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Full text of "The photographic negative. Written as a practical guide to the preparation of sensitive surfaces by the calotype, albumen, collodion, and gelatin processes, on glass and paper, with supplementary chapters on development, etc., etc"

THE 



PHOTOGRAPHIC NEGATIVE, 



WRITTEN AS 

A PRACTICAL GUIDE 

TO THE PREPARATION OF SENSITIVE SURFACES BY THE 
CALOTYPE, ALBUMEN, COLLODION, AND GELATINE PRO- 
CESSES, ON GLASS AND PAPER, WITH SUPPLEMENT- 
ARY CHAPTERS ON DEVELOPMENT, ETC., ETC. 

3? 1 1 

BYTHE iMA 

-- 1 ' 1 

REV. W. H. BURBANK, 

Author of Photographic Printing Methods, etc., etc. 



NEW YORK: 
SCOVILL MANUFACTURING COMPANY. W. IRVING ADAMS, Agent. 

1888. 




Entered, according to Act of Congress, in the year 1888, by the 

SCOVILL MANUFACTURING COMPANY, 
in the Office of the Librarian of Congress.'at Washington, D. C. 



-B 



CONTENTS. 



PREFACE 3 

CHAPTER I. 

GENERAL REMARKS ON SENSITIVE SURFACES, ETC 7 

CHAPTER II. 
PRELIMINARY REMARKS ON EXPOSURE, DEVELOPMENT, FIXING, ETC. . . 23 

CHAPTER III. 
CALOTYPE 32 

CHAPTER IV. 
SENSITIVE SURFACES ON GLASS. PREPARATION OF THE GLASS 39 

CHAPTER V. 
THE ALBUMEN PROCESS 44 

CHAPTER VI. 
THE OLD COLLODION PROCESS, WET PLATES 50 

CHAPTER VII. 
THE COLLODION PROCESS, DRY PLATES 65 

CHAPTER VIII. 
COLLODION EMULSION. COLLODIO-.BROMIDE OF SILVER . 73 

CHAPTER IX. 
THE GELATINE PROCESS 86 

CHAPTER X. 
COATING THE PLATES 110 

CHAPTER XI 
DEVELOPMENT, FIXING, ETC 115 

CHAPTER XII. 

PAPER NEGATIVES. STRIPPING FILMS ON PAPER, CARD-BOARD, AND 
COLLODION 130- 



11 CONTENTS. 

PAGE 

CHAPTER XIII. 
FAILURES IN THE GELATINO- BROMIDE PROCESS 147 

CHAPTER XIV. 
METHODS OF STRIPPING FILMS FROM GLASS PLATES 151 

CHAPTER XV. 
COLOR-SENSITIVE PLATES 153 

CHAPTER XVI. 
BLACK AND WHITE NEGATIVES 160 

CHAPTER XVII. 
INSTANTANEOUS PHOTOGRAPHY 164 

CHAPTER XVIII. 

TOUCHING-UP THE NEGATIVE 169 

CHAPTER XIX. 
PHOTO- MICROGRAPHY 171 

CHAPTER XX. 
MICRO-PHOTOGRAPHY 183 

CHAPTER XXI. 
THE TRANSFORMATION OF NEGATIVES INTO POSITIVES 186 

CHAPTER XXII. 

OBERNETTER'S METHOD FOR THE DIRECT PRODUCTION OF NEGATIVES 
FROM NEGATIVES . . .190 



INDEX 193 



PREFACE. 

THIS book, like its companion, "Photographic Printing 
Methods," is the outcome of my wish to testify to the exceed- 
ing great interest which I take in photography, an interest 
which has been deepened by my study of the literature of the 
science and a growing knowledge of the many processes to 
which it has given birth. 

Some few of those processes I endeavored to explain in my 
former volume. Others of equal interest I have selected for 
description in the following pages. 

I have aimed to select only those methods known to have a 
permanent value. 

If it be objected that some of them no longer have a prac- 
tical value, let it be remembered that an acquaintance with 
them is necessary to a thorough knowledge and appreciation of 
the enormous advance which photography has made in these 
later years. 

It is folly to neglect the treasures of past experience. 

There is a culture, a completeness of knowledge, in this as 
in other sciences. 

I have endeavored to make this knowledge easy of attain- 
ment by giving a few typical formulae under each of the his- 
torical negative processes. 

The arrangement of the chapters follows the historical or 
chronological order of the development of the negative proc- 
ess, from the calotype of Fox-Talbot to the pellicular film of 
to-day. 

1 make no other claim to originality than is implied in the 
selection and arrangement of the material at my command. 
The appended list of authorities bears abundant witness to my 
indebtedness to better workers in the same field. 

I have sought to make a practical book, valuable alike to the 
amateur and to the professional, and I bespeak for my effort 
the kindly criticism which well-meant striving always merits. 



To Dr. Charles Ehrmann and W. I. Lincoln Adams, of the 
Photographic Times, my thanks are due, as well for the 
warm interest which they have shown in the work, as for the 
valuable advice and assistance they have freely given. 

It is with a feeling of regret that I bring to a close a task 
which has been full of pleasure and profit, and one which I 
trust may have a genuine, though, perhaps, a small value to 
my brother photographers, to whom I respectfully dedicate 
my work. 

R&v. W. H. Burbank. 

NEWBUKG, N. Y., February, 1888. 






LIST OF PHOTOGRAPHIC WORKS CONSULTED. 

ABNEY, CAPT. W. DE W. Photography with Emulsions. Scovill Mfg. 
Co., N. Y. 1886. 

ABNEY, CAPT. W. DE W. A Treatise on Photography. D. Appleton & 
Co., N. Y. 1878. 

BOIVIN, E. Procede au Collodion Sec. Gauthier-Villars, Paris. 1883. 

DAVANNE, A. La Photographic. Gauthier-Villars, Paris. 1886. 

DAVID and SCOLIK. Die Photographic mit Brom-Silber Gelatine. Hart- 
leben, Wien. 

EDER, J. M. Modern Dry Plates. E. & H. T. Anthony & Co., N. Y. 
1881. 

HARDWICH, REV. T. F. A Manual of Photographic Chemistry. Scovill 
Mfg. Co., N. Y. 1886. 

HUBERSON, G. Precis de Microphotographie. Gauthier-Villars, Paris. 
1879. 

LIESEGANG, PAUL. Die Collodion-Verfahren. Ed. Liesegang. Diissel- 
dorf. 

MALLMANN and SCOLIK. Mittheilungen. 

MARTIN, A. Handbuch der Gesammten Photographic. Wien. 1854. 

PELEGRY, ARSENE. La Photographic des Peintres, des Voyageurs, et des 
Touristes. Gauthier-Villars, Paris. 1885. 

PIERRE PETIT FILS, A. La Photographic Industrielle. Gauthier-Villars, 
Paris. 1887. 

Roux, V. Traite Pratique de la Transformation des Negatives en Posi- 
tives. Gauthier-Villars, Paris. 1881. 

TISSANDIER, G. A History and Handbook of Photography. Scovill 
Mfg. Co., N. Y. 1877. 

TRUTAT, E. Traite Pratique de Photographic sur Papier Negatif. Gau- 
thier-Villars, Paris. 1884. 

VIALLANES, H. La Photographic Appliquee aux Etudes d'Anatomie 
Microscopique. Gauthier-Villars, Paris. 1886. 

VOGEL, H. W. Progress in Photography. Edward L. Wilson, Philadel- 
phia. 1883. 

VOGEL, H. W. Handbook of the Art and Practice of Photography. 
Benerman & Wilson, Philadelphia. . 1871. 

VOGEL, H. W. Die Photographic Farbiger Gegenstande. Oppenheim, 
Berlin. 1885. 

WILSON, E. L. Photographies. E. L. Wilson, Philadelphia. 1883. 

WILSOX, E. L. Quarter Century in Photography. E. L. Wilson, New 
York. 1887. ~ 

Valuable information has also been derived from the British Photo- 
graphic Annuals, from the American Annual of Photography for 1887, 
and from the columns of The Photographic Times and other American and 
foreign photographic journals. 



CHAPTER I. 

GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 

IT is proposed in this chapter to give a brief statement of 
the nature of the various sensitive compounds in most com- 
mon use in photography, followed by brief notes on the ma- 
nipulations common to all negative methods described in sub- 
sequent chapters. 

Substances Sensitive to Light. The number of substances 
which are sensitive to the action of light is infinite. There is 
reason to believe that there is no substance which is not more 
or less changed in outward appearance or in internal struc- 
ture by the continued action of light. 

But while this is true, thus far but three compounds have 
come into general use for the production of photographic 
negatives ; these are the iodide, the bromide, and the chloride 
of silver ; and more rarely, the fluoride of silver. These prod- 
ucts of double decomposition are very far from possessing 
equal value in negative work. 

The bromide of silver is the one of the three compounds 
which most perfectly meets all the requirements demanded by 
the varying needs of the photographer, which are that the 
result due to the action of light shall be effected as speedily as 
possible, that the tone values of different colors shall be repro- 
duced on the plate as they are on the retina, and that the 
quantities of light which give the impression of high lights, 
half-tones, and shadows shall produce the same effect on the 
sensitive surface that they produce on the human eye. 

As the result of much experiment and investigation, it has 
been found that while the iodide and the chloride possess one 
or more of these qualities in a higher degree than the bromide, 
the latter is superior to the others in that it meets fairly well 



8 THE PHOTOGRAPHIC NEGATIVE. 

all the requirements. It is more sensitive, and gives a better 
rendering to half-tones than either of the others. For certain 
purposes, however, the iodide or the chloride may be advan- 
tageously substituted for the bromide, or combined with it. 
For the reproduction of plans, engravings, designs, etc., in 
line work, the iodide is superior to either of the others. 

The chloride, owing to its comparative slowness, is but little 
used in negative work, but is invaluable for the production of 
positives on glass. 

The fluoride of silver has been recommended by Obernet- 
ter and Yogel for orthochromatic plates. 

Many formulae are based on the combination in different 
proportions of the iodide and bromide, and, less often, the 
chloride, in order that the excellencies of one may counter- 
balance the defects of the others. 

No difficulty will be experienced in effecting this combina- 
tion if care be taken to have the amount of silver at least equal 
to the total of the combining weights of the salts. 

The necessity for this is based on the law of chemical affin- 
ity. The iodides, bromides, and chlorides differ in the order 
named in their affinity for nitrate of silver. If a solution of 
nitrate silver be added gradually to a solution containing an 
iodide, a bromide, and a chloride, the iodide of silver will be 
formed first ; next, the bromide of silver after all the soluble 
iodide has been converted, and after the conversion of the 
bromide, the chloride is fonned. 

So powerful is the law of affinity governing these combina- 
tions, that the precipitates formed will be decomposed, if 
necessary, to satisfy it. 

If sufficient of a solution of chloride of sodium has been 
added to a solution of nitrate of silver to convert all the 
nitrate into the chloride, the latter will be decomposed and 
transformed into the bromide of silver, if a bromide solution 
is added, which in turn will be changed into the iodide of sil- 
ver on the addition of an iodide solution. 

The Film. Owing to the impossibility of spreading the 
sensitive salt of silver formed by double decomposition when 
an iodide, a bromide, or a chloride solution is poured into a 



GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 

solution of nitrate of silver, directly upon the glass, and of 
holding it there during all the manipulations necessary to the 
production of the finished negative, it was found necessary to 
incorporate the sensitive salts with other substances capable of 
giving the glass support a regular, continuous, and adhering 
surface. 

Many important considerations govern the choice of these 
substances. They must be capable of liquefaction in order that 
they may be easily and quickly spread upon the glass or other 
support ; they must have the property of setting, or hardening 
on the support ; they must be or become insoluble in the suc- 
cessive baths through which they must be passed ; they must 
be easily permeated by the various reagents to whose action 
they will be submitted, and they must have no injurious effect 
upon the sensitive salts. 

The result of patient and laborious investigation long- 
continued has narrowed the list of suitable substances down to 
three : albumen, collodion, and gelatine, given here in the 
order of their introduction. Each of these has given its name 
to a group of processes, the best of which will be described in 
later chapters. 

At this point it is sufficient to say that each of these sub- 
stances has its merits and its defects. Albumen gives films to 
the finest grain, but of great tenuity. It must be coagulated 
by a strong nitrate bath, which lessens its permeability, and 
thus lengthens the time of exposure. Collodion films set 
very rapidly, owing to the evaporation of the solvents ; they 
are easily permeated by the various photographic reagents ; 
they are easy and economical of production, and while they do 
not always unite great sensitiveness with good keeping quali- 
ties, they unquestionably yield negatives of irreproachable print- 
ing qualities, superior in many respects to those produced on 
the modern gelatine plates. 

The collodion process has too many points of excellence to 
be finally superseded by any rival methods, although at present 
it may seem to be in abeyance, owing to the great popularity 
enjoyed by gelatine emulsion plates. Gelatine gives quickly- 
setting, highly-sensitive films, which retain their good quali- 



10 THE PHOTOGRAPHIC NEGATIVE. 

ties for an indefinite period, and which are easily acted upon 
by the reagents, and notwithstanding some drawbacks, gelatine 
has usurped the place once held by collodion in the photo- 
graphic laboratory. 

The Dark-room and Laboratory. The convenience and 
comfort of the photographer will be greatly enhanced by the 
arrangement of the room or rooms in which his work is 
done. The dark-room in which the sensitive surfaces are 
prepared and developed may be of any size within reach of 
the operator; it must be lighted in such a way as to 
enable him to see what he is doing without the light ex- 
erting any injurious effect upon the preparations. Experi- 
ment has shown that the red end of the spectrum has least in- 
fluence upon iodide and bromide of silver ; therefore a light 
varying from orange to red or ruby is in common use. 

It must be borne in mind that no light is absolutely non- 
actinic, that is, without reducing power on salts of silver ; the 
only difference between rays of different colors being the 
length of time required to effect the reduction. The orange- 
red end of the spectrum being the slowest in its action, some 
one of these colors, or a combination of them, is used for dark- 
room illumination. 

For albumen, collodion, and slow gelatine plates yellow light 
is safe; for highly sensitive gelatine plates a ruby or a green- 
ish-yellow light must be used, and the plate exposed to its ac- 
tion as little as possible. For orthochromatic plates, which are 
made highly sensitive to the yellow and red rays, the smallest 
possible amount of illumination is necessary, and the plates 
must be most carefully guarded from the direct rays. Schu- 
man, Eder, and others use a screen made of three thicknesses 
of brown tissue-paper. This gives a pleasant and safe light, 
which is especially recommended for color-sensitive or ortho- 
chromatic plates. 

The source of light may be gas, oil, electricity, or the sun, 
according to the taste of the operator ; it may be inside or out- 
side the dark-room, as preferred. My own preference is for 
an oil or gas light outside the rooms. An opening of conven- 
ient size, shape, and position is cut in one of the walls of the 



GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 



11 



dark-room ; this is provided with sliding frames carrying re- 
spectively a ground glass, a yellow, a green, and a ruby glass ; 
a curtain is arranged to slide back and forth behind these 
frames, and a shade is hinged to the wall above. This com- 
bination of arrangements seems to give all the necessary modi- 
fications, and the changes are quickly and easily made. 

The size and internal fittings of the dark-room will vary to 
suit the convenience of the operator, and the amount and kind 
of work to be done in it. If the room is used only for devel- 
opment it need not be larger than six by eight feet. If it is 
to be used as well for the preparation of plates it must neces- 
sarily be larger ; nine by twelve feet will be a convenient size 
for a room of this description. 

For the guidance of those who may wish to fit up such a 
room the following diagram and description is given : 



9ft. 



FIG. 1. 



A, is a broad shelf at which the coating of thejplates is done. 
On it is the levelled slab used to hasten the setting of gelatine 
plates, and above are shelves containing the various chemicals, 
vessels, and utensils used in the preparation of the sensitive 
compounds. B, immediately facing the window, is the devel- 
oping shelf. It inclines slightly toward the sink E, and is 
covered with sheet lead. Above it on suitable shelves are 
stored the developing solutions and chemicals. The space un- 
derneath is divided into vertical compartments to hold the 



12 



THE PHOTOGRAPHIC NEGATIVE. 



various sized trays used for development. C, is a shelf run- 
ning across the room. The end nearest the sink is used for 
fixing, and here are kept all fixing solutions and trays. D, is 
the drying-box, and F, is a light-tight closet for the storage of 
plates, sensitive paper, etc. 

The double door arrangement shown in the cut is a great 
convenience, allowing ingress or egress without the necessity 
of covering the plates to prevent them from being light-struck. 

The open space in the middle of the room is large enough 
to be utilized for enlarging purposes. The wall space above 
and below the shelves shown in the cut may be fitted up to 
suit special needs. The room is ventilated by boring holes at 
the top and bottom of one side and covering them in such a 
way as to prevent the ingress of light. The method shown in 
the cut below is simple and effective. 



JL 



J 



FIG. 2. 

Cleanliness will be greatly promoted by covering the floor 
with oil cloth ; this is easily cleaned and can be renewed when 
worn out. 

Such a room as this would seem to meet all the requirements 
of the professional or amateur photographer, especially if a good 
supply of running water can be laid on. In default of this, a 
large tank can be fastened to the wall above the sink and fitted 
with a tap. 

The Drying-Box. Many photographic processes, both 
negative and positive, require a place in which the sensitive 



GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 



13 



surfaces can be dried by heat or otherwise, and in which they 
can be protected from light and dust. 




FIG. 3. 

The drying-box shown in Fig. 3 will answer all these needs, 
and it is easy of construction and effective in operation. It 
may be placed in the dark-room, if the coating is done there, 
or elsewhere, to suit the convenience of the workman. 

It is impossible to give any very definite dimensions, as 
these vary according to individual needs. A convenient size 
for the amateur workman is three feet high, two feet wide, 
and one foot deep from back to front. The box is divided 
into two unequal sized compartments, each closed by a door 
fitted light-tight. The upper portion, which occupies about 
three-fourths of the box, is the drying space proper, and is 
fitted as shown with notched side pieces to allow easy displace- 
ment of the shelves. The bottom is a moderately thick piece 
of sheet iron, accurately and tightly fitted to the sides of the 
box, to prevent the escape of gas into the drying chamber. In. 



14: THE PHOTOGRAPHIC NEGATIVE. 

one corner of this plate a hole is cut to take the ventilating- 
pipe, which passes through the back and is there again bent 
at right angles. A second pipe, also bent, leading from the 
top of the box, serves in connection with the first to establish 
a current of air. If it is necessary to dry the sensitive surfaces 
by hot air, the source of heat is placed in the lower compart- 
ment, immediately under the iron plate. If a current of cold 
air is desired, a lamp 6r gas jet is placed in the upper pipe. 
When not in use as a drying-box, it can be used for other pur- 
poses. Wood may be used in its construction in place of 
metal, but the danger of fire is increased. 

This is the box recommended by M. Davanne, who also 
gives the following method for drying the plates vertically. 




FIG. 4. 

As shown by the cut, Fig. 4, the racking arrangement con- 
sists of three bars of wood placed side by side on the movable 
ledges of the drying-box. The middle bar, which is one-quar- 
ter of an inch thinner than the two side bars, is provided with 
a series of vertical rods placed about four inches apart ; they 
are about six inches high, and of sufficient size to prevent 
bending or shaking. Between these bars pieces of glass rods, 
one-half an inch high, are fixed. With this arrangement two 
plates can be placed between the rods. If it is preferred, the 
glass rods can be dispensed with, and the wooden uprights 
brought nearer together, but one plate can then be placed 
against each upright. The side bars are one-quarter of an inch 
higher than the middle one. Their two upper surfaces are 



GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 



15 



beveled off, and glass rods are fitted into grooves cut in the 
tops of each. The plates rest on these rods, which are easily 
cleaned after each operation of drying. 

When paper coated with emulsion is to be dried in this box, 
it is only necessary to remove the middle bar, and to pin the 
paper to the two side bars. 




FIG. 5. 



-6 6 


jl 


m i 

3 i 


B 


-3 E 

4i i 

c c 




^__D 




FIG. 6. 






l> 66 



WJ^ 



FIG. 7. 




FIG. 8. 




FIG 



Figures 5, 6, 7, 8, and 9, illustrate the details of the con- 
struction of a more elaborate drying-box, of German origin, I 
believe. Fig. 5, is a general plan of the framework, showing 
the sliding door. Fig. 6, shows the ventilating arrangements 
from the front ; Fig. 7, is a side view ; Fig. 8, the bottom plan, 
and Fig. 9 the cut-off for excluding light from the interior. 
Dust is excluded by a strip of muslin glued over the opening 
of the cut-off. 

D, Figures 6, 7, and 8, is a sheet-iron box, six inches deep, 
fastened to the bottom of the drying-box, projecting far 



16 THE PHOTOGRAPHIC NEGATIVE. 

enough beyond the back, to allow the insertion of the six-inch 
pipe, E, Figures 6, 7, and 8. On the inside are riveted two 
pieces of sheet iron, four and one-half inches wide, and passing 
completely across. C, C, Figures 6, 7, and 8, are pieces of two- 
inch iron pipe, four inches long, projecting into the box, D, 
and opening into the drying chamber, F. Figure 7, is a gas 
jet, which, burning inside the pipe, E, produces the current. 
K, Figure 7, is a door in the pipe, which allows the height of 
the flame to be seen. In default of gas, an oil lamp can be 
used, supporting it on angle-irons riveted inside the pipe. 
The shelving arrangements can be made to suit the fancy of 
the operator. Tbe framework is of wood, the sides may be of 
wood, sheet iron, or zinc, as desired. 

If the coating-room is dry, well ventilated, free from dust, 
and light-tight, the plates may be racked away on shelves 
placed near the top of the room to dry spontaneously. This 
is my own practice, and I prefer it to the most elaborate dry- 
ing-boxes, which do not always dry well. 

Utensils. It is manifestly impossible to give a complete in- 
ventory of all the various glasses, graduates, and other para- 
phernalia which accumulate in and about the photographic 
work- shop. Some pride themselves on doing all their work 
with the fewest possible conveniences ; while others must have 
an infinite number of belongings before setting to work. The 
list which is here given is intended to cover everything really 
needed in the performance of all the processes included in 
these pages. If the list seems a long one it must be re- 
membered that the number of negative processes is large, 
and that all of them have special requirements in the way of 
apparatus. 

For development a number of flat trays of different sizes 
will be needed. These may be of glass, porcelain, gutta 
percha, japanned iron, wood, or even pasteboard in an emer- 
gency. Glass and porcelain are the cleanliest, and must have 
the preference for regular work in the dark-room. 

For the chemicals nothing can be better than the wide- 
mouthed glass-stoppered bottles used by druggists. 

For mixing solutions the cylindrical glasses known as beak- 



GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 



17 



ers are well adapted, and a number of these of different 
capacities should be provided, together with a goodly number 
of glass stirring-rods. Graduates of different sizes are a 
necessity; test tubes, pipettes, porcelain capsules for heating 
liquids, a glass mortar and pestle, specific gravity glasses for de- 
termining the specific gravity of liquids, glass funnels of various 
sizes, Bohemian glasses of various shapes and sizes for emulsion 
making, a retort stand, a Bunsen gas burner, or a Liebig spirit 
lamp, a retort or two, a hot-water bath, two or three drying 
racks, a washing box, a distilling arrangement, and an apparatus 
for hot filtration will well stock the photographic laboratory. 
Not all of them need be kept in the dark-room. Most of them 
should be kept in a room set apart for such operations as do 
not shun the light of day ; a working laboratory in fact, which 
may be fitted up to suit the inclination and purse of the ex- 
perimenter. It should have a sink, an abundant supply of 
water, a strong work table, with a stone or marble top, and a 
draining rack where the various glass bottles, etc., may be put 




FIG. 10. 

to drain and dry after washing. Such a rack is shown in Fig. 
10, and its use is sufficiently apparent to need no further de- 
scription. 



18 THE PHOTOGRAPHIC NEGATIVE. 

Solutions. The photographer uses all his chemicals in the 
form of solutions. The- most common method of making a 
solution is to weigh out the proper amount of the chemical 
required, throw it into the bottom of a bottle, add the proper 
quantity of water, and then leave it to take care of itself. 
This is the simplest method and the poorest. It produces a 
local saturation of the lower portion of the liquid, and in a 
short time the process of solution ceases entirely. A better 
way is to pulverize the chemical before adding the water, and 
to assist the solvent action by frequent stirrings. The best 
way is to keep the chemical near the surface of the liquid, or 
even above it. This hastens solution, because the liquid in 
contact with the chemical is continually being replaced as the 
heavier saturated portion falls to the bottom. Two methods 
may be adopted to effect this result ; one is to pour the liquid 
into a wide-mouthed bottle and to suspend the chemical in a 
bag, so that it is just covered ; another way, and the more 
scientific, is shown in Fig. 11. A gutta-percha 
tube fitting tightly into the mouth of a flask is 
forced tightly over the tube of a funnel to pro- 
duce an air-tight joint. Two-thirds of the liquid 
is poured into the flask, the remaining third and 
the chemical to be dissolved are placed in the 
funnel and the mouth of the flask is hermetically 
sealed by forcing the rubber tube into it. The 
lower end of the tube must be below the surface 
of the liquid. As the air cannot escape, and the 
heavier saturated liquid must descend, two cur- 
rents are soon established in the tube, one de- 
scending, bearing the saturated liquid, the other 
ascending, bearing fresh portions. The operation 
is automatic and speedy. If the filtered solution 
is wanted it is only necessary to place a filter 
paper in the funnel. A saturated solution is 
FIG. 11. made by placing in the funnel an excess of the 
substance to be dissolved. 

Filtration. To produce clean work in photography all 
solutions must be filtered. The means of doing this with or- 




GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 



19 



dinary aqueous solutions are too well known to need descrip- 
tion. Solutions containing gelatine, gum, and similar sub- 
stances, as a rule need to 
be kept warm during fil- 
tration to prevent them 
from cooling down and 
filling the pores of the 
paper. Two very effect- 
ive systems of warm fil- 
tration are shown in Figs. 
12 and 13. In both the 
inner glass funnel is tight- 
ly fitted to the outer one 
of tin by means of a 
pierced cork. Warm 
water is poured into the 
outer funnel and its tem- 
perature maintained by a 
spirit, gas, or oil lamp. 
Upward filtration will 

FIG 12. 

be found a valuable 
method for filtering 
emulsions of any 
kind, as bubbles are 
entirely prevented. 
One or more thick- 
nesses of muslin, ac- 
cording to its fineness, 
are tied over the 
mouth of a beaker or 
other glass, the bot- 
tom of which has been , 
removed. The emul- 
sion is placed in a ves- 
sel a trifle larger than the filter, which is allowed to sink by 
its own weight. When full it is withdrawn and the emul- 





20 THE PHOTOGRAPHIC NEGATIVE. 

eion poured out. The dish containing the emulsion should be 
placed in a hot water bath. 

In case of need the ordinary filter paper may be replaced 
with glass, as in the case of strong acid or alkaline solutions, 
which might attack the paper, or with filtering cotton, or a 
piece of chamois skin previously well soaked in a sal soda solu- 
tion and well washed for collodion or gelatine emulsion. 
Flaxen tow is also sometimes used for this purpose. 

Precipitation. The term precipitates is applied to the in- 
soluble substances which are formed in a solution, when by a 
change in the nature of the substance held in solution or in 
the solvent, insoluble and non-crystalline bodies are formed. 
Precipitation is resorted to to obtain certain substances or fluids 
difficult or impossible to be had in any other way. The liquid 
and the precipitate are first separated by filtration, and then 
the precipitate, if wanted, is freed from impurities by washing. 
Washing Precipitates. Precipitates are commonly washed 
on filter paper, small quantities of water being poured into 
the filter until the drainings when treated with the proper 
reagents,show no traces of the dissolved substances from which 
the precipitate has been formed. 

Another method is to use the washing 
bottle of the chemist, shown in Fig. 1 4. 

A, and B, are two glass tubes bent as 
shown, and tightly fitted into the cork 
which closes the mouth of the bottle. 
The precipitate is placed in the bottle, 
which is then partly filled with water ; 
the cork is then inserted, and by blow- 
ing through B, a stream of water is 
forced through A, the upper end of 
which is drawn out somewhat to diminish 
the size of the bore. 

Decantation. When the precipitates are coarse grained 
and heavy they may be easily and quickly washed by decanta- 
tion. The precipitate is placed in a large beaker or tumbler, 
which is then filled with water, and the contents well stirred 
with a glass rod. As soon as the precipitate has fallen to the 




GENERAL REMARKS ON SENSITIVE SURFACES, ETC. 



21 



bottom the water is carefully poured off as closely as possible. 
This operation is repeated ten or more times, and the precipi- 
tate is then thrown on a filter and allowed to drain. 

The use of a decantation flask will greatly facilitate the 
operation. This is a flask provided with two tubes, a large 
and a small one. A piece of fine muslin is tied over the 
mouth of the smaller tube, the water and the precipitate are 
introduced through the larger. The water is poured away 
through the smaller tube. 

Distilling Apparatus. Many photographic operations re- 
quire distilled water to secure the best results; it would be 
well to use nothing else in making up solutions. The use of 
distilled water would probably be more general were it not for 
the high price and great bulk of the ordinary worm still. 
Pig. 15 illustrates a simple form of a portable still which is 
open to neither of these objections. It can be easily and 
cheaply constructed by any tinman ; it is effective in operation 
and easily kept clean. The dimensions given below will give 
a still capable of distilling a gallon of water at a time. It is 
made of stout tin or copper, as preferred. The cylindrical 




FIG. 15. 



body, A, is thirteen inches high and seven inches in diameter. 
The funnel-shaped lid, B, is eight and a half inches in diam- 
eter and five inches in height from base to apex. It is pro- 
vided with a flange, 0, C, to fit accurately inside the cylinder 



22 THE PHOTOGRAPHIC NEGATIVE. 

like an ordinary pail cover, and a tube, D, a couple of inches 
long, near the top of the cone. About five inches from the 
top of the body a tube, E, about ten inches long, is passed 
through, terminating at the inside in a small funnel, F, exactly 
under the tip of the cone. The other end projects about three 
inches at the outside of the cylinder. The three legs, made of 
strap iron, are riveted to the body, and may be of any conven- 
ient length. 

Common tap water is poured into the cylinder, the cone lid 
is put in place, and the apparatus is placed over a gas or oil 
stove near the water supply. A gentle stream of running 
water is led into the cone by a piece of rubber tubing. The 
steam produced from the boiling water is condensed on the 
under side of the cone, and runs down into the funnel and 
tube, and is caught in a flask placed underneath the pipe. 
This still is the invention of Mr. C. C. Vevers, of England, 
the description being given nearly in his own words. 

If running water cannot be had the cone can be occa- 
sionally replenished with cold water from a pail, or small 
lumps of ice can be thrown in now and then to keep the water 
cool. 




CHAFTEE II. 

PRELIMINARY REMARKS ON EXPOSURE, DEVELOPMENT, FIXING, ETC. 

IT will serve to pave the way to the more practical discus- 
sion of the manipulations peculiar to the different negative 
processes if a few pages are devoted to the general principles 
common to all. 

The production of a negative by any of the methods, de- 
scribed later, requires an exposure to light more or less pro- 
longed, followed by development, fixing, washing, and in 
many cases a strengthening or weakening of the image pro- 
duced by development. While each of these manipulations 
has special modifications to adapt it to the different pro- 
cesses, they all agree in certain broad and general principles, - 
the knowledge of which is essential to that complete mastery 
of the subject without which the operator will be continually 
working in the dark. 

These general principles will be discussed in this chapter, 
leaving their application to special cases to be explained 
later on. 

Exposure. Whenever a ray of light falls upon a sensitive 
surface a change of some kind is produced. Of the precise 
nature of this change we, at present, know but very little, and 
where little is known, little had best be said. We do know, how- 
ever, that this change, invisible to the eye, can be made visible 
by the application of certain reagents to the exposed surface. 
The latent image then shows itself with a perfection and de- 
tail proportioned to the duration of the exposure and the 
strength of the reagent. The behavior of the exposed surface 
in the developer is to some extent a means of determining the 
correctness of the exposure. If the image appears suddenly 
in #11 its details and then as suddenly clouds over, we know 



24: -THE- PHOTOGRAPHIC NEGATIVE. 

the exposure was too prolonged. If the image comes up slow- 
ly and is poor in detail, the exposure was not sufficient. In 
neither of these cases will a geod negative be produced. 

A good printing negative is one in which the high lights 
show points of opacity, and the deepest shadows almost bare 
glass, with an infinite gradation of tones between these two 
extremes. Such a negative is largely the product of correct 
exposure. Much may be done in development to make 
amends for a faulty exposure, but the best technical negative 
will always be the properly exposed and rightly developed 
one. 

Beyond question the time of exposure is one of the most 
important of photographic manipulations, and even with a 
careful study of all the facts which determine its length, 
aided by much experience, it is only possible to acquire an 
approximately correct judgment. 

Three different sets of facts must be considered in this con- 
nection ; viz., the physical, chemical, and optical conditions 
present and influencing the duration of the exposure. 

The physical conditions are such as the following: the 
nature, intensity, and color of the light, and the distance, 
color, and lighting of the object to be reproduced. These 
the view photographer has little or no power to change. He 
must take them as he finds them, and rely on his own judg- 
ment as to the time of exposure best suited to the view before 
him. 

Despite many ingenious attempts, no mechanical means of 
settling the question have as yet been discovered of sufficient 
accuracy to take the place of long experience and good judg- 
ment. The simplest are based on the darkening action of 
light on sensitive paper confined in a box and exposed through 
a narrow slit cut in its cover. The best and most accurate 
require too much scientific knowledge to be generally useful, 
and none give anything more than a relative estimate of the 
intensity of the light. 

The chemical conditions depend on the method employed 
in making the sensitive compound; sensitiveness increasing in 
the following order : albumen, calotype, collodio-albumen, 



PRELIMINARY REMARKS ON EXPOSURE, ETC. 25 

dry collodion, wet collodion, gelatino-bromide. The compar- 
ative rapidity of each is approximately given in the following 
table : 

Albumen 10 to 30 minutes 

Calotype 8 to 20 minutes 

Collodio-Albumen 3 to 10 minutes 

Dry Collodion - 1 to 5 minutes 

Wet Collodion 5 to 60 seconds 

Gelatino-Bromide 1 to 10 seconds 

These figures represent average results with emulsions or 
preparations of medium sensitiveness in each class. 

The optical conditions influencing the exposure are the 
focal length of the objective, the size of the diaphragm, the 
number, thickness, and degree of coloration of the lenses, and 
the distance from the view. 

These conditions are subject to one or more of the following 



1. The time of exposure varies directly as the focal lengths 
of the objectives. 

2. The time of exposure is inversely proportioned to the 
squares of the diameters of the diaphragms. 

3. The time of exposure varies inversely as the distances of 
the objects to be photographed. To this law is due the repro- 
duction of the effect known as aerial perspective. 

Development. To the eye, and even to the microscope, an 
exposed plate shows nothing to distinguish it from an unex- 
posed one. The developer alone detects the difference, with- 
out, however, conveying any information as to the nature of 
the change. 

Notwithstanding much patient investigation the question of 
the nature of the latent image is still an unsettled one. The 
most commonly accepted theory is that a molecular change is 
produced by the action of light upon sensitive compounds, the 
molecules being pulled apart, as it were, and so made less 
stable. 

This molecular change is not supposed to produce any sep- 
aration of elements, such as occurs when a visible image is 
formed by the action of light. 



26 THE PHOTOGRAPHIC NEGATIVE. 

The function of a developer is to make this change visible 
by reducing the silver in those parts acted upon by light to the 
metallic state. 

It has long been a disputed question among photographic 
savants whether the change produced in a sensitive com- 
pound of silver is a physical or a chemical change. With- 
out burdening the reader with the arguments advanced in sup- 
port of each of these positions, it may be stated that at present 
the weight of authority seems to be on the side of a chemical 
change. 

It may be regarded as a tolerably certain fact that under the 
action of light the haloid salts of silver, that is, the bromide, 
iodide and chloride, have a tendency, more or less powerful, to 
return to the metallic state; a tendency which is promoted and 
made permanent by the action of developers, which are al- 
ways reducing agents ; that is, they are substances which are 
able to reduce the soluble salts of silver to the metallic state. 
We may thus take it for granted, for the present at least, that 
the change of condition produced in the sensitive compounds 
employed for the production of negatives is a chemical, not a 
physical reaction. 

The development of negatives may be eifected in one of two 
ways: 

1st Method. The new compound may possess an attractive 
force. The action of light on sensitive compounds of silver 
tends to cause the formation of a substance capable of attract- 
ing the metal of which it is a salt, when slowly deposited from 
a solution. This first deposit is capable of attracting more of 
the metal, and in this way an image is gradually built up. 
This is the theory of the physical development of wet collodion 
plates. 

2d Method. The image may be the result of the reduction,, 
more or less complete, to a more elementary state, of the altered 
compound when treated with certain solutions; in which state 
it may have the same attractive power as before. This is the 
rationale of all alkaline development. 

The proper development of a negative is an art acquired 
only after long experience and many failures. It cannot be 



PRELIMINARY REMARKS ON EXPOSURE, ETC. 27 

learned from books ; it must be acquired at the developing 
table. The problem to be solved is to bring forth on the ex- 
posed surface a reproduction of the original which shall pre- 
serve all the varied tones, and be capable of reproducing in the 
print the impression made by the original. 

As a first step towards the solution of this problem it is 
best to begin with a weak developer, strengthening it 1 as need 
arises. This gives more control of the reducing action by 
which the image is built up, and gives the operator time to see 
and meet the needs of each case. This method is particularly 
desirable with instantaneous exposures. Here a strong devel- 
oper would probably ruin the plate, burying the high lights be- 
neath an opaque deposit of metallic silver long before any detail 
was visible in the shadows. It is always best to make sure of 
the details before securing density. The latter is always possible 
at any stage of development, while if the proper degree of 
density is reached before the details are well out, the plate will 
be lacking in that exquisite gradation of tone which makes the 
charm of a perfect negative. 

The common practice is to keep the developer in constant 
motion, in order to renew the portion in contact with the plate, 
and so secure uniformity of action. 

Many operators, however, claim that finer details are secured 
by allowing the plate to remain undisturbed. In the case of 
pyro development there is less danger of the film becoming 
stained by the oxidization of the pyro. 

When prolonged development is necessary, it is best to turn 
the plate face down in the developer, supporting it by the 
extreme edges in such a way as to leave a fair depth of the 
solution between the plate and the bottom of the tray. 

