch or so by fine wires. Various gauges of wire
are used, and thus the number of wires to the inch may be varied to suit the
thickness or other characteristics of the paper. The thicker and stronger the
paper, the coarser the wire used and the fewer the number of wires to the inch.
Azure or blue papers look better with fewer wires to the inch than cream
papers. A medium substance of ledger paper usually has about 18 wires
to the inch, a writing paper about 20 wires and a thick, strong ledger about
16 wires.

Water-marking by means of a dandy roll is done by fixing a device or
letters worked in wire on the cover of the roll, and this may be done cm either
a wove or a laid roll. The device stands out from the surface of the roll,
and the weight of the roll presses the wires into the soft wet web, forcing the
fibres away in all directions and thus forming a thin place in the web. When
paper marked in this way is held up to the light, the device shows up as a
translucent pattern.

Formerly, water-marks served as trade-marks for mills m a kin g the paper,
and to a certain extent this still holds good, although probably the greater
number of registered water-marks nowadays belongs tothe wholesale stationers
and printers. Some well-known devices are shown in Fig. 96. The marks
vary from simple words of a few letters to the most elaborate and artistic
designs—coats of arms, ships at sea, etc. Some very fine water -markin g
is done on papers for postage stamps and bank-notes, and, generally

WATER-MARKING 237

speaking, the finer and more intricate the design the slower the speed at which
the paper has to he run. Many rolls containing intricate designs, and especially
those having small round spaces enclosed by wire, are very troublesome on
the machine, owing to the fact that they pick small pieces of stuff out of the
web, causing holes to appear in the finished sheet.

By far the greater proportion of water-marks have to register in the finished
sheet—that is, they have to fall in a predetermined position in every sheet when
it is cut and ready for use. In order to achieve this the dandy rolls have to
be made to suit different sizes of paper, so that they vary in circumference and
also in the spacing of the names across the roll. •

Bg. 97.— Showing how the Wathr-maii: faiis m a Large Post Vnacm 4T0 Shctt, 4 m

The devices are either sewn or soldered on to the cover after being made
separately, and when they are in position on die cover, all connecting wires
used to hold the letters, figures or designs in place have to be removed. The
designs are generally soldered cm to the cover, and this is done by tinning the
whole device before placing it in position and then running a soldering iron
over it, causing the tin to run down and fix the wires to the cover.

Since the web of waterleaf is drawn out in length—/.?., in the machine
direction—during the time it passes from the wire until it is dried, it will be
obvious that the distance between the devices round the roll will have to be
less than the distance desired in the finished sheet, and as die web shrinks in

238 MODERN PAPER-MAKING

the cross direction, the devices 'will have to be spaced out further across the
roll than they are to be in the finished sheet. These variations must therefore
be allowed for when ordering a roll for any particular size of paper. The
variation's remain fairly constant for each machine, but depend, of course, upon

I CsIsto Cai&vs

j W GSA Vi V*. G5&- W

WGS&W WGS&W

OstawD |

AGS4W WGS&W

WGS&W WGS&W ‘

[Green, Son and Waite

Fig. 98.—Showing how the Water-mark falls in a Large Post 8vo

W 6 REEKS 0 N&WAITE

W GREEK SONS WAITE

W GREEK SONd WAITE

W GREEK SON 8 .WA 1 TE

[Green, Son and Waite

Rg, 99.—Position of Water-mark in Broad Quarto Sheet

the ‘draws’ from the couch roll and presses, the heat of the first set of drying
cylinders, and also on the nature of the stuff.

A roll for water-marking a sheet of Large Post, made 16$ inches across the
m ac h i ne , will have to be about 20J or 20| inches in circumference and the

WATER-MARKING

239

names will be spaced about 17I inches apart; this will allow for a stretch of
about i to | inch down the machine and a shrinkage of about f inch across
the machine for each sheet.

Figs. 97 to 100 show the positions of the water-marks in a sheet of writing
paper.

Unless these matters are carefully attended to and the ‘draws’ carefully
regulated, a great deal of broke will be made at the cutters, on account of the
name or design not appearing at the correct and regular interval in the finished
sheet. With papers for postage stamps and currency notes, where the water¬
marks have to register exacdy and correspond minutely with intricate printings

and perforating, special cutting marks are placed on the dandy roll, and the
distances between these must be frequently checked by the machineman, at
least after each beater is emptied, in order that any slight variation may at
once be rectified by altering the draws or ‘hanging’ or lowering the
dandy.

If the marks are coming too close, the dandy may be ‘hung’ or raised a
little by lifting the brackets so that it drags on the stuff, or if the marks are
too for apart die roll may be let down into close contact with the stuff. The
roll is driven round entirely by the friction of the stuff, so that the amotatt
of impetus given to it may be varied by the two methods mentioned. A third

240 MODERN PAPER-MAKING

way of increasing the drag upon it is to hang a felt cloth on it from above;
this acts as a brake and reduces its speed.

None of these methods of ‘dragging’ the dandy roll is to be recommended.
Both are inclined to cause ‘pick-ups’. A far better way is to run a turn or
two of tape round the ends of the roll. This will give a more regular distance,
and it the paper is of thin substance will take the driving of the roll off the
stuff a little and prevent ‘pick-ups’.

CHAPTER XV

THE M.G. OR CYLINDER MACHINE-THE VAT OR BOARD

MACHINE

The M.G. machine (Figs, ioi and 102) is a modification of the Fourdrinier
machine, designed to produce papers having certain distinctive characteristics
as to surface.

The single-cylinder (or M.G.) machine is so called because it usually has
only one drying cylinder in place of the tiers of cylinders arranged on Four¬
drinier machines. It is sometimes called a ‘Yankee’ machine.

The wet end is exacdy the same as that of the ordinary Fourdrinier, having
chests, sand-tables, strainers, wire part, couch rolls and—in the case of ordinary
machines—press rolls as welL

When the web leaves the press rolls it is led on to a felt, usually of special
make, and this felt leads it into a nip between the large drying cylinder and
a press roll or press rolls. The pressure exerted at the nip causes the wet web
to stick to the polished surface of the hot cylinder, and it passes round the
cylinder to the reel.

The cylinder is the most important part of the machine, is made of cast
iron, or a mixture of iron and steel, chromium, etc., and is from 8 to 15 feet
in diameter. The surface must be entirely free from blemishes of any kind if
perfect paper is to be made, as any holes or depressions or fiat places will seriously
affect the surface of the paper. It should also be capable of taking on a good
‘shin’ or surface to which dust and fluff from the web will not adhere; or if
it does adhere, should clean easily at the doctors.

The cylinder must at all times be absolutely clean and smooth if the beautiful
mirror-like gloss, so necessary to the majority of M.G. papers, is to be main¬
tained.

These large cylinders are no doubt very difficult to cast, but a really good
one is worth almost anything to the mill which possesses it.

On most machines the cylinder is fitted with a hood or cover, which
fits closely round the surface of the cylinder for about three-quarters of
its circumference. Under this hood there are, on some machines, a series of
steam-pipes so placed that they are very dose to the web of paper as it passes

241

243

MODERN PAPER-MAKING

round the cylinder. Dry steam passes through these pipes and heats the moist
vapour which is being driven from the web of paper by the heat of the cylinder.
This assists the web to part with its water, and the vapour is drawn away from
the hood by means of a large pipe and fan which exhaust to it atmosphere.

On other machines the hood has no steam-pipes, and the vapour is exhausted
to atmosphere by means of a fan only. The process is really vacuum dr ying
except that the vacuum is very low owing to there being no sealing of the
joints between the hood and the cylinder.

There are two distinct methods of drying the web on these machines, which

[Bentley and Jackson

Fig. ioi.—Drying Cylinder of a Large M.G. Machine, showing Two Press Rolls and

Complete Hood

have a marked effect on the finished paper, both as regards under side and
surface.

In one method the top side of the paper—that is, the side farthest away
from the wire and wet felt of the machine—is brought in contact with the
surface of .the cylinder. In order to effect this, the web has to be led round
the cylinder in such a way that it fini shes up at the front top of the cylinder
nearest the wet end of the machine, and immediately above the press rolls.

Uns method obviously gives the smoothest surface and the roughest under
side.

M.G. MACHINES

243

The other method consists in leading the paper from the press back into
contact with the cylinder—which is revolving clockwise or in the same direction
as the wire—and in this case the under side of the w'eb comes in contact with
the cylinder and receives the smooth finish.

The result of this method is that the under side of the paper though
‘finished’ has not the close and highly polished surface of the paper made by
the first method.

In order to modify the effects of these two arrangements and to suit the
particular paper to be made, recourse is had to felts of various qualities. These
felts, used to carry the web through the cylinder nip, are called ‘overfelts’,

[StfMfW Sdmtckert

Pbg. 102.—Elbctbjc Dsiye httbd Dtracr to JouiNAi of a Lamb M.G. Cyunpbr

and may be had either rough, smooth, thick or thin, ribbed, striped or plain,
according to the effect it is desired to produce in the finished paper; they
are made of wool. The finish obtained depends on a variety of circum¬
stances, but chiefly on the surface of the cylinder, as has been stated above.

The press roll which squeezes the web into contact with the cylinder is
worked by means of compound levers and weights, and it has to be very rigid
to stand die strain and prevent it from springing in the middle and thereby
reducing the pressure on the web.

Opinions differ as to the best position of this roll, but it is usually placet

244

MODERN PAPER-MAKING

exactly under the centre of the cylinder, so that the nip given to the web of
paper and felt is as direct as possible.

These press rolls were at one time made of iron, but they are now more
generally covered with rubber, as they give almost equally good results and
are much less hard on the felts.

On some machines the press roll is placed either in front or behind the
centre of the cylinder, so that the pressure of the weighted lever does not press
direcdy to the centre of the cylinder, but to a point between the centre and
the circumference, and has a dragging action. Our experience has led us to
favour the former method, and we are of opinion that the paper must stick
instantly to the cylinder and remain fixed in close contact with it during the
whole of the time it is passing round.

On other machines two cylinder press rolls are fitted, but we cannot under¬
stand the necessity for these, in spite of the fact that they are presumably giving
good results, and they are being fitted to some of the latest machines. It
would appear to be highly probable that the second press roll to come in contact
with the web would interfere with the work done by the first one, in sticking
the web to the cylinder.

We believe that two press rolls are the cause of a lot of trouble on M.G.
machines. It is asserted that by having two rolls the pressure on each can be
varied at will to suit the special requirements of the paper being made. We
think this is very doubtful.

The overfelts are usually washed continuously after they leave the press
roll, or if no washer is available they are sprayed with cold water to cool and
clean them before they again come in contact with the web.

An important factor in determining the finis h of both sides of the paper
is the amount of water left in it at the wet press rolls. If a good finish is re¬
quired, the web should be fairly moist on reaching the cylinder; and if a
pronounced rib or stripe is required, or a rough under side, the wet press rolls
should be let down very lightly or they may be hung up altogether. This
will leave the web bulky and impressionable, so that the full effect of the over¬
felt can be produced.

The furnish of the paper and the way it is beaten have, of course, a very
marked effect on the finish, as obviously very long and wild stuff will not take
on such a good finish as finer stock, or a common brown as will a pure sulphite.

The state of fibrillation or wetness also has another important effect, in that
if the stuff is too wet it may be impossible to get it to stick to the cylinder at all.

For kraft papers and sulphites it is usual to tty to get the highest possible
finish, while for lithos and certain other papers too high a gloss is not
desirable.

M.G. MACHINES

245

It may be taken as a general rule that the purer the furnish used the easier
will it be to keep the cylinder clean, and the making of common papers from
refuse containing grit, oil, tar, etc,, is very detrimental to the surface of the
cylinder, as is also the use of bleached pulp from which the bleach residues
have not been properly removed.

It has already been stated that about three-quarters of the cylinder is used
for drying the paper; the other quarter is taken up by the cleaning and polishing
apparatus, which must always be in as accessible a position as possible, in order
to facilitate the changing of doctor blades, wire brushes, etc.

The principal piece of apparatus for keeping the cylinder clean is the ordinary
doctor, preferably a Vickery, and there are usually two of these. One is fitted
in position just before the cylinder comes in contact with the web at the press
and the other one immediately after the paper has been pulled off the cylinder.
This latter doctor removes the end of paper which comes over first, prior to
its being wound on to the reel.

Between these two doctors may be fitted all kinds of cleaning devices to
suit the individual tastes and fancies of the paper-maker.

Another effective burnisher is a stiff wire brush, made by winding carding
cloth round a wooden roll, and nailing it in position. The roll is driven at a
high speed (250 revolutions per minute), the wire bristles cleaning and polishing
the surface of the cylinder.

A wooden doctor covered with a piece of damp felt is also used, and this is
very effective in damping the fluff* and dust which dry on to the cylinder, thus
enabling the steel doctor blade to remove them. The felt may be frequently
changed if necessary 7 .

A ‘water’ doctor is also very effective; it consists of a perforated pipe, which
forces wet steam against the surface of the cylinder immediately in front of
the iron doctor blade.

Apart from these devices for keeping the cylinder clean while it is in motion,
it is also necessary periodically to grind it or buff it, or it may be cleaned with
emery powder and oil. For grinding it, a perfectly true iron roll is fitted in
position in place of the press roll, and driven at a higher speed than the cylinder
by means of very tight belts in the presence of water.

This is a risky business, for unless the belts are kept very tight all the time,
the motion of the cylinder will be bumpy and will result in flat places being
formed, which will show on the surface of the paper later.

The best way to carry out this work is to buff the cylinder with proper
buffing apparatus.

When the cylinder has to be stopped for any special cleaning, it should first
be allowed to cool down, as the dirt is then more easily removed.

MODERN PAPER-MAKING

246

If soft water is available for paper-making, it seems to be much easier to
keep the cylinder clean than if the water is very hard.

The papers made on M.G. machines are very varied in character and uses,
and the following are some of the most common: Pressings, manillas for
envelopes, litho papers for poster work, krafts, sulphite bag papers, common
cap and cheap wrappings, tissues and sealings.

The machine described is the commonest type, but there are many varia¬
tions and modifications, of which the following are a selection:

1. An ordinary Fourdrinier wet end, followed by several small drying
cylinders, which partly dry the paper before it is led to the large cylinder.
The overfelt of this machine receives the paper from the last of the small
cylinders, which are not usually very hot, and takes it to the cylinder press.
The felt is damped just before the press nip.

This arrangement enables higher speeds to be run, as the big cylinder is
relieved of some of the drying, and it does not have any detrimental effect
upon the high surface which is obtained on the paper.

2. The ‘lick-up’ machine may have either a vat or Fourdrinier wet end,
but it does not possess a wet press. Instead, the wet felt passes round the top
couch rolls, and the web is transferred to it at the couch, carrying it to the
cylinder press and depositing it on the cylinder. The felt acts as wet felt and
overfelt, and is usually passed through a washer to cool and clean it on its return
journey from the cylinder to the couch roll. On this type of machine the under
side of the web sticks to the cylinder and receives the polished surface.

If the wet end is of the vat type, as described in the following section, the
web is made on the wire drum and transferred to the wet felt and thence to
the cylinder.

3. A combination of both the above-mentioned types makes duplex paper
in the following manner: The Fourdrinier wire part for ms one side of the
sheets and the other side is made on a cylinder mould situated above the wet
end. The second web is led by a felt into the couch of the Fourdrinier wet
end and the two webs are united, couched and pressed together at the same
time, thus forming a duplex sheet or thin board. They are subsequently dried
on the cylinder in the usual way.

4. Heavy boards may be made by having a battery of cylinder moulds
exactly the same as those for the ordinary board machines, as described in
the following pages.

It will be readily understood that the drying power of an M.G. machine
is very li m i t ed compared to some Fourdrinier machines with their long double
tiers of drying cylinders. For this reason it is usual to work the cylinder very
hot mdeed, as hot as the paper can stand without blistering.

BOARD MACHINES

247

Except in the case of very thin papers, high speeds cannot be attained, and
for this reason better prices are usually obtained for M.G. papers than for
similar qualities supercalendered or unglazed.

The Board or Vat Machine

This important paper-making machine is very different from the Fourdrinier
machine in the manner in which it makes or forms the web of paper, but it is
the same as the Fourdrinier machine from the presses to the calenders.

The simplest type is the single-vat machine, which has no drying cylinders
and is used for making very thick boards. It works as follows:

The pulp is pumped from the stuff chests to the stuff box and thence to
the strainers; it then flows to a vat or trough, in which revolves a bronze cylinder,
hollow in the centre and open at the ends, and with a covering of fine-mesh
machine wire cloth over a stout backing wire.

The construction of the cylinder is much the same as that of a wove dandy
roll. As the cylinder revolves about two-thirds immersed in the stuff, the
water in which the fibres are suspended rushes through the meshes of the wire
in the same way as it runs through the wire on the wet end of a Fourdrinier
machine. As, however, the meshes are too fine to allow the passage of the
fibres, the latter cling to the surface of the wire drum, and thus a t-hm film of
fibres is formed on the revolving mould.

As the drum moves round towards the top, the film of stuff is lifted clear
of the stuff and water in the vat, and more water drains away. When the wet
film reaches the highest part of the circumference of the roll it comes in con¬
tact with an endless travelling wet felt. As the web touches the wet felt it
is couched by means of a felt-covered wooden roll, which presses the travelling
felt against the surface of the drum. In this way the wet film of pulp is picked
up from the wire surface and adheres to the felt.

The felt carries it along to squeezing or press rolls, where it is relieved of
as much water as possible. The web sticks to and is wound round and round
the top press roll until a sufficient thickness has been formed. This is indicated
automatically by the ringing of a bell. It is then cut off by hand, laid in a pile,
pressed and finally dried by hot air.

The resulting paper is known as a board, and such boards are used for
boxes, panels, suitcases, etc. Larger machines are provided with drying
cylinders and calenders for drying and glazing the board as it is made. By
using two stuff chests, two sets of strainers and two vats, a board can be made
of two different qualities of colours—that is to say, it may consist of common
brown paper stuff on one side, and have a white top side made of sorbite

MODERN PAPER-MAKING

248

pulp, or of stock of any colour. Such papers are known as duplex, which
means that they are two-sided or two-ply. The width of the web which is
to be made on the drum is regulated by stopping up the meshes of the wire
by tapes, which may be wound on at either side. This obviously has the effect
of closing the meshes of the wire cloth, so that water cannot run freely through
and cause the formation of a web of fibres.

The water which passes through is run away to a back-water box, whence
it is pumped back again for further use in furnishing the beaters. The thick¬
ness of the web which will form on the cylinder is obviously limited, for, as it
becomes thicker, less and less water can pass through, and so the number of

[Banning and Seybold

Fig. 103 .-Sheet-forming Vats of a Multiple-Vat Board Machine

fibres deposited becomes less. The thickness of the various webs which form
the board is regulated by the consistency of stuff going to the vat, and by the
speed of the machine.

In order, however, to produce a thick board suitable for making folding
boxes, or a paper which has to be very thick and stiff, the number of vats and
making drums may be increased to four or even six or eight, and all the webs
pressed together to form one thick sheet (Figs. 103 and 104).

In this way boards may be made with a different-coloured surface on each
safe and with a middle’ of entirely different colour and quality. To do this
it will be seen that different sets of beaters will be required, also a number
of stuff chests, mixing boxes, and strainers, to correspond with the number of
qualities of staff to be used to compose the finished board.

BOARD MACHINES

249

Each chest requires a separate stuff pump, and where stocks of different
colours are being used, separate back-water pumps and tanks are needed to
pump back and store the water from the vats for the beaters or mixing boxes.
From the foregoing it will be gathered that the wet end of a multi-vat machine
is a somewhat complicated and cosdy affair.

[Mtf&ft, Scott md Co. Ltd.

Fig. 104— Vats and Couch Rous op a Muiukb-Vat Boabd Machine

To take the case of a four-vat machine: The vats are arranged dose together,
and in rotation, the first one to deliver its web of stuff to the wet felt being che
one nearest the presses, and so on in a reverse direction towards the strainers.
When the fourth web has been picked up, the felt will be fairly heavily loaded,
and here it turns round a roll and travels back towards the presses of the machine
carrying the four-ply web on top and immediately above the vats.

250 MODERN PAPER-MAKING

The presses at first are small and fairly light, and are placed in rotation,
in steps, leading down to the main heavy press roll. These small presses are
generally called ‘baby’ presses (Fig. 105), and they serve to squeeze and in¬
corporate the four webs of paper together gradually before the main pressure
is applied by the heavy press, which is usually of granite.

The ‘baby’ presses are of wood or metal, and are usually 60m five to seven
in number; the web passes straight through them and is not reversed. At the

[H.J. and A. Couhhurst, Ltd.

ftc. 106 . A Battery of Chests for supplying Stuff to the Vats of a Muitepie-Vat Board Machine

‘baby presses another felt comes into action and is in contact with the upper
side of the paper during its passage through t h*™

The wet rat carries the web right to the main press roll; this wet felt passes
tfaxMagfr a felt washing-tank and squeezing rolls before returning to the vats
to pick up a fetoher web of paper.

£ The majority of papers made on board machines are either ‘duplex’ or
triplex, the former having, as a rule, a face of pure sulphite and a back of a

BOARD MACHINES

251

[Courtesy IValmshys (linry) Ltd. 1 aid Thiiimv lUwd Mills
107.— Stackhd Dbying Cylindhh*, Calhndhrs and Rhel-up of a Large Hoard Mac.iiinii

252

MODERN PAPER-MAKING

mixture of mechanical pulp and waste papers, the proportions being 25 per cent
face and 75 per cent backing.

In the drying of boards it is not the general practice to use dry felts, and on
some of the big modem machines, in order to save space, the drying cylinders
have been arranged in tiers, five or six high. We believe that this practice
originated in America, but we are not at all certain that it is an unqualified
success.

It is almost universal practice to combine a system of hot air with the dry
cylinders, in order to absorb the large amount of moisture given off into the
pockets between the tiers of the cylinders, and between the cylinders themselves.

On many board machines the paper is calendered on machine calenders, and
then cut at the end of the machine, instead of being reeled and cut separately.

This is not, as a rule, a difficult matter, as board machines run at a compara¬
tively slow speed when compared with some modem paper-making machines,
although, of course, the output in weight may be very high.

In the case of triplex boards the usual furnish is face and backing of the
same material, such as sulphite, with a middle of poorer quality, such as straw-
boards and mixed waste papers.

This arrangement necessitates the use of only two sets of beaters and chests,
a great saving of space and power. The usual ‘finish’ is a water-finish put
on with chilled iron rolls in two tiers on to which water is led from a trough.
Soap is usually added to the trough to prevent rusting. The paper passes
from the second stack moist, and the finish is put on during its passage through
the two remaining stacks. Four stacks of calenders have therefore to be
provided.

The ‘Mould’ Machine

The so-called mould machine is used for making imitation hand-made
papers, and papers made on these machines are the nearest approach to hand¬
made paper which has yet been achieved by mechanical means.

The paper is, however, inferior to genuine hand-made paper.

It is possible on- this machine to make paper with a deckle edge all round
die sheet, and this fact alone is liable to mislead those who are not experts into
mis ta king the mould’ made for the real hand-made sheet.

Great secrecy is observed in mills possessing these mould machines; the
wet end, consisting of strainer, vat, wire-covered cylinder and presses, is placed
in a locked room, and the wet web is led on a felt through a slit in the wall
into the drying room.

The mould or cylinder is just like a large-diameter dandy roll, and it
revolves partly submerged in the stuff in the vat.

MULTIPLE WIRE MACHINES

253

This roll has the devices and lettering, etc., fixed to its woven-wire cover,
and as it revolves it picks up a layer of stuff, thick where the cover is plain cloth,
and thin where the device wires are placed.

The wet film of stuff is couched off at the top and taken on a felt to the
presses in exactly the same way as the stuff is couched off the drum of a hoard
machine.

If the paper is to be made in single sheets, strips of wire are placed round
and across the roll to fix the dimensions of the sheet. No stuff, or very little
stuff, adheres to this wire, so that when the wet sheets have been pressed they
come apart, or are easily pulled apart by hand, leaving a ‘deckle’ edge.

The machines are so arranged, and fitted with four or five or more drying
cylinders, that the paper may either be dried at once by steam, or may be
removed from the felt by hand as wet waterleaf and dried by air in a loft.

The Richardson-Key expanding cylinder ‘mould’ is sometimes used on
these machines, owing to the ease with which a new wire cloth cover may be
fitted when changing from one water-mark or size to another. This patent
‘mould’ enables a great saving to be made in the stock of ‘moulds’ or drums,
which would otherwise have to be carried.

Two and Multiple Were Machines

In recent years increasing use is being made of Fourdrinier machines with
more than one wire. The object of this is twofold. In the first place it enables
a paper to be produced with two top sides on which to print. This is achieved
by running together the under or wire sides of two thin papers, leaving the
two top sides outermost. It is thus possible to produce a printing paper with
exactly the same surface on each side of the sheet. The method is also applied
to make paper of very great strength, and two or more wires may be used
for this, givin g a two- or three-ply sheet. Some mills have been doing this
for a long time, but the practice has not been general. More frequently a
Fourdrinier wire has been used in conjunction with a vat such as that used on
a mould machine, but now that the difficulties of combining the two sheets
at the press have been overcome, the use of two complete Fourdrinier wire
parts to form the sheets is quite common practice. The sheets arc brought
together at the press, where they become homogeneous and pas on through
the second and third press and across the dryer as one solid sheet.

It is not, of course, possible in this case to make satisfactory laid or water¬
marked sheets. .

CHAPTER XVI

THE MANUFACTURE OF NEWSPRINT

Production Figures—Fibrous Raw Materials—Non-Fibrous Raw Materials
—Handling of Raw Materials—Water—Preparation of Alum,
Loading, and Dyes for Addition to Stock—Preparation and Pro¬
perties of Stock—Strainers and Slice—The Wire Part—The Press
Part-The Dryer Part-Finishing-Future Trends of Newsprint
Manufacture

In the descriptions of paper-making practice given in other chapters
(notably in Chapters XI, XII and XIII), there is a good deal of information
which is applicable to the manufacture of newsprint. Nevertheless, since
newsprint-making has tended to become increasingly specialised— if only
because of the ever-growing necessity for reducing conversion costs by the
development of larger output machines running at high speeds—it will be
useful in this chapter, not only to give a brief general discussion of the technique
of this branch of paper-making, but also to draw attention to various aspects
of it which are peculiar to newsprint. The subject is treated primarily from
the viewpoint of the manufacturer in this country who does not prepare his
own pulp, but purchases it ready-made. Some details of the processes for
pulping wood for making newsprint are, however, given in Chapter V (see
pp. 55,61, 68 and 69).

Production Figures —World production of newsprint in 1938, the last com¬
plete year uninterrupted by war, was 6,710,000 long tons. The greatest
quantity yet manufactured in a single year was 8,020,000 tons, which was
the world output for 1937. The world production of paper of all kinds for
1937 was 20,500,000 tons; thus newsprint accounts for about 40 per cent of
this total.

These figures give some idea of the importance and size of the world’s
newsprint industry.

• Even more striking, perhaps, is the rate at which the annual production
of newsprint has increased. In Canada, for instance, to take an outstanding
example, the production in 1913, the year immediately preceding the last
war, was 310,090 tons. In the peak year of 1937 the production rose to
3,25<yxx> tons—? tenfold increase. Enormous expansions of this kind have

NEWSPRINT

255

been made possible not only by building new mills, but also by increasing
the size, the speed, and the efficiency of the machines used to make this class
of paper. Newsprint manufacture has, in fact, been largely responsible for
leading the industry with ever wider and faster machines. This, of course,
is a logical development, since newsprint must always remain one of the cheapest
grades of paper made, and it is also required in quantities that far exceed any
other class of paper.

The majority of modem Fourdrinier newsprint machines in operation to¬
day are designed for maximum paper widths ranging from about 200 to 250
inches, but a notable exception is the world’s largest machine, which makes
paper 304 inches wide. This is an all-British machine operating in England.

The most common speeds of modem newsprint machines range from about
1050 to 1250 feet per minute, while the highest authentic speed is in the neigh¬
bourhood of 1400 feet per minute. Machines of this kind naturally produce
a lot of paper. The output of the 304-inch machine, for example, when making
super-calendered paper of normal substance (55 grams per square metre),
reeled and ready for the customer, exceeds 200 tons per 24 hours.

The fibrous raw materials for newsprint are prepared exclusively from
wood, and it takes, very roughly, a cord of wood to produce a ton of finished
newsprint; a cord being a pile of logs, all lying parallel to each other, 4 feet
high, 4 feet wide, and 8 feet long. A cord of wood corresponds, very ap¬
proximately, to eight trees having an average height of usable trunk of about
50 feet, and an average diameter of about 18 inches. Calculating from the
basis that a typical pre-war daily newspaper of about sixteen pages weighed
4 oz., the amount of pulp required for a circulation of two million copies was
over 200 tons (air-dry) per day. This means that rather more than 800 trees
had to be cut down every day to satisfy the requirements of only one of the
leading newspapers published in this country.

Altogether, the average daily consumption of newsprint in the British Isles
during 1938 was 3400 tons, the consumption for the year having reached the
total of 1,241,000 tons. The corresponding annual consumption per head
of the population was about 60 lb. It is interesting to compare these figures
with those for North America (Canada, U.S.A., and Newfoundland). The
total consumption for the same year, 1938, was 3,088,000 tons, which gives
a daily consumption of 8500 tons. Although these figures are two and a half
times greater than the figures for this country, the consumption per head in
North America was somewhat lower, being about 53 lb. per year. During 1938
the British Isles and North America together accounted for 62 per cent of the
world production of 6,710,000 tons.

These enormous tonnages give some idea of the inroads being made into

256

MODERN PAPER-MAKING

the forests of the world to satisfy the demand for newsprint. The question of
the continuity of wood supplies has, as a result, given rise to some anxiety,
and from time to time it has been concluded that the world is in sight of a
serious shortage. Although these scares appear to have been unjustified, they
have at least drawn attention to the need for organized schemes of wood¬
cutting and afforestation to ensure that, with steadily increasing demands, the
wood supply is maintained. Nearly all the major wood-pulp producing
countries, and especially the European ones—Norway, Sweden, and Finland—
have their forests continuously surveyed, in order to check consumption
against the annual rate of growth. As a result the necessary afforestation
measures are enforced.

Fibrous Raw Materials.—By far the most common variety of wood used
for newsprint manufacture in Europe is spruce (see p. 50). This wood is
converted both into groundwood (mechanical pulp), and also into sulphite
pulp. Very exceptionally sulphate pulp is used. Groundwood is the most
inexpensive fibrous material (other than waste paper) available for newsprint,
but apart from this advantage it is particularly well-suited for newsprint pro¬
duction. It has the necessary absorbent properties to take the printing-ink
well, and it has good opacity. In fact, it has often been said, quite rightly,
that to obtain the best printing results it would be preferable to use ground-
wood alone. In practice, however, a proportion of pulp, longer fibred than
groundwood, is necessary, mainly to help the immature sheet to have the
requisite strength to be carried on its journey along the paper machine, from
the couch, through the presses to the drying cylinders. The pulp most
commonly used for this purpose is known as news quality, or strong, sulphite
pulp. Occasionally sulphate pulp is preferred to sulphite pulp, but its selection
is justified only on those rare occasions when it is cheaper than sulphite pulp,
due to exceptional market conditions, or because a newsprint mill is in close
proximity to a sulphate mill where supplies of pulp may be available in slush
form at a competitive price. Actually sulphate pulp has the advantages of a
somewhat longer fibre than sulphite pulp, and it is free from resinous sub-
tances. On the other hand, even in the palest grades, it is us ually rather
darker in colour than strong sulphite pulp, which is an objectionable fe at ure
if bright, nearly white shades are required, as is mosdy the case nowadays in
this country.

At the present time the proportion of chemical pulp used with ground-
wood for a newsprint furnish ranges from about 10 per cent to 20 per cent.
Some years ago the amount commonly used was as high as 30 per cent, but,
partly due to the need for retrieving some profit out of the ever-decreasing
seSing price of newsprint, and partly due to a growing understanding of the

NEWSPRINT

257

importance of groundwood for giving good printing qualities, the sulphite
percentage has been steadily reduced. Improvements in groundwood manu¬
facture, resulting from scientific research, and also the development of reliable
methods of pulp evaluation, have helped to make the reduction in sulphite
content practicable.

Non-Fihroiis Raw Materials— Mention must be made of the two other raw
materials that occur in appreciable proportions in newsprint. They are loading
and water.

Loading is added to newsprint to increase ink receptivity, to help to give
satisfactory opacity, and to fill up inter-fibre spaces so that a smoother surface
may be obtained; it also helps to make a sheet of paper as economically as
possible. China clay is the most common loading for newsprint, although in
some American mills calcium carbonate is used, because china clay is expensive;
the reason being that it occurs only to a limited extent in the United States, and
a good deal has, therefore, to be imported from Cornwall. In one American
mill, calcium carbonate is made from carbon-dioxide recovered from the flue
gases of the boiler plant. In other mills, loading is not used at all, because
of the expense of transporting it to the mill site.

The cheaper grades of clay, even down to mica clays, are quite satisfactory
for newsprint, provided the abrasive grit content is not too high. This is an
important point to watch, otherwise excessive wire wear may result. The
colour of the clay, unless it is exceptionally bad, has no appreciable effect on
the shade of the finished newsprint paper, and it is, therefore, only a secondary
consideration. The amount of loading carried may range from 2 or 3 per cent
up to 12 per cent or more, depending on the properties desired, the basis weight
of the paper, and other factors.

