Chapter I: II III (6)

When the coated paper is dry it may be printed and toned just the same as any other printing-out paper, with any toning bath, and fixed in hyposulphite of soda as usual. Toning may be carried to a rich blue black, or if not carried too far will remain a beautiful sepia color. After well washing and drying, it will be observed that the surface corresponds with that of a carbon print; if the paper has been of a somewhat absorbent character, the surface will be entirely mat, and will give an excellent tooth for coloring or finishing in sepia, black and white, etc.

«How to Sensitize Photographic Printing Papers.»—I.—The older form of paper is one in which the chemicals are held by albumen. Silver is said to combine with this, forming an albuminate. Pictures printed on this would be too sharp in their contrasts, and consequently “hard”; this is avoided by introducing silver chloride.

To prepare this form of paper, beat 15 ounces of fresh egg albumen with 5 ounces of distilled water, dissolve in it 300 grains of ammonium chloride, set aside for a time, and decant or filter. Suitable paper is coated with this solution by floating, and then dried. The paper is “sensitized” by floating it on a solution of silver nitrate in distilled water, about 80 grains to the ounce, with a drop of acetic acid. The paper is dried as before, and is then ready for printing. The sensitizing must, of course, be done in the dark room.

The reaction between the ammonium chloride present in the albumen coating produces a certain quantity of silver chloride, the purpose of which is shown above. Of course, variations in the proportions of this ingredient will give different degrees of softness to the picture.

II.—The bromide and chloride papers which are now popular consist of the ordinary photographic paper sensitized by means of a thin coating of bromide or chloride emulsion. In “Photographic Printing Methods,” by the Rev. W. H. Burbank, the following method is given for bromide paper:

A.—Gelatin (soft) 42 1/2 grains
Bromide of potassium 26 grains
Distilled water 1 ounce

B.—Nitrate of silver 33 1/3 grains
Distilled water 1 ounce

Dissolve the bromide first, then add the gelatin and dissolve by gentle heat (95° to 100° F.). Bring the silver solution to the same temperature, and add in a small stream to the gelatin solution, stirring vigorously, of course in non-actinic light. Keep the mixed emulsion at a temperature of 105° F. for half an hour, or according to the degree of sensitiveness required, previously adding 1 drop of nitric acid to every 5 ounces of the emulsion. Allow it to set, squeeze through working canvas, and wash 2 hours in running water. In his own practice he manages the washing easily enough by breaking the emulsion up into an earthen jar filled with cold water, and placed in the dark room sink. A tall lamp chimney standing in the jar immediately under the tap conducts fresh water to the bottom of the jar, and keeps the finely divided emulsion in constant motion; a piece of muslin, laid over the top of the jar to prevent any of the emulsion running out, completes this simple, inexpensive, but efficient washing apparatus.

Next melt the emulsion and add one-tenth of the whole volume of glycerine and alcohol; the first to prevent troublesome cockling of the paper as it dries, the second to prevent air bubbles and hasten drying. Then filter.

With the emulsion the paper may be coated just as it comes from the stock dealer, plain, or, better still, given a substratum of insoluble gelatin, made as follows:

Gelatin 1 3/5 grains Water 1 ounce

Dissolve and filter; then add 11 drops of a 1 in 50 filtered chrome alum solution. The paper is to be floated for half a minute on this solution, avoiding air bubbles, and then hung up to dry in a room free from dust. The purpose of this substratum is to secure additional brilliancy in the finished prints by keeping the emulsion isolated from the surface of the paper. The paper should now be cut to the size desired.

We do not know of these processes having been applied to postal cards, but unless there is some substance in the sizing of the card which would interfere, there is no reason why it should not be. Of course, however, a novice will not get the results by using it that an experienced hand would.

«Ferro-Prussiate Paper.»—The following aniline process of preparing sensitive paper is employed by the Prussian and Hessian railway administrations. The {540} ordinary paper on reels is used for the purpose, and sensitized as follows:

Two hundred and fifty parts, by weight, of powdered potassium bichromate are dissolved in water; the solution should be completely saturated; 10 parts of concentrated sulphuric acid, 10 parts of alcohol (962), and 30 parts of phosphoric acid, are added successively, and the whole stirred together. The solution is sponged over the paper. It is not necessary to have the room absolutely dark, or to work by a red light, still the light should be obscured. The drying of the paper, in the same place, takes about 10 minutes, after which the tracing to be reproduced and the paper are placed in a frame, as usual, and exposed to daylight. On a sunny day, an exposure of 35 seconds is enough; in cloudy weather, 60 to 70 seconds; on a very dark day, as much as 5 minutes.

After exposure, the paper is fixed by suspending it for 20 minutes upon a bar in a closed wooden box, on the bottom of which are laid some sheets of blotting paper, sprinkled with 40 drops of benzine and 20 of crude aniline oil. The vapors given off will develop the design. Several impressions may be taken at the same time.

For fixing, crude aniline oil is to be used (anilinum purum), not refined (purissimum), for the reason that the former alone contains the substances necessary for the operation. The reproduced design is placed in water for a few minutes, and hung up to dry.

«Pigment Paper for Immediate Use.»—Pigment paper is usually sensitized in the bichromate solution on the evening before it is desired for use. If it is not then used it will spoil. By proceeding as follows the paper may be used within a quarter of an hour after treating it in the bichromate bath. Make a solution of

Ammonium bichromate 75 grains Water 3 1/2 fluidounces Sodium carbonate 15 grains

Mix 0.35 ounces of this solution with 0.7 ounces alcohol, and with a broad brush apply to surface of the pigment paper, as evenly as possible. Dry this paper as quickly as possible in a pasteboard box of suitable size, 15 minutes being usually long enough for the purpose. It may then be used at once.