When the development is very rapid, as with wet collodion 
plates developed with protosulphate of iron, the plate is to be 
held in the hand and as much developer as the plate will hold 
poured on and allowed to act until the process of develop- 
ment is completed. 

If the latent image flashes up at once under the action of 
the developer, the exposure was too great. If, however, the 
high-lights only appear, the half-tones hanging back, the ex- 



28 THE PHOTOGRAPHIC NEGATIVE. 

posure was too short. Both of these errors can be corrected, 
to a certain extent, by certain modifications of the developer. 

Development must be continued until the proper degree of 
density is reached, generally until the image is faintly visible 
at the back of the plate. Viewed by transmitted light the 
highest lights should be nearly opaque, and the gradations be- 
tween the shadows, the half-tones, and the high-lights should 
be well marked and distinct. 

After development, the plate is washed in several changes 
of water and then fixed. 

Fixing. The office of the fixing-bath is to dissolve out all 
the silver salts not converted to the metallic state by the devel- 
oper. If this were not done, and the unfixed plate were exposed 
to the action of light, the surface of the plate would assume a 
uniformly dark tint and the image would be lost. 

There are many substances which possess this power of dis- 
solving the salts of silver, but only three of them are of use in 
photography; these are the alkaline sulphocyanides (potassi- 
um or ammonium), the cyanide of potassium and the thio- 
sulphate of soda, commonly known as hyposulphite of sodium. 
The chemical action of all these compounds is practically the 
same. In conjunction with the salts of silver they form re- 
spectively the sulphocyanide, the cyanide, and the hyposul- 
phite of silver, all of which are insoluble in water, but soluble 
in an excess of alkaline sulphocyanide, cyanide, or hyposul- 
phite. Hence the necessity of employing an excess of the fix- 
ing agent. 

The sulphocyanide and the cyanide fixing-baths are but 
little used ; the former on account of its cost, the latter be- 
cause of its exceedingly poisonous nature. 

Hyposulphite of soda is cheap, harmless, and effective ; its 
sole drawback being the difficulty of eliminating it entirely 
from the negative, without which perfect elimination the keep- 
ing qualities of the negative are greatly lessened. 

The effect of the fixing-bath is to deprive the negative of 
its milky appearance due to the unreduced silver. This it 
does by dissolving the unreduced salts, but in so doing the ex- 
ceedingly unstable compound known as hyposulphite of silver 



PRELIMINARY REMARKS ON EXPOSURE, ETC. 29 

is formed. This is a white substance which rapidly decom- 
poses into black sulphide of silver. The decomposition does 
not take place in an excess of hyposulphite of soda ; in this 
case double salts are formed and rapidly dissolved. The quan- 
tity of the hypo must then be in excess of the amount actually 
required to dissolve the unreduced salt. 

The fixing action is commonly supposed to be complete 
when the negative has lost its milky appearance. Portions of 
the double salts may still be undissolved, however, and it is 
best to allow the fixing agent to act for a few moments after 
the milky appearance has disappeared. The negative is then 
ready for washing. 

Washing. Hyposulphite of soda has a strong inclination to 
remain in the pores of the film, especially gelatine films. 
These require a thorough washing and a subsequent treatment 
with some hypo eliminator to eliminate the last traces of the 
salt. 

The negative may be washed in ordinary trays in running 
water, or by frequently changing it, but this method requires 
longer washing, as the negative lies in the bottom of the tray 
with its face up, upon which the heavy hypo-charged liquid 
rests. Another method is to place the negatives in washing 
boxes provided with grooves, and then wash in running water. 
The most effective method is to place the negatives film side 
down in a triangular box provided with a stop cock at one 
end, and to wash in running water or with frequent changes. 
The hypo as it leaves the film falls to the bottom of the tray 
and is drawn off through the stop cock. Negatives washed 
for twenty minutes in running water in this box show no 
traces of hypo even to the most delicate tests. 

Whatever method of washing is adopted it is always safe to 
test for hypo, which may be done in several ways, as shown 
later on. After sufficient washing, the negatives, if on gelatine 
films, may be soaked for a short time in a strong alum bath 
to harden the film. They are then washed a few moments 
longer, and after the faces have been brushed over with a 
broad carnePs-hair brush to remove all adhering particles, 
they are racked away to dry in a place free from dust. 



30 THE PHOTOGRAPHIC NEGATIVE. 

When dry, proofs are taken to determine if the negative 
needs any further treatment in the way of strengthening, re- 
ducing, or local touching up before being varnished. 

Intensification. It often happens that the negative through 
over-exposure or under-development lacks sufficient density to 
give good prints. In such cases it must be strengthened or 
intensified. This is done by causing the negative to take a 
deposit of some chemical substance in order to produce greater 
thickness of the lines. Intensifies differ according to the na- 
ture of the sensitive surface. With albumen and collodion the 
most common intensifier consists of a mixture of gallic and 
pyrogallic acids and nitrate of silver strongly acidified with 
acetic acid. For gelatine films most operators employ a sat- 
urated solution of bichloride of mercury ; this forms the chlo- 
ride of silver and the insoluble proto-chloride of mercury 
which is deposited on the film, causing it to assume a creamy 
tint, which is changed to a brown or black by subsequent 
treatment with a solution of ammonia or sulphite of soda. 
Specific instructions for the use of these and other intensifiers 
will be found under the various processes described. 

Reduction. Over-development is apt to produce hard 
negatives incapable of yielding prints full of soft and delicate 
gradations. Such negatives may often be made fit for use 
by reducing the excessive thickness of the deposit of metallic 
silver. This may be effected by treating the negative with 
solutions of iodide, cyanide, or the perchlorides. These change 
the deposit on the film into the iodide, cyanide, or chloride of 
silver, which are then dissolved in a cyanide or hypo bath. 

Success in this treatment is by no means certain, owing to 
the impossibility of knowing to what extent the metallic silver 
has been converted to the soluble salt until the negative is 
taken from the fixing-bath. Keduction, therefore, is to be re- 
sorted to only in extreme cases. Other methods will be found 
in Chapter XI. 

Varnishing. Collodion negatives must, albumen and gela- 
tine negatives should, be protected from chance of injury by 
flowing over the films a thin coat of varnish. If the negative 
does not require touching up, any good negative varnish will 



PRELIMINARY REMARKS ON EXPOSURE, ETC. 31 

answer. The following is as good as any and is easily made : 
Dissolve pure yellow lac in alcohol in the proportions of 150 
grains of lac to three and a half ounces of alcohol, sp. gr. .83. 
Some days are required to effect solution, during which the 
flask is occasionally shaken. The varnish is then well filtered, 
and is applied to the plate, previously slightly warmed, by 
pouring it upon the plate held in a horizontal position. When 
the plate is well covered the surplus is poured off, and the 
varnish dried by gentle heat, the plate being rocked to pre- 
vent the formation of ridges. 

A good retouching varnish is made as follows : 

Sandarac .1 ounce 

Castor oil 1 dram 

Alcohol 6 ounces 

The sandarac is first dissolved in the alcohol, after which the 
oil is added. 



CHAPTER III. 

(JALOTVPE. 

THIS is the name which Fox Talbot gave to the process by 
which he obtained the first negatives ever made. In this 
process, paper of a fine and even texture, as free from grain as 
possible, is immersed in a bath containing an iodide, and when 
wanted for use is sensitized on a bath of nitrate of silver, and 
then exposed. 

Plain Saxe or Rives paper is immersed in a dilute solution 
of hydrochloric acid, the acid removed by thorough washing, 
and the sheets hung up to dry. As soon as dry they are ready 
to be treated with the silver iodide bath, made as follows : 

No. 1. Silver nitrate 46 grains 

Distilled water 6 drams 

No. 2. Potassium iodide 46 grains 

Distilled water 6 drams 

The silver iodide is formed by pouring No. 2 into No. 1, with 
constant stirring. The iodide falls to the bottom of the beaker 
as a precipitate, which is allowed to settle ; the water is then 
poured off as closely as possible, and the beaker again filled 
and the precipitate well stirred. The operation is repeated 
three or four times to eliminate the bye-product, potassium 
nitrate, which is not wanted. 

The precipitate is then dissolved in the following potassium 
iodide solution : 

Potassium iodide 462 grains 

Water 2J ounces 

This is poured over the precipitate and well stirred. To 
insure complete solution, crystals of the potassium salt are 
added with constant stirring until the solution turns milky. 



CALOTYPE. 33 

The solution is applied to the paper with a Buckle's brush, 
made by inclosing a thin tuft of cotton in the loop of a doubled 
string passed through a bore of a piece of glass tubing six or 
seven inches long. The loop being pulled up into the tube, a 
brush of cotton wool is formed. 

The paper is cut to the proper size and pinned to a flat 
board, and the solution is brushed over its surface, brushing up 
and down and across, to secure an even coating. As soon as 
surface-dry the paper is immersed in a dish of distilled water, 
and after a two-minutes soaking is removed to a second dish, 
and then to* a third ; care must be taken to remove all air 
bells. After two or three hours soaking the potassium iodide 
will be removed. The paper is then hung up to dry, after 
which it may be preserved in any convenient way for future 
use, but as it is somewhat sensitive to light, it is best to store it 
in a dark, dry place. 

When the paper is wanted for use it is sensitized by brush- 
ing over it, first pinning it to the board as before, a mixture of 
the following solutions : 

No. 1. Silver nitrate 77 grains 

Glacial acetic acid 2% drams 

Water 14 drams 

No. 2. Saturated solution of gallic acid in distilled water 

To every dram of No. 1, add 60 drams of distilled water, 
then 1 dram of No. 2, and finally 30 drams of distilled water. 
In warm weather the proportion of water may be still further 
increased to prevent the speedy reduction of silver nitrate, 
owing to the presence of gallic acid. The mixture is well 
stirred and applied plentifully to the surface of the paper. All 
excess of moisture is then blotted off on pure filter paper. The 
paper is most sensitive while moist, but it will give images 
when dry, until the surface of the paper becomes discolored 
owing to the reduction of gallate of silver. 

For exposure the paper may be placed between two pieces 
of glass and inserted in the holder, or if preferred it may be 
gummed by the corners to a glass plate or piece of thick paste- 
board. The time of exposure is long, varying from five to 
twenty minutes. The sensitiveness may be increased by 



34 THE PHOTOGRAPHIC NEGATIVE. 

increasing the proportions of the silver and gallic acid in the 
sensitizing mixture, but the keeping qualities of the prepared 
sheets diminish as their sensitiveness increases. It has been 
noticed that for brilliantly lighted subjects a highly sensitive 
condition gives the best results, while poorly lighted subjects 
require a paper of low sensitiveness to avoid fog. 

Development is effected by pinning the exposed sheets to a 
board and applying the sensitizing mixture given above with 
the brush. As soon as the development seems to flag, the 
gallic acid solution No 2 is applied sparingly until the shadows 
begin to grow dim. 

Under-exposed pictures require more of No. 1. If the iimge 
is fairly visible before development the paper was over ex- 
posed ; in this case more of No. 2 should be added. 
~ The negative is fixed in 

Sodium hyposulphite 15 drams 

Water 35 ounces 

Fixing is complete when the yellowness of the iodide is no 
longer visible by transmitted light. A thorough washing for three 
or four hours in many changes of water is necessary to eliminate 
the hypo. When dry the negative can be printed from as it is, 
but the quality of the prints will be greatly improved by waxing 
the negative. This is readily done by heating a flat-iron hot 
enough to melt white wax, a cake of which substance is 
applied to the iron as it passes over the surface of the paper. 
As soon as the negative is evenly translucent, a sheet of blot- 
ting-paper is laid down upon it and the iron again applied to 
remove all superfluous wax. Care must be taken not to have 
the iron too hot, or the blotting-paper will absorb too much of 
the wax and cause the grain of the paper to become visible. 

The above is a description of the method by which Fox 
Talbot obtained his first negatives, and it is given more as a 
matter of historical interest than because of its practical value. 
The great disadvantage of this and other like methods was the 
rapid deterioration of the sensitized sheets, owing to the com- 
bination of the silver nitrate with the vegetable fibres and the 
sizing of the papers, and also to the formation of a very fugi- 
tive compound of iodo-nitrate of silver. 



CALOTYPE. 35 

Le Gray, in his once famous process, by waxing the paper 
before sensitizing, and by washing away all excess of nitrate, 
greatly increased the keeping qualities of the paper but dimin- 
ished its sensitiveness, and M. Pelegry, a French amateur who 
has given much attention to the process, has of late years still 
further increased the keeping qualities of the paper and has 
also materially decreased the time of exposure. 

LE GRAY'S PKOCESS. 

Waxing. A piece of thick sheet-iron is placed over an oil 
or gas stove and heated up to the melting point of wax. One 
or two sheets of blotting-paper are then placed on the iron, and 
upon these a sheet of the paper to be waxed. This is evenly 
waxed by rubbing it with a piece Qf white wax. A second 
sheet is laid over the one already treated, and waxed as before. 
This operation is continued until a dozen sheets have been im- 
pregnated. The sheets are then separated and again placed on 
the hot iron plate, but with a sheet of unwaxed paper between 
each waxed sheet. The pile is next evenly pressed down with 
a pad of clean blotting-paper, being frequently turned over. 
This process remelts the wax and impregnates the unwaxed 
sheets. If now, on separating the sheets, any of them show 
unwaxed spots, they are to be rewaxed as before, one at a 
time. 

The sheets are best dried by placing them, separately between 
blotting-papers, or two unwaxed sheets, and placing them on 
the warm iron plate. All excess of wax is now easily removed 
by using the pad of blotting paper. Excessive heating of the 
plate must be avoided during this operation, as this will pro- 
duce a grained appearance impossible to remove by rewaxing. 

The iodide lath. 

Whey (serum) 35 ounces 

Iodide of potassium 130 grains 

Bromide of potassium 30 " 

Milk sugar (crystals) 308 " 

NOTE. The whey or serum is produced by boiling 40 to 45 
ounces of milk. As soon as the milk boils acetic acid is added 
drop by drop until the milk is coagulated. The liquid is then 



36 THE PHOTOGRAPHIC NEGATIVE. 

filtered through a piece of linen and allowed to cool, when the 
white of an egg, beaten to a froth, is added. The mixture is 
again boiled to coagulate the albumen, which clarifies the 
serum. The liquid is ready for use as soon as filtered. 

As this bath soon ferments, it must be used within two days 
of its preparation. 

The bath is filtered into a deep porcelain tray, and a waxed 
sheet is first floated on it, avoiding air bubbles, and then com- 
pletely immersed in it, all air bells being removed with a clean 
camel's hair brush or a glass triangle. This process is repeated 
until a sufficient quantity of paper has been immersed, great 
care being taken that no air bells are allowed to form between 
the sheets. After soaking for two hours the sheets are pinned 
up by one corner to dry. In this condition they will keep in- 
definitely. 

Sensitising. The sheets are immersed one after the other 
in the following bath : 

Distilled water 3 ounces 

Nitrate of silver 108 grains 

Glacial acetic acid ... 125 to 150 grains 

To this are added eight to ten drops of the iodide solution 
given above. The mixture is well stirred and filtered into a 
porcelain tray used only for this purpose. The iodized sheets 
are to be immersed in this bath as described for iodizing, 
avoiding air bells. The sheets must not be allowed to stick 
together, and each one is turned over with a pair of bone or 
glass pincers before another is introduced. 

After three or four minutes immersion the sheets are re- 
moved one by one and passed successively through three or 
four baths of distilled water. They are then placed between 
sheets of strong, pure blotting-paper and all excess of moisture 
removed, after which they are dried under pressure between 
fresh blotters. The first and second wash waters should be 
renewed for every three or four sheets. The more thorough 
the washing the longer the sheets will keep, but the less their 
sensitiveness. In any event they will keep only two or three 
days. 



CALOTYPE. 37 

The paper, after being: iodized, usually loses somewhat of 
its waxed appearance, which can be restored by placing the 
sheets previous to sensitizing between. blotters and smoothing 
with a warm iron. 

Exposure. The prepared sheets are made ready for expos- 
ure as in Talbot's process and the exposure varies from ten to 
twenty minutes, according to circumstances. 

Development and Fixing. These operations are the same 
as in Talbot's method, except that the waxed paper is im- 
mersed in the developer. 

Pelegry's Process. This method is superior to the forego- 
ing in the superior keeping qualities which it confers upon 
the sensitized sheets and in its greater sensitiveness. 

Plain Saxe paper is immersed for a few moments in the 
iodide bath given in Le Gray's method, and hung up by one 
corner to dry. 

When wanted for use the dried sheets are sensitized by a 
three minutes immersion in the following bath : 

Distilled water 3^ ounces 

Nitrate of silver 154 grains 

Citric acid 10 grains 

The sheets are immersed in the bath as in Le Gray's pro- 
cess, but no more than five sheets must be sensitized at the 
same time. 

After remaining in the bath the requisite length of time, 
the sheets are removed one by one, allowed to drain slightly, 
and placed in a tray containing distilled water. Five more 
sheets are then sensitized and placed with the others. After 
a short soaking, during which the tray is rocked, the water is 
poured away, and a fresh supply added. The tray is again 
rocked -for a few moments and the sheets are next placed in a 
tray containing a filtered solution of chloride of sodium, one 
to one hundred, to destroy the last traces of nitrate of silver. 

After a short sojourn in this bath they are well washed in 
several changes of water, and finally immersed for two min- 
utes in a tannin bath made as follows : 

Two hundred and thirty grains of dextrine are macerated in 
a mortar with a little water ; when solution is complete the 



38 THE PHOTOGRAPHIC NEGATIVE. 

bulk is made up to twelve ounces of water, and the solution 
filtered. To this is added a filtered solution of two hundred 
and thirty grains of tannin in twelve ounces of water, and 
finally forty-five grains of gallic acid previously dissolved in 
four drams of alcohol. 

After treatment with this preservative the paper is hung up 
to dry. 

Paper prepared as above and preserved in a dark dry place 
will keep good from three to six months. The above formulae 
will prepare 18 by 22 sheets of paper. 

Exposure. Well-lighted landscapes require from five to 
six minutes exposure. Sombre views will require at least 
thirty minutes for full exposure. 

Development. The development should, if possible, be ef- 
fected within a few hours of exposure, but in case of necessity 
it may be deferred for some days. 

The developer is thus compounded : 

Water 3i drams 

Pyrogallic acid 15 grains 

Citric acid 15 grains 

The sheet to be developed is first moistened in a tray con- 
taining pure water and then immersed in the pyro solution, in 
which it is turned several times to insure equalization of the 
developer. The negative is then removed from the developer 
to which a dram or two of a three to one hundred solution of 
nitrate of silver is added : the tray is rocked to insure an equal 
mixture, and the negative is again placed in the solution. 
The image soon appears and development is arrested as soon 
as the details are well out and the density seems sufficient, the 
tray being well rocked. The negative is then washed in two 
changes of water and fixed in a one to six hyposulphite of 
soda solution, in which it is allowed to remain from thirty to- 
forty minutes. It is then well washed and dried between 
blotting-papers. As soon as dry it is ready for oiling, which 
may be done as best suits the operator's taste and convenience,, 
either with castor oil, translucine, vaseline, or wax. 



OHAPTEK IV. 

SESSITIVE SURFACES ON GLASS. PREPARATION OP THE GLASS. 

THE glass plates should be selected with great care. They 
should be flat, and free from scratches and bubbles. For small 
sizes ordinary glass of good manufacture will answer, but for 
large pictures and process work, plate, or patent-plate, should 
be used. The rough edges should be smoothed down with a 
flat file, and the glasses should never be packed with pieces of 
printed paper between them, since printer's ink is apt to leave 
greasy spots on the plates, which must be perfectly clean 
before they are coated with the collodion or emulsion. New 
plates should be soaked for some hours in a solution of 
carbonate of soda, and then well washed and soaked for some 
time in a solution of equal parts of nitric acid and water. They 
are then well washed and dried, if not to be albumenized. 
Old collodion plates should be immersed over night in the fol- 
lowing solution : 

Sulphuric acid 1 ounce 

Bichromate of potash 1 ounce 

Water 16 ounces 

and then washed. 

This solution quickly destroys organic substances, but it must 
be renewed as soon as crystals are formed. 

In all cases it is well to drain the plates on blotting paper, 
and to rub them dry with a piece of canton-flannel, which is 
used for no other purpose. 

The Final Cleaning of the Glasses for the Albumen and 
Collodion Processes. After the preliminary treatment with 
acid or bichromate of potash the dried plates are breathed on 
and rubbed with a clean towel kept for this purpose exclu- 
sively. It is important that the fingers do not touch the plate. 



40 THE PHOTOGRAPHIC NEGATIVE. 

The towel is spread out on a clean table, the plate is laid upon 
it, and one end of the towel is folded over one edge of the 
plate, which is then rubbed with the other end of the towel. 

After both sides and the edges of the plates have been 
thoroughly rubbed, it is tested by breathing upon it and ex- 
amining it by reflected light. If it is perfectly clean the 
moisture of the breath will evaporate evenly. If, however, it 
shows spots it must be again breathed on and rubbed. If this 
fails to remove the spots, the plate must be returned to the 
acid bath. "When the plate appears perfectly clean after this 
treatment, it is ready for the final polishing, which is done 
with chamois leather pads. The plate may be held in a clean- 
ing vice or laid on a clean towel. A small quantity of alcohol 
is then poured on the plate and rubbed over it with one 
of the pads ; the plate is next polished with another pad, and 
may be considered finished when it takes the breath evenly. 

Instead of alcohol, old and worthless collodion is often used. 
Varnished plates must be soaked for some hours in a solution 
of soda ; they are then washed with water, soaked in the acid 
bath, washed, and polished as above. 

The towels and chamois skins used for cleaning and polish- 
ing must be washed in soda, never with soap. 

Albumenizing the Glasses. In order to avoid the tedious 
operation of polishing, many operators prefer to flow an albu- 
men solution over the plate after it has been treated with the 
acid bath given above. The following solution is poured over 
the plate while still wet : 

Whites of 2 eggs 

Water 64 ounces 

Ammonia 1 dram 

Iodide of potassium % dram 

This is placed in a bottle containing glass broken up into 
small pieces and well shaken for fifteen minutes ; it is then 
filtered and flowed over the glasses, the surplus being drained 
away to waste. The plates are racked away to dry in a room 
free from dust. They will keep for a month, and give as good 
results as those which have been polished. 



SENSITIVE SUKFACES ON GLASS. 41 

TREATMENT OF THE GLASSES FOR THE GELATINE EMULSION 
PEOCESS. 

The glass of old negatives which, for any cause, have become 
useless for printing, may be again coated after the films have 
been removed. The simplest method of removing old films is 
to soak the plates in a moderately strong solution of hydro- 
chloric acid until the films are easily detached from the glasses, 
which after being well washed in clean warm water and rubbed 
with a coarse cloth to remove all adhering pieces of film, are 
ready for further treatment. 

Cleaning the Glass. Both old and new glass should be 
soaked in a ten per cent, solution of nitric acid, then well 
washed, and immersed in a solution of carbonate of soda con- 
taining a little alcohol. The plates while in this solution are 
well rubbed with a clean cloth, then washed in clean cold water 
until it flows evenly over them, rinsed in distilled water, and 
stood up to dry on blotting-paper. When dry they should 
be well wrapped up to prevent dust from settling on them. 

Polishing with Talc. When the films are to be stripped from 
the glass after fixing, the plates must be polished with French 
chalk. This is done by dusting a little of the chalk over them 
and polishing with a clean piece of linen, using a circular 
motion. All excess of chalk is dusted off with a camel's-hair 
brush. The plates are then flowed with plain collodion, and 
coated with the emulsion when the collodion is dry. 

Substrata. It is the practice of many coaters to give the 
plates a substratum of some kind to prevent blisters, or to as- 
sist the flowing of the emulsion. A few of the best of these 
substrata are here given. 

1. White of egg-. 1 ounce 

Water 20 ounces 

Alcohol 1 ounce 

Carbolic acid 20 drops 

Add the carbolic acid to the alcohol, and stir well ; then pour 
the mixture into the albumen and water which have been pre- 
viously mixed, then filter. 



42 THE PHOTOGRAPHIC NEGATIVE. 

DR. VOGELS. 

2. a. Gelatine 150 grains 

Acetic acid % ounce 

Dissolve by heat. 

b. Chrome alum 10 grains 

Water K ounce 

For use take of a, 2^ parts ; Z>, 1 part ; alcohol, 70 parts, and 
filter. Coat the plates as with collodion. 

3. Soluble water glass 1 ounce 

Albumen . 8 ounces 

Water Bounces 

The wet plates are coated with this solution, drained, 
dried, and washed. 

4. Gelatine 75 grains 

Distilled water 60 ounces 

Ammonia 2 drams 

Alcohol 1 ounce 

Soak the gelatine in half the given quantity of water, then 
add the remaining half at the boiling point ; when cool add the 
ammonia and alcohol, and filter. 

5. White of egg 1 ounce 

Water 100 ounces 

Ammonia 5 drops 

Shake well for five minutes, and then filter. 

6. India rubber 10 grains 

Water 1 ounce 

Filter and flow over the plates like collodion. 

More care must be taken in cleaning the plates when a sub- 
stratum is to be used, the difficulty being to secure an even 
coating. 

Instead of flowing the above solutions over the plates, they 
may be applied with a Blanchard brush, which is made by tie- 
ing a double thickness of fine canton-flannel, ribbed side out, 
over one end of a strip of glass about six inches long and two 



SENSITIVE SURFACES ON GLASS. 



inches wide. The brush is dipped in the solution and the ex- 
cess squeezed out against the side of the beaker. The plate is 
then brushed smoothly down the surface in parallel lines. In 
this way a thin and even coating is applied. 




CHAPTEK Y. 

THE ALBUMEN PROCESS. 

. THE second step in the development of the negative process 
was the employment of albumen as a vehicle for the suspen- 
sion of the finely-divided sensitive salts, and, in consequence, 
the use of glass as the means of support. Niepce de Saint 
Yictor seems to have been the first to work out a practical 
method for the use of albumen, and the process was greatly 
improved by later experimenters. 

Although rarely used to-day, the process is a valuable one 
for delicate work, where the utmost possible fineness of grain 
is desired. 

The drawbacks to the more general adoption of a process 
which undoubtedly yields the very finest photographic results, 
are, the long exposure necessary, the difficulty of securing an 
even coating of the extreme tenuity required to prevent the 
film from leaving the glass, and the extreme care demanded 
to prevent dust from settling on the films while drying. 
Methods of overcoming these difficulties will be given under 
the practical manipulations soon to be described. 

The general outline of the process is as follows : The whites 
of several eggs are carefully separated from the yolks and 
germs, and beaten to a froth with a bundle of quill pens or a 
wooden fork. After standing for some hours, the deposit of 
albumen is decanted and filtered by upward filtration, as de- 
scribed on page 19. 

An addition of an aqueous solution of iodide and bromide 
of potassium or ammonium is then made, and the mixture is 
well stirred and filtered as before. From this point on, the 
greatest precautions must be taken to prevent particles of dust 
from settling in the mixture. 



THE ALBUMEN PKOCESS. 45 

The plates, which must be plate or patent plate, are next 
coated and dried in a perfectly horizontal position. In this 
condition, the plates are insensitive, and will keep for an 
indefinite period. They should be stored in a dust-proof box. 
When wanted for use, they are sensitized by an immersion in 
a nitrate of silver bath acidified with glacial acetic acid. The 
effect of this bath is to coagulate the albumen, to form the 
albuminate of silver, and to transform the soluble, insensitive 
iodide and bromide into the insoluble and sensitive iodide and 
bromide of silver. Therefore, the operation of sensitizing 
must be performed in yellow light. 

After being sensitized, the plates are washed in many 
changes of pure filtered water, to remove all traces of nitrate 
of silver; they are then dried by heat and are ready to be 



GOBERT'S ALBUMEN METHOD. 

Formulae. 
No. 1. THE ALBUMEN MIXTURE. 

Albumen from fresh eggs 26 drams 

Iodide of ammonium 15 grains 

Bromide of potassium 4 grains 

Iodine in pellets 4 grains 

First dissolve the salts in two ounces of water and then dis- 
solve the iodine. Then add the solution to the albumen, beat 
to a froth, and, after standing for some" hours, decant the albu- 
men and filter twice, as described above. 

No. 2. THE SENSITIZING BATH. 

Distilled water 4 ounces 

Nitrate of silver 155 grains 

Glacial acetic acid 2% drams 

MANIPULATIONS. 

Cleaning the Glass. Pour a few drops of hydrochloric acid 
on the surface of the glass plate, previously freed from all im- 
purity by soaking first in a solution of caustic potash, then in 
dilute nitric acid, and well washed under the tap. Then polish 



46 THE PHOTOGRAPHIC NEGATIVE. 

with a dabber of cotton dipped in the following iodine solu- 
tion : 

Iodine 4 grains 

Alcohol 4 ounces 

This is well rubbed in, and the plate dried with a piece of 
fine linen. 

Coating. A sufficient quantity of solution No. 1 is poured 
over the plate, which is held in the left hand by means of a 
pneumatic holder having a vertical handle provided with a 
small brass hook at the end. The albumen should be poured 
in a pool on the right-hand upper corner of the plate. When 
the surface of the plate is completely covered, to effect which 
some coaxing with a glass rod may be necessary, the excess is 
drained off in a reserve flask for filtration. 

A pipette will be found very convenient for getting the 
albumen on the plate free from bubbles. 

After draining as closely as possible, the plate is rocked 
gently to equalize the film. If any specks of dust or air bells 
are noticed, they must be removed with the point of a clean 
piece of paper, or with the pipette. 

Notwithstanding the close draining, the film is still too 
thick ; it must be made thinner, and at the same time equal- 
ized. This is done by suspending it, film down, by catching 
the hook in the handle in the loop of a doubled string hanging 
from the ceiling of the room. A slow rotary movement is 
then given to the plate. - The centrifugal force thus generated 
throws off all excess of albumen, and equalizes the film except 
along the edges, where ridges are formed which are dried with 
blotting-paper when the plate is removed from the string. 

In order to avoid spots of albumen on the floor and walls, it 
is best to suspend the plate in a large round metallic tray. 

Drying the Plate. The plate must be dried rapidly, and in 
a perfectly horizontal position. Perhaps the best method of 
combining these requisites, while at the same time reducing to a 
minimum the danger of dust falling on the film, is to place 
the plate film downwards on three levelling screws provided 
with needle points ; these screws stand on an iron plate placed 
over an oil or gas stove. 



THE ALBUMEN PROCESS. 47 

The old daguerreotype gilding stand will be found a very 
convenient drying apparatus. If neither of these means are at 
hand, the plate may be dried by placing it on a warm iron 
plate film up, first putting two or three sheets of blotting- 
paper on the iron to equalize the heat. 

Fuming with Vapors of Iodine. The action of the sensit- 
izing bath is greatly assisted by fuming the dried film with the 
vapors of iodine. The simplest way of doing this is to cut a 
rectangular opening, somewhat smaller than the plate, in the 
cover of a wooden box four or five inches in depth. Some 
pellets of iodine are placed in the bottom of the box, and the 
plate is laid over the opening in the cover film down, and 
fumed until it assumes a rich golden hue. It is then taken 
from the box, and after a short exposure to the atmosphere to 
allow the excess of iodine to volatilize, it is ready to be sen- 
sitized. 

Sensitizing. The plate is sensitized in yellow light by a 
three minute immersion in solution No. 2, above. It is then 
well washed in several changes of water, allowed to drain, and 
the preservative, a saturated solution of gallic acid, is flowed 
over it. It is then dried by gentle heat. The dried plates 
will retain their good qualities for some weeks. The films 
should have a decided opalescent appearance. If this is want- 
ing, the film is too thin, owing to a too rapid rotation on the 
pneumatic holder. The remedy is obvious. The time of ex- 
posure varies from 10 to 30 minutes, according to circumstances. 

Development. The exposed plates are developed in a bath 
containing a saturated solution of gallic acid, to which has been 
added a few drops of a 1 to 30 solution of nitrate of silver. 

The process should not be unduly hastened ; the best results 
are gained by slow development. The developer must be 
thrown away when it becomes cloudy. 

The developer thus compounded will bring out all the details 
and give good printing density on properly exposed plates. If, 
however, the image shows a lack of detail and density after 
prolonged development, a fresh developer, containing gallic 
acid and silver, must be compounded. 

Fixing. After development the plate is rinsed in clean 



48 TllE PHOTOGRAPHIC NEGATIVE. 

water and immersed in a ten per cent, solution of hyposulphite 
of soda until the opalescent appearance has disappeared. It is 
then well washed in running water, to eliminate the hypo, and 
when dry it is ready to be printed from. 

VARIOUS MODIFICATIONS OF THE ALBUMEN PROCESS. 

Numerous experiments have been made by different investi- 
gators to shorten the time of exposure by introducing various 
modifications, consisting chiefly in the use of a larger propor- 
tion of iodide and the addition of certain substances to produce 
a more porous, and, therefore, more sensitive film. A few of 
the best of these are here given. 

Sellers Modification. 

Water 5 drams 

White sugar 120 grains 

Iodide of potassium 61 grains 

Iodine in pellets 12 grains 

Bromide of potassium. 12 grains 

Pour the solution into 14 ounces of albumen, beat to a froth, 
and, after standing for twenty-four hours, decant three-fourths 
of the liquid for use. The remaining manipulations are the 
same as described above. 

tiagofs Modification. 

Dextrine 140 grains 

Iodide of potassium 46 grains 

Bromide of potassium 8 grains 

Distilled water 11 drams 

Dissolve by heat, filter and add the whites of six eggs. All 
the other operations are as described above, with the following 
exceptions : Sensitize on a ten per cent, solution of nitrate of 
silver, containing twenty -five per cent, of glacial acetic acid, 
and develop in the following bath : 

Distilled water . 12)^ ounces 

Gallic acid 108 grains 

Acetate of lime 46 grains 

at a temperature varying from 120 to 140 deg. 



THE ALBUMEN PROCESS. 49 

Couppier's Modification. 

Albumen 25 drams 

Distilled water 6)^ drams 

Iodide of potassium 15 grains 

The manipulations are the same as in Gobert's method. 

The Albumen Honey Process. The following description 
of this process, as formerly worked by Whipple and Black, is 
taken from the Photographic Times. The plates are given a 
thin, even coating of the following solution : 

Albumen 8 ounces 

Honey 7 ounces 

To which has been added 

Iodide of potassium . v 3 grains 

Bromide of potassium 20 grains 

Chloride of sodium 10 grains 

Water 2 ounces 

The mixture is beaten to a stiff froth, allowed to settle, and 
then filtered. 

The dried plates are sensitized, while still warm, in the fol- 
lowing bath : 

Nitrate of silver 1 ounce 

Acetic acid, No. 8 8 to 10 drams 

Water 10 ounces 

The plate is kept in constant motion while in the bath. 
After sensitizing, the plates are washed slightly, if to be used 
immediately. If, however, they are to be kept for any length 
of time, they must be washed until all the silver is washed 
away. Development is effected in a saturated solution of 
gallic acid, to which a few drops of a nitrate of silver solution 
have been added. 




CHAPTER VI. 

THE COLLODION PROCESS, WET-PLATES. 

LB GKAY was the first to suggest collodion as a vehicle for 
the suspension of the salts of silver in place of the albumen 
method of St. Victor. To Scott Archer and Dr. Diamond, 
however, belong the credit of having been the first to intro- 
duce the collodion process in the practical form in which it is 
still used. 

This was in 1851, and the publication of their process revo- 
lutionised photographic methods, and incited many experi- 
menters to investigate the new process. 

It would be impracticable to enter into a detailed discussion 
of the improvements discovered by such patient investigators 
as Martin, Gaudin, Spiller, Sutton, Schnauss, Carey Lea, 
Sdronheim, Roettcher, Bellitzky, Vogel, Eder, Duchochois, 
and others, to all of whom photography is deeply indebted. 
The history of photography has been ably treated in another 
volume of this series, and need not be repeated here. 

The advent of gelatine plates by no means sounded the 
death knell of collodion. It is still in common use by not a 
few of our best practitioners in all cases where the extreme of 
rapidity is not called for, and in the opinion of many good 
judges collodion negatives possess qualities which are only 
with extreme difficulty conferred upon gelatine plates. 

For these reasons, the process is fully described in all its 
details, as practised by the best operators. 

The base of collodion is the substance known as pyroxyline, 
or soluble gun-cotton, which is prepared by submitting cotton, 
paper, or other like substances, to the action of a mixture of 
sulphuric and nitric acids. The resulting substance, when dis- 
solved in a mixture of ether and alcohol, forms the volatile, 
viscous compound known as collodion. 






THE COLLODION PROCESS, WET-PLATES. 51 

The preparation of pyroxyline suitable for photographic 
work is a somewhat delicate operation, and, as a rule, it is wise 
to purchase it ready-made of the dealer. The two formulae 
for its manufacture which are given below, are recommended 
by Hardwich, who at one time made many experiments in this 

direction. 

No. 1. 

Sulphuric acid, sp. gr. 1.842 at 59 deg. F 18 ounces 

Nitric acid, sp. gr. 1.456 6 ounces 

Water 4% ounces 

Cottonwool 360 grains 

No. 2. 

Sulphuric acid, 1.842 6 o.unces 

Nitrate of potassium 3^ ounces 

Cotton wool 62 ounces 

Water 1 ounce 

Mr. Abney says the cotton must be first well steeped in an 
aqueous solution of carbonate of soda, and 'then be well washed 
and perfectly dried. It should then be made up into ten or 
twelve balls. 

The nitrate of potassium should be as free from chloride of 
potassium as possible, and dried in an air bath at a temperature 
of about 120 deg. 

The water and nitric acid are poured into a porcelain dish 
and well mixed, then the sulphuric acid is added with constant 
stirring. The temperature will rise to about 170 deg., and 
the liquid must be allowed to cool down to about 150 deg. 
The balls of cotton are then immersed separately in the liquid, 
as rapidly as possible, to prevent decomposition. After receiv- 
ing a thorough soaking, using a glass or porcelain spatula to 
keep the balls submerged, they are allowed to remain ten or 
fifteen minutes in the solution. They are then raised by the 
spatula, as much of the liquid as possible being extracted by 
pressing them against the side of the dish, and then they are 
placed in a large vessel full of clean water. The washing 
must be continued until a piece of blue litmus paper retains 
its color after two or three minutes' contact with the cotton, 
which, when dried, should weigh about 25 per cent, more than 
the original cotton. 