The last of the four major constituents of newsprint, water, is the cheapest,
but it is by no means unimportant, neither is it put in primarily for reasons of
economy. Newsprint devoid of water would, like any other paper, be of
very inferior quality. The presence of the correct amount of water, which
should be between about 8 per cent and 10 per cent, is helpful in obtaining
a satisfactory finish; it gives paper a mellow handle (if it is too dry it will be
harsh and brittle; if too wet it will be soft and flabby); it minimises the possibility
of troubles due to static electricity during printing, and it reduces the tendency
to cockle during transport and storage.

The analysis below gives the proportions in which the four constituents
mentioned occur in a typical sample of newsprint.

Groundwood . 70% or 84 expressed as a percentage of the

Sulphite pulp . 13% or 16 % J fibrous furnish only

China day . 8%

Moisture. 9%

MODERN PAPER-MAKING

258

Handling of Raw Materials .—Raw materials for newsprint are required in
large quantities, and therefore up-to-date methods of handling and transporting
are an essential part of a modem mill. It is of prime importance that the site
should have good rail and water transport facilities; and, in addition, road
transport is essential, as it is used almost exclusively for the distribution of paper
to customers in this country. It is also used for conveying general stores,
machinery and the less bulky raw materials, such as dyestuffs, to the mill.

A well-located newsprint mill, producing, for example, 3000 tons of paper
per 51-day week from four modem machines, will consume approximately
4500 tons of moist mechanical pulp, 500 tons of air-dry sulphite pulp, 300
tons of china clay, and 2000 tons of coal per week, all of which will be
delivered by ships carrying anything from rooo to 5000 tons or more
of cargo. These ships come alongside the mill wharf for unloading. Coal
and china clay are grabbed out by the wharf cranes and discharged direct into
the bunkers provided. Pulp is lifted from the ship’s hold, usually four or five
bales at a time, on to tracks belonging to the mill, and the bales are tidily stacked
subsequendy, using gantry cranes.

Coal is conveyed into the mill continuously by bucket or belt conveyors,
and clay is usually slurried in a building integral with the clay bunker, the slurry
being then available for pumping to the point at which it is mixed with the
stock in the mill. Pulp is reclaimed from the stacks by the mill gantry cranes
and taken to the beater floor, either by electric trucks or in some cases direct
by crane.

The handling of newsprint raw materials has been specially mentioned in
order to emphasise the important point that with only a relatively small
.margin between raw material costs and the selling price of the finished product,
conversion costs, which of course include the cost of handling materials,
must be kept to the most economical level possible. Newsprint to-day is
essentially a cheap product, mass-produced in enormous tonnages. Every
effort must, therefore, be made to ensure that labour is not wasted by inefficient
methods of handling materials.

Water .—The water supply for processing the paper is obtained usually from
wells, although in some cases it is drawn from rivers. River water often re¬
quires rather elaborate flocculation and filtration treatment, but well water has
the advantage that it rarely needs any treatment at all. The quantity required
for all paper-making purposes will be of the order of 12,000 gallons per hour
per m a chin e, which, at 6 tons per hour production per machine, is 2000 gallons
of water per ton of paper manufactured. Of this quantity the? dryers will
evaporate about 2500 gallons per hour, the remainder being necessary to make
up incidental nan-recoverable losses, such as hosing floors, machine wash-ups.

NEWSPRINT

259

[Stothert and Pitt , LtdBath

Fig. 109.—2f-ToN Cranes used for unloading Pulp, Coal, and China Clay direct from

Ocean-Going Ships

The pulp bales are loaded on to trucks for subsequent stacking by gantry cranes

z 6 o

MODERN PAPER-MAKING

and water drained away from the presses. For safety a supply should be avail¬
able considerably in excess of this rather economical quantity of 2000 gallons
per ton. It should, however, be the aim to keep the water consumption on the
machines to as low a figure as possible, not so much because water may be
difficult to obtain, as because extravagance will almost invariably be linked
with excessive fibre losses. Modem newsprint manufacture, calls essentially
for a closed back-water system, which means that as large a quantity as possible
of the water should be used over and over again. Any water added in excess
of that subsequently removed by the machine (principally at the dryers) will be
wasted water, and unless an efficient fibre recovery system is available, the loss
involved is likely to be serious. With an adequately balanced water system,
a recovery unit is not, as a matter of fact, essential.

The quality of the water used for the actual paper-making process, as distinct
from the boiler plant, is not of material importance. It should, of course,
be clear, and free from suspended matter, but it may be very hard without
giving any serious paper-making troubles. Indeed it is contended in some
mills that hard water has certain definite advantages over soft water, such as
helping to prevent pitch troubles on the machines. A typical hard water, quite
satisfactory for newsprint manufacture, is as follows:

so 4

Hardness, permanent
n temporary

9.7 parts per ioo 3

f OOO

3-2 „ „

9-<S „ „

10.0 „ „

27.2 ,, „

Preparation ofAlum, Loading, and Dyes for Addition to Stock .—The most efficient
practice in newsprint mills to-day demands that all the auxiliary materials,
loading, alum, and in many cases dyestuffs, should be added to the stock in
suspension or in solution.

China clay, as already mentioned, is mixed into a slurry with water, in the
clay-mixing house, which should be adjoining the clay store. The clay is
mixed in tanks, fitted with the necessary agitator gear, to give a concentration
of about 2 lb. per gallon. From the mixing tank the slurry is pumped
through a screen, usually made of old machine wire, to a storage tank- The
slurry must, of course, be continually agitated to prevent sedimentation. In
some installations it is found convenient to have two or three mixing tanks,
each feeding one large storage tank. From the storage tank, the slurry is
pumped to a small service tank in the mill, which supplies the machines by
gravity. To prevent sedimentation, slurry from the service tank overflows
continuously, the surplus bang collected in a receiving tank, from which it is
pumped back to the storage tank in the clay-house. The slurry is added to

NEWSPRINT

261

the newsprint stock usually at the Trimbey or other form of proportioner.
Alternatively it may be measured in boxes of suitable capacity, and added to
the beaters.

Alum, either in the form of kibbled 17 to 18 per cent quality, or as 14 to
15 per cent slab alum, is dissolved in tanks having a perforated false bottom
fitted quite near the top. The alum is loaded on to the false bottom, and water

LS [Bell and Robertson, Ltd * Aberdeen

Pig. ixo.—Typical Clay Slurrying Plant, showing Two Mixing Tanks from which the Slurry
hows by Gravity, through a Direct-Driven Rotary Strainer, to the Storage Tank

is run in until the solid alum is just covered. As the alum dissolves, the dpnsf-r
solution Ms to the bottom of the tank, thus giving some natural circulation
which helps to speed up the dissolving process. Sufficient alum is added to-
the tank to give a solution containing 2 to 5 lb. per gallon. A useful check
of the concentration can be had by testing the solution with a Twaddell
hydrometer.

From the m i xin g tank, alum flows by gravity to the storage tnnV ) from
which pipe lines take it to the machines. The feed may he arranged
continuously at the breakers or heaters, or continuously at {fie pK>pa$M»||^

262

MODERN PAPER-MAKING

In some miUs it has been possible to dispense with alum altogether, since it is
now recognised that size is not required in newsprint. In general, however,
troubles such as sticky presses are likely to arise if the stock is not kept down to
a pH value of about 5.

Alum solution is a very corrosive liquid and must be handled in lead-lined
or other suitably protected tanks and pipe lines.

The dyes used for newsprint are almost exclusively basic dyes because they are
cheap, they are bright colours, they dye directly without difficulty and the fact

[Waimskys (Bury), Ltd.

Peg. iii. Breaker and Beats* Floor for the Preparation of Stock for Two Modern Newsprint

Machines

that they are fugitive is of no consequence. In modem mills they are dissolved
in bulk, and added to the stock at the proportioner. This is a elean and con¬
venient method of dyeing, as the beater floor is kept completely free from dyes,
and shades can be more quickly and easily controlled the nearer they are a dded
to the machine itself.

and Properties of Stock .—The preparation treatment of baled pulp
WWg newsgrint stock consists essentially in breaking up the laps and then
the fibres so that they are fina ll y all separated from one another
^ to on to the wire of the paper machine.

mam#
There is

NEWSPRINT

263

The method of breaking that is still the most popular is to use the common
type of breaker having a roll fitted with bars that are saw- or wavy-edged.
The bars are usually equally spaced round the roll about 18 inches apart, and
there is no bed-plate. The roll operates in a fixed position about 6 inches above
the bottom of the breaker trough, and it is not adjustable or counterbalanced
like a beater roll. Breakers of this type for newsprint stock are built to hold
about 1 ton (air-dry weight) of pulp at a consistency of 5 to 6 per cent, the
capacity of the trough being about 4500 gallons. Bales are fed by hand, a
few laps at a time, into the breakers just in front of the roll, the filling opera¬
tion taking altogether about 10 minutes. After a total period of 20 or 30
minutes, including filling in, the stock is sufficiendy broken up to be dropped
to the breaker chest.

[Sturtepwt Mill Cc., Boston, Mass .

Fig. 11 2 . —Sturtevant Bale Puieer

Accepted stock has to pass through the semicircular perforated screen plate

Although this method of breaking appears, on the face of it, crude and
unscientific, and represents no advance, other than in the capacity of the breaker,
over methods that have been in use for very many years, it compares surprisingly
well in labour and power costs, and in capital expenditure, with proposals
made from time to time with a view to modernising the procedure and reducing
the amount of man-handling required.

Among these proposals may be mentioned the Sturtevant pulper, which is
illustrated in Fig. 112. With this equipment, bales are mounted on a conveyor
which carries them continuously to a revolving drum fitted with daws that
tear at the surface of the pulp and effectively break it up. A shower of back¬
water plays on the surface where disintegration takes place, and the resulting
slush fells below into a breaker chest.

MODERN PAPER-MAKING

264

Another system, known as the Liebeck fihrator, is an attractive alternative
to the generally adopted breaker method. In this arrangement, bales are packed
together in line on a conveyor, but instead of being forced by the moving
conveyor direct against a disintegrating roll, the pulp falls, bale by bale, into
a large oblong concrete breaker chest capable of holding 5000 lb. of stock
at 3 per cent consistency. The chest is fitted with a horizontal shaft, on which
are fitted large disintegrating propellers, and as the bales are fed in, they fall
some 10 or 12 feet either on to the shaft itself, or on to stationary horizontal
concrete baffles which protea the propellers. This heavy fall helps to split
the bales into laps, and then the propellers thrashing round are very effective
in breaking the laps down to slush form. These breakers require about 30
minutes, including loading time, to treat the stock. *

Both the Sturtevant whole bale pulper and the Liebeck system are able to
handle pulp that is difficult to disintegrate rather more satisfaaorily than con¬
ventional breakers. Thus, the Liebeck breaker is able to handle frozen pulp
without any prior hacking and man-handling of the bales to separate the laps.
The Sturtevant pulper has been employed successfully to break up dry Kraft,
a task which is very difficult in an ordinary breaker. Both these methods of
pulping, however, suffer from the disadvantage that labour is still required to
load the pulp on to the conveyors, and to remove the baling wires. Perhaps
for this, among other reasons, these newer methods have not displaced the
breaker system to any appreciable extent for newsprint.

An arrangement for the breaking and preliminary treatment of pulp that
has operated satisfaaorily in several news nulls in this country has been to have
for each machine, making about 150 tons of paper per 24 hours, a battery of
three i-ton breakers for handling the groundwood, one i-ton sulphite breaker
and two i-ton sulphite beaters. The beaters, unlike the breakers, are fitted
with bed-plates, but they do very little real beating, and chiefly h el p to dis¬
integrate the pulp further. The groundwood breakers operate independently
and discharge the stock into a common breaker chest. The sulphite breaker
may be arranged to discharge the stock direct to a pump which transfers the
stock to one of the two beaters, where the pulping treatment is continued for
about an hour. The sulphite beaters then discharge the stock into a sulphite
stock storage chest.

Groundwood and sulphite pulp are thus, in modem practice, broken and
dkmtegrated separately in the early stages. The breakers, in each case, are
fed with back-water obtained by gravity from the back-water storage tank, and
’when did broken-up stock is let down into the storage chests, additional back¬
water is added to wadi down the rather thick 5 to 6 per cent stock. This
wadshg dilutes the stock to about 3 per cent, and in order to keep the

NEWSPRINT

265

concentration as constant as possible, the chests are allowed to fall always to
the same level before the next breaker-full is dropped. The addition of
dilution water is continued via the breaker until the stock-chest level has been
brought up to a predetermined level to give the required concentration of
3 per cent

Storage chests for both sulphite and groundwood stock are usually rather
long and narrow, the width being roughly the same as the height (see Fig. 106).
They are fitted with a horizontal shaft to which are attached paddles, or pro¬
pellers, to provide the necessary agitation to prevent sedimentation or flota¬
tion, and to help in some small way in the soaking and disintegrating process.
For the sake of cleanliness, the tanks are permanently closed in with a manhole
at the top through which access can be had for inspection and repair purposes.
The capacity of these chests is usually sufficient, together with the refiner and
machine chests, to give about 4 hours’ supply of stock to the machine. The
greater the capacity the better the opportunity there is to get the stock
thoroughly mixed, which helps to maintain a uniform consistency. It also
gives some margin in the event of any breakdown occurring in the breakers.
On the other hand, a large chest-capacity makes it difficult to make any rapid
changes of furnish, if this should be necessary.

The stock from the breaker and beater storage chests may be refined
separately, then mixed, by means of a proportioner, in the ratio needed to
give the desired percentage of sulphite. After mixing, the stock, in most
installations, is refined again, and is then ready to be fed to the mixing pump
to provide the dilute stock for the breast box.

No hard-and-fast rules can be laid down as to the exact flow-system needed
to give the best refining results. Normally two or three refiners, each taking
about 250 horse-power, will be installed for a machine making 150 tons of
paper a day. From the evidence available, it seems that two refiners should be
enough for the work to be done.

The purpose of refining, so far as newsprint is concerned, is p rimarily to
complete the disintegration of the stock, which, after breaker treatment only,
is full of undisintegrated dots of pulp. Refiners are able to dear these away
completely. Groundwood changes little in freeness, or other characteristics,
on bang refined, although sulphite pulp, especially if it is added to the breakers
in an air-dry condition, may increase in strength considerably when refined.
This increase does not, however, seem to be of primary importance, partly
because the percentage of sulphite used nowadays is so low that its contribution
to the strength of the finished sheet is rather small, and partly because the primar y
function of sulphite is to make full use of the long slender fibres to i&k?
strength to the immature sheet of newsprint, thus hdping it to widKt^^m

266

MODERN PAPER-MAKING

stresses set up in passing from the couch to the drying cylinders. Refining
helps to some small extent to control the wetness of the stock on the wire,
but there is no doubt that groundwood is rather unresponsive to refiner treat¬
ment, and therefore it is more important that the right quality of groundwood
should be obtained from the pulp mill, rather than that any attempt should
be made to try to modify its quality by treatment in the paper mill.

The correct proportioning of sulphite and groundwood stocks is dependent
upon the maintenance of a uniform consistency, and some reference has already
been made both to the usefulness of large chests, and also to the importance of
dropping breakers regularly and diluting the stock methodically in order to
avoid excessive variation in consistency.

It may be found desirable, in addition, to control the stock automatically-
using one of the many types of consistency regulator available for the purpose.
All these regulators depend, for their operation, on the stock changing in
viscosity, as the consistency changes, and although this relationship is rather
variable, depending, among other things, on the kind of pulp and the treat¬
ment it has received, a well-designed and carefully constructed regulator can
give a very satisfactory measure of control.

The separately prepared groundwood and chemical pulp stocks are mixed
by means of a proportioned of which a number of types and designs are
available. These depend usually on the provision of a constant head of each
kind of stock by pumping up to a receiver having an overflow for stock to
return to the storage chest. From the constant head, or constant level com¬
partment, the rate of flow of the stock is controlled by a revolving variable-
speed paddle-wheel, as in the Trimbey proportioned or by a rectangular weir
having an adjustable width, as in the Tidbury proportioned The two pro¬
portioned stocks are collected together in a receiver and conveyed by gravity
to the mixed stock chest, from which the stuff is pumped for further refining;
and consistency control, finally being discharged into the machine chest ready
for the mixing pump.

In modem mills, the proportioner is the place where, in addition to adjusting
the ratio of groundwood to chemical pulp correctly, loading, dyes, and some¬
times alum are added, in the form of a suspension or solution. As in the case
of pulp, the rate of flow may be controlled by a constant head of the liquid,,
coupled with a feeding paddle rotating at the rate required to give the necessary*
does. A more recent and very satisfactory method of obtaining a visual control,
ofafomflow is to use a rotameter. This type of flow indicator consists of a very
gradually tapering glass tube. A cone rises or fills in this glass tube, according
to, the quantity of liquid that has to escape between it and the glass tube; the
gteafer the ikw the higjber the cone must rise to take advantage of the

NEWSPRINT

taper to give the required larger clearance between the glass tube and the cone.
Rotameters are obtainable already calibrated over the range of flow-rate
desired.

From the proportioner, then, the stock is complete with colour, loading
and alum, and after further refining it is ready for the machine.

In dealing with die correct furnishing and preparation of the stock for
making newsprint, stress must be laid on the importance of selecting pulps
which are suitable for the purpose, and on the need for keeping out of the
system foreign material likely to affect adversely
the quality of the sheet, or cause breaks on the (©)

paper machine. Methods of evaluating pulp
quality have advanced very considerably during
the past few years, and in modem newsprint mills // i

the testing of the quality of shipments is an im- [j gfflj

portant part of laboratory control work. The j K&l i

tests made include fireeness determinations, the I l
estimation of shive content and the preparation j im \ L
and examination of laboratory sheets. Detailed j - ' iLjj g

information about methods of this kind is avail-
able in the technical literature and in the reports j X.11 '

of committees which have made a special study , ( \J

of the subject. '"

The precautions taken to prevent foreign matter
getting into the paper consist firefly in keeping a 1

careful control of the cleanliness and general con- l

dition of all pulp used; this is usually done when dmfy '■* V

the pulp is first received at the mill and is tested
for moisture content. Secondly, coarse grids are

fitted at various points in the pipe lines, in boxes ® .

which may be isolated and cleaned out periodically ml

without interrupting production. The final point fk* “J-—the rotospray k» oean-

for holding back unwanted material is at the colour itoiiso has ahomogw-
s trainers through which the stock passes immedi- d® ®o* sbmeating the pawtcles
ately before flowing to the breast box. ^ TO?G 48,WOTOf “

Strainers and Slice .—The finally prepared stock,
regulated to a uniform consistency of 2| to 3 per cent, and containing dyes,
alum, and loading, is pumped to a head box, from which the required quantity
of stock flows through the stuff valve to be mixed at the mixing pump with the
back-water recovered from the wire pit It is important to have a
pressure of stock behind the stuff valve, as this is the valve that is

268

MODERN PAPER-MAKING

controlling the basis weight of the paper being made. The valve itself should
preferably be specially designed so that a large number of turns are required
to change the setting from the shut to the full-open position. This will give
greater delicacy of control, and therefore more accurate basis weight adjust¬
ment, than can be obtained from a valve that requires only a few turns to

[ Vickerys, Ltd., and Walmsleys (Bury), Ltd.

Fig. i 14-—Latest Type of High-Capacity Bird Screen for Newsprint Stock

ITk lower motor operates the shake motion and the upper motor drives the gearing which keeps the cylindrical

screen turning slowly round

produce a large change in the rate of flow. The diluted stock from the mixing:
pump passes direct to the strainers which, usually, are located behind the
breast box.

The strainers needed for news stock must, of course, be of large capacity.
The type used (see Fig. 49) is that known as the inward-flow strainer, because
the stock is pumped to an outer container and flows by gravity through the
slits of the screen to the centre. The screen itself is a large cylinder in which
thousands of slits, parallel with one another and in rows, are cut. The usual
width of slit for news is about 0.0025 inch. In operation the stock is helped.

NEWSPRINT

269

through these narrow slits by the jogging motion of the outer half-cylindrical
container, which is flexibly coupled to the main framework of the strainer by
rubber jointing each end. Material, such as coarse shives and slivers, which
is rejected by the screens, will accumulate in the outer jogging container. It
may be removed by bleeding continually a small quantity of stock from the
bottom of the container and passing it to an auxiliary flat screen, such as that

[Walmsleys (Bury), Ltd.

Fig. 115.—A Typical Strainer, Breast Box and Projection Slice Assembly for a Large

Newsprint Machine

On the left, the flexibly mounted container of one of the four inward-flow cylindrical screens can be seen

illustrated in Fig. 50, where accepted stock is returned to the wire pit, and
rejected material is sent to the main drain.

A large machine producing 150 tons of newsprint a day will require four
strainer units mounted parallel to each other and parallel to the direction of
the machine. The screened stock is discharged from the strainers into the
flow box which leads it over various baffles and weirs to the slice (see Fig. 115).
In the single case of the world’s largest paper machine, making 200 tons or
more of paper per 24 hours, there are six strainers all arranged at right angles
to the direction of flow, in two lines of three, on either side of a central collecting
trough.

The art in designing efficient flow (or breast) boxes consists firstly in aiming

2 7 o MODERN PAPER-MAKING

at keeping the stock as uniformly dispersed as possible; secondly, in preventing,
as far as possible, eddy or other local disturbances from arising, and lastly,
the stock must be projected on to the wire at a speed which gives the most
desirable sheet formation and sheet properties generally. The optimum speed
of projection is of course intimately bound up with the wire speed. Normally
it is found that the best practice is for the stock to be projected at a rate which
is 5 to io per cent slower than the speed of the wire. Flow boxes must, of

course, have no dead spots where slime and dirt can accumulate; a clean design,
in this respect, is consistent with the need for producing a uniform rate of
stock-flow to the slice.

The so-called projection slices (see Fig. 115) are used almost without exception
in high-speed news machines, although there are one or two other kinds of
slice working on different principles, and these may one day modify newsprint
slice technique. There is, for instance, the Millspaugh arrangement, in which
the stock contacts directly with a suction-operated forming cylinder. This
arrangement, incidentally, has the advantage of dispensing with the conventional
wire part of a paper machine. Another interesting development is the pressure
slice in use in one or two mills in the U.S.A. In this arrangement the wire
itself forms the base of a kind of swan-necked breast box. The stock impinges
on the wire and is to some extent forced down against it, giving an immediate
in i t ial mat of fibres on the wire. The quantity of stock available for build-

NEWSPRINT

271

ing up the remainder of the sheet thickness is governed by the height of the
projecting slice ‘lip’ above the wire. This slice is being found especially useful
for very free stock.

The Wire Part .—The wire part of a news machine is different from that
of slower-running machines in that there is usually no shake fitted, the section
is removable as a whole to facilitate wire changing, and it has fewer table, or
tube, rolls.

When the stock flows on to the machine wire, drainage of the water com¬
mences right away, but only a small proportion is removed by the effect of
gravity alone. Most of the water which is removed before the suction boxes

This machine has no slice, the 'wires are very short, and the duplex sheet is made by combining the under sides of the

two webs, thus giving finished paper having two top sides

are reached is withdrawn by the effect of the contact of the table rolls with the
underside of the wire, and by the suction produced as they revolve rapidly
round. This can be seen by observing what is happening under the wire,
and also to some extent the action is indicated by the appearance of the stock
on top of the wire.

The very large volume of water handled at the wet end of a news machine
makes it necessary for the table rolls to be rather large in diameter. On a
220-inch machine the diameter would be n or 12 inches, while on a 300-inch
machine the diameter is 15 inches. This large size is also needed to prevent
whip at the high speeds at which the table rolls rotate.

Some of the water drained from the stock tends to be flung back on the
underside of the wire by the centrifugal action of the rolls. This can spoil the
formation of the sheet, and in order to prevent the trouble the practice is very
often adopted of fitting baffles between the rolls, especially near the breast
roll. Alternatively it is helpful to space the rolls fairly far apart.

27 2

MODERN PAPER-MAKING

The wires used for making newsprint are almost invariably about 60 meshes
per inch in the cross direction and 40 in the machine direction, and the recently
developed long crimp or twill wires (see p. 166) are used very extensively
for news.

Drainage on the wire increases the consistency of stock from about 0.8 to
about 3 per cent, at which point the suction boxes or flat boxes, as they are
sometimes called, come into action, raising the consistency to around 16 per
cent. Finally the remaining water, which is capable of being removed while
the sheet is still in contact with the wire, is taken out by the couch where the
concentration is increased to about 20 per cent.

The finally diluted stock fed to the flow box of a newsprint machine is
very heterogeneous. The freeness will be about 50 c.c. Canadian standard,
and the china clay will account for about a quarter of the 0.8 per cent of total
solids, if an average ash content of about 8 per cent is desired in the sheet
being made. The quantity’ of very fine fibre and clay present in flow-box
stock is very much higher than it is in the thick stock delivered to the
mixing pump. This stock will have a Canadian freeness figure of about
125 c.c., and the total solids will have a china-clay content of about 10 per
cent.

The reason for the change in the composition and properties of the stock
when it gets to the flow box is that an amazingly large proportion of the stock
that flows on to the wire passes through the meshes by drainage and by the
action of the table rolls. Flow-box stock having a consistency of 0.8 per cent
will give rise to an average consistency in the wire pit of about 0.3 per cent.
This means that nearly 40 per cent goes through the wire. Most of this finp
short-fibred stock goes back again to the mixing pump to be delivered once
more to the flow box. It therefore does not represent lost material, but its
circulation back into the flow box is the reason why the stock issuing from the
slice is so very different in properties and composition from the thick stock
fed to the mixing pump.

The number of suction boxes fitted to the wire "will usually be about eight,
and the suction will be graded from about 5 inches of mercury to about 10
or 12 inches. The tops of the boxes must be fitted with some material that
will give rise to as little friction as possible between the rapidly travelling wore
and the suction boxes. Many different materials, including glass, granite and
synthetic resins, have been tried, but by far the most popular is still wood.
A hard wood, such as maple, arranged so that the grain is perpendicular to
the wire, gives very satisfactory results, both because it requires attention less
frequently than horizontal-grain suction boxes, and also because the load on
the couch motor is reduced to a minimu m (see also p. 183).

NEWSPRINT

273

A dandy roll is usually run, even on the fastest news machines in the country.
It closes the sheet and gives a more uniform look-through. Incidentally, a
dandy roll enables an identifying water-mark to be applied.

The couch on a modem news machine is essentially of the suction type
(see Fig. 69 and p. 192), otherwise economical speeds cannot be attained.
Occasionally a light rubber-covered top couch roll is used as well, but opinion
is divided as to whether this is really helpful. The vacuum at the couch is
usually about 17 inches of mercury.

The Press Part —During recent years quite a number of proposals have been
made with a view to improving the pressing of newsprint.

Some years ago it was quite common practice to have two plain presses
followed by a reversing third press, all with felts. Nowadays the first two
presses are almost invariably suction presses; the third press, in the development
of modem practice, was first deprived of its felt, then, by putting the brass
roll at the bottom and the granite roll on top, it became a straight-through
smoothing press. Finally, tests showed that it had very little, if any, effect at
all on the finish of the sheet, so that, in present-day installations, there is usually
no third press at all.

The bottom rolls of both first and second presses may be rubber-covered
or just plain brass. Rubber-covered rolls have the advantage that they widen
the contact at the nip, thus giving less drastic treatment to the paper. The
rubber covering is also kinder to the felts, which are prevented from directly
contacting the perforated brass roll. In some installations, notably on better-
class paper machines, running at slower speeds than news machines, important
increases in wet felt life have been obtained, but for newsprint made at high
speeds, rubber-covered press rolls are not invariably chosen, because improve¬
ment in felt life has not in all cases been established, and also because the extra
length of the drilled holes makes quite an appreciable difference to the capacity
of the vacuum pump required.

Two other important developments in pressing, to which reference
must be made, are the stacked press and the dual press. In the stacked
press three rolls are arranged vertically above one another. The two
bottom rolls are perforated suction rolls, each having a felt, and the top
roll is granite. The sheet is transferred from the bottom roll to the middle
roll by a suction box, and there is, in addition, a suction box at each of the
two nips for removing water. Pressure is applied in the conventional way by
lever systems.

In the dual press (see p. 196) there are again three rolls together, but in
this case they are horizontal. The solid roll is in the centre, and the two
perforated rolls are on each side. The dual press makes the arranging of the

274 MODERN PAPER-MAKING

felts and. the disposal of the water, thrown out centrifugally by the rolls, rather
more simple.

The stacked press and, more especially, the dual press are logical develop¬
ments of the press part, the most important advantage of which is the saving
in space. This is a specially helpful feature when old machines are to be
modernised (see Fig. 75), but it is doubtful whether a newly planned newsprint
machine would necessarily have a dual press installed in preference to two
separate suction presses.

Fig. 118.—Diagram of Millspaugh Automatic Couch which eliminates the Draw between the
Conventional Couch and First Press

Other developments at the wet end of news machines have been concerned
with handling the sheet in such a way that stretch is eliminated or greatly reduced
at the draws. The stacked press and the dual press are themselves examples
of this. The name of Millspaugh is especially connected with developments
along these lines, and among his many interesting designs there is the automatic
couch (Fig. 118), which picks the sheet off the wire by suction, thus eliminating
altogether the draw from the couch to the press rolls.

Some indication of the importance of eliminating draws in this way may be
obtained from the following figures, which have been carefully measured at
different points on a modem news machine fitted with a suction couch and two
separate suction presses:

NEWSPRINT

275

Speed

Increase

Stretch

Per Cent

Couch .

1045

—

First press.

II 08

6.0

Second press .

1120

1.1

First drying cylinder .

,. 1129

0.8

Sweat cylinder.

1130

0.1

Pope reel drum.

1130

0.0

Total wet end stretch.

—

8.0

Total dry end stretch.

—

0.1

Grand total for whole machine ..

—

8.1

The moisture removed by a modem press part is indicated by the following
average figures:

Moisture Content Vacuum Used
Per Cent Inches

Couch . 79 J 6

First press. 68 17

Second press . 66 22

Obviously it is important to remove as much moisture as possible by pressing,
in order to reduce the amount of drying required to a minimum.

The Dryer Part— The most difficult problem in the drying of newsprint is
ventilation. The greater the width of a machine die greater is the difficulty
of removing the moisture-laden air uniformly across the machine. It is the
general practice to fit hoods by means of which the damp air is collected and
discharged to atmosphere by a battery of usually six to eight fans situated above
the back of the machine. Coupled with this system, hot air is blown in through
trunking under the dryer section. The fundamental defect of methods of this
kind, however, is that air cannot pass direcdy upwards past the drying cylinders
because of the felts and the paper itself. Various methods have therefore been
tried to promote adequate circulation between the cylinders, and the Grewin
system is a typical example. In this system relatively small quantities of hot
air are blown into the dryer section alternately from the front and back of
the machine. The nozzles are placed as near to the paper as possible, so that
fresh dry air may be brought continuously into contact with it.

In spite, however, of all the attempts made to improve the uniformity of
drying, it is all too frequendy necessary to have to try to compensate for
uneven evaporation by loading the presses or crowning them specially to
give the lowest moisture content in that part of the sheet where the drying is
least efficient.

In tackling drying problems on news machines the fundamental fret must

27 6

MODERN PAPER-MAKING

[Air Control Installations , Ltd., Ruislip

Fig. 119*—View of a Neatly Designed Hood fitted over the Dryer Part of a Large

Newsprint Machine

LAYOUT OF NAPQUR ABSORPTION AND VENTILATION PLANT

[Air Control Installations , Ltd., Ruislip .

Fig. 120.—Diagram illustrating the Circulation and Removal of Air in the Dryer Part

of a News Machine

Note die arrangement by which air is admitted to die machine-house roof to prevent condensation

NEWSPKINT

277

be kept in mind that practically all the moisture has to be removed by using
air as a carrier. Water dissolves in air, and the higher the temperature of the
air, the greater the quantity of water it can earn' without becoming saturated.
This mechanism of drying is entirely different from drying by ebullition, and
it is doubtful whether any substantial proportion of the v r ater removed from
the sheet in a news machine is boiled off. Adequate supplies of hot air efficiently
circulated and removed after becoming saturated, or nearly saturated, are
therefore essential for satisfactory drying.

j j O

News machines built to run at the high speeds prevalent to-day are usually
equipped with about fifty, or in exceptional cases as many as sixty, 5-foot
dryers. It is generally considered that felt dryers are not an advantage, although
there is some difference of opinion on this matter. The last cylinder is usually
arranged as a sweat cylinder for damping the underside of the sheet. This is
especially important when making M.F. paper. Dry felts are used throughout
the dryer section, with the exception that on some machines it has been found
beneficial to omit the first bottom section felt, the idea being that free move¬
ment of air past the sheet, at this stage, is more important than pressing the
paper hard against the cylinders by means of a felt.

The difficulties of arranging for uniform ventilation, and therefore unif orm
drying, in conventional dryer parts, were overcome a few years ago by the
introduction of the Minton vacuum dryer. Although very few paper machines

MODERN PAPER-MAKING

278

have been fitted with this rather expensive system, the experiment was a very
courageous one, and recently it has been applied successfully for pulp drying.
In the Minton dryer all the cylinders are enclosed, so that they operate in a large
air-tight compartment where the pressure can be reduced to about 73 inches
of mercury. Working under these conditions, water can be boiled off, and
thus no air circulation is required. Drying is therefore quite uniform provided
the sheet is uniformly heated on the drying cylinders. Newsprint made on

[Edward Lloyd, Ltd., and Wabnsleys {Bury), Ltd.
Fig. 122.—View of the World’s Largest Paper Machine

machines fitted with Minton dryers is more bulky and absorbent than ordinary
newsprint, and it takes the ink very well.