«Photographing on Silk.»—China silk is thoroughly and carefully washed to free it from dressing, and then immersed in the following solution:

Sodium chloride 4 parts Arrowroot 4 parts Acetic acid 15 parts Distilled water 100 parts

Dissolve the arrowroot in the water by warming gently, then add the remaining ingredients. Dissolve 4 parts of tannin in 100 parts of distilled water and mix the solutions. Let the silk remain in the bath for 3 minutes, then hang it carefully on a cord stretched across the room to dry. The sensitizing mixture is as follows:

Silver nitrate 90 parts Distilled water 750 parts Nitric acid 1 part

Dissolve. On the surface of this solution the silk is to be floated for 1 minute, then hung up till superficially dry, then pinned out carefully on a flat board until completely dry. This must, of course, be done in the dark room. Print, wash, and tone in the usual manner.

«TONING BATHS FOR PAPER.»

The chief complaints made against separate baths are (1) the possibility of double tones, and (2) that the prints sometimes turn yellow and remain so. Such obstacles may easily be removed by exercising a little care. Double tones may be prevented by soaking the prints in a 10 per cent solution of common salt before the preliminary washing, and by not touching the films with the fingers; and the second objection could not be raised provided fresh solution were used, with no excess of sulphocyanide, if this be the bath adopted.

A very satisfactory solution may be made as follows:

Sodium phosphate 20 grains Gold chloride 1 1/2 grains Distilled (or boiled) water 10 ounces

This tones very quickly and evenly, and the print will be, when fixed, exactly the color it is when removed from the bath. Good chocolate tints may be obtained, turning to purple gray on prolonged immersion.

Next to this, as regards ease of manipulation, the tungstate bath may be placed, the following being a good formula:

Sodium tungstate 40 grains Gold chloride 2 grains Water 12 ounces

The prints should be toned a little further than required, as they change color, though only slightly, in the hypo. {541}

Provided that ordinary care be exercised, the sulphocyanide bath cannot well be improved upon. The formulas given by the various makers for their respective papers are all satisfactory, and differ very little. One that always acts well is

Ammonium sulphocyanide 28 grains Distilled water 16 ounces Gold chloride 2 1/2 grains

For those who care to try the various baths, and to compare their results, here is a table showing the quantities of different agents that may be used with sufficient water to make up 10 ounces:

Gold chloride, 1 gr. to 1 oz. water 12 dr. 16 dr. 16 dr. 11 dr. 11 dr. 14 dr. Borax 60 gr. Sod. bicarbonate 10 gr. Sod. carbonate 20 gr. Sod. phosphate 20 gr. Sod. tungstate 40 gr. Amm. sulphocyanide 17.5 gr.

We may take it that any of these substances reduce gold trichloride, AuCl_〈3〉 to AuCl; this AuCl apparently acts as an electrolyte, from which gold is deposited on the silver of the image, and at the same time a small quantity of silver combines with the chlorine of the gold chloride thus:

AuCl + Ag = AgCl + Au

When toning has been completed, the prints are washed and placed in the fixing bath, when the sodium thiosulphate present dissolves any silver chloride that has not been affected by light.

Besides the well-known, every-day tones we see, which never outstep the narrow range between chocolate brown and purple, a practically infinite variety of color, from chalk red to black, may be obtained by a little careful study of toning baths instead of regarding them as mere unalterable machines. Most charming tints are produced with platinum baths, a good formula being

Strong nitric acid 5 drops Water 4 ounces Chloro-platinite of potassium 1 grain

The final tone of a print cannot be judged from its appearance in the bath, but some idea of it may be got by holding it up to the light and looking through it. A short immersion gives various reds, while prolonged toning gives soft grays.

Results very similar to platinotype may be obtained with the following combined gold and platinum bath:

_A._—Sodium acetate 1 drachm
Water 4 ounces
Gold chloride 1 grain

_B._—Chloro-platinite of potassium 1 grain
Water 4 ounces

Mix _A_ and _B_ and neutralize with nitric acid. (The solution will be neutral when it just ceases to turn red litmus paper blue.)

Another toning agent is stannous chloride. Two or three grains of tin foil are dissolved in strong hydrochloric acid with the aid of heat. The whole is then made up to about 4 ounces with water.

«Toning Baths for Silver Bromide Paper.»—The picture, which has been exposed at a distance of 1 1/2 feet for about 8 to 10 seconds, is developed in the customary manner and fixed in an acid fixing bath composed of

Distilled water 1,000 cubic centimeters Hyposulphite of soda 100 grams Sodium sulphite 20 grams Sulphuric acid 4 to 5 grams

First dissolve the sodium sulphite, then add the sulphuric acid, and finally the hyposulphite, and dissolve.

Blue tints are obtained by laying the picture in a bath composed as follows:

_A._—Uranium nitrate 2 grams
Water 200 cubic centimeters

_B._—Red prussiate
of potash 2 grams
Water 200 cubic centimeters

_C._—Ammonia-iron-alum 10 grams
Water 100 cubic centimeters
Pure hydrochloric acid 15 cubic centimeters

Immediately before the toning, mix

Solution _A_ 200 cubic centimeters Glacial acetic acid 20 cubic centimeters Solution _B_ 200 cubic centimeters Solution _C_ 30 to 40 cubic centimeters

Brown tints. Use the following solutions: {542}

_A._—Uranium nitrate 12 grams
Water 1,000 cubic centimeters

_B._—Red prussiate of potash 9 grams
Water 1,000 cubic centimeters

And mix immediately before use

Solution _A_ 100 cubic centimeters Solution _B_ 100 cubic centimeters Glacial acetic acid 10 cubic centimeters

Pictures toned in this bath are then laid into the following solution:

Water 1,500 cubic centimeters Pure hydrochloric acid 5 cubic centimeters Citric acid 20 grams

«To Turn Blueprints Brown.»—A piece of caustic soda about the size of a bean is dissolved in 5 ounces of water and the blueprint immersed in it, on which it will take on an orange-yellow color. When the blue has entirely left the print it should be washed thoroughly and immersed in a bath composed of 8 ounces of water in which has been dissolved a heaping teaspoonful of tannic acid. The prints in this bath will assume a brown color that may be carried to almost any tone, after which they must again be thoroughly washed and allowed to dry.