52 THE PHOTOGRAPHIC NEGATIVE. 

It is important that the acids be of the specific gravity indi- 
cated in the formulae, as any deviation will materially change 
the character of the pyroxyline. The second formula is usu- 
ally to be preferred. 

The Solvents. Alcohol and ether in varying proportions 
are the solvents of pyroxyline employed in the manufacture 
of collodion. Many modifications may be made in the film by 
altering the proportions of the solvents. Up to a certain 
point an increase in the quantity of alcohol confers greater 
sensitiveness and density. It must not be too largely in ex- 
cess, however, or tender, porous films will result. 

An excess of ether gives strong, contractile films, which are 
easily stripped from the glass. The specific gravity of the 
alcohol must be varied to suit the sample of pyroxyline used 
in making up the collodion. 

For pyroxyline prepared at a high temperature the alcohol 
should have a spec-iric gravity of .812. For the tougher 
variety of pyroxyline a specific gravity of .820 is about right. 

The ether should be as pure as possible. 

The normal proportion of the solvents is equal volumes of 
each, but this may be modified as required. 

The lodizers. These are the various metallic iodides and 
bromides which are added to the collodion to produce, when 
the plate is immersed in the silver bath, the sensitive iodide and 
bromide of silver. Obviously only those iodides and bromides 
can be used, which are soluble in alcohol and ether. Those 
most commonly employed are the iodides and bromides of 
potassium, ammonium, calcium, cadmium, sodium, and, more 
rarely, lithium. 

These are not all of equal value for the preparation of the 
salted collodion. Three factors determine the choice of the 
Boluble salt, viz., the physical action of the salts ; the perman- 
ency of the resulting collodion, and the solubility of the salt. 

Cadmium, although very soluble and giving a collodion of 
good keeping qualities, has a tendency to thicken the film, 
and must, therefore, be used with caution and only in connec- 
tion with other salts. 

The iodides of potassium and ammonium give more intense 



THE COLLODION PROCESS, WET-PLATES. 53 

images than the iodide of cadmium, but they are not so solu- 
ble and the resulting collodion does not keep so well. 

The salts of sodium and lithium are but rarely used on ac- 
count of their decomposing action. 

A collodion containing iodide alone gives great density with 
little detail in the shadows, one containing bromide only gives 
less density but more detail in the shadows. 

For this reason the common practice is to use mixed collo- 
dion for general work to secure both density and detail. 

Plain Collodion. It is customary to make up a stock of 
plain collodion to be iodized in sufficient quantity for the 
work in hand. This plain collodion can be kept indefinitely 
in well-stoppered bottles. The following formulae are given 
for its preparation : 

FOR COLD WEATHER. 

Pyroxyline 185 to 215 grains 

Alcohol 16 ounces 

Ether 19 ounces 

FOR WARM WEATHER. 

Pyroxyl ine 185 to 215 grains 

Alcohol 17J ounces 

Ether 17 ounces 

The quantity of pyroxyline may be increased if desired, 
but it should not exceed two per cent. An increase in pyroxy- 
line increases the sensitiveness but diminishes the flowing 
quality of the collodion. 

The usual method of making up the plain collodion is to 
add the pyroxyline to the alcohol and then to add the ether in 
small quantities, shaking well after each addition. 

Some operators, however, prefer to add the pyroxyline to 
the ether, shaking it up well until the fibres are well dis- 
tended, and then to add the alcohol in small quantities with 
constant shaking. 

In either case the solution is allowed to stand for twenty- 
four hours before being used. Sufficient of the clear liquid 
for the work to be done is then decanted off. 

Salted Collodion. Plain collodion is iodized or salted by 
the addition of soluble iodides or bromides, or both. 



54: THE PHOTOGRAPHIC NEGATIVE. 

The following formulae will be found suitable for general 
landscapes, and portrait work : 

BROMIZED COLLODION. 

Bromide of zinc 247 grains 

Plain collodion 35 ounces 

IODIZED COLLODION. 

a. Iodide of ammonium 123 grains 

Plain collodion 35 ounces 

b. Iodide of cadmium 154 grains 

Plain collodion 35 ounces 

a must be used at once ; 5 will keep indefinitely. 
BROMO-IODIZED COLLODION. 

a. Iodide of ammonium 108 grains 

Bromide of cadmium 62 grains 

Plain collodion 35 ounces 

b. Iodide of cadmium 139 grains 

Bromide of cadmium 62 grains 

Plain collodion 35 ounces 

a can be used soon after making ; b must be allowed to 
ripen for some time before it will flow well. 

Another method of salting the collodion is to add to ninety 
parts of plain collodion, ten parts of the following bromo- 
iodide solution : 

Absolute alcohol 7f ounces 

Iodide of cadmium 154 grains 

Bromide of cadmium 154 grains 

Iodide of ammonium 154 grains 

Mr. John CarbutCs Methods. Mr. Carbutt first prepares 
the double salts of potassio-cadmium iodide and ammonio- 
cadmium bromide with which he prepares two collodions, 
which are mixed for use in varying proportions. 

The potassio-cadmium iodide is made as follows : 332 parts 
of iodide of potassium and 366 parts of iodide of cadmium 
are dissolved in the smallest possible quantity of distilled 
water, and evaporated to dryness by gentle heat, and bottled 
for use. 

The ammonio-cadmium bromide is prepared by taking 196 
parts of bromide of ammonium and 272 parts of bromide 



THE COLLODION PROCESS, WET-PLATES. 55 

of cadmium and treating them as in the preparation of the 
double iodide. 

The iodized collodion is made up as follows : 

Double iodide 6 grains 

Ether .. Jounce 

Alcohol i ounce 

Pyroxyline 2 grains 

To make the bromized collodion take 

Double bromide 10 grains 

Alcohol 3 drams 

Ether 5 drams 

Pyroxyline 2 grains 

For special use these collodions are mixed in the following 
proportions : 

For interiors and dimly lighted subjects, two parts iodized 
to one part bromized. 

For quick exposures, three parts iodized to one part bromized. 
For copying and process work, five parts iodized to one 
part bromized. 

Mr. Carbutt states that this collodion should be allowed to 
ripen for six or eight weeks before it is used. If a few drops 
of tincture of iodine are added, it will be in good working or- 
der in a few days. 

DR. VOGEL'S COLLODION. 

Iodide of cadmium 1 part 

Iodide of sodium i part 

Bromide of ammonium i part 

Alcohol 80 parts 

After filtration one part, by measure, of the filtrate is 
added to three parts, by measure, of -plain collodion, contain- 
ing two per cent, of pyroxyline. The mixture may be used 

after three days. 

EQUIVALENT COLLODION. 

a. Iodide of cadmium 18 parts 

Alcohol 270 parts 

b. Bromide of cadmium 17 parts 

Alcohol 270 parts 

Two measured parts of a are added to one measured part 
of b, and nine measured parts of plain collodion, containing 
two per cent, of pyroxyline. 



56 



THE PHOTOGRAPHIC NEGATIVE. 



This collodion will keep for years. 

Care of the Collodion. The proper care of the collodion is 
a matter of great importance to the photographer who wishes 
to secure uniformly good results. 

The chemical changes which a salted collodion undergoes are 
manifested by a change of color to yellow and red, and by a 
decrease of sensitiveness. Red collodion may be corrected by 
the addition of cadmium collodion, which remains white for 
months. 

A collodion which has a tendency to turn red should be 
mixed only as wanted for use, the plain collodion and the 
iodizer being kept in separate bottles. 

The collodion also becomes thick by the evaporation of the 
solvents. When it becomes too thick to flow well it must be 
thinned down by the addition of a sufficient quantity of alcohol 
and ether in the proportions of three to five. 

When the excess of collodion is drained from the plate into 
the stock bottle it gradually becomes filled with dust, giving 
rise to spots on the plates. This evil may be avoided by drain- 
ing the excess into a separate bottle. After settling for a week 
the clear liquid can be decanted off and used for coating. 

The neck of the stock-bottle should be 
kept covered with a bell glass, and the stop- 
per should be left out as little as possible to 
prevent evaporation. 

Filtering Collodion. Many collodions set- 
tle so slowly as to require a tedious length of 
time to render them fit for use unless filtered. 
Fig. 16 shows a collodion filter. A is a 
glass funnel fitting closely into the neck of 
the bottle, and closed by the glass stopper B 
to prevent the evaporation of the collodion. 
C is a piece of glass tubing, around which 

^^^ *S washed cotton is loosely packed, through 

FIG. 16. which the collodion slowly filters. 

The Sensitizing athThe office of the bath is to make 
the collodion film sensitive by changing the metallic iodides 
and bromides into iodide and bromide of silver. 




THE COLLODION PROCESS, WET-PLATES. 57 

The utmost care and cleanliness must be exercised in the 
preparation of the bath, and a generous amount of it should 
be made up. It is customary to add a trace of iodide of potas- 
sium to prevent the bath eating away the film, owing to the 
solubility of iodide of silver, in a solution of nitrate of sil- 
ver. Dilute nitric acid is also added sparingly when the plates 
show signs of veiling. Other additions are sometimes refcom- 
mended, but their utility is doubtful. 

The strength of the bath varies somewhat according to the 
nature of the work in hand ; from 35 to 50 grains of silver to 
the ounce may be taken as the limits in either direction. 

Dr. Yogel recommends the following: 

Nitrate of silver (neutral) 100 parts 

Distilled water 1000 parts 

To which are added 25 parts of 1 per cent, aqueous solution 
of iodide of potassium. If the bath gives veiled images, a 20 
per cent, aqueous solution of nitric acid is added drop by drop 
until a trial plate developes free from fog. 

Hardwich recommends the following baths: . 

FOR BROMO-IODIZED COLLODION. 

Nitrate of silver 35 grains 

Distilled water 1 ounce 

The required quantity of solution is made up and iodized by 
the addition of a few grains of iodide of potassium. 

If the bath shows a neutral or alkaline reaction acidify with 
dilute nitrate acid until blue litmus changes slightly to red. 

FOR IODIZED COLLODION. 

Nitrate of silver 30 grains 

Distilled water 1 ounce 

The bath is iodized as before, and, if necessary, made acid by 
the addition of acetic acid. 

Great care must be taken when acidulating the nitrate bath 
not to add too much acid, which diminishes the sensitiveness 
of the film and gives weak images. The proper way is to 
add only a few drops at a time, and to sensitize, expose, and 
develop a trial plate after each addition until the image shows 
no deposit of silver in the deepest shadows, i. <?., until it is 
free from fog. 



58 . THE PHOTOGRAPHIC NEGATIVE. 

To correct a bath which is too acid the best plan is to add 
by degrees some non-acidulated nitrate solution of the same 
strength, testing with trial plates between each addition. 

Management of the Bath. Collodion plates sensitized in 
a freshly made bath generally, give clear and brilliant neg- 
atives, but by constant use the bath undergoes a change; it 
becomes charged with alcohol and ether, with the nitrates of 
potassium, ammonia, cadmium, etc., the products of double 
decomposition, with various substances derived from the 
pyroxyline, with dust and impurities from various sources. In 
this condition the bath will not produce good results; it must 
be purified. 

The insoluble substances contained in an old bath are easily 
removed by filtration. The soluble organic substances are de- 
stroyed by exposing the bath to sunlight. Under the action of 
light the greater portion of the organic matter is burnt up, as 
it were, by the nitrate of silver, which is at the same time re- 
duced and a slight trace of nitric acid is given off which aids 
the production of pure and brilliant negatives. The bath 
should be " sunned " occasionally when not in use. 

With long use the bath becomes so charged with alcohol and 
ether as to be unfit for use until these have been removed by 
evaporation. For this purpose the bath may be poured out 
into a large tray and left uncovered for some hours, when most 
of the alcohol and ether will have evaporated. The process 
may be hastened by the application of heat When this 
method is adopted the bath after evaporation must be made 
up to its original volume by the addition of distilled 
water. If turbidity is produced by this addition, the bath is 
filtered, and acetic acid added drop by drop, until a trial plate 
gives a perfectly clear negative. 

When the volume of the bath has become very much reduced, 
it may be increased by making up a new bath, observing the 
following precaution : To the old bath sufficient distilled water 
is added to bring it up to the volume desired. This addition pro- 
duces a yellowish discoloration, due to the precipitation of 
iodide of silver ; this is removed by filtration, after which suffi- 
cient nitrate of silver, in crystals, is added to bring the bath up 
to the proper strength. 



THE COLLODION PROCESS, WET-PLATES. 59 

If these simple precautions be taken no trouble need be 
feared from the silver bath, and they are all that are required. 

Testing the Strength of the Silver Bath. An approximately 
correct determination of the strength of the bath can be arrived 
at by the use of the argentometer, an instrument graduated to 
register grains of silver to the ounce of water. 

The accuracy of this test is greatly impaired by the presence 
of foreign matter in the solution. Since these are nearly al- 
ways present in the sensitizing bath, the chloride of sodium 
test should be applied when accurate knowledge of the exact 
strength is necessary or desirable. Hardwich gives the follow- 
ing simple method of applying this test : 

Pure crystallized chloride of sodium is dried by heat, to 
eliminate the water of crystalization, and dissolved in distilled 
water in the proportion of eight and one-half drams to six fluid 
ounces. This forms a standard solution, each dram of which 
will precipitate half a grain of silver. 

One dram of the bath is accurately measured out in a minim 
graduate and placed in a two-ounce stoppered phial, the gradu- 
ate is rinsed out with a dram of distilled water, which is added 
to the dram of bath. A little bichromate of potash is then 
added to the contents of the phial ; its effect is to form a deep 
red precipitate of chromate of silver. 

Two or three drams of the standard salt solution are next 
placed in a graduate and added to the contents of the phial, in 
the proportion of one dram for every four grains of nitrate 
known to have been present. The contents of the phial are 
then well shaken, and then examined to note if the red colora- 
tion shows any lessening of tint. Further additions of the salt 
solution are added, fifteen drops at a time, until the red colora- 
tion disappears, owing to the decomposition of the red chromate 
into the white chloride. The volume of salt solution used is 
then determined, when a simple calculation will give the num- 
ber of grains of silver in the original dram. 

The following example will make the method plain : In case 
the bath is thought to contain about 20 grains to the ounce, then 
one dram will contain two and one-half grains ; half a dram of 
the salt solution is added and the whole well shaken, subsequent 



60 THE PHOTOGRAPHIC NEGATIVE. 

additions must be made more cautiously, a few drops at a time, 
followed by vigorous shaking. If it is found that 40 drops of 
the salt solution were required to produce the change of color, 
the number of grains of silver in the tested dram was evidently 
$ or f of 4 = 2f grains or 21^- grains to the ounce. 

If pure chloride of sodium can not be obtained, ordinary 
chloride of ammonium may be substituted in the proportion of 
Tf grains of the chloride to 6 ounces of water. 

Development. A solution of sulphate of iron is generally 
employed as a developer for the negative. This solution has 
the property of precipitating silver from its solution as a fine 
metallic powder. The same precipitate is formed when a solu- 
tion of iron is poured over a collodion plate still wet from the 
silver bath. The formation of the precipitate is, however, con- 
fined to those parts of the plate which have been acted upon 
by light, and in this way the image is built up. 

To prevent the too rapid formation of the precipitate a di- 
lute and acidulated solution is used. 

For pictures with half tones, portraits, landscapes, etc., Dr. 
Vogel recommends the following developer : 

Sulphate of iron 3 parts 

Glacial acetic acid 3 parts 

Water 100 parts 

When an old nitrate bath is used two parts of alcohol should 
be added to the developer. 

A typical American developer is 

Sulphate of iron . 1 ounce 

Water ,..16 ounces 

Acetic acid 1 ounce 

For soft effects in portraiture the following is recommended : 

Sulphate of iron and ammonia 1% ounces 

Acetic acid 1 ounce 

Water 16 ounces 

The sulphate of iron solution must be freshly mixed every 
two or three days. The sulphate of ammonia and iron modifi- 
cation will keep for a long time. 

Intensification. In many cases the developed image is too 
weak to be printed from with good results ; it must then 



;oo 
be 



THE COLLODION PROCESS, WET-PLATES. 61 

strengthened by the process called intensification. This is 
effected by pouring on the plate a silver solution combined with 
some reducing agent, usually pyrogallic acid or sulphate of iron. 
The following formulae will produce good results : 

a. Pyrogallic acid 1 part 

Alcohol 10 parts 

b. Nitrate of silver 2 parts 

Citric acid 3 parts 

Water ' 100 parts 

This solution will keep for two weeks. 

For use dilute a small quantity of a with twenty-five parts 
of water and mix with an equal volume of b. 

In summer four parts of citric acid may be used instead of 
three, to retard the action of the intensitier. In winter it will 
be well to reduce the proportion to one part. The plate must 
be well washed before the solution is applied. 

The iron intensifier is as follows : 

a. Sulphate of iron 3 parts 

Glacial acetic acid 3 parts 

Water 100 parts 

b. Nitrate of silver 2 parts 

Citric acid 3 parts 

Alcohol 2 to 3 parts 

Water 100 parts 

Equal volumes of a and b are taken to form the intensifier. 
The advantage of this method is that the plate need not be 
washed after development. It is much better not to intensify, 
but to give the proper density to the negative by development. 

Fixing. The object of the fixing-bath is to remove the un- 
reduced iodide and bromide of silver, and so protect the pic- 
ture from further changes through the action of light. For 
this purpose either a 1 to 5 solution of hyposulphite of soda 
or a 1 to 20 solution of cyanide of potassium is employed. 

The only objection to the use of hyposulphite of soda as a 
fixing agent is the prolonged washing necessary to remove it 
from the film. 

Cyanide of potassium is more easily washed away, but it is 
a deadly poison, and attacks the half-tones unless quickly re- 
moved by washing. 



62 THE PHOTOGRAPHIC NEGATIVE. 

PRACTICAL MANIPULATIONS. 

Collodionising. The plates to be collodionized must have 
been previously cleaned, as described in Chapter IY. 

To collodionize, the plate is held between the thumb and 
fingers of the left hand at the left lower corner, and brought 
into a horizontal position. The mouth of the collodion bottle 
is brought near the surface of the plate and sufficient collodion 
is poured on to cover two-thirds of the surface. The plate is 
then gently rocked, to secure an even coating over the entire 
surface, and the surplus is drained from the lower right-hand 
corner into a separate bottle, to be filtered before being added 
to the stock collodion. 

As soon as the surface has become tacky, the plate is placed 
on the glass dipper and kept in a horizontal position until the 
lower corner has dried so that the collodion will tear. It is 
then ready for 

Sensitizing. The plate is lowered slowly and without stop- 
page into the silver solution contained in a vertical glass bath. 
Any interruption in this operation will produce lines visible 
in the finished negative. 

At first the alcoholic film repels the bath, which will run off 
the plate in greasy lines, if it is removed shortly after im- 
mersion. 

The plate must remain in the bath until these greasy lines 
disappear, being gently moved up and down. It is then placed 
in the same position on blotting-paper, with its top against the 
wall, and allowed to drain, after which it is placed in the 
holder, care being taken that the edge of the plate which left 
the bath last occupies the lower end of the holder. 

Sensitizing in Trays. The plates may be sensitized in 
trays. This method requires less silver solution than that 
with the vertical bath, but care must be taken to remove the 
scum which forms on the surface with a piece of clean paper. 

One end of the tray is raised slightly higher than the other, 
and a sufficient quantity of the silver solution is filtered into it 
to cover rather more than half of the bottom, one end of the 
plate is placed in the bath, and the plate is then lowered, face 
down, by means of a horn or silver hook. The liquid flows 



THE COLLODION PROCESS, WET-PLATES. 63 

between the glass and the bottom of the tray by capillary 
attraction and so covers the whole film. This method is 
recommended for experimental work on a small scale, as 
being more economical. 

Another method is to lower the plate film up into the solu- 
tion placed in a tray having a tank at one end. 

The tray is placed in a vertical position, the plate is placed 
in the tray, which is then rapidly lowered. 

Exposure. No definite instructions can be given as to the 
proper time of exposure, which depends on the chemical inten- 
sity of the light, the brightness of the object to be photo- 
graphed, and the size of the diaphragm. 

The plate-holder must be kept always in the vertical posi- 
tion, to prevent the running back over the plate of the silver 
solution which collects at the bottom. 

It is essential that all the operations at the camera be done ^f^ 
rapidly, as the plates will keep moist only a short time. ^-7 . s 

development. The plate, after exposure, is taken into the 
dark-room, always being kept in its original vertical position. 
It is removed from the plate-holder inclined towards the edge 
which was lowest in the holder. 

The developer is then poured on the upper part of the plate 
in such a way as to cover the whole plate with one sweep. 
This must be done gently and with care, to avoid unequal re- 
duction of the silver. 

The image now becomes visible, the high-lights appearing 
first, and gradually gains in detail and density. The operation 
must be w T atched with great care, and fresh additions of the 
developer made when necessary, the plate being kept in con- 
stant but not violent motion. 

If, after long-continued development, the details in the 
shadows do not appear, the plate was under-exposed and is 
worthless. 

If, on the contrary, all the details appear, but the image is 
wanting in contrasts, the exposure was too long, and the plate 
must be intensified. When fully developed, the plate is 
washed, and if not sufficiently dense, it is intensified before 
fixing. 



64 THE PHOTOGRAPHIC NEGATIVE. 

Intensification. The intensifier, mixed as directed on page 
61, is poured over the plate and allowed to act until sufficient 
density is reached ; it is then thoroughly washed and fixed. 
The intensifier must be rejected as soon as it becomes turbid. 
Intensification may be done after fixing. 

Fixing. The plate is immersed in either of the fixing solu- 
tions given on page 61, until the last trace of iodide of silver 
has disappeared. It is then well washed and dried. 

Varnishing. The instructions given on page 31 may be 
followed here. 

Defects. The most common defects in collodion negatives 
are the following : 

Fog: due, a, to dirty plates; 2, to want of acid in the de- 
veloper ; c, to over-exposure ; d, to an alkaline bath solution ; 
e, to improper exposure to white light ; /, to vapors in the 
developing-room. 

Weak images : due, a, to a poor collodion ; 5, to a weak 
sensitizing solution ; <?, to a bath charged with organic matter ; 
<7, to bad lighting of the subject ; e, to an over-strong devel- 
oper. 

Pin-holes : due, #, to dust on the plate ; b, to an over or 
under-iodized bath. 

Black specks : due, #, to dust in the camera, slide, dark- 
room, or collodion. 

Comet-like spots : due to undissolved particles of pyroxyline 
in the collodion. 

Transparent spots : due to dust in the collodion. 

Scum on the film: a, the plate has been kept too long out 
of the bath ; or, , the developer was too strong. 

Wavy lines on the film : either the collodion contains too 
much iodide or alcohol, or the pyroxyline is too strong, 

Transparent markings : due, #, to unequal sensitizing, or, 
b, to the developer refusing to flow. 

Blurring of the image : due to reflections from the back of 
the plate ; it may be diminished by coating the back of the 
plate with some non- actinic color, such as sienna, mixed in 
gum-water. 



CHAPTER VII. 

THE COLLODION PROCESS. DRY PLATES. 

HARDLY had the wet collodion process established itself in 
public favor before attempts were made to make it 
more suitable for the landscape photographer by giving him 
dry collodion plates, of fair keeping qualities. Up to the time 
when the gelatine process was introduced, the zeal of experi- 
menters knew no flagging, and many valuable dry plate proc- 
esses were elaborated by skillful workers. The fact that all 
of these processes have been almost entirely superseded by the 
gelatine dry plate, does not make a description of some of the 
best unnecessary or out of place. They have a value still, no- 
tably for the economical production of lantern slides on a large 
scale, while the Taupinot process gives results extremely diffi- 
cult to be equalled by the more modern method. 

Success in these processes depends on the strict observance 
of the following principles : 

Firm adherence of the sensitive surface. 

Permeability of the collodion film. 

The use of a large proportion of bromide. 

Complete elimination of all the free nitrate of silver by 
copious washing. 

The use of a preserver to give keeping qualities to the plates. 

The use of alkaline, or other similar developers to reduce the 
bromide of silver to the metallic state. 

The strict observance of all the details given under each of 
the processes described, will enable the operator to meet all 
these conditions and make success certain. 

TaupinoCs Collodio-Albumen Process. This method gives 
negatives of fine detail and exquisite delicacy. The manipu- 
lations are not over difficult, and the plates are fairly sensitive. 






66 THE PHOTOGRAPHIC NEGATIVE. 

The manipulations may be thus summarized : The plates, 
previously polished with French chalk, or flowed over with a 
thin film of albumen, as described in Chapter V., are collodion- 
ized as usual with any of the collodions given in the previous 
chapter. They are then sensitized in the nitrate bath, well 
washed, and given a coating of iodized or iodo-bromized albu- 
men, which destroys the sensitiveness conferred by the silver 
bath. When dry the plates will present a brilliant, opalescent 
appearance, and can be preserved indefinitely. When wanted 
for use they are sensitized in an acidulated silver bath, thoroughly 
washed, and then flowed with a solution of gallic acid to pre- 
serve them. In this condition they will retain their good qual- 
ities for two weeks. 

Manipulations. Collodionize as usual ; stand the plate on 
one corner on two or three thicknesses of blotting paper, sup- 
porting it against the wall, face down. After a minute's stand- 
ing, sensitize as usual on the following bath : 

Water 3J4 ounces 

Nitrate of silver 100 to 125 grains 

Nitric acid ... .3 or 4 drops 

This bath should be filtered occasionally, kept acid, and 
stood in the sun when not in use. 

After being sensitized the plate is washed in three or four 
changes of pure water, and then allowed to drain, one of the 
lower corners being supported in a beaker, the upper corner 
resting against the wall, the film side being uppermost. 

After being well drained the plate is coated with the follow- 
ing albumen solution : 

Albumen 3% ounces 

Bromide of ammonium 3% grains 

Iodide of ammonium 15 grains 

The albumen must first be beaten and treated as described 
on page 40. 

A more simple method is that of Mr. Ackland. Place the 
whites of several eggs in a large graduate, and for each three 
and one-half ounces of albumen add two drams of a 1 to 10 solu- 
tion of glacial acetic acid ; gently stir the mixture with a glass 
rod until the albumen becomes fluid, then allow it to stand for 



THE COLLODION PROCESS. DKY PLATES. 67 

two hours ; then decant the clear portion into a funnel, having a 
piece of sponge in the tube ; when this has filtered through, pour 
in the balance of the liquid. Before using, the albumen must 
be again filtered through filter paper, avoiding air bubbles by 
bringing the tube of the filter in contact with the side of the 
glass, or by the method of upward filtration before described. 

This solution is flowed over the plate like collodion, and the 
plate is drained as described above. When well drained it is 
dried in the drying box, or spontaneously in the open air, sup- 
ported vertically, so that no part of the film is in contact with 
any foreign substance. 

When dry the plates, which are insensitive, will keep inde- 
finitely. 

To sensitize they are immersed in the following bath : 

Water 3^ ounces 

Nitrate of silver 100 grains 

Glacial acetic acid 2 drams 

Each plate remains in the bath one-half a minute ; it is then 
washed in four changes of distilled or filtered water and the 
gallic acid preservative flowed over it, (water, thirty-five 
ounces ; gallic acid, seventy-five grains); this is applied twice, 
and the plate is then dried. Plates prepared in this way will 
retain their good qualities for two weeks. 

Exposure and Development. The time of exposure varies 
from four to ten minutes, according to circumstances. 

The image is developed with either of the following de- 
velopers : 

Water. : 35 ounces 

Gallic acid 45 grains 

Pyrogallic acid 45 grains 

Glacial acetic acid 4 drams 

The plate is placed in a tray and sufficient of this solution 
poured over it to cover it. While this is acting one to two 
drams of a one to twenty-five solution of nitrate of silver are 
placed in a graduate, and the contents of the tray poured into 
it. The liquid is then returned to the tray ; the image will 
soon appear and rapidly gain in detail and density. 



68 THE PHOTOGRAPHIC NEGATIVE. 

The following developer will generally be found the best : 

a. Water 35 ounces 

Carbonate of ammonia 155 grains 

Bromide of potassium 1 grain 

b. Water 35 ounces 

Pyrogallic acid 155 grains 

Mix a and b in equal parts and pour over the plate pre- 
viously soaked in distilled water. The image will appear 
almost immediately, and should show no signs of fog. If fog 
appears, due to over-exposure, add a few drops of a one to ten 
solution of bromide of potassium. 

The action of this developer should be stopped before all 
the details in the shadows are visible, and the development 
completed in the gallic and pyrogallic solution given above. 
The plate is immersed in this for a moment until the acetic 
acid has removed all traces of alkalinity ; it is then removed 
from the developer, to which a few drops of a one to twenty- 
five nitrate of silver solution are added, and the plate returned 
to the tray. Development is soon completed ; the plate is then 
washed and fixed in a one to five hyposulphite of soda solu- 
tion, after which it is washed, dried, and varnished as usual. 

Boiwin's Process. This method gives negatives of the very 
highest grade, free from danger of frilling, full of detail in 
the shadows, and with the distances properly rendered. The 
sensitized plates retain their good qualities for months. 

Manipulations. The plates are first well cleaned, and then 
without any previous coating they are collodionized as usual 
with the following collodion : 

Ether 17 drams 

Alcohol 11 drams 

Nitrate of silver 15 grains 

Pyroxyline 15 grains 

The nitrate of silver is placed in a glass-stoppered bottle, 
one or two drops of distilled water are poured over it, and 
when the silver is dissolved, or nearly so, the alcohol is added, 
and the bottle shaken until solution is complete; then the 
ether and the pyroxyline are added, and the bottle again 
shaken. The resulting collodion must be allowed to ripen for 






THE COLLODION PROCESS. DRY PLATES. 69 

twenty-four hours before being used. If found too thick to 
flow well, sufficient alcohol and ether in the proportions of 
four to six must be added to thin it down. The collodion 
will keep indefinitely in a dry, dark place. 

As soon as the collodion is set, the plate is immersed with- 
out stoppage in the following bath : 

Distilled water 3% ounces 

Iodide of cadmium 30 grains 

Iodide of ammonium 15 grains 

Iodide of potassium 30 grains 

Bromide of potassium 20 grains 

As soon as all traces of oiliness have disappeared, the plate 
is taken from the bath and washed in four changes of pure 
rain water, aiid then inclined against the wall, face down, to 
drain, blotting paper being placed under the lower edge. 

The next step is to cover the film with an albumen solution 
prepared as follows : 

Whites of six eggs beaten to a froth 

Distilled water 2 ounces 

Dextrine 90 grains 

Glucose 90 grains 

Iodide of potassium 22 grains 

Bromide of potassium .17 grains 

Iodide of ammonium 22 grains 

Bromide of ammonium 7 grains 

Iodide in pellets. 5 grains 

The dextrine and the glucose are first dissolved in the water 
by heat, the water lost by evaporation is replaced ; the salts 
are then dissolved, and the solution is added to the albumen 
and whole well shaken ; a few drops of ammonia are then 
added and the solution is allowed to stand some hours before 
being used. It is then filtered and flowed over the still moist 
plate ; two thin coatings are given to the plate, which is then 
dried at a temperature of about 70 deg. The plates will 
keep indefinitely. 

Sensitizing is effected by plunging the plates rapidly and 
without stoppage in the following bath : 

Distilled water 3J^ ounces 

Nitrate of silver 95 grains 

Glacial acetic acid 2^ drams 

Iodide of potassium 10 grains 



70 THE PHOTOGRAPHIC NEGATIVE. 

The plates are immersed for one minute, and then washed in 
three or four changes of distilled water. The first wash water 
being preserved in a well-corked bottle for use in develop- 
ment as explained later on, finishing up with a good washing 
Tinder a rose, or with a pipette. They are then dried in the 
dark. 

M. Boivin claims that these plates will retain all their good 
qualities for six months, and the author can certify to the good 
results obtained from them with exposures varying from one 
to five minutes. 

Development. The exposed plate is immersed for a few 
minutes in the wash water preserved for this purpose as 
directed above ; it is then immersed in a bath prepared as 
follows : 

Solution of gallic acid (1 to 250) 3% ounces 

Rain water 3% ounces 

Solution of acetate of soda (1 to 20) 4 ounces 

If the details develop too slowly add a few drops of a ten- 
gram solution of nitrate of silver. 

When the details are well out strengthen with the follow- 
ing: 

Distilled water 9 ounces 

Pyrogallic acid 15 grains 

Glacial acetic acid 3 to 4 drams 

If the negative is flat and lacks vigor, substitute the follow- 
ing: 

Distilled water 9 ounces 

Pyrogallic acid 15 grains 

Citric acid 20 to 30 grains 

If detail is wanting immerse the plate in a strong gallic acid 
solution containing a little nitrate of silver. 

Fix in a saturated solution of hyposulphite of soda. 

M. Boivin recommends the following modifications in the 
preparation, to produce still greater perfection of results. They 
are not, however, indispensable. 

After sensitizing and washing as usual, the plates are im- 
mersed in a one per cent, solution of bromide of potassium, 



THE COLLODION PROCESS. DRY PLATES. i 1 

then washed and immersed in a twenty per cent, solution of 
pyro, to which a few drops of acetic acid have been added. 
They are then well washed by pouring water over them from 
a flask and dried as usual. Plates thus prepared seem to keep 
better, are more sensitive to feeble light, and yield plucky neg- 
atives, full of fine detail in foliage. 

The Tannin Process. The plates are collodionized with one 
of the following collodions : 

No. 1. 

a. Pyroxyline (very soluble) 61 grains 

Ether 5% ounces 

Alcohol 2^8 ounces 

b. Iodide of cadmium. 135 grains 

Iodide of ammonium 37^ grains 

Bromide of cadmium 112 grains 

Alcohol 12^ ounces 

Mix three parts of a with one of S, and add enough iodine to 
give a slight tinge of color. 

Sensitize in a ten per cent, nitrate bath, slightly acidified 

with nitric acid. 

No. 2. 

Pyroxyline 88^ grains 

Bromide of cadmium 77 grains 

Bromide of ammonium , 20 grains 

Alcohol 538 ounces 

Ether 5% ounces 

In this case sensitize in a fifteen per cent, nitrate bath. 
After sensitizing, wasli well and flow twice with the follow- 
ing preservative : 

Distilled water 3% ounces 

Tannin 30 to 45 grains 

and dry as usual. 

These plates retain their good qualities for about two weeks, 
but they are slow. 

Development. The following developer is recommended : 

Carbonate of ammonia 75 grains 

Distilled water 24 ounces 

Alcohol 12 ounces 

First well moisten the plate in a sufficient quantity of this 



72 THE PHOTOGRAPHIC NEGATIVE. 

solution ; then pour the developer into a graduate and add a 
few" drops of a fifty grain alcoholic solution of pyro, and pom- 
back on the plate. More pyro may be added if necessary to 
give density. Fix and wash as usual. 

Sutton's Method for Instantaneous Views. Sensitize the 
plates on a plain bromized collodion containing 45 grains of 
bromide to every 3^- ounces of normal collodion ; sensitize on an 
eighteen per cent, nitrate bath. After washing and draining 
flow the plates with the following preservative : 

Albumen 1 part 

Water 2 parts 

Glycerine 1 part 

Dry as usual and use the same day. 

Develop in the alkaline bath given for the tannin process, 
or in the sulphate of iron bath ; in the latter case the plate 
must be immersed in a four per cent, solution of nitrate of 
silver after washing. Fix and wash as usual. 

The Gum Gallic Process, The process now to be described 
is a modification of that of Mr. Manners Gordon. Plates thus 
prepared give good detail in foliage, with an exposure varying 
from ten to sixty seconds, but they cannot be kept longer than 
four or five days. 

The plates are first given a thin coating of dilute albumen, 
to promote adhesion of the film ; they are then collodionized 
with a collodion containing equal quantities of the iodides and 
bromides ; sensitized in an eight per cent, nitrate bath and well 
washed, the last wash water containing a slight trace of pyro- 
gallic acid and a drop of glacial acetic acid. They are then 
drained and flowed with the following preserver, well filtered : 

Water 3% ounces 

Gum arable 60 grains 

Glucose or sugar candy 15 grains 

Develop with Boivin's developer, given above. Fix and 
wash as usual. 



x -v 

<t V^ 

CHAPTER VIII. 

COLLODION EMULSION. COLLODIO-BROMIDE OF SILVER. 

MANY attempts were made at various times to simplify the 
collodion process by manufacturing a collodion containing the 
sensitive substances suspended in a state of extremely fine 
division. 

The first efforts in this direction seem to have been made as 
early as 1853 by M. Gaudin, a French experimenter, but he 
did not fully work out the method. It was not until 1864 that 
the process came into general use, owing chiefly to the publica- 
tion in that year by Messrs. Sayce and Bolton of the results of 
their experiments with collodio-bromide emulsion. During the 
next ten years many formulae were published for preparing 
plates by the new method. A few of the best of these have 
been selected for detailed treatment, including the process of 
M. Chardon, which, in 1875, won the prize offered by the 
French Photographic Society for the best set of formulae for 
working this process. 

As it seems highly probable that collodion emulsion will be 
increasingly employed, especially for the production of trans- 
parencies, and as success with the process depends upon the 
attention paid to various details which are not of paramount 
importance in the wet collodion process, it has been thought 
advisable to give a few hints on points likely to be neglected by 
the experimenter. These general notes will, it is hoped, serve 
to clear the way for the more detailed description of the typi- 
cal processes given later in the chapter. 

The Pyroxyline. For washed emulsions it is better that the 
sample of pyroxyline employed should not be that known as 
high temperature cotton. The most suitable pyroxyline for 



74 THE PHOTOGRAPHIC NEGATIVE. 

this class of work is the somewhat tough or horny variety, pro- 
duced when ordinary cotton is dissolved in a preponderance of 
sulphuric acid, at a temperature varying from 140 to 150 deg. 
The after-washing of the emulsion seems to produce a change 
in this kind of pyroxyline, making it eminently suitable for 
emulsion work. 

The Bromides. As a matter of convenience it is best to 
use the bromides of ammonium, cadmium, and zinc. But ow- 
ing to the insolubility of the former salt in alcohol it must 
be combined with the bromide of cadmium to form the dou- 
ble salt of ammonium and cadmium, which is sufficiently soluble 
in alcohol to give a highly salted collodion. 

The double salt is easily made by placing the proper quanti- 
ties of the two salts in a mortar, and then to mix them inti- 
mately with the pestle. The water of crystallization is thus 
separated, and a pasty mass is formed, which is dried in an 
oven ; when thoroughly dry it is ready for use. 