Finishing .—Newsprint made in this country has achieved a very high
standard of quality, and one of the factors responsible for this is the super¬
calender. To obtain the best results from the super-calender the moisture
content has to be carefully controlled. Because of the difficulty, already re¬
ferred to, of drying paper really uniformly, it is necessary to over-dry slightly,
and then to damp the paper to the desired moisture content to give the best
results from the super-calender. It is difficult to give any very definite figures
for moisture content, but normally, after drying and before damping, there
should be about 6 to 8 per cent of moisture in the sheet, and the finished paper
should contain at least 8 per cent of moisture.

NEWSPRINT

279

The paper is damped on the machine just before reeling. A spray damper
is used to moisten the top of the sheet, and the automatic reel change-over
dr um provides a ready means of applying moisture to the underside, the method
being to spray the surface of the drum so that there is a film of water on it
ready to be transferred to the paper.

Newsprint super-calenders are remarkable chiefly for their gigantic size
coupled with the fact that the accuracy with which the rolls are ground is

Fig. 123.—Diagram illustrating an Arrangement for damping Newsprint prior to

Super-Calendering

In this arrangement, sprays of special design are used for both top and bottom damping

sufficient to enable a sheet some ^ inch thick to receive an amazingly uniform
finish (see Chapter XX).

Future Trends of Newsprint Manufacture—hi this very brief review of some of
the sali ent features of newsprint manufacture, some indication has already been
given of the lines along which developments are occurring.

Undoubtedly one of the main trends in technical advance will be towards
further increases in speed. The scientific staffs of some of the leading companies
are already actively studying the conditions and problems that will arise at
speeds of 2000 f.p.m.

Further efforts to cheapen the cost of production will be directed towards

280

MODERN PAPER-MAKING

decreasing, still more, the proportion of chemical pulp in the furnish. This
effect will be materially aided by further studies of groundwood production
with a view to producing qualities better suited to high-speed operation, and
at the same time giving paper of adequate strength and good printing qualities.
The processing of stock, in general, may in the future derive benefit from the

[Edward Lloyd , Ltdand IValmsleys (Bury), Ltd.
Fig. 124.—The World’s Largest Super-Calender

The approximate total weight is 250 tons; the bottom roll alone, which is 36 inches in diameter by 26 feet (face), weighs
44 tons. There are ten rolls in the stack, five of them being wool-paper ones. The marl mum specified speed is 2300
feet per minute

application of modem preparation plant, such, for example, as the Sutherland
refiner, which is very economical in power consumption.

Finally, although this chapter has been concerned primarily with the news¬
print industry in this country, some reference must be made to the recendy
announced commercial production of newsprint from Southern Pine. This
is a project that has long been under consideration, but difficulties due to the

NEWSPRINT

281

nature of the wood—particularly its high content of resins—have demanded
many years of painstaking investigation to make the project a commercial
possibility. The advantages of being able to use trees which grow to maturity
in a dozen years or so have been a very attractive goal in developing this under¬
taking, and the new factory now in operation near Lufkin, Texas, may well
be the forerunner of an important Southern newsprint industry.

CHAPTER XVH

HAND-MADE PAPER

The making of paper by hand is unique in this respect, that it is still carried
on in practically its primitive form, side by side with the most highly developed
paper-making bv machinery. When we look for the reason for this state of
things, we find it in the very high quality and excellence of hand-made paper
compared to machine-made for certain special papers, such as drawing and
filter-papers, bank notes, and superlative qualities of writing and account-book
papers, etc. This is shown by the many attempts made to give to machine-
made papers the qualities or appearance of hand-made by cheaper methods.

Hand-made paper is generally made from the best grades of linen and cotton
rags. Papers for very special purposes are made from new rags. The reason
for this is that the process is very costly, and it would be poor policy to put
low-grade stock through such a process.

The rags are treated in much the same way as for machine-made paper, but
as the quantities to be dealt with are very much less, they can be allowed more
careful sorting and more time for treatment than is the case where machines
have to be kept supplied.

These high grades of rags require very light treatment in boiling and
bleaching, and the resulting paper is, or should be, of very high quality and
purity.

The boiling is usually carried out in open pans without pressure, very little
lime or caustic soda being used, so that most of the original strength of the
fibres is retained.

After boiling, the rags are picked over again to remove any contraries’
such as black threads, buttons, etc., which may have become exposed during
the process.

The rags are broken in, in breakers fitted with drum washers to carry off
the dirty water, dean water being run in all the time until the water leaving
the breaker is as clean as that entering it. The colour of the stuff is then im¬
proved by adding a little bleach, which is afterwards carefully washed out,
until a starch iodide test shows no trace of chlorine in the stuff.

When we come to the beating, which is done in small hollanders with very
light rolls, we find that longer and freer stuff, and also more highly fibrillated
or wet stock, can be more successfully dealt with by hand than on the ordinary

282

HAND-MADE PAPER

283

Fourdrinier machine. For instance, for filter-paper, stuff that is so long, raw
and fiee that it is impossible to get it through most strainers or to put it together
on the machine wire can he made into a compact sheet by hand. And very
highly fibrillated stock for strong ledgers, etc., can be made to heavier sub¬
stances on the hand mould than could be run satisfactorily over the usual wet
end of a Fourdrinier machine.

On leaving the beater the stuff passes to a stuff chest, whence it passes along
sand traps over magnetic separators to remove metal and through strainers
into the vat. As the quantity required by one vat is small, the straining of the
stock is not forced, as it too often is for a machine, and this is a great advantage
in producing clean paper. Being generaEy well fibrillated, the stuff is warm
on leaving the beater, and it is warmed for ease and speed in making, and to
save the vatman from having to slow down so as to handle cold stuff. It is
also kept stirred while in the vat by an agitator or ‘hog’.

Moulds for Hand-Made Paper .—The foundation of a mould for making
hand-made paper is a framework of hardwood into which are set at convenient
distances a number of thin transverse wooden bars, which are perforated with
small sewing holes.

Used in conjunction with this frame is what is termed the deckle, which
closely resembles a picture frame, and when placed in position on the mould
provides the necessary edge to keep the pulp from running off the mould back
into the vat. It also determines the exact size of the sheet of paper.

The surface of the mould (called ‘the sheet’) is provided with either a laid
wire sheet or a woven wire cloth, the laid being the older form of covering.
In either case it is sewn down to the framework, the sewing wire passing through
the perforations in the bars.

The laid sheet is so called because its component wires are actually laid in
position by hand as the cloth is formed, being held together by chain or twist
wires, and the construction of this type of mould differs but slightly from the
earliest types. At the present time most of these coverings are laid mechani¬
cally, with the result that the mould has a much more even surface, but there are
still a good many moulds made with hand-laid ‘sheets’.

In its earliest form a paper mould was probably formed by blitting or
■weaving vegetable fibres or split cane together to form a sheet, and then stretch¬
ing this sheet over a mould in such a way as would provide an adequate surface
for the pulp to be lifted from the vat and drained.

The introduction of drawn wire largely benefited the construction of paper
moulds, both in the case of laid sheets, and later in the introduction of the
woven type of sheet or cover.

It may be mentioned that the earlier types of moulds have the laid sheets

MODERN PAPER-MAKING

284

placed directly on to the bars, the position of the chain lines being directly
over the wooden bars, and this causes the slight shading appearance in the
paper around these parts.

With the mechanically-made ‘sheet’ it has become customary to introduce
a laid under ‘sheet’ which, by giving a slight clearance between the top sheet
and the mould, allows for a better waterway, gives a more evenly water-marked
surface to the paper, and does away with the shaded appearance mentioned
above.

Letters or devices are sewn on the surface of the wires or wire cloth. Some

[J. Barcham Green and Son and the *Daily Mirror* Newspapers

Fig. 125.—Hand-Made Paper-Making

The vatman making a sheet of paper on the mould. The sheet is actually formed, and the ‘deckle’

is about to be removed

moulds have patterns or figures embossed on the wove wire cloth both up and
down, so as to form thick or thin places in the sheet, and many beautiful designs
are produced in this way.

The paper-maker who handles the mould and makes the waterleaf sheet is
called the vatman (Fig. 125). With the deckle in position he dips the mould
into the stuff in the vat, and, lifting it up, he gives it the peculiar shake and
movement which closes up the sheet and gives it the desired character; he
sometimes causes a little wave to run over the mould, so getting rid of the
surplus pulp, and leaving the fibres evenly felted behind it. He tips some of
the water off the top and then places the mould on the bridge beside him, within
reach of the coucher, at the same time removing the deckle.

HAND-MADE PAPER

285

The coucher tilts it into a sloping position to allow more of the surplus
water to run through the sheet and off the under side of the wire cloth, and then
presses it face downwards on to a felt. Skilfully lifting the mould from one
edge first, he leaves the wet sheet on the felt, and places another felt on top of

[J. Barcham Green and Son
Fig. 126.—Hand-Made Paper-Making

Vat’s crew at work on a two-sheet mould. The sheet is already formed and mould is ready for deckle to be removed,
the upper end boy assisting, and in the foreground the layer picking up the felt with his right hand and the sheet
with his left.

it. Another sheet is laid on the pile, and so on until a ‘post’ of alternate sheets
and felts is built up.

This post is subjected to heavy pressure in a press, to squeeze out as
much water as possible. The sheets are then stripped off the felts by a

286 MODERN PAPER-MAKING

‘layer’ and piled into packs’, which are taken and pressed again for some
hours. These packs are then separated sheet by sheet carefully, and then they
are pressed again for twelve hours, when they are again parted, pressed again,
and then hung up in a loft to be air-dried. In summer the natural air is enough,
but in winter steam-pipes are used. When sufficiently dry the paper is stacked
up in piles to mature and flatten out. This maturing process may take weeks
or months. The waterleaf is now ready to be sized with gelatine.

The sizing is carried out in a sizing machine, which consists of a tub through
which two endless felts travel slowly, with the sheets of waterleaf between
them. After the sheets have been well soaked they are carried between squeez¬
ing rolls to force the size into the sheets and also to remove excess size from
the surface of the sheets; this prevents subsequent discoloration by reason of
patches of size lying on the surface.

After sizing, the sheets are stacked up in piles and covered with hot felt
and allowed to stand for about twenty-four hours. This gives the size a chance
to permeate the sheet thoroughly and the heat prevents the sheets sticking
together. After this the sheets are parted by girls, so that warm air can get
at them and dry off the surplus moisture.

The paper is afterwards allowed to stand in piles for a day and then again
carefully parted sheet by sheet, care being taken not to strain the sheets unduly
if they should be stuck together, otherwise they will be cockled and will never
lie flat.

The sheets are again allowed to stand for a few hours, and are then
taken to the drying lofts. These lofts are heated and care has to be taken to
prevent cold air or draughts getting in, or the paper will be spoilt. Different
temperatures are used for drying different qualities of paper. The paper may
be dried flat on hessian screens, or hung over cow-hair ropes. Most papers
are sized a second time after drying. The stronger the paper and the more
fibrillated the stock, the more difficult it is to get the paper to take the size,
owing to the absence of air spaces. After drying in the loft the paper is stacked
in heaps to mature, and is then sorted over for defective sheets before being
plate-glazed. It is then sorted over finally by experienced sorters, who separate
it into good, retree and broken.

The most important features of hand-made paper are its great strength and
its tendency to expand and contract equally in both directions after damping
and redrying.

The shake given by the vatman is in two directions, so that there is very
little difference in the tensile strength in the length and breadth of the sheet.
Machine-made paper shows a decided difference in strength and expansion in
the machine and cross directions.

HAND-MADE PAPER 287

The couching pressure is applied to hand-made paper slowly and directly
at right angles, instead of the sudden rolling up of the machine couch rolls.

The expansion and contraction of hand-made paper, being much more
even, are of great advantage for some special papers, such as bank notes and
other papers which have intricate designs printed on them, and which must
register correctly.

Water marking can be made very clear and distinct, and some very beautiful
and elaborate designs are produced. While the dandy roll can only make an
impression on the already formed sheet on the machine, the water mark on a
hand-made sheet is moulded into the fabric. No loadings or resin size are
used because, the paper being loft-dried, there would not be sufficient heat to
fuse the resin in the sheet. Hairs from the felts were often left on the surface
of hand-made sheets, causing annoyance when a pen was used. This trouble
has, however, been eliminated recently to a great extent.

The substances of sheets are sometimes very irregular before the sorting,
but they are on the whole astonishingly good, when the conditions of working
are taken into account. The percentage of broken is naturally higher than that
of machine-made paper.

Hand-made papers are mostly sent out in rough or low finishes, especially
for drawing and painting, but those for writing are usually plate-glazed. Owing
to the deep impression of the felt and the absence of the smoothing process
between press rolls, it is difficult to obtain a close finish.

A steel pen-nib will generally be found more satisfactory than a fountain pen
for writing on hand-made paper, the surface of which usually has a ‘greasy’
nature, because stationers think a rough paper looks better, and insist on the
maker supplying this, when a higher glaze would make it write perfecdy well,
and it .really looks just as good.

It is scarcely necessary to add that the vatman and coucher must be skilled
and steady workmen, the vatman in particular, for he has to make sheet
after sheet without deviating from the correct substance or altering his
shake.

It is also quite a common occurrence for a vatman, owing to nervous strain,
to lose control of the muscles of his arms, and, as it is called, ‘lose his shake’,
sometimes only temporarily, usually permanently.

The vatman can only do his work properly if he is in good health and
‘free from care’. The least mental strain or worry shows itself at once in
the resulting paper, so that the substance, appearance and character of the
paper are altered or irregular. Quite frequently, when beginning to make a
certain paper after having just finished making a different size or substance, it
will take some time before the vatman setdes down and gets the paper right.

288

MODERN PAPER-MAKING

and he usually knows himself that it is wrong, and marks it with tabs so that
it can be set aside for repulping or special sorting when finished.

The finished paper is finally sorted by layers’, who are women of great
experience. These layers throw out defective sheets, which are in their turn
sorted again by ‘second layers’ into retree and broken, so that finally three
grades are left—namely, good or perfect, retree and broken. These grades are
all fit for sale, but the retree and broken are sold at a lower price, in the same way
as machine-made papers. The reams are made up in various ways—viz.:

1. Mill reams, containing 472 sheets (432 good, with 20 broken sheets

on top and the same number of broken sheets at the bottom of the
ream); this method is now given up by most mills.

2. Insides, 480 sheets, all ‘good’.

3. For export, 500 sheets, all ‘good’.

4. Retree insides.

5. Retree mill reams.

6 . Broken.

It is often said that hand-made papers are expensive. This idea is quite
erroneous when the superlative excellence, strength and durability of the finished
sheet are taken into account. Hand-made papers are actually cheaper than
machine-made papers in comparison, when the conditions of manufacture are
considered.

For instance, a mill with five vats, making about 3 tons of paper per week,
requires 125 employees for the various processes, and bums 25 tons of coal,
60 per cent of which is for drying, some power being obtained from the river.
It takes from two to three months for a sheet of paper to find its way through the
mill, and the various processes entail about one hundred separate handlings.

There are a good many purposes for which hand-made papers are essential,
and for some of these they are actually a good deal cheaper in die long run than
are machine-made papers.

Drawings .—The fine texture and ‘tooth’ characteristic of hand-made papers
render them essential for the beautiful work of the real artist.

Etchings .—For printing wet or dry, the etcher wants a paper which will
withstand the pressure and yet be sympathetic to the plate, combined with a
lasting quality and purity that are not to be found in machine-made papers.

Money paper and all documents which get a lot of handling have to be printed
on the very best paper obtainable, and the slight extra cost of hand-made makes
the paper much cheaper in the long run. Very intricate lettering and devices
can be put into these papers, and die English hand-made mills make money
paper for banks and Governments all over the world.

HAND-MADE PAPER

289

Mounts and Covers.— Half the battle, when one wants to display a good
picture, is to have a suitable background, and there is nothing to equal a good
hand-made mount, which can be obtained in white and almost any shade of
colour, even to black.

Vellum Papers— The amazingly strong imitation parchment papers made
by hand are equal to and in some ways superior to real parchment. They are
practically indestructible, and they are not so easily affected by heat, mildew,
or insects as are skin parchments.

Filter-papers for the most delicate chemical analysis are almost invariably
made by hand, and they are the most reliable, the amount of ash in some of
the chemically treated ‘ashless’ papers being practically nil.

Notepapers and Envelopes.—There is something distinguished-looking and
‘good’ about hand-made notepaper which cannot be imitated by any of the
machine-made varieties. A box of good hand-made paper is actually much
cheaper than many of the gaudy cabinets and compendiums of inferior engine¬
sized notepapers which are to be seen in all stationers’ shops, and which seem
to have a ready sale.

Ledger Papers.— For ledgers and account books, which have to be durable
and stand a lot of hard usage and fingering, there is nothing to equal the blue-
laid English hand-made papers.

Printing Papers.— For costly editions of valuable books, and for editions de
luxe, hand-made printings are still in good demand, and they give an added
charm to the volume when combined with good and tasteful printing.

A hand-made paper-maker is a craftsman who has served at least seven
years of apprenticeship before he gets his ‘Card of Freedom’, and until he
obtains this card, which may only be awarded him by the Society, he is not
allowed to be employed in the making of hand-made paper. The result is
that after many years of tuition there exists a body of workmen called ‘The
Original Society’, who are highly trained and who enjoy a freedom not possessed
by any other organization of workmen.

It is interesting in this connection to note that membership of the Society
can be traced from generation to generation, son following father in unbroken
succession, and several of the fifth generation are employed in the hand-made
mills to-day. The same holds good of the employers also.

[We are indebted for much of the above information, and also for the blocks
of the illustrations, to Messrs. J. Barcham Green, hand-made paper-makers,
Hayle Mill, Maidstone.]

CHAPTER XVIII

GELATINE-SIZING-HAND-SIZING-TUB-SIZING-AIR-DRYING

The best writing and typewriting papers, whether machine-made or hand¬
made, are always ‘sized’, or coated and impregnated with a solution of gelatine,
in order that their surface may be more even and more resistant to ink.

Papers sized with a gelatine emulsion are freer from fluff and ‘hairs’ on
the surface, as these are all glued down among the other fibres and do not
become attached to the pen-nib. This glueing down does not, however,
take place with the coucher hairs from the felts, as these are wool and not
cellulose.

In the case of a gelatine-sized paper, the ink lies in the thin film of gelatine
and dries there, so that it may, if necessary, be erased and other letters or figures
substituted.

Papers are sometimes required to ‘stand ink after erasure’, which means
that they must be hard ‘engine-sized’ before they are tub-sized. In this
case, when the paper has been hard-sized in the beater, less gelatine is taken up
in the same time, as it does not penetrate the sheet to such an extent, but lies
on the surface. The writing is easily erased, the gelatine being removed with
it, and more writing may be filled in without the ink ‘running’ to any great
extent.

Gelatine-sized papers are much more durable, as the fibres are protected
by the thin film from the oxidising agents of the atmosphere. They are also
rendered more tough and will stand folding and rough handling. The gelatine
also imparts other distinctive qualities to papers, such as ‘snappiness’, handle,
feel and look-through.

Hand-Sizing .—All hand-made and, in some cases, machine-made papers
are sized in sheets, and the method is called hand-sizing, as it was originally
carried out by dipping sheets of waterleaf into a tub of gelatine.

The sizing is now done by placing the sheets between two endless travelling
felts, which run through a bath of warm gelatine size. The sheets are carried
into the size and thoroughly soaked in it, the felts, which are very thin, hav ing
holes punched in them to allow the free passage of the gelatine. The excess
size is squeezed off by means of a pair of press rolls, through which the felts
carry the sheets; the latter are then'taken off and stacked ready to he taken to
the drying loft, where they are dried by air at various temperatures. The

290

GELATINE SIZE

291

sheets may be hung by clips or laid on hessian, in which case they will be dried
flat, or they may be hung over cow-hair ropes and dried with a ‘back’ or ridge
down the centre, caused by the rope; such papers are called ‘backed’ and the
ridge has to be cut out by means of a guillotine, the ‘deckle edge’ thus being
absent on one side of each half of the original sheet.

Tub-Sizing.—la the ‘tub-sizing’ of machine-made papers in a continuous
web the paper is run off a reel, or straight from the drying cylinders, through
a tub of gelatine size and again reeled up to ‘soak’, or run straight over an
air-dryer, which will be explained in detail in a subsequent paragraph.

Preparation of Gelatine Size .—Most mills do not now prepare their own
size, but find it more economical and clean to buy the particular grade of gelatine
which is best suited to their need, ready prepared in sheet form.

This method does away with the necessity" of buying skins and wet pieces
from tanyards, boiling them down and running off several ‘draws’ to make
the sizing solution.

For those who wish to make their own size the following details may be
of interest:

The wet hide pieces are soaked in cold water and washed in revolving
drums to free them from the lime which has been used to preserve them.

The size is extracted from the skins by boiling them in copper-lined, jacketed
heaters, into the bottom of which is fitted a wooden frame covered with openly
woven cloth. The solution of size passes through this sieve and the slime and
other objectionable matter are kept back.

The heat is brought up to about 170° F. and the charge stands for about
16 hours before being drawn off. The heat must be put on again before drawing
off, in order that the first draw may run off easily to the store tanks.

The first ‘draw’ contains the strongest jelly, but one or two more ‘draws’
are made in order to extract the whole of the gelatine. The second heating,
with a fresh supply of water, is conducted at a temperature of about 190° F.,
and is allowed to stand as in the first treatment.

A third and fourth infusion may be made, the third being heated up to
about 200° F. and the fourth boiled for an hour or two.

The amount of water added to the heaters for each treatment must be
regulated according to the strength of the size required, and will, of course,
depend upon the quality of the skins. The size should be strained through
flannel cloth over a wire sieve.

The strength of the size for the store tank is regulated according to require¬
ments by mixing together various amounts of the different infusions, such
as the first and fourth, second and third, or any other which may be found
suitable.

292

MODERN PAPER-MAKING

For the reason that size of different strengths may be easily obtained in this
way, some mills still continue to make their own. By using a bath of size
made entirely or almost entirely from the first draw, a very hard-sized paper is
obtained, and one the strength of which is very greatly increased; for other
papers, weaker solutions will suffice.

A small percentage of white soap is added to the size and thoroughly mixed
up before adding the alum; about i\ per cent is the usual amount. If the soap
is not put in before the alum the size will curdle. The soap must be pure tallow
curd, and may be bought, specially made, under the name of ‘paper-makers’
soap’. The soap helps to give a high finish to the paper, and it also prevents
the formation of glistening alum specks on the surface of the paper.

Alum is added in the proportion of about 14 or 16 lb. to 112 lb. of gelatine,
reckoned on the dry weight. The function of the alum is threefold: it serves
to stabilise the consistency of the sizing solution at various strengths and tem¬
peratures, and also acts as a preservative by arresting the formation and growth
of destructive bacteria, which quickly destroy the gelatine and cause it to
putrefy; the third function of the alum is to render the gelatine resistant to ink
penetration.

The effect of the alum on gelatine solution is very curious. If it is slowly
added, it causes the gelatine to thicken until it becomes almost solid; when,
however, more alum is added, the gelatine becomes fluid again, and it is in this
condition that it is used in the size-bath. About 12 or 14 per cent of alum
will be required to produce this solution. The normal way of testing the
density of the solution in the mill is by means of a special hydrometer which
has two scales of figures.

For a good quality paper in substance about 16^x21, 21 lb., 480’s, the
temperature of the bath should be no 0 F., and the density 7, as shown on
the hydrometer. This figure is arrived at by allowing for the temperature on
the scale.

Only the best sulphate of alumina must be used, and it must contain no
iron or free acid.

Excellent gelatine may now be obtained in the form of small sheets ready
for dissolving, and this saves the paper-maker the lengthy and rather unpleasant
business of preparing the size from skins.

These skin and bone glues are made in a wide variety of qualities and colour,
from dark brown to almost colourless (bleached). In order to find a grade
suitable for tub-sizing, various samples may be tested. The qualities most
desired are penetration at high temperatures and good stiff gelatinisation at
ordinary atmospheric temperatures.

This simply means that the solution should penetrate the surface of the

GELATINE SIZE

293

paper while it is passing through the tub, and then dry hard on the dryer after¬
wards, giving the maximum resistance to ink and moisture and the maximum
increase in strength and bursting strain. When testing gelatines, the colour
of the solution must be taken into account, because the use of dark-coloured
solutions will bring down the colour of the paper to an appreciable extent.

A rough way of testing samples against each other is to weigh out pieces
according to their price; soak in water for 24 hours, remove them and wipe
off surplus moisture, and then dissolve in equal quantities of water in a water-
bath. When all the jelly has dissolved, remove the dish from the water-bath
and allow to stand until cold. The stifFest jelly will be the most economical,
and, if its colour is satisfactory, will be the best for tub-sizing.

The stock solution of size is made in the following way: The sheets are
placed in a tank, covered with cold water and allowed to stand for 24 hours.
By this time they will have swollen to several times their original thickness,
but they will not have dissolved. The water may be drained off and hot water
added, or the temperature of the water in the tank may be raised to about
150° F. The jelly will dissolve, and soap may be added in the proportion of
about 2 or 3 per cent on the dry weight of gelatine. When the soap has dissolved,
12 to 14 per cent of alum is added, and the size is now ready to be run to the
store tanks. Here it is tested for strength, and if too.strong it is diluted with
hot water to the required strength. It is now ready for use.

The tub-sizing machine consists of a trough, either of wood, lined with lead
or copper, or of cast iron with a copper lining. No iron- or steel-work must
come in contact with the gelatine solution.

The trough is heated by a copper steam coil or may have a double bottom
with hot water circulating across the under side, in order that the temperature
of the size may be kept constant. The best method is undoubtedly that in
which hot water circulates through the bottom of the entire mb, as in this
way the whole of the solution is kept at a uniform temperature. The tem¬
perature of the size is indicated by a thermometer kept permanently in the mb.
A thermostatic controller will give perfect results.

Various methods are used for leading the web of paper through the mb,
and all paper-makers seem to have their own ideas about it. The main principles
to be borne in mind, however, are that the paper should be soaked for a period
sufficient to allow it to expand to the utmost, otherwise trouble will be experi¬
enced with ribbing or piping of the paper as it is wound up wet after leaving
the mb. This ribbing is caused by the paper still taking in size and expanding
while being tightly wound, and as it cannot expand easily outwards, it expands
upwards and takes on a shape resembling that of corrugated iron.

A suitable arrangement of squeezing rolls must be fixed at the end of the
u

294

MODERN PAPER-MAKING

tub in order that the excess size may be removed from the surface of the paper
before it passes to the air-dryer, or is wound up.

A satisfactory arrangement of tub-sizing plant is illustrated in Fig. 129, and
a much more elaborate tub, with a steam jacket and other improvements, is
shown in Fig. 127.

The paper is led, either direct from the steam-drying cylinders of the machine
or from a reel, over a dancing roll and round a large wooden roll fixed in the
front of the tub. This roll is half submerged in the size, and the web of paper
passes under it and along the bottom of the tub to another large wooden roll,
also half submerged in the size. The web is led round this roll, and out of
the size, over a guide roll, and into the nip of the squeezing rolls.

The squeezing rolls are important, and various combinations are in use.
They may be either brass on brass, rubber and brass, or granite and rubber, the
latter making an excellent combination. These rolls, no matter of what they
are made, must always be kept in good condition, free from ridges and blemishes
of any kind, and they must fit evenly the whole way across, otherwise damp
patches will occur in the paper, and these will show in the finished sheet. Rubber
rolls must be most carefully handled, as they are easily scratched and damaged,
and the least mark in the roll will leave a corresponding mark on the paper,
which may be visible only in certain lights.

The rolls must always be kept clean, and the top roll should be provided
with a doctor and spray of water in order to wash off any froth or scum.

The top roll should be fitted with levers and weights, so that the pressure
may be regulated.

Mention has already been made of the thermometer which is fitted in the
tub; this should be in such a position that it may be easily seen all the time,
as endless trouble may be caused by the temperature falling below its proper
height.

During the working of the tub a great deal of froth is formed by the agita¬
tion of the size; this must be removed regularly in order to prevent it becoming
hard and getting on to the web, and being pressed in by the squeezing rolls,
thus causing hard size lumps or spots in the finished paper.

The level of the size in the tub should always be carefully regulated, as
trouble is often caused by the level being allowed to get too low, and the scum
which floats on top settling on the web, causing .blemishes in the finished
sheet.

The best sizing results are obtained when the paper enters the tub in air-dry
condition and absolutely flat and free from cockles, creases and wrinkles of all
kinds. It will be found advantageous to pass the paper over a scraper before
it goes into the tub, in order to remove loose particles of rubber, which often

TUB-SIZING

295

adhere to the surface and stand out prominendy after passing over the drying

cylinders. . .

Op ini ons differ as to whether the paper should be reeled up after sizing and

allowed to stand and soak for a time before being dried. It is the practice in
some mills to have several reels lying sized for some hours before drying, while
others allow the reel to soak while the previous one is being dried; others,
again, run the paper straight from the tub over the dryer.

& So far as the efficiency of the sizing is concerned, there seems to be little to

[Messrs, Masson, Scott and Co., Ud.
Fig. 127.—Tub-Sizing Vat and Squeeze Roils

choose between the various methods, and our experience leads us to the con¬
clusion that the latter method—namely, ru nn ing the paper straight through the
tub and over the dryer—is the most economical and convenient, although it
means that the sizing and drying must always be done at the same speed.

Nevertheless, by this method we have sized papers in the same tub vary¬
ing in substance from Large Post 7 lb. to Large Post 35 lb., with excellent
results.

The second method seems a waste of time, as that part of the paper which
has just left the tub is the first to pass over the dryer, and consequently one end
of the paper will have been soaked for an hour or more while the other will
be fresh from the tub.

MODERN PAPER-MAKING

296

The prolonged soaking of coloured papers is not advisable, as the colours
are liable to fade.

Another drawback with reels which are allowed to stand and soak is the
fact that the deckle edges often stick together and cause tears at the edges of
the paper when being unwound at the dryer. To prevent this, the sides of the
reel must be washed with hot water, or a jet of steam should blow gently against
them during the unwinding.

The only point in favour of sizing and drying in two separate operations is
that the speed in the ‘straight-through’ method cannot be varied to suit varying
conditions of the atmosphere, and the slower the drying has to be done the
longer the soaking of the paper in the tub.

When the two operations are separate, the dryer can be slowed or quickened
at will, as the dryness of the paper demands, without interfering with the sizing.

Tub-Sizing with Fec/dose.—Feculose is sometimes used for tub-sizing writing
papers, either in combination with resin or with gelatine size. Provided that
the paper has not to be free from starch, excellent results may be obtained so
far as hardness and resistance to ink are concerned, if resin is also used, and
feculose is usually cheaper than the better grades of gelatine.

The method of preparing the solution is as follows:

200 lb. of feculose are stirred up with 90 gallons of water, warm but not
above 160° F., and heated with steam injection until the temperature reaches
205° F. Allow to stand \ hour to ensure thorough cooking, then add 800 lb.
(80 gallons) of cold water.

10 lb. of resin size are placed in a tub and 8 gallons of water added, then
heated to dissolve the resin size with the addition of £ lb. of soda ash (the resin
size is used just as it is delivered); then add 2 pailfuls of feculose solution.

10 lb. of alum are dissolved in 8 gallons of water with steam injection and
2 pailfuls of feculose solution are added.

The made-up resin size should now be added to the feculose solution through
a sieve and mixed well with a wooden paddle; next add the alum solution
and stir.

The feculose solution is now ready and should be about 5 0 to 6° Be. (8° to
9° Tw.) } but can be diluted to any desired strength.

By following this method the colloidal condition of the resin is obtained,
and therefore its maximum efficiency assured.

If the paper has been well sized in the beater, the resin and alum can be cut
out, but it is advisable to add i to 1 per cent of formalin calculated on dry
feculose to ensure the keeping qualities of the feculose solution. Where alum
is used the formalin is not required, as the alum prevents fermentation. For¬
malin does not thicken feculose as it does glue.

AIR-DRYING

297

With pure rag paper, where the resin does not exceed i per cent, the quan¬
tity of resin added to the feculose solution should be doubled.

The sizing may be carried out in the ordinary size-tub of a tub-sizing machine
and the paper then dried by hot air. As an alternative, however, a bath of
feculose of about 10 per cent strength may be placed after the presses, and
immediately before the steam-drying cylinders of the machine. In order
to give full ink resistance, resin size is added to the feculose in the bath and
precipitated in the usual way by alum. The heat of the drying cylinders does
not affect the feculose size adversely, as is the case with gelatine.

Paper sized in this way should not be called ‘tub-sized’, as this term has
long been applied to high-grade papers sized with gelatine, and it is likely to
be misleading.

[Messrs. Masson , Scott and Co. .

Fig. 128.—Section of Tub-Sizing and Air-Drying Machine, showing Hot-Air Blower on Top Section

The dried web is brought back to the bottom floor to be calendered

Air-Drying .—To carry out this operation the paper is led over a series of
sparred drums about 3 feet in diameter by means of cotton tapes. The drums
are composed of iron ends and spindle and have wooden spars. Some of them
are also fitted with metal fans revolving in the opposite direction, in order
to agitate the air and keep it in motion, and these fans also assist in keeping
the paper flat and preventing it from running into creases. They are generally
arranged in tiers.

Attempts have been made to dry a tub-sized paper in an enclosed dryer
where hot air can be circulated, and thus dry the paper quickly and in a much
smaller space than is required with the ordinary sparred drums in a heated
room. So far as we are aware, however, up to the present this method has
not been found very successful.

A typical air-dryer is illustrated in section in Fig. 128. If the paper has to

MODERN PAPER-MAKING

298

be dried at a high speed a very large number of drums is required, as many
as 120 or even 140 being used on some machines.

The arrangement for supplying hot air consists of a series of steam-pipes
running along the floor under the dryer, and the heat of the room, is regulated
by a valve worked in conjunction with a steam pressure gauge and a thermo¬
meter, or by a thermostat.