«COMBINED TONING AND FIXING BATHS.»

The combined toning and fixing bath consists essentially of five parts—(1) water, the solvent; (2) a soluble salt of gold, such as gold chloride; (3) the fixing agent, sodium thiosulphate; (4) a compound which will readily combine with “nascent” sulphur—i. e., sulphur as it is liberated—this is usually a soluble lead salt, such as the acetate or nitrate, and (5) an auxiliary, such as a sulphocyanide.

The simplest bath was recommended by Dr. John Nicol, and is as follows:

Sodium thiosulphate 3 ounces Distilled water 16 ounces

When dissolved, add

Gold chloride 4 grains Distilled water 4 fluidrachms

A bath which contains lead is due to Dr. Vogel, whose name alone is sufficient to warrant confidence in the formula:

Sodium thiosulphate 7 ounces Ammonium sulphocyanide 1 ounce Lead acetate 67 grains Alum 1 ounce Gold chloride 12 grains Distilled water 35 fluidounces

A bath which contains no lead is one which has produced excellent results and is due to the experimental research of Dr. Liesegang. It is as follows:

Ammonium sulphocyanide 1/4 ounce Sodium chloride 1 ounce Alum 1/2 ounce Sodium thiosulphate 4 ounces Distilled water 24 fluidounces

Allow this solution to stand for 24 hours, during which time the precipitated sulphur sinks to the bottom of the vessel; decant or filter, and add

Gold chloride 8 grains Distilled water 1 fluidounce

It is curious that, with the two baths last described, the addition to them of some old, exhausted solution makes them work all the better.

«ENLARGEMENTS.»

───────────────────────────────────────────────────────────────────────────────
TIMES OF ENLARGEMENT AND REDUCTION
───────+────────+────────+────────+────────+────────+────────+────────+────────
Focus │ │ │ │ │ │ │ │
of │ 1 inch │2 inches│3 inches│4 inches│5 inches│6 inches│7 inches│8 inches
Lens. │ │ │ │ │ │ │ │
In. │ │ │ │ │ │ │ │
───────+────────+────────+────────+────────+────────+────────+────────+────────
2 │ 4 │ 6 │ 8 │ 10 │ 12 │ 14 │ 16 │ 18
│ 4 │ 3 │ 2 2/3 │ 2 1/2 │ 2 2/5 │ 2 1/3 │ 2 2/7 │ 2 1/4
───────+────────+────────+────────+────────+────────+────────+────────+────────
2 1/2 │ 5 │ 7 1/2 │ 10 │ 12 1/2 │ 15 │ 17 1/2 │ 20 │ 22 1/2
│ 5 │ 3 3/4 │ 3 1/3 │ 3 1/8 │ 3 │ 2 9/10│ 2 6/7 │ 2 3/16
───────+────────+────────+────────+────────+────────+────────+────────+────────
3 │ 6 │ 9 │ 12 │ 15 │ 18 │ 21 │ 24 │ 27
│ 6 │ 4 1/2 │ 4 │ 3 3/4 │ 3 3/5 │ 3 1/2 │ 3 3/7 │ 3 3/8
───────+────────+────────+────────+────────+────────+────────+────────+────────
3 1/2 │ 7 │ 10 1/2 │ 14 │ 17 1/2 │ 21 │ 24 1/2 │ 28 │ 31 1/2
│ 7 │ 5 1/4 │ 4 2/3 │ 4 3/4 │ 4 1/5 │ 4 1/12│ 4 │ 3 9/10
───────+────────+────────+────────+────────+────────+────────+────────+────────
4 │ 8 │ 12 │ 16 │ 20 │ 24 │ 28 │ 32 │ 36
│ 8 │ 6 │ 5 1/3 │ 5 │ 4 4/5 │ 4 2/3 │ 4 4/7 │ 4 1/2
───────+────────+────────+────────+────────+────────+────────+────────+────────
4 1/2 │ 9 │ 13 1/2 │ 18 │ 22 1/2 │ 27 │ 31 1/2 │ 36 │ 40 1/2
│ 9 │ 6 3/4 │ 6 │ 5 3/5 │ 5 2/5 │ 5 1/4 │ 5 1/7 │ 5 1/16
───────+────────+────────+────────+────────+────────+────────+────────+────────
5 │ 10 │ 15 │ 20 │ 25 │ 30 │ 35 │ 40 │ 45
│ 10 │ 7 1/2 │ 6 2/3 │ 6 1/4 │ 6 │ 5 5/6 │ 5 5/7 │ 5 5/8
───────+────────+────────+────────+────────+────────+────────+────────+────────
5 1/2 │ 11 │ 16 1/2 │ 22 │ 27 1/2 │ 33 │ 38 1/2 │ 44 │ 49 1/2
│ 11 │ 8 1/4 │ 7 1/3 │ 6 4/5 │ 6 1/2 │ 6 5/12│ 6 2/7 │ 6 3/16
───────+────────+────────+────────+────────+────────+────────+────────+────────
6 │ 12 │ 18 │ 24 │ 30 │ 36 │ 42 │ 48 │ 54
│ 12 │ 9 │ 8 │ 7 1/2 │ 7 1/5 │ 7 │ 6 6/7 │ 6 3/4
───────+────────+────────+────────+────────+────────+────────+────────+────────
7 │ 14 │ 21 │ 28 │ 35 │ 42 │ 49 │ 56 │ 63
│ 14 │ 10 1/2 │ 9 1/3 │ 8 3/4 │ 8 2/5 │ 8 1/6 │ 8 │ 7 7/8
───────+────────+────────+────────+────────+────────+────────+────────+────────
8 │ 16 │ 24 │ 32 │ 40 │ 48 │ 56 │ 64 │ 72
│ 16 │ 12 │ 10 2/3 │ 10 │ 9 3/5 │ 9 1/3 │ 9 1/7 │ 9
───────+────────+────────+────────+────────+────────+────────+────────+────────
9 │ 18 │ 27 │ 36 │ 45 │ 54 │ 63 │ 72 │ 81
│ 18 │ 13 1/2 │ 12 │ 11 1/4 │ 10 4/5 │ 10 1/2 │ 10 2/7 │ 10 1/8
───────+────────+────────+────────+────────+────────+────────+────────+────────