Bromide of zinc gives a richer and closer film than either of 
the others, and is therefore not so suitable for slides and trans- 
parencies. 

Making the Collodion and Emulsion. The best method is 
to make up the plain collodion first, reserving, however, a part 
of the alcohol to be used later. When an emulsion is to be 
made, the bromides are placed in the emulsifying bottle and 
the proper quantity of plain collodion poured over them, and 
the bottle shaken until the salts are dissolved. In this way 
there is absolute certainty of having the amount of bromide 
necessary to convert the silver. 

The silver is to be dissolved in the reserved alcohol. This 
is a slow and tedious operation, but it may be greatly hastened 
by dissolving the silver in the smallest possible quantity of dis- 
tilled water, and then adding the alcohol at its boiling point. 
Nitrate of silver is dissolved in rather less than half its weight 
of boiling water. If then the required weight of silver be 
placed in a test tube, and half as many drops of water added 
as there were grains of silver, the latter may be dissolved by 
holding the test tube in the flame of a lamp until the water 
boils. The alcohol is then added in small quantities, and the 



COLLODION EMULSION. 75 

solution is re-heated after each addition. Or if the alcohol has 
been previously brought near its boiling point it may all be 
added at once without precipitating the silver. The silver 
solution should be heated nearly to boiling before it is added 
to the bromized collodion to avoid danger of crystallization. 
The flask is always to be washed out with a small quantity of 
alcohol reserved for that purpose, and, finally, with some of 
the emulsion itself to obtain every trace of silver. 

Ripening the Emulsion. This process is necessary to the 
production of that creamy condition which is essential to good 
results. The length of time required to attain this creaminess 
varies with different emulsions. Those in which an excess of 
silver nitrate is present will be sufficiently ripened in a few 
hours ; while those in which the bromide is in excess may re- 
quire days, and even weeks to reach their best condition. The 
ripening process can always be hastened by adding a small 
quantity of an old emulsion in good condition. 

Washing and Organifying. Washing is a most important 
matter. The best method for small batches is to pour the 
emulsion out into a clean dish of sufficient size to allow it to 
set in a thin layer, and when set to wash in many changes of 
water, the last change being distilled water. If it is proposed 
to use an organifyer, the better mode of using is to allow it to act 
a quarter of an hour upon the set film before washing is begun. 

For re-dissolving the emulsion, always use a flask of double 
the capacity required to hold the emulsion. This allows room 
for vigorous shaking. The above method of working is 
recommended by Mr. Bolton, and it is a safe one to follow. 

C/iardon's Method. 

For the successful working of this process, the two kinds of 
pyroxyline described in Chapter Y. are necessary. 

These are dissolved in separate mixtures of ether and alco- 
hol, and the solution allowed to settle. The clear liquid is 
then decanted, and the pyroxyline precipitated from both solu- 
tions by pouring the collodion from a height in a fine stream 
into a dish of pure water, stirring well during the pouring and 
for a short time afterwards. The effect of this is to deprive 



76 



THE PHOTOGRAPHIC NEGATIVE. 



the pyroxyline of its solvents, and to precipitate it in a spongy 
mass. The stirring must be continued until the precipitated 
mass feels firm and hard to the touch. The water is then 
poured off, the cotton passed through a cloth and dried. It is 
then suitable for use in making up the following collodion : 

Alcohol 1 ounce 

Ether 2 ounces 

Double bromide of cadmium and ammonium 14 grains 

Zinc bromide . .14 grains 

Precipitated pyroxyline, common 7 grains 

Precipitated pyroxyline, made by the nitrate of 

potassium method 28 grains 

A stock of this can be made up, as it keeps well. It should 
not be filtered, but should be decanted off when wanted. 

The sensitive modification, or collodio-bromide emulsion, is 
produced by adding to each ounce of the above collodion 6.2 
grains of finely-powdered nitrate of silver dissolved in 3 ounces 
of alcohol. To effect solution, the powdered nitrate is placed 
in a flask with a few drops of distilled water ; solution is pro- 
duced by gentle heat ; the alcohol is then added and the pre- 
cipitate first formed is re-dissolved by heat. This solution is 
added, drop by drop, to the given quantity of collodion. The 
apparatus shown in Figure 17 will be found very convenient 
for this purpose, as well as for others, when a finely divided 
emulsion is required. 

A and C are two flasks ; B is a cork, through 
which are passed two glass tubes as shown, the 
lower end of the tube projecting into the bottle, 
C, having been drawn to a point, and then filed 
off, thus leaving a small orifice. 

The collodion is placed in the lower flask, the 
silver solution in the upper. By vigorous shaking, 
the nitrate solution is made to pass, drop by drop, 
into the collodion, and in this way a very finely- 
divided emulsion is produced, which may be 
C tested by pouring a few drops on a glass, and ex- 
amining it by white light. If it shows a bluish 
FIG. 17. tint by reflected and an orange tint by trans- 
mitted light, the operation has been successful thus far. 




COLLODION EMULSION. 77 

The emulsion is now set aside in the dark for thirty-six 
hours, to settle and ripen. 

The next step is to test for silver nitrate, which must be 
slightly in excess. For this purpose, an ounce of distilled 
water is placed in a beaker glass, and a dram of the emulsion 
poured into it ; the mixture is well shaken, and then filtered 
twice, or until clear, through filter-paper. The addition of a 
few grains of common salt to the waste water will indicate 
the presence of free nitrate by a slight milkiness, due to the 
formation of chloride of silver. If no change in color is vis- 
ible, a sufficient .quantity of the alcoholic nitrate solution is 
added to the collodion, to produce a slight milkiness in the 
wash-water. 

In order to secure immunity from fog it is well to add at 
this stage to every ten ounces of emulsion two drams of the 
following cobaltic collodion : 

Alcohol 1 ounce 

Ether \% ounces 

Chloride of cobalt 60 grains 

Pyroxyline 12 grains 

The finished emulsion is next poured in a fine stream into a 
large quantity of water, with constant stirring. This precipi- 
tates the emulsion and removes from it most of the useless or 
harmful bye-products. The precipitate is washed in many 
changes of filtered water, and finally in one change of distilled 
water. It is then drained in a cloth and dried on several thick- 
nesses of blotting paper. When dry the resulting powder may 
be preserved indefinitely by placing in a clean bottle well 
wrapped in non-actinic paper. 

Be-emulsification. To make the final emulsion for coating 
the plates, 17 grains of the sensitive powder are dissolved in 
the following solution : 

Alcohol % ounce 

Ether ' Bounce 

Precipitated quinine 1 grain 

The precipitated quinine is made from common sulphate of 
quinine by dissolving it in sulphuric acid and precipitating 
with ammonia. 



78 THE PHOTOGRAPHIC NEGATIVE. 

The precipitate is first added to the alcohol, then filtered and 
the ether added, and lastly the sensitive powder. The mixture 
is allowed to stand for some hours in the dark, being occasion- 
ally shaken ; it is then filtered through cotton wool and used 
to coat the plates. 

Develop with any of the usual developers. 

These plates keep well, but are not more than one-half as 
quick as ordinary wet plates. 

Cooper's Process. 

THE PLAIN COLLODION. 

Alcohol 6 ounces 

Ether 10 ounces 

Pyroxyline, ordinary 160 grains 

THE EMULSION. 

a. Alcohol 5 ounces 

Bromide of zinc 400 grains 

b. Alcohol 3 ounces 

Nitrate of silver 150 grains 

Dissolve as recommended above. 

To make about ten ounces of emulsion add one ounce of a, 
and all of i, to three ounces of the plain collodion ; then add 
twenty drops of syrupy lactate of ammonia. The silver solu- 
tion should be at the boiling point when added to the collo- 
dion. The zinc solution will throw down a deposit after being 
kept, which must not be disturbed. 

The emulsion will ripen in twenty-four hours, but better 
results are obtained by allowing it to stand for three days ; then 
add twenty drops of strong nitric acid and shake well. 

Wash first in a very dilute solution of nitric acid, one-half 
an ounce of acid to one gallon of water, then in many changes 
of pure water, and dry thoroughly. 

When dry dissolve the pellicle in five ounces of alcohol and 
the same quantity of ether. 

The plates are first coated with the following gelatine sul> 
stratum : 

Gelatine 60 grains 

Water 8 ounces 

Chrome alum (10 grain solution) 2 drams 

The gelatine is swelled in cold water, well drained, and 



COLLODION EMULSION. 79 



enough boiling water added to make the bulk up to eight 
ounces. Then the alum solution is adde.d and the mixture well 
stirred for a few moments, and then filtered, avoiding air 
bubbles. This solution is flowed over the washed plates while 
still wet. Two coats are given, the first being drained away 
closely. The plates are then dried in an airy place, free from 
dust. 

The plates are coated with the emulsion, and when the films 
are set they are to be well washed ; a grooved negative washing- 
box answers well for this purpose. Wash until all signs of 
greasiness have disappeared, and then immerse for one minute 
in the following bath : 

Albumen, dried 60 grains 

Water 3 ounces 

Ammonia 1 dram 

Again wash well, flow over with a two-grain gallic acid pre- 
servative, drain and dry. 

These plates seem to possess indefinite keeping qualities, 
develop well with any good alkaline developer, and possess 
great latitude of exposure. They should be backed to prevent 
halation. A good backing is made as follows : 

Powdered burnt sienna . . 1 ounce 

Gum 1 ounce 

Glycerine 2 drams 

Water 10 ounces 

This is applied to the back of the plate with a stiff brush, 
and washed off with a damp sponge previous to development. 

Capt. Abney's Collodio-A Ibumen Emulsion. 
PLAIN COLLODION. 

a. Alcohol 4 drams 

Ether 6 drams 

Pyroxyline 16 grains 

BROMIDE SOLUTION. 

b. Bromide of zinc 16 grains 

Chloride of calcium 4 grains 

Alcohol 1 dram 

Add bromine water to impart a yellow tint. 

ALBUMEN SOLUTION FOR EACH HALF OUNCE OF COLLODION. 

c. White of egg 8 drops 

Alcohol... 1 dram 



80 THE PHOTOGKAPHIC NEGATIVE. 



Add the albumen in drops and stir well. 

First add b to #, and then drop in the proper quantity of c, 
and stir well. Then by the method given on page 76 add 
forty grains of nitrate of silver, previously dissolved in the 
smallest quantity possible of water and hot alcohol. 

The emulsion is then poured out into a shallow dish to set ; 
it is then washed as usual. Capt. Abney recommends covering 
it with a weak solution of nitrate of silver after the second 
washing, and then to continue the washing until the traces of 
silver are very faint. 

The pellicle should be re-dissolved in equal quantities of 
ether and alcohol, in the proportion of seven grains of the 
pellicle to each ounce of the mixed solvents. 

After being coated, the plates are well washed, flooded with 
a two-grain gallic acid preservative, and dried. 

These plates are more rapid than ordinary wet-plates, and 
can be developed with any of the alkaline or ferrous oxalate 
developers. 

Capt. Abney's Collodio- Chloride Emulsion, with Excess of 
Chloride. 

This emulsion can be used within a quarter of an hour of its 
preparation. The process is described in Captain Abney's own 
words. 

Weigh out the following : 

Pyroxyline, easily soluble 10 grains 

Pyroxyline, easily soluble 5 grains 

Chloride of calcium 20 grains 

Nitrate of silver 50 grains 

Dissolve the calcium in one-half ounce of alcohol, by warm- 
ing over a spirit-lamp. Place the five grains-of pyroxyline in a 
two-ounce bottle, and pour on it the alcohol containing the cal- 
cium. After a couple of minutes, add one-half ounce of ether, 
when the cotton will dissolve. 

Dissolve the 50 grains of silver in a test tube in 25 drops of 
water, and add to it one ounce of boiling alcohol and 'mix. 
Previous to this, the 10 grains of pyroxyline should have been 
placed in a four-ounce bottle, and the alcohol containing the silver 
should be poured in. Next add one ounce of ether, little by 



COLLODION EMULSION. 81 

little, with continuous shaking. Take the two bottles into a 
room lighted by yellow light, and gradually pour the chloride 
of calcium collodion into the nitrate of silver collodion. A 
test plate should now be coated, washed under the tap, and 
placed in the dark slide. The slide should be taken into 
white light and half the front pulled up for a second and then 
closed. The ferrous citro-oxalate developer given below should 
then be applied and the result noted. The film should show no 
blackening except on the exposed half of the plate. Should 
blackening take place, add two or three drops of a 20-grain 
solution of chloride of gold or cobalt to the emulsion and 
shake well ; the fog will then disappear. 

There seems to be no advantage in washing the emulsion. 
The coated plates are washed and then flooded once with 

Beer 5 ounces 

White sugar , 1 lump 

Pyrogallic acid 5 grains 

Or the two-grain gallic acid preserver may be substituted. 
These plates will be fonnd quite sensitive. 

They are developed with the ferrous citro-oxalate developer, 
prepared as follows : 

Citrate of potassium, neutral 100 grains 

Ferrous oxalate 22 grains 

Water 1 ounce 

First dissolve the citrate by heat, and, when nearly boiling, 
add the ferrous oxalate and shake well. 
A weaker form of the same developer is 

Citrate of potassium 50 grains 

Ferrous oxalate 12 grains 

Water 1 ounce 

These solutions keep well when corked in bottles. 

The plates are first rinsed in water, and then immersed in 
the developer. The image soon appears, and is of an ivory- 
black tone, well adapted to collodion transfers or positives on 
glass or paper. If a warmer tint is desired, tone with 

Nitrate of, uranium 10 grains 

Ferricyanide of potassium 10 grains 

Water . . 10 ounces 



82 THE PHOTOGEAPHIC NEGATIVE. 

Canon BeecTiey's Process. 

This is a very simple and reliable process. Plates made by 
it possess admirable keeping and technical qualities of about 
one-half the sensitiveness of average wet-plates. 

The following solutions are made up : 

1. BKOMIZED STOCK SOLUTION. 

Bromide of cadmium (anhydrous) 300 grains 

Alcohol (805) ' 8 ounces 

The solution is allowed to settle until clear. The super- 
natant liquid is then carefully decanted off, and one dram of 
hydrochloric acid is added. In this condition the solution will 
keep for years. 

2. COLLODION. 

Bromized solution Bounce 

Absolute ether 9 drams 

Pyroxyline 12 grains 

These ingredients are placed in a clean bottle and shaken 
until the pyroxyline is dissolved. The quantity given above 
is sufficient to coat one dozen whole plates. 

3. THE SENSITIZER. 

Nitrate of silver 40 grains 

Alcohol v . 1 ounce 

The best way of effecting solution is to pulverize the silver 
in a mortar. The powder is then placed in a test tube, the 
alcohol poured over it, and boiled until solution is effected. 
It is then poured in a fine stream into the collodion, with con- 
stant stirring. The emulsion is allowed to stand for twenty- 
four hours in a dark place, being occasionally shaken. It is 
then ripe enough for use, and should have a creamy appearance. 

The plates to be coated must first have been given a sub- 
stratum. Any of those given in Chapter IY. will answer. 
They are then coated as usual, and, when set, washed in pure 
water until all greasiness has disappeared. They are then im- 
mersed in the preservative stale beer thirty ounces, pyro 
thirty grains and dried as usual. 

Before coating, the emulsion should be well shaken and 
filtered. 



COLLODION EMULSION. 83 

Development Any good alkaline developer will work well 
with these plates. Before development the plates must be 
immersed in pure water to remove the preservative. 

DEVELOPERS FOK COLLODION EMULSION PLATES. 

Alkaline Developers. 

l. 

a. Pyrogallic acid 6 grains 

Water ... 1 ounce 

b. Bromide of potassium 20 grains 

Water 1 ounce 

c. Ammonia 1 ounce 

Water 32 ounces 

To develop : Take two parts of a, two parts of J, and one 
part of c. 

2. 

a. Pyrogallic acid 6 grains 

Alcohol 1 ounce 

b. Bromide of potassium 120 grains 

Water 1 ounce 

c. Carbonate of ammonium 80 grains 

Water 1 ounce 

Six drops of , three drops of 5, and three drams of c, 
form the developer. 

3. 

a. Carbonate of ammonium (pure) 10 grains 

Bromide of potassium 2 grains 

Water 1 ounce 

b. Pyrogallic acid 50 grains 

Alcohol 1 ounce 

One ounce of , and fifteen drops of b, form the developer. 
Ferrous-Oxcilate Developer. 

a. Ferrous sulphate 160 grains 

Water *. 1 ounce 

b. Oxalate of potassium (neutral) 1 ounce 

Water 3 ounces 

Add one part of a to two parts of b immediately before 
wanted for use. 



84 THE PHOTOGRAPHIC NEGATIVE. 

Hydrochinone Developer. 

a. Hydrochinone. . . 12 grains 

Sulphite of soda 60 grains 

Water 1 ounce 

b. Carbonate of soda 60 grains 

Water 1 ounce 

For the developer take two ounces of a, one ounce of b, 
and one ounce of water. 

This developer, although expensive, is recommended by the 
author for fine work, especially for positives on glass or paper, 
on account of the velvety blackness of tone and the clearness 
of shadows obtained by it. The hydrochinone solution will 
keep indefinitely; the mixed developer can be used to develop 
many plates, and the developer does not stain. 

Previous to development, the plates should be soaked in 
water or alcohol, as required, to remove the preservative. 
Gum or albumen preservatives dissolve only in alcohol. 
When the latter solvent is used, the plate must be washed in 
pure water until all repellent action has ceased. The devel- 
oper is then poured over the plate. If the image is Slow in 
appearing, pour off the developer and apply a new one con- 
taining less bromide, or add more of the alkaline solution. 

Intensify, if necessary, with the following : 

a. Pyrogallic acid 2 grains 

Citric acid .2 grains 

Water 1 ounce 

b. Nitrate of silver 20 grains 

Water 1 ounce 

Wash the plate well, and cover with a. Drop four or five 
drops of b into the graduate and pour the solution on the 
plate into it ; then return the mixture to the plate and allow 
it to act until sufficient density is reached. 

Defects. Those most commonly met with in collodion 
emulsion plates are the following : 

Black spots : due to dust settling on the film while drying. 

Crape markings : due, a, to the solvents of the emulsion 
being too aqueous ; 5, to failure to shake the emulsion before 



COLLODION EMULSION. 



85 



using it; or, c, to the bromide of silver being too coarse, 
owing to improper enralsification. 

Difficulty in flowing the emulsion : due to a deficiency in 
the solvents. 

The films leave the plates : the pyroxyline was too tough ; 
use a more powdery kind. 




CHAPTER IX. 

THE GELATINE PROCESS. 

Gelatine as a vehicle for the suspension of the sensitive salts 
of silver was recommended by Poitevin as early as 1850, but 
owing to the difficulty of obtaining it in the high state of 
purity necessary for photographic purposes, and the supposed 
greater facility and rapidity of manipulation possessed by col- 
lodion, Poitevin's suggestion found but little favor. 

Maddox, King, Burgess, and Kenneth, during the years 1871 
to 1874, published formulae in which gelatine replaced collo- 
dion as the vehicle of suspension, but it was not till Bennett, in 
1878, discovered the extreme sensitiveness conferred upon a 
gelatino-bromide emulsion, by digesting it at a high tempera- 
ture, that the new process met with favor among photograph- 
ers. From that time its advance has been rapid and continu- 
ous. Although the writer believes that it is a mistake to bring 
all photographic processes under the rule of the new claimant, 
he recognizes the immense advantages possessed by the gela- 
tine method, advantages which may well outweigh any defects 
inherent in it. 

It has been the custom to give the highest praise to the 
modern process on account of the extreme sensitiveness easily 
given to it. The writer, however, believes that its best claim 
for recognition is found rather on the artistic side. 

In the old collodion days the operator having to prepare hi& 
plates himself as he had occasion to use them was under the 
temptation of unduly magnifying the chemical aspect of hi& 
work and to neglect somewhat the artistic. 

But the advent of gelatine dry-plates has relieved the pho- 
tographer from the task of preparing his plates, and left him 
free to devote all his care and thought to the production of 
artistic results. Art is ever averse to manipulation, and now 
that the photographer is to a great degree emancipated from 
the manipulatory miseries inseparable from the collodion pro- 



THE GELATINE PROCESS. 87 

cess, he has the opportunity of becoming more of an artist of 
putting more of himself into his work. 

Without touching upon the many other advantages possessed 
by gelatino-bromide plates, the author now addresses himself 
to the pleasant task of explaining the details of the production 
of the plates and the development of the image. 

PREPARATION OF GELATINE EMULSIONS. 
General Observations. 

Theory of the Method. The preparation of the gelatino- 
bromide of silver consists essentially in forming a precipitate 
of bromide of silver in a warm solution of gelatine ; this pre- 
cipitate must be sufficiently fine to remain in suspension in 
the liquid in which it is produced ; it is then said to be in a 
state of emulsion. 

The sensitive bromide of silver is obtained by double de- 
composition, that is, by combining a soluble bromide with ni- 
trate of silver; the result of this combination is the formation 
of insoluble bromide of silver and an alkaline nitrate corres- 
ponding to the bromide employed. This nitrate must be re- 
moved by washing. 

It is necessary that the bromide be in excess in order to pre- 
vent fog and to regulate the action of the developing reagents. 
As a result of this there always remains in the emulsion a cer- 
tain quantity of undecomposed alkaline bromide, whic-h, unless 
removed by washing, would greatly lower the sensitiveness of 
the finished emulsion. 

The most common mode of washing is to allow the emulsion 
to set, then to break it up into small pieces and to wash for 
some hours in many changes of distilled or filtered rain water. 
During the washing the emulsion gradually gains in sensitive- 
ness, owing to the more complete removal of the alkaline ni- 
trate and bromide. Hence the greatest precautions should be 
taken against exposing the emulsion to the action of any light 
save when absolutely necessary, and then only for the shortest 
possible time. After the washing is completed, the emulsion 
is freed from all excess of water by draining, then melted with 
gentle heat, filtered, and flowed over the plates, which, after 
the film is set, are dried and stowed away for future use. 



88 THE PHOTOGKA.PHIC NEGATIVE. 

Time, temperature, and degree of alkalinity affect the sensi- 
tiveness of gelatino-bromide emulsions. 

At low temperature great sensitiveness is reached only after 
long digestion. If the temperature is raised to 100 deg. F. the 
same grade of sensitiveness is reached after five or six days. A 
temperature of 145 deg. F. will give the 1 same result within three 
or four hours. If the emulsion be kept at the boiling point, 
thirty minutes gives the maximum of sensitiveness. These 
conditions are changed if any addition is made with a view to 
produce a chemical ripening. Ammonia is often employed for 
this purpose. This produces an alkaline condition in the 
emulsion which thus reaches its maximum of sensitiveness after 
standing for some hours in a cool place. With this method it is 
not advisable to seek to hasten the ripening by employing heat. 

Choice of Soluble Bromides. The bromides of ammonium 
and potassium are the ones most commonly employed in the man- 
ufacture of gelatine emulsions. There is little choice between 
them. Emulsions prepared with one show little or no differ- 
ence from those prepared with the other. On this point Eder 
says that potassium bromide, owing to its stability, appears 
more suitable than the hygroscopic ammonium salt, which dis- 
colors under the action of light. Some operators use a mixture 
of the two salts, claiming superior results, a claim which 
numerous experiments of my own have failed to substantiate. 
Either of the two salts may be employed without necessarily 
prejudicing the quality of the resulting emulsion. 

In substituting one salt for the other it must be remembered 
that their combining weights are different, as shown in the fol- 
lowing table ; the combining weight of the potassium bromide is 
1 1 9, that of the ammonium is 98 ; hence one part of the former 
may replace 0*823 of the latter, or one part of the ammonium 
bromide may be replaced by 1'214 of the potassium salt. 

The principal bromides, chlorides, and iodides which are 
likely to be used in emulsions of either gelatine or collodion 
have been included in these tables. Table No. I. presents to 
the reader, without any mystification which may be involved in 
equivalents, the actual weights of haloid or silver, as the case 
may be, required to convert or combine with one grain of the 
other. 



THE GELATINE PROCESS. 



TABLES FOR THE SIMPLIFICATION OF EMULSION CALCULATIONS. 
No I. 







i c -D 


^ g 


2*0 


o *> 


T3 C 




e/3 


" 0*3 





2. c 


,2 o'-o 


11 




Js 




"c3 j 


C-cj ;* 


^ '3 


CO tJD 




tj 


O "43 


C S i 


"^ fe'O 


-C fj t 


* 




*3 




JJ >O 


1 sl 


lit 


* c 




<L> 


VM "O 

2 M 


pf 


5|i 


**M ^ 


s^ 




*D 


t^ o 


_r2 ^ hr 


^ o ^ 


^ QJ gj 


43 ^ 




8 


bpo> c 

D-g'g 

^crbo 


|! 


' 5 1 

^ 0. 


||1 


s| 








l!_ 








Ammonium bromide 


98 


1-734 


576 


1-918 


521 


] 


Potassium bromide 


119*1 


1-437 


*700 


1-578 


633 




Sodium bromide 


103 


1-650 


606 


1-825 


548 




Cadmium bromide, com 


172 


988 


1-012 


1-093 


915 


{1-106 


Cadmium bromide, anh 


136 


1-25 


800 


1-382 


723 




Zinc bromide . . . 


112-1 


1-509 


663 


1-670 


600 




Ammonium chloride ..... 


53-5 


3*177 


315 


2-682 


373 




Sodium chloride 


58.5 


2-906 


344 


2-453 


408 


^ 

844 


Ammonium iodide 


145 


1-172 


853 


1-620 


617 




Potassium iodide . . 


166-1 


1-023 


977 


1-415 


'707 


1 


Sodium iodide 


150 


1-133 


882 


1-566 


638 


L 1-383 


Cadmium iodide . . . 


183 


929 


1-076 


1-284 


778 
















J 



In order to test the utility of this table, let us suppose that 
it is desired to make (say) ten ounces of emulsion by a new 
formula, which, for the saKe of showing the working of the 
table, we write down as follows : 

Bromide of potassium 150 grains 

Iodide of Potassium 10 grains 

Chloride of ammonium 10 grains 

Gelatine 200 grauis 

Now we want to know how much silver nitrate should be 
employed in sensitizing this mixture. For this purpose we 
use the first column, in which we find against each haloid the 
exact quantity of silver nitrate required to fully decompose one 
grain. Taking, then, the figures we find in column No. 1 
against the three salts in the above formula, and multiplying 
them by the number of grains of each used, we have the fol- 
lowing sum : 



Potassium bromide 150 X 1'427 = 214 

Potassium iodide 10 X 1*023 = 10'23 

Chloride of ammonium. .. 10 X 3*177 = 31*77 



Weight 

silver nitrate 

required. 



or the total quantity of silver nitrate required for full conver- 
sion, 256*00 grains. 



90 



THE PHOTOGRAPHIC NEGATIVE. 



Cadmium 
Iodide. 


10 

? 





CO 




? 


5 
t- 


B 


i 


05 
CO 



i> 


i 


OS 
00 


v* 


Sodium. 
Iodide. 


1 


1 


i 


(O 


I 


to 
t- 


s 

CO 


C5 
CO 


1 


1 


1-1 


P 


Potassium 
Iodide. 


OS 


t- 
t- 


p 


! 


~ 

S 


i 


1 


I 


co 




i-i 


i 


1 


Ammonium 
Iodide. 


o 


1 





l 


QO 

P 


s 


1 


co 

> 


r^ 


i 

-j< 


1 


! 


Sodium 
Chloride. 


1O 


1 
<N 





^ 



<N 


! 


* 

cs 


- 


1 

jq 


e 

00 
O} 


i 

CJ 




CO 


Ammonium 





1 





i- 
? 





3 


1H 





01 

r^ 


s 




oo 


o 

^ 




1-H 


<M 


1-H 


e3 


0> 


<M 




TH 


e 


CO 


20 


co 


Zinc 
Bromide. 


t~ 

9> 


! 


>O 

5s 


! 


! 


<H 


1^1 
t- 


Oi 

o 


S5 

C4 


1 


Ci 



T^H 


! 


Cadmium 
Bromide. 
(Anhyd.) 


o} 
t- 


I 


g 




o* 


rH 


g 

00 


I 


cc 
T 1 


! 


1 


CO 

o 


o 

i 


Cadmium 
Bromide. 
(Coml.) 





I 


I 


<-< 


? 


i 


5o 


s 


CO 
QO 


1 




QO 


! 


Sodium 
Bromide. 


1 


i 


<H 


6 


P 


CO 

8 


OS 


oo 

<g 


3D 

i 


OJ 

s 


! 


g 


Potassium 
Bromide. 


i 


*4 


I 


1 


^T 


i- 


os 


? 


t- 

? 


! 


s 



! 


Ammonium 
Bromide. 


^H 


1O 




S 

o 


p 


i 


OS 


CO 

*p 


i 


1 


o 

o 





c- 

s 






































































* 












B 











x: 
e 
cfl 




6 














Ammonium bromi 


Potassium bromid 


Sodium bromide . 


Cadmium bromide 


Cadmium bromide 


Zinc bromide 


Ammonium chlori 


Sodium chloride.. 


Ammonium iodid< 


T3 

-5 
o 

E 

3 

rt 

O 

CU 


Sodium iodide. . . 


Cadmium iodide. 



THE GELATINE PROCESS. 91 

Table No. II. gives in separate columns the relative convert- 
ing values of each of the soluble haloid salts in ordinary use, 
showing how much of any salt must be used to replace one 
grain of any other. In each column will be found an unit 
(printed in larger type) which represents one grain of the salt 
named at the head of the column ; the other figures in the 
same column show the exact quantities of the other salts which 
must be used in lieu of a single grain of that particular haloid. 
Thus, taking the first column, which is headed " Ammonium 
Bromide," we find against ammonium bromide in the margin 
the figure 1, representing one grain of that salt. If we wish to 
know the relative converting power of potassium bromide we 
take the number in the same column which stands against the 
latter salt in the margin, viz., 1/215 ; that is to say, 1/215 grain 
of potassium bromide will be required to do the same work as 
one of NH 4 Br. 

Choice and Treatment of the Gelatine. The gelatine em- 
ployed must have been prepared especially for photographic 
purposes, and a supply both of the hard and the soft varieties 
should be kept on hand. An emulsion prepared with a mix- 
ture of both hard and soft gelatines gives better films than one 
in which either the hard or the soft alone was used. In win- 
ter, equal proportions of the two should be used; in summer, 
the proportion of the hard variety should be increased to two- 
thirds of the total amount employed. 

The gelatines manufactured by Cox, Nelson, Coignet, Hein- 
rich or Simeon will be found the best. Even when the best 
gelatines are employed, the operator will often be troubled with 
grease spots in his films; to avoid this danger the author 
recommends that the gelatine solution be purified in one of 
the following ways: 

To each thirty-five ounces of gelatine solution add the white of 
one egg beaten to a froth. Mix well and boil for fifteen minutes 
in a water bath. The albumen, coagulated by the heat, frees 
the gelatine from all impurities. When cooled down to 100 
deg. the liquid is filtered. This method removes all danger 
from grease spots, but when the nitrate of silver is added to a 
gelatine solution thus treated, a precipitate is formed which 



92 THE PHOTOGRAPHIC NEGATIVE. 

must be removed by decantation. Another equally good 
method is to soak the gelatine, cut up in shreads, for an hour 
in a one per cent, potassium bromide solution, and then wash 
in three or four changes of water. Excess of water is then 
removed by squeezing the gelatine wrapped in a piece of clean 
muslin. The mass is then weighed, and the difference in 
weight between the dry and the wet gelatine is deducted from 
the amount of water directed to be added to form the emul- 
sion. It is well to test the gelation solution with litmus paper. 
If it shows an acid reaction, neutralize with ammonia ; if alka- 
line, neutralize with a few drops of a ten per cent, nitric acid 
solution. In this case do not add the acid indicated in the 
formulae. 

Proportion of the Ingredients. Great diversity exists in 
the proportions used of the various ingredients used in making 
an emulsion. The following table gives an average computed 
from the comparison of many formulae. 

Water 1 ounce 

Bromide of ammonium 15 to 20 grains 

or, 

Bromide of potassium 18 to 25 grains 

Nitrate of silver, proportioned to the amount 

of bromide 25 to 30 grains 

Gelatine 30 to 40 grains 

The proportion of gelatine varies according to its nature and 
the temperature. In summer more, in winter less. 

The amount of emulsion required to coat the plates is not 
constant ; from four to five drams for a whole plate is about 
right. 

Emulsifying. To dissolve the gelatine and to make the 
emulsion, it is best to use a hot water-bath, and to place the 
emulsion in a clean glass or porcelain flask capable of with- 
standing heat and sudden changes of temperature. For ex- 
perimental work on a small scale very simple arrangements 
will suffice ; a tin pail, an old coffee pot, or any similar vessel 
with a tightly fitting cover, will answer for the water bath, and 
the emulsion may be placed in a stout bottle, a porcelain cap- 
sule, or a Bohemian glass of suitable shape and size. But for 



THE GELATINE PROCESS. 



93 



more ambitious attempts something more elaborate must be 
devised. The writer knows of nothing better than one of the 
two arrangements figured and described below. The first, 
shown in Fig. 18, is a somewhat elaborate emulsifying apparatus 
recommended by David and Scolik, and is well adapted for 
work on a large scale. 

Fig. 19 shows the apparatus devised by M. Davanne, and 
it is the best with which the writer has experimented, as it 
combines in itself all the requirements of emulsifying, filtering 
and washing. 




FIG. 18. 

The essential parts of this apparatus consist of the lamp, F, 
the sheet-iron covering, A, and the cover, B. The lamp can be 
filled and the flame regulated from the outside as shown in 
the cut. D is a small window of ruby glass through which the 
flame can be seen. A is the water- bath in which the vessel 
containing the emulsion is placed. It is provided with a dou- 
ble bottom. B is the cover, closed at the top with a small bent 
pipe soldered in to allow the steam to escape. This cover must 
fit light-tight over A. This is easily effected by soldering a 
small gutter-shaped trough around the top of A, into which the 
bottom of B fits. By filling this trough with small shot a 
light-tight joint is made. 

The dimensions of the various parts will depend upon the 
quantity of emulsion to be cooked. I have had no experience 
with this apparatus, but it is theoretically good, and should 



94 THE PHOTOGRAPHIC NEGATIVE. 

work well if properly constructed. A very good substitute 
for it is found in the infants' food- warmer, to be had of most 
druggists, which consists essentially of a covered porcelain jar 
resting in a metallic water-bath, the water in which is heated 
by means of a candle placed underneath. 

Fig. 19 illustrates M. Davanne's ingenious apparatus. 




FIG. 19. 



It is simply a common steam cooker somewhat modified to 
adapt it to its new use. A is the hot water receptacle ; B, fit- 
ting tightly 'over A, contains the vessel in which the emulsion 
is placed ; d, d, are two small tin tubes soldered into B, which 
serve to convert the apparatus into a convenient washing ar- 
rangement. To construct the apparatus the perforated bottom 
is removed from B, leaving a margin of one-quarter of an incli 
around B to receive the movable plates used in the different 
operations. The portion removed is used as a false bottom in 
A to prevent breakage of the various flasks which may be placed 
there. Its place in B is filled by a movable plate, F, pierced 
with holes. On this plate all the preparations are placed which 
are to be heated with steam instead of warm water. 

Three or four other metal plates are provided, of the form 
shown at E, with various sized openings. These are intended to 



THE GELATINE PROCESS. 95 

hold funnels for warm filtration, or flasks containing solutions, 
the temperature of which requires careful watching. 

The following description will demonstrate the great adapta- 
bility of this simple piece of apparatus : 

Cooking the Emulsion. The flask containing the emulsion 
is placed on the false bottom, the cover is put on and the tubes 
d, d, closed with corks, and the water brought to the proper 
temperature ; or the flask is placed on the perforated bottom of 
B, and the emulsion cooked by steam. 

Filtering. The filter is placed in one of the metallic plates, 
E, in such a way that it is nearly introduced into B, a flask is 
placed beneath it, and the water is heated ; the heat thus pro- 
duced is sufficient to prevent the emulsion from closing the 
pores of the filtering medium. 

Washing. The shredded emulsion is placed in a wide- 
mouthed flask fitted with a cork, through which pass two glass 
tubes, one reaching nearly to the botton, the other only a few 
inches; the tubes d, d, are closed with corks carrying glass 
tubes which are connected with the tubes in the flask by means 
of black india-rubber piping. The tube thus attached to the 
longer tube in the flask is connected with the tap by rubber 
piping. The writer confidently recommends this apparatus to 
all experimenters as a most convenient and compact arrange- 
ment. 

Filtration. All emulsions must be filtered before the plates 
are coated. To effect this in the case of emulsions containing 
gum or gelatine, it is often necessary to resort to the method of 
warm filtration to prevent the pores of the filtering medium 
from being closed. Small quantities of emulsion are easily 
filtered through a clean lamp chimney, around the top of which 
two or three thickness of clean linen have been tied. Another 
good method, as it avoids air bubbles, is the method of upward 
filtration already described. 

For large quantities of emulsion, however, some means of 
keeping the emulsion warm during the process of filtration 
must be resorted to. Figs. 12 and 13 (page 19) illustrate two 
very efficient arrangements for warm filtration. There is 
little choice between them, both being constructed on the 



96 



THE PHOTOGRAPHIC NEGATIVE. 



same principle. To avoid air bubbles, it is well to bring the 
tube of the funnel in contact with the side of the vessel into 
which the emulsion is to be filtered. 

If Davanne's apparatus is used, neither of these latter will 
be needed. 

Silvering. In order to produce the bromide of silver in the 
extremely fine state of division necessary to give good results r 
it is imperative that the nitrate solution be added slowly to 
the emulsion. A simple means of effecting this is to add the 
silver in small quantities, and to shake well after each addition. 
Another, and perhaps a better, is to pour the silver solution into 
the emulsion in a fine stream with constant stirring. A good 
stirrer is made by fastening a strip of glass across the end of 
a glass rod with a piece of clean twine. A rotary motion is 
imparted to the rod by twirling it between the thumb and fore- 
finger. 

An ordinary glass funnel is easily adapted for silvering pur- 
poses, by inserting a clean cork in the lower end of the tube 
and boring a small hole through it. 

A spray apparatus is also very efficient for this purpose. 
Fig. 20 shows a form which is easily constructed. 