Some of the latest dryers also have a hot-air blower arranged to supply extra
warm air to the upper tiers of the dryer, as it was found that by the time the air
had risen from the first and second tiers it was so charged with moisture as to
be unable to remove the final traces from the third tier.

There are several different forms of procedure adopted by various mills.
In some cases the dryer is situated at the end of the machine immediately
following the size-tub, so that the paper may be run straight from the drying
cylinders, through the size-tub and on to the dryer, in a continuous web. This
is the cheapest and best method, from the point of view of labour saving and
the reduction of broke. Obviously if the whole operation of making, sizing
and drying is carried out in one room, not more than five men and boys will
be required, and when the machine has to stop to wash up or change, all five
men will be available to assist at the wet end in cleaning sand traps, strainers,
washing felts, etc., and so the length of time taken for this very necessary work
can be reduced to about one-half of that which would be taken by a machine-
man and one assistant, were the machine separate from the dryer.

Another advantage of this method is that a sized and finished sample of the
paper can be got in the shortest possible time for the purpose of comparing it
with the sample to be matched. The sizing always affects the colour of the
paper in some degree, and if a waterleaf sheet only is available for comparison
with a finished sheet, allowance will have to be made for the colour ‘going
back’ a little after sizing.

Among the disadvantages which might be claimed against this method
may be mentioned the fact that sizing and drying have to be done at the same
speed at which the paper is being made, but we know of two very satisfactory
machines on which this method is used, and the speed of the machine has
never been affected by sizing or drying troubles.

Of course, a sufficiently large tub and a long or hot enough dryer must be
provided to size and dry the paper at the maximum speed of the machine.

A slight variation of this method is to have the machine, size-tub and dryer
arranged to follow straight through, but to reel the paper after sizing and then
pass it over the dryer.

It is, however, difficult to see what advantage there can be in this, except
that the size gets a little time to soak in, for the last part of the reel to be sized

AIR-DRYING

299

is the first part to be dried, and supposing that the dryer is run one reel behind
the machine, some of the paper will be dried almost immediately, while some
of it will have been soaking for an hour or more. Surely this must result in
unequal sizing, if it is claimed that better s izin g is obtained by allowing the
paper to soak in the size.

We are of the opinion that in actual practice the difference is negligible
between sizing results from soaking and drying straight away. In some mills
the making, sizing and drying are carried out in three separate operations, the
sizer and dryer being right away from the machine.

This method means that the paper has to be wound up three times and

Fig. 129.—Tub-Sizing and Air-Drying Plant, showing Tub and Squeeze Rolls, also Sparred Drums

of Dryer

unwound twice, and at each of these operations some paper is spoilt. It also
means more labour, as it is impossible to shut down a sizer or dryer to send
men to help wash up the machine, etc.

The only advantage which can be claimed for this method is that the speed
of each machine can be adjusted to the exact requirements of the paper, and if
trouble is being experienced at the size-tub, the machine need not be stopped.
The same applies to the dryer.

Another arrangement is to reel the paper at the end of the making machine
and then to size and dry it in one operation. This method is the best and
usually the most convenient, if it is impossible to arrange all three operations
simultaneously. The output of the machine cannot be affected in any way, and

300

MODERN PAPER-MAKING

it will usually be found possible to make up any lost reels when the machine
is shut for changing, etc.

The web of sized paper is led over the sparred dryers by means of tapes until
it reaches the calenders and is started on the reel. The tapes may then be run
off the paper to the side of the drums, in order to avoid marking the paper
and causing cockling.

It is, however, sometimes necessary to keep at least two tapes on the paper,
one above and one below, to keep the web tight and prevent it running off to
the side of the drums. It will be an advantage if the spars of the first twelve
drums are covered with strips of zinc or copper, as a certain amount of size is
always deposited on the spars of the first few drums, and must be scraped off
periodically. It is not easy to scrape wooden spars without damaging them,
but zinc- or copper-covered spars are easily cleaned with a cloth and hot
water.

Trouble is sometimes experienced from paper cockling or creasing at the
dryer, owing to the fact that it has not completely expanded in taking up size
in the tub. The root cause of this trouble is that the paper is not long enough
in the tub, but it can be got over by allowing the web to pass along a travelling
felt between the tub and the dryer, in order that it may have sufficient time to
expand fully before it is tightened up on the drums of the dryer.

An old wet felt can be utilised for this, and will last a long time, but it must
be washed at least once a week.

In the drying of thin banks cockling and creasing can sometimes be traced
to the fan speed, and this should be capable of easy adjustment. The speed of
the fans is often excessive. If the air is kept in constant agitation and prevented
from lying stagnant inside the drums, nothing more is required.

The temperature of the drying room is important, and should be kept at
about 85° F. and as dry as possible. Drying is much easier in the summer than
in winter, and on a dry day than on a wet and foggy one, unless, of course,
specially heated and dried air only is allowed to enter the room, and adequate
fans are provided for the complete removal of all air after it has become charged
with moisture from the paper.

Very large dryers are usually divided into two of three sections, and these
should all be separately driven and have cone pulleys for easy adjustment of
the draws.

The drums themselves should be driven by endless cotton belts running
on their edges, in preference to cog-wheels, as the draws and tension are much
easier, and any slight variation in the size of the drums, due to wearing away
of the wooden spars, has less effect in causing uneven tension between drums.
Endless trouble from creasing, especially on thin weights, will always result

AIR-DRYING

301

from unequal draws between drums, if cog-wheels are used, and especially if
there are too many drums in one section.

It is often an advantage to have three steam-heated iron drying cylinders
at the end of the dryer in order thoroughly to dry the paper after it leaves the
sparred drums. These cylinders should have woollen felts, and it will be found
that they also assist greatly in flattening the paper before it passes to the calenders,
besides enabling thick papers to be thoroughly dry. The heat must not be too
great, or the gelatine will be made too brittle, and the strength of the paper
will be greatly reduced.

A departure from the usual practice was recently adopted on a machine
having 120 drums. These drums were arranged in three tiers, but it was found
that the paper was often very flabby, due to imperfect ventilation of the room
in wet weather, and also the large number of drums required considerable
power to drive. Consequently the bottom tier, which consisted of eighteen
3 feet drums, was fitted with steam-pipes inside and about 3 inches away from
the paper. These pipes were led back and forwards across each drum twelve
times, in exactly the same way as are the steam-pipes under the hood of some
M.G. machine cylinders.

The pipes were divided into three sections, one for each six drums, in order
that the heat could be regulated for each section.

When this arrangement was in operation it was found possible to do away
with 100 drums altogether, and to get a better dried and harder handling paper
with only eighteen drums, and two extra drums with fans but without steam-
pipes immediately after the tub. This is, of course, a method that is applicable
only to the cheaper grades of tub-sized papers. Theoretically, the best results
should be obtained with air at a low temperature and low humidity, but the
practical application of this theory is not commercially possible. A very long
drying machine running very slowly would.be required, and the high moisture
content of our air during a great part of the year would render drying almost
impossible. Drying machines are therefore as nearly adapted to the general
quality of paper made in the mill in which they are installed as experience
shows to be approximately correct.

Apparatus for controlling the temperature and humidity of rooms is now
available, but is still troublesome and requires a good deal of attention.

CHAPTER XDC

DAMPING - SUPER-CALENDER - PLATE-GLAZING - CUTTING-
GUILLOTINE-SLITTING AND WINDING-SORTING AND

FINISHING

Damping .-The damping of paper is the first step to the finish or surface
given by. the super-calender. There is little necessity for damping paper that
is machine finished, the necessary condition of moisture being obtained by
judicious drying. Dryers for tub-sized papers are often fitted with two or three
sets of finishing rolls, and the paper is dried soft enough to take a good finish.

[Sternberg and Phillips

Fig. i 30.—Orion Spray Damper with Adjustable Nozzles

But where a higher and finer finish is required, it is necessary to damp the paper
to reduce the harshness of the fibres and soften them sufficiently, so that the
heat and pressure of the calender rolls can smooth and glaze the surface of the
sheet. A paper intended for super-calender finish is usually run through a few
nips of the rolls at the paper machine, and is damped before it runs on the reel.

One of the simplest and most efficient dampers is the brush damper. This
is a roll brush with hard bristles which dip into a shallow trough of water. As
the roll revolves, the bristles carry round a certain quantity of water. This is
flicked off by the bristles coming in contact with a doctor blade.

The depth of the water and the speed of the roll are varied to get the required
amount of water in the paper.

Another type is worked by means of air jets partly immersed in water

302

DAMPING

303

and blowing it on the web. This is very difficult to regulate, as microscopic
differences in the orifices of the air jets, and their immersion in the water, make
it necessary for each jet to be separately controlled, and the results of adjust¬
ments are not fully known until the paper is being super-calendered. Direct
sprays have the same disadvantage.

Filtered water is necessary and a high pressure, but under the best conditions

Fig. 131.—Watford Patent Aquamist Damper with Adjustable Nozzles

a small particle of any foreign substance may stop a spray or reduce its volume,
causing streaky and irregular finish.

Jets of water impinging on a glass or metal plate, so as to rebound in the
form of spray, form a very good damping arrangement, give good results and
little trouble.

A form of damper which is now falling into disuse is in the form of a brass
or copper cylinder cooled by an internal flow of water. Steam jets are made
to play on the outside surface, and the condensed steam in a fine film is trans¬
ferred to the paper. This form of damper does not give much variation in
volume of applied water, and is expensive owing to the use of steam. A felt-
covered roll, partly immersed in water, is sometimes used to wet a damping
cylinder.

304

MODERN PAPER-MAKING

Milne’s patent damper consists of a short travelling wire cloth, which is
made to earn' a certain amount of water in its meshes. Air jets blow this water
on to the paper. Any mesh wire may be used as required for the fineness of
the spray, and the speed and mesh control the quantity applied.

As only the amount of water carried can be blown on the paper, the damping
is very unitorm and regular. The cheaper grades of paper are damped on the
making machine. Better grades are damped and rewound. All paper should
stand for at least twenty-four hours before being finished, so that the moisture
will spread through the substance of the sheet and reduce inequalities of

It seems to be a very general idea that best results are obtained by having
the paper cool before it is damped. This entails more expense and labour in
the use of a damper separate from the machine, but very few mills work this
method. The usual practice for super-calendered papers is to damp the web
as it is reeled on the making machine, while still in a very hot condition. Quite
satisfactory results are obtained. As the damping, or application of water,
takes place immediately before the paper is reeled, very little evaporation can
take place in the short space of time before the sheet is covered by another layer
of warm and watered paper.

As warm water is more penetrative and diffusive than cold, it is only reason¬
able to expect that it will more readily force its way into the fibres and produce
more uniform damping when the paper cools. There is no doubt that the
results of practical experience go to prove that the most satisfactory damping
is that carried out when the paper is hot off the machine.

The Super-Calender

The super-calender (Fig. 132) is a stack of rolls usually eight in number,
but now being built with as many as sixteen. These are alternately of iron
and composition. The latter are built of discs of paper, made from cotton or
woollen fabrics and cotton rags and hemp. The laminations or discs of paper
are fitted on a heavy steel centre and compressed into a solid form. The roll
is then turned and buffed to the correct camber. The iron and paper rolls are
placed alternately, commencing with top and bottom rolls of iron. This
brings two paper rolls together in die centre of the stack. The reason for the
dse of iron and paper rolls is that the latter form what may be termed a cushion,
allowing the heated iron rolls to impart a high glaze to the paper, without the
blackening or crushing and reduction of bulk which take place between two
rigid iron rolls.

The two adjacent paper rolls bring the reverse side of the web into contact

SUPER-CALENDER

305

with the iron rolls for the second half of its passage, thus giving an equal \flqish
both sides.

The iron rolls are highly burnished and fitted for steam heating. The
bottom roll is made greater in diameter than the other rolls, in order to sustain
the weight of those above it. The other iron rolls are less in diameter than
the paper rolls. As all rolls ‘give’ under pressure, the calender rolls require

[Walmskys (Bury), Ltd.

Fig. 132.—Large Super-Calender for Newsprint

to be very carefully cambered. The weight of the rolls of an eight-roll calender
resting on the bottom one would be about 9 tons for a 90-inch machine and
about 30 tons with/weights full on. This size would take 25 to 50 h.p. at
350 feet per minute, according to the degree of finish and the quality and sub¬
stance of the paper being treated. The drive is either from the bottom roll or
the third from the bottom. In machines with sixteen rolls or more, the seventh
from the bottom is the driver, top and bottom rolls being assisted with belt
drive, to reduce slip or skid which is very destructive to the strength and
bulk of the paper. When not in use the rolls should be relieved of the lever

306 MODERN PAPER-MAKING

weights and lifted apart, so as to prevent the line of pressure producing a
flat place.

The newer type of calenders have a lifting device for that purpose. They
must be washed frequently with warm water and soap, or a little soda, to clean
the paper rolls from dust, grit, and resin or gelatine size. Care must be taken
not to use too much heat in the iron rolls while this is being done, otherwise
they will take the top skin off the paper rolls.

The latter being of a softer nature, any hard substance or wrinkle in the
paper is liable to make a bruise or an impression on their surface. For this
reason, extra precautions are necessary when "working on tub-sized papers;
any ‘slap’ or defect on the deckle edge should be marked with a ticket at the
drying machine and damper, and watched for at the calender, as a folded,
wrinkled or doubled comer will make a mark in the paper rolls. Hard knots
of rag fibre, ‘rolls’ from the machine apron and ragged deckle edges are to
be avoided.

In cheaper papers, the greatest danger lies in particles of metal or grit which
become embedded in the rolls and may pass from one roll to another, making
so many impressions that the marks become continuous all round the rolls.
This is the case when there are no doctor blades on the iron rolls. Many
calenders have none except on the bottom roll. A long run on a narrow width
web is bad for the paper rolls, as it upsets the camber, the pressure being heaviest
on the width covered by the paper. After such a run, the rolls should be cleaned
and run as long as possible with frequent applications of hot water and with
no weight on.

This will cause the compressed part to swell out to its normal size. Bruises
and imprints, if not too deep, may be cured by blowing a steam jet on the
damaged place or by applying cloths saturated with hot water. Any deep cut
or mark may be improved by a judicious touch up with very fine emery or
glass paper and afterwards washing it with hot water. This is a temporary
repair and only lessens the mark made on the paper, the proper remedy being
to have the roll rebuffed.

This is necessary in any case at longer or shorter periods, according to the
hardness of the rolls and the conditions they show after a certain time.

As an additional damping arrangement, it has been found of great assistance
to pass the paper through a cloud of steam and over a felt-covered roll before
it enters the first roll. Great heat and pressure give a high but not a permanent
glaze, therefore, for good class papers, it is better to put the paper twice through
the rolls with less heat and weight. When fimshing tinted papers, pressure and
heat should be kept very regular from reel to reel, as a great many ‘shades’
may be caused by varying finish-

PLATE-GLAZING

307

The mottled appearance of some papers is caused by bad damping— i.e.,
insufficient time for penetration and spread of the water, or the damper throwing
drops instead of spray—cloudy or patchy make of the paper, or strong fibres
that will not make a close sheet. In the last case the mottled appearance is
sometimes looked for and desired, to show up a strong paper.

Paper intended for a high finish should be specially made for such if possible.
The stuff should be beaten so as to produce a close sheet, with the addition of
some good china clay and starch. On the machine full use must be made of
the shake, and a heavy dandy roll run. If finish is "wanted to be- equal both
sides, the paper must be run through the second press and smoothing rolls
to eliminate wire, coucher and felt impressions.

Plate-Glazing .—A plate-glazed finish is applied only to high-class papers.
The plate-glazing calender is a machine consisting of a heavy frame carrying
two iron rolls. Just under the level of the nip are smooth metal plates, or
rollers, both at back and front. The action of the rolls is reversible and the
top roll is fitted with levers to apply pressure. The sheets of paper are placed
alternately with plates of copper, zinc or cardboard, until a pile, ‘book’, or
‘handful’, as it is called, is formed about i| to 2 inches thick.

The pile is laid on the metal platform or rollers and the rolls are started.
It is pushed into the nip and the rolls grip it and take it through on to the back
platform. On the rolls being reversed, the pile is pulled back through the nip.
It is then turned half round and the process repeated. The turning of the pile
is for the purpose of reducing the curl of the plates and paper and giving the
paper equal finish and expansion in the machine and cross directions.

The necessary amount of finish is obtained from the burnished surface of
the plates, the pressure and the number of times the pile is put through the
rolls. High finish is given by copper or zinc plates, low finish by cardboard.
One man works the machine, but it is sometimes necessary to have an assistant
turning the pile at the back for low finishes and helping to lift a heavy ‘book’
from die bench. Women are employed to lay the sheets of paper and metal
and to separate them afterwards.

A plate-glazed finish is very fine and silky, and the most permanent of all
finis hes. An extremely high glaze may be put on the paper, but if overdone
the sheet may be crushed out of all recognition. In any case, specks of dirt
are shown up very prominendy. One may look through hundreds of sheets
without finding a single one that is fauldess in this respect.

Unless trimmed, the edges of a plate-glazed sheet are slighdy rougher than
the centre, owing to the difficulty of laying the paper and metal plates so that
all the edges coincide.

Plate-glazing is a very expensive method, owing to the labour and time

MODERN PAPER-MAKING

308

required, and the extra broke made by the necessity of handling the sheets so
often. The hands of the workers are very frequently cut and scratched by the
plates, and if a slight injury is not immediately noticed, a great deal of paper
may be spoiled by blood-stains.

The crew of a machine consists of four women or girls, with the attendant
and an assistant. Practically the only papers that are now plate-glazed are
hand-made papers, and some super-quality machine-made writing and ledger
papers. The special qualities of silkiness and close texture necessary for the
smooth gliding of the pen point cannot be equalled by any other finish,
and its permanence is one of the special features of a super-quality ledger
paper.

While there will always be a certain but limited demand for expensive
plate-glazed paper, this method has to all intents and purposes been superseded,
by the super-calender; the finish given by this machine satisfies most ordinary
requirements. Hand-sized sheets, both hand- and machine-made, are also
finished by putting them one by one through a pair of iron or iron and com¬
position rolls, steam heated, and weighted when necessary. After a pile has
been put through, the sheets are half turned and then put through a second time.
This is a cheaper method, as two women do the work. The paper thus treated
is usually sold as ‘plate-glazed’.

It may be confidendy stated that only an expert can tell the difference
between a plate-glazed and a carefully super-calendered finish, and that only
when he has good samples of each for comparison.

Linen-faced and other finishes are produced by the same means as described
for plate-glazing, except that a sheet of linen of the desired texture is stuck on
to the zinc plate or laid between the plate and the sheet of paper. When the
‘book’ is passed through the rolls the pressure causes the linen threads to
make an impression on the paper, and the linen-faced effect is produced. The
impression is much greater when the linen is new, and it gradually wears away as
the linen becomes flattened.

These papers appear to be losing popularity at present, but they are very
pleasant to write upon.

The cost of linen facing is high on account of the amount of labour required
and the slowness of the operation, and also the high cost and short life of the
linen.

For cheaper papers an embossing calender is generally used. This con¬
tains a roll with a linen impression etched upon its surface. The paper is run
through in the same way as through a calender and the process is very
quick and less cosdy. The result, however, is not so satisfactory. The
embossing calender may be used to give all kinds of ‘ finish ’ to paper, such

CUTTING

309

as ‘watered silk’, imitation leather and names, designs, which in some cases
are almost indistinguishable from water marks.

Cutting.—It is very seldom now that we find a cutter attached to a making
machine, but this was once not uncommon. As the old type of cutter, known
as the ‘English’ or single sheet cutter, was limited in speed to under 65 feet
per minute, it was found to be uneconomical to keep back the speed of the
machine to suit the cutter.

There are still some machines, however, with this cutter attached. These
are used for making and cutting high-class writings and drawings ‘waterleaf’,
the sheets being subsequently hand-sized with gelatine, and as a high speed
cannot be attained with these papers the objection does not apply.

The ‘English’ cutter consists of the usual slitting discs or knives, which
are common to all cutters, and a reciprocating action chopper. After being
slit longitudinally, the paper is run over a large drum. This drum is moved
round, carrying the paper to the required length of sheet. The slit sheets fall
over a ‘dead’ knife, and are temporarily clamped as the moving blade swings
away and the action of the drum is stopped. The return swing of the table
shears off the sheets, which fall on to a moving felt or smooth inclined surface
and are ‘laid’ by hand by boys.

The web slackens back at each stop or clamping, and the slack is taken up
by a ‘dancing roll’, the tension being regulated by two large cone pulleys.
The length of the sheet is set by a screw adjustment in the crank which moves
the drum, and slight variations are made by hanging small weights on the
‘dancing roll’ and by a brake which checks the momentum of the drum.

A change of gear wheels enables the crank to make two forward movements
of the drum for one chop of the knife for very long sheets.

When cutting short sheets, the speed has to be reduced to under 45 feet,
owing to the vibration and the jar of the reciprocating parts. Only one web
can be cut at a time. This type of cutter is very accurate in capable hands,
and some may still be found doing good work in cutting water-marked papers
which must be in exact register.

Under modem conditions of speed and output the revolving cutter (Fig.
13 3) is now used. The chop knife is fixed on a revolving drum, thus eliminating
the reciprocating action altogether. For very short sheets two knives may be
used on the drum, but this is seldom carried out in practice, the usual procedure
being to cut double sheets and cut them in two on the guillotine cutter.

As many as twelve or more sheets or webs may be cut at one time, accord¬
ing to the thickness of the paper. If the filling is too heavy the bottom sheets
may be tom instead of being cut with clean edges. Two rolls thickened at
the centre pull the paper into the slitter discs. The tension between the feeding

3 io

MODERN PAPER-MAKING

rolls and the discs is maintained by two steel rolls about 3 inches in diameter.
These deliver the slit webs on to the dead knife edge.

The knife on the revolving drum, set at a slight angle so as to have a shearing
effect, chops the sheets as they pass over the dead knife, and they fall on to a
moving felt. The length of the sheet is regulated by the speed of the revolving
drum. This is set by changes of the driving pulleys, and finer adjustment is
made by expanding pulleys, enabling water-marked papers to he cut to register.

The carriage of the revolving drum and dead knif e is adjustable to cut the
sheets at a true right angle to the slit sides. This device is extended so far in
the ‘angle’ cutter that sheets may be cut at any angle. This is essential for
reducing waste in stamping out envelopes, etc. A very useful variation of the
ordinary cutter is the Duplex cutter, which can cut sheets of different sizes from
the same web. This enables the paper-maker to make full use of the width of
the machine.

Thus, if the machine is capable of making only 72-inch deckle, and the
order is for sheets 30x40 inches, the lot may be made one sheet 30 inches and
one sheet 40=70 inches, instead of 2 sheets 30 inches=6o inches.

The Duplex cutter has two revolving cylinders and dead knives. These
may be driven independently and at different speeds, one part of the web
passing over the first revolving knife and being cut at a different length by
the second.

An invention which has reduced the labour costs of the cutter to a great
extent is the automatic ‘layboy’. Formerly it was necessary to have a boy
to ‘lay’ each sheet as it came off the moving felt, so that a cutterman and
five boys was a usual cutter crew. With this device which ‘lays’ and ‘jogs
up the sheets automatically, a cutterman and an assistant can manage a
cutter.

A cutterman must be very careful and precise with his work. The setting
of the slitting discs is a very simple matter. The distance between each fixed
disc is accurately set with a good rule, preferably steel. The moving disc is
then brought into contact with the fixed disc, and this must be gendy done,
otherwise the hard edges may chip each other. Indeed, to obviate any risk of
this a sheet of thin paper should be used at the point of contact.

A very common mistake is to compress the spring of the moving disc too
hard, and thus cause the cutting edges to grate on each other and wear blunt
very soon. The setting of the length of the sheet is done in accordance with
the table of sizes and pulleys issued with each cutter. The driving belt of the
revolving blade must be kept in good order, and well tightened up with the
tension pulley or pulleys provided for that purpose.

Before starting the cutter, all tools and spanners should be accounted for

CUTTING

3 ii

and laid aside. A few sheets must be cut at full speed and carefully measured
and right-angled before doing the bulk, and the edges examined from time to
time for frayed or tom cuts.

In cutting water-marked papers, the water mark has to be kept in correct
position on the sheet. This will often necessitate cutting a fraction over or
under the size, as the length between the water marks is liable to vary a little,
especially in paper made on a machine with old-fashioned belt and packing
drive. A continual watch has to be kept as the sheets pass on the felt, and
any variation closely followed and corrected by the skilful use of the expanding
pulleys.

It will be recognized that the work of the cutterman, in keeping a good
and steady length, depends very much on the care taken by the machineman in
setting and working the dandy and the draws of the machine. It is advisable
to allow a fraction of an inch over the size—say, one-sixteenth—for the cut in
water-marked papers.

If the dandy roll cannot be made to register exactly the machineman should
notify his foreman, and also send a slip of paper with the reel, to warn the
cutterman what has occurred. If the length between water marks is too great, ■
the sheet must be cut to register the water mark, and then trimmed on the
guillotine. If it is too short, the water mark will continually run out of register
and compel the cutterman to throw out sheets until it comes approximately
correct. It will be found on close examination that all water-marked papers
cut to register have some variation in length of sheet. This is inevitable to a
certain extent, and if the variation is less than b per cent either way, the paper
may be considered commercially correct. If it is absolutely necessary to have
to supply a lot the exact size, the water mark on the dandy roll must be spaced
and tensioned to allow for tr immin g on the guillotine.

Haubold Supercutter .—This is a modem precision-built machine designed to
satisfy the demand for a cutter that will operate at high speed, cut with guil¬
lotine accuracy and handle all classes of papers efficiendy, whether large or small
orders. Cutting speeds of 600 ft. per minute and over are attained.

The machine comprises a heavy feeding press and cutting unit mounted on
robust side frames. The feeding press rolls are of special composition, ensuring
that all the webs of paper are fed uniformly to the cutting unit. The latter,
which is adjustable for true square cut, is driven through a positive, steplessly
adjustable gear which controls the speed of the rotating knife and thus enables
the length of cut to be accurately regulated.

The drive for the entire machine forms a totally enclosed unit which is
mounted on the cutter frame. Every step in the drive is positive so as to
avoid backlash, all main drives being effected through totally enclosed, precision.

MODERN PAPER-MAKING

312

chrome-nickel steel bevel gears mounted in roller and ball bearings. The
machine is direct motor driven through an electro-magnetic coupling which
incorporates an overload safety device and an automatic brake for stopping
the cutter as soon as the motor is switched off.

The whole of the equipment, while massive and robust throughout, is built

[Messrs. Masson, Scott and Co., Ltd.
Fig, 133.—Modern High-Speed Super-Cutter with Layboy

more on the lines of modem high-speed printing machinery than is customary
in paper-mill equipment.

The slitter gear, which is situated in front of the feeding press, is provided
with knife holders of a new design which give an exceptionally wide clearance
for feeding through the sheet. The bottom slitter knives, mounted on a stiff
one-piece shaft, are made in halves so that they can be readily changed to enable
each pair of slitter knives, and therefore the width of each slit web, to be adjusted
simply by turning one handwheel, the width of the web being read off on a
graduated scale.

On leaving the cross-cutting unit the sheets are transported to the layboy
on a system of conveyor bands. With the latest design of feed the paper run
is entirely horizontal right through the cutter. This facilitates handling and

CUTTING

313

helps to prevent turned-up edges, particularly at high speeds, when cutting only
one or a few’ w’ebs, and also in handling light-v’eight papers.

The automatic hydraulic overlapping lavboy enables the high speed of the
cutter to be taken full advantage of. It is actuated by oil under pressure supplied
by a pump driven by the main motor. The speed of the lavboy carriage is
first adjusted to suit the thickness of the bundles of paper by means of a hand-
wheel, and thereafter the lavboy carriage rises automatically as the height of
the stack increases. When the lavboy reaches the top of its run it is lowered
to the starting position in two or three seconds by simply opening a valve.

As the sheets are delivered from the cutter to the lavboy they are overlapped
like tiles on a roof, so that they can reach the stack at only a fraction of the speed
at which they have passed through the cutter. The sheets are thus easily
controlled on the layboy and are not liable to be damaged by the stop board.
A system of air nozzles above the layboy conveyor facilitates handling light¬
weight papers, and a further series of air nozzles at the end of the layboy float
the sheets gently into position on the stack.

The cutter and layboy are controlled entirely from a central push-button
panel. A number, of extra ‘stop’ push-buttons are fitted at convenient points
about the machine to enable the operator to stop it from whatever position
he may be in.

There are designs for simplex, duplex, and triplex cuttings, while models are
available for installation at the end of a board machine for which the new slitter
gear with single handwheel adjustment is used so that the width of slit can be
altered while the machine is running.

On the duplex cutters a special coupling is fitted to disengage the duplex
unit when cutting simplex only, and an automatic hydraulic stack equalizing
device is provided to compensate for the unequal height of the stacks when
cutting duplex.

Recently various auxiliaries for these cutters have been developed. Chief
among these is a push-button-operated attachment on the drive to the rotary
knife drum, enabling the length of cut to be varied by small amounts to locate
the water-mark on the cut sheet. Registration of the water-mark is controlled
by an operative as he stands at the layboy and watches the overlapped sheets
passing to the stack. With this equipment water-marked papers are being cut
accurately to register at speeds of nearly 400 ft. a minute.

The ream counter and tabber counts the sheets in reams of 480, 500, 516
sheets as required and inserts a coloured paper strip between each ream. This is
all automatic.

When handling papers which are'liable to give trouble due to static elec¬
tricity, the electric neutralizer has proved extremely useful. It discharges the

MODERN PAPER-MAKING

static electricity in the paper during its passage through the cutter, enabling
the latter to be run at higher speeds and minimizes broke. It is quite safe for
the operatives and takes practically no current.

It is usual to employ duplicate sets of reelstands so that one set of reels can be
loaded while the other set is being run off on the cutter. According to the
space available, various methods are used for bringing the new set of reels into
position for feeding into the cutter. Where the two sets of reel bearings are
arranged horizontally behind the cutter, one above the other, the top set of
reels is loaded by an overhead crane in the usual way while the bottom set of
reels is being cut. While the top set is being run off, the bottom set is
loaded in position by a trolley running on track rails arranged between
the stands. The trolley is provided with hydraulic raising and lowering gear.

By another method the two sets of reelstands are mounted on a tumable
which is rotated by hand or by an electric motor to bring a fresh set of reels into
position. In one case the sets of stationary reelstands have been mounted side
by side, and the cutter mounted on a travelling carriage, enabling it to move
sideways from one set of reelstands to the other.

The Guillotine.—The guillotine is an essential part of the cutting equip¬
ment. Its function is to trim or subdivide sheets cut by the rotary cutter. It
is the only cutter used in a ‘hand-made’ mill. It consists of a heavy frame
supporting a level table, on which the sheets are placed. A cutting or shearing
blade works diagonally in upright guides. In close contact with the cutting
blade is another blade which is blunt on its lower edge. The latter is worked
by a foot lever, and is pulled down on the handful of sheets, holding them
firm and solid, close to the proposed line of the cut. The cutting blade slides
down in contact with this blade with a sideways and downwards motion,
similar to that which is made by a knife held in the hand. At the same time
power is added to the clamp, to fix the paper more firmly.

The mechanism is so arranged that only one chop or cut is made by the
action of pulling over a lever. The blade then ascends, and stops at the top
of the guides, and the holding blade is released. The action is assisted by the
momentum of a heavy fly-wheel, which is automatically thrown out of action
when the knife ascends. An upright at the back of the table is movable to
take the required size of sheet The distance from this upright to the cut is
indicated by a sliding gauge at the side of the table, or by a gauge worked by
a steel ribbon. A side plate at right angles to the back plate is also provided to
enable dead square trimming to be done.

By means of this machine sheets may be trimmed and cut dead square, or
slit into small sizes. Small sheets are usually cut double on the rotary cutter
and cut into two on the guillotine.

SLITTERS AND RE-WINDERS

3i5

A very common size cuts 40 inches and requires about h.p. for ‘handfuls’
of about 4 inches thickness. Smaller sizes are used by stationers, who get their
paper in bulk and cut it into writing and ledger sizes.

Webs, Slitting and Winding .—As more printing and other processes are
being made continuous, the demand for paper in webs or reels in place of sheets
is increasing and likely to increase. For this reason the production of paper
in reels is becoming of more importance in every paper-mill.

A good reel of paper should be evenly and cleanly slit, and run up to the
required size or length with no breaks, cracks on the edges, hard or soft places,
or unequal substance and finish. All these cannot be obtained if the paper is
poorly made and finished, and faults which would not be apparent in paper
cut into sheets become very obvious when it is wound into reels. In the first
place, the wire and clothing of the machine must be in very good order. Ridges
or dirty streaks on the wire, uneven spread of stuff at the slices, worn or scored
couch roll covers, dirty wet felts, badly-cambered rolls, dry felts that have
become worn and thin in the centres, unequal couching, pressing, drying,
damping or finishing are the most usual causes of bad reeling.

Variations in substance are difficult to check, since the machineman is
handicapped by the fact that he must not spoil a web by tearing out and weigh¬
ing sheets, and has to keep correct substance by other means. An experienced
machineman will, however, come very near to being exact by keeping in dose
touch with his machine. At the end of every reel a piece the whole width of
the machine should be taken and sheets marked and cut from the centre and
both sides, so as to cover all the width of the paper. Damping and drying
should be spedally watched, since the success of the super-calender finish will
depend on this being regular all across the web. A slight extra damping at
any one place will produce a higher finish, which will show as a soft place
when reeled. This may be easily so serious as to cause the paper to be creased
on the slitter and winder.