{543}

The object of this table is to enable any manipulator who is about to enlarge (or reduce) a copy any given number of times to do so without troublesome calculation. It is assumed that the photographer knows exactly what the focus of his lens is, and that he is able to measure accurately from its optical center. The use of the table will be seen from the following illustration: A photographer has a _carte_ to enlarge to four times its size, and the lens he intends employing is one of 6 inches equivalent focus. He must therefore look for 4 on the upper horizontal line and for 6 in the first vertical column, and carry his eye to where these two join, which will be at 30–7 1/2. The greater of these is the distance the sensitive plate must be from the center of the lens; and the lesser, the distance of the picture to be copied. To reduce a picture any given number of times, the same method must be followed; but in this case the greater number will represent the distance between the lens and the picture to be copied, the latter that between the lens and the sensitive plate. This explanation will be sufficient for every case of enlargement or reduction.

If the focus of the lens be 12 inches, as this number is not in the column of focal lengths, look out for 6 in this column and multiply by 2, and so on with any other numbers.

To make a good enlargement five points should be kept constantly in view, viz.:

1. Most careful treatment of the original negative.

2. Making a diapositive complete in all its parts.

3. Scrupulous consideration of the size of the enlargement.

4. Correct exposure during the process of enlargement.

5. The most minute attention to the details of development, including the chemical treatment of the enlarged negative.

The original negative should not be too dense, nor, on the contrary, should it be too thin. If necessary, it should be washed off, or strengthened, as the case may be. Too strong a negative is usually weakened with ammonium persulphate, or the fixing hypo solution is quite sufficient. All spots, points, etc., should be retouched with the pencil and carmine.

The diapositive should be produced by contact in the copying apparatus. A border of black paper should be used to prevent the entry of light from the side.

The correct period of exposure depends upon the thickness of the negative, the source of the light, its distance, etc. Here there is no rule, experience alone must teach.

For developing one should use not too strong a developer. The metol-soda developer is well suited to this work, as it gives especially soft lights and half tones. Avoid too short a development. When the finger laid behind the thickest spot, and held toward the light, can no longer be detected, the negative is dense enough.

The denser negatives should be exposed longer, and the development should be quick, while with thin, light negatives the reverse is true; the exposure should be briefer and the development long, using a strong developer, and if necessary with an addition of potassium bromide.

The silver chloro-bromide diapositive plates, found in the shops, are totally unsuited for enlargements, as they give overdone, hard pictures.

To produce good artistic results in enlarging, the diapositive should be kept soft, even somewhat too thin. It should undergo, also, a thorough retouching. All improvements are easily carried out on the smaller positive or negative pictures. Later on, after the same have been enlarged, corrections are much more difficult and troublesome.

«VARNISHES:»

«Cold Varnish.»—

I.—Pyroxylin 10 grains
Amyl alcohol 1 ounce
Amyl acetate 1 ounce

Allow to stand, shaking frequently till dissolved. Label: The negative should be thoroughly dried before this solution is applied, which may be done either by flowing it over the solution or with a flat brush. The negative should be placed in a warm place for at least 12 hours to thoroughly dry.

II.—Japanese gold size 1 part
Benzol 1 part

Label: In applying this varnish great care should be taken not to use it near a light or open fire. It can be flowed over or brushed on the negative.

«Black Varnish.»—

Brunswick black 1 1/2 ounces Benzol 1 ounce

Label: The varnish should be applied with a brush, care being taken not to use it near a light or open fire. {544}

«Dead Black Varnish.»—

Borax 30 grains Shellac 60 grains Glycerine 30 minims Water 2 ounces

Boil till dissolved, filter, and add aniline black, 120 grains.

Label: Apply the solution with a brush, and repeat when dry if necessary.

«Ordinary Negative Varnish.»—

Gum sandarac 1 ounce Orange shellac 1/2 ounce Castor oil 90 minims Methyl alcohol 1 pint

Allow to stand with occasional agitation till dissolved, and then filter. Label: The negative should be heated before a fire till it can be comfortably borne on the back of the hand, and then the varnish flowed over, any excess being drained off, and the negative should then be again placed near the fire to dry.

«Water Varnish.»—It is not only in connection with its application to a wet collodion film that water varnish forms a valuable addition to the stock of chemicals in all-round photography; it is almost invaluable in the case of gelatin as with wet collodion films. In the case of gelatin negatives the water varnish is applied in the shape of a wash directly after the negatives have been washed to free their films from all traces of hypo, or in other words, at that stage when the usual drying operation would begin. After the varnish has been applied the films are dried in the usual manner, and its application will soon convince anyone that has experienced the difficulty of retouching by reason of the want of a tooth in the film to make a lead-pencil bite, as the saying goes, that were this the only benefit accruing from its application it is well worthy of being employed.

The use of water varnish, however, does away with the necessity of employing collodion as an additional protection to a negative, and is, perhaps, the best known remedy against damage from silver staining that experienced workers are acquainted with. As a varnish it is not costly, neither is it difficult to make in reasonably small quantities, while its application is simplicity itself. The following formula is an excellent sample of water varnish:

Place in a clean, enameled pan 1 pint of water, into which insert 4 ounces of shellac in thin flakes, and place the vessel on a fire or gas stove until the water is raised to 212° F. When this temperature is reached a few drops of hot, saturated solution of borax is dropped into the boiling pan containing the shellac and water, taking care to stir vigorously with a long strip of glass until the shellac is all dissolved. Too much borax should not be added, only just sufficient to cause the shellac to dissolve, and it is better to stop short, if anything, before all the flakes dissolve out than to add too much borax. The solution is then filtered carefully and, when cold, the water varnish is ready for use.