Two thin glass tubes are 
bent in the shapes shown 
at A and B. The tube, A r 
is drawn to close the bore. 
A flat file is then used to 
file away the point, leaving 
a very small orifice. The 
two tubes are then fitted 
into a cork which is placed 
in a test tube, as shown in 
the figure. The silver nit- 
rate is placed in the test 
tube, the cork inserted, and a fine spray of liquid is forced 
out by blowing through the tube, B. The handiness of the 
apparatus is increased by adapting to B, with a piece of rubber 
tubing, a rubber ball provided with a valve. 

The silvering apparatus shown in Fig. 17 is also very efficient. 




FIG. 20. 



THE GELATINE PROCESS. 



97 



Digesting the Emulsion. The vessel containing the emul- 
sion is placed in the water-bath, which is brought to the re- 
quired temperature. If the emulsion is to be boiled, a bent 
glass tube should be inserted in the cork which closes the flask. 
Breaking Up and Washing* After digesting the proper 
length of time, the emulsion is allowed to set, by pouring it out 
into a clean shallow tray. When well set it is cut up into 
narrow strips with a clean ivory paper cutter ; the strips are 
then placed in the center of a square of working canvas, pre- 
viously soaked in a solution of carbonate of soda and well 
washed, and squeezed out into a deep dish full of clean 
water. The washing can be done in a variety of ways. The 
simplest is to wash in many changes of water, stirring the 
emulsion well after each change, and allowing it to settle be- 
fore decanting the water. If this method be adopted a double 
tubed decantation flask will be found very convenient ; a 
piece of clean muslin is tied over the small tube and the 
emulsion introduced through the large one. It is well ta 
squeeze the emulsion through the canvas once more when 
half washed. A half hour's washing in this way will proba- 
bly eliminate all the soluble salts. 

Capt. Abney has recommended the 
following very simple washing appa- 
ratus, the use of which makes it possi- 
ble to wash the emulsion in full day- 
light. Fig. 21 makes its construction 
sufficiently evident. A hole is perfor- 
ated in the lid of a tin canister of 
sufficient size to admit a glass tube, C. 
This tube is connected with the water- 
tap by a piece of well-washed black 
inclia rubber piping. A spout, D, is 
soldered to the canister. To prevent 
the emulsion from being carried over 
the top of the flask, a piece of muslin 
is tied over its mouth around the glass tube. 

The method of converting Davanne's cooker into a washing 
apparatus has already been given. 




98 THE PHOTOGRAPHIC NEGATIVE. 

When the washing is nearly completed a small quantity of 
the wash-water is placed in a glass and a few drops of a neu- 
tral solution of nitrate of silver are poured in. If the mix- 
ture examined by white light shows no coloration the washing 
is sufficient. 

Draining, When the emulsion is sufficiently washed it is 
drained to remove the excess of water. A hair-sieve may be 
used for this purpose, or a piece of linen or open-meshed can- 
vas tied over the top of a large earthen vessel. The emulsion 
should be allowed to drain two hours. At the end of that 
time it will be well to pour a few ounces of alcohol over the 
mass. 

Re-melting. The emulsion is re-melted in the water-bath at 
a low temperature ; during this process the emulsion should 
be stirred occasionally. When dissolved it is ready for filter- 
ing. 

FORMULAE FOR EMULSIONS. 
Andrei's. Weigh out the following : 

Bromide of ammonium 138 grains 

Nitrate of silver , 208 grains 

Gelatine 310 grains 

Dissolve the ammonium salt in five ounces of water, and 
add 138. grains of the gelatine cut up into shreds. As soon as 
the gelatine has swelled, dissolve in the water-bath. 

While this is taking place, dissolve the silver in two and a 
half ounces of water, with gentle heat. While both solutions 
are warm, add the silver solution to the gelatine by any of the 
methods indicated above. This and the following operations 
must be carried out by ruby light. 

The silvered emulsion is to be kept at the boiling point for 
thirty minutes, or until a few drops of it, spread on a strip of 
glass, is blue by transmitted light. Allow it to cool down to 
about 1 20 deg. and then add eighty-one grains of shredded 
gelatine previously swelled in cold water. When the gelatine 
is dissolved add two drams of a two per cent, bichromate of 
potash solution ; mix well, and pour out into a clean porce- 
lain tray to set. When set the emulsion is cut into shreds, 



THE GELATINE PROCESS. 99 

squeezed through canvas, and washed. It is then drained, 
eighty-one grains of swollen gelatine added and dissolved by 
gentle heat, and poured out as before to set. When the 
emulsion is set it is covered with alcohol and allowed to ripen 
for eight days. It is then melted, filtered, and spread over 
the plates. 

Henderson ' Ammonia Method. 
In 

Distilled water 8^ ounces 

dissolve 

Bromide of ammonium 308 grains 

Gelatine (previously swelled) 50 grains 

When cold add 

Water 1% ounces 

Alcohol 1% ounces 

Strong ammonia 4 drams 

In 

Distilled water , 3}^ ounces 

dissolve by heat 

Nitrate of silver. 462 grains 

and add gradually to the first solution. 

An emulsion thus prepared lacks sensitiveness. This is 
produced by allowing the emulsion to ripen for twenty-four 
hours ; under the alkaline conditions present sensitiveness is 
conferred in this simple way. At the end of twenty-four 
hours 220 grains of swelled gelatine are added and dissolved 
by gentle heat. Then proceed as above. 

Eder's Ammonio-Nitrate of Silver Method. 
In 

Distilled water 4 ounces 

dissolve 

Bromide of potassium 310 grains 

add 

Gelatine 617 grains 

previously swelled in water. 

In 

Distilled water 4 ounces 

dissolve 

Nitrate of silver 462 grains 



100 THE PHOTOGRAPHIC NEGATIVE. 

To this solution, cold, add strong ammonia, drop by drop, 
until the precipitate first formed is re-dissolved. 

Add this gradually to the first solution, and place in a water- 
bath at a temperature of 105 deg. Kemove the source of heat 
and allow the emulsion to cool down gradually to about 75 deg., 
then pour out to set, and proceed as usual. For plates of mod- 
erate sensitiveness the author prefers this method to any others 
with which he has experimented. 

Brauris Method. 
In 

Distilled water 4 drams 

dissolve 

Bromide of ammonium 964 grains 

add 

Gelatine 92 grains 

previously swelled in 

Distilled water 19 ounces 

dissolve 

Nitrate of silver 1,543 grains 

and add to the first solution ; after a few minutes add 

Strong ammonia. 12 drams 

and stir well. 

For plates of medium rapidity digest for six hours at a tem- 
perature of 95 deg. When great sensitiveness is desired digest 
for twelve hours at the same temperature. 

As soon as the digestion is finished, turn the emulsion out 
into a three-gallon earthen jar containing half a gallon of dis- 
tilled water. Put on the cover and allow it to stand for four 
days if it was digested for twelve hours, and six days if digested 
six hours. By this time all the sensitive bromide of silver will 
have deposited. The water is then decanted and 1,235 grains 
of gelatine, swelled in 39 ounces of water, are added to the 
bromide, and well stirred. The mixture is melted at a tem- 
perature of 105 deg. As soon as the gelatine is dissolved, the 
emulsion is filtered and used for coating the plates. 



THE GELATINE PROCESS. 101 

This method gives clean plates, which yield crisp, brilliant 
negatives, of great clearness in the shadows. 

Scolitts Ammonio- Nitrate of Silver Method. 

In 

Distilled water 17^ drams 

dissolve 



Bromide of ammonium 308 grains 

Bromide of potassium 370 grains 



and add 



Iodide of potassium solution (1 to 10) 2 to 3 drams 

Hard gelatine 704 grains ) . . 

Soft gelatine 704 grains [ m wmter 

or, 

Hard gelatine 1,003 grains } . 

Soft gelatine .400 grains p n summer 

Allow the gelatine to soak for half an hour in 

Distilled water 17% drams 

dissolve 

Nitrate of silver 926 grains 

Add ammonia, drop by drop, to re-dissolve the precipitate 
first formed, stirring well. 

Dissolve the gelatine in the water-bath at a temperature of 
150 deg. Then, in the dark room, add the silver solution in a 
fine stream, with constant stirring. Replace the emulsion in 
the water-bath for half an hour, the source of heat being with- 
drawn. At the expiration of this time the emulsion is poured 
out to set. 

Scolitfs Modification of Henderson's Cold Emulsion 
Method. 
In 

Distilled water 38 drams 

dissolve at 120 deg. 

Soft gelatine 45 to 60 grains 

add 

Citric acid 15 grains 

when dissolved add 

Carbonate of ammonia 108 grains 

Bromide of ammonium 694 grains 

Iodide of potassium solution (1 to 10) 2 drams 



102 THE PHOTOGRAPHIC NEGATIVE. 

When these salts are dissolved add a mixture of 

Alcohol ......... .............................. 13 ounces 

Ammonia ..................................... 4% drams 



In 

Distilled water .................................. 9% ounces 

dissolve 

Nitrate of silver ................................ 925 grains 

Add this to the bromized solution as usual, cork the flask 
tightly to prevent the escape of ammonia fumes, and set aside 
for twenty-four hours to ripen. Then add 1,000 grains of soft, 
and 300 grains of hard gelatine, and dissolve at a temperature 
of 95 deg. Set, wash, and filter as usual. 

Davannds Method. 
In 

Distilled water ................................. 12% ounces 

swell, dissolve, and filter 

Soft gelatine .................................... 925 grains 

In 

Distilled water ................................. 5% ounces 

dissolve 

Bromide of ammonium .......................... 262 grains 

add 

Gelatine solution ............................. ,-3% ounces 

In 

Distilled water .................................. o% ounces 

dissolve at 85 deg. 

Nitrate of silver .................................. 416 grains 

and add to the bromized solution as usual. 

This gives an excellent slow emulsion, with the addition [of 
3 ounces of the gelatine solution. To increase sensitiveness. 
boil for half an hour, and then add 

Gelatine solution ............................... 3% ounces 

Bichromate of potassium solution (2 per cent.). . . .3 drams 



THE GELATINE PROCESS. 103 

Burton's Precipitation Method. 
In 

Distilled water 1% ounces 

dissolve 

Bromide of ammonium 120 grains 

Iodide of ammonium 10 grains 

Add 

Soft gelatine 30 grains 

swell and dissolve at 95 deg., and add 

Hydrobromic acid 1 drop 

In 

Distilled water 1% ounces 

dissolve 

Nitrate of silver 212 grains 

and add to the bromized solution in a fine stream. 

Boil for thirty minutes ; cool down quickly to about 60 deg., 
and then pour the emulsion in a fine stream into a clean dish 
containing eight ounces of alcohol. In a few seconds the emul- 
sion precipitates ; it is then washed by decantation in a few 
changes of water, after which it is added to the following 
solution : 

Soft gelatine 120 grains 

Hard gelatine 150 grains 

Distilled water 12 ounces 

The mixture is well shaken to effect solution ; the emulsion 
is then filtered and used for coating. 

This method has many points to recommend it. The plates 
are of the best quality, and yield plucky negatives. The bro- 
mide of silver precipitate may be prepared, dried and pre- 
served indefinitely, and the tedious operations of prolonged 
washing and draining are done away with, since a few changes 
of water serve to eliminate the last traces of the soluble salts 
from the precipitated bromide. 

Fabre's Method. By this method the sensitive bromide of 
silver is produced directly by macerating in a mortar the proper 
proportions of bromide of silver and sulphate of potash. By 
the addition of a few drops of distilled water, long, needle-like 



104 THE PHOTOGRAPHIC NEGATIVE. 

crystals are formed ; the addition of a slight excess of water 
destroys this combination and produces the sensitive modifica- 
tion of bromide of silver, which may then be emulsified with 
gelatine as usual. 

This method does away with washing, draining, and the use 
of alcohol ; and some few experiments made with emulsions 
so prepared indicate remarkably fine qualities in the plates. 
To form the sensitive salts, mix intimately in a mortar one 
part of bromide of silver and two and one-fourth parts of sul- 
phate of potash ; then add of distilled water, drop by drop, 
not more than one-tenth of the weight of the bromide. The 
first combination is formed within five minutes. A slight 
excess of water is then added ; this destroys the former com- 
bination and forms the sensitive salt, which, after two or three 
washings, may be dried and preserved for future use, or incor- 
porated immediately with a gelatine solution. The emulsion 
is made up as follows : 

Distilled water 3% ounces 

Sensitive bromide 77 grains 

Gelatine 45 to 75 grains 

Boil till a trial film is blue by reflected light. 

Some operators prefer to add the nitrate of silver to the 
bromized solution in large crystals. 

The following formulae and explanations are given to illus- 
trate this method, which gives results equal to the best. 

In 

Distilled water 5 ounces 

dissolve 

Bromide of potassium 164 grains 

Iodide of potassium. . .... 20 grains 

Add 

Soft gelatine 80 grains 

Allow the gelatine to soak for fifteen minutes, and then dis- 
solve at 120 deg. 

In a strong bottle place 

Nitrate of silver 232 grains 

Heat both vessels to 140 deg., then add the crystals of silver 
to the bromized gelatine and shake vigorously till the silver is 



THE GELATINE PROCESS. 105 

dissolved. Boil for thirty minutes, then cool down to 100 
degrees. 
Add 

Hard gelatine 180 grains 

Soft gelatine 100 grains 

Water to cover. 

Soak fifteen minutes. 

Stir well until the gelatine is dissolved, and add 

Strong ammonia 1 dram 

and stir vigorously. Pour out to set. 

Burton's Method for a Very Slow Emulsion. 

In 

Distilled water 3 ounces 

dissolve 

Bromide of potassium 160 grains 

Iodide of potassium 10 grains 

Soft gelatine 40 grains 

Soak the gelatine for fifteen minutes before dissolving; 
when dissolved, add 

Hydrochloric acid 2 drops 

111 

Distilled water 3 ounces 

dissolve 

Nitrate of silver 200 grains 

Heat both solutions to 120 cleg., and add the nitrate gradu- 
ally to the gelatine with constant stirring. 
After ten minutes, pour the emulsion over 

Hard gelatine 150 grains 

previously swelled in cold water and all excess of water re- 
moved by pressing in a cloth. Heat until dissolved, and set 
aside to set. Then break up, wash, and add 

Hard gelatine 150 grains 

treated as before. Melt, and add 

Alcohol . . 4 drams 

Filter and coat. 



106 THE PHOTOGRAPHIC NEGATIVE. 

Gelatino- Chloride Emulsion for Slides and Transparen- 
cies. 

In 

. Distilled water 7 ounces 

dissolve 

Chloride of sodium 108 grains 

Gelatine 310 grains 

In 

Distilled water 3^ ounces 

dissolve 

Nitrate of silver 231 grains 

Heat both solutions to 120 deg., and add the nitrate to the 
gelatine. 

Pour out to set at once. 

Wellington's Citro- Chloride Emulsion for Opah. 

In 

Distilled water 3 ounces 

dissolve 

Chloride of sodium 20 grains 

Bromide of potassium 40 grains 

Citric acid 100 grains 

Soft gelatine 40 grains 

In 

Distilled water 3 ounces 

dissolve 

Nitrate of silver 100 grains 

Citric acid 100 grains 

Heat both solutions to 150 deg., and add the nitrate to the 
gelatine. 
Then add 

Hard gelatine (swelled) 200 grains 

and stir until dissolved. Then pour out to set. 

These plates are best developed with the ferrous oxalate 
developer, modified with chloride of ammonium and citric 
acid, as described in the chapter devoted to development. 



THE GELATINE PROCESS. 107 

Sczekely's Process with Carbonate of Silver. 
The following solutions are made up : 
1. In 

Distilled water 45 drams 

dissolve 

Nitrate of silver 261 grains 

2. In 

Distilled water 45 drams 

dissolve 

Bicarbonate of soda 154 grains 

3. In 

Distilled water 45 drams 

dissolve 

Bromide of ammonium 154 grains 

Gelatine 340 grains 

Solution No. 2 is boiled, and then added to No. 1. The 
precipitate of carbonate of silver thus formed is well washed 
and thrown on a filter. When the bulk of the liquid has run 
through, the wet precipitate is placed in a beaker and its 
bulk made up, if necessary, to 4:5 drams. Strong ammonia is 
then added, until a clear solution is obtained. 

This solution is poured gradually and with constant stirring 
into solution No. 3. The bottle is rinsed out with 5 drams 
of distilled water, which is added to the emulsion, which is 
then filtered into the funnel, from which it runs in a fine 
stream. The emulsion must be kept constantly stirred. 

Sensitiveness is given to the emulsion by digesting it from 
one to two hours at a temperature of 100 deg. 

All of the operations preceding the addition of the silver 
solution to the bromized gelatine may be performed in diffused 
white light. 

The author finds that this process gives negatives rich in 
detail and gradation, and free from fog. 

While the above formulae are very far from exhausting the 
long list of gelatine emulsion formulae, they are sufficient to 
meet all the possible needs of the photographer, and with 
proper precautions they are all reliable, and have stood the 



108 THE PHOTOGRAPHIC NEGATIVE. 

test of practical experience. The writer's aim has been to 
give one typical formula of each class, and he has selected 
those which his own experience has proved to be best adapted 
to the special class of work for which they were designed. 

Collodio- Gelatine Emulsions. The great drawback to the 
preparation, in small quantities, of gelatino bromide plates by 
amateurs has been the somewhat difficult operation of coating, 
and the need of efficient drying arrangements. 

To obviate these difficulties many experiments have been 
made to produce emulsions combining the rapidity of the or- 
dinary gelatine emulsion with the ease of coating of collodion. 
The aim of most of these experiments has been to combine 
pyroxyline with the gelatine emulsion. Under the usual con- 
ditions this is impossible, since the solvents of pyroxyline pre- 
cipitate gelatine from an aqueous solution. 

To Dr, H. W. Vogel belongs the credit of being the first 
to overcome this difficulty, and to produce a combined emul- 
sion easy to coat with, and of good working qualities. 

His method is to prepare a gelatine emulsion as usual, and 
after washing to dry it by spreading it out on clean blotting- 
paper where it is allowed to dry spontaneously. 

The dried pellicle is dissolved by heat in three to ten times 
its weight of acetic acid, the quantity of acid varying according 
to the kind of gelatine used in making the emulsion. Enougli 
alcohol is then added to make it flow well at a temperature of 
90 deg. 

Plates may be coated with the emulsion in this condition, 
but, in order to give greater tenacity, Dr. Vogel recommends 
the addition of an equal quantity of a collodion made as 
follows : 

Pyroxyline 20 grains 

Glacial acetic acid 1 ounce 

Alcohol 1 ounce 

Another method recommended by Dr. Vogel is to prepare 
a collodion emulsion, any of those described in Chapter VII. 
will answer. This emulsion is washed and dried. Seventy 
grains of the pellicle are dissolved in three ounces of alcoliol 
and one and three-quarter ounces of acetic acid. Twenty 



THE GELATINE PROCESS. 109 

grains of plain gelatine are dissolved in three and a half drams 
of acetic acid and added to it. The emulsion is then ready 
for coating. 

KosarzewnkV s Method. 

Alcohol 2 ounces 

Glacial acetic acid 2 ounces 

Pyroxyline 18 grains 

One hundred and eighty grains of gelatine emulsion are 
added and dissolved by heat. 

Plates which are to be coated with any of these emulsions 
must first receive a very tenacious substratum, the albumen 
and silicate of soda substratum answers well. 

The emulsion is flowed over the plates like collodion, 
the plates are drained, and then rocked gently to prevent the 
formation of ridges. 

These plates may be developed by any of the methods de- 
scribed in Chapter XI. 

The great advantage of this form of emulsion is that it may 
be kept in a bottle and used for coating plates as wanted. 

Sensitiveness seems to be a trifle diminished, but the plates 
yield good results. 




CHAPTER X. 

COATING THE PLATES. 

The Levelling Shelf. Some means must be provided in the 
coating-room for keeping the plates perfectly level while setting. 
The most common practice is to use a glass, stone, or marble 
slab of suitable size. This is levelled by means of thin hard- 
wood wedges, or by levelling screws of the form shown in 
Fig. 22. The top screws- into the base. By providing a 
supply of these, and a number of plate-glass slabs, a large 
number of plates may be placed to set on these slabs levelled 
one above the other, and left to dry in the coating-room, which 
must be light-tight, well ventilated, and free from dust. This 
method does away with drying-boxes, which are apt to be 
somewhat uncertain and irregular in their action. 

To prevent the troublesome sticking of the plates to the 
le veiling-shelf, owing to the spreading of the emulsion on the 
back of the plate, the writer has found it useful to cover the 
warmed and levelled slab with a plain gelatine solution, made 
insoluble by the addition of chrome alum, and then to sprinkle 
line shot evenly over the coated surface. 

The best results are secured when plates coated with an 
emulsion rich in gelatine are rapidly set. In warm weather, 
however, the films set slowly, and to hasten the process Prof. 
Burton has devised the cooling arrangement shown in Fig. 23. 
C is a tin or zinc tank, somewhat wider and longer than the 
levelling slab, A. It is fastened securely to the wall, and, 
when plates are to be coated, it is filled with ice. A faucet is 
inserted into one end to draw off the water. 

Some coaters use a small tripod on which the plate to be 
coated is placed. Fig. 24 shows a simple form which can be 
levelled by means of the thumb-screws as shown. 

The writer has used with success, instead of the customary 
levelling slab, the arrangement shown in Fig. 25. 






COATING THE PLATES. Ill 

JB .^ 




112 THE PHOTOGRAPHIC NEGATIVE. 

The purpose of this apparatus is to hold the plates firmly 
clamped end to end, and in connection with the coating-box, 
next to be described, to allow the plates to be rapidly and evenly 
coated without any of the emulsion running over the edges, 
as well as to avoid the necessity of disturbing the plates until 
the films are well set. 

To construct the apparatus a hard-wood slab, of suitable 
length and width, and one inch thick, is smoothly and evenly 
planed, both surfaces being left perfectly plane and parallel. 
On the accuracy with which this is done depends the efficiency 
of the arrangement. Along one side a hard-wood strip, B, one 
and a quarter inches wide and a half -inch thick is firmly screwed. 
At one end a quarter-inch strip, half -inch wide is fastened. 
Two long strips, A A, of the same thickness, but two inches 
wide, and two short strips of equal width and thickness are 
next worked out of hard wood. The outer long strip and the 
two short ones are slotted to receive the thumb-screws, D, D, 
shown in the cut. These thumb-screws pass through the slots 
into the slab. The long strip in the center is also slotted and 
held loosely in place with common screws, or with thumb-screws 
if preferred. The inside edges of all these strips may be bev- 
elled slightly towards the slab, although this is not essential. 
The slab should be battened at the ends to prevent warping. 
It should also be smoothly sand-papered and shellacked, as also 
the strips. The dimensions of the slab will vary with the size 
and number of the plates to be placed on it. That shown in 
the cut, designed to hold twelve whole plates in two rows, is 54 
inches long and 17 inches wide. The slab is levelled by means 
of the screws shown in Fig. 22. 

The plates, E, E, E, are placed on the slab between the strips 
as shown, the movable side and end pieces are pushed firmly 
against the plates, and thumb-screws tightened. The plates 
are then coated, using the coating-box shown in Fig. 26, and 
allowed to set. When set. they may be removed by loosening 
the thumb-screws and taking away the movable strips, as the 
slots are cut through to the inside edges. 

If a number of these slabs are provided, one can be levelled 
above the other, and a large number of plates coated in a short 



COATING THE PLATES. 113 

time. This arrangement when used in connection with the 
coating ; box has but one disadvantage that of slow setting. 
This ma} r be obviated by placing between the strips long strips 
of plate-glass, slightly narrower and shorter than the width 
and length of the plates. In this case the thickness of the 
movable strips must be increased. 

Coating-Box. A very efficient coater is shown in Fig. 26. 

3. IN 




The box is exactly 6-J inches wide, for coating whole plates. 
C is a solid double inclined plane. The outlet, A, is made by 
inserting a piece of cardboard between JB and 0, while the box , 
is being fastened together. A piece of cloth is glued over 
this opening. The box is made of wood firmly fastened with 
glue and screws, and well shellacked outside and in. The 
emulsion is poured in, and made to run over the inclined plane 
by tilting the box. 

Other Methods of Coating. Plates up to 6 by 8 inches 
are easily coated by balancing the plate on the thumb and 
fingers of the left hand, then with the right hand pour care- 
fully over the plate the exact quantity of emulsion necessary 
to give a film of the desired thickness. The spreading of the 
emulsion may be helped by using a glass rod, a clean camel's- 
hair brush, or the tip of the little finger. The plate is gently 
rocked a moment to equalize the film and then placed on the 
levelling slab to set. 

The flowing of the emulsion will be greatly helped by first 
passing over the surface of the plate a squeegee muffled in 
soft flannel and moistened in warm water. 

When the plates have received a substratum of water glass, 
or one of sugar, the emulsion can be flowed over the plate 
like collodion. 



114 THE PHOTOGRAPHIC NEGATIVE. 

Some operators prefer to coat the plates while resting on 
the levelling tripod shown in Fig. 2, but the author sees no 
advantage in this practice. 

Another method is to level the plate, then to pour on the 
necessary quantity of emulsion which is equalized with a 
broad camel's-hair brush used for this purpose only. The 
brush is rapidly drawn over the surface of the plate in all 
directions to secure an even coating. Brushes used for this 
purpose should have rubber mountings, if those mounted in 
metal be used, the metal must be well shellacked. This is a 
simple and expeditious method. 

In whatever way the coating is done, the plates must be 
slightly warmed and dusted before the emulsion is poured on. 

Quantity of Emulsion Necessary to Cover Various Sizes 
of Plates. The film when dry must have a certain thickness 
in order to give sufficient density to the image. The only 
test possible in the coating-room is to examine the films when 
set, by transmitted light. If the outline of the flame of the 
ruby lamp can be just made out through the film, the coating 
is all right. To secure this result it is best to cover each 
plate with a fixed and constant quantity of emulsion, using a 
pipette, or a horn or wooden spoon of proper size for each 
size of plate. 

The following table gives the quantities of emulsion neces- 
sary to give a good film to the sizes in most common use : 

3}^ by finches 1 dram 

4 by 5 inches 1J^ drams 

4} by Clinches 2 to 3 drams 

5 by 8 inches 3 to 4 drams 

6^ by 8% inches 4 to 5 drams 

8 by 10 inches 6 to 8 drams 

One dram of emulsion for every ten square inches of surface 
is about right. 

Drying. When set the plates may be dried by any of the 
methods described in Chapter I. 

Packing the Plates. Many different methods of packing 
the prepared plates. The writer prefers to place them face to 
face in packages of half-a-dozen, well wrapped up in non- 
actinic paper, and to store them in pasteboard boxes, also well 
wrapped, in a cool, dry place. 



CHAPTER XL 

DEVELOPMENT, FIXING, ETC. 

THE reader is referred to Chapter II. for the theory of de- 
velopment and fixing. What follows in this chapter deals 
with the practical manipulations of the dark-room. 

Development. Many substances possess the power of re- 
ducing salts of silver to the metallic state, and so giving 
visibility to the latent image impressed by the action of light. 
Among others, mention may be made of sulphate, borate ; 
phosphate, and tartrate of iron, pyrogallic acid, hydrochinone, 
hydroxylamine, resorcin, and pyrocatechin. Of these the sul- 
phate of iron, pyrogallic acid, and hydrochinone alone have 
more than an experimental value. Hydrochinone, although 
a powerful reducer, is but little used at present, owing 
to its high cost. The oxalate of iron and pyrogallic acid are 
the reducing agents now in most common use, each having its 
advocates and each its own place in photographic work. 

The oxalate of iron developer is the simplest, the cleanliest, 
and the easiest to work, but as a rule it does not work well 
with short exposure ; it does not admit of so wide a range of 
modification to correct errors of exposure as does the method 
with pyrogallic acid. On account of the regularity of its ac- 
tion, and the fact that it does not stain the film or the hands, 
it is perhaps the best method for beginners. 

Pyrogallic acid is more powerful, has a wider range of 
modification to adapt it to the varying needs of the operator, 
and seems to give better modeling and a more perfect ren- 
dering of half tones. It is the method for the advanced prac- 
titioner, whose judgment has been ripened by long experi- 
ence 



116 THE PHOTOGRAPHIC NEGATIVE. 

FORMULAE. 

Oxalate of Iron Developers. 
1. TRUTAT'S FORMULA. 

a Neutral oxalate of potash 30 parts 

Water 100 parts 

b. Sulphate of iron 30 parts 

Tartaric acid % part 

Water 100 parts 

Solution b will keep indefinitely if placed in a strong light 
when not in use. 

c. Bromide of potassium. 5 parts 

Water 100 parts 

This is the restrainer, and is to be used only in cases of over- 
exposure. 

To make the developer add one part of b to three or four 
parts of a. If the plate proves to have been over-exposed, add 
ten drops of c to each ounce of developer. Develop until the 
image is visible at the back of the plate. 

The proportions of one to three, given above, are the strong- 
est possible with this form of developer, and for full exposures 
will prove too powerful. A safer method is to cover the plate 
first with a mixture of four parts of b and one hundred parts 
of a. 

If the high lights begin to appear in one or two minutes, 
the exposure was about right, and the plate is removed to a 
second tray containing twelve parts of b to one hundred parts 
of a, in which the development is completed. If, however, 
the image is slow in appearing in the first solution, it is an 
evidence of a short exposure, and the plate is transferred to 
the second tray, and after a few moments to a third contain- 
ing the normal developer b twenty-five parts, a seventy-five 
parts. If even this strong developer does not bring out suffi- 
cient detail, pour the developer into a graduate containing a 
few drops of a very dilute solution of hyposulphite of soda 
(1 to 2,000), and return to the plate. The effect is almost 
instantaneous, a slight veil comes over the image, but new de- 
tails appear. If too much of the accelerator be added the 
veiling becomes too pronounced and the plate is ruined. The 
addition of hypo is always dangerous. 






DEVELOPMENT, FIXING, ETC. 117 

2. EDER'S CONCENTRATED DEVELOPER. 

Neutral oxalate of potash 2 ounces 

Water 6 drams 

Sulphate of iron 3J ounces 

Dissolve the bxalate in boiling water ; when dissolved add 
the iron and keep at 200 deg. until dissolved. Set aside for 
twenty-four hours, then decant the clear liquid for use. 

This forms a very powerful developer for instantaneous 
views, but should be diluted somewhat with water. 
3. EDER'S OXALATE DEVELOPER. 

a. Neutral oxalate of potassium 100 parts 

Distilled water 400 parts 

Acidulate with oxalic acid 

b. Sulphate of iron 50 parts 

Distilled water 150 parts 

Sulphuric acid 3 drops 

c. Bromide of potassium 5 parts 

Distilled water 50 parts 

d. Hyposulphite of soda 1 part 

Distilled water 100 parts 

For the developer take of a three parts, of I one part. Ee- 
strain with a few drops of c. 

For over-exposures take less of J, adding more if re- 
quired. To give density use c. 

For soft, harmonious negatives full of detail take of 

a 2)^ ounces 

b % ounce 

c 4 drops 

d 6 drops 

4. FERROUS OXALATE DEVELOPER WITH CITRIC ACID FOR INTENSE 
(BLACK AND WHITE) NEGATIVES. 

a. Water 500 parts 

Sulphate of iron .150 parts 

Citric acid 2 parts 

b. Water ...500 parts 

Neutral oxalate of potassium 200 parts 

Solution b is boiled, and when cold filtered from the green 
crystals which may have separated out. One part of a is 
mixed with four parts of b to form the developer. 



118 THE PHOTOGRAPHIC NEGATIVE. 

5. OXALATE DEVELOPER WITH CHLORIDE OF AMMONIUM AND CITRIC ACID 
FOR WELLINGTON'S CITRO-CHLORIDE EMULSION. 

a. Oxalate of potassium 2 ounces 

Chloride of ammonium 40 grains 

Water 20 ounces 

b. Sulphate of iron 4 drams 

Citric acid 2 drams 

Water 20 ounces 

c. Bromide of potassium 1 ounce 

Water 3 ounces 

Mix a and 5 in equal volumes, and add one dram of c to 
each ounce of developer. 

Alkaline Development. In all alkaline developers there are 
three elements : 1, pyrogallic acid, or its equivalent ; 2, an 
alkali ; 3, bromide of potassium or ammonium. 

The process of development will be better understood if we 
consider the office which each of these elements fills in devel- 
opment. This will enable the operator to compound and mod- 
ify his developing solutions to suit his tastes and needs. 

Pyrogallic acid is a powerful absorbent of oxygen, and re- 
duces the soluble salts of silver to the metallic state ; it is then 
the reducing agent in most alkaline developers. Its place may 
be supplied by other oxygen absorbers, such as hydrochinone, 
hydroxylamine, etc. 

Owing to its reducing power, due to its affinity for oxygen, 
pyrogallic acid gives density to the image. If the amount of 
alkali used remains constant, the density will be proportioned 
to the amount of acid used. The degree of density conferred 
is governed by the amount of pyro used, although an in- 
crease of the alkali may serve the same purpose. 

The alkali, either ammonia or the carbonates of potash or 
soda, combines with the bromide, which is set free from the 
silver by the reducing power of the pyro. If the amount of 
alkali be increased, there is a corresponding increase of the 
affinity of pyro for oxygen, and in consequence a greater re- 
ducing action, giving an increased amount of reduced silver, 
which may increase density. Hence an increase of alkali 
means increased rapidity of development. If an excess of 



DEVELOPMENT, FIXING, ETC. 119 

alkali be added the reduction of silver takes place so rapidly as 
to produce fog. 

Soft, harmonious images are produced by the use of a com- 
paratively large proportion of alkali, the pyro being kept 
slightly under strength. 

On the other hand an excess of pyro gives great density and 
heightens the contrasts between the tones of the image. 

The bromide diminishes the affinity of pyro for oxygen, 
and hence acts as a restrainer. It also diminishes the liability 
of the pyro attacking the unaltered bromide of silver, and thus, 
to a certain extent, prevents fog. 

The use of bromide is not always necessary, since gelatine 
itself acts as a restrainer, by holding the particles of silver en- 
closed in a semi-impervious coating, which presents more or 
less resistance to the action of the developer. 

This brief explanation of the function of each of the com- 
ponents of an alkaline developer will, it is hoped, enable the 
operator to compound his developed with judgment, and to use 
it with discretion, modifying it by increasing the proportions of 
one or the other ingredient as need may arise. 

The question now arises : Should the mixed developer be 
applied at once to the plate, or should the pyro, the alkali, or 
the bromide be first used ? 

If the time of exposure were always correct, there can be no 
doubt that the best method would be to apply the mixed de- 
veloper. But the exposure is always more or less doubtful ; it 
is nearly always necessary to modify the developer in one way 
or another, to meet special needs. 

It would, then, seem more scientific to begin with a part of 
the developer, and to add the other ingredients in small quan- 
tities as required. Since the effect of a preliminary applica- 
tion of pyro is to slow the plate, the author's practice is to 
flood it first with a solution containing about half the quantity 
of pyro likely to be needed, and to add the alkali in small in- 
crements, as required to bring out detail, finishing up with the 
rest of the pyro, to give density, using the bromide only in 
cases of necessity. This is for time exposures. 

For instantaneous exposures the method is reversed ; the 



120 THE PHOTOGRAPHIC NEGATIVE. 

plate is first flooded with a weak solution of the alkali, and the 
other ingredients added as required. 

In this connection it may be stated that the author's prefer- 
ence is for slow development, as giving the operator time to 
see the needs of the plate and meet them before it is too late. 
Hasty development has ruined many a plate which might have 
been saved by a more judicious treatment. 

The development should, as a rule, be continued until the 
image is fairly visible at the back of the plate. 

Density. Excess of pyro or prolonged development will 
increase density. The amount of density which it is desirable 
to give to the image, depends on the nature of the surfaces on 
which the positive is to be printed, since negatives adapted to 
one kind of surface are not always suitable for others. For 
instance, the negative which will give good results on albu- 
menized paper, will not necessarily produce equally good 
prints on matt surfaces, as the platinotype, bromide, and plain 
papers. t 

For printing on albumenized paper, the negative should show 
all the detail in the shadows and be of moderate density, since 
albumenized paper renders the most delicate gradations. For 
matt prints, and photogravures or heliogravures, however, there 
should be as little deep shadow as possible in the negative, and 
a small amount of high light, not more than one-fourth. Most 
of the tones should be half-tones, subdued lights, and well-illu- 
minated shadows, with great opacity in the high lights, for 
photo-engraving purposes, and not too intense for matt surface 
prints, which do not render well details in the deepest shadows. 

The amount of density must then be determined by circum- 
stances, and the operator will seek to give his negatives those 
special qualities which best fit them for the purposes to which 
they are to be put. 

The Quantity of Pyro and Alkali to be Used. Excess of 
pyro or alkali is equally disastrous, the first producing too 
great density, the latter giving foggy images. While it is im- 
possible to give any exact proportions, the author, after com- 
paring many formulae, finds that two and a half grains of pyro 
'and four grains of carbonate of potash, or ten grains of car- 



DEVELOPMENT, FIXING, ETC. 121 

bonate of soda, or two drops of ammonia, to each ounce of 
mixed developers, is a fair average. In special cases the pyro 
may be increased to five grains to the ounce, but the quantity 
of alkali should not greatly exceed the quantities given, or fog 
may result. 

It is hoped that these remarks may make the intelligent use 
of the following developers more easy. 

PYROGALLIC ACID DEVELOPERS. 
No. 1. COOPER'S FORMULA. 

a. Sulphite of soda 6 ounces 

Water. . . 1 quart 

When dissolved add 

Pyrogallic acid 1 ounce 

b. Carbonate of soda, pure 4 ounces 

Water 1 quart 

Developer : a 1 ounce ; 5 1 ounce ; water 1 ounce. Restrain 
with bromide of potassium. 

No. 2. BEACH'S FORMULA. 
A. Pyro Solution. 

Warm distilled water 2 ounces 

Sulphite of soda 2 ounces 

When dissolved and cool add 

Sulphurous acid 2 ounces 

Pyrogallol % ounce 

B. Potash Solution. 

1. Water 4 ounces 

Carbonate of potash, c. p B ounces 

2._Water Bounces 

Sulphite of soda 2 ounces 

Combine 1 and 2 into one solution. 

For a shutter exposure take 3 ounces water, -| ounce A, and 
3 drams B, increasing the latter to 5 drams if the image hangs 
back. 

For over-exposure 3 ounces water, 3 drams A, 1 dram B, 
adding more if necessary. 