Slitters and Winders .—These are of two kinds, friction and drum winders.
The friction winder has slitter discs, which are identical with the rotary cutter
discs and slit the paper in the same way. Each slit web is wound on a separate
spindle by a friction arrangement similar to that on the making machine. This
is not a very efficient machine, since the tightness of the web depends entirely
on the strain the paper will stand without breaking, so that the webs are soft
and bulky. They are therefore very liable to damage in transit and become
lopsided on standing or being packed. This causes breaks on the printing
machine, as the result of the jerky motion of the unbalanced reel. The drum
winder, as its name implies, winds the web by contact with one or two
cylinders by its own weight, and is regulated by levers at the spindle ends.

3i6 modern paper-making

As the weight of the web increases, the paper is pressed harder to the cylinders
and wound tighter, which is the reverse of the friction type, where the pull
of the friction has less effect as the web increases in diameter. The weight of
the levers is so applied that the web can be partly supported to ensure regular
pressure from the start to the finish of the reel. In the drum winder all the
slit webs are wound on one spindle, strawboard centres of the requisite width

[Messrs. Masson , Scott and Co. t Ltd.

Fig. 134._Voith type High-Speed Slitting and Rewinding Machine

being put on the bar and kept tight and in position by an expanding device.
The paper is wound by the action of two cylinders travelling close together in
the same direction, the webs being in contact with both. The cylinders are
sometimes spiralled on the surface, outwards from the centres, to reduce the
chances of creasing. If only one cylinder is used, the web is pressed against
it by means of levers at the spindle ends, or else it runs directly on top of it.
When it is necessary to reel two webs of different yardage a four-drum winder
is used. By this means two webs of different lengths may be run off at the
same time from the same reel.

SLITTERS

317

A very simple and efficient winder has a cylinder about 9 inches in diameter
formed of sections which fit on to a centre. These segments are of various
lengths so that slitting knives in the form of thin steel discs may be introduced
between them at the required distances. The whole is fixed bv screws and
lock nuts at each end.

Cutter discs cut the side shavings, but the actual splitting takes place on the
cylinder on the top of which the web is run. This machine has the advantage
that the split edges cannot run into each other, the cutting discs protruding

from the cylinder about l inch. On winders where all the splitting is done by
ordinary cutter discs it is often a matter of difficulty to prevent the cut edges of
adjacent webs interlocking. It is usual to have a flexible steel bar over which
the paper is dragged, and which is bent by set-pins by the attendant into such
shapes as to keep the cuts open. On other winders the slitting is done by means
of small steel discs attached by rocking levers suitably weighted to a cross¬
bar. They are moveable sideways on the bar for adjusting to the breadth
of the web required. Being fixed between two circular plates * inch less in
diameter, they are thereby kept from being jammed in the cut by the pressure
of levers, and in contact with the web coming off the drum. An attachment

MODERN PAPER-MAKING

318

which is almost indispensable for a winder is an indicator showing the length
of paper that is wound. Immediately the webs are taken off the winding
spindle hard wood plugs should be driven into the open ends of the centres
to prevent the pressure from buckling them inwards, as the outside edges of the
paper swell by absorbing atmospheric moisture.

When a break takes place the winder is stopped, the broken edges
are cut square, and joined with gutta-percha tape or paste. A hot iron
is pressed over the join to dry and fix it, and a slip is put in to indicate
its presence. A piece tom from the edge should also be marked in the same
way.

In order to run good tight webs, such as will run off well on the newspaper
presses, it is essential that the webs should be tightly wound from the start,
and all joins must be very carefully made, especially at the edges. Voith and
Cameron machines are excellent for this work.

Sorting and Finishing.—After the paper has been cut it passes to the ‘salle’
or finishing room to be overlooked by women sorters, who remove damaged
or faulty sheets, and it is then ‘told out’ or counted by tellers in reams con¬
taining a certain number of sheets, after which it is weighed, tied up and put
into store, or packed up in bundles of two or more reams and dispatched to
the customer.

Obviously this sorting department is a very important place, and calls for
very strict and careful supervision if the good name of the mill is to be pre¬
served. Generally speaking, the finer the qualities of paper being made the
more careful must the sorting be, for while a few specks of dirt may not be of
much consequence in a sheet of cheap printing or wrapping paper, they cannot
be allowed to pass in a sheet of good writing paper.

In the sorting room of a mill the light must be good, and must come in
through windows facing north if possible, otherwise blinds will have to be
arranged on the windows to lessen the glare of the sun. It is always best to get
most, if not all, of the overhauling or sorting done during the hours of daylight,
and this is of paramount importance if the paper contains different shades which
have to be picked out and packed separately.

The girls generally stand at benches with the pile of paper to be sorted on
their right-hand side. In front of them they lay the good or perfect sheets,
which they jog up’ periodically into a neat pile. It is usual to have an arrange¬
ment of bricks on wooden elbows, in order to form a kind of frame into
which the size of paper being sorted will fit. This helps to keep the pile straight
and tidy.

If they are sorting three grades—‘good’, ‘retree’ and ‘broken’—they will
need to make three piles, the good in front of them, the retree over on the

SORTING PAPER

3i9

left-hand side and the broken at the back. Finally, the bad or useless sheets,
such as those with holes, creases and pieces tom off, may be put in a basket,
or anywhere else convenient, ready to be taken away to the beater room to be
used over again.

According to trade custom good or perfect paper is paid for at full price,
retree at an allowance of 10 per cent, and broken, if taken, at an allowance of
20 per cent. The question as to what constitutes a good sheet and a retree
sheet must be decided before the paper is sorted, and this is usually done by

[Abbey Mils, Greenfield, X. Wales
Fig. 136.—A Well-Lighted Sorting and Finishing House

the salle foreman or forewoman in conjunction with the manager, several
factors having to be taken into account. In the first place, the paper must be
equal to the sample, subject to the price being paid for it, and subject also to
the known requirements of the customer. Some customers are much more
difficult to please than others, and seem to imagine that it is possible to get
the best all-rag papers absolutely free from specks of dirt. Those who have
had a wide experience of the ‘fine’ trade will know that it is a practical im¬
possibility to get a sheet of all-rag paper absolutely free from all small specks,
so that the sorting of such papers resolves itself into the determination of the

320

MODERN PAPER-MAKING

amount of specks which may be allowed in a good sheet, and this can only be
arrived at by long experience in sorting such papers.

The sorters, who must have experience, while referring doubtful questions
to their forewoman, use their own judgment as to what shall constitute a good
sheet, and any sheet which does not quite reach this standard is placed on one side
to be sold as retree. Those which contain blemishes in the third degree are put
among the broken, and obviously fault ) 7 and useless sheets are sent back to the mill.

[Greenfield Paper Mill

Fig. 137. —Examining, Cleaning, Banding and Packing Cons of Cigarette Paper

So far we have dealt only with dirt or blemishes in the paper, and these
may consist of all kinds of foreign matter, such as pieces of metal from the beater
knives, chips from buttons, etc., small pieces of rubber, specks of improperly
dissolved dye, splinters of wood, shive, shine, froth and many other thin gs.

Besides dirt, there are other things which may spoil an otherwise perfect
sheet of paper; and the women must be on the look out for light or heavy sheets,
which must not be allowed to pass, sheets which are too low or too high in
finish, and those in which the water mark is defective, or, in the case of a paper
in which the mark has to register, is out of place.

PAPER SORTING

321

In jogging up’ the sheets the sorter will observe those sheets which are not
cut square, or are too long or too short, or cut with ragged edges.

From the foregoing remarks it will be seen that the sorters’ work requires
experience and skill, and, above all, great care and concentration. A good
sorter works at a very fast speed, and rarely allows a fault)' sheet to pass, so
that she is a valuable asset to the salle, and gets the best qualities to overlook.
New sorters gain their experience on lower grades of paper, which do not
require such careful sorting. It is usual for good-class papers to be turned as
they are being sorted, so that both sides of the sheet can be examined, and
during the turning movement the appearance of the ‘look-through’ of the
sheet and also the water mark can be seen. In this way crushed sheets, and
blurred or otherwise imperfect water marks, can be seen and thrown out.

It often happens that a small piece of wire, forming part of a letter or design,
becomes detached from the dandy roll, and this may not be immediately
.observed at the machine, so that, unless the sorters are very careful and skilful
in watching the mark, they may let through a quantity of paper with the
defective mark, and if it is detected by the customer the paper is quite likely
to be rejected.

In the sorting of water-marked papers for postage stamps and security
papers, which are needle-cut and have to register exactly, it is necessary for
each sheet to be placed in a frame with a glass back, in order that its exact regis¬
tration may be carefully checked.

In order that the work of sorting may be thoroughly and carefully carried
out, there must be adequate supervision of the sorters by capable forewomen,
whose duty is to watch the sorters regularly, check their work by occasionally
resorting it, and removing any faulty sheets which may have slipped through
unnoticed. It is also very necessary to watch that a sorter working very fast
does not crumple the sheets by rough handling. Many sorters otherwise efficient
and careful have this fault, which is mosdy the result of gripping the sheets
too tightly with the left hand.

After the paper has been sorted it is carefully jogged, and stacked ready to
be counted into reams. The counting or telling is quickly done, usually by
women, who turn over the edge of a handful of paper and run their fingers
across the edges of three, four or more sheets at a time. Often it is necessary
to ‘quire mark’ the reams, and in this case a slip of coloured paper is put in
after every twenty sheets.

Unless the paper is specified all ‘insides’ or each quire perfect, it is usual
to place a quire of retree at the top and bottom of each ream, so that if the
paper is slightly marked or creased by the tape or during handling, it will
generally be the retree quire which will suffer.

322

MODERN PAPER-MAKING

As soon as the reams are counted they should be weighed and packed in
ream wrappers and fastened with gummed tape; they are then marked with
indelible ink lettering as required.

Usually a special brand label is pasted to the ream wrapper, and in this
case the wrappers must be thoroughly dried before being used, so that the wet
paste will not break through and cockle the paper inside.

When reams are tied with tape the operation should be neatly and regularly
carried out, so that when the reams are placed in a pile all the tapes will corre¬
spond and give a neat appearance. Attention to these details always helps to
give a good name to the mill.

In some cases gummed tape is used for closing the ream wrappers, but this
has the disadvantage that it necessitates a fold of wrapper being placed over
on to the top of the ream, instead of being folded in at the end, which does
not make such a neat package.

When proper knots are used to tie up the tape, the reams can be unfastened
quickly and without spoiling the wrapper when only a sheet or a quire
or two are required, or when the paper is being examined at the buyer’s
warehouse.

Before the paper is sent away it is usual to tie up two or three reams into a
bundle, and this is done by means of strong and bulky wrappers, in order to
protect the paper from damage in transit, and to lessen the handling and packing
of it in trucks or lorries.

It is important that valuable papers should be well and securely packed,
and sufficient attention is not always paid to this important point. A good
paper is worth a good wrapper and will always benefit from it. To realize the
importance of this it is only necessary to visit the warehouse of one of the large
wholesale stationers, and see the conditions in which the consignments of paper
arrive from different mills. Some are neat and untom, while others are often
untidy and the "wrappers are all tom and gaping, exposing the paper to li g ht,
dust and moisture. While some damage can no doubt be attributed to rough
handling in transit, it will generally be found that the packing is greatly to
blame.

In the case of large and unwieldy reams, especially if the paper is thin in
substance, it will be necessary to pack the bundles between light wooden frames
or boards, in order to prevent the reams from bending and buckling when being
loaded and unloaded.

Formerly, this method was adopted "with most fine papers, but nowadays
it is generally confined to special lots and .unwieldy sizes. These boards and

frames are the property of the mill in most cases and are returnable.

Various methods of packing have to be adopted for shipment of paper to

PAPER FINISHING

323

the Continent and for export. Waterproof-lined cases have to be provided
for gummed paper for postage stamps, and the lining is usually of zinc; the
top layer of zinc is soldered down when the case is full. Other packings re¬
quire the paper to be baled in a hydraulic press between strong boards with
wire hoops.

The overhauling, counting and packing of all other qualities of paper are
the same as those for fine writing papers already described, except that the

[Hall and Kay

Fig. 138.—Hail and Kay Patent Paper-Conditioning Plant for conditioning Paper

CONTINUOUSLY IN MACHINE ROLLS

same standard of cleanliness is not usually expected, and cheaper forms of
packing and tying up are used.

Wrapping papers, news off-cuts and cheap papers generally do not have
wrappers extending over the ends. In the case of large sheets which cannot
conveniently be handled flat, they are folded once or twice, making a more
compact and rigid bundle.

The loading of reams and reels of paper into lorries or railway wagons
must be very carefully carried out. Straw should be placed on the floor and
this should be dry. The truck or lorry should be filled as full as possible,
so that the reels or reams have no room in which to slide about, and all reels
should be securely scotched to prevent rolling. Considerable damage is often
done in transit owing to the goods not being properly packed by the sender.
Another very general cause of spoilage is the carriage of paper in lorries or

324

MODERN PAPER-MAKING

railway wagons that have contained coal or other dirty or oily material. It
is here that the value of a mill siding is apparent, as railway trucks can be
examined and swept clean, and if the floors are doubtful, a few sheets of coarse
wrapping may be laid down to protect the reels or packages. Mill lorries
should be similarly treated.

[Hall and Kay

Fig. 139 - Paper-Conditioning Plant, showing the Paper passing round the Sparred Drums

Paper Conditioning

Paper Conditioning, or maturing, as it is sometimes called, has come into
considerable prominence during the last few years, and is one of those addi¬
tional processes which have been forced on paper-makers by the demands
of the printer, who in his turn has been forced to seek for paper which will
give him trouble-free running on his fast-running automatic machines. To
put it very simply, paper conditioning consists solely in getting paper ‘into
balance with what has been termed a normal atmosphere’, which is generally

PAPER CONDITIONING

325

accepted as being an atmosphere of 60 5 F. temperature and 60 per cent relative
humidity. In an atmosphere such as this there will be approximately 345
grains of water as vapour in a cubic foot of air, and this corresponds to a moisture
content in the paper of between 6 and 7 per cent. Paper which is composed
principally of cellulose is hygroscopic— i.e., it will take in or give up moisture
according to the conditions of the air in which it is placed—and it will alter
in moisture content comparatively quickly. This fact is responsible for wavi¬
ness on the edges of the finished paper. In the majority of mill-finished
Fourdrinier papers the moisture content of the finished paper as it is reeled
up varies considerably, and can be as low as 1.5 per cent and as high as 4.5 per
cent according to the surface given—a very highly finished paper which has
been run over hot calender rolls may contain very little moisture; on the other
hand, an offset paper which has had less rolling may contain the higher per¬
centage. It is impossible to give any definite figures on this because of the
factors which govern this content at the reel end. It will be apparent that the
paper is deficient in the moisture necessary to bring it up to the balance with
normal atmosphere mentioned earlier. Provided that a normal atmosphere
has free access to the paper over the whole of the sheet for about 15 minutes
the sheet will of its own accord absorb sufficient moisture for it to arrive at
its correct moisture content. Under general mill conditions, however, this
free access is not given to the paper; it is reeled, cut, sorted, and packed, and
during the whole of that time it is in bulk, and in consequence moisture can
be absorbed only by the outside edges of the paper. In the case of a ream it
will be obvious that the centre of practically every sheet of that ream will be
unable to get air. The outside edges, however, are exposed to the atmosphere
and absorb moisture. The absorption of moisture causes the paper to expand,
and because that expansion is held back by the unexpanded centre portion of
the sheet, the edges develop into a series of waves, and it is this waviness and
irregular tension in the sheet which causes the printer so much trouble. Paper¬
conditioning machines are now available for dealing with this, and all work
to the same principle—viz., of passing the continuous web through a number
of passes in an atmosphere which will impart sufficient moisture to the paper
in its passage through the machine to bring it ‘into balance’ -with the normal
atmosphere.

CHAPTER XX

THE TESTING OF PAPER-TRANSPARENCY AND OPACITY-
DURABILITY AND STORAGE OF PAPER

There are a great many features which require to be considered in the testing
of paper as usually carried out at the mill or in the mill laboratory. We have
no intention of trespassing on the sphere of scientific research, or of describing
intricate processes, but simply to give such information as will be readily
understood and ample for commercial purposes.

In the making of all papers it is obvious that some standard for quality must
be aimed at, and before going further we must define what we mean by quality.

This expression as applied to paper is capable of a very wide definition;
literally, a paper of ‘high-class quality’ is one made by hand from the best
materials, such as new rags; sized by hand, loft-dried and possibly plate-glazed,
and, in fact, a paper of superlative excellence.

In the broad sense of the term, however, a paper may be of excellent quality,
no matter what its composition, provided that it is eminently suited for the
purpose for which it is to be used.

Newsprint, for instance, may be described as of very high-class quality,
and the term may be perfectly correct and logical, though it cannot he said
that newsprint, as paper, is of high quality'.

Therefore, in testing or judging quality, some standard is necessary for
comparison, and as a basis on which to found a judgment. This basis, as between
the paper-maker and his customer, is generally defined in terms of price and
a certain sample to be matched, this sample being mutually agreed upon at
the time the order is placed.

It often happens, however, that a prospective customer sends a sample
and wishes to know the price at which it can be matched. Occasionally, too,
instead of a sample, a general indication of the kind of paper required is given.
If the paper supplied is a good match to the sample, taking into consideration the
price asked for it, the customer may consider the paper to be of ‘good quality’.

Therefore, in testing paper, quality must be taken as a comparative term, all the
characteristics of the paper being placed against those of the sample individually.

For this reason it is necessary to be able to test a sample and ascertain its
composition, etc., before submitting an estimate of price, and, later, for the
purpose of being able to match it accurately.

326

PAPER TESTING

327

Ud to within a few rears ago—and indeed in some mills to-dav— no real
tests were made. The manager simply looked at the paper, rattled it. tore a
comer, and perhaps compared it with some of his stock lines, and then made a
guess at the price at which he could profitably match it. If the customer
thought the price too high, he went elsewhere, or offered less until terms were
mutually agreed upon.

The paper-maker, haring no real knowledge of the composition of the
sample, sometimes found his paper returned as unsuitable, or was compelled
to concede a reduction in price in order to get it accepted.

As trade and conditions are at present, these haphazard methods are useless.
The paper-maker must know exactly the composition of the sample, and he
should also know for what purpose the paper is to be used. He can then quote
a price which, while securing more or less profit for his mill, is still low enough
to stand a fair chance of securing the order against other competitors.

If his tests have been fairly accurate he need have little worry as to the
results of his making, and by testing the paper at the various stages of manu¬
facture he can check any mistake and produce a satisfactory match to the
sample. But as the natural ‘cussedness’ of paper-making materials, machi¬
nery, and workmanship may cause variations during the making of an order,
provided these variations do not go very far from the sample, the paper may
still, within certain limits, be called a ‘commercial match’. The limits of some
of the variations, such as substance, are defined by the rules of the Associations
of Paper-makers and Stationers. Other variations, such as colour and opacity,
which are not amenable to exact measurement, are not so defined, and are left
to the decision of the customer.

This leaves openings which are sometimes taken advantage of by unscru¬
pulous firms. A paper, for instance, may be rejected as not being an exact
match to the sample for colour. This may be quite true, as it is very difficult,
and in some cases almost impossible, to give an absolutely faultless match for
colour. After a great deal of correspondence and argument, and threats to
withhold future orders, the mill is forced to concede a percentage of the price,
and the paper is then accepted. Although the paper-maker is well aware that
his paper is a good commercial match, and would be considered so by a com¬
petent independent judge, he dare not force acceptance by legal action, well
knowing that it may cause him serious loss of trade. Thus the importance of
testing paper, so far as it can be tested with certainty, will at once be recognized.

Some of the qualities of paper, as compared to the sample, are matters of
individual judgment and opinion; others are capable of being definitely
demonstrated.

Constant Humidity.—It has been shown that observations on most paper

MODERN PAPER-MAKING

328

tests vary widely on the same sample if tested under different conditions of
relative humidity and temperature. An observation of folding endurance
carried out at 70 per cent relative humidity may be double the value obtained
on the same sample at 60 per cent relative humidity; it has become common
practice, therefore, to ‘condition’ paper specimens before tests are made. The
usual recognized standard atmosphere for the conditioning and testing of paper
is at 65' per cent relative humidity at 65° to 70° F. It is advantageous that the
paper-testing laboratory is a constant humidity and constant temperature
room, having double doors with an air lock between and preferably double
windows. The walls and ceiling, besides being reasonably thick and

heat insulating, are better glazed or

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MULLEN TESTER
HOUl. - 2 .

gloss painted rather than plastered, so
as to reduce the water-absorbing surface
to a minimum. The disposal of the
paper-testing apparatus in the room
must be given careful consideration, so
as to avoid the room being unduly
large and giving rise to difficulties with
air circulation. Provision should be
made to supply conditioned air into
the room at the rate of about 30 cubic
feet per minute per man working in
the room. Temperature control of
the incoming air, through the medium
of a thermostat, does not present
any serious problems, electrical heat¬
ing of the air in winter being
possibly the most convenient, and water cooling in summer where necessary,
although it may be found that this latter recourse is unnecessary by careful
choice of room site. Humidity control is usually brought about through the
length changes of a humidity sensitive hair or a sensitized parchment strip.
Constant humidity cabinets are also available in which paper specimens may He
for some time before testing in order that their moisture content may attain
equilibrium with the controlled atmosphere in the cabinet.

Strength .—There are several recognized apphances for testing the strength
of paper. The most popular, rehable and easiest to manipulate is the Mullen
paper tester (Fig. 140).

In this machine the paper is clamped over a circular diaphragm of thin
rubber, 1 square inch in area. By turning a wheel, a piston forces glycerine
against the under side of the diaphragm. The latter presses against the paper

Fig. 140.—The Mullen Paper Tester for testing
the Bursting Strength of Paper

STRENGTH TESTING

329

with increasing force until the fibres give way and are pulled asunder. The
pressure at the bursting point is recorded on a dial by a pointer.

On a sheet of large post (i6ix 12 inches) about 12 bursts may be taken
to set a correct average. These mav be 3 along each long side, 2 along each

short side and 2 near the centre. The
rubber diaphragms should not be used
too long, as they lose their elasticity,
and low readings may be expected.
Generallv the difference between a

new and an old diaphragm may be

[H. E. Messmer

Fig. 141.—Schopper-Dalen Bursting
Tester

[Goodbrand and Co.

Fig. 142.—-New British Bursting Tester, with
Latest Type Diaphragm Control Mechanism

taken as about 10 per cent, but if possible it is desirable to check results by using
two testers. If the sample is tested on the same machine as the finished sheet
a more accurate comparison may be made.

The paper must be firmly clamped, but not so hard as to produce stress

33 °

MODERN PAPER-MAKING

on the edges of the area to be tested. The rate at which the wheel is turned
produces different results. About two to three revolutions per second is a
usual speed. A slower speed gives the fibres longer time under pressure, when
less is required to tear them apart. A uniform, not jerky, movement of the
wheel is essential. The highest bursting point of paper is reached at normal
humidity', about 5 to 8 per cent moisture. If the paper is above or below

this moisture content, lower readings
are obtained. It is as well to remem¬
ber that a paper newly made may be
expected to gain up to 10 per cent
increase of strength when properly
matured. Sometimes different read¬
ings will be obtained according to
whether the top or under side of
the sheet is clamped next to the
diaphragm.

The sheet may be tested both ways.
Two operators sometimes get differ¬
ent results on the same sheet, but two
experienced men generally come very
close in their averages.

There are other paper testers of
this type, such as the Ashcroft and
Schopper-Dalen,but they all work on
the same principle, differing only in
structural details.

Certain modifications have been
recommended for use with the
Schopper-Dalen type of tester in the
[h e uessmer diaphragm pressure control mecha-
fig. 143.—schopper tenshe tisthr arranged for nism. These are incorporated in

Electric Dktve the more recent instruments made

by Goodbrand, of Stalybridge, the latest of which is illustrated in Fig. 142.

Whenever possible, the operator who tests the sample should also test the
finished sheets of the paper. In connection with these tests, it is necessary to
point out that there is no corresponding proportional increase of bursting
strength as the substance of the paper increases. Some paper buyers seem to
be under the impression that this is so, and we know of an instance where a
sample was sent to be matched for quality, but the paper had to be of a
much heavier substance. When the sheets were sent in, the paper was

STRENGTH TESTING

33 i

rejected, because the bursting strain did not increase in exact proportion to
the substance.

The Schopper paper tester (Fig. 143} is a modem adaptation of the old
method of paper testing. Before the introduction of this machine, a strip of

Fig. 144.—Thnsiih Strength and Stretch Testing Machine
This is the latest and most improved type and is British made

paper of a certain length and breadth was suspended from a clamp; another
clamp was attached to the bottom of the strip and weights were added until
the strip broke. When the Schopper is used, the breaking strain of strips cut
from across the web, and also in the machine direction, is taken, and a short

332

MODERN PAPER-MAKING

calculation gives an average or mean breaking strain. The strip of paper,
fixed between two clamps, is used to raise a heavily-weighted lever by means
of a wheel and gearing.

The lever remains automatically fixed by a pawl at the point where the
strip is broken, and a graduated scale and pointer show the breaking strain in
pounds. In addition, the stretch which has taken place is also recorded.

Like the Mullen tester, the Schopper requires the wheel to be steadily turned,
and where great accuracy is required this may be done mechanically by a small
electric motor, or by means of hydraulic pressure. Older machines of this
type depend on a spring for the tension, and they are accurate enough on the
whole, but as the Schopper machine is the standard tester, they are falling into
disuse.

The more recent motor-driven instruments of this type, by Goodbrand—

illustrated in Fig. 144—have a

[H. E. Messmer
Fig. 145-—Folding Tester

two-speed gear box giving alternative loading
rates, and a graphic recorder indicating the
stress/strain diagram of the paper specimen
examined.

When using these machines which require
a strip, it will be found that strips cut in
the machine direction have a greater tensile
strength than those cut across the web. Hand¬
made papers show little difference owing to
the shake being applied in both directions
during making.

While the Mullen and Schopper types do
not show results in any relation to each other,
it will be found in practice that either machine

will bear out the evidence of the other.

Folding.—Closely allied to the question of strength is that of ‘folding’.
Envelope papers, paper for bags, etc., require to be capable of being folded
without danger of the paper breaking at the hinges and folds.

Folding Endurance .—The most widely used instrument for the determination
of folding endurance is that by Schopper (Fig. 145). A strip of paper cut to a
standard template is clamped under a known arbitrary tension and subjected to a
continuous backward and forward folding effect. This folding effect is produced
by a slotted steel plate, which through a reciprocating motion folds the strip
until fracture takes place. The number of folds required to produce fracture
is recorded on a dial, the operating mechanism of which stops at the timp of
breakdown. The number of folds that a given paper will stand before fracture
occurs under a given tension offers a fair indication of its cohesive properties.

TEARING STRENGTH

333

It is essential that the folding endurance test is carried out in a constant humidity
room, since this test is very susceptible to change in atmospheric conditions.
A folding endurance carried out at 70 per cent relative humidity may be double
the value obtained on the same sample conditioned and tested at 60 per cent
relative humidity.

Tearing Strength—It has been claimed that the tearing strength is a better
criterion of paper strength value for practical purposes than either the tensile
or bursting strength. A popular instrument for the measurement of tearing
strength is the Marx-Elmendorf (Fig. 146). A specimen of paper is accurately cut
to a template in such a manner that two parallel slits form a centre tongue, the
equivalent of the start of a double tear. The outer tongues produced bv this
cutting are held in a fixed clamp, while the centre tongue is subjected to the
load of a pendulum to continue the tear.

The load necessary to continue the tear is
recorded through a spring-loaded friction
pointer on the scale forming the pendulum.

Thus the instrument records the work
done in continuing a tear in a given
length of paper, and not the resistance of
the paper to the starting of a tear. The
magnitude of the tearing force as deter¬
mined above is very small compared with
the breaking load under tensile stress for
the same sheet of paper. Like the tensile
strength, it is possible to determine the rela¬

tive tearing strength in both ‘machine’ and
‘cross’ directions, a factor offering some
indication of fibre orientation in the sheet.

[Renold Marsh
Fig. 146.—Elmendorf Tearing Tester

Thickness.— The thickness or ‘bulk’ of paper is measured by small instru¬
ments known as micrometers (Fig. 147). These are very delicate instruments
graduated to thousandths of an inch, and they work either by spring pressure,
which is always constant, or by means of a fine screw, the head of which is
fitted with a friction arrangement, so that when the face of the screw presses
the paper against the fixed face the screw cannot be turned further, and so the
paper is not squeezed.

The spring micrometers have a dial, divided into thousandths of an inch,
and a pointer shows the thickness of the paper under test.

It is usual to place four or more pieces of paper in the tester at a
time, for in this way the ever-present irregularities in the surface of
the paper are taken into account, and it is obvious that this is necessary

334

MODERN PAPER-MAKING

if the thickness of the paper is required to give any indication of the bulk of
a book, etc.

Substance—The substance, or weight per given area, or more commonly
the weight per ream of a definite number of sheets, is ascertained by means
of a pair of scales and weights. The paper is cut to the required size, such as
20x30 inches (double crown), 174x224 inches (demy), 164X21 inches (large
post), and a sheet of this size is weighed, either by a balance scale and
special weights, or in a special lever scale, which has a graduated quadrant

plate, on which is engraved the weight per
ream of 480, 500, or 516 sheets. In these
latter scales a sample sheet of any desired
size may be weighed, so that it is an ex¬
tremely useful instrument for the machine-
man to have on his table, enabling him,
as it does, to cut a sheet of the exact size
of the finished paper and weigh it, thus
avoiding the necessity of calculating the
weight in the usual mill standard size,
such as double crown, etc.

It is usual in mills making paper of
many distinct sizes and substances to have
metal templates for all the more usual
sizes, so that the machineman may quickly
cut out a sheet for checking his weight.

Air Permeability— The permeability of
a paper to air is a guide to the degree of
calendering, coating, sizing, or beating.
The two most popular instruments for
this determination are the Potts perme-
r ability apparatus and the Gurley denso-

[H. E. Messmer 4.4 r . ... ' .

Pl „ Ti „ .. _ „ meter. The former is readily constructed

Fig. i + 7 -—Micrometer Thickness Tester r . J

from simple laboratory materials, and has
the advantage over the Gurley instrument in that the determination is made
at constant pressure. The sample of paper is held in a clamp of known dimen¬
sions and air is drawn through the sheet under constant pressure by means
of a water aspirator fitted with a Marriotte tube. By measurement of the
volume of water passing from the aspirator in a given time it is possible to
report the air permeability of the paper as volume per unit time for air passing
at a given pressure through a known area. A mathematical interpretation of
the significance of observations by this apparatus has been given.

SUBSTANCE AND THICKNESS

335

The Gurley densometer operates by allowing a cylinder of specified
characteristics, having a specimen of paper to seal its upper end, to fall freely
in a second cylinder containing oil. The paper is clamped between two orifice
plates having an opening of i square inch, and the inner cylinder is timed
for a given fall equivalent to a known volume of air being displaced through
the paper at the upper end. The permeability is then reported as the time
taken for the displacement of ioo c.c. of air. An improved type of this in¬
strument is now available in which the inner cylinder is sealed at the top and
air is forced through an inner tube extending to a paper clamp at the base
of the instrument. It will be noted that the Gurley densometer does not permit
the passage of air through the paper specimen at constant pressure.

The Gurley smoothness tester is a development of the densometer. By
this device both sides of the sheet are subjected to an equal air pressure by the
equivalent of a densometer falling cylinder. The paper is supported between
two optical flat steel blocks with a centre opening connected to the falling
cy lin ders, so that the passage of air is outwards between the face of the sheet
and the steel block. The rate of flow of air across the sheet is determined by
inequalities in its surface, and so is a measure of smoothness and ‘finish’.

The degree of sizing of paper is usually measured by the rate of water
penetration. By means of the Currier apparatus the time is determined in
which a sample of paper is penetrated by water, the sample being placed on a
metal plate and covered with a wet felt. Liquid penetration has been followed
by a change in the light reflection on the upper surface of a paper sheet due to
a liquid penetrating from the under side, the reflection being followed photo-
electricafly.

Of interest to the printer is the softness or compressibility of paper. The
Bekk hardness tester is used for observations on this property. The instrument
consists of a metal cylinder with a spherical end attached to a rod and free to
move in a vertical plane like a pendulum. The paper sample is clamped against
a hard steel plate vertically below the pivot of the rod. The metal cylinder
is withdrawn through a standard arc and after lightly inking the spherical end
is allowed to impinge on the paper sample. The area of the ink spot produced
on the paper is a measure of its compressibility.

The rebound arc of the cylinder is also measured, since this affords an in¬
dication as to whether the paper will be permanently deformed and embossed,
after printing. A paper with a small rebound arc, and therefore low elasticity,
may be permanently indented during printing.

Another attempt at deriving a ■ numerical measure of a rather obscure
paper property is afforded by the Bekk resistance to ‘picking’ apparatus.
‘Picking’ is a difficulty experienced on printing machines where small

MODERN PAPER-MAKING

336

surface areas of paper become detached and adhere to the printing rolls. It is
claimed that this apparatus indicates the relative freedom from picking’ in
different papers. While the apparatus may give a broad indication as to the
relative merits of different papers, the conditions of the test are not strictly
comparable with those encountered in practice on a printing machine.

An instrument is offered by Schopper to measure the ink-absorption pro¬
perties of blotting papers. The same manufacturer is also putting out a con¬
tinuous bendins; tester which it is claimed has overcome some of the fundamental
failures in the design of the folding endurance tester.

