Successfully to prepare drawings for photographic reproduction it is essential that some knowledge should be possessed of the fundamental principles of {95} photography, as well as an acquaintance with the capabilities of the particular process of production which is to be employed. Thus, the material upon which the drawing is to be made should be of such a character as will yield a strong and well-defined contrast to the lines of the drawing; while the pigment employed for the drawing should be as black as can be procured. White Bristol board of fine surface, and the best India ink meet these conditions. A blue-black does not form a desirable drawing medium, but the introduction of red or orange into the composition should serve to intensify the photographic image. To draw upon a dark orange-colored paper with a pale blue-gray ink would be simply to disregard all photographic principles, for the photographic value of the paper and of the ink would be nearly equal, and the drawing would consequently be lost.
Uniformity of color in the drawing is also desirable, and the artist should resist the natural tendency to express distance and to produce his effects by diminishing the intensity of color in parts of his picture. From a drawing uniform in color a satisfactory negative is obtained; but, in the other case, the photographer must estimate an average duration of exposure, and will rarely escape the dilemma of some portions being overexposed while others are comparatively undeveloped. This theory receives illustration from the fact that very good subdued effects can be obtained from well-executed pencil drawings, where this uniformity of color is preserved. A longer exposure may be required, but every part of the picture will be equally developed.
To return to the matter of the paper used, color is not the only important consideration. If the surface of the paper is irregular and coarse in texture, such as painters in water-color delight in, good results must not be expected. A negative, taken in the ordinary way from a drawing made on such material, would inevitably reproduce all the inequalities of the texture of the paper, to the manifest injury of the more delicate parts of the drawing. In reproductions from old prints or printed books, the conditions and character of the paper present some of the greatest difficulties with which the photographer has to contend. The ridges in the surface of the paper cast shadows which are too faithfully reproduced in the negative. The employment of a diffusive rather than a direct light is the usual remedy, but the best way of dealing with the difficulty is that employed in the studio of the Autotype Company. The original is laid upon the floor under a strong light, and the camera set at an angle of forty-five degrees.
Mr. Alfred Dawson informs me that he inclines to the opinion, founded upon {96} his extensive experience and untiring experiment, that it is desirable to get rid of the surface of the paper altogether, by covering it with a substance similar to an enamel.
In conclusion, the conditions required in the successful preparation of drawings for photographic reproduction, may be thus briefly summarized: That a sufficient photographic contrast should exist between the pigment employed and the material upon which the drawing is made; that a paper should be selected which is smooth and without water-mark, and white; that the drawing material may be pencil or ink, in which blue is not a component.—JAMES S. HODGSON.
FADING OUT THE PHOTOGRAPH.
For newspaper line work excellent results may be obtained by drawing over a photograph, and then fading out the photographic parts not wanted. There are several methods, but the following is the most simple and the easiest to manage: Make a weak solution of cyanide of potassium and add a flake or two of iodine. When the drawing is made with water-proof ink and on a photograph printed upon bromo-gelatine paper the above solution flowed over it will at once cause such portions of the image as have not been drawn upon with the ink, to fade away and leave nothing but a fine ink sketch against a perfectly white background.—ROBERTS & FELLOWS.
THE REVERSAL OF DRAWINGS (NEGATIVE PRINTING).
This very simple and very safe method is to be recommended especially for advertisements in papers and for titles of books, and can be made both by aid of photography (by a transparency) and without it, in the following manner:
Make a copy, on copy-paper, of the drawing to be reversed, using an ink of gum, glycerine, and aniline, and transfer it carefully, without using too much water, when loosening. Dry the plate, and pour over it a solution of 1 part of asphaltum, 1 part Venetian turpentine, in 18 parts benzole; then allow to dry upon a plate. Place the plate into a weak soda solution, and develop with a fine pad of cotton, till the drawing stands clear. Ordinarily I employ the following method: A plate prepared for transfer is uniformly cleansed with gallic acid and then coated with gum, as in the case of blackening a transferred drawing, while both solutions are left to dry spontaneously. This done, the coating of gum and gallic acid is thoroughly washed off, and the plate is carefully dried and gently warmed. The transferred drawing must be made on {97} paper with an easily soluble layer composed as follows: dissolve 100 grammes of wheat starch—i. e., starch made of wheat—in 400 c.cm. of rain-water; raise 1 litre of water to boiling and dissolve therein: 50 grammes of common salt, 75 grammes of glycerine, 50 grammes of gelatine, and 25 grammes of molasses; when these are well dissolved and taken up, add slowly the wheat-starch, stirring continually; then allow to boil a short time so that we may dissolve it without an excess of water after the ordinary transfer of the picture. When this has been done, we wash it again with a soft brush and water, dry, dust twice, and burn in thoroughly with asphaltum. Place the plate in a very weak bath of nitric acid (10 cubic centimetres of acid to 1 litre of water), and rock it lightly for about two minutes until the zinc changes color. Then wash, dry, and warm.