Part 100

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_