During recent years the optical properties of paper have received much
attention, and at the moment quite a number of instruments are marketed
to determine both the opacity and gloss of paper. The use of some of these
instruments is restricted to the routine checking of batches of similar papers
and do not give reliable observations on papers of widely different character¬
istics. In the main their operation depends on the measurement of the amount
of light from a standard source passing through the sheet (for opacity) or
reflected from its surface (for gloss) through the medium of a photo-electric
cell. The choice of the photo-electric cell is important, it being essential to
use a cell system with the same colour response as the average human eye.
Amongst the more popular instruments for this purpose are the Westinghouse
Trans-O-Meter, the Bausch and Lomb Opacimeter, and more recently the
Lange reflection meter. A very high sensitivity in the measurement of white¬
ness is claimed for the Leukometer (Zeiss).

Composition.—A knowledge of the nature of fibrous materials of which a
sample is composed is of very great importance to the paper-maker. On that
knowledge the price is estimated; without it he may make serious mistakes.

Suppose, for instance, a sample is submitted and a price agreed on to match
it in all respects. The paper offered may be all right in all details, but may
contain a fibre that the customer does not want, and is not in his sample. He
would be quite justified in rejecting the making. It is not at all unusual for
papers containing wood fibres to be offered as matches to ‘all-rag’ samples
either through ignorance or a desire to make a little more profit, or to get the
order at a ‘cut’ price.

The microscope is a very necessary piece of apparatus in the identification
of the constituent fibres of the paper furnish, and useful work may be performed
with relatively simple apparatus. We have already (see Chapter I) indicated the
chief points of difference in the various fibres, and little difficulty should be en¬
countered in recognizing them. The paper specimen is disintegrated and stained
for examination, the Hersberg stain probably having the most wide application.
Whilst different fibres assume a different tint by the stain, this characteristic

OPACITY

337

tint is not the true medium of differentiation, the function of the stain being
to exaggerate the characteristic appearance of the fibre. A table of colour
reactions on fibres by the more commonly used stains is given in the Appendix.
Furnish may be approximately estimated by a count of the different fibres
present, although beating adds to the difficulty of such an estimation.

Transparency and Opacity .—Transparency in paper depends on the com¬
parative absence of light reflecting or absorbing faces or facets in or on the
fibres, minerals or other items of its composition. Any treatment—parch-
mentizing, waxing, finishing, fibrillation, or the addition of such substances as
size, starch, etc.—which tends to cause the fibres to pack closely together and
eliminate or fill up air space produces transparency by allowing light rays to
pass through the sheet more or less unbroken or unreflected.

For example, vegetable parchment before and after treatment. This paper
is beaten free and consequendy is very opaque, but after the manufacture is
completed it is the reverse. Blotting has its opacity from its bulk, which is the
result of quick and free beating with very sharp tackle, and the softness and
want of felting qualities given to the cotton fibres by treatment. Yet the same
furnish may be treated to produce a comparatively transparent sheet, if highly
fibrillated, sized and finished as a writing paper.

Envelopes to match must be opaque. To get this result the fibres must be
beaten long and free and, if possible, china clay and a lower quality of fibre
may be utilized.

The second press should not be used; this omission will give a little more
bulk and leave the under side of the sheet with a rough surface. All fillers
and colours of a mineral or pulpy character produce opacity. So also do all
dyes when used to get a deep shade, but a slight addition of a good blue dye
will give an increased transparency to paper. A poor or cheap colour always
gives a more opaque result than a good colour, owing to the greater quantity
required to produce a similar shade.

The transparency of paper generally is a good indication of the quality;
the better the quality the more transparent will the sheet appear, owing to the
greater care that has been taken in boiling and bleaching the fibres, and the
purity of the colour, size, etc. A finish given on the machine with iron rolls
gives a more transparent paper than the super-calender or plate glaze, owing
to the greater compression and loss of bulk. The colour and quality of water
used at the mill influence the transparency of the paper, so that one mill will
have difficulty in giving the opacity, and another the transparency or purity.

In the first case the stock may be dulled down with a touch of nitrate of
iron, and brought up to the colour with blue and pink; in the second, it may
be necessary to use a higher grade of stock and to touch up the shade with dye.

MODERN PAPER-MAKING

338

The use of broke or waste paper that has been boiled gives opacity, owing to
the boiling having reduced the colour of the fibres.

The Durability and Storage of Paper.—In the hurry of modem paper-making
the durability of paper is a subject that few paper-makers seem to consider.
A hundred years ago paper-making was a slow, not to say leisurely, process,
w r hen the result of the paper-makers’ labour was a thing to be prized and taken
care of. Books were carefully bound and treasured as lasting records, and
from first to last the art of paper-making and bookbinding was conducted
with the object of producing an enduring article.

With the advent of machinery this ideal began to change, not because of
the greater output that became possible, but because progress demanded that
output. The slow, old-fashioned methods and materials were too expensive,
and other and quicker methods, and cheaper and more abundant materials,
became necessary if paper-making was to keep up with the advance of science
and the general progress of the world. This inevitably meant poorer and less
durable products, but it was recognized that these were quite good enough for
what was required of them.

Now this idea has developed so far that no one troubles about paper further
than that it will fulfil the purpose of the moment, and that it can be obtained
at the lowest possible price consistent with that condition. The paper-maker
is now compelled to supply demands on that basis, and when we have com¬
plaints from printers and stationers about the paper they receive, we feel
tempted to reply that they are getting no more and no less than they are
paying for.

Any of our ‘fine’ mills can supply a paper that will last, under ordinary
conditions, for ever, but very few printers, for instance, would be w illin g to
pay a price that would enable the paper-maker to make that paper. The object
of the paper-maker is to supply the best he can for the price, and this best too
often falls short of the quality he would prefer to give.

There are, however, papers that are admittedly made for the moment.
They serve the purpose and are discarded. The principal paper of this class
is newsprint. All papers containing mechanical wood are short-lived. The
resin and natural impurities in the wood very quickly bring about the destruc¬
tion of the paper, which turns brownish-yellow in colour, grows brittle and
ultimately is reduced to dust. Newsprint does not work well on the printing
machine when newly made. It is ah the better for st an ding a few weeks to
absorb the normal humidity of the atmosphere, and to allow any electric charges
to pass away.

But within ten years after being used, newsprint generally is so much
deteriorated that it can scarcely be handled. It may be preserved by pasting

DURABILITY AND STORAGE

339

a thi n tissue of good quality over it, but it is doubtful how long a newspaper
will be readable even with this plan.

On the other hand, news-sheets printed ioo years ago on hand-made rag
printing paper are as good as ever. One of the greatest factors in the deteriora¬
tion of paper is the use of resin size. Resin, when exposed to light and air,
becomes friable and is reduced to dust, and all papers sized with resin lose their
ink resistance, colour, strength and finish. When resin size is supplemented
by a coating of gelatine the life of the paper is lengthened, by how long we
cannot tell yet; but it is certain it will not in ioo years be in the same perfect
preservation as when it was made, as the hand-made papers of a century ago
are at the present day.

By substituting silicate of soda for resin we get a much more durable and
light-resisting paper, such as may be used for printing with printer’s ink.

As regards dyes, many cannot stand light at all without fading out and
taking all the good of the paper with them. The aniline or coal-tar products
are mosdy of this class. Smalts blue is, of course, a permanent colour, so also
in a great measure is good ultramarine blue and most of the mineral colours,
except those which owe their shades to oxides of iron, and which tend to go
darker in colour and destroy the cellulose.

Chemical residues of alkalis, bleach, acids and possible combinations of
chemical traces in mill water many cause or hasten deterioration of paper. A
very curious effect is produced by age in the particles of copper or brass that
are found in a great many good papers that have been beaten with bronze roll
bars, or that have been made from rags in which pieces of copper have been
retained. In a few years from each of these particles irregular lines spread
outwards through the fibres, sometimes covering a space J inch in diameter.
These are called ‘dendritic growths’. The products of the oxidation of the
metal travel along the fibres and form fern-like designs.

While the paper-maker knows that many of his products are more or less
perishable, he is also aware that some or all can be gready improved by being
kept in stock for varying lengths of time, under proper conditions, before being
sent out from the mill. All machine-made papers are produced under a certain
amount of strain, and the fibres ought to get time to relax.

Most printing papers are improved by being kept in a cool, dimly-lighted
stock room for a few weeks. Papers intended for litho work especially will
benefit by absorbing atmospheric moisture and getting rid of their electric
charge.

On gaining a normal air-dry condition finish goes off more or less. A
plate-glazed finish is most permanent; next in order is a super-calender finish.
Any glaze or finish obtained by hot rolls is most liable to - go back. But a

MODERN PAPER-MAKING

340

wise paper-maker provides for this by having the finish a litde higher than the
sample in the first place. Complaints are often made of deficient bulk and too
high finish when all that is required is a reasonable time for paper to mature.
For this reason it is bad policy for a customer to send an order and ask for
immediate delivery, unless he knows the mill stocks the paper he wants, and
also for the paper-maker to delay making an order until he has to send it out
as soon as it is made.

Poor quality or badly-made gelatine size is also a common cause of the
deterioration of paper. Given the least extra humidity in the stock room,
poor size begins to give off an offensive odour, and the paper loses strength,
colour, finish and ink resistance. Generally a good quality of gelatine size,
properly made, will withstand the ordinary variations of humidity in the stock
room, but any definite dampness continued for a time produces bacteria which
destroy the gelatine.

Paper should not be stocked on a ground floor or under ground level,
where the atmosphere is likely to be humid. A well-ventilated stock room on
the second floor is most desirable, with a temperature of 6o° F. and a diffused
light from ground-glass windows, preferably greenish-tinted.

All ventilators should be covered with wire cloth, to prevent dust or sooty
particles from gaining admission, and no machinery or shafting should be
installed in a paper store.

Sweeping can be safely undertaken by putting down damp sawdust, to
which the floor dust will adhere, or by using a vacuum cleaner. Spraying the
floor with water before sweeping makes the air too moist, besides the risk of
splashes or drops of water getting on the stacks of paper. Even under the
strictest conditions there will be some dust, therefore a sheet of wrapping
paper must be used to top each pile of paper or packages, and sheets of
wrapping put on the floor for the stacks to stand on, the sides being tucked
in all round to a height of 6 or 8 inches above the floor level. Wide avenues
should be left between each double row of stacks, so that every stack can
be reached without disturbing another. All those who have to handle the
stock must have clean aprons or overalls and must keep their hands perfectly
clean. It is surprising how many sheets a dirty thumb will spoil.

The stacks ought to be built up carefully so that there are no protruding
sheets, which will certainly be broken at the edges when the paper is again
lifted. The height of the stacks will depend on the size of the sheets. A small
sheet will not stack safely to any great height, especially if it has a low finish,
as a slight push may send it over. A safe rule is that no stack must be higher
than a man of average height can build without the use of steps.

If the paper is in wrappers there is, of course, less danger of it being spoiled

DURABILITY AND STORAGE

34 i

in the stack. It is not advisable to use gas lighting in the stock rooms; apart
from the risk of fire, the products of the combustion of gas have a deleterious
efect on paper.

BIBLIOGRAPHY

1. Proc. Tech. Sect. P.M.A., 1937, XVIII, Part ia: Report of Paper-Testing Committee.

2. Potts: Proc. Tech. Sect. P.M.A., 1931, 12 ,91.

3. Goldberg: Joum. Soc. Chem. Ind., 1937, 56 ,249 T.

4. Hammonds: Paper Trade Journal, 1936, 103 ,32.

5. Bekk: Proc. Tech. Sect. P.M.A., 1935, 16 ,1.

6. Fairbrother: World’s Paper Trade Review, 1937, 58 , T 538.

7. Meese: Papier Fabr., 1937, 35 ,177.

8. Strachan: Paper-Maker, 1937, 93 , T 549.

9. Schulze: Papier Fabr., 1937, 35 ,219.

CHAPTER XXI

WATER SUPPLY-RECOVERY AND RE-USE OF WATER

Water Supply—A most important point to be considered when choosing a
site for a paper-mill is undoubtedly that of water supply. Water is as im¬
portant as transport facilities and the proximity of markets; unfortunately
this has not always been taken into consideration when choosing a site, and
some mills to-day are very hard put to it to find sufficient suitable water for
their requirements.

The ideal water for all requirements of a modem mill is not commonly
met with, and the mill is fortunate which can boast an adequate supply of
water suitable for steam-raising and paper-making purposes.

In the first place it must be borne in mind that a very large quantity of water
is required to produce a ton of paper, no matter of what quality. For the
production of a rag paper 80,000 to 140,000 gallons of water are required per
ton of paper, and a very large proportion of this is irrecoverable and runs to
waste. For newsprint the amount varies from about 2000 gallons upwards,
per ton.

The second point to be considered is the quality of the water, and
in this connection the quality of the papers to be made will be the deter¬
mining factor. If the water is very soft, such as water from peaty moors,
it will suit the steam boilers, as it will eliminate both the necessity for
providing a water-softening plant and all trouble with scale in the boilers
and economisers.

This water will, however, foul with slime and possibly with iron deposits
many of the tanks and water-pipes in the mill, and, unless it is carefully filtered,
with suspended matter.

Such water has many advantages, but it cannot be made to produce papers
of such a pure and bright colour as other 'harder’ waters, and it is usually
necessary to pass it through a series of filters to remove the suspended matter
and to improve the colour.

Where surface water has to be used, unless the qualities of paper to be
made are very low or highly coloured it will usually be found most satisfactory
to filter it, as otherwise the colour of the paper will be at the mercy of the

weather, and floods and other discolorations will have disastrous results at certain
periods of the year.

342

WATER SUPPLY

343

Some of the filters at present available give excellent results, require little
or no attention and are self-cleaning, this latter operation talcing only a few
minutes each day: They remove all suspended matter and make a wonderful
improvement in the quality and brightness of the colour.

Brown peat water, often in flood time the colour of beer, comes through
the filter quite clear and bright. The same applies to ordinary river water,
which may often be contaminated with road water, surface water from streams,
and in the summer months with rotting water-weeds.

[Paterson Engineering Co. Ltd.

Fig. 148.—Water Clarification and Filtration Plant at a Paper-mill.

• Capacity 15 Million Gallons per Day

A suitable type of filter for general paper-mill requirements is that known
as the Bell filter (Fig. 149), which is working satisfactorily in many paper-mills
at present. The Paterson Engineering Company also make a similar filter as
shown in Fig. 150.

Hard waters containing calcium carbonate, calcium sulphate and mag¬
nesium salts, while very suitable for making paper, especially those qualities
which have to be bright and clear both on the surface and especially in the
look-through, have the great drawback of depositing scale in the pipes, econo¬
misers and steam boilers. If these waters are very hard, it is necessary to treat
chemically that which is to be used for steam raising.

344

MODERN PAPER-MAKING

They may be used in their natural state for paper-making, but service
pipes, etc., will frequently require to be scaled in order to keep them clean

Fig. 149.—Bell Pressure Filter
Internal view of the rotating arms and nozzles

[Bell Bros..Manchester

and to prevent pieces of scale coming away into the stuff at the machine and
thus spoiling the paper.

WATER SUPPLY

345

This trouble is most likely to occur if the pipes, etc., have been left empty
for any length of time and have become dry.

When hard water has to be used for steam raising it must first be softened
in order to prevent scale in the boilers and economiser pipes, and one of the
plants in general use is that made by Paterson. The machine consists of a
tower (Fig. 151), at the top of which is a mixing tank for chemicals and also the

[Paterson Engineering Co. Ltd.
Fig. 150.—Section of Pressure Filter, showing Under-Draining
, System

intake for untreated water. The water flows down a central tube fixed in the
middle of the tower, and is mixed with the softening chemicals as it passes
down. When it reaches the bottom of the tube it passes up the tower again,
depositing any heavy, insoluble matter at the bottom. On reaching the top
it passes through a filter, where any suspended matter is removed, and is now
softened and cleaned ready to pass to the boiler-feed tank, or any other place
where it may be required. This system is effective and simple in operation
and costs very little to run.

346

MODERN PAPER-MAKING

Surface water from springs and small streams or ‘bums’ may often be
satisfactorily freed from suspended matter by passing it through a series of
tanks filled with clean coke or sand. The water is made to flow upwards
through the cone in the first tank and down through the coke in the second
tank, and so on until it is sufficiently cleaned. The coke must, of course, be
renewed periodically.

Another method is to fill the tanks first with drain-pipes and then with a

OSILAMETER REaGEnT
SUPPLY GEAR BT P "
TYPE

hard Water inlet

ISLUOQE OUTLET

[Paterson Engineering Co. Ltd.

Fig. i5i.—Typical Vertical Water Softener, Lime-Soda Type

layer of coarse stones, then smaller stones, followed by a layer of gravel, and
finally a layer of clean sand on top. In this way the water, passing through
the various layers, deposits the suspended vegetable matter and dime, and
finally appears at the top in a clean and clear state. The sand, etc., has to be
removed frequently and washed in a washing machine, and is then put back
in place ready to be used again.

These methods are both, of course, entirely mechanical, and no change
takes place in the actual composition of the water. When a Bell filter is* used
the action may be partly chemical as well, as the water may come in contact
with alum and so be softened and actually freed from colour by chemical action.

WATER SUPPLY

347

In choosing a site for a mill too much importance cannot be attached to
the question of water supply, and exhaustive tests must be carried out to ascer¬
tain the amount and quality of the supply, having due regard to the immediate
and possible future requirements.

In almost every mill vast quantities of water can, and should, be recovered
for further use. This question is now receiving greater attention than formerly,
and it is a most important one.

[Paterson Engineering Co. Ltd.

Fig. 152.—Chemical Dry Feeder, for the Accurate Addition of Chemicals *
for Water Treatment

Broadly speaking, the water has to be recovered from the machine and
returned to the beaters, or to the stuff box at the machine, but there are other
places where a great deal can be recovered.

To take first a rag mill, which uses more water per ton of paper than other
mills. Water is first used in the rag boilers; this is irrecoverable, owing to
the presence of grease, soluble soaps, etc., and it must be passed to settling
tanks if no convenient sewer is available. It should not in any case be returned
to the river.

MODERN PAPER-MAKING

348

The rag washer uses a large amount of water, and this is not recovered, as
it contains traces of the soaps formed in the boiler and also a quantity of rag
fluff or fibres, but not sufficient to pollute a river. The rag breakers, where
most of the washing is done, also use a very large quantity of water, and this
is also not recovered, although if a wrapper machine is run at the mill some
of it can certainly be used with advantage for furnishing the beaters.

There is a very large amount of rag fibre lost here, due to the finer fibres
passing away through the meshes of the washing drums and the washer screens,
and also through the button and sand catchers, where these are fitted. The
loss sustained during this operation is serious and deserves more careful attention
than it generally receives.

It might possibly pay to recover this fibre in a save-all, and some of the
water used towards the end of the washing is quite clean enough to use again
if water is scarce. This would necessitate the use of large tanks and a pump
to return the water to the washer.

Immediately following the washing operation in the breaker comes the
bleaching, and this uses more water; where the bleached stock is run into
drainers or steeps the liquor from these latter should always be recovered,
when rags are being bleached, and run into tanks, whence it may be pumped
back to the potchers to start the next bleaching operation.

It is sometimes possible to use the spent liquor from three potchers to com¬
plete the bleaching of die rags in a fourdi potcher without the addition of any
fresh bleaching liquor, and this represents a great saving. This can only be
done, however, when more than the necessary amount of bleach is being used
in the first instance— i.e., when hurrying stock through the mill.

The beaters are usually furnished with new unused water, owing to the
fact that every care has to be taken to eliminate dirt, and to keep the shade of
the paper bright and constant. This does not, of course, apply to low-grade
papers, newsprint and printings, and even in the case of fine papers sufficient
water should be available from the machine back-water system to furnish the
beaters.

At the machine all spray water from the strainers, water from die save-
alls beneath the wire and overflow water from the vacuum boxes should be
collected and run to an auxiliary strainer or ‘back knotter’ and strained free
from lumps, knots of fibres, and rubber, and then pumped back to the stuff
box for diluting the thick stuff from the stuff cock. The careful conservation
of all this water represents an enormous saving in chemicals, such as engine
size, alum, dyes, loading and small fibres. It also reduces the effluent, which
must be disposed of ultimately. It also assists gready in the reduction of froth
and the prevention of scale in the water service system when hard waters are

WATER SUPPLY

349

used, and this operation has been proved, when carefully attended to, to double
the length of life of the machine wire. In this case, formerly only about half
the water required at the stuff box was recovered water, the other half being
‘fresh’ and very hard. It was found that after a week the machine wire was
so filled up with a white limy deposit that it was necessary to remove it with
a strong solution of vitriol. This, of course, ruined the wire in about 4 to 6
weeks, or even less.

When, however, use was made of all the water which could be recovered
and no fresh water was added, no vitriol was required to clean the wires, and
they lasted from 8 to 12 weeks without any special cleaning other than an
occasional blow with the force jet.

It had also been found expedient to have a spray-pipe on all the wire rolls,
whereas, after the back water only was used, no sprays were used except on
the wash and breast rolls.

In mills making printings and newsprint there is no recoverable water
except at the machines, and every drop of this should be carefully caught and
returned to the beaters, stuff box and machine service system, either direct or
after passing through some sort of save-all. This water is generally termed
‘white water’, and it comes from the wire and suction boxes at the machine.
It is collected in the pit below the machine, and contains large quantities of
clay and fibre from the deckle edges which are cut off, and also from the water
which passes through the meshes of the wire, carrying clay and fibres with it.

The water is kept agitated by means of paddles in the pit, and is pumped
to huge tanks above the breakers or beaters, whence it is run to the latter when
furnishing.

There should be no dirty effluent at all from a news or printing mill, except
floor washings, containing oil from bearings, etc., and the only fiesh water
which should usually be necessary will be for the sprays at the slices and guard
board, for the spray damper at the reel end, and for the edge cutters.

Other mills making different grades of paper should be able to recover
varying amounts of water, according to the conditions under which they work,
and if it is found impossible to use all the water it should in any case be filtered
to remove the valuable fibres and clay, which can be used again either in the
same paper or in lower grades.

35°

MODERN PAPER-MAKING

The Recovery and Re-use of Waste Waters, Fibrous Material

and Loading

In almost all mills a large quantity of fibre and clay may be recovered
from the back waters of the machines. Generally speaking, the lower the
grade of paper being made the greater is the amount of stuff which can be
recovered.

Until quite recently it was common practice for the waste waters con¬
taining size, colour, loading and fibres to be run to the drain, river or other
convenient place, and thus much valuable material was lost and much pollution
of rivers caused.

Two factors were chiefly responsible for the curtailment of these losses, one
being the increased competition in the trade and consequent need for economical
production, the second the tightening up of bye-laws concerning pollution by
river conservators and fishery boards.

The yield of material in a rag mill may be taken to be from about 60 to
80 per cent, so that from ioo tons of rags anything from 20 to 40 tons are
lost between the rag loft and the machine reel. A good deal of this loss is
represented by unsuitable material thrown out, and also by the removal of
dust, loadings, starch, grease and ligneous matter during the boiling and bleach¬
ing operations.

Apart from this, however, there is a serious loss of small fibres during the
washing and draining of the stuff, and again at the machine, where a great deal
of small fibrous material is washed away through the meshes of the machine
wire. There is also a loss at the auxiliary strainer, due to hanks and knots of
fibres which get caught here, which are so mixed with dirt, rubber, etc., as
to be unfit for further use.

Stuff is also lost which runs down the wire when starting up, or if a break
occurs there, and other small losses occur when starting and stopping by stuff
going down the pit between the wet felt and second press, and between the
second press and cylinder. These latter losses are very small, and may be
prevented by the provision of clean wooden boxes to catch the stuff, provided
that the stuff is carefully removed at frequent intervals and returned to the
beaters in a clean state.

Where the mill makes nothing but fine qualities it will generally be found
impossible to use again any of the fibres which may be recovered from the
washing waters and the auxiliary strainer. The usual practice in dealing with
such waste is to run it to tanks where the fibrous material may setde down, and
the clear water is then run off to the river or drain. The tanks are periodically
cleaned out and the stuff is thrown away as useless refuse.

RE-USE OF WATER

35i

If, however, the mill makes its own wrappers from time to time, or has a
machine engaged in the manufacture of wrapping papers, it will pay to recover
all this fibre in order to assist in making up the furnish of the wrapping papers.
This is not only economical, but it also enables a really good wrapper to be
made, on account of the rag fibres contained in the refuse.

The method employed to save this material is simple, and consists of running
the waste washing water, overflow or cleanings from auxiliary strainers, waste
from the wire pit and press pit into large tanks built up of perforated tiles.
Here the water drains away, leaving a large proportion of the fibres lying in
the bottom of the tank and round the sides. The tanks are periodically cleaned
out and the stuff is taken up to the beaters to be furnished for wrappers. The
tanks should be of a sufficiently large capacity to deal with all the water from
the rag-washing engines, which contains only a small amount of fibre, and they
must also be capable of dealing with the stuff from the machine wire pit when
changing or washing up.

If this work is being properly and carefully carried out by the machineman
the amount of effluent should not be excessive, but there will always be some
waste from the bottom of the chest, the sand traps and strainers, and a small
amount from the wire pit.

In mills making lower grades of paper the methods employed vary accord¬
ing to the general lay-out of the mill and the grades being manufactured, the
amount of waste which has to be dealt with and the capacity of the mill to
re-use this waste in lower-grade papers.

It may be taken as a general rule that most of the recovered stuff will have
to be used in a paper of a lower grade, quality or colour from that which pro¬
duced the waste water.

The most satisfactory method is as follows:

All water from the machine wire pit, press roll pits, wire save-alls and
suction boxes should be collected in suitable tanks at the back side of the machine,
whence it can be pumped back to any or all of the following places:

1. The machine back-water tank for supplying the mixing box.

2. The beater supply tanks.

3. The machine chests.

4. The sprays at the machine.

When the machine starts up, assuming the back-water service system to
be empty, it will be necessary to use fresh water to dilute the stuff coming
into the mixing box from die stuff tap, but as soon as the machine has
started and the back water has had time to get round, the fresh water may

352

MODERN PAPER-MAKING

be shut off and no more will be required. There will thus be a supply of water,
containing a little fibre, loading, size, alum and dye, in constant circulation
at the machine. The surplus from the save-alls and wire pit over and above
the requirements of the machine is then pumped up to large tanks situated
above the beaters. From these tanks the beaterman draws his supply for
furnishing and emptying the beaters, and for diluting stuff going through the
refiners.

Re-use of Back Water .—When the web is being run down the wire for any
length of time, such as that occupied in washing and turning a felt on a news
machine, the stuff which collects in the pit is stirred up with water and
pumped back direct to the machine chests. This obviates the necessity for
shutting off the stuff and possibly upsetting the machine when it is running
well.

There is a disadvantage in this method—namely, the dilution of the stock
in the chest—and the machineman must be careful to see that when he starts
up again his weight is not seriously affected.

The sprays at the strainers and on the wire rolls may be supplied with back
water, withdrawn from the web at the suction boxes, and thus there is an
economy in the use of fresh water and a consequent diminution in the quantity
of back water to be dealt with subsequently.

This water is drawn out at the boxes through the meshes of the wire and
has consequently been well strained. It is then collected in a sump and forced
by another pump at a high pressure to the strainer and other sprays about the
machine.

When this method of supplying the sprays can be adopted the use of fresh
water is cut down to a minimum, and it will then be necessary only to have a
fresh-water spray on the breast roll, couch roll and possibly at the breast box
to keep down froth.

Adka Save-all (Fig. 153).—This save-all employs the principle of flotation,
as opposed to the older forms using the principle of sedimentation. The flota¬
tion is brought about by forcing the back water through a nozzle, designed
on the lines of an injector, through which the air is drawn and intimately mixed
with the back water. It is then passed into a chamber, and under vacuum the
fibres, surrounded by minute bubbles of air, and flocculated by a suitable floccu¬
lating medium, rise to the top of the liquid, where they are drawn off by a
scoop, and returned to the paper machine. The clarified water runs con¬
tinuously from the bottom and is used whenever desired. A picture of the
Adka is shown in Fig. 153.

The back water from the machine is passed through the main inlet (1) and
travels down to the aerator nozzle (2), where air is drawn in through the air-

BACKWATER RECOVERY

353

intake pipe and intimately mixed with, the back water in the nozzle. It
then passes to a wooden box (3); much froth is made in this box owing to the
excess air escaping, and the air-intake pipe is led into this froth from a

The cycle of operations is as follows:

The back water is pumped by pipe 1 through injector 2 to the tank 3 (the injector aerates the back water and by this
means carried up any loading material contained in it).

From tank 3 the back water is drawn up pipe 4 to the main tank 5. The fibres being aerated, plus the vacuum in tank 5,
causes the flow up pipe 4.

The revolving pipe 6, with its sucker 7, is the suction pipe coupled to the vacuum pump 8.

The thin layer of fibres floating upon the surface of the b,ack water in tank 5 is sucked off by the sucker 7. After being
skimmed, the clarified water falls to discharge tank 9 by pipe 10.

The air and recovered stock are drawn towards pipe 11, the air ascending up the pipe 12 to the vacuum pump 8. The
recovered stock descends in barometric leg 11 to the centrifugal pump 13 and is pumped to the stuff chests or preferably
the mixing box. Both pumps are driven by motor 14. The compensating pipe 15 allows for a constant discharge from the
centrifugal pump 13.

Pipe 16 is to fill the tank when starting up; 17 reverses the flow of liquid for washing-out purposes.

Sight holes in cover with electric lamps allow for inspection of inside of tanS 5.

MODERN PAPER-MAKING

354

point above the aerator nozzle and keeps it from overflowing. The back
water than flows upwards and back over another wooden partition to
the base of the surge-pipe (4), up which it is drawn by the vacuum
in the body of the Adka. This vacuum is maintained by the excess air
being drawn off through the same rotating scoop (7), which deals with the
thick stuff floating to the top. By reason of the vacuum in the chamber (5)
the height of the floating stuff in the body is always maintained at the
same level, since if the back water rises above the level of the inlet of the
rotating scoop, no more air could be sucked from the body, and in con¬
sequence the back water could not rise any higher; and likewise if the back
water should drop below the level of the scoop, the vacuum would be auto¬
matically increased, which would once more draw it up to the right height.
In practice the level of the back water in the body seldom varies more than
& inch, which is usually insufficient to cause any serious fluctuation. The
thick fibre and clay on the top of the back water in the body is drawn upwards
to a separating chamber (11), where the stuff falls to the bottom and is dealt
with by a centrifugal stuff pump (13), and the air rises to the top, where it
is drawn off over a barometric column (12) by a drum vacuum pump which
is always kept submerged by a priming tank set alongside (8). The centrifugal
stuff pump should be of sufficient capacity to deal with the stuff drawn off,
and be capable of pumping it to wherever desired, in most cases to the sand
traps of the paper machine. The clarified water freed from die clay and fibre
travels down a series of pipes (10) set around the base of the body, all flowing
into one common outlet pipe into a box (9), from whence it is discharged
to the drain or for re-use. The ends of the clarified water-pipe and the surge-
pipe should always be completely submerged, otherwise the vacuum in the

It will be readily understood that the time taken for die whole cycle of
operations is very much shorter than that in a sedimentation type of save-all,
as the back water is dealt with almost immediately, and it is only a matter of
a few minutes to effect changes of colour. In practice, with short delivery
pipes to the paper machine, 5 minutes is sufficient interval when changing to
get the new colour to the paper machine.

The clarified water is practically free from fibres and clay, and may be used
for all ordinary purposes in the mill.

CHAPTER XXII

SODA RECOVERY

One of the most expensive items in a paper mill using esparto, straw, or
rags for its raw material is the caustic soda required for boiling. In small
mills, using rags or rags and wood, the spent liquor from the boilers, both in
quality and quantity, is not worth the expense of installing a recovery plant.
The disposal of the liquor is a continual source of trouble with the River
Pollution Authorities, yet it must be disposed of somehow, often at great
expense.

When a mill is boiling esparto and using 3 to 4 cwt. of caustic soda per
ton of grass, it becomes not so much a question of disposal as of recovery.

The principle of soda recovery is in itself very simple. The liquor from
the boilers, containing the soda combined with the non-cellulose constitu¬
ents. of the raw material, is evaporated to a thick liquor and incinerated.
The soda is thus converted into sodium carbonate, which is dissolved out from
the incinerated mass and brought back to the caustic condition by the action
of lime.

When the grass has been cooked, the steam is shut off and the vomiting
action ceases as the pressure falls. The drain cock to the spent liquor reservoir
is then opened and the liquor is discharged from the digester. A much better
result is obtained by allowing slight pressure in the digester to express the
liquid from the grass.

The cock is then shut and the boiler is filled, to above the level of the grass,
with hot water obtained from the condensation of steam during the boil.
Some steam is turned on to circulate the water through the pulpy mass.
This wash is also run to the tank. A second wash may be carried out in the
same way, but it is necessary to be careful here so that the liquor in the tank
is not too much diluted for economical recovery of soda. After this, wash¬
ing water may be run to the drain until the effluent is reasonably clear. A
loss of soda occurs here of 2 to 5 per cent according to the efficiency of the
first and second washes. The second wash may be pumped to a separate
tank and used for the first wash of the next boil. Although this may reduce
the work of the evaporators to some extent it is bad practice, chiefly because
the colour of the grass is reduced, and any saving effected is nullified by the
extra pumping and tanks required.

‘355

356

MODERN PAPER-MAKING

The liquor may be run through a drum washer on its way to the tank to
keep back fibre and sludge, but here again a loss takes place and the liquor
is more difficult to bum, requiring to be evaporated to a greater density.
There is of course a risk of economiser tubes or other pipes becoming clogged
up, but the regular cleaning and attention, which this department should
receive if it is to be efficient, will reduce this to a minimum.

[George Scott and Sons

Fig. 154.—Scott Quadruple Effect Evaporator for Caustic Soda Liquor

Evaporators are usually three in number, of which one is fed with steam
from the main range. The plant is described as 'Triple Effect Vacuum Tube
Evaporators. Some plants have four evaporators and are described as Quad¬
ruple Effect (Fig. 154).