«FADED PHOTOGRAPHS AND THEIR TREATMENT:»

Restoring Faded Photographs.—I.—As a precaution against a disaster first copy the old print in the same size. Soak the faded photograph for several hours in clean water and, after separating print from mount, immerse the former in nitric acid, highly dilute (1 per cent), for a few minutes. Then the print is kept in a mercury intensifier (mercuric chloride, 1/2 ounce; common salt, 1/2 ounce; hot water, 16 ounces, used cold), until bleached as much as possible. After half an hour’s rinsing, a very weak ammonia solution will restore the photograph, with increased vigor, the upper tones being much improved, though the shadows will show some tendency to clog. The net result will be a decided improvement in appearance; but, at this stage, any similarly restored photographs should be recopied if their importance warrants it, as mercury intensifier results are not permanent. It may be suggested that merely rephotographing and printing in platinotype will probably answer.

II.—Carefully remove the picture from its mount, and put it in a solution of the following composition:

By weight Hydrochloric acid 2 parts Sodium chloride 8 parts Potassium bichromate 8 parts Distilled water 250 parts

The fluid bleaches the picture, but photographs that have been toned with gold do not quite vanish. Rinse with plenty of water, and develop again with very dilute alkaline developer.

«MOUNTANTS:»

See also Adhesives.

I.—If buckling of the mount is to be cured, the prints must be mounted in a dry state, and the film of mountant borne by the print must be just sufficient to attach it firmly to the mount and no more. The great virtue of the method {545} here described consists of the marvelously thin film of tenacious mountant applied to the print in its dry condition, shrinkage by this means being entirely obviated. A drawing board with a perfectly smooth surface and of fair dimensions, an ivory or bone burnisher attached to a short handle, with some common glue, are the principal requisites. Take, say, a quarter of a pound of the glue broken into small pieces and cover it with water in a clean gallipot, large enough to allow for the subsequent swelling of the glue. Place on one side until the glue has become thoroughly permeated by the water, then pour off the excess and dissolve the glue in the water it has absorbed, by placing the gallipot in a vessel of hot water. The solution tested with a piece of blue litmus paper will show a distinctly acid reaction, which must be carefully neutralized by adding some solution of carbonate of soda. The amount of water absorbed by the glue will probably be too little to give it the best working consistency, and, if this is the case, sufficient should be added to make it about the thickness of ordinary molasses. Careful filtration through a cambric handkerchief, and the addition of about 10 grains of thymol, completes the preparation of the mounting solution. As glue deteriorates by frequent and prolonged heating, it is preferable to make up a stock solution, from which sufficient for the work in hand can be taken in the form of jelly, melted, and used up at once.

The finished prints, dried and trimmed to the required size, are placed on the boards they are to occupy when mounted, and, as it is impossible to remove a print for readjustment once it is laid down for final mounting, the wisest course is to indicate by faint pencil marks on the mount the exact position the print is to occupy; then it may be laid down accurately and without any indecision. A small gas or oil stove is required on the mounting table to keep the glue liquid, but maintaining the solution in a constant state of ebullition throughout the operation is unnecessary and harmful to the glue; the flame should be regulated so that the mountant is kept just at the melting point. Place the drawing board beside the gas stove and with a house-painter’s brush of good quality and size spread the glue over an area considerably exceeding the dimensions of the print to be mounted. A thin coating of glue evenly applied to the board is the end to aim at, to accomplish which the brush should be worked in horizontal strokes, crossing these with others at right angles. Have at hand a small pile of paper cut into pieces somewhat larger than the print to be mounted (old newspaper answers admirably for these pieces), lay one down on the glued patch and press it well into contact by passing the closed hand across it in all directions. Raise one corner of the paper, and slowly but firmly strip it from the board. Repeat the operations of gluing the board (in the same place) and stripping the newspaper 2 or 3 times, when a beautifully even cushion of glue will remain on the board.

Mounting the prints is the next step. The cushion of glue obtained on the board has to be coated with glue for, say, every second print, but the amount applied must be as small as possible. After applying the glue the print is laid down upon it, a square of the waste newspaper laid over the print, which has then to be rubbed well into contact with the glue. Raise a corner of the print with the point of a penknife and strip it from the board, as in the case of the newspaper. Care must be taken when handling the print in its glued condition to keep the fingers well beyond the edges of the print, in order that no glue may be abstracted from the edges. Lay the print quickly down upon its mount; with a clean, soft linen duster smooth it everywhere into contact, place upon it a square of photographic drying board, and with the bone burnisher go over it in all directions, using considerable pressure. The finished result is a mounted print that shows no signs of buckling, and which adheres to the mount with perfect tenacity.

II.—Gelatin 2 parts
Water 4 parts
Alcohol 8 parts

The alcohol is added slowly as soon as the gelatin is well dissolved in the water, and the vessel turned continually to obtain a homogeneous mixture. The solution must be kept hot during the operation on a water bath, and should be applied quickly, as it soon dries; the print must be placed exactly the first time, as it adheres at once. The solution keeps for a long time in well-corked bottles.

«TRANSPARENT PHOTOGRAPHS:»

I.—The following mixture may be employed at 176° F., to render photographs transparent. It consists of 4 parts paraffine and 1 part linseed oil. After immersion the photographs are at once {546} dried between blotting paper. For fastening these photographs to glass, glue or gelatin solution alone cannot be employed. This is possible only when one-fourth of its weight of sugar has been added to the glue before dissolving. The glasses for applying the photographs must be perfect, because the slightest defects are visible afterwards.

II.—If on albumen paper, soak the print overnight in a mixture of 8 ounces of castor oil and 1 ounce of Canada balsam. Plain paper requires a much shorter time. When the print is thoroughly soaked, take it from the oil, drain well, and lay it on the glass face downward, and squeeze till all is driven out and the print adheres. If a curved glass is used, prepare a squeegee with edge parallel with the curvature of the glass. It will take several hours before the print is dry enough to apply color to it.