122 THE PHOTOGRAPHIC NEGATIVE. 

No. 3. THE AUTHOR'S FORMULA. 

a. Water 10 ounces 

Sulphite of soda 1 ounce 

Dissolve and add 

Pyrogallic acid , 1 ounce 

Sulphuric acid 20 drops 

b. Water 10 ounces 

Carbonate of pytash 1 ounce 

c. Water 10 ounces 

Carbonate of soda 1 ounce 

NORMAL DEVELOPER. 

Water 4 ounces 

Solution a 3 drams 

Solution b. 2 drams 

Solution c 2 drams 

These quantities may be increased if necessary. An excess 
of J over c gives soft harmonious negatives full of detail ; when 
c is in excess more density and less detail is gained. 

No. 4. CARBUTT'S FORMULA. 

a. Distilled water 10 ounces 

Sulphite of soda 4 ounces 

Dissolve and add slowly 

Sulphuric acid 1 dram 

Pyrogallic acid 1 ounce 

And water to make 16 fluid ounces. 

b. Granulated carb. of potash 2 ounces 

Granulated carb. of soda 2 ounces 

Water 10 ounces 

Dissolve and add water to make 16 fluid ounces. 

NORMAL DEVELOPER. 

Water 4 ounces 

Solution a 3 diams 

Solution b 2 drams 



DEVELOPMEHT, FIXING, ETC. 123 

No. 5. EDWARDS' FORMULA. 

a. Pyrogallic acid 1 ounce 

Glycerine 1 ounce 

Alcohol 6 ounces 

b. Bromide of potassium 60 grains 

Ammonia 1 ounce 

Glycerine 6 ounces 

Water Bounces 

NORMAL DEVELOPER. 

a. Solutiona 1 part 

Water 15 parts 

b. Solution b 1 part 

Water 15 parts 

Mix equal parts of a and I. If the image flashes up quickly 
pour off the mixed developer, and flood the plate with solu- 
tion a. 

No. 6. HENDERSON'S FORMULA, WITH FERRO-CYANIDE OF POTASSIUM. 

Saturated solution of ferro-cyanide of potassium. ..10 ounces 

Ammonia 10 drops 

Pyrogallic acid 15 grains 

This solution keeps well. If it refuses to develop add a few 
drops of ammonia. 

No. 7. E. VON SOTHEN'S HYDROCHINONE DEVELOPER. 

a. Carbonate of soda 60 grains 

Water 1 ounce 

b. Hydrochinone 12 grains 

Sulphite of soda 60 grains 

Water 1 ounce 

NORMAL DEVELOPER. 

Water 1 ounce 

Solution a I ounce 

Solution 6 2 ounces 

The mixed developer can be used many times. 
No. 8. DR. MARTELL'S SODA, POTASH, AND AMMONIA DEVELOPER. 

a. Pyrogallic acid 1 dram 

Citric acid 5 grains 

Sulphite of soda 1 dram 

Water 10 ounces 



2 THE PHOTOGRAPHIC NEGATIVE. 

b. Carbonate of potash 1 ounce 

Water 20 ounces 

c. Bromide of ammonium 15 grains 

Ammonia 1 dram 

Water 20 ounces 

NORMAL DEVELOPER. 
a, b, and c equal parts 

NOTES ON THE GrENEEAL COMPOSITION OF DEVELOPERS. 

The Oxalate of Iron Developer. In this developer, com- 
monly known as the ferrous-oxalato developer, the only func- 
tion of the oxalate of potash is to produce, when combined with 
sulphate of iron, the powerful reducing agent, oxalate of iron, 
which is a compound insoluble in water, but soluble in an ex- 
cess of oxalate of potash. If, on the addition of the iron solu- 
tion to the oxalate of potash, the oxalate of iron is thrown 
down in the shape of a yellowish powder, it is a sure indication 
that there is a deficiency of the oxalate of potash. In this case 
the developer must be rejected and a fresh one mixed, contain- 
ing less iron. 

The oxalate of potash must be neutral or slightly acid. 
If the oxalate solution shows an alkaline reaction, turning red 
litmus paper blue, oxalic acid must be added to restore the red 
color to the paper. 

The sulphate of iron solution does not keep well unless tar- 
taric acid is added ; the solution must then be kept in the sun. 

Old oxalate of iron developer may be kept in good condi- 
tion by the occasional addition of a few grains of tartaric acid 
and keeping it in the sun. Old developer is useful to start 
development with. 

Alkaline Developers. In this form of developer the pyro 
is the reducing agent, the other ingredients are either accelera- 
tors, restrainers, or preservatives added to prevent the too 
rapid deoxidation of the pyro. 

When using pyro the author prefers to begin with a devel- 
oper weak in pyro and alkali, adding more of each as re- 
quired. Plates known to have received a full exposure should 



DEVELOPMENT, FIXING, ETC. 125 

be soaked for two or three minutes in a plain pyro solution, 
adding the accelerator in small quantities. 

Potash, soda, and ammonia are accelerators ; sulphite of 
soda is a preservative, and bromide of potassium a restrainer. 

Excess of pyro gives great density with little detail ; excess 
of accelerator gives plenty of detail but little density. Bear- 
ing these principles in mind the intelligent operator is able to 
modify his developer to suit special cases. 

The Hydrochinone Developer. This form of developer is 
but little known, owing chiefly to its expensiveness, hydro- 
chinone being manufactured only in small quantities. 

Its" many good qualities, however, should recommend it. 
It is a more powerful reducer than pyro, but slower and more 
uniform in its action ; it does not oxidize as quickly as pyro ; 
it gives a velvety black image with great cleanness in the 
shadows, and it does not stain. For transparencies and opals 
it is far superior to pyro or oxalate of iron. 

The Alum Bath. When the development is completed, 
the negative should be immersed for five minutes in a five 
per cent, solution of alum. This hardens the film, thus pre- 
venting frilling, and in the case of pyro-developed negatives, 
removes any coloration of the film caused by the oxidation of 
the pyro. 

The alum bath may be used for many negatives, but the 
same bath must not be used both for iron and pyro-developed 
negatives. 

Fixing. The negative is washed slightly after leaving the 
alum bath, and fixed in a one to five hyposulphite of soda 
solution. It should remain in this bath for some time after 
the creamy appearance has left the plate. 

Washing. In order to eliminate thoroughly all traces of 
hypo, the plates must receive a thorough washing in many 
changes of water, or, better still, in running water. 

The different methods of washing will be found described 
in Chapter II. 

When the negatives are thought to be sufficiently washed, a 
small quantity of the drainings should be placed in a beaker 



126 THE PHOTOGRAPHIC NEGATIVE. 

and tested for hypo, using for that purpose the following solu- 
tion : 

Permanganate of potash 2 grains 

Carbonate of potash 20 grains 

Water 40 ounces 

The addition of a few drops of this rose-colored solution to 
a pint of water will produce a slightly pink tinge. If any 
hypo be present this color will give place to one of a slightly 
greenish hue. 

If this test detects hypo the washing must be prolonged, or 
the plates may be immersed for a short time in the following 
hypo-eliminator : 

BELLITZKI'S HYPOCHLORITE OF ZINC HYPO-ELIMINATOR. 

a. Chloride of lime -.. .304 grains 

Water 35 ounces 

b. Sulphate of zinc 610 grains 

Water 100 ounces 

Add J to a and shake well. 

Set aside for some hours and decant the clear liquid, which 
must be kept in well-stoppered bottles. It retains its good 
qualities as long as it smells of hypochlorous acid. 

For use add one part of the solution to sixty parts of water. 

After this treatment the plate is washed for ten minutes, 
all adhering spects removed with a soft sponge, and dried 
spontaneously. 

Intensifying. Many negatives are wanting in density ow- 
ing to over-exposure or insufficient development. In such 
cases intensification must be resorted to in order to increase 
the density. The bichloride of mercury intensifier in its com- 
mon form will be found in Chapter II. It is, perhaps, as 
good as any. 

If preferred, one of the following formulae may be sub- 
stituted for it. 

Dr. Eder's. The negative is whitened in a saturated solu- 
tion of bichloride of mercury, and after thorough rinsing im- 
mersed in 

Potassium cyanide 10 parts 

Potassium iodide 5 parts 

Mercuric chloride 5 parts 

Water 2000 parts 

and well washed. 



DEVELOPMENT, FIXING, ETC. 127" 

Cyanide of Silver Method. The negative is 
whitened in the following : 

Bichloride of mercury 10 grains 

Chloride of ammonium 10 grains 

Water 1 ounce 

It is then well washed and blackened in 

a. Cyanide of potassium 2 ounces 

Distilled water 48 ounces 

b. Nitrate of silver 1 ounce 

Distilled water 6 ounces 

Mix a and 5 by pouring 5 gradually into a with constant 
stirring. Allow the mixture to stand a few days before using. 

The Gallic Acid and Nitrate of Silver Intensifier. Dr. 
Wallace and Mr. Bartlett have recently worked out a modifi- 
cation of an old wet plate intensifier which makes it applic- 
able to gelatine emulsion plates. 

The author has found it reliable and efficient. 

The following solutions may be kept in stock : 

1. Perchloride of iron 4 grains 

Chrome alum 2 grains 

Citric acid 4 grains 

Water 1 ounce 

2. Gallic acid 80 grains 

Alcohol 1 ounce 

3. Nitrate of silver 40 grains 

Water 1 ounce 

For use add one dram each of 2 and 3 to two or three 
ounces of water. 

The negative is soaked for a few minutes in solution 1, in 
which it should not be allowed to bleach unless it is slightly 
fogged or over-developed. 

The plate is then rinsed under the tap, and sufficient of solu- 
tions 2 and 3 diluted as directed, is flowed over it and allowed 
to act until the proper degree of density is reached. After 
which it is well washed. 

This method is applicable either before or after fixing. In 
either case the negative must be well washed. 

Uranium Intensifier. The plate is flooded with a one per 



128 THE PHOTOGRAPHIC NEGATIVE. 

cent, solution of nitrate of uranium. After remaining on the 
plate for a minute it is poured back into the graduate, in 
which a few drops of a two per cent, solution of ferricyanide 
of potassium have been placed. The mixture is then poured 
back on the plate. If this does not give sufficient density add 
more of the ferricyanide. 

This is one of the most permanent of intensifies. 

Reduction. It occasionally happens that negatives have 
too great density. In this case the density must be reduced. 
This may be done with either of the following solutions : 

FARMER'S REDUCER. 

Ferricyanide of potassium (saturated solution) 1 part 

Hyposulphite of soda solution (one to five) 10 parts 

BELLITZKI'S REDUCER. 

Potassium ferric oxalate 1 to 10 grains 

Hyposulphite of soda solution (one to five) 1 ounce 

Local reduction can be made by mixing the preparations 
with mucilage and applying with a brush. Wash well after 
treatment. 

Varnishing. All negatives worth preserving should be 
varnished. The method of applying the varnish will be found 
on page 30. A few additional formulae are given here : 

1. Sandarac ^ 4 ounces 

Alcohol 28 ounces 

Oil of lavender 8 ounces 

Chloroform 5 drams 

2. White hard varnish 15 ounces 

Methylated alcohol 25 ounces 

This will be found a good and cheap varnish if durability 
is not required, as it is easily rubbed up for retouching upon 
and easily cleaned aff. Yery suitable for enlarged negatives 
that are not to be retained. 

TOUGH, HARD, AND DURABLE. 

3. Shellac 1^ ounces 

Mastic ^ ounce 

Oil of turpentine Bounce 

Sandarac ....... 1 J^ ounces 

Venice turpentine J^ ounce 

Camphor 10 grains 

Alcohol , 20 fluid, ounces 



DEVELOPMENT, FIXING, ETC. 



129 



4. Sandarac . . .......... . ........................ 90 ounces 

Turpentine .................................... 36 ounces 

Oil of lavender ................................. 10 ounces 

Alcohol ........................................ 500 ounces 

This one may be nibbed down with powdered resin to give 
a good retouching surface : 

5. Sandarac .................................... 4 ounces 

Seed lac ....................................... 1 ounce 

Castor oil .................................... 3 drams 

Oil of lavender ................................ 1J drams 

Alcohol ................................... , . . .18 ounces 

COLLODION VARNISH. 

6. Tough pyroxyline ................................ 12 grains 

Alcohol .......................................... 1 ounce 

Ether ........................................... 1 ounce 

Flow over the plate as in collodionizing, drain well, and 
dry. 




CHAPTEE XII. 

PIPER NEGATIVES. STRIPPING FILMS ON PAPER, CARDBOARD, AND 
COLLODION. 

THE latest development in photographic negatives is a return 
to first principles, the use of paper as a permanent or tem- 
porary support for the sensitive film. 

It is not the writer's intention to enter into a discussion of 
the advantages or disadvantages of the new method. The 
writer's own opinions on the subject are decided and based on 
practical experience in the field and in the dark-room, but he 
is content to keep those opinions to himself, simply giving de- 
tailed descriptions of the manipulations peculiar to the use of 
paper or other similar support as a substitute for glass. 

For various reasons collodion does not seem to take kindly 
to paper ; therefore it is to be assumed, of all the methods here 
given, that the sensitive film is formed by coating the paper 
with one of the emulsions given in chapter VIII. 

The use of paper as the support does not necessitate any 
change in the nature of the emulsion, except, perhaps, that a 
slight increase in the quantity of gelatine may be advisable, or 
a decrease in the amount of water. 

Any changes which are recommended are necessitated by 
the flexible nature of the support, and the somewhat different 
conditions under which the emulsion must be flowed over it. 
. Radical differences exist between the preliminary manipula- 
tions of paper intended as a permanent support, and those to 
be employed when the film is to be finally removed from the 
paper. 

Each of these will be treated in turn, beginning with those 
to be used when the paper is to form the permanent support. 

The Paper. When the paper is to form the final support 
of the negative, great care must be taken to select a variety 



PAPER NEGATIVES. 131 

presenting the greatest uniformity of surface, and freedom 
from grain. The kind known as plain Saxe negative paper is 
well adapted to this process. Parchment paper, if it could be 
had free from marks and lines, would be the best, since its use 
would render the after operation of oiling unnecessary. 

Whatever brand of paper be selected, its right side is the 
one to be coated. Neglect of this precaution will result in 
grainy and spotted negatives, due to the unevenness of the un- 
polished side of the sheets. 

Sizing the Paper. If the paper selected be strongly sized, 
it may be coated without further preparation. Better results, 
however, will be obtained on paper which has received a coat- 
ing of coagulated albumen or insoluble gelatine. Both of these 
may be obtained of any dealer in materials for the carbon 
process, or, if preferred, the experimenter may prepare his 
own paper, by floating it for a minute on the following bath : 

Hard gelatine 4 ounces 

Sulphate of baryta (powdered) 2 ounces 

Water 20 ounces 

Dissolve and mix thoroughly ; then stir in a hot solution of 
six grains of chrome alum in one ounce of water. 
. The paper is coated by rolling it up tightly, face outwards ; 
the roll is laid upon the surface of the liquid, the loose end is 
seized and the paper unrolled ; it is then hung up to dry. 

Paper possessing a high degree of transparency may be pre- 
pared by soaking the sheets for some days in copal varnish, and 
then drying. When dry the surfaces are polished with pum- 
ice stone, after which a layer of soluble glass is applied and 
well rubbed in with a piece of cloth. Some small experiments 
of the author in this direction have resulted favorably, the 
emulsion readily flowing over the prepared surface. 

Coating the Paper. The prepared sheets may be coated 
with the emulsion by the method just described, having been 
first slightly dampened. The tray containing the emulsion is ' 
placed in a larger tray containing water, the temperature of 
which is kept at about 70 deg. The paper is rolled up as be- 
fore and floated on the emulsion, avoiding air bells. It is then 
seized by one end and drawn over the edge of a glass plate, 



132 



THE PHOTOGRAPHIC NEGATIVE. 



previously levelled over the tray. As soon as the film is set 
the paper may be stripped from the glass and hung up to dry. 
Another very good method is that sometimes used in the 
preparation of carbon tissue, and shown in Fig. 28. The des- 
cription of the apparatus is from " Abney's Treatise on Pho- 




FIG. 



tography." A porcelain or^other dish, A, is placed on a hot 
water tin, B, the water being kept at the boiling point by a 
lamp or Bunsen burner. Over the dish is placed a level table, 
D, at one end of which is a roller, G, that is on a level with 
the top surface of a glass, E, placed on the table, D. The 
paper, F, is floated on the warm gelatine solution contained in 
the dish, drawn through it, seized by the hands, drawn over 
the roller on to the plate, E, where it is allowed to remain till 
the gelatine is well set ; after which it is hung up by clips to 
dry. The dish has to be removed each time that paper is 
floated ; if B be widened, the dish can be run backwards and 
forwards in a very simple manner. 

Another simple method is to soak the paper in warm water 
until limp, then to place it on a glass plate, and with blotting- 
paper and a squeegee, to remove all excess of moisture. The 
paper may then be coated as if it were a glass plate. After 
being coated it is placed on the levelling slab until the film is 
well set, after which it may be hung up to dry, or allowed to 
dry on the glass. 



PAPER NEGATIVES. 133 

This is the simplest method, and for most purposes it will be 
found as good as any. 

Another method, which is preferred by some operators, is to 
coat a glass plate, previously polished with French chalk, with 
the emulsion, and when the film has thoroughly set, gently to 
squeegee the moistened sheet of paper in perfect contact with 
the film. When dry, the paper bearing the film may be pulled 
from the glass. 

A glass roller may be used to equalize the film. This roller 
is made by inserting corks in the ends of a piece of glass tub- 
ing, one-half inch in diameter, and a trifle longer than the width 
of the paper to be coated. About one-eighth of an inch from 
each end rubber bands surround the rod. These serve to keep 
the rod slightly above the surface of the paper, and their thick- 
ness determines that of the film. Short pieces of wire are in- 
serted in the corks, the ends of a bent wire are bent around 
these wires, to form a handle by which the rod is manipulated. 

The emulsion is poured on the paper in parallel lines between 
the rod and the handle ; the rod is then drawn backwards and 
forwards over the paper to equalize the film. 

The glasses on which the sheets of paper are squeegeed must 
be a trifle wider than the paper, in order that the rubber bands 
may rest on the glass. The distance between the bands 
should just equal the width of the paper. 

The emulsion may also be spread over the paper with a stiff 
brush. 

Balagny^s Method. M. Balagiiy prefers to paste the paper 
to the glasses, over which has been flowed a thin film of the 
following solution : 

Benzine '. . . 3J^ ounces 

Gum dammar 15 grains 

White wax 30 grains 

Resin 15 grains 

This solution is flowed over the glass like collodion and the 
glass is racked away to dry. 

The paper, cut to size, is first soaked in water till limp, and 
then given an even coating of thin starch paste, free from 
lumps, and laid down on the glass, the starched side of the 



134: THE PHOTOGRAPHIC NEGATIVE. 

paper in contact with the waxed surface of the glass. The 
face of the paper is then covered with a sheet of blotting- 
paper, and all excess of paste, as well as all air-bells, removed 
with the squeegee. When dry, the paper is coated and the 
film allowed to dry on the glass ; the paper is then stripped 
from the glass by raising one corner first. 

The advantage of this method is that the paper is kept in 
perfect contact with the glass, on which it is tightly stretched, 
and that there is no possibility of its cockling or rolling up as 
it dries. 

STRIPPING FILMS. PAPER SUPPORT. 

Chennemere's Method. The glasses are waxed as in Balag- 
ny's method given above. The paper is cut somewhat smaller 
than the plates, softened in water, and laid down on the plate, 
leaving a narrow margin of glass on all sides. Excess of mois- 
ture and air-bells are removed by means of blotting-paper and 
the squeegee. Narrow strips of albumen paper are then 
pasted around the paper and glass, and when dry the paper is 
given a thin coating of French chalk, all excess being removed 
with a camel's-hair brush, and then collodionized with the 
following plain collodion : 

Ether 1% ounces 

Gun-cotton 15 grains 

Alcohol 1% ounces 

Castor oil 10 drops 

As soon as the collodion is dry the paper is coated and 
allowed to dry on the glass. It can then be stripped from the 
glass by cutting along the edges of the albumen paper. 

The only disadvantage of the above method is the liability 
of the films to leave the paper when cut down to smaller sizes. 
To obviate this difficulty, M. Chenneviere has introduced the 
following improvement: The paper is given a coating of a 
waxing solution made as follows : 

White wax . . . 61 grains 

Benzine 3J^ ounces 

This is applied with a piece of linen dipped in the solution. 
The paper when dry is dampened and fastened to the glass as 



PAPER NEGATIVES. 135 

before. It is then collodionized, and when again dry coated 
with the emulsion. 

Balagny's Method. The paper is pasted on the glass as 
described on page 133, and, when dry, is polished with 
French chalk, a moderately thick coating being given in order 
to fill the pores and leave a smooth surface. It is then collo- 
dionized with the following plain collodion : 

Pyroxyline 23 grains 

Alcohol 3 ounces 

Ether 4% ounces 

When dry, the paper is coated as usual and allowed to dry 
on the glass. 

Fdbrds Method. Plain paper of good body is given a coat- 
ing of Para gum dissolved in benzine (gum 30 grains, benzine 
3 ounces), and hung up to dry in a place free from dust. 

When dry it is moistened and squeegeed into perfect contact 
with a glass plate previously waxed as in M. Chenneviere's 
method, coated as usual, and stripped from the glass as soon as 
the film has set, and then hung up to dry. 

The rubber solution must be well filtered through several 
thicknesses of muslin, and it is conveniently applied to the 
paper with a brush, placing the paper on a glass plate and 
giving it a thin coating. 

Milsom's Method with Waxed Paper. The paper is cut 
one-half an inch longer and wider than the glass supports. It 
is then soaked for five minutes in water, and then pasted by 
its edges on its glass support. For this purpose the paper is 
laid down on moist blotting-paper, with the side to be coated 
in contact with the paper. The glass plate is then placed over 
the paper, the edges of the latter are then turned over and 
glued or pasted to a sheet of common paper of the proper size. 
Dry between blotters under moderate pressure. 

When dry place the glass on a metal plate warmed to above 
the melting point of wax. With a piece of white wax go 
carefully over the entire surface of the paper until it is evenly 
waxed and no air- bells remain between the paper and the glass. 
Then remove the glass from the metal plate and remove all 



136 THE PHOTOGRAPHIC NEGATIVE. 

excess of wax by gently rubbing with a piece of clean flannel. 
The glasses are then dried under pressure, the waxed surfaces 
being placed in contact. When dry, coat as usual. 

Eastman's Method. The paper is first coated with a plain 
gelatine solution containing 15 to 20 grains of soft gelatine to 
the ounce of water. When dry, the paper is again coated 
with any good emulsion which has been made insoluble by the 
addition of chrome alum. 

To every 500 parts of emulsion 15 to 20 parts of the follow- 
ing alum solution is added : 

Chrome alum 4 parts 

Water 90 parts 

Glycerine 40 parts 

An emulsion containing chrome alum should all be used at 
once. 

Stripping films on Cardboard Supports. Any of the 
methods described above, for preparing paper to serve as a tem- 
porary support, may be employed when cardboard is used. 

The simplest method is to polish the cardboards with French 
chalk, and after dusting off all excess of chalk to collodionize 
them with any good, plain collodion, the formula given on page 
50 will answer. The prepared cards are thoroughly soaked in 
water, and then squeegeed, collodion side uppermost, on glass 
plates somewhat larger than the cards. The edges are secured 
to the glass with gummed paper, and when dry the cards are 
coated as usual. 

If preferred, the cards may be waxed with the solution given 
on page 51, before collodionizing, or they may be given two 
coats of shellac. 

Balagny's Method with Methyl Alcohol. To obviate the 
difficulty of determining the proper point at which to cease 
the development of films on paper or cardboard, owing to the 
impossibility of judging of their density by transmitted light, 
M. Balagny has worked out a method which gives films which 
leave their support when placed in the developer. 

Glass plates are polished with French chalk, dusted off, and 
coated with any good emulsion. 



PAPER NEGATIVES. 



137 



When dry the films are collodionized with the following 
collodion : 



Ether 

Methyl alcohol. 

Pyroxyline 

Castor oil. . . 



. 3% ounces 
. 3% ounces 
. 30 grains 
, 1 dram 



The paper or card supports are moistened in water, placed 
upon a clean glass, and all excess of moisture removed 
with blotting-paper and the squeegee, both sides being thus 
treated. A ten per cent, solution of pure gum is then 
laid on with a brush, after which the paper or card is 
carefully laid down on the prepared plate and squeegeed into 
contact. 

As soon as the support is dry it is stripped from the glass by 
cutting around the edges with a sharp knife, and pulling the 
paper or card from the glass. 

After exposure these films are soaked for three or four 
minutes in a one per cent chrome alum solution, then in pure 
water until the film begins to wrinkle. It is then carefully re- 
moved from its support and placed in the developer. 
c c c 





FIG. 29. 

Figure 29 shows a coating-board, devised by the author, for 
coating cards. It has been found useful for holding the cards 
while being waxed or polished and collodionized, as well as 
while being coated. It will also answer for holding paper. 

A is a half-inch slab of hard- wood, battened at the ends to 
prevent warping, planed and sand-papered perfectly smooth. 
Its length and breadth are a trifle in excess of the size of the 
cards or paper to be coated. 



138 THE PHOTOGRAPHIC NEGATIVE. 

B, B, B, B, are movable half-inch strips of thin metal well 
shellacked or japanned, and having slots cut in them, as shown. 
C, C, C, are ordinary flat-headed screws, which serve to clamp 
the metal strips. The slab is levelled with levelling screws or 
wedges. 

The paper or cards to be coated are first cut somewhat larger 
than the size desired, moistened in water and laid smoothly on 
the slab from which the metal strips have been removed. All 
excess of moisture is removed, and perfect contact secured 
with blotting paper and the squeegee. The strips are then 
placed in position and tightly screwed down, in which con- 
dition they act as clamps to hold the paper tightly stretched. 
If the paper is to serve as a permanent support, the emulsion 
is poured on immediately, and evenly distributed with a glass 
rod, the ends of which rest on the side strips, which determine 
the thickness of the film. 

If stripping films are desired, the paper, or cards, when dry, 
is polished and collodionized as described above, and then 
coated. 

"When the films are set the paper may be removed from the 
slab and hung up to dry. The author, however, prefers to al- 
low the film to dry on the slab. 

PELLICULAK FILMS WITHOUT SUPPORT. 

Balagny's Method, Clean glass plates are polished with 
French chalk, dusted, and collodionized with the plain collo- 
dion given on page 135, and, when dry, coated with an emulsion 
containing 35 ounces of water and 1080 grains of gelatine for 
every 770 grains of nitrate of silver. 

When the films are dry they may be detached from the 
glass by cutting around the edges, first detaching one corner 
from the plates. 

These films will be strong enough to undergo all the neces- 
sary manipulations. 

Another method of preparing films without support, is to 
polish and collodionize the plates, then to paste narrow strips 



PAPER NEGATIVES. 139 

of pasteboard around their edges, and to coat them with the 
following gelatine solution : 

Water 14 ounces 

Hard gelatine 1,080 grains 

Soak the gelatine in cold water, dissolve, and add 

Water 3% ounces 

Chrome alum 7 grains 

Glycerine 1 dram 

Ferric acid 40 drops 

This is to be added in a fine stream, with constant stirring. 
The mixture is then well filtered, and the plates coated. When 
dry they are coated with the emulsion, and the dried films are 
stripped from the glass, as in the preceding method. 

The author sees no great advantage in these two methods 
over the usual stripping processes. They are given to demon- 
strate the possibility of preparing a sensitive film, having all 
the transparency of glass, without its bulk or weight. 

Methods of Exposing Films on Paper Supports. Many 
methods of exposing films on flexible supports have been de- 
vised. Most of those recently put forth for gelatine films are 
as old as the calotype process, and possess few or no claims to 
novelty. 

For the exposure of emulsion paper, in long rolls, the roll- 
holder, in some one of its modern forms, is certainly the best 
method for the tourist who does not care to develop his ex- 
posures until he returns home. 

The stay-at-home photographer, however, who only exposes 
a plate now and then, and develops it at once, will use simpler 
and less expensive methods, better suited to his needs. 

Many forms of film-carriers are now in the market, of which 
the best known, perhaps, is the Eastman, which consists of a 
thin tablet of wood surrounded by a light detachable metal 
frame, in which the sensitive tissue, cut to size, is laid face 
down, and the back-board placed in position, when the whole 
is introduced into the plate-holder, exactly as if it were the 
usual plate. 



140 THE PHOTOGRAPHIC NEGATIVE. 

Another effective method is to coat thin pieces of shellacked 
wood with the following mixture : 

Water 4 ounces 

Sulphate of baryta 2J ounces 

Sugar 1 ounce 

Gelatine 1 ounce 

Glycerine 6 ounces 

The wooden tablets are levelled and given a thin coating of 
the mixture, which may be applied with a brush. The sensi- 
tive film is laid down on one of the prepared tablets, and gently 
smoothed into contact. It is easily removed for development, 
and the prepared tablets will answer for several exposures. 

Still another method is to gum the tissues by the edges to a 
glass plate, a thin wooden tablet, or a piece of stiff cardboard. 

A fourth method, applicable to single holders, is to place 
the tissue between a clean glass plate and a sheet of cardboard. 
If this method be employed, care must be taken to allow for 
the thickness of the glass in focusing. The best method seems 
to be that adopted in the Vergara double holder, in which the 
sensitive tissue, cut to twice the length of a single sheet, is 
folded across the middle, and the end of the septum placed in 
the fold, and the whole slid into grooves cut in the holder. 

Films on cardboard are placed in the holders exactly as glass 
plates. Pellicular films on collodion or gelatine are best ex- 
posed behind a glass plate. 

Development. The development of films on paper or card- 
board supports is carried out precisely as in the case of glass 
plates, using any of the developers given in the previous chapter, 
preferably the oxalate of iron developer, or those modifications 
of the alkaline developer which contain oulphite of soda. 

Good, full exposures give the best results with stripping 
films. Long development with pyro is very apt to tan or 
harden the soft gelatine substratum, owing to the penetration 
of the developer through the pores of the paper, and so make 
stripping difficult or impossible. 

For this reason most of those who make use of stripping 
films, adopt the oxalate of iron (ferrous oxalate) developer. 

The following formulae and directions are those recom- 



PAPER NEGATIVES. 141 

mended by the Eastman Co., for their films, but they will be 
found equally applicable to others : 

No. 1. 

Sulphite sodium, pure, crystals 6 ounces 

Distilled or boiled water, cold 1 qt. (32 ounces) 

Pyrogallic acid 1 ounce 

Dissolve the sulphite first and then add the pyro. 

No. 2. 

Carbonate soda, pure J^ pound 

Water 1 quart 

To develop, pour into a clean tray the following : 

No. 1. 1 ounce 

No. 2 1 ounce 

Water 1 ounce 

Immerse the exposed film in a tray of clean, cold water, and, 
with a soft camel's hair brush, gently remove the air bells that 
cling to the surface of the film. As soon as limp, remove the 
film to the tray containing the developer, and proceed with the 
development the same as with a dry plate. The image should 
commence to appear in ten or fifteen seconds. If the lights 
come slowly and with no detail in the shadows, add not to ex- 
ceed one ounce of No. 2. If the image appears too quickly, 
add ten to twenty drops of the 

Restrainer. 

Bromide potassium 1 ounce 

Water 6 ounces 

Keep this in a dropping bottle, consisting of an ordinary 
bottle having two notches cut lengthwise in the cork, on oppo- 
site sides. 

Oxalate Developer. The oxalate developer works well with 
Eastman's American films, and it has no tendency to attack 
the soluble substratum and render it insoluble. 

FORMULA. No. 1. 

Oxalate of potash 1 pound 

Hot water ... .48 ounces 



Acidify with Oxalic acid. 



142 THE PHOTOGRAPHIC NEGATIVE. 

No. 2. 

Proto-sulphate of iron 1 pound 

Hot water 32 ounces 

Tartaric acid 60 grains 

No. 3. 

Bromide potassium 1 ounce 

Water 1 quart 

These solutions keep separately, but must be mixed only for 
immediate use. 

To Develop. Take No. 1 , six ounces ; No. 2, one ounce ; 
No. 3, ten drops. Mix in the order given ; use cold. 

After exposure, soak the paper in water until limp, then 
immerse in the developer. 

The image should appear slowly and should develop up 
strong, clear, and brilliant. When the lights are sufficiently 
developed, wash well and fix. 

After fixing, wash in three or four changes of cold water for 
five or ten minutes, and the film is then ready for transferring. 

When the oxalate developer is used, it is sometimes advisable 
to use alum in the fixing-bath, to prevent frilling, but after 
using it the paper must be stripped as quickly as possible after 
squeegeeing on to the glass ; that is to say, after standing 
thirty minutes under pressure and before it becomes entirely 
dry, otherwise the substratum will become insoluble. 

The film may be examined from time to time by transmitted 
light, by holding it up by the corners. When sufficient density 
is obtained, wash the film in two changes of cold water, and 
then immerse in the 

Fixing-Bath. 

Hyposulphite sodium 4 ounces 

Water , 1 pint 

Mix fresh fixing-bath for each batch of negatives. Use no 
alum in the fixing-bath. 

Films fix quicker than glass dry plates, and the completion 
of the operation can be ascertained by the even, translucent 
appearance as seen from the back while lying in the bath, or 
by examination by transmitted light. 

Drying, Paper negatives, if not to be stripped, are best 



PAPER NEGATIVES. 143 

dried on a piece of glass, well polished with French chalk, or 
on a sheet of ebonite. The negative is squeegeed into contact 
with the glass or ebonite, and allowed to dry spontaneously. 
When dry it will peel off with a brilliant gloss. 

Oiling. Paper negatives, when dry, may be printed from 
without further treatment. It is better, however, to render 
them more translucent by oiling or waxing. Many methods 
have been advocated for increasing tranelucency. 

The author usually adopts the following method : The nega- 
tive is secured, face down, to a clean flat board, by thumb tacks 
at the corners. The oiling medium, castor oil, vaseline, or 
translucine, is then applied to the back ; the negative is then 
held over a stove and kept in constant motion until it assumes 
a uniform dark color. It is then allowed to cool, and a second 
coat of oil is applied and heated as before. All excess of oil 
is then removed with a piece of sponge or clean rag. 

Retouching. Paper negatives are best retouched from the 
back after oiling. The oiled surface takes the pencil readily, 
and any amount of working up may be given to the negative. 

Printing. Lay the negative, film side up, on a clean glass 
plate, secure the corners with gummed paper, and place in the 
printing frame. 

Preserving Paper Negatives. Place a sheet of oiled paper 
between the backs of the negatives and keep under pressure ; 
a deep printing frame makes a convenient press. 

Intensification, if necessary, should be done before the nega- 
tives are oiled. 

Stripping Films. The development of films which are to 
be stripped from their temporary supports is the same as that 
given above for paper negatives. 

After development, fixing, and washing, they are prepared 
for stripping in some one of the following methods : 

Eastmarts Method for "American Films" Coat a clean 
glass plate, one size larger than the film, with the following 
rubber solution : 

Rubber cement 1 ounce 

Benzine 9 ounces 

The above rubber cement is such as sold at the rubber stores 



144 THE PHOTOGRAPHIC NEGATIVE. 

in half-pound cans for 25 cents, and is a mixture of pure rub- 
ber and benzine. This article should not be mistaken for the 
bi-sulphide of carbon and rubber cement used by shoemakers. 
Allow the rubber to dry until " dead," say five or ten min- 
utes, then flow with plain collodion made as follows : 

Ether 1 ounce 

Alcohol 1 ounce 

Gun-cotton 12 grains 

As soon as set, wash under tap until greasy lines disappear, 
then slide the prepared glass into a tray of water, face up, 
slide the fixed and washed American film negative into the 
water over the plate, face down, grasp together by the edges 
and draw plate and negative out of the water, allowing to 
drain from one end. Carefully squeegee into contact, examin- 
ing from front for air-bells, place under blotter and weight to 
dry for thirty minutes only, then slide plate supporting the 
negative into a pan of water about 120 deg. to 140 deg. Fahr., 
raise corner of paper with a pin and pull it off, or slide the 
paper off from the glass sidewise, using gentle pressure, leav- 
ing the negative film on the glass. Brush gently with camel's- 
hair brush dipped in warm water, transfer plate to tray of cold 
water, negative side up, slide a gelatine skin of the proper size 
into water over negative, rough side up, allow skin to soak 
one minute, then grasp together with plate, and lift out of the 
water. Squeegee into contact, and stand to dry. When thor- 
oughly dry, flow with plain collodion. When dry, cut around 
the edges and peel off the glass ; remove adhering rubber from 
the face of the negative by gently rubbing with the palm of 
the hand, or with a tuft of cotton moistened with benzine. 

The sheets of gelatine are soaked for five minutes in the 
following bath : 

Water 35 ounces 

Alcohol 2% ounces 

Glycerine 2J ounces 

After soaking, a gelatine sheet is carefully placed on the 
film and lightly squeegeed into contact. When dry, the nega- 



PAPER NEGATIVES. 145 

live is stripped off as before. It is advisable, however, to col- 
lodionize the gelatine backing with plain collodion before 
stripping. 

Chennemere's Method. Stripping-films prepared according 
to M. Chenneviere's method are developed, fixed and washed 
as usual. They are then squeegeed into contact with glass 
plates previously polished with French chalk and collodionized 
with plain collodion. When dry, the negatives are cut 
through to the glass near the edges and pulled from the plates. 
The film is separated from the paper by inserting a knife-blade 
between the two at one corner and pulling them apart. 

Fabrds Method for Films on Paper Coated with Rubber. 
The washed negatives are squeegeed into contact with polished 
and collodionized glass plates. When dry, the back of the paper 
is covered with benzine and rubbed with a cloth dipped in 
benzine, to dissolve the rubber. The paper is then removed, 
the back of the film gently rubbed with a soft cloth dipped in 
benzine, to remove all traces of rubber. After drying, the 
films are coated with a plain collodion, and, when again dry, 
they are stripped from the glass as usual, first cutting around 
the edges. 

This method is applicable to all films united to paper sup- 
ports with wax or collodion, as in the methods of MM. Balagny 
and Milsom, given above. 

Films on Cardboard Supports are developed, fixed, washed 
and dried like glass plates. When dry, they are collodionized 
with plain collodion, and, when again dry, stripped from the 
cardboard support by inserting the point of a knife-blade be- 
tween the film and card at one corner and pulling them apart. 

The films are then placed in water in which a polished glass 
plate has been laid. After a moment's soaking, the collodion 
side of the film is brought in contact with the polished side of 
the glass, and the two removed from the tray. Perfect contact 
is secured with the squeegee, and the film allowed to dry. 
When dry, it is coated with plain collodion, and, when again 
dry, stripped from the glass as usual. 