Advantage is taken of the lower boiling point induced by lessened atmos-
phenc pressure, a vacuum being maintained by a barometric column and
pump, or jet condenser. The steam created by the boiling liquor in one effect
is used to bring it to a boil in the next, which is under less pressure. In some
installations the liquor flows from the highest to the lowest temperature, in
others the opposite way.

SODA RECOVERY

357

Each effect has three chambers, the bottom one being very shallow, the top
one being much larger. The centre chamber is composed of a number of
upright tubes connecting the top and the bottom, through which the liquor
is agitated by means of the vacuum. The steam to assist the evaporation of
this liquid is passed through the centre chamber, but on the outside of the
tubes. The last effect or concentrator is constructed in the same manner as

[George Scott and Sons

Fig. 155.—Two Scott Rotary Furnaces with Patent Soda Grates

Nos. 1 and 2, but the steam for this concentrator is new steam, procured
entirely from the main steam range. This ensures that the thickened liquor
is passing to the furnace at the highest temperature, the drop in temperature
being from the third to the first effect in this arrangement.

Where the drop in temperature is from the first to the third effect, the
thickened liquor requires to be run to a steam-heated storage tank to increase
its temperature, thereby making it more fluid and easy to bum.

The liquor has then been concentrated from about 4 0 Tw. to 6o° Tw. (200°
to 230° F.) by evaporation, and passes onwards to the rotary furnace (Fig. 155).
This consists of a revolving firebrick-lined steel shell, whose internal diameter

MODERN PAPER-MAKING

358

increases towards the discharge end. It revolves about once per minute.
Ignition of the liquor is caused in the first place by the flame from an auxiliary
furnace with coal, oil, or wood at the start of a run, and with careful control
the liquor will then remain alight throughout the run. In one type of furnace
the liquor is sprayed in similarly to an oil-fired boiler.

Combustion is sustained by the burning of the organic matter brought
forward with the liquor from the digesters.

[George Scott and Sons

Fig. 156.—Causticisers, and in rear Rotary Vacuum
Filter

There are several methods of subsequent treatment of the black ash. One
method is to complete the combustion of all remaining carbon on a travelling
chain grate over forced draught. Another consists in removing the ash from
the furnace while combustion is still incomplete and spreading this ash over
a perforated floor under which an air draught is induced. Complete com¬
bustion requires about two weeks under these conditions. This method has
the disadvantage of requiring a long time and a good deal of floor area. The
calcined ash, or black ash’, is then soaked with bo ilin g water, which absorbs

SODA RECOVERY

359

all the sodium carbonate, and this is drained to a pump through perforated
tiles in the bottom of the soaking tank. This liquor is then pumped to a
causticising pan (Fig. 156) with a half-round bottom and a mechanical

Fig. 157.—Flow Diagram of Caustic Soda Recovery Process

MODERN PAPER-MAKING

360

agitator. A quantity of pure ‘make-up’ sodium carbonate is then added, with
the necessary amount of lime, to the causticiser, where it is dissolved by boiling
and agitation. The aim of the whole operation is to retain the maximum
amount of sodium carbonate, any losses being replaced at the causticiser.

The required amount of lime is then added to the causticiser, the action
being chemically designated so:

Na 2 C 0 3 +CaO +H* 0 =CaCO»+2NaOH

Up to 45 per cent of lime is required, and the whole is subsequendy boiled
for from 1 to 2 hours with direct steam and continuous agitation. Agitation
then ceases and solids, principally chalk and carbon, are allowed to settle.
‘Strong’ liquor may then be drawn from the top of the causticiser. It is then
recharged with water and agitated for a further hour. The solids are then
again allowed to settle as before and a weaker liquor is drawn off. These
two batches are then mixed and give a batch of boiling liquor at somewhere
about 14 0 Tw. The causticiser is again filled with water and agitated as before,
and when all solids have settled out the resulting liquor is drawn off and serves
as a ‘water’ for the next ‘weak’ liquor production.

The losses, which are inevitable, result from carrying off sodium carbonate
in the digested grass, in the sludge from the drum washer, if used, in the vapour
from the evaporating plant, by particle entrainment in the rotary furnace
flue gases, and incomplete recovery from the black ash, and sludge from the
causticiser pans.

The sludge left in the causticiser pan is a very difficult problem. It may
be drawn off and setded in ponds, the liquor from the surface being run away
and the sludge being dug out and deposited in some waste ground. It can be
readily understood that there may be many difficulties in this proceeding, as
it is not easy to find sufficient waste ground to dispose of the sludge from a
large mill.

It is possible, however, to dry this sludge and recondition it so that it may
be used as lime for agricultural purposes.

The recovery of from 70 to 80 per cent is possible economically, and
higher recoveries than this have been claimed. Although it is theoretically
possible to recover nearly 100 per cent of the original soda used, the expense
would be greater than the value of the recovered soda. Where there is no
easy method of disposing of sludge and extra washings of the grass owing to
the proximity of a preserved river, recovery has to be of the utmost possible
quantity in order to satisfy River Authorities. In this case extra expense is
of course inevitable and unavoidable.

APPENDIX OF TABLES

MOISTURE IN PAPER ON MACHINES

The following tables show the percentage of moisture contained in the
web from the breast box to the finishing house, and also the proportion of
water to dry fibre.

Fourdrinier.

Class oj Paper

White News

Common News

Substance in D.C. soo’s .

25 lb.

21 J lb.

Speed .

580 ft.

590 ft.

Parts water

per part

fibre

Breast box.

98.92

91.6

99.2

124.0

Couch .

77.6

346

78.1

3.57

First press .

73-1

2.59

75-5

3.08

Second press.

69.3

2.25

71.6

2.52

Third press.

68.4

2.16

71.6

2.52

Middle cylinder .

41.1

0.69

49.1

0.96

Machine calenders.

6.2

0.06

7.0

0.08

After damping .

12.2

0.14

0.10

After super-calender .

7.2

0.08

8.8

0.10

Length of machine wire, 70 feet. Six suction boxes. First press, maple; second press, granite; third press, brass. All
on rubber. Thirty 5 feet 6 inch drying cylinders. Cooling roll at reeling drum. Spray damper before reeling drum.

Fourdrinier

Class of Paper

Mechanical

Printing

Antique Wove

Printing

Substance in D.C. 500*5 .

31J lb.

681 b.

Speed .

330 ft.

140 ft.

Parts water

per part

fibre

Breast box.

99.0

444

Couch .

85.1

5.71

80.0

4.00

First press .

69.6

2.29

63-4

1.73

Second press.

64.9

1.85

6I.4

1-59

Intermediate rolls.

—

17-3

0,21

Machine calenders.

6.2

0.07

4.8

0.05

After damping .

10.6

0.12

—

After super-calender .

8.2

0.09

—

After cutting and finishing

—

5-2

0.05

This machine had a wire 50 feet long, and iron first and second top press rolls, with rubber bottom rolls.. There were
twenty-two 5-feet drying cylinders.

362

MODERN PAPER-MAKING

Fourdrinier

Class of Paper

Tissue

Substance in D.C. 50o’s

9.17 lb.

Speed . .

350 ft.

Parts water

per part

fibre .

Breast box.

99.52

207.0

Couch .

84.3

5-37

First press .

70.2

2.35

Second press

68.5

2.17

Middle cylinder.

47*3

0.90

Reel .

0.05

M.G. Machine

Class of Paper

Pure Sulphide

‘ Manilla ’ Envelope

Paper

Substance in D.C. 500’s .

1 6 lb.

32 lb.

Speed.

150 ft.

140 ft.

Parts water

per part

fibre

Breast box.

994

165.7

98.8

82.3

Couch .

85.0

5.67

81.4

4.38

First press.

68.3

2.16

69.9

2.32

Before M.G. cylinder .

65.6

I.9I

68.0

2.13

At reel .

5-6

0.06

5.6

0.06

M.G. Machine

Class of Paper

Pressing or Cover Paper

Sulphite Litho

Substance in D.C. 500’s .

47 * lb.

32 i lb.

Speed .

91 ft.

100 ft.

Parts water

per part

fibre

Breast box.

98.6

70.4

99-0

Couch .

78.5

3.65

73.9

2.83

First press .

67.1

2.04

58.3

1.40

Before M.G. cylinder .

60.9

1.56

At reel .

0.04

0.05

APPENDIX 363

MOISTURE REMOVED BY THE COUCH ROLLS

It is sometimes asserted that the couch rolls do not remove any appreciable
amount of water from the web. This is not so. The result of several tests
showed that about 10 per cent of water is removed, or the proportion of water
to fibre is almost halved.

Moisture in web before couch roll 86.85 per cent, or 6.60 parts water per
part fibre.

Moisture in web after couch roll 78.64 per cent, or 3.68 parts water per
part fibre.

The moisture content is estimated on the wet pulp weight.

The paper was pure sulphite and the substance 24! lb. demy.

Colour Reactions of Fibres by Common Stains

Fibre

Iodine and

Zinc Chloride

Iodine and
Sulphuric

Acid

Aniline

Sulphate

Phloro¬

glucinol

Cotton .

Violet

Blue

Flax .

Violet

Blue

—

Hemp *.

Violet

Blue

Pale yellow

Violet red

Jute.

Brown yellow

Green blue

Golden yellow

Deep red

Ramie .

Dull violet

Dull blue

—

Manilla hemp .

Yellow to violet

—

Yellow

Red

New Zealand flax .

Golden yellow

Green blue

-Yellowish

Pale red

Chemical wood.

Blue violet

Blue to grey

Pale yellow

Pale red

Mechanical wood.

Yellow

Dark yellow

Deep red

Iodine and Zinc Chloride (Herzbero Stain). Dissolve 20 grms. zinc chloride in
10 ml. water and add to a solution of 2.1 grms. potassium iodide and 0.1 grm.
iodine in 5 ml. water. Allow to stand for 24 hours and decant the clear
solution, and finally add a crystal of iodine to the clear solution. Place a drop
of the solution on the disintegrated and teased fibres and mop up the excess
stain to avoid too deep a colouration.

Iodine and Sulphuric Acid. Dissolve 2.85 grms. iodine and 5.0 grms. potassium
iodide in 100 ml. water. Add 5 ml. glycerine.

Spot the fibre mass with the iodine solution, mop up the excess stain after
standing two minutes, and add a spot of sulphuric acid solution (70 ml. con¬
centrated sulphuric acid added to 30 ml. water).

Aniline Sulphate. Dissolve 1 grm. aniline sulphate in 50 ml. water and
solution as with iodine stains.

Phloroglucinol. Dissolve 1 grm. phloroglucinol hydrochloride in 50 ml.
ethyl alcohol and add 25 ml. concentrated hydrochloric acid. Apply the stain
as with iodine stains.

364 MODERN PAPER-MAKING

PAPER TRADE CUSTOMS

CODIFIED AND ADOPTED BY THE PAPER-MAKERS* ASSOCIATION OF GREAT BRITAIN

AND IRELAND (INCORPORATED); THE NATIONAL ASSOCIATION OF WHOLESALE

STATIONERS AND PAPER MERCHANTS; THE EMPLOYERS* FEDERATION OF

ENVELOPE MAKERS AND MANUFACTURING STATIONERS; AND THE UNITED

KINGDOM PAPER BAG MANUFACTURERS* ASSOCIATION

Group Reference Letters.—A: Cloth-lined Papers, Coated Art Papers and
Enamels, Copyings, Tissues, Drawing Cartridges, Drawing Papers, Blottings,
Dryings, Filterings, Duplicators, Foils, Gum Papers, Insulating Papers, Machine
Writings and Printings, Pulp Boards, Tracing Papers, Envelope Papers, Manillas
for other than wrapping purposes, Caps for other than wrapping purposes, and
similar papers. B: Cards, Pasteboards, Glazed Pressing Boards, Greaseproof,
Imitation Parchment, News, Waterproof Papers, Waxed, and similar papers.
C: Box Boards, Browns, Corrugated Straw, Leather Boards, Middles, Mill
Boards, Mill Wrappers, Sugars, Casings, Krafts, Sealings, Wrappings,
Cartridges, and similar papers.

Conditions of Sale— Prices may be agreed: (i) By weight, whether put up in
reams, reels, or any other form. (2) Per ream, based upon nominal weight.

Terns and Delivery.— (1) Quotations are understood to be net and carriage
paid to buyer’s address. Goods invoiced and despatched up to and including
25th of the month shall be paid for during the following month, provided
delivery has been effected by date when payment is due. (2) Delivery in the
British Isles shall include delivery at buyer’s warehouse or that of his consignee.

Packing and Marking— Boards, Frames, Cases, and Special (not ordinary
cardboard) Centres shall be chargeable at reasonable rates, to be refunded in
full when returned -within a reasonable time, carriage paid and in good condition.
The outside of the wrapper of each ream shall be marked with the nominal
weight, except in cases where the weight charged is above nominal.

Machine-Made Writings, Printings, etc.—A ream contains 500 sheets. Reams
are graded as ‘Good’, ‘Retree’ and ‘Broke’. ‘Retree’ is subject to 10 per cent
reduction. ‘Broke’ is subject to 20 per cent reduction. All fine papers under
15 lb. Large Post 500’s shall be classed as ‘Bank*.

Wrappings, Caps, etc.—A ream contains 480 sheets.

Hand-Made Papers.—A ‘Mill’ ream ‘Good’ or ‘Retree’ contains 472 sheets,
consisting of 18 ‘Inside’ quires of 24 sheets each and 2 ‘Outside’ quires of 20
sheets each. The ‘Outside’ quires are placed one at the top and one at the
bottom of the ream. An inside ream ‘Good’ or ‘Retree’ contains 480 sheets,
made up of 20 ‘Inside’ quires of 24 sheets each. ‘Retree’ is subject to 10 per
cent reduction, and ‘Broke’ to 50 per cent reduction.

PAPER TRADE CUSTOMS

3<55

Wrappers.— The chargeable weight shall include weight of necessary Ream
and Reel Wrappers (not Bale Wrappers), String and Centres (excepting those
of wood or metal).

Substance Variations.—Average variation shall not exceed 5 per cent either
way. Group ‘A’: Nominal weight of sheets and reels shall be chargeable if
actual weight exceeds or is not more than 2$ per cent under nominal weight.
Actual weight shall be chargeable if more than 2\ per cent under nominal
weight. Group ‘B’: Actual weight of sheets and reels shall be chargeable
up to 2\ per cent in excess of nominal. Group ‘C’: Actual weight of sheets
and reels shall be chargeable provided average variation does not exceed 5 per
cent either way.

Short Yardage.— Claims for short yardage can only be based upon result
obtained from yardage measurements.

Measurement Variations.— (1) Width of reels shall not vary more than £ per
cent, with a maximum permissible variation of £ inch. (2) The variation in
measurement of paper in sheets must not exceed £ per cent either way above
or below the ordered measurement, provided always that where £ per cent
is greater than £ inch the permissible variation shall be £ inch, and that where
£ per cent is less than £ inch the permissible variation shall be £ inch.

Special Makings.— For makings of Groups ‘A’, ‘B’ and ‘C’ of special size,
substance, tint, water-mark, etc., an order shall be deemed to be properly
filled if the quantity supplied is within the following limits either way of the
quantity ordered: 1 ton or less, I2| per cent; above 1 ton and not exceeding
5 tons, 7| per cent; above 5 tons, 5 per cent; not applicable to hand and mould
mades. Any excess beyond such limits shall be cut down to the nearest standard
size and taken by the buyer at the proportionate price of such size.

Materials.— Unless it is otherwise expressly stipulated in the order, the paper-
maker shall be free to use his discretion in the selection of materials.

Dandy:Rolls and Moulds.— Buyers requiring a special water-mark shall provide
the roll or moulds free of charge to the paper-maker.

Deliveries.— Deliveries may be suspended in the event of: (1) Any con¬
tingency arising beyond the control of the buyer or seller, such as war, fire,
drought, interruption of transport, impediment to navigation through ice,
strikes, lock-outs, and the like. (2) Any accident and/or partial damage
during such time as may be required to make good such accident and/or
damage. The buyer or seller, as the case may be, shall give prompt notice
to the other party of the cause and commencement of such suspension, and
in like manner when it ceases. In such cases deliveries shall be resumed as
soon as is practicable, and where they form part of a contract spread over
periods of time, they shall be resumed at the same rate as provided for in the

366

MODERN PAPER-MAKING

contract. In the event of the works of the buyer or seller being totally
destroyed, and not rebuilt or replaced within twelve months, the contract
.shall be considered null and void. In the case of contracts for delivery in in¬
stalments, each delivery shall be considered a separate contract.

Delayed Deliveries — (i) Specification of makings shall be sent to the seller
in reasonable time for delivery on due date. If the paper contracted for be
ready for delivery on the specified date, and the buyer does not take delivery
when requested by the seller to do so, it shall be invoiced forthwith and invoice
taken to account. If the whole of the delivery be not ready, the seller shall not
be entitled to invoice any portion. (2) Paper stored at mill shall be subject to
a rent charge of 6d. per ton per week for any period it lies at mill after 14 days
from date of invoice, except in cases where delay is due to causes beyond buyer’s
control. Maximum period for storing at mill shall be 3 months.

Complaints of Quality, etc.—Claims for defective quality, short, weight etc.,
shall be made in writing within 14 days after delivery, but this is not to operate
in cases where defective quality cannot reveal itself during this period. Such
protection shall not be given beyond 3 months. In cases where delivery
is within the British Isles, at least half the parcel must be available for exami¬
nation. For export business, six representative outturn sheets shall be supplied
with invoice, but the English exporter is entitled to return to the question
of quality in cases where his export buyer subsequently reports any defect
not revealed by outturn sheets.

Contracting Out .—Any or all of these terms may be varied or made in¬
applicable by the terms of the contract or order.

Arbitration.—(1) All disputes arising under any contract or order shall be
submitted to arbitration in the United Kingdom. ( 2 ) Each party shall appoint
his arbiter, and the arbiters shall choose their umpire before proceeding. If
the dispute relates to quality, the arbiters and umpire must be experts in paper,
and they shall decide whether the paper complained of is a fair commercial
match of quality to be supplied. Should they decide that it is not, they may
authorise rejection, or they may order acceptance subject to stated allowance,
in which latter case they shall state whether the allowance shall apply to all
or part of such portion as has been used before their examination, and their
decision shall be final and binding on both parties. Should either side fail to
appoint his arbiter within the prescribed 14 days, the arbiter appointed by the
other party shall act for both, and his award shall be binding on both parties
as though he had been appointed with their joint consent. The costs of such
reference shall be borne as the arbiters and umpire decide.

Note.—The trade customs as codified in January, 1906, are hereby can-
celled.

Equivalent Weights of Printing Papers expressed in Terms op Lbs. 48o*s

APPENDIX OF TABLES

367

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368

MODERN PAPER-MAKING

Substance Equivalents: Grammes and Pounds.

Grammes

per

Square

Mette

Demy (22| X 17J)

Royal (25X20)

Double Foolscap
(27X 17)

Double Crown
(30X20)

crt

0 -=>

00j

500’s

Lb.

516’s

Lb.

480’s

Lb.

500’s

Lb,

516’s

Lb.

480’S

Lb.

500’s

Lb.

516’s

Lb.

480’s

Lb.

500’s

Lb.

516’s

Lb.

20 ..

5.38

5.6

5-78

6.82

7-1

7-33

6.26

6.52

6.73

8.19

8.53

8.8

21 ..

5.64

5.88

6.06

7.16

7.46

7-7

6.57

6.84

7.06

8.6

8,96

9.24

22 ..

5.91

6.16

6.35

7-5

7.81

8.06

6.89

7.17

9.01

9-39

9.68

23 ..

6.18

6.44

6.64

7.84

8.16

8.43

7-2

7*5

7-74

9.42

9.81

10.13

24 ..

6.45

6.73

6.93

8.18

8.52

8.79

7.5i

7.82

8.07

9-83

10.24

10.57

25..

6.72

7.0

7.22

8.52

8.87

9.16

7 82

8.15

8.41

10.24

10.67

11.01

26 ..

<5.99

7,28

7 5i

8.87

9*23

9-53

8.14

S.48

s.75

10.65

11.09

11.45

27 ..

7.26

7.56

7*8

9.21

9-59

9-9

8.45

8.8

9.08

11.06

11.52

xi.89

28 ..

7.53

7.84

8.09

9-55

9-95

10.27

8.76

9.12

9.42

11.47

H-95

12.23

29 ..

7.8

8.12

8.38

9.89

10.3

10.63

9.08

9-45

9.76

11.88

12.38

12.77

30..

8 06

8.4

8.66

10.23

10 66

11.0

9.39

9.78

10.09

12.29

12.8

13.21

31 -■

8.33

8.68

8.95

10.57

II.OI

11.36

9-7

IO.I

10.43

12.7

13.23

13.65

32 ..

8.6

8.96

9.24

10.91

11.36

n.73

10.02

10.43

10.77

13.11

13-66

14.09

33 -■

8.87

9.24

9-53

11.25

11.71

12.09

10.33

10.76

II.X

13.51

14.08

14-53

34 --

9.14

9.52

9.82

11.59

12.07

12.46

10.64

xi.08

n-44

13.93

14.51

14-97

35 ..

9.41

9.8

10.11

11.93

12.43

12.83

10.95

11.41

11.77

14.34

14.93

15.42

36 ..

9.68

10.08

10.41

12.28

12.79

13.2

11.27

11.74

12.X1

H.75

i5-3<s

15.86

9.95

10.36

10.7

12.62

13.15

13-57

11.58

12.06

12.45

15.16

15-79

16.3

38 ..

10.21

10.64

10.98

12.96

13-5

13.93

11.89

12.39

12.78

15-57

16.22

16.74

39 ..

10.48

10.92

11.27

13-3

13.85

14.29

12.21

12.72

13-12

15.98

16.64

17.18

40 ..

10.75

11.2

11 56

13 64

1421

14.66

12.52

13.04

13.46

16.38

17.06

17.61

41 ..

11.02

11.48

11.85

13.9S

14.56

15.02

12.83

13-37

13-79

16.79

17-49

18.05

42 ..

11.29

ix.76

12.14

14-32

14.91

15.39

13-15

13.7

14.13

17.2

17.92

18.49

43 ••

11.56

12.04

12.43

14.66

15.27

15.76

1346

14.02

14.47

17.61

18.34

18.93

44 --

11.83

12.32

12.72

15.0

15.62

16.12

13*77

14.34

14.8

18.02

18.77

19-37

45 ..

12.1

12.6

13.01

15.34

15.98

1649

14.08

14.67

15.14

18.43

19.2

19.81

4 6 ..

12.36

12.88

13*29

15.69

16.34

16.86

14.4

15.0

15.48

18.84

19.62

20.25

47 - •

12.63

13*16

13.58

16.03

16.7

17.23

14.71

15-32

15.81

19.25

20.05

20.69

48 ..

12.9

13*44

13.87

16.37

17.06

17.6

15.02

15.65

16.15

19.66

20.48

21.13

49 • •

13-17

13-72

14.16

16.71

1741

17.96

15-34

15.97

16.49

20.07

20.91

21.57

50 ..

13.44

14.0

14.45

17.05

17.76

18.33

15.65

16.3

16.82

20.48

21.33

22.02

60 ..

16.12

16.8

17*33

20.46

21.3

21.99

18.78

19.56

20.18

24.58

25.6

26.42

70 ..

18.88

19.6

20.22

23.86

24.85

25.66

21.9

22.81

23.54

28.68

29.87

30.83

SO . .

21.5

22.4

23.11

27-27

28.4

29.32

25.03

26.0

26.91

32.77

34-13

35-23

90 ..

24.19

25.2

26.0

30.68

31.96

32.98

28.16

29.33

30.27

36.86

384

39-63

IOO . .

26.88

28.0

38.9

34-i

35.52

36.65

3i.3

32.6

33.64

40.96

42.67

44.03

, WdgmultipKedby0.41 = weight 20X30 480’s. Example: 30X0.41 = 12.3011
m.nJ T 4 1464 -axea in inches gives grammes per square metre. Example: i 5 x j^ajxao-^

grammes

APPENDIX OF TABLES

Strawboards: Equivalent Number per Cwt.

369

Weight of

Board .

22x 32
704

20X25

500

20X30

600

24x38

912

25X30

750

27x34

918

28X36

1008

30X40

1200

4 oz.

448

631

526

346

421

344

313

263

6 „

299

421

354

231

281

229

209

175

8 „

224

315

263

173

210

172

156

131

10 „

179

252

210

138

168

137

125

105

12 „

149

210

175

115

140

113

104

14 „

128

180

150

120

16 „

112

158

I 3 i

105

18 „

100

141

117

20 „

127

106

1* lb.

106

i-i „

2 „

5<5

2i „

3 i

2 f' „

38 '

3 i

3 „

3 * „

4 »

Basis, 22 X 32. The figures under size in heading indicate square inches

French and Belgian Sizes of Paper

Name

Size in
Centimetres

Size in
Inches

Name

Size in
Centimetres

Size in
Inches

Grand Aigle.

104 X70

41 X271

Carre .

S6 X 4 S

Mix 17 i

Grand Colombier

90 X63

3 six Mi

Coquille

56 X44

22JX I7l

Colombier.

85 X62

32JX24J

Petit Median

53 - 3 X 40

21 XI5|

Petit Aigle.

84 X 60

33 iX 23 f

Ecu .

52 X 40

20jX I 5 i

Petit Colombier

80 X 60

3ifX 23$

Couronne.

46 X 36

18JX I 4 i

Grand Soleil.

80 X 57

3I&X22J

Ruche .

46 . 2 X 36

18JX I 4 i

Elephant .

77 X62

3ofX 24J

Griffen .

45 X35

I7fx 13 j

Jesus.

76 X 56

30 X22J

Telliere .

44 X34

I 7 |X I 3 i

Jesus.

70 X 55

27|X2lj

Propatria.

43 X34.5

17 XI 3 |

Super Royal.

70 X50

27fX19J

Almasso.

44 X32.5

I7|X 12J

Petit Soleil.

68 X50

2 < 5 fX I 9 |

Petit Raisin

43 X32

17 X12J

Raisin .

65 X 50

ajfX19I

Pot.

40 X31

I5|X 12^

Royal.

63 X 48

Mi x 19

Cloche .

40 X30

I5fx lif

Cavalier .

62 X 46

24 X 18J

Lys.

39.7X3I-7

15# x I2f

Grand Mddian

60.5X46

Mi x I8J

Rosette .

34-7X27

i3|x io|

The above is a selection from an extensive range of prevailing sizes. The dimensions given are those most frequently
used; but there is considerable variation in different qualities of papers and different makers

370

MODERN PAPER-MAKING

Equivalent Sizes in Inches and Centimetres

Size

Inches

Centimetres

Size

Inches

Centimetres

Emperor

72 X48

183.0X 121.9

Demy

22JX I7J

57 . 1 X 444

Antiquarian ..

53 X31

134.6X 78.7

Post.

39 XI 5 i

48.2x38.7

Double Elephant

40 X26J

101.6X 68.0

Pinched Post

I8£x Hi

49-0X37.4

Atlas ..

34 X26

86.4X 66.0

Foolscap

I6£X I 3 i

41.9x33.6

Colombier ..

34 iX 23 j

87.6X 59.7

Pot.

15 x 12J

38.1x31.7

Imperial

.. WDPC

30 X22

76.2X 55-9

Short and $ Foolscap

22 X 13$

55 . 9 X 34.2

Elephant

.. WDC

28 X23

71.IX 584

Short and | Foolscap

24 x 13J

62.2x34.2

Cartridge

26 X 21

66.0X 53.3

Double Foolscap

2 6£x 16J

67.2X41.9

Super Royal ..

27 XI9

68.6 X 48.2

,, „

27 X17

68.6X43.2

>j »

27^X20$

69.8 X 52.1

Double Crown

30 X 20

76.2X50.8

Royal..

24 XI9

61.0X 48.2

Double Post

30JX19

77.5X48.2

»»

25 X 20

63.5X 50.8

3 ljx I 9 i

80.0X49.5

Medium

22 XI7J

55-9 X 444

Double Large Post ..

33 X 21

83-8X53.3

”

23 Xl8

584X 45-7

Double Demy

31 X 20

78.7X50.8

Large Post

21 XI6J

53-3 x 41.9

Ji jj • •

35 X22J

88.9x57.1

Copy ..

20 Xl6

50.8 X 40.6

„ „ ..

35 jX 22^

90.2X57.1

Demy ..

20 XI5J

50.8 x 39.3

Music Demy

20 x15J

50.8X39-3

w, Signifies Writings; d, Drawings; p, Printings; c, Cartridges

Comparative Weights in Lbs. and Kilos, calculated Comparative Weights in Kilos, and Lbs. calculated
on Basis op 1016 Kilos, to an English Ton on Basis of 1016 Kilos, to an English Ton

Lbs.

20
21
22

Kilos.

0-454

0.908

1.361

1.815

2.268

2.722

3 .I 7 S

3.629

4.083

4.536

4.990

5-443

5.897

6.350

6.804

7.258

7.711

8.165

8.618

9.072

9.525

9-979

Lbs.

35
40
45
50
56
60
65
70
75
80

Kilos.

10.433

10.886

11.340

11.793

12.247

12.700

13-154

13.608

14.061

14.515

14.967

15.422

15.875

18.143

20.411

22.679

25.400

27.215

29.483

31.750

34.018

36.286

Lbs.

Kilos.

90
100
112
120
130
140
150
160
170
180
190
200
224
250
300
336
350
400
500
560
1120

38.100

40.822

45.358

50.800

54-429

58.964

63.500

68.036

72.572

77.108

81.643

86.179

90.715
101.600
113.393
136.072
152.400
158.750
181.429
226.786
254.000
508.000

Note.—A n easy way to find the nominal comparative
weightis to multiply the number of pounds by 454, and
divide by 1000. The result is number of kilos.

Kilos.

Lbs.

Kilos.

Lbs.

Kilos.

Lbs.

2.205

50.709

187.401

4409

52.913

198.425

6.614

55 -n 8

100

220.472

8.819

57.323

242.520

11.024

59.527

120

264.567

13.228

61.732

130

286.614

15433

63-937

140

308.661

17.638

66.142

150

330.709

19.842

3 i

68.346

160

352.756

22.047

70.551

170

374.803

24.252

72.756

180

396.850

26.457

74.960

190

418.898

28.661

77-165

200

440.945

30.866

88.189

250

551.181

33.071

99.212

300

661.417

35.276

110.236

350

771.654

37480

121.260

400

881.890

39.685

132.283

1102.362

41.890

143.307

600

1322.834

44.094

154 . 33 1

700

1543.307

46.299

165.354

800

1763.780

48.504

176.378

900

1984.252

Note. An easy way to find the nominal comparative
weight is to multiply the number of kilos by 1000,and divide
oy 454 * The result is number of pounds.

APPENDIX OF TABLES

37 i

To calculate the output of a machine:

Multiply the deckle width in inches by the speed in feet per minute; multiply
the result by the substance of the paper in double crown (20 x 30) 480’s. Divide
the result by 400. The resulting figure is the number of pounds per hour.

Example: Deckle=i30 inches. Speed=6oo feet per minute. Substance=
20 lb. double crown 480 sheets.

130x600x20 ., .

-=3900 lb. per hour.

400 r

Another method:

To calculate the output of a machine: Multiply weight per ream by speed
per hour in inches by width of web in inches, and divide the result by length
of sheet multiplied by breadth of sheet and by number of sheets per ream.

Weight per ream X speed per hour in inches x width of web
Length of sheet x breadth of sheet x sheets per ream

Example: Speed, 100 feet per minute. Deckle width, 68 inches. Sub¬
stance, i6|X2i=2i lb. 500 sheets.

21 x (100 x 12 x 60) x 68
16^x21x500

=593 lb. per hour.

To find equivalent weights of different sizes of sheets: Multiply known
ream weight by length and breadth of sheet, the weight of which is required,
and divide the result by length and breadth of sheet the weight of which is
known.

Ream weight x (length and breadth of sheet of unknown weight)
Length x breadth of sheet of known weight

Example: Sheet 20x25=25 lb. per ream.

Find equivalent weight of sheet 20 x 30:

2 5 x (20x30) lb
20X25

To find the .weight of paper required for a web of a given length, breadth
and substance:

Multiply the ream weight by the length of web in inches and by the breadth
in inches; divide the result by the number of sheets per ream, multiplied by
the length and breadth of sheet.

Ream weight x length of web in inches x breadth of web in inches
Sheets per ream X length of sheet x breadth of sheet

372

MODERN PAPER-MAKING

Example: Find the weight of paper required to produce a web 600 yards
long by 30 inches broad, the paper being the substance of 20x30=^=25 lb. 500
sheets per ream.

25 x (600x36) X30
20x30x50 ^

To find the substance of paper in a web of given length, breadth and weight
in any size of sheet and number of sheets per ream:

Multiply the weight of web by the length, breadth and number of sheets per
ream, and divide result by length of web in inches and breadth of web in inches.

Weight of web x length of sheetx breadth of sheetxNo . of sheets per ream
Length of web in inches x breadth of web in inches

Example: Find the weight in 20x30—500 sheets of a web 600 yards long
and 30 inches wide weighing 54 lb.

54x500x20x30

=25 lb.

(600x36^30
To find the weight of a web of paper:

Multiply width of web in inches by yardage, multiply result by substance
in double crown (20x30) 480 sheets, divide result by 8000 and the result is
the weight of the web in pounds.

Multiply width of web in inches by yardage, multiply result by substance in
demy 480 s and divide by 5350. The result is the weight of the web in pounds.

To find the cubical contents of any square or rectangular vessel, multiply
the length, breadth and depth together.