«THE GUM - BICHROMATE PHOTO-PRINTING PROCESS.»

Gum bichromate is not a universal printing method. It is not suited for all subjects or for all negatives, but where there is simplicity and breadth in sizes of 8 1/2 x 6 1/2 and upward, direct or enlarged prints by it have a charm altogether their own, and afford an opportunity for individuality greater than any other method.

While almost any kind of paper will do, there are certain qualities that the beginner at least should endeavor to secure. It should be tough enough to stand the necessary handling, which is considerably more than in either the printing-out or developing methods. It must not be so hard or smooth as to make coating difficult, nor so porous as to absorb or let the coating sink in too much; but a few trials will show just what surface is best. Till that experience is acquired it may be said that most of Whatman’s or Michallet’s drawing papers, to be had at any artist’s materials store, will be found all that can be desired; or, failing these, the sizing of almost any good paper will make it almost as suitable.

For sizing, a weak solution of gelatin is generally employed, but arrowroot is better; half an ounce to a pint of water. It should be beaten into a cream with a little of the water, the rest added, and brought to the boil. When cold it may be applied with a sponge or tuft of cotton, going several times, first in one direction and then in the other, and it saves a little future trouble to pencil mark the non-sized side.

The quality of the gum is of less importance than is generally supposed, so long as it is the genuine gum arabic, and in round, clean “tears.” To make the solution select an 8-ounce, wide-mouthed bottle, of the tall rather than the squat variety, and place in it 6 ounces of water. Two ounces of the gum are then tied loosely in a piece of thin muslin and suspended in the bottle so as to be about two-thirds covered by the water. Solution begins at once, as may be seen by the heavier liquid descending, and if kept at the ordinary temperature of the room may not be complete for 24 or even 48 hours; but the keeping qualities of the solution will be greater than if the time had been shortened by heat. When all that will has been dissolved, there will still be a quantity of gelatinous matter in the muslin, but on no account must it be squeezed out, as the semi-soluble matter thus added to the solution would be injurious. With the addition of a few drops of carbolic acid and a good cork the gum solution will keep for months.

The selection of the pigments is not such a serious matter as some of the writers would lead us to believe. Tube water colors are convenient and save the trouble of grinding, but the cheap colors in powder take a better grip and give richer images. The best prints are made with mixtures of common lampblack, red ocher, sienna, umber, and Vandyke brown, the only objection to their employment being the necessity of rather carefully grinding. This may be done with a stiffish spatula and a sheet of finely ground glass, the powder mixed with a little gum solution and rubbed with the spatula till smooth, but better still is a glass paper weight in the shape of a cone with a base of about 1 1/2 inches in diameter, bought in the stationer’s for 25 cents.

The sensitizer is a 10 per cent solution of potassium bichromate, and whatever be the pigment or whatever the method of preparing the coating, it may be useful to keep in mind that the right strength or proportion, or at least a strength of coating that answers very well, is equal parts of that and the gum solution.

In preparing the coating measure the gum solution in a cup from a toy tea set that holds exactly 1 ounce, it being easier to get it all out of this than out of a conical graduate. From 20 to 30 grains of the color or mixture of colors in powder is placed on the slab—the ground surface of an “opal” answers well—and enough of the gum added to moisten it, and work the paper weight “muller,” aided by the {547} spatula, as long as any grittiness remains, or till it is perfectly smooth, adding more and more gum till it is like a thick cream. It is then transferred to a squat teacup and 1 ounce of the bichromate solution gradually added, working it in with one of the brushes to perfect homogeneity. Of course, it will be understood that this mixture should be used all at once, or rather only as much as is to be used at once should be made, as notwithstanding what has been said to the contrary, it will not keep. After each operation, both or all of the brushes should be thoroughly cleaned before putting them away.

Not the least important are the brushes; one about 2 inches wide and soft for laying on the coating, the other, unless for small work, twice that breadth and of what is known as “badger” or a good imitation thereof, for softening.

The paper can be bought in sheets of about 17 x 22 inches. Cut these in two, coating pieces of about 17 x 11. The sheet is fastened to a drawing board by drawing pins, one at each corner. The coating brush—of camel’s hair, but it is said that hog’s is better—is filled with the creamy mixture, which has been transferred to a saucer as more convenient, and with even strokes, first one way and then the other, drawn all over the paper. It is easier to do than to describe, but all three joints, wrist, elbow, and shoulder take part, and unless the surface of the paper is too smooth, there is really no difficulty to speak of.

By the time the whole surface has been covered the paper will have expanded to an extent that makes it necessary to remove three of the pins and tighten it, and then comes the most important and the only really difficult part of the work, the softening. The softener is held exactly as one holds the pen in writing, and the motion confined altogether to the wrist, bringing only the points of the hair in contact with the coating, more like stippling than painting.

If much of the coating has been laid on, and too much is less of an evil than too little, the softener will soon have taken up so much as to require washing. This is done at the tap, drying on a soft cloth, and repeat the operation, the strokes or touches gradually becoming lighter and lighter, till the surface is as smooth and free from markings as if it had been floated.

Just how thick the coating should be is most easily learned by experience, but as, unlike ordinary carbon, development begins from the exposed surface, it must be as deep; that is, as dark on the paper as the deepest shadow on the intended print, and it should not be deeper.

While it is true that the bichromate colloid is not sensitive while wet, the coating is best done in subdued light, indeed, generally at night. Hang the sheets to dry in the dark room.

Exposure should be made with some form of actino-meter.

Development may be conducted in various ways, and is modified according to the extent of the exposure. Float the exposed sheet on water at the ordinary temperature from the tap. The exposure should admit of complete, or nearly complete, development in that position in from 5 to 10 minutes; although it should not generally be allowed to go so far. By turning up a corner from time to time one may see how it goes, and at the suitable stage depending on what one really wants to do, the otherwise plain outcome of the negative is modified, gently withdrawn from the water, and pinned up to dry.

