Photo-engraving, Photo-etching, and Photo-lithography in Line and Half-tone;, by W. T. Wilkinson, A Project Gutenberg eBook

To develop photo-litho. transfers on paper

there are two methods. The first and oldest is, after exposure, to coat a smooth litho. stone with a thin layer of transfer ink, by means of a leather roller, then to lay the exposed print face down upon this inked stone, and pull it through the press. Of course, this must be done in a dark room, or by gas or oil light, as daylight would spoil the transfer.

Now the inked and exposed transfer is placed in water at 80° F., and allowed to remain for three or four minutes, when it is taken from the water and placed upon a plate of glass, and the superfluous ink is removed by means of a sponge dipped in the hot water. If the negative has been sufficiently opaque, and the exposure right, the image will quickly develop, the lines retaining the ink, while that upon the whites will come away.

Hot water is used where the coating is of gelatine only; if gum arabic, or albumen has been used, then, after inking up on the stone, the transfer must be developed in cold water, and cotton-wool used to remove the ink from the whites, rubbing very carefully with very little pressure.

Paper prepared with a thick coat of gelatine may be developed in another way; after removing it from the printing-frame, the transfer is inked up on the stone, then placed in a dish of cold water and left there for five or ten minutes; then removed and placed upon a thick glass slab, the end tucked under so that when placed on the bench the slab will press the paper and keep it in position. Now, with a sheet of clean blotting-paper, remove the water from the transfer, using pressure with the hands from the end tucked under the slab; then, with a glue roller, roll from the tucked under end until the image is developed. Instead of inking the transfer up when dry, the transfer may be placed in the cold water directly it is taken from the printing-frame, and allowed to remain for ten or fifteen minutes, during which time the image will swell, by the whites absorbing water. Now place upon the glass slab (one end being tucked under), and remove the superfluous water first with a {141} sponge, then with a damp cloth; now dip a sponge in transfer ink thinned to the consistency of cream by turpentine, and dab all over the damp transfer, then allow it to stand until the turpentine has evaporated. Next take the glue roller and roll the transfer until the whites are clear; only roll one way—i.e., from the end tucked under the slab.

The transfers being developed, they are rinsed with clean water, and hung up to dry in a current of cool air. If dried at too high a temperature, the transfers will be inferior, and difficult to handle.

Instead of using a slab of glass, and tucking the end of the transfer underneath, a proper developing-board may be used as follows: A is a clamped board 18 inches by 12 inches, by 1 inch thick; B is another 4 inches by 12 inches; these are hinged together at C, the hinges being let into the boards underneath. Now, if the transfer be laid upon the board A, the end placed in the aperture C, then the pressure of the roller will cause the piece B to clamp the paper quite tight.

A few little differences in manipulation are required by the various transfer papers found on sale in the market. For this reason I add the instructions given by Prof. Husnik for his transfer paper.

Making the paper sensitive.

—Pour the solution in a shallow glass or porcelain dish (such as photographers use), take hold of the paper on two opposite ends, dip one end (prepared side upward) in the solution, and draw the paper through so that the whole surface is covered evenly with the solution; drain off and hang it up for drying in a dark room. Pins may be used for this purpose. Never reverse the paper in hanging it up. Wet only as much of the paper as you intend using at every one occasion. In hot summer weather the so prepared paper must be used within a few hours. In cold and damp weather it keeps good for three days. After the paper has passed through the bath the prepared side of it must not be brought in contact with anything whatever, as the least touch will create a spot in the picture. For pouring back the solution into the bottle use a glass funnel. It is very advisable to run the sensitive {142} paper on a polished stone or metal plate through a lithograph press to give a smooth surface.

The development

of the picture can begin after the mentioned time and is to be accomplished with a fine, solid, and very soft sponge, rubbing in circle-form with it over all parts of the picture until all the ink is washed out of the lights, the lines becoming clear and distinct and the shade properly open. The water must be changed several times, passing always with the sponge delicately over all parts of the picture to remove all uncleanliness from it. But never go over the picture with a dry sponge. After washing the picture clean it is laid between damp printing paper and slightly pressed with the hands to remove the superfluous water. Was the exposure of the picture too long it will be very difficult, yea, impossible to develop it. Too short an exposure will lose the fine lines. The proper time of exposure will easily be learned.

For very fine reproductions

the paper should be dried and inked in the following manner:

Take a pane of glass, coat it with a fatty substance, as tallow or wax dissolved in benzine; wipe the glass clean, so as to leave only a trace of fat on; lay the paper in the solution about one minute, drain off and then lay the paper face down on the glass, removing all air bubbles by rubbing over the back with a rubber straight edge, or better, a squeegee. When dry, the paper will leave the glass easily and will have a glass-like surface.

The inking.

—Take common lithographic transfer ink, mix with it one-fourth part of the photo-lithographic ink and coat a smooth stone with an even tint, taking care not to make it too thick (a smooth lithograph or composition roller will answer). Lay the printed picture face down and run it through the press with a good pressure; the picture will be covered with an even tint, showing the picture through it.

The development is the same as above described. This later method gives excellent results.

Transferring.

—When all the water is removed from the picture, and while damp, lay it on the stone and make the transfer with the same care as other transfers are made, starting with a very light pressure; and if the paper sticks to the stone, increase the pressure. It is advisable to wash the stone with pure turpentine, and dry it before transferring.