Example: Find the number of cubic feet in a tank 6 feet long, 4 feet wide
and 3 feet deep:

6x4x3=72 cubic feet.

To find the number of gallons a tank will hold, proceed as above and multiply
the result in cubic feet by 6.23 5 5, this being the number of gallons in 1 cubic foot.
Extending the above example:

6x4x3x6.2355=448.956 gallons

To find the weight of water in a tank, proceed as above and multiply die
number of gallons by 10 (1 gallon of distilled water weighs 10 lb.).
Extending the above example:

6x4x3x6.2355x10=4489.56 lb.

To find the cubical contents of a cylindrical vessel, square the diameter

APPENDIX OF TABLES

373

(i.e., multiply the diameter by itself), then multiply the result by 3.1416. Divide
the result by 4, then multiply by depth.

Example: Find the cubical content of a vessel 4 feet in diameter by 3 feet
in depth.

(4X4)X3.1416x3
4

37.6992 square feet.

To find the number of gallons proceed as for a square or rectangular vessel
(see previous examples).

To find the nominal comparative number of pounds in kilos: Multiply the
number of pounds by 454 and divide by 1000. The result is the number of kilos.

Vice versa : Multiply the number of kilos by 1000 and divide by 454. The
result is the number of pounds.

Bleach Liquor .—One cwt. (112 lb.) of dry bleaching powder of 36 per cent,
strength produces approximately:

250 gallons of 5 0 Tw. liquor.

208 „ 6°

178 „ 7 °

Cylindrical Tanks: Diameters, Circumferences, Areas and Capacities

Diameter

Circum¬

ference

Area

Capacity
at 1 -Foot
Depth

Diameter

Circum¬

ference

Area

Capacity
at i-Foot
Depth

Ft.

In.

Ft.

Sq. Ft.

Gallons

Ft.

In.

Ft.

Sq. Ft.

Gallons

3.14

0.78

4-8

29.84

70.88

441.7

3.92

1.22

7.6

3141

78-53

489.4

4.71

1.76

11.0

34-55

95-03

592.2

549

2.40

15.0

37-69

113.09

704.8

6.28

3.14

19.5

40.84

132.73

829.5

7.06

3-97

24.7

43-98

153.93

959.3

7.8s

4.90

30.6

47-12

176.71

1101.3

8.63

5-93

37-0

50.26

201.06

1253.0

9.42

7.06

44.0

5340

226.98

1414.5

10.21

8.29

5 i .7

56.54

254-46

1585.8

11.00

9.62

59.9

59.69

283.52

1766.9

11.78

11.04

68.8

62.83

314-15

1957-8

12.56

78.3

65-97

346.36

2158.5

13.35

14.18

88.4

69.11

380.13

2369.0

14.13

15.90

99-1

72.25

415-47

2589.2

14.92

17.72

110.4

75-39

452.38

2819.3

15.70

19.63

122.3

78.53

490.87

3059.1

16.49

21.64

134.9

81.68

530.92

3308.8

17.27

23.75

148.0

84.82

572.56

3568.1

18,06

25.96

161.8

87.96

615.75

38374

18.84

28.27

176.2

91.IO

660.52

4 II 3.7

20.42

33.18

206.8

94.24

706,86

4402.3

21.99

38.48

239.8

109-95

962.11

5992,0

23.56

44.17

275-3

125.66

1256.63

7826.3

25.13

50.26

313-2

I 4 I -37

159043

9905.2

26.70

56.74

353-6

157.08

1963.50

12228.6

28.27

63.61

3964

_1_

374

MODERN PAPER-MAKING

Useful Equivalents

Imperial Metric

In. Ft.

i inch = 254 mm.

1 millimetre = 0.0393 = 0.0032

r foot = 30480 cm.

1 centimetre = 0.3937 = 0,0328

1 yard = 0.9144 m.

1 decimetre = 3.9370 = 0.3280

1 furlong = 0.2011 km.

1 metre = 39.3701 = 3.2808

r mile = 1.6093 km.

1 kilometre = 0.62137 ml. = 3280.8

1 sq. in. = 64516 sq. cm.

1 sq. millimetre — 0.0015 sq. in.

1 sq. ft. = 0.0929 sq. m.

1 sq. centimetre = 0.1550 sq. in.

1 sq. yd. = 0.8361 sq. m.

1 sq. metre — 1.1959 sq. yd.

1 acre (4,840 sq. yd).=4046.87 sq. m.

(10.7639 sq. ft.)

r sq. mile = 259.000 hectares

1 are = 119.59 sq. yds.

1 hectare = 2.471 acres

1 cu. in. =s 16.3872 cm. 3

1 cu. centimetre = 0.0610 cu, in.

1 cu. ft. = 0.0283 m. 3

1 cubic metre = 35-3145 cu. ft.

1 cu. yd. = 0.7645 m. 3

(Stere) (1.3079 cu. yds.)

r pint = 0.5682 litre

1 cu. centimetre = 0.0338 fluid oz.

1 quart = 1.1364 litres

(0.2705 fluid dram)

1 gallon = 4-5459 litres (277419 cu. in.)

1 litre (1000 c.c.) = 0.220 gal.

1 cu. metre (1000 litres) =220.083 gals.

1 grain = 0.0648 gramme

1 milligramme = 0.0154 grain

1 dram = 1.772 grammes

1 centigramme = 0.1543 grain

1 oz. = 28.349 grammes

1 gramme = 15.4323 grains

1 lb (7000 grains)=o.4536 kg.

1 kilogramme = 2.2046 lb.

1 cwt. = 50.80 kg.

I quintal = 1.9684 cwt.

1 ton = 1.016 tonnes

1 tonne =2204.62 lb. (0.9842 tons)

1 b.p, (33,000 ft.-lbs. per min.)

1 joule = 0.7373 ft.-lb.

=745-9 joules per sec.

1 joule per sec. (1 watt)=o.ooi34 h.p.

1 ft.-lb. (13,825.5 gm. cm.)

1 metric h.p, = 0.9863 h.p.

= 1.3 562 joules

1 metric h.p. hr. = 1,952,910 ft.-lb.

1 h.p, hr. (1,980,000 ft.-lbs.)

1 calorie or heat unit = amount of heat required to raise the

= 2,685,443 joules

temperature of 1 gramme of water 1 degree centigrade.

1 watt-hr. (2654.31 ft.-lbs)

= 3600 joules per sec.

1 lb. per sq. in. = 0.0703 kg. per sq. cm.

Reciprocal,

14.2234

1 lb. per sq. ft. = 4.882 kg. per sq. m.

0.2048

1 grain per gal. = 0.0142 gramme per litre

70.1160

1 lb, per 1000 gals. = 0.1 kg. per m. 3

10.0

1 Imp. gal. = 277419 cu. in.

0.0036

1 Imp. gal. = 0.1605 cu. ft.

6.2278

1 Imp. gal. = 1.2003 U.S. gals.

0.8330

I cu. ft.= 6.2278 Imp. gals.

0.1606

1 cu. ft. = 62.2786 lb.

0.0160

1 inch rainfall = 22,600 gals, per acre

1 gal. per sq. ft.= 48.895 litres per sq. metre

0.0204

I gal. per sq. ft. hr. = 1.17 cu. metres per sq. metre per day

0.8550

1 gal. per sq. ft. hr. = 1.92 vertical in. per hour

0.5200

1 gal. per sq. ft. hr. = 1,045,000 gals, per acre per day

1,000,000 gals, per acre per day = 0.96 gal. per sq. ft. per hour

1,000,000 gals, per acre per day = 1.84 vertical in. per hour.

APPENDIX OF TABLES

Heads of Water and Corresponding Pressures

375

Head in
Feet

Pressure
Lbs. per

Sq. In.

Head in

Feet

Pressure
Lbs. per

Sq. In.

Head in
Feet

Pressure
Lbs. per

Sq. In.

Head in

Feet

Pressure
Lbs. per

Sq. In.

04335

2.3067

21.6753

80.7369

0.6502

4.6135

32.5130

92.2707

0.8670

6.9203

100

43-3507

103.8046

2 i

1.0837

9.2271

125

54.1884

115.3384

1.3005

11.5388

150

65.0260

138.4060

1.7340

13.8406

175

75.8637

161.4736

2.1675

16.1474

200

86.7014

184.5415

4.3351

18.4541

250

108.3767

207.6090

6.5026

23.0676

300

130.0520

230.6768

100

8.6701

34.6015

15 '

350

151.7273

288.3460

125

10.8377

46.1354

400

173.4028

346.0152

150

13.0052

57-6692

500

216.7534

403.6844

175

17.3403

69.2030

600

260.1041

4 < 5 i- 353<5

200

Degrees of Hardness of Water

Clark

German

Parts per
100,000

Metric
(Parts per
1,000,000)

Clark .

1.0

1.25

0.7

0.07

German.

0.8

1.0

0.56

0.056

Parts per 100,000.

1.42

1.78

1.0

O.I

Metric (mg. per litre or parts per millioii).

14.2

17.8

10.0

1.0

pH Values

Pure distilled water, before exposure to atmosphere, at 22 0 C. = pH 7.0.

Pure distilled water after exposure to atmosphere = water + carbon dioxide — pH 5.7.

pH values over 7.0 denote alkalinity.
pH values under 7.0 denote acidity.
Hydrochloric acid = pH 1.00

Acetic acid =»

Pure water =

Sodium bicarbonate =
Ammonium hydrate —
Sodium carbonate =
Caustic soda 1 =

2.86

7.00

8.4

11.3

11.6

13-1

376

MODERN PAPER-MAKING

Specific Gravity of Solutions of Caustic Soda (6o° F.= i5 ° C.).

Twaddell

Grammes
per Litre
Na 2 0

Twaddell

Grammes
per Litre
Na 2 0

Twaddell

Grammes
per Litre
Na 2 0

3-7

100.5

5 i

223.4

7-5

105.0

208.9

H -3

109.6

234-4

15.1

114.1

240.0

18.8

118.6

245.5

22.6

3 i

123.2

251.0

26.4

127.7

256.6

30.2

132.2

262.1

33*9

136.8

267.6

37*7

I 4 I .3

273.2

41.6

145.8

279.3

45*5

150.4

285.4

49-4

154*9

291.5

53*2

159*4

297.7

57-1

, 40

164.0

303.8

61.0

169.4

309.9

64.9

174.7

316.0

68.8

180.1

322.2

72.7

185.5

328.3

76.5

190.9

334-4

80.4

196.3

340.8

84.3

201.7

347-2

88.2

207.0

353-6

92.1

212.4

360.1

96.0

217.8

366.5

Note. —To find lb. soda (Na O) per cubic foot, divide grammes per litre by 16

INDEX

Abcstine, 125
Abietic acid, 116
Adka save-all, 352-354
Agalite, 125
Agitators, 137-138
Air-drying, 297 et seq.

Air permeability, 334-336
Alfa, see Esparto
Alplia-cellulose, 64
Alum, 122-124, 260, 261, 292
Aluminium sulphate, 122-
124

Aniline colours, 133-135
Anti-chlors, 32-33
Apron, 160-163

Baby presses, 250
Back knotters, 153, 158-159
Backwater, 260,-352
system, 142, 143
Bagging, 19

Bank-note papers, n, 234
Barium sulphate, 125
Barometric leg, 185
Barytes, 125

Basalt Lava beater roll, 77
Basic dyes, 262
Beaters, 75 et seq., 264
Beating, 74 et seq., 282
free, 87-88, 89, 93
wet, 87, 89 et seq.

Bed plate, 27
Bekk hardness tester, 335
Best fines, 15
Bewoid size, 117 et seq.

Bird screen, 156-157
Bisulphite liquor, 57
Black ash, 358
Blanc fixe, 125
Bleached kraft, 66
soda pulp, 67

Bleaching, 31-33, 38 et seq.
of rags, 31-33
of wood pulp, 48-49
liquor, 31, 373
methods, 45-47

Bleaching, multi-stage, 60
powder, 40,373
towers, 46-47
Blistering, 246
Blotting-paper, 6
Blow rolls, 194
Board machines, 246, 247 et
seq.

Boilers, rotary, 24, 37
stationary, 37-38, 39
Boiling, 355
of rags, 24-27
Box strainer, 157-158
Breakers, groundwood, 264
pulp, 263
rag, 27-31, 282
Breast board, 160
boxes, 160-163, 270
Broke, 106-115, 318
Brush damper, 302
Bulk of paper, 333-334
Bursting strength, 330
Button catcher, 27

Calcium carbonate, 257
sulphate, 125
Calender rolls, 215-216
Carbon black, 132
Carmine, 133
Caustic soda, 24, 355
specific gravity of solu¬
tions of, 376
Causticiser, 360
Cellulose, 1
alpha-, 64
hemi-, 60
oxy-, 71'

Centrifiner, 150
Centrifugal machines, 147 et
seq.

Chemical wood pulp, 50, 56
et seq.

semi-, 61-62

China clay, 124, 257, 260
Chlorination, 60
Chlorine, 43-45

377

Colophony, 116
Composition, 336-337
Concentrator, drum, 49
Conditioning of paper, 324-

325

Conical washer, 27
Consistency regulator, 266
Constant humidity, 327-328
Cotton, 2 et seq., 12,13
beating of, 97-101
canvas, 18-19
linters, 2

Couch jackets, 187 et seq.
rolls, 187 et seq., 363
suction, 192-193
Cover washing, 30
Crown filler, 125
Crushing, 169
Curtain cuttings, 13
Cutting, 309 et seq.

to register, 311
Cylinder moulds, 246, 247

Damping, 302 et seq.

Dandy rolls, 228-229, 273
care of, 232

Deckle straps, 176,182-183
Dendritic growths, 339
De Vains, process of, 73
Digesters, 56-57
Dirtec, 152
Doctor, 214-215
Drum washers, 27, 30, 282
Dry felts, 202,210-2x4
Dryers, 275-278
Drying cylinders, 202-204
lofts, 286

Dual press, 196, 274
Duplex cutters, 310,313
papers, 246, 248, 250
Durability of paper,338-34l
Dust, 33-36
Duster, rag, 21, 23
Dyeing, 128 et seq.

Dyes, 262

378

Edge Runner, see KoUergang
Embossing calendar, 308-309
Engine-sizing, 290
English cutter, 309
Erkensator, 147
Esparto, 8 et seq., 70-71
beating of, 105
papers, 9

Evans Rota Belt, 200
Evaporators, 356
Extractors, hydro-, 49

Farina, 122
Feculose, 296
Felt conditioners, 198-202
dryer, 209
rolls, 202
-washers, 198
Felts, 196 et seq.

Fibres, 2 et seq.
knots of, 74
staining of, 363
Fibrillae, 90
Fibrillation, 31
Filter-papers, 11, 283
Filtration treatment, 258
Finishing, 244, 252, 278-279,
306, 318 et seq.

Flat warp wire, 167
Flow box, 163-166
Folding endurance, 332-333
Fourdrinier machine, 13 6 et
seq.

Free beating, 87-88, 89, 93
Froth, 227, 294

Gas bleaching, 45
Gelatine-sizing, 290
preparation for, 291
Glazing, 247
Granite rolls, 194
Grewin system, 277
Groundwood, 256
breakers, 264
Guard board, 190-192
Guillotine, 314
Gypsum, 125

Hand-made paper, 234, 282
et seq.

moulds for, 283 et seq.

INDEX

Hand-sizing, 290-291
Happer felt dryer, 210, 212
Hardness tester, 335
Hardwoods, 52
Harland drive, 219 et seq.
Haubold supercutter, 311 et
seq.

Heads of water and corre-
ponding pressures, 375
Heating of stock, 227-228
Heimbach system, 214
Hemp rope, 19
Herzberg stain, 363
Hollander beaters, 10, 27, 75-
81

Hollow dandies, 229 et seq.
Hydrosulphites, 60

Imitation- hand-made papers,
252

Ink receptivity, 257
Inward-flow strainer, 269

Jet condenser, 356
Jute rope, 19

Kaolin, see China clay
Kellner, and sulphite process,
5<5

Knots, 152

Kollergang, 59, 107, 109
Kraft pulp, 51, 65
bleached, 66-67

Laid rolls, 228, 232
Layboy, 310
Ledger papers, n
LeithWalk strainer, 155-156
Lick-up machine, 246
Liebeck fibrator, 264
Lignocellulose, 12
Linen, 4 et seq., xi et seq .,
101-102

Loading, 124-127, 257, 260,
323

retention of, 126

Machine drive, 216-218
output, 371
wires, 166

Magnesium silicates, 125
Manilla rope, 19

Marshall drive, 218-219
refiner, 96
Maturing, 324-325
Mechanical wood pulp, 50,
53-56, 60-61, 256
M.G. cylinders, 204
press roll, 243
machine, 241 et seq.
papers, 241

Millspaugh automatic couch,
275

Milne, Samuel, 84
Mitscherlich, and sulphite
process, 56

Moisture in paper, 361-363
Mould machine, 252 et seq.
Multiple wire machines, 253
Multi-stage bleaching, 60

Newsprint, manufacture of,
254 et seq.
production of, 254
Neythor Press, 91
Nitrate of iron, 132-133

Ochres, 132

Offset printing process, 9
Old light prints, 17
Opacity, 337-338
Outshots, 15
Oxfords, 14
Oxycellulose, 71

Packing, 322
Paperine, 122

Partington, and sulphite pro¬
cess, 56

Pearl hardening, 125
pH values, 262, 375
Pigments, 130
Pine, 51

Plate glazing, 286,307-309
Pomilio, process of, 73
Potts permeability apparatus,
334

Press rolls, 193, 243, 247
Presse-pate, 49
Presses, 193-197, 273-275
baby, 250
dual, 196
hydraulic, 49
suction, 195-197

INDEX

379

Printing papers, equivalent
weights of, 367
Prints, 14

Projection slice, 160, 163
Prussian blue, 132
Pulp grinder, 53
Pulper, xo8
Purifuge, 150

Rag, 4, 11 et seq ., 21 et seq.
bleaching, 31-33
boiling, 24-25
breaking, 27-31, 282
chopper, 22, 23
cotton, 11
duster, 21, 23
linen, 11
papers, 319
sorting, 21
washer, 348
willow, 23

Raw materials, handling of,
258

Ream counter, 313
Refiners, 93-96, 265
Register, 231
Resin size, 116-117
Retree, 318
Retting process, 4
Revolving cutter, 309
Richardson-Key expanding
cylinder, 253

Ritter, and sulphite process,

Rod-milling, 59
Rosin, 116
-wax size, 119-120
Rotameter, 266
Rotary boilers, 24, 37
furnace, 357
vacuum filters, 49
Rotor whitewater circulation
system, 143-145
Rubber, 21

Sand catcher, 27
traps, 145-147
Satinite, 125
Save-all, 348

Sciennes beating engine, 84-
86

Seconds, 15 et seq.

Shake, 225
Shive, 12, 18
Silicate of soda, 120-122
Sinclair boiler, 38, 39
Sizing, 286
agents, 11 6 et seq.

Sizes of paper, equivalent,
370

French and Belgian, 369
Slices, 163-166, 224, 268 et
seq.

projection, 271
Slitting, 314 et seq.

Smalts blue, 132
Smith, Sigurd, 89
Smoothing press, 273
rolls, 214-215
Smoothness tester, 335
Soda ash, 24
process, 58
pulp, bleached, 67
recovery, 355 et seq.
Sodium silicate, 120
sulphide, 58
sulphite, 32
thiosulphate, 32-33
Sorting, 318 et seq.

Spray damper, 303
Stacked press, 274
Stains, 363
Starch, 120
-silicate, 122
Static electricity, 313
Stationary boilers, 37-38, 39
Steam circulation system, 205
et seq.

ejectors-, 185
engine, 216

Storage of paper, 338-341
Strachan, James, 90
Strainers, 152 et seq., 268 et
seq.

auxiliary, 153, 158-159
inward-flow, 269
plates, 153
Straw, 71-73

Strawboards, number per
cwt., 369

Strength, 328 et seq.

Stuff box, 139-140

Stuff chest, 136-137
gate, 140-142
pump, 138-139
Substance, 334
equivalents, 368
Suction boxes, 183-187, 200
* couch rolls, 192-193
presses, 195-197, 273
Sulphate, easy bleaching, 65
process, 58 et seq.
wood pulp, 256
Sulphite, easy bleaching, 63
et seq.

extra strong, 62
process, 56-58
unbleached, 62
wood pulp, 256
Super-calender, 302, 304 et
seq.

Superfine wire, 167

Tables, 361 et seq.

Talc, 125

Tanks, diameters, circumfer¬
ences, areas and capacities,
373

Taylor beater, 10, 82-83
Tearing strength, 333
Terra alba, 125
Testing of paper, 326 et seq .
Thickness, 333-334
Titanium oxide, 125
Tower beater, 10, 83-84
Trade customs, 364-366
Transparency, 337-338
Trimbey proportioner, 266
Triplex papers, 250
Tub-sizing, 290, 291, 293-297

Ultramarine blue, 130, 131
Umpherston beater, 81
Useful equivalents, 374

Vacuum evaporators, 356
pumps, 185, 193
Vapour absorption, 211, 276
Variable speed electric
motors, 217
Vat machine, 247 et seq.

38c

Vickery felt conditioners, 198,
199

Voith flow box, 163-166

Vomiting stationary boilers,

38,39

Vortrap, 151-152

Washers, conical, 27
drum, 27,30, 282

Waste paper, 106, 112 et seq.
waters, 350 et seq.

Water, 258-260
filtration, 343
hardness of, 375
supply, 342 et seq.

Water-marking, 230, 234, et
seq., 287

INDEX

Waterleaf sheet, 284-286
Wave roll, 228
Weight equivalent, 370
Wet beating, 87, 89 et seq.
White water, 349
Wieger, Bruno, 118
Wilkins, B.A. Poulie, 72
Winding, 314 et seq.

Wire, 166 et seq., 271-273
care of, 174-177
flat warp, 167
guide, 177
life of, 172
seam, 169-174
setting of, 177-179
stretch roll, 178
superfine, 167

tube rolls, 179-181
Wood, 5 et seq.
chemical, 5, 50, 56 et seq.
coniferous, 5
deciduous, 5

mechanical, 5, 50, 53-56,
60-61, 256

pulp, 5 et seq., 50 et seq.
Writing papers, 9
equivalent weights of, 367
hand- and machine-made,
11

Yankee machine, 241
Yellow chrome, 132

Vapour absorption Hood fitted to M.G. Machine

□§] VAPOUR ABSORPTION
IIS MILL VENTILATION
AIR FILTRATION
PULP DRYING

Fans for the Paper-making
Industry

S3 Complete Air-conditioning
Schemes

AIR CONTROL INSTALLATIONS LTD.

Telephone: Ruislip 4066 (8 lines)
Telegrams: Controlair-Ruislip

RUISLIP

MIDDLESEX

Many Mills have proved beyond question, by fitting

NAL END-ON

to existing Vacuum Boxes, economy in maintenance
costs and improved efficiency result

We manufacture a type of cover to meet your particular requirements
and would welcome an opportunity of quoting you

JAMES ATHERTON (SYCAMORE) LTD.

BURY, LANCASHIRE

Use No ROSIN

FOR

HARDER SIZING

Boards and Wrappings can be much harder
sized; fifty per cent Alum can be saved, and
Froth abolished by leaving out the Rosin and
using instead

BEWOID PAPERCOLl BETA GRABE SIZE

(100% British)

Bewoid Papercoll A Grade for Fine Papers and
bright shades

EXPORT INQUIRIES INVITED

Details from:

BECKER & CO. LTD.

34/40 Ludgate Hill, London, E.C.4

(World Patents)

Odontoid, Cent. London

City 1671

PURE WATER

IS ESSENTIAL TO
PAPER MAKERS

For the manufacture of good quality paper, an
abundant and reliable supply of pure water is a
necessity. Bell Brothers have nearly 60 years
experience as water purification specialists and
this accumulated technical and practical
knowledge in the treatment of water
is already giving efficient service in
many important Mills throughout
the British Isles and overseas

Some users of BELL PLANT:

J. Dickinson & Co., Watford.

Wiggins, Teape & Co. Ltd., Hele.

St.Cuthbert’s Paperworks Ltd.,Wells.
Portals Ltd., iv/bridge.

North of Ireland Paper Mill Co. Ltd.,
Ballyclare.

BEL
PLANT

FOR EFFICIENT
WATER PURIFICATION

Write for full particulars to:

BELL BROTHERS

(Manchester 1927) LTD.
DENTON, Nr. MANCHESTER

Telephone: Denton 2294 (3 lines)

London Office:

98 BERRYLANDS, SURBITON, SURREY

Telephone: Elm bridge 4032 gj

B&NNETT Sf 7 P r>L

tingle pane, fi f Not etiie

ded by 5v ff t s “ rroun -

ta'buted paniJ Venly dis '
Part,cks of size

[ UST AS GOOD? to.

mjCr o?raDJi/yjnn.‘ Pilot °-

5 Usa»^c

me P a per fibre

Te lepho N e .

' H yde 4<9

‘BenI ELEGRAMS:

B «M>K 0 >p h

, Shu

-m/croscope

^IfutSUfw

o tt >e <hptmonj*?? the Wl*

f* "nsatisfeco mosc of

etnced ^coJ s / u S n U s ^ne dan

l he ‘W quality of w . 6 emU ' Si °" s

the Ben nett P roc W s ' 2es made by

"vy run of co “V s t ' ,e r «ult o?
improvement 5 ^ ^

HVDf)

Bost °n mills

’ Hyde - Cheshire

The Whole Art of doing things Better!

To create something the world wanted ... to
improve it and keep on improving. To set up
a lead which others follow ... to maintain this
leadership by performance and look back at
your many followers

In 1784 David Bentley made the first Calender
Bowl . . . since which he and generations of his
successors have specialized in the art of doing
this one thing, and doing it well

To-day, Bentley’s are still Leaders ... in the
‘finish’ . . . and r
after all—it’s the
‘finish’ that

really counts

BENTLEY L™

SALFORD
IANCHESTER-3

[TELEGRAMS ''fcOWL • MANCHESTER
[TELEPHONE • lUkCtFtlARS «951 -3

aso AT BOMBAY

‘Leith Walk’ Patent
Rotary Drum Strainers

in five sizes

Stuff, Water and
Vacuum Pumps

Centrifuged Pumps

in sizes from 2 in. to 8 in. discharge

Ram Stuff Pumps

Ram sizes from 8 in. to 14 in. diameter
Duplex or Triplex

All are of latest design and of highest efficiency

All arranged for direct drive by motor, or by
belt or rope drive

Patent High Speed Wire Shake Motion

(vertical or horizontal design)

JAMES BERTRAM & SON LIMITED

Leith Walk, Edinburgh 6

Service to the Paper Trade
in its march of Progress

has been our primary aim
since our establishment in

1821

We have made the Paper Makers’ problems
our problems

We have studied these scientifically in our
Laboratory & Designing Departments

We have applied to them all the inventive
genius at our command

Result: Paper Making Machinery of the
Highest Quality & Satisfied Customers

ST. KATHERINE’S WORKS, SCIENNES, EDINBURGH, 9

Vll

Continuity:

Fourdrinier revolutionized paper making. Batch
production gave way to continuous flow

Pomilio revolutionized pulp production. Continuous
digestion—gas chlorination—a uniform product

Economy:

To produce 1 ton esparto paper by the soda-batch
process =?= 3 tons coal

To produce 1 ton straw paper ( 45 % yield on straw)
by the ‘Celdecor-Pomilio ’ process = li tons coal

Quality:

‘Celdecor-Pomilio’ straw paper is as strong in Burst
and Breaking Length as Bleached Sulphite

Plants embodying this process are operating or being
installed in France, North and South Africa, India,
The Philippines, Argentina, Chile, Uruguay, Italy,
Spain, Great Britain

COATING PLANTS

BARYTA COATING, EMULSION COATING,
CARBON COATING, WAXING, TINTING,
SENSITIZING, IMPREGNATING, GUMMING,
GLUING, PASTING AND COMBINING
MACHINERY

FESTOONING AND DRYING PLANTS

T. H. DIXON & CO. LTD.

LETCHWORTH :: HERTS :: ENGLAND

cc ix

MAKERS of CALENDERS
and BOWLS SINCE 1852

We make bowls of all
sizes, from the smallest
to the largest in use,
and are the only makers
of both super calenders
and bowls in this
country

SIR JAMES FARMER NORTON tfS:

ADELPHI IRONWORKS MANCHESTER

FRASER/LONDON/& CO., LTD.
FRASER/SOUTH WALES/ & CO., LTD.
THE BLACK-CLAWSON CO'ENGLAND/ LTD
GARTH ROAD, MORDEN, SURREY.

Typical Hall & Kay Ait Conditioning Plant
installed in a Lancashire Paper Mill

Our specialities for the Paper and Allied Trades include:

Heating, Ventilating and Air Conditioning Plant
Drying and Conditioning Plant for Coated Papers
Constant Temperature and Humidity Control Plant
Vapour Absorption Plant

Patent Paper Maturing and Air Drying Plant (See
page 323)

Happer Patent Felt Dryer, in conjunction with
Bentley & Jackson Ltd. (See page 213)

Our many years experience in the science of Air Conditioning are
at your disposal

L TD -

meets

ASHTON-UNDER-LYNE . LANCS.

HK88

For PIIPEIIITMERS

Superfine Wet Felts, Special Superfine Wet Felts, Coating Sieves,
Special Extra Superfine Wet Felts, Super Woollen Dry Felts,
Suction Press Felts, Grey Woollen Dry Felts, News Felts,
Grey Wet Felts, Superfine Jackets, Cotton Dry Felts, Board Felts

Xlll

MILLSPAUGH

IMPROVEMENTS

FOR PAPER MAKING & BOARD MAKING

Millspaugh Suction Couch Rolls— Spirally-drilled shells.

Millspaugh Suction Press Rolls— Plain bronze or rubber
covered—spirally-drilled shells.

Top Press or Smoothing Rolls —Bronze or Stonite

• covered — cast-iron or centrifugally cast-steel
bodies.

Automatic Press Sections - Stacked,, staggered and
reversing suction presses.

Vacuum Forming Machines - Millspaugh’s revolutionary
simplification of paper making.

Gearless Dryer Systems —Power-reduced drying.

Machine Renovation—Production increased.

I SHEFFIELD

MILLSPAUGH LIMITED, VULCAN ROAD, SHEFFIELD, ENGLAND

THE REISS ENGINEERING COMPANY Ltd.

399 HENDON WAY, LONDON, N.W.4

Rotor.Closed Whitewater Plant for Fourdrinier Machines.
Saves Fibre. Loading. Chemicals. Water.

iqMjxingBox

BSEB

see Drg. No. 1854

3 Stage Heating System —British Patent-

Steam Su

Suction Stage

Compensate.Main t ^ THERMOSTATIC AlR VENT

on Steam Separator.

__Heating Stage_

S'-SteamSeparator/C-SteamCirculatorI'F^FlashSteam Separator.
Forced Draining & Ventilating Saves Steam, & Increases Production.

On Paper & Board Machines. see Drg. No. 1855

Combined Blower & Suction Plant .-
-Fully /Iutomatic-

see Drg. No. 1625

SCAPA DRYERS LTD.

BLACKBURN

LANCS.

MANUFACTURERS

PAPER MAKERS’ FELTS

WOOLLEN FELTS
COTTON DRYERS
ASBESTOS FELTS

Wherever paper is made the standard is

SCAPA

Head Office:
CARTMEL STREET
BLACKBURN
LANCS.

Tel.: BLACKBURN 7701

London Office:

BLACKFRIARS HOUSE
NEW BRIDGE STREET
LONDON, E.C.4

Tel.: CENTRAL 2617

Representatives throughout the World

XVI

GEORGE SCOTT & SON (LONDON) |TD

ERNEST SCOTT & CS UP

ARTILLERY HOUSE - WESTMINSTER • LONDON-S W-I
DURIE FOUNDRY • LEVEN • FIFE • N-B

HENRY BALFOUR & CO. LTD.
ENAMELLED METAL
PRODUCTS CORPORATION
(1933) LTD. ERNEST SCOTT
& CO. LTD. GEORGE SCOTT
& SON (LONDON) LTD.

SG20I2-TXI

XVII

THE UNITED
WIRE WORKS

LIMITED

GRANTON, EDINBURGH, 5

Motto:

Telephone: Edinburgh 83245 (Private Exchange)
Telegrams: ‘Scotia, Phone, Edinburgh’

WEST END ENGINE
WORKS [EDIN.] LTD.

MAKERS OF

GRASS AND RAG DUSTING
MACHINERY

CHLORINATING, CHEMICAL, AND
COLOUR PLANT

POTCHING AND BLEACHING PLANT
BEATING ENGINES
RAM STUFF PUMPS
STUFF CHESTS
TANKS
CALENDERS

TUB SIZING AND HUMIDIFYING
MACHINES

PAPER CUTTERS AND REELERS

170 DUNDEE STREET

“ EDINBURGH

EDINBURGH

Telegrams
WEST END
EDINBURGH

XIX

MAKERS OF
REVOLVING BOILERS,
ESPARTO DIGESTERS,
SIZE PANS AND
SPECIAL PROCESS
VESSELS FOR OVER
100 YEARS

R. LORD & SONS LTD.

(Successors to J. & J. LORD) Established 1843

BARN BROOK BOILER WORKS

TELEPHONE
No. 226

BURY

NEAR

MANCHESTER

ig m? gr nr pi

B. H. BLACKWELL LTD.

iSilllli

§11

i&ZTM

” A "vJL

scientific, technical and
university booksellers

OXFORD

would welcome your
inquiries for technical
publications from all
parts of the World

ENGLISH

AMERICAN

CONTINENTAL

■m Telegrams

BOOKS, OXFORD

Telephone
OXFORD 2217

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