The modifying operation may be done at once, where the exposure has been long enough to admit it, but generally, and especially when it has been such as to admit of the best result, the image is too soft, too easily washed off to make it safe. But after having been dried and again moistened by immersion in water, the desired modification may be made with safety.

The moistened print is now placed on a sheet of glass, the lower end of which rests on the bottom of the developing tray, and supported by the left hand at a suitable angle; or, better still, in some other way so as to leave both hands free. In this position, and with water at various temperatures, camel’s-hair brushes of various sizes, and a rubber syringe, it is possible to do practically anything.

«TABLES AND SCALES:»

«Comparative Exposures of Various Subjects.»—

Seconds Open panorama, with fields and trees 1 Snow, ice, marine views 1 Panorama, with houses, etc. 2 Banks of rivers 3 Groups and portraits in open air (diffused light) 6 Underneath open trees 6 Groups under cover 10 Beneath dense trees 10 Ravines, excavations 10 Portraits in light interiors 10 Portraits taken 4 feet from a window, indoors, diffused light 30

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«TABLE SHOWING DISPLACEMENT ON GROUND GLASS OF OBJECTS IN MOTION»

By Henry L. Tolman

_From the Photographic Times_

Lens 6-inch Equivalent Focus, Ground Glass at Principal Focus of Lens

──────+─────────────+─────────────────+─────────+──────────
Miles │ Feet │ Distance on │ Same │ Same
per │ per Second. │ Ground Glass, │ with │ with
Hour. │ │ in inches, with │ Object │ Object
│ │ Object 30 Feet │ 60 Feet │ 120 Feet
│ │ away. │ away. │ away.
──────+─────────────+─────────────────+─────────+──────────
│ │ │ │
1 │ 1 1/2 │ .29 │ .15 │ .073
2 │ 3 │ .59 │ .29 │ .147
3 │ 4 1/2 │ .88 │ .41 │ .220
4 │ 6 │ 1.17 │ .59 │ .293
5 │ 7 1/2 │ 1.47 │ .73 │ .367
6 │ 9 │ 1.76 │ .88 │ .440
7 │ 10 1/2 │ 2.05 │ 1.03 │ .513
8 │ 12 │ 2.35 │ 1.17 │ .587
9 │ 13 │ 2.64 │ 1.32 │ .660
10 │ 14 1/2 │ 2.93 │ 1.47 │ .733
11 │ 16 │ 3.23 │ 1.61 │ .807
12 │ 17 1/2 │ 3.52 │ 1.76 │ .880
13 │ 19 │ 3.81 │ 1.91 │ .953
14 │ 20 1/2 │ 4.11 │ 2.05 │ 1.027
15 │ 22 │ 4.40 │ 2.20 │ 1.100
20 │ 29 │ 5.87 │ 2.93 │ 1.467
25 │ 37 │ 7.33 │ 3.67 │ 1.833
30 │ 44 │ 8.80 │ 4.40 │ 2.200
35 │ 51 │ 10.27 │ 5.13 │ 2.567
40 │ 59 │ 11.73 │ 5.97 │ 2.933
──────+─────────────+─────────────────+─────────+──────────

W. D. Kilbey, in the _American Annual of Photography_, gives still another table for the exposure that should be given to objects in motion.

According to his method the table is made out for a distance from the camera 100 times that of the focus of the lens; that is, for a 6-inch focus lens at 50 feet, a 7-inch at 58 feet, an 8-inch at 67 feet, a 9-inch at 75 feet, or a 12-inch at 100 feet.

Toward At Right
the Angles to
Camera. the Camera.

Man walking slowly, street scenes 1/15 sec. 1/45 sec. Cattle grazing 1/15 sec. 1/45 sec. Boating 1/20 sec. 1/60 sec. Man walking, children playing, etc. 1/40 sec. 1/120 sec. Pony and trap, trotting 1/100 sec. 1/300 sec. Cycling, ordinary 1/100 sec. 1/300 sec. Man running a race and jumping 1/150 sec. 1/450 sec. Cycle racing 1/200 sec. 1/600 sec. Horses galloping 1/200 sec. 1/600 sec.

If the object is twice the distance, the length of allowable exposure is doubled, and vice versa.

«To Reduce Photographs.»—When one wishes to copy a drawing or photograph he is usually at a loss to know how high the plate will be when any particular base is selected. A plan which has the merit of being simple and reliable has been in use in engravers’ offices for years.

Here are the details:

Turn the drawing face down and rule a diagonal line from the left bottom to the right top corner. Then measure from the left, on the bottom line, the width required. Rule a vertical line from that point until it meets the diagonal. Rule from that point to the left, and the resulting figure will have the exact proportions of the reduction. If the depth wanted is known, and the width is required, the former should be measured on the left upright line, carried to the diagonal, and thence to the lower horizon. The accompanying diagram explains the matter simply.

«COLOR PHOTOGRAPHY:»

«A Three-Color Process.»—Prepare 7 solutions, 4 of which are used for color screens, the remaining 3 serving as dyes for the plates.

A.—Screen Solutions.—

Blue violet.

By weight Methylene blue 5 parts Tetraethyldiamidooxytriphenyl carbinol 2 parts

Or:

By weight Methyl violet 5 parts Alcohol 200 parts Water, distilled 300 parts

Green.

By weight Malachite green 10 parts Alcohol 200 parts Water, distilled 300 parts

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Yellow.

By weight Acridin yellow N. O. 10 parts Alcohol 200 parts Water, distilled 300 parts

Red.