Films on Gelatine or Collodion Supports. After the usual 
operations of development, fixing, and washing, M. Balagny 



14:6 THE PHOTOGRAPHIC NEGATIVE. 

recommends that these films be quickly blotted off between 
clean blotters. They are then immersed for five minutes in 
the following bath : 

Alcohol 16 ounces 

Glycerine 1 ounce 

They are then removed from the dish, drained for half a 
minute, placed between clean blotters and laid down on a glass 
plate. A piece of rubber cloth is next laid over the blotters 
and gently pressed with a roller, to remove all excess of mois- 
ture. This process is repeated three or four times, changing 
the blotters each time. The films are then dried thoroughly 
between fresh sheets of blotting-paper. 

These flexible plates, as the inventor calls them, are superior 
to films on paper or cardboard, in that they allow the progress 
of development to be watched by transmitted light. 

The author, however, has found no insuperable difficulty in 
judging of the density of films on paper or cards by reflected 
light. His practice is to develop until the shadows begin to 
gray over, and then to wash and fix as usual. 




CHAPTEK XIII. 

FAILURES IN THE GELATINO-BROMIDE PROCESS. 

MOST of the possible causes of failure with this process with 
the proper remedies, will be found enumerated in this chapter. 

Fluidity of the emulsion in the flask. This is usually due 
to failure to add an antiseptic to the emulsion. Such an emul- 
sion will not set, and is not safe to use. 

Irregular flowing of the emulsion is most commonly due to 
the want of a substratum, and may be corrected by applying 
any of the substrata given in Chapter IV. 

Wavy and irregular lines during coating are caused by 
the plates being too cold, or the emulsion not being sufficiently 
fluid. The plates should be warmed slightly, and the emulsion 
kept at a temperature of about 95 deg. 

Refusal of the emulsion to set may be due to high tempera- 
ture of the coating-room, or to a deficiency of gelatine in the 
emulsion, or to a decomposition of the gelatine, caused by long 
boiling, excessive use of ammonia, or frequent re-meltings. If 
the defect is due to the first cause, lower the temperature of 
the coating-room, which should always be at about 70 deg. 

If the gelatine be deficient, add 25 or 30 grains of gelatine 
to every 2 drams of emulsion, and, after standing for a few 
hours, dissolve in the water-bath. 

In the third case it is best to reject the emulsion. 

Spots and small rings are due to the irregular drying of the 
plates. The door of the box or room in which the plates are 
dried should be opened as little as possible during the drying. 

Fog is due to several causes, as over-exposure, forced devel- 
opment, admission of white light, or too long an exposure to 
the light of the dark-room. 

If the edges of the plate, which were protected by the re- 



14:8 THE PHOTOGRAPHIC NEGATIVE. 

bate of the frame, are free from fog, the plate was over 
exposed. 

If the whole plate fogs over during development, it is either 
light-struck, or the emulsion was fogged. 

This point may be determined by developing and fixing an 
unexposed plate. If this shows no signs of fog, the camera or 
the slide is at fault, and must be examined. 

Fog on unexposed plates may be due to some fault in the 
making of the emulsion, or to the slow drying of the plates. 

Fogged emulsion may occasionally be made fit for use by the 
addition of a few drops of tincture of iodine. 

Plates which have been coated and show signs of chemical 
fog should be soaked in the following bath : 

Bichromate of potassium 1 part 

Hydrochloric acid 3 parts 

Water 100 parts 

After this treatment the plates are well washed and then 
dried. 

Yellow fog occurs only with the alkaline developer ; it is 
due to the staining action of pyro on the film, and may be re- 
moved by soaking the plates, after fixing, in a saturated solu- 
tion of alum, to which one per cent, of hydrochloric acid lias 
been added. 

lied fog is caused by an excess of nitrate of silver used in 
the emulsion. It also sometimes occurs when the plate has 
been long subjected to the action of a concentrated oxalate of 
iron developer. 

Green fog is most commonly caused by an excessive amount 
of ammonia in the developer. It may sometimes be removed 
by soaking the plate in a solution of peroxide of hydrogen. 

A slight green fog does not injure the printing qualities of 
the negative. If, however, the fog is very dense, it may be 
cleared away by converting the deposit into chloride of silver, 
by means of perchloride of iron solution, to which a trifle of 
bromide of potassium has been added, and an after re devel- 
opment with ferrous oxalate. If the original deposit chances 
to be too feeble for printing, expose the chloride of silver de- 



FAILURES IN THE GELATINO-BROMIDE PROCESS. 149 

posit to day-light before re-developing, which will increase the 
density very much. 

A white opalescent veil, covering the film, is sometimes met 
with in plates developed with oxalate of iron, when lime is 
present in the water. It has no injurious effect, but may be 
removed by soaking the plate in dilute hydrochloric acid. 

A yellow deposit forms on the film when using the oxalate 
of iron developer, owing to an excess of sulphate of iron hav- 
ing been added to the oxalate of potassium. 

Undefined marks and spots on the film after development 
are due to grease in the gelatine. Emulsion prepared with 
ammonia is free from this defect. 

Pinholes are caused by dust on the plate. 

White marks or round spots are caused by air bubbles form- 
ing on the film during development. This may be prevented by 
soaking the plate in water before developing, or by keeping 
the developer in motion. 

Lack of detail is caused by insufficient exposure, by want of 
sufficient alkali in the developer, or by the excessive use of the 
restrainer. 

Want of density is due to over-exposure or to the use of 
a weak developer. 

Excessive density is caused by over-development. 

Halo around the high lights, is generally due to the reflec- 
tion of light from the back of the plate. It may be, in part 
prevented by backing the plate with some non-reflecting color, 
mixed with gum water. 

Matt surface plates, and those containing iodide of silver, 
are usually free from this defect. 

Frilling of the film during development is most commonly 
caused by the use of soft gelatine in the preparation of the 
emulsion. The formation of frills and blisters is promoted by 
the addition of too much alkali to the developer, by the use of 
warm developers and wash-waters, by treating the plates 
with dilute acid solutions to remove fog or stains, and by the 
use of a concentrated fixing-bath. 

Films which show a tendency to frill should be treated be- 
fore or after development with 10 per cent, chrome alum solu- 
tion. 



150 THE PHOTOGRAPHIC NEGATIVE. 

Frills showing during development may be arrested by add- 
ing a teaspoonful of saturated solution of Epsom salts (sul- 
phate of magnesia) to the developer. Plates with a tendency 
to frill should be placed in the alum-bath. 

The best remedy for frilling is to work in a low tempera- 
ture. Let the amateur defer developing, during hot summer, 
to the early morning hours, if he has no means of lowering 
the temperature of his work-room or water by artificial means. 

Soaking in alcohol will usually remove films by the absorp- 
tion of the water under them. 

Slow fixing is due to the use of a too dilute, or too concen- 
trated, hypo-solution for fixing. The proper strength is 1 to 
5. Plates containing iodide are always slow to fix. 

Spots and Stains appear on the films when intensified with 
mercury, owing to insufficient washing after fixing, or after 
the treatment with mercury. 

Red stains, which appear on the films after having been 
printed from, are caused by the silver in the paper, combining 
with the gelatine. They can sometimes be removed by soak- 
ing the films in dilute cyanide of potassium, accompanied by 
gentle rubbing, but this method is very dangerous. Dr. Ehr- 
mann recommends that a line be drawn around the stains with 
a piece of wax sharply pointed ; the film is then softened in 
water, and the spots are treated with cyanide of potassium 
solution applied with a fine brush. 

Farmer's or Belitzki's reducing solutions, given on page 
128, may also be applied in the same way. 

The wax is removed with a tuft of cotton, moistened with 
ether. 



CHAPTER XIV. 

METHODS OF STRIPPING FILMS FROM GLASS PLATES. 

MOST of the mechanical printing processes require reversed 
negatives or positives for the production of the printing 
plate. 

In such cases, unless a reversed negative was obtained in the 
camera, by the use of a reversing prism, or by exposing through 
the glass support, it is necessary to strip the film from the 
plate, in order to turn it and print from the reversed side. 

The use of stripping films, prepared according to the in- 
structions given in the previous chapter, gives negatives which 
can be printed from either side. 

A few of the best methods for stripping are given below. 

Collodion Films. The plates are collodionized without be- 
ing given a substratum. If the negatives have been varnished, 
the varnish is removed by pouring over them sufficient of the 
following solution to cover them well : 

Distilled water 5 ounces 

Caustic potash 120 grains 

Alcohol 17% ounces 

The alcohol is used to neutralize the destructive effect of 
the alkali on the film. 

As soon as the varnish is dissolved the negative is well 
washed in pure water, levelled, and coated with a solution of 
six parts of gelatine in forty parts of water, to which from 
four to five parts of alcohol, and from one-half to one part of 
glycerine have been added. When the gelatine has thoroughly 
dried, the film is cut around the edges and stripped from the 
glass. 

For " process work " the film is turned by coating the nega- 
tive, when dry, with a solution of Para gum in benzine, and 



152 THE PHOTOGRAPHIC NEGATIVE. 

afterwards with a tough collodion. When this is dry the film 
is cut as before, and is immersed in a 1 to 10 acetic acid 
solution. As soon as the film floats off it is turned upon 
another glass plate placed in the solution, or glycerine. When 
again dry, the film may be pulled from the glass after cutting 
around its edges. 

Gelatine Films. Unless specially prepared for stripping, 
gelatine films must be treated with a 20 per cent, chrome alum 
solution, for at least one hour, and then immersed in a 20 per 
cent, hydrofluoric acid solution until the film leaves the glass. 
A polished and collodion ized plate is placed in the tray, under- 
neath the film, and both removed from the water, and laid 
down on a plain surface. A piece of sheet gelatine, previously 
soaked in water, containing 2 per cent, of glycerine is then 
brought in contact with the film, and, when dry, the film 
is easily detached from the glass. 

A better method is to prepare the plates for stripping before 
they are coated. This is easily done by polishing them with 
French chalk, and collodionizing them with a plain collodion 
containing 1 per cent, of pyroxyline, first taking the precau- 
tion to remove the chalk from the edges of the plate, for about 
an eighth of an inch, with a wad of cotton wool, dipped in 
albumen. The plates are then coated with the emulsion. 

To effect the transfer it is only necessary to cover the film 
after fixing, and washing with water containing 2 per cent, of 
glycerine, and then .to lay over it a piece of sheet gelatine, 
previously soaked in the same glycerine solution. The whole 
is then covered with a piece of rubber cloth, and gently 
squeegeed. 

When the gelatine sheet is dry it is collodionized, dried, and 
stripped, as described on page 144. 






CHAPTEK XY. 

COLOR-SENSITIVE PLATES. 

Isochrotnatic or Orthochromatic Methods. The ordinary 
photographic plate, whether prepared by any of the well- 
known albumen, collodion, or gelatine methods, is deficient in 
its power of giving proper tone-value to the different colors. 
It does not render them with the same relative force with 
which they impress themselves upon the retina. Some colors 
appear too dark ; others too light in the finished print. 

Prof. Draper was the first to discover the fact that only the 
absorbed rays produce chemical changes in a sensitive surface. 

The knowledge of this fact was the starting point in the 
search for substances which should make sensitive plates prop- 
erly color-sensitive, by conferring upon them the property of 
translating the different colors of the spectrum into their true 
values in light and shade. 

In this connection special mention is made of Angerer, 
Eder, Obernetter, Scolik, Mallmann, Ducos du Hauron, Cros, 
Tailfer, Josef Albert, Schumann, Yogel, Ives, Ehrmann, 
Abney, and Bierstadt, as investigators of this somewhat ob- 
scure branch of photography. 

As the result of these investigations, it is now possible to 
prepare sensitive plates which will render, with great fidelity, 
the varying intensities of different colors. 

The method is of great value in the reproduction of oil 
paintings, water-colors, colored fabrics, and, in general, of all 
objects in which there is a large proportion of red and yellow 
rays. 

The problem to be solved was a method of treating emul- 
sions or prepared plates, which should increase their absorp- 
tion for rays which are but feebly absorbed by ordinary 
plates. 



154 THE PHOTOGRAPHIC NEGATIVE. 

Two methods were found available to effect this result, one 
being to color the emulsion with certain dyes, the other, and 
more practical, being to bathe plates, prepared as usual, with a 
dilute solution of the same dyes. 

It was also found necessary to interpose between the sensi- 
tive surface and the lens, or to place in front of the lens, col- 
ored screens in order to modify the action of the light to 
adapt it to the work it was called upon to perform. 

Of the dyes most commonly used in the preparation of 
color-sensitive plates, those belonging to the eosine group have 
given the best results. Chinoline, and many others too numer- 
ous to mention, have also been successfully employed by dif- 
ferent experimenters. 

Without attempting to discuss the subject exhaustively, it is 
intended to give sufficiently detailed instruction, drawn from 
the best sources, to enable the intelligent operator to produce 
good results. 

The Light Screen. The light reflected from the object to 
be reproduced is passed through a colored glass screen before 
falling upon the sensitive plate, in order to equalize the chem- 
ical action of different colored rays. The shade and depth of 
color of this screen are somewhat varied to adapt it to special 
needs. The color in most common use is yellow, but the 
color is often modified to suit the prevailing tints of the ob- 
ject to be reproduced. In many cases a slight tinge of red, 
blue, or green is advisable. Such screens are easily prepared 
by coating a piece of clean plate-glass, free from scratches and 
bubbles, with a plain collodion, to which sufficient of some 
yellow dye has been added to impart the desired tint aurantia 
or dimethyl orange and tincture of Bengal curcuma answer 
well for this purpose. 

Ives prefers to use a plate-glass cell, filled with a solution of 
bichromate of potash. 

Some experimenters strip the colored collodion film from 
the glass, cut it to the size and shape of the lens, and mount 
it with the lens in the tube. The screen may be placed in 
front of or behind the lens. In many cases, especially where 
the object is lighted by yellow light, the screen may be dis- 
pensed with. 



COLOR-SENSITIVE PLATES. 155 

The use of the screen materially lengthens the time of ex- 
posure, which can only be learned by practice. 

Color-Sensitive Gelatine Emulsion. Gelatine emulsion 
may be made color-sensitive by the addition of eight drops of 
a one to 500 eosine solution to every three and a half drams 
of emulsion. Cyanine, erythrosine, chinoline, or other dyes 
maybe used. 

Color-Sensitive Bath-Plates. Tailfer, in France ; Schu- 
mann, Angerer, in Austria ; Ives, Bierstadt and Ehrmann, in 
America, were the first to demonstrate the possibility of ren- 
dering ordinary gelatine plates color-sensitive by immersion in 
a batli of the dye-stuff. 

This method is superior to the older one of adding the dye 
to the emulsion, and it is, therefore, to be preferred, both on 
account of its simplicity, certainty, and a general excellence. 

Scolik's Method, with Erythrosine. 

1. PREPARATORY BATH. 

Water 7 ounces 

Ammonia 35 drops 

The plates are immersed for two minutes in this bath, to 
secure an even action of the color-bath, and to increase sensi- 
tiveness. 

2. COLOR BATH. 

Erythrosine solution (one to one thousand) 7 drams 

Ammonia 1 dram 

Distilled water 6J^ ounces 

The plates are bathed in this solution from sixty to ninety 
seconds, rocking the tray gently. 

They are then dried in the dark. These two baths are 
sufficient for one dozen plates, but fifteen drops of ammonia 
must be added to each bath after seven or eight plates have 
been treated. Exposure through the yellow screen is from 
three to six times that necessary with the original emulsion. 

If the plates are very rapid, the amount of ammonia in both 
baths should be diminished one-half. 

For portraits the yellow screen is unnecessary, unless blue or 
red appear in the draperies. 



156 THE PHOTOGRAPHIC NEGATIVE. 

The addition of a few drops of a one to five hundred eosine 
solution to the erythrosine bath will increase the sensitiveness 
to red. 

Prof. Ehrmann's Formula. 

1. THE PRELIMINARY BATH. 

Ammonia 1 dram 

Water 7 ounces 

2. THE COLOR BATH. 

Erythrosine 1J drams 

Ammonia 2 drams 

Distilled water 5% ounces 

The plates are bathed as before. 
VogeVs Method with Azaline*. Sensitive to red. 

Azaline alcoholic solution (1 to 2,500) 340 drops 

Ammonia 34 drops 

Water 22% drams 

The plates are bathed for one minute and then dried. A 
yellow screen is used, and the exposure is three or four times as 
long as with wet plates. 

These plates will keep from four to six weeks. 

Obernetter and VogeVs Erythrosine Bath. Sensitive to yel- 
low; good for landscapes containing much green and blue. 

Erythrosine, aqueous solution (1 to 1,000) 14 drams 

Silver solution (1 to 1,000) 14 drams 

Ammonia 34 drops 

Water 3^ ounces 

The solution is filtered, and the plates are bathed in it for 
one minute, and then dried. 

Exposure is made through the yellow screen. 
The plates will keep one week. 
Development is effected in the following : 

1 . Sulphite of soda 3 ounces 

Pyro 3% drams 

Water 17> ounces 

* According to Mallmann and Scolik's analysis, azaline is a com- 
pound of chinoline red and chinoline blue (cyanine), 500 c. c. m. contain- 
ing one gramme of red and one decigramme of blue. 



COLOR-SENSITIVE PLATES. 157 

2. Carbonate of soda 1J ounces 

Water 35 ounces 

Mix one volume of No. 1 with two volumes of No. 2. 
Schumann's Method with Cyanine. 

1. PRELIMINARY BATH. 

Water 7 ounces 

Ammonia J^ to 1 dram 

2. COLOR BATH. 

Distilled water 7 ounces 

Alcohol 3 drams 

Ammonia 68 drops 

Alcoholic solution of cyanine (1 to 500) 3 drams 

Immerse the plates for two or three minutes in No. 1, and 
then treat with No. 2 for ninety seconds. 

Expose through the yellow screen, and develop with the 
following : 

1. Sulphite of soda 6 drams 

Sulphuric acid 8 drops 

Pyro 2 drams 

Water 3J ounces 

2. Carbonate of potash 3 drams 

Sulphite of soda 6 drams 

Water 7 ounces 

Start development with the following weak developer : 

Solution No. 1 6 drops 

Solution No. 2 6 drops 

Bromide of potassium solution (1 to 10) 1 drop 

Water 2 ounces 

adding more pyro, if necessary. 

Obernetter* s Method with Fluoride of Silver. The plates 
are washed with distilled water for one minute, then drained 
and covered one minute with a solution of fluoride of silver 
(1 to 2,000). They are next washed slightly under a tap, and 
the following solution flowed over them three times, in differ- 
ent directions : 

Erythrosine solution (1 to 1,000) 7 drams 

Azaline solution (1 to 2,000) 35 drops 

Carbonate of ammonia solution (1 to 6) 14 drams 

Water 35 ounces 



158 THE PHOTOGRAPHIC NEGATIVE. 

The plates are then drained and dried. 

No yellow screen is necessary with these plates. 

The alkaline pyro developer is to be preferred. 

If the plates fog in the developer, the usual bromide of 
potassium restrainer must be used. 

Wellington's Method. The plates are immersed for two 
minutes in the following bath, then rinsed and dried : 

Nitrate of silver 20 grains 

Carbonate of ammonia 90 grains 

Erythrosine solution (1 to 500) 10 drams 

Distilled water 16 ounces 

To avoid fog the exposed plates are immersed for twenty 
seconds before development in the following bath : 

Bromide of potassium 120 grains 

Ammonia 4 drams 

Water. 10 ounces 

Then well rinsed and developed with any good developer. 

The use of the yellow screen is unnecessary if the exposures 
are to be made by gas or lamp-light. For day-light expos- 
ures the screen must be used if the object to be copied contains 
much blue. 

The interesting feature about the two last-mentioned methods 
is that they seem to disprove the commonly accepted absorp- 
tion theory, according to which the function of the various 
dyes is to act simply as optical sensitizers, by increasing the 
absorption power of the film for certain colors. 

But the fluoride and carbonate of silver processes seem to 
prove that the orthochromatic effect is due rather to a chemi- 
cal change, produced by the presence of free silver and a new 
compound formed with dye. 

The theory is now meeting with general adoption, and it 
makes the function of the dye, in combination with a sensitive 
silver haloid, that of a color-screen merely, each dye acting 
according to its color or shade of color. 

The fact that Ducos du Hauron and Edward Bierstadt have 
been able to secure good orthochromatic effects by exposing 
ordinary collodion or gelatine plates through variously colored 



COLOR-SENSITIVE PLATES. 159 

glasses, or cells, filled with colored liquids, seems an additional 
argument in support of this theory. 

Development. The use of color-sensitive plates necessitates 
no changes in the ordinary process of development, which may 
be effected with oxalate of iron or the alkaline developer. 

Great care must be taken not to expose the plates to the 
direct rays of the dark-room light, until development is well 
started. 

Schumann and Eder recommend the use of three thicknesses 
of brown tissue-paper as a safe medium through which to filter 
the light. 

Eder's Method of Developing Color-Sensitive Plates. Dr. 
Eder prefers the oxalate of iron developer, and begins devel- 
opment with an old developer. A properly-exposed plate 
should show all the details in from five to ten minutes, but the 
image will probably be weak. In this case it is necessary to 
add to the old developer one-half, or an equal bulk of freshly 
mixed developer, and to prolong the development ten minutes. 

In some cases the development must be continued for thirty 
minutes. Slowly developed negatives give the best results. 

Angerer, Scolik, Schumann, Ehrmann, and others, prefer 
the potash developer for the development of color-sensitive 
plates. 

Captain Abney has recently made the discovery that all that 
is necessary to render any plate color-sensitive is to coat it 
with a solution of the dye (eosine, cyanine, etc.), in alcohol or 
collodion. The action of light taking place at the surface of 
the plate, it is said to be sufficient to have the dye in contact 
with the surface molecules only. 

Coming from so high an authority, the new method is pre- 
sumably practical; but further knowledge of the results is 
necessary before accepting it as a rival of older and well-tried 
methods. 



CHAPTER XYI. 

BLACK AND WHITE NEGATIVES. 

MOST of the mechanical printing processes require negatives 
of greater density than is necessary or desirable in negatives 
used solely for printing upon sensitized paper. 

All the details of lines or lettering must be reproduced with 
perfect sharpness in the negative, the high lights being in- 
tensely black to prevent the light from penetrating through on 
to the bichromatized gelatine plate beneath. Such negatives 
are technically known as "black and white negatives." 

The favorite process for the production of this class of work 
has long been, and still is, wet collodion. Undoubtedly it is 
possible to produce negatives of abnormal density on gelatine 
plates, as will be described later in the chapter, but the wet 
collodion, in the opinion of those most skilled in this class of 
work, offers greater facilities in working, and produces better 
and more uniform results. 

The directions given in the following pages are based on 
articles on this subject which appeared in The Photographic 
Times. 

Wet Collodion Process. While any good collodion may be 
used, the following is especially recommended : 

Alcohol 5 ounces 

Ether 5 ounces 

Iodide of ammonium 50 grains 

Bromide of ammonium 20 grains 

Pyroxyline 50 grains 

The silver bath should be acidulated with acetic acid, which is 
better suited to vigorous development, and decreases the like- 
lihood of a foggy deposit upon the clear portions of the nega- 
tive. 



BLACK AND WHITE NEGATIVES. 161 

The plates are collodionized and sensitized as usual. 

The time of exposure is a factor of great importance in this 
class of work. If the plate is under-exposed, the lines will be 
rough and heavy. If over-exposed the fine lines or stipple are 
blocked up. A correctly exposed plate shows the finest lines 
only feebly. 

The development should not require longer than three or 
four minutes, or the negative will suffer. The following de- 
veloper gives good results : 

Water 16 ounces 

Sulphate of iron 1 ounce 

Acetic acid 1 ounce 

to which 1 dram of sulphate of copper may be added to give 
more solidity to the deposit. 

The negative, after development, should be rather thin, and 
will need to be intensified. The best and safest method is that 
of Dr. Eder, with nitrate of lead. 

The negative, after fixing and a thorough washing, is im- 
mersed in the following bath : 

Nitrate of lead 2 ounces 

Red prussiate of potash 3 ounces 

Water 50 ounces 

The bath must be filtered. 

In this bath the color of the negative soon changes to a 
yellowish-white, which must be allowed to deepen until the 
proper degree of density is reached. 

The chemical action of this bath is thus explained. The 
silver in the image acts as a reducing agent, and deoxidizes the 
ferri-cyanide to ferro-cyanide, which unites with the nitrate of 
lead to form the insoluble ferro-cyanide of lead. 

After being removed from the lead bath the negative is 
washed until the drainings give no blue precipitate when the 
sulphate of iron is added. It is then blackened by immersion 
in a 1 to 6 solution of hydro-sulphate of ammonia. The ac- 
tion of this bath is continued until the film is black on both 
sides. The negative is then well washed, and should show 
great clearness in the lights, and great density in the ground. 



162 THE PHOTOGRAPHIC NEGATIVE. 

If sufficient density was not conferred by the lead bath, the 
negative may be whitened in a 1 to 10 sulphate of cadmium 
solution, then washed and blackened as before with ammonia, 
which transforms lead, cadmium, and silver into the corres- 
ponding sulphides. 

Yellow fog or stains are due to insufficient washing after 
fixing, but they can be removed by flooding the plate with a 
sherry-colored solution of iodine and iodide of potassium, fol- 
lowed by fixing in a weak cyanide of potassium bath. 

Negatives properly intensified with nitrate of lead, are won- 
derfully clear in the lines, of great density, and produce fine 
and high reliefs on bichromatized gelatine. 

Stripping. Negatives intensified with lead are stripped by 
coating the films first with a 5 grain solution of pure india- 
rubber in benzine, and then with a tough plain collodion. 
When dry the edges of the film are cut through to the glass, 
and the plate immersed in 1 to 10 acetic acid solution. The 
film soon loosens, and may then be detached from the plate. 

Gelatine Process. The great convenience attending the use 
of gelatine emulsion plates has led to many experiments for 
the purpose of giving the negatives on gelatine films the quali- 
ties necessary for mechanical printing. 

For this purpose plates of a low order of sensitiveness are 
correctly exposed, and developed with the oxalate of iron de- 
veloper, to each eight ounces, of which have been added fifty 
drops of the following solution : 

Iodine 10 grains 

Iodide of potassium 10 grains 

Water .... 3 ounces 

As soon as the image appears, a small quantity of the bro- 
mide of potassium restrainer should be added. 

Properly exposed plates thus developed will need no intensi- 
fication. 

If the negatives are not sufficiently intense they may be 
strengthened by whitening the films in the following bath : 

Chloride of ammonium 16 grains 

Bichloride of mercury 1 dram 

Water. . 24 ounces 



BLACK AND WHITE NEGATIVES. 



163 



The negatives are then most thoroughly washed and treated 
with the following : 

Cyanide of potassium 30 grains 

Iodide of potassium 15 grains 

Bichloride of mercury 15 grains 

Water 7 ounces 

After reaching a certain degree of density in this bath the 
reducing power of the cyanide begins to show itself, and the 
density is thus reduced. By taking advantage of this fact the 
operator can easily determine the character of the negative. 




CHAPTER XYIL 

INSTANTANEOUS PHOTOGRAPHY. 

THE time of exposure necessary to imprint a developable 
image on the sensitive surface, has been reduced to the one 
twenty-six-hundredth part of a second, and even lower, under 
exceptionally favorable circumstances. 

This great increase in sensitiveness has opened a new and 
delightful field to the photographer, making it possible for 
him to give graphic delineations to fleeting effects of motion, 
expression, and grouping, which but lately were impossible of 
exact and accurate delineation. 

The detective camera has become a necessary part of the 
photographic outfit, and the tourist who is provided with one 
of these modern instruments, finds little difficulty in securing 
interesting studies of the lands and peoples visited by him. 

But instantaneous photography, with detective cameras and 
highly sensitive plates, is not so certain as the more common 
method of longer exposures on slower plates. 

If the development of a correctly-timed exposure is a deli- 
cate operation, much more delicate is it to coax a good print- 
ing image from a plate which has received an exposure of 
only a fraction of a second. 

It is, however, but a transfer of difficulties and perplexities 
from one stage of the process to another. In the case of a 
timed exposure the operator's judgment is most exercised to 
determine the length of exposure best suited to the view be- 
fore him. 

"With instantaneous exposures, however, it is in development 
that good judgment is most needed to make the most possible 
out of the plate. 

He who would be successful in instantaneous work must 



INSTANTANEOUS PHOTOGRAPHY. 165 

have a thorough knowledge of the plate used, the distance and 
illumination of the object, and the conditions of development. 

It is taken for granted that the plates used have at least as 
high a sensitometer number as 25, which is rapid enough for 
most purposes, and even in the detective camera they are 
more often over than under-exposed, owing to the use of a 
diaphragm with too large an opening. 

The distance and illumination of the object determine the 
amount of light to be admitted, and, consequently, the size of 
the diaphragm and the speed of the shutter. 

Objects near at hand require the admission of more light 
than those at a distance, because their actinic force is dis- 
tributed over a larger area of sensitive surface. 

If the illumination is from behind the camera, a smaller 
diaphragm may be employed than when the shadows fall 
transversely across the field. 

Objects in shadow will require a larger diaphragm than 
those fully illuminated. 

In general it may be said that the best effects, both as 
regards definition and tone, are secured by using a medium- 
sized diaphragm and increasing or diminishing the speed of 
the shutter. 

The following table is given as the results of the author's 
experiments with a Morrison lens of 8-inch focus, using No. 
25 plates. 

For brightly-illuminated landscapes, with rapid shutter, use 
diaphragm opening T ^-. 

For seascapes, with quick shutter, use ^. 

For figures, animals, etc., in the foreground, use T , with 
moderate speed. 

For thick foregrounds, with foliage in the middle distance, 
use full opening, with fair speed of shutter, or, for better 
definition, y^-, with slower shutter. 

For buildings and confined scenes generally, when well 
illuminated, use T ^-,.with moderate speed. 

These may be taken as standard measurements, and the 
resulting exposures, if properly developed, will yield negatives 
with sufficient pluck to print well. 



166 THE PHOTOGRAPHIC NEGATIVE. 

Development. Instantaneously exposed plates should be 
developed slowly, using a developer weak in pyro and alkali, 
and the plate should be protected from the action of the light. 

The following method is given, not as the best or only pos- 
sible one, but as the one which has given the author uniformly 
good results. 

The developer is compounded as follows : 
No. 1. 

Pyro 1 ounce 

Sulphite of soda 1 ounce 

Sulphuric acid 10 drops 

Water 10 ounces 

Dissolve the soda first, then the pyro, and then add the sul- 
phuric acid. 

No. 2. 

Carbonate of potash 1 ounce 

Sulphite of soda f 1 ounce 

Water 10 ounces 

One dram of each of these solutions contains six grains of 
pyro, sulphite and carbonate. 
To develop. Take 

Water 4 ounces 

Solution No. 1 1 dram 

Solution No. 2 1 dram 

Immerse the plate in this and cover the tray with an opaque 
screen. If after two or three minutes the high lights do not 
appear, add half a dram of No. 2. As much as four drams of 
No. 2 can be added without producing fog, but in most cases 
two to three drams will be found sufficient. 

As soon as the details are well out, add one dram of No. 1, 
and continue the development until the image is visible at the 
back of the plate. Instantaneous exposures seem to lose more 
density in the fixing-bath than timed exposures, therefore they 
should be developed further. 

If, after the addition of two drams of No. 2, the details still 
hang back, do not seek to hasten matters by the addition of 
more alkali, but dilute the developer one-half with water, or 



INSTANTANEOUS PHOTOGRAPHY. 167 

remove the plate from the tray and immerse in a weak alka- 
line solution (one dram of No. 2 to four ounces of water) until 
the details appear, then return to the developer to which the 
second dram of No. 1 has been added. 

It will generally be advisable to give the plates a prelimin- 
ary soaking for two or three minutes in the weak alkaline 
solution, given above, before applying the developer. This 
method is valuable in the case of heavy foliage and dark 
shadows. 

If the image flashes up immediately, add a few drops of a 
ten per cent, solution of bromide of potassium. 

The following method of developing instantaneous expos- 
ures with Beach's formula, given on page 121, is taken from 
the Photographic Times. 

"Take of solution No. 1, or pyro, 45 or 50 minims, and 
mix with 3 fluid ounces of water, not too cold about 60 deg. 
in summer and 70 deg. in winter is most satisfactory. Add 
30 minims of the No. 2, or potash, solution, and flood the 
plate without previous soaking in water. Have at hand, in 
soak in a basin of clean running water, a wide camel's-hair 
brush, such as is commonly sold for dusting off plates, and 
with it lightly brush the surface of the plate under the liquid, 
to prevent air-bells and pin-holes. The picture will come up 
slowly and steadily, and should be pushed to considerable den- 
sity, until the outlines begin to " sink in." When the plate is 
held up to the red light, the dark parts should be of an opaque, 
velvety black, and a dim, but clear, ruddy glow ought to shine 
through the lighter details. Looked at on the wrong side, the 
image should be discernible. It is safer to press the develop- 
ment a trifle too far than to halt too soon, for it is always easy 
to reduce an over-developed plate , but in practice there is not 
much likelihood of over-intensity in a well-timed instantaneous 
plate, for it loses density prodigiously in fixing. Wash well 
before fixing, and when the whiteness goes off, transfer to a 
cool bath of fresh hyposulphite, and let it soak for a few 
minutes longer. 

It sometimes happens that, even with this weak developer, 
the image conies up too rapidly, giving full details while den- 



168 THE PHOTOGRAPHIC NEGATIVE. 

sity lags. In such cases, add half a dram more of the pyro- 
gallol mixture and ten or fifteen drops of the following 
solution : 

Water 4 ounces 

Sodium sulphite 1 ounce (437 grains) 

Sodium carbonate (chem. pure, dry) 1 ounce (437 grains) 

Ammonium bromide 20 grains 

On the other hand, if the image shows undesirable contrast 
and backwardness in the details, the developer should be fur- 
ther diluted with an ounce of water, and ten, or even twenty, 
drops of the standard No. 2 (potash) solution added." 

The careful study of these two methods will enable the 
intelligent operator to employ any alkaline developer for the 
development of instantaneous exposures. 




CHAPTEE XVIII. 

TOUCHING UP THE NEGATIVE. 

NEGATIVES are rarely perfect in every respect when fin- 
ished. There is often a want of harmony, frequently an over- 
abundance of pin-holes. These and various other defects 
necessitate judicious doctoring before good prints can be ob- 
tained. 

Avoiding any discussion concerning the retouching of por- 
trait negatives as too difficult and serious a matter to be ade- 
quately treated in a general work like the present, a few 
methods of improving poor negatives and remedying the 
defects of faulty ones will be briefly indicated in the present 
chapter. 

A very common fault, in landscape negatives, is a want of 
harmonious blending of the tones; the high lights are too 
dense, the shadows too thin. Such a negative, if printed from 
without any touching up, would give very unsatisfactory 
prints. 

The shadows must be brought up to the proper density to 
print well with the high lights. 

A common method of securing this end is to paste tissue or 
tracing paper over the back of the negative, cutting out 
the high lights with a sharp penknife. In this way the den- 
sity of the shadows is increased ; the effect may be hightened 
by applying black lead with a stump to the parts which re- 
quire it. 

Another very efficient means of securing better gradation, . 
is to coat the back of the plate with a plain collodion, to which 
a tinge of red or yellow has been given by the addition of 
aniline dyes. This method is particularly good for strength- 
ing weak negatives, as any desired depth of color may be 



170 THE PHOTOGRAPHIC NEGATIVE. 

given to the collodion by increasing the amount of dye 
added. 

The author much prefers, to either of these methods, the use 
of the mat varnish, the formula for which is as follows : 

One dram of powdered sandarac is dissolved in fourteen 
drams ;of ether, fifteen grains of Canada balsam, and five or 
six grains of pure benzine or benzole are then added and the 
varnish filtered. It is applied by flowing it over the back of 
the negative, which is not warmed. If one coating does not 
give sufficient density two or three may be given. 

The advantage of this varnish is that it may be removed 
from the denser portions of the negative with a brush dipped 
in mastic varnish, and that it admits of any amount of re- 
touching with plumbago and the stump, or with the pencil. 

If desired, the varnish may be colored with aniline dye. 

Pinholes, scratches, and other defects of a similar nature, 
should be touched up with India ink applied with a very fine 
brush. The ink should be used nearly dry and laid on thinly, 
to attain, as far as possible, the density of the surrounding 
parts. 

Local reduction of density may be effected by rubbing the 
over-dense portions with a piece of fine linen drawn over the 
finger end and moistened with alcohol, or by mixing a small 
quantity of any of the reducing agents, given on page 128. 
with gum water, and applying the mixture with a brush. 

Local intensification may be produced in the same way. 

These general hints are sufficient to enable the skillful 
operator to improve the printing quality of defective nega- 
tives, which is their only aim. 



CHAPTER XIX. 

PHOTO-MICROGRAPHY. 

PHOTOGRAPHY has proved a most useful handmaid to micro- 
scopy, and the photographic camera has, to a large extent, 
emancipated the microscopist from the camera lucida. Vari- 
ous methods have been devised for the photographic reproduc- 
tion of the highly magnified images given by the microscope, 
some of the best of which have been selected for description. 

Mercer's Plwto-j&Licrograpliic Camera. This instrument 
is so well illustrated in Fig. 30 as to require but little further 
explanation. It is light and portable, and can be used with the 
microscope in any position. It is used in connection with the 
eye-piece, and carries plates measuring 2| by 3^ inches. 

Its essential parts consist of a small box, to which is at- 
tached a brass cone provided with a draw tube for insertion 
into the body of the microscope. The weight rests upon the 
brass arm, as shown, none of it being upon the sliding parts. 
Coarse adjustment is made by sliding the instrument up and 
down on the arm; the fine adjustment is given by the micro- 
meter screw of the microscope. 

This little instrument, while not well adapted for serious 
scientific work, is well suited to the wants of the amateur, on 
account of the small cost, its simplicity, and the rapidity of its 
manipulation. 

The Scomll Photo-Micrographic Camera. Fig. 31 illus- 
trates another simple form of the micrographic camera, using 
plates 4 by 5 inches. 

It consists of an ordinary bellows camera, having a cone ex- 
tension in front to give the additional length of focus neces- 
sary to give the desired amplification to the image. 