By weight Congo rubin 10 parts Alcohol 200 parts Water, distilled 300 parts

B.—Dyes (Stock Solutions).—

By weight
I.—Acridin yellow or acridin orange, N. O. 1 part
Alcohol 100 parts
Water, distilled 400 parts

By weight
II.—Congo rubin 1 part
Alcohol 100 parts
Water, distilled 400 parts

By weight
III.—Tetraethyldiamidooxytriphenyl carbinol 1 part
Alcohol 100 parts
Water, distilled 400 parts

The screen solutions, after being filtered through paper filters into clean dishes, are utilized to bathe 6 clean glass plates previously coated with 2 per cent raw collodion; we require 1 plate for blue violet, 2 plates for red, 2 plates for yellow, and 1 plate for green, which in order to obtain the screens are combined in the following way: Yellow and red plate, yellow and green plate. For special purposes the other red plate may be combined with the blue violet. Another method of preparing the screens is to add the saturated solutions drop by drop to a mixture of Canada balsam and 2 per cent castor oil and cement the glasses together. Those who consider the screens by the first method too transparent, coat the glass plates with a mixture of 2 to 3 per cent raw collodion and 1 per cent color solution. Others prefer gelatin screens, using

By weight Hard gelatin (Nelson’s) 8 parts Water 100 parts Absolute alcohol 10 parts Pigment 1 part

This is poured over the carefully leveled and heated plate after having been filtered through flannel.

The collodion screens are cemented together by moistening the edges with Canada balsam (containing castor oil) and pressing the plates together in a printing frame, sometimes also binding the edges with strips of Japanese paper.

On the evening before the day of work, good dry plates of about 18° to 24° W. are dyed in the following solution:

By weight Stock solution, No. 1 16 parts Distilled water 100 parts Alcohol 5 parts Nitrate of silver (1.500) 50 parts Ammonia 1–2 parts

This bath sensitizes almost uninterruptedly to line A. The total sensitiveness is high, and the plate develops cleanly and fine. Blue sensitiveness is very much reduced, and the blue screen is used for exposure. As far as the author’s recollection goes, the plate for the yellow color has never been color-sensitized, many operators using the commercial Vogel-Obernetter eosin silver plates made by Perutz, of Munich; others again only use ordinary dry plates with a blue-violet screen. This is, however, a decided mistake, necessitating an immense amount of retouching, as otherwise it produces a green shade on differently colored objects of the print.

For the red color plate the dry plate is dyed in

By weight Stock solution, No. 2 10 parts Distilled water 100 parts Nitrate of silver (1.500) 100 parts Ammonia 2 parts

The resulting absorption band is closed until E, reaching from violet to red (over C). This red pigment was examined by Eder, who obtained very good results, using ammonia in the solution.

The corresponding screen is a combination of malachite green with acridin yellow or acridin orange N. 0.

For the blue color plate the dye is made up as follows:

By weight Stock solution, No. 3 0.5–1 part Distilled water 100 parts Nitrate of silver (1.500) 100 parts Ammonia 1–2 parts

This dye yields a strong band, commencing at B, reaching to C 3/4 D; since the orange screen used herewith necessitates a long exposure, the action seems to extend into the infra-red (beyond A).

As a rule, cyanine is used instead of the tetraethyldiamidooxytriphenyl carbinol {550} (HCl salt), but the former is apt to produce fogged plates. Methyl violet or crystal violet has also been suggested.

Exposures should be made in direct sunlight or with artificial pure white light (acetylene); electric light is too variable.

The most suitable methods of reproduction are half-tone, and the prototype methods; also Turati’s Isotypie. The greatest difficulty in 3-color printing nowadays is presented by the want of accurate printing. We must use the proper paper and pure fast colors; the inking rollers should be smooth, not too soft, and free from pores or weals. The blocks must be firmly fixed typehigh, otherwise they take color irregularly. A good printing machine is, of course, most essential.

To supplement the above working directions: After having kept the plates for 2 or 3 minutes (constantly moving the dish) in the dyes, they are removed into a dish containing filtered alcohol, which extracts the superfluous pigment. Plates thus treated dry much more rapidly, develop cleaner, and show no fogging.

Most of the above dyes may be obtained from the “Berliner Actiengesellschaft für Anilinfabrikation,” the acridin only from the “Farbwerk Mühlheim, a/Main, vorm. A. Leonhard & Company.”

«Solution for Preparing Color Sensitive Plates.»—H. Vollenbruch maintains that plates sensitized with erythrosin silver citrate are not only more sensitive to color impressions, but also have better keeping qualities than ordinary erythrosin bathed plates.

For depression of the over-active blue rays he recommends the addition of picric acid to the coloring solution. The picric acid erythrosin silver citrate ammonia solution is prepared as follows:

_Solution I_

Citrate of potassa 1 gram Distilled water 10 cubic centimeters

_Solution II_

Silver nitrate 1 gram Distilled water 10 cubic centimeters

Both solutions are mixed and a white precipitate is formed which is allowed to subside. The clear supernatant liquid is poured off carefully, precipitate washed with water, allowed again to subside, and the wash water again decanted. This process is repeated two or three times. Finally a large bulk of water (20 cubic centimeters) is added to the precipitate and well shaken; 5 cubic centimeters of this is reserved, the remainder is treated to ammonia, drop by drop, until the precipitate is redissolved. Now add the 5 cubic centimeters of reserved solution and shake the whole until every particle is dissolved. Then make up the solution to 50 cubic centimeters and filter; this forms Solution III.

_Solution IV_

Distilled water 300 cubic centimeters Pure erythrosin 1 grain

Under lamplight the 50 cubic centimeters of Solution III are poured slowly with repeated shaking in Solution IV, by which the originally beautiful red is converted into a dirty turbid bluish red somewhat viscid fluid; add—

_Solution V_

Picric acid 4 grams Absolute alcohol 30 cubic centimeters

Shake well, and add to the whole 33 cubic centimeters ammonia (specific gravity, 0.91), wherewith the beautiful red color is restored.

After the filtration call this Solution VI. This solution keeps well. The slight deposit formed is redissolved on shaking.

The plates are sensitized as follows: The plate to be sensitized is first laid in a tray of distilled water for 2 or 3 minutes, then bathed in a mixture of 1 cubic centimeter ammonia for 1 minute and finally for 2 minutes in a bath composed of the following:

Color Solution VI 10 cubic centimeters Distilled water 300 cubic centimeters

The plate is well drained and dried in a perfectly dark room. These plates keep well for several months.

«MICROPHOTOGRAPHS.»