To this cone the body of the microscrope, inclined horizon- 



172 



THE PHOTOGRAPHIC NEGATIVE. 




FlG. 31. 



PHOTO-MICROGKAPHY. 173 

tally, is adapted by means of a black velvet sleeve. The 
source of illumination shown in the cut is Carbutt's multum 
in parvo lantern, with the condensers in place. Any other 
method of illumination may be substituted. 

AtwoocPs Photo-Micrographic Camera Fig. 32 illustrates 
a very convenient form of apparatus which dispenses with the 
microscope body. The coarse adjustment is effected by slid- 
ing the stage upon the solid base. The sub-stage bar is on the 
plane of the stage, and is provided with an adjustable and 
centering sub-stage to hold any accessories desired. The fine 
adjustment is in the nose piece, a brass tube with society 
screw to receive any ordinary microscopic objective. The 
focusing is done by means of a rod passing under the box to 
the back and terminating in a milled head as shown. The 
illumination is from a lamp from behind the stage. 

Amplifiers are provided to increase the size of the image 
thrown on the ground-glass screen. The whole apparatus is 
mounted upon a cherry board of convenient length. 




FIG. 32. 

The form shown in the cut allows the use of plates 4 by 5 
inches and under, but a modification has been introduced, 
with bellows extension, which increases the size of the image 
to the whole plate. Either form may be fitted with mirrors, 
stereoscopic and other attachments required by the varying 
needs of the investigator. 

Walmsley's Photo-Micrographic Camera. Figs. 33 and 
34 illustrate the very complete and ingenious apparatus, de- 
vised by Mr. W. H. Walmsley, and manufactured by the 
American Optical Company. 



174 



THE PHOTOGRAPHIC NEGATIVE. 



Fig. 33 illustrates the original and cheaper form, adapted 
only to the making of negatives up to the half-plate size. 







FIG. 33. 



Fig. 34 shows the latest form by which the original appara- 
tus is converted into a small enlarging, reducing, and copying 




FIG. 34. 



The following description of the complete camera, first pub- 
lished in the Photographic Times, is also applicable to the 



PHOTOMICROGRAPHY. 175 

cheaper form, excepting that the latter cannot be used for en- 
larging, reducing, or copying. In all other particulars the 
two boxes are identical. 

" The camera box (of mahogany) is square, carrying a Flam- 
mang single plate-holder for 4^ by 5^ plates ; usable vertically 
or horizontally, and with kits for 3^ by 4J plates. The bel- 
lows are in two sections, with a central division of mahogany, 
which carries a removable partition, to which a suitable recti- 
linear photographic lens can be attached, for enlarging, re- 
ducing, or copying. A light-tight door on one side of this 
wooden section gives ready access to the lens for inserting or 
removing diaphragms, or other necessary manipulations, whilst 
a milled head, accessible from the same opening, clamps the 
lens-bearing section firmly to the bed of the camera at any 
desired point. 

" The bellows have an extension of two feet in addition to 
the length of the box, sliding very smoothly upon Y-shaped 
ways, which, for greater convenience, are made in two sections, 
firmly attached to each other by wooden dowels and a solid 
brass screw, worked by a milled head. 

"The bellows are firmly held at any desired point of exten- 
sion by a cam, operated by s a lever conveniently placed at the 
rear of the focusing screen, which latter is hinged at the bot- 
tom, and, when not in use, lies out of the way upon the exten- 
sion bed. The screen itself is of the very finest ground-glass, 
but is used only for arranging the portion of the object to be 
photographed properly in the center of the plate, as no sur- 
face can be ground finely enough to permit the sharp focusing 
of any delicately-lined object. For this purpose, a circle or 
disc of thin microscopic covering-glass is attached with bal- 
sam to the center of the ground-glass screen, which clears 
away all the inequalities of the latter, and leaves an exquisitely 
fine surface to receive the image, which, by using an ordinary 
focusing glass, may be as sharply defined as in the eye-piece of 
the microscope. 

" The front of the camera (which is double-shifting, for the 
purpose of centering) carries a cone-shaped tube, which re- 
ceives the tube of the microscope when the latter is inclined 



1Y6 THE PHOTOGRAPHIC NEGATIVE. 

to a horizontal position, and conveys the image-bearing rays 
of the light therefrom into the body of the camera. This 
cone is removable, and in its place may be inserted kits, carry- 
ing negatives from quarter to half size for enlargement, or re- 
duction to lantern slides, as may be desired. Or a front board, 
bearing a lens, may be inserted in its place, converting the 
camera into a copying one. Indeed, a more complete instru- 
ment for all the purposes for which it was devised could 
scarcely be conceived or desired. Its design was the result of 
several years' work and experiment on the part of Mr. Walms- 
ley ; and the Scovill Manufacturing Company have carried out 
his plans in their usual masterly manner, leaving nothing to 
be desired. 

" In use, the camera is attached to a solid platform (which 
also carries the microscope and lamp) by a screw, such as is 
used with an ordinary tripod. By this means any jar or tre- 
mor, produced by a passing vehicle or other means, is com- 
municated to microscope and camera alike, preventing any 
diminution of sharpness in the negative. By this arrange- 
ment, also, the whole apparatus is so compact that, with the 
bellows closed,- the operator can easily see the image upon the 
ground glass, and at the same time reach the milled heads upon 
the microscope controlling the stage and focusing movements, 
permitting the arrangement of the subject with the greatest 
nicety. But, when the bellows are extended to their full 
length, some appliance becomes necessary to operate the fine 
adjustment of focus, whilst the eye can discern the changes 
upon the screen. This is most simply effected by Mr. Wahns- 
ley, in the employment of a fine cord passing in a groove 
around the periphery of the milled head of the fine adjust- 
ment screw, and thence through a series of hook-eyes to the 
rear of the camera bed, where it is held taut by a couple of 
leaden weights. The slightest pull upon either cord moves 
the fine adjustment screw with the utmost nicety." 

Nothing more complete or convenient than this apparatus 
can well be devised. By its use no difficulty will be experi- 
enced in securing by lamp-light photo-micrographs of all trans- 
parent objects requiring microscopical examination. Opaque 



PHOTO-MICROGRAPHY. 



m 



bodies may be photographed by illuminating them by sun- 
light reflected from a mirror. 

White's Pttoto-Micrographic Apparatus. Fig. 35 is an 




FIG. 35. 

illustration of a novel piece of apparatus, which dispenses with 
the use of the microscope, and projects a magnified image of 
the object upon a movable screen. It is the invention of Mr. 
T. Charters White, of England, who claims for it the follow- 
ing advantages : That the field of view is only limited by the 
size of plate employed ; that a great range of amplification is 
possible, and the ease with which all the adjustments are made. 

The following description of the construction and method of 
working is condensed from that given by Mr. White in the 
" British Journal Almanac, for 1887." 

A narrow, lidless box is fastened by screws to one end of 
a baseboard, two inches in thickness, and two and a half feet 
in length. The other end of the baseboard is provided with a 
groove, in which slides the wooden bar which carries the f rame 
which holds the focusing screen and sensitive plates. An or- 
dinary printing frame answers well for this purpose. An ob- 
long opening is cut in the top of the box over which a metal 
chimney is fitted. 

In the end of the box, facing the plate-holder, a square 
opening is cut and closed with a brass plate tapped with the 
standard screw gauge, thus allowing the use of any standard 



178 



THE PHOTOGRAPHIC NEGATIVE. 



objective. The movable stage support is fastened to the end 
of the box, below the brass plate, the stage being moved to 
and from the objective by a long micrometer screw. The 
front of the box is covered with a black velvet curtain. 

Two focusing screens are used ; one, for coarse adjustment, 
is made by gumming a sheet of smooth white paper on a glass 
plate. This is placed in the holder, and the object roughly ar- 
ranged and focused. The screen is then removed, and a piece 
of plain glass substituted for it, having fine lines, drawn close 
together with a writing diamond, on the surface which faces 
the object. These lines are brought into the focus of a focus- 
ing glass, placed against the back of the glass, and the stage 
moved back and forth until the details of the object are seen 
with equal sharpness. The glass is then removed and the sen- 
sitive plate substituted for it. 

This apparatus presents some novel features, and seems well 
adapted to the photographing of transparent objects. Of 
course all white light must be excluded from the room while 
the sensitive plate is in position, save that which comes 
through the objective. 

Apparatus for the Vertical Microscope. It is sometimes 
necessary, or desirable to retain the 
microscope in the vertical position. 
Such an arrangement is shown in Fig. 
36, the microscope being omitted as 
unnecessary to the clearness of the 
description. 

A A, are slotted bars supporting the 
camera body, B, with its bellows. 
There are three of these bars fastened 
firmly to a slab of hard- wood, as shown 
in the cut. The box, B, carries the 
ground glass frame, D, at its upper 
end, and is provided with a door, C, in 
one side. The object of this door is to 
admit of focusing, without mounting 
FIG. 36. a step-ladder. It must fit light-tight. 

The microscope is adapted to the cone in the base of the in- 
strument by means of a velvet sleeve. 




PHOTOMICEOGRAPHT. 179 

There are many other ways of securing photographic repre- 
sentations of the images seen in the microscope, but they are 
all modifications of the various arrangements just described, 
which are believed to be sufficiently varied to meet all possible 
needs. 

It is now proposed to enter somewhat fully into the practical 
manipulations of photo-micrography, and to give some hints 
on the choice of the microscope and objectives. 

The Microscope. Any standard form of microscope, bin- 
ocular or monocular, may be employed ; the body should be 
capable of being included to the horizontal position. The 
best form for photo-micrography is one with a broad short 
tube, because the field of illumination is then less restricted 
than when a long tube is employed. If the binocular stand 
be used, the prism must be withdrawn sufficiently to allow all 
the light to pass through the straight tube. 

The eye-piece may be used, or not, as the operator prefers. 
If it is not used, the tube must be lined witli some soft dark 
material, to prevent reflections which cause spectral spots 
called " ghosts," in the negatives. 

A mechanical stage, revolving in the optical axis of the mi- 
croscope, a sub-stage revolving in the plane of the stage, a con- 
denser, and a double or triple nose-piece will be found neces- 
sary for serious work. 

The latter is especially necessary when working with high 
powers, as an object can be quickly brought into proper posi- 
tion under a low power, and the high power substituted by re- 
volving the nose-piece. 

The Objectives. The experimenter is recommended to be- 
gin with the low powers, and to attempt higher powers only 
after he has gained complete mastery over the manipulations 
with the low powers. The one-half inch objective is a very 
good power to begin with, and the one-eighth inch is about 
as high as can be worked in photo-micrography, although much 
depends upon the skill of the operator. 

When working by artificial light with low powers, no diffi- 
culty will commonly be experienced through want of coinci- 
dence between the chemical and visual foci. With higher 



180 THE PHOTOGRAPHIC NEGATIVE. 

powers, however, it is necessary to determine the difference 
by actual experiment and allowed for it in focusing, or 
specially corrected objectives, may be employed. The photo- 
micrographic series of the Bausch Lomb Company, of Roches- 
ter, are free from this defect, besides giving a very flat field 
and fine definition. 

Source of Light. The object to be photographed may lie 
illuminated by sunlight or artificial light, the latter being pre- 
ferred on account of its greater certainty and uniformity. 
Any good microscopic lamp, burning oil, will answer well for 
photo-micrographic work, and a little practice will enable the 
operator to make such simple arrangements as may be neces- 
sary to secure the best results. The usual practice is to place 
the lamp behind the object and in line with it. Some opera- 
tors, however, prefer to illuminate the object by means of 
light reflected from a white screen placed behind the stage. 

With objectives of low powers, condensers will not be 
needed ; they must, however, be used when working with the 
higher powers, which require the most careful adjustments 
and the most scrupulous attention to minute details, and which 
are, therefore, not recommended except to the most advanced 
manipulators. 

If lamps with flat wicks are used, the flame must be placed 
at an angle to the plane of the stage, in order to avoid the 
dark spot in the center of the field. Even illumination of the 
object must be secured by the use of the diaphragms with 
which the stage should be provided. 

The author believes that the incandescent electric light is 
superior to the oil lamp, as it occupies less space, gives out no 
heat, and can be adapted to the revolving sub-stage bar. A 
very efficient light of this kind is manufactured by the Bausch 
& Lomb Company. 

Measuring the Magnification. The scientific value of a 
photo-micrographic print is greatly increased if its exact mag- 
nification is indicated. 

This is easily effected by placing upon the stage a microme- 
ter ruled in -rta and Wmi of an inch, and focussing its image upon 
the ground-glass. The exact value of each division is then 
readily determined. 



fHOTOMICROGRAPHY. " l8l 

To avoid the necessity of making this measurement each time 
an object is to be photographed, it is well to make the measure- 
ments at various points in the extension of the bellows, and to 
mark those points with their exact power of magnification. 

The Sensitive Plates. The nature of the work to be done 
will determine the kind of plate to be employed. For micro- 
metric purposes, where the greatest precision is absolutely neces- 
sary, collodion films are to be preferred to gelatine films, be- 
cause their distortion is less, being not more than 2 or 3 in 
1000 parts, while gelatine films often show an error of 1 in 100 
parts. 

For studying details, however, gelatine is vastly superior to 
collodion. The method of preparation must have been such 
as to combine extreme sensitiveness with density and strong 
contrasts. Abney states that the best plates for this class of 
work are those prepared with iodide of silver, by boiling, and 
without the use of ammonia. 

For colored objects the use of color-sensitive plates in con- 
nection with the yellow screen is strongly advised. 

Plates coated with Davanne's emulsion, given on page 102, 
are well adapted to photo-micrographic work. 

Focusing. For arranging the object in the field, and for 
the preliminary focusing the ground-glass is used. For the 
final focusing the ground-glass is replaced by a plain glass, on 
whose inner surface a series of fine parallel lines have been 
drawn with a writing diamond. The focus of a focusing-glass 
placed against the back of the glass plate is adjusted to render 
these lines sharp and distinct. The image is then brought into 
focus, and the exposure made. 

Exposure. The time of exposure varies according to the 
nature and color of the objects, the power of the objective, and 
the nature of the illumination. Mr. Walmsley gives the fol- 
lowing table for the different powers with the oil lamp : 

l-J- inch 3 to 45 seconds 

1 inch 5 to 60 seconds 

finch i to 1 minutes 

^jinch i to 3 minutes 

inch 2 to 7 minutes 

inch. 5 to 10 minutes 



182 



THE PHOTOGKAPHIC NEGATIVE. 



These figures, however, are only approximate, and the oper- 
ator must learn from experience here as in other departments 
of photography. 

Development. Any form of developer may be used, either 
the oxalate of iron or the alkaline. It is best to develop more 
for detail than for density, resorting to intensification, if neces- 
sary, to bring the negative up to the proper printing density. 




CHAPTER XX. 



MICRO-PHOTOGRAPHY. 

THE term micro-photography has been applied to the pro- 
duction, on a scale of microscopic fineness, of positives on 
glass from large negatives. These positives are subsequently 
mounted at one extremity of a Stanhope lens of great magni- 
fying powers and enclosed in many ways in tiny opera-glasses, 
keys, penholders, medallions, etc., and sold as curiosities. 

The process by which these microscopic pictures are pro- 
duced is little known and rarely practised. To the best of the 
writer's knowledge, there is but one producer of these articles 
in America, and his methods are not known to the author. 

The method here given is that employed by the best French 
producers of micro-positives, and is described in all its details 
to enable the experimenter to produce good results. 

A negative is first made, on a whole plate, of the object to be 
reproduced. This negative should not be made over-dense, 

A as it is to be used in the 

copying camera for the re- 
production of the reduced 
positives. It is not to be 
varnished, but when dry it 
is copied by any method 
known to the operator, the 
usual copying lens being re- 
placed by a brass plate carry- 
ing from twenty-five to fifty 
very small objectives, as 
_ shown in Fig. 37, which 
Fig 37 shows only a few of the 

objectives. 

This apparatus is known as the microscopic apparatus, and 
can be obtained of most large dealers in photographic goods. 




184: THE PHOTOGRAPHIC NEGATIVE. 

It will give fifty reduced positives on a 2x2 inch plate. There- 
fore, by using a 4x5 plate, and a holder adapted for making 
two exposures on one plate, one hundred impressions may be 
taken without changing the plate. 

A piece of ground-glass is placed behind the negative to be 
copied, which is accurately focused on the ground-glass at the 
back of the copying camera, using for this purpose a powerful 
focusing glass. 

The exposure is made as usual, and the plates developed in 
the customary manner. 

Since, owing to the small size of the image, it is manifestly 
impossible to watch the progress of development very closely, 
a few trial exposures must be made, developed, and fixed, that 
the operator may acquire a knowledge of the proper duration 
of the exposure, the correct strength of the developer, and the 
time of development. 

After development, the plates are fixed, washed, and dried, 
and then varnished with the following varnish : 

Benzoin 220 grains. 

Alcohol 3^ ounces. 

They are then laid face down on a clean sheet of white 
paper, and cut in parallel lines with a diamond between the 
positives, which are then separated from each other, after 
which they are mounted. 

Mounting. For this purpose a table with a sheet-iron top is 
needed. The edges of the top are turned up to form a tray, 
which is filled with fine sand, over which is spread a piece of 
thick black cloth, on which are placed the Stanhopes and the 
positives, with the side bearing the images uppermost. 

The sand is kept warm by means of a spirit or oil-lamp. A 
jar of Canada balsam, previously warmed, a pair of small brass 
pliers, and a small, flat stick of wood are also placed within 
convenient reach. 

One of the lenses is, taken with the right hand between the 
pliers, and a small quantity of the balsam applied to its flat 
end, which is then placed upon one of the small images, after 
which it is set aside to cool. When cool, the edges of the 



MICKO-PHOTOGRAPHY. 



185 



positives are rounded off on a grindstone, and then covered as 
desired. 

Wet collodion plates are best suited for this purpose, owing 
to the liability of gelatine film sustaining some damage when 
the plates are cut down. 

Although these micro-positives are chiefly used as curious 
ornaments, they have a more serious value, as affording means 
for the storage in small space of reduced copies of valuable 
originals, and for the reproduction of reduced maps, charts, 
etc , for the tourist's use. 



CHAPTER XXI. 

THE TRANSFORMATION OF NEGATIVES INTO POSITIVES. 

MANY heliographic processes require a positive for the 
production of the printing plate, as does also the production 
of enlarged negatives. Many methods have from time to time 
been proposed to obviate the necessity of taking a positive di- 
rect from the negative by contact printing or by exposure in 
the copying camera. 

Methods have also been worked out for producing positives 
direct in the camera, but all these methods have proved too 
uncertain to come into general use. 

M. E-oux, a skilful French manipulator, has worked out a 
practical process for the chemical transformation of negatives 
into positives, which should prove valuable to the process 
worker. 

All essential details of the process are given in the present 
chapter. 

No. 1. Collodion for Drawings and Engravings. 

PLAIN COLLODION. 

a. Ether 21 J^ ounces. 

Alcohol 10% ounces 

Pyroxyline 150 grains 

IODIZER. 

b. Alcohol 2% ounces 

Iodide of potassium 123 grains 

Iodide of cadmium 30 grains 

Iodine 0.7 grains 

Chloride of zinc 30 grains 

%. Collodion for Half-tones. 

PLAIN COLLODION. 

a. Same as above. 

IODIZER. 

b. Alcohol 3^4 ounces 

Iodide of cadmium 92 grains 

Iodide of ammonium 30 grains 

Iodide of zinc 30 grains 

Bromide of cadmium 22 grains 

Bromide of ammonium 22 grains 

Chloride of zinc 80 grains 



THE TRANSFORMATION OF NEGATIVES INTO POSITIVES. 187 

THE SENSITIZING BATH. 

Distilled water 85 ounces 

Nitrate of silver 1234 grains 

Acetic acid 1% ounces 

The plates are sensitized as usual, and dried moderately. 

Exposure. For negatives which are to be transformed, the 
exposure should be a trifle longer than would be necessary for 
an ordinary negative. 

Development. The following developer is recommended by 
M. Koux: 

Water 35 ounces 

Sulphate of iron 770 grains 

Acetic acid l^j ounces 

Alcohol IJg ounces 

Nitric acid 30 drops 

Ammonia 30 drops 

The best method of preparing the developer is to pulverize 
the sulphate, then to add the nitric acid, and, after stirring, 
the ammonia. The iron turns black, and stifling fumes are 
given off. As soon as these cease, the water is added, and, 
finally, the alcohol and the acetic acid. 

Negatives developed in this bath are strong and brilliant, 
with good printing density. For the present purpose, how- 
ever, it is necessary to intensify them slightly, after washing 
off the developer, with the following : 

Water 35 ounces 

Pyrogallic acid 77 grains 

Citric acid 385 grains 

Alcohol 3 drams 

to a sufficient quantity of which are added, when wanted for 
use, a few drops of the following : 

Distilled wnter 35 ounces 

Nitrate of silver 308 grains 

Acetic acid If ounces 

After intensification, the negative is washed slightly, but not 
sufficiently to remove all the free nitrate, a slight excess of 
which is useful in determining the formation of the positive 
image during the latter exposure to diffused light. 

The Transformation of the Negative. Two operations are 
necessary to transform the negative into a positive : 



188 THE PHOTOGRAPHIC NEGATIVE. 

1. Exposure of the unfixed negative to diffused light. 

2. Destruction of the negative image by dissolving the re- 
duced silver, and development of the positive image. 

1. Exposure to Diffused Light. The unfixed negative is 
placed, face up, on a piece of black cloth, and exposed to weak 
diffused light until the positive image viewed by the reflected 
light is clearly seen with a bluish-black tone on the grey 
ground of the silver of the negative image. The time neces- 
sary to produce this effect will vary from a few seconds to two 
or three minutes, according to the strength of the light. 

The color of the positive image is due to the presence of a 
small quantity of chloride of silver. 

2. Destruction of the Negative Image, and Development of 
the Positive. If re-development followed immediately upon 
the exposure to diffused light, the two images would be con- 
fused together. Hence it is first necessary to destroy the 
negative image. This is done by placing the plate, after wash- 
ing slightly, in the following solution : 

Water 25 ounces 

Bichromate of potash 460 grains 

Nitric acid lOf ounces 

The plate is immersed in this bath until the reduced silver 
of the negative image is entirely dissolved ; that is, until the 
film assumes a yellow color, except in the lines of the positive, 
which will strike a slightly reddish tint, owing to the forma- 
tion of chromate of silver. 

The plate is then washed until all traces of the acid are 
removed. 

The positive image is then developed by pouring over the 
plate sufficient of the following : 

Water 35 ounces 

Pyrogallic acid : 385 grains 

Citric acid 308 grains 

Alcohol 1 ounces. 

This solution is allowed to remain on the plate for a few 
seconds ; it is then poured off into a graduate containing a few 
drops of aceto-nitrate of silver solution, given above, and the 
mixture poured back on the plate. 



THE TRANSFORMATION OF NEGATIVES INTO POSITIVES. 189 

The positive image will now gradually develop with a 
strength proportioned to the amount of silver added to the 
developer. Reproductions of line-work require a strong and 
rapid development in order to preserve the fineness of the 
lines and perfect transparency of the ground. Reproductions 
of portraits, landscapes, and paintings require slow develop- 
ment with little silver to preserve the gradations of the half- 
tones. 

Fixing. The developed positive is fixed as usual, reproduc- 
tions of line-work, preferably in a 1 to 50 solution of cyanide 
of potassium ; those in which it is desired to preserve the half- 
tones, in the usual hypo solution. 

Intensification. The positive, if too thin, may be intensified 
either with the usual pyro and silver intensifier or with bi- 
chloride of mercury. 

Success with this method depends on the quality of the 
negative and the complete washing away, after the exposure 
to diffused light, of all the free silver. 

Reversed negatives obtained by exposure through the glass 
are, after development and drying the backs, exposed to dif- 
fused light through the glass in the plate-holder. 

Without this precaution there is danger of fog, unless all 
the iodide of silver acted upon by light was reduced by the 
developer and the intensifier. 




CHAPTEK XXII. 

OBERNETTER'S METHOD FOR THE DIRECT PRODUCTION OF NEGATIVES 
FROM NEGATIVES. 

IN the " American Annual of Photography for 1887," the 
late E. Obernetter described a practical method for the repro- 
duction of negatives in any size. 

In the issue of the "Annual for 1888," Herr F. Mueller 
gives a few valuable notes on the process. 

Both of these papers have been freely drawn upon in the 
following description, which has been written only after a 
thorough trial of the method, which has demonstrated its 
practical utility. This test of the process was the more severe, 
since the negatives thus reproduced were in many cases very 
far from possessing that high degree of technical excellence 
which is to be desired in negatives which are reproduced. 

The first requisite to complete success is faultless negatives 
of moderate density. The next is that the plates on which 
the reproduced negatives are made be thinly but evenly coated 
with an emulsion containing a comparatively small percentage 
of gelatine. 

Evenness of coating is greatly assisted by using plate or 
patent plate glass. 

The negative to be reproduced is placed in the copying 
camera, with the film side turned away from the lens, and 
focused to the desired dimensions, and the sensitive plate 
exposed for a considerably longer time than would be neces- 
sary for the production of a good positive, and developed with 
the usual oxalate of iron developer till the positive image is 
distinctly visible at the back of the plate. 

If the exposure was sufficiently prolonged, the image flashes 
up at once, the plate blackens quickly, and the development is 
completed withinjtwo minutes. 



DIRECT PRODUCTION OF NEGATIVES FORM NEGATIVES. 191 

It is important that both sides of the plate appear black, 
with only faint indications of the high lights. Unless this is 
the case the reproduced negative will fail to give the fine 
details and gradations of the original. 

When fully developed, the plate is well washed, and then 
immersed in the following chromic solution till the black 
deposit has completely changed to white : 

Water 35 ounces 

Bichromate of potassium 1540 grains 

Nitric acid (c. p.) 17)^ ounces 

For use, the solution is diluted with water in the proportion 
of 1 to 15. 

Three or four minutes' immersion in this bath will be re- 
quired to produce a thorough change of color. 

When the change is complete, the plate is thoroughly 
washed, and then made sensitive by pouring over it repeat- 
edly, and flowing, from corner to corner, the following solu- 
tion: 

Water 35 ounces 

Ammonia 6 drams 

Bromide of ammonium 308 grains 

The plate is again washed, and exposed to diffused daylight 
for a length of time varying from one to six seconds, according 
to the sensitiveness of the plate and the intensity of the light. 

After this second exposure, the plate is re-developed with 
the developer used for the first development. 

The negative will develop slowly with every appearance of 
being under-exposed. But if the second exposure was suffi- 
ciently prolonged density will gradually increase to the desired 
degree. If, however, the time of exposure was too short, the 
negative will refuse to gain in strength. 

The plate is fixed in the usual hypo solution, well washed, 
treated with dilute hydrochloric acid to clear up the shadows, 
and finally washed again to remove all traces of the acid. 



INDEX. 



Preface 3 

List of Authorities 5 

GENERAL REMARKS ON SENSITIVE 
SURFACES, ETC. 

Substances Sensitive to Light. . 7 

The Film 7 

The Dark-room and Laboratory 10 

The Drying-box 12 

Utensils 16 

Solutions 18 

Filtration 18 

Precipitation 20 

Washing Precipitates 20 

Decantation 20 

Distilling Apparatus 21 

PRELIMINARY REMARKS ON EXPOS- 
URE, DEVELOPMENT, ETC. 

Exposure 23 

Physical Conditions Governing 

the Exposure 24 

Chemical Conditions Govern- 
ing the Exposure 24 

Optical Conditions Governing 

the Exposure 25 

Development 25 

Fixing 28 

Washing 29 

Intensification 30 

Reduction 30 

Varnishing 31 

CALOTYPE PROCESS, THE. 

Fox Talbot's Process. 

Sensitizing Solutions 32 

Exposure 33 



Development 34 

Fixing 34 

Waxing 34 

Le Gray's Process. 

Waxing 35 

Iodide Bath 35 

Sensitizing.. . . . 36 

Exposure 37 

Development 37 

Pelegry's Process. 

Sensitizing 87 

Tannin Bath 37 

Exposure 38 

Development 38 

SENSITIVE SURFACES ON GLASS. 

Preparation of the Glass. 

Cleaning Bath for Old Collo- 
dion Films 39 

The Final Cleaning of the Glass 
for the Albumen and Collo- 
dion Process 39 

Albumenizing the Glass 40 

Treatment of the Glass for the 

Gelatine Process. 

Cleaning the Glass 41 

Polishing with Talc 41 

Substrata 41 

ALBUMEN PROCESS, THE. 

General Remarks 44 

Gobert's Method. 

Formulae 45 

Cleaning the Glass 45 

Coating 46 



194 



INDEX. 



Drying the Plates 46 

Fuming with Iodine 47 

Sensitizing 47 

Development 47 

Fixing 47 

Sella's Modification 48 

Bagot's Modification 48 

Couppier's Modification 49 

Whipple and Black's Albumen 
Honey Process 49 

COLLODION PROCESS, WET PLATES, 
THE. 

General Remarks 50 

Preparation of Pyroxyline 51 

The Solvents 52 

Thelodizers 72 

Plain Collodion 53 

Salted Collodion 53 

Bromized Collodion 54 

Iodized Collodion 54 

Bromo-iodized Collodion 54 

Carbutt's Collodion 45 

Vogel's Collodion 55 

Equivalent Collodion 55 

Care of the Collodion 55 

Filtering Collodion 56 

The Sensitizing Bath 56 

Management of the Bath 58 

Testing the Strength of the 

Bath 59 

Development 60 

Intensification 60 

Fixing 61 

Practical Manipulations. 

Sensitizing in the Vertical Bath 62 

Sensitizing in Trays 62 

Exposure 62 

Development 63 

Intensification 64 

Fixing 64 

Varnishing 64 

Defects .. 64 



COLLODION PROCESS, DRY PLATES, 
THE. 

General Remarks 65 

Taupinot'sCollodio-albumen Pro- 
cess. 

Manipulations 66 

Exposure and Development. . . 67 

Boivin's Process. 

Manipulations 68 

Sensitizing 69 

Development 70 

The Tannin Process. 

The Collodion 71 

The Preservative 71 

Development 71 

Sutton's Process 71 

The Gum-gallic Process 72 

COLLODION EMULSION, COLLODIO- 
BROMIDE OF SILVER. 

General Remarks 73 

The Pyroxyline 73 

The Bromides 74 

Making the Collodion and 

Emulsion 74 

Ripening the Emulsion 75 

Washing and Organifying 75 

Chardon's Method. 

The Collodion 76 

Emulsifying 76 

Re-emulsification 77 

Cooper's Process. 

The Collodion 78 

The Emulsion 78 

The Substratum 78 

The Preservative 79 



ItfDEX. 



195 



Abney's Collodio-bromide Emul- 
sion. 

Plain Collodion 79 

Bromide Solution 79 

Albumen Solution 79 

Emulsification ... 80 

Abney's Collodio-chloride Emul- 
sion. 

Emulsification 80 

The Preservative 81 

The Developer 81 

The Toning-bath 81 

Canon Beechey's Process. 

The Bromized Solution 82 

The Collodion 82 

The Sensitizer 82 

Development 83 

DevelopersforCollodion Emul- 
sion Plates 83 

Intensification 84 

Defects 84 

GELATINE PROCESS, THE 

General Remarks. .. ..86 



Preparation of Gelatine Emulsions. 

General Observations 87 

Theory of the Method 87 

Choice of Soluble Bromides. .. 88 
Tables for Emulsions, Calcula- 
tions 89 

Choice and Treatment of the 

Gelatine 91 

Proportion of the Ingredients.. 92 

Emulsifying 93 

Silvering 96 

Digesting 97 

Breaking-up and Washing. ... 97 

Draining 98 

Re-melting 98 



Formulae for Emulsions. 

Andra's 98 

Henderson's Ammonia Method 99 
Eder's Ammonio-nitrate of Sil- 
ver Method 99 

Braun's Method 100 

Scolik's Ammonio-nitrate of 

Silver Method 101 

Scolik's Modification of Hender- 
son's Cold Emulsion Method. 101 

Davanne's Method 102 

Burton's Precipitation Method. 103 

Fabre's Method 103 

Burton's Slow Emulsion 105 

Gelatine-Chloride Emulsion for 

Slides and Transparencies. . .106 
Wellington's Citro - Chloride 

Emulsion for Opals 106 

Sczekely's Process with Car- 
bonate of Silver. .. ..107 



COLLODIO-GELATINE EMULSIONS : 

Dr. Vogel's 108 

Kosarzewenski's 109 

COATING THE PLATES : 

The Levelling Shelf 110 

Button's Cooling Tank 110 

Coating Tripod 110 

Coating Board 112 

Coating Box 113 

Other Methods of Coating 113 

Quantity of Emulsion Necessary 
to Cover Various Sizes of 

Plates: 114 

Drying 114 

Packing the Plates 114 

DEVELOPMENT, FIXING, ETC.: 
Development 

General Remarks 115 

Oxalate of Iron Developer. ...116 



196 



ISfDEX, 



Alkaline Development 

General Remarks. 118 

Density 120 

The Quantity of Pyro and Alkali 
to be Used 120 

Formulae 

Cooper's 121 

Beach's 121 

The Author's 122 

Carbutt's 123 

Edward's 124 

Henderson's 124 

E. Van Sothen's 124 

Dr. Martell's 124 

Notes on the General Composition 
of Developers 

TheOxalateof Iron Developer. 124 

Alkaline Developers 124 

The Hydrochinone Developer. .125 

The Alum Bath 125 

Fixing 125 

Washing 125 

Test for Hypo 126 

Bellitzki's Hypo-Eliminator 126 

Intensifying : Formulae 

Eder's 126 

Thompson's 127 

Wallace and Bartletfs 127 

Uranium Intensifier 127 

Reduction 

Farmer's Reducer 128 

Bellitzki's Reducer 128 

Varnishing 128 

PAPER NEGATIVES, STRIPPING FILMS 
ON PAPER, CARD-BOARD, AND 
COLLODION : 

The Paper 130 

Sizing the Paper 131 



PAGE 

Coating the Paper 131 

Balagny's Method 133 

Stripping Films, Paper Support 

Chenneviere's Method 134 

Balagny's Method 135 

Fabre's Method 135 

Milson's Method 138 

Eastman's Method 138 

Stripping Films on Cardboard 

Supports 136 

Balagny's Method with Methyl- 
alcohol 136 

Coating Board 137 

Pellicular Films Without Sup- 
port 138 

Mefhods of Exposing Films on 

Paper Supports 139 

Development 140 

Drying 142 

Oiling 143 

Retouching 143 

Printing 143 

Preserving Paper Negatives . . .143 

Stripping 

Eastman's Method 143 

Chenneviere's 145 

Fabre's 145 

Failures in the Gelatino-Bro- 
mide Process 147 

METHODS OF STRIPPING FILMS FROM 
GLASS PLATES : 

Collodion Films 151 

Gelatine Films 152 

COLOR-SENSITIVE PLATES : 

General Remarks 153 

The Light-Screen 154 

Color-Sensitive Gelatine Emul- 
sion 155 

Color-Sensitive Bath Plates 155 



INDEX. 



19T 



PAGE 

Scolik's Method with Erythro- 

sine 155 

Ehrmann's Method 156 

Vogel's Method, with Azaline. .156 
Obernetter and Vogel's Ery- 

throsine Bath 156 

Schumann's Method with Cy- 

anine 157 

Obernetter's Method with Fluor- 
ide of Silver 157 

Wellington's Method 158 

Development 159 

Abuey's Method of Making Dry- 
plates Color-sensitive 159 

BLACK AND WHITE NEGATIVES. 

General Remarks 160 

The Wet Collodion Process. 

The Collodion 160 

The Silver Bath 160 

The Exposure 161 

The Developer 162 

The Intensifier 162 

Stripping 162 

The Gelatine Process. 

The Developer 162 

The Intensifier 162 

INSTANTANEOUS PHOTOGRAPHY. 

General Remarks 164 

Development. 

The Author's Method 166 

Beach's Method 167 

Touching-up the Negative 169 

PHOTO-MICROGRAPHY. 

Mercer's Photo-Micrographic 
Camera 171 

The Scovill Photo-Micrographic 
Camera... 171 



PAGE 

Atwood's Photo-Micrographic 

Camera 173 

Walmsley's Photo-Micrographic 

Camera 174 

White's Photo-Micrographic 

Apparatus. 177 

Apparatus for the Vertical Mi- 
croscope 178 

The Microscope 179 

The Objectives 179 

The Source of Light 180 

Measuring the Magnification. . .180 

The Sensitive Plates 181 

Focussing 181 

Exposure 182 

Development 182 



MICRO-PHOTOGRAPHY. 

General Description of the Pro- 
cess 183 

Mounting 184 



THE TRANSFORMATION OF NEGATIVES 
INTO POSITIVES. 

Roux's Process. 

The Collodion 186 

Development 187 

The Transformation of the Neg- 

tive 187 

Exposure to Diffused Light 188 

Distinction of the Negative Im- 
age 188 

Development of the Positive 

Image 188 

Fixing 189 

Intensification 189 

Obernetter's Method for the Di- 
rect production of Negatives 
from Negatives 190 



198 



INDEX. 



LIST OF CUTS. 



Number. PAGE 

1. Plan of Dark-room 11 

2. Ventilation of Dark-room... 12 

3. Davanne's Drying-box 13 

4. Davanne's Drying-rack 14 

5-9. Scolik's Drying-box 15 

10. Draining-rack 17 

11. Apparatus for Making Solu- 

tions 18 

12-13. Apparatus for Hot Filtration 19 

14. Washing Bottle 20 

15. Vever's Distilling Apparatus 21 

16. Collodion Filter 56 

17. Silvering Apparatus 76 

18. David and Scolik's Emulsify- 

ing Apparatus 93 

19. Davanne's Emulsifying Ap- 

paratus 94 

20. Spraying Apparatus 96 

21. Abney's Washing Apparatus 97 



22. Levelling Screw Ill 

23. Burton's Cooling Tank Ill 

24. Coating Tripod Ill 

25. Coating Board Ill 

26. Coating Box 113 

28. Apparatus for Coating Paper. 132 

29. Coating Board 137 

30. Mercer's Photo-Micrographic 

Apparatus 172 

31. Scovill's Photo-Micrographic 

Apparatus 172 

32-33. W a 1 m s 1 e y's Photo-Micro- 
graphic Apparatus 174 

34. White's Photo-Micrographic 

Apparatus 177 

35. Apparatus for the Vertical 

Microscope 178 

36. Arrangement of Lenses for 

Micro-Photography. 183 




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