CARBON PRINTING.
It is very doubtful whether any process so completely fills the require ments of the artistic photographer as does the carbon process. Its long scale, reproducing perfectly every gradation of the original negative, its permanence, its great variety of color, its wonderful transparency in the deepest shadows, and its adaptability to any surface, all combine to render it the most perfect of photographic printing methods. Sometimes, indeed, its very perfection is a barrier to its use. If we have to print from a flat, thin negative in carbon, we shall certainly obtain a flat, thin result, but for a negative with a very full scale of gradation, especially large and enlarged negatives, it is the process par excellence. Year by year it gains steadily in favor, and our exhibitions have greatly improved in general appearance by the variety of color it has given to their walls. In this short article it is my intention to give a brief outline of the process, embodying the salient points, which, if followed by the tyro, should ensure his success, but at the same time I would recommend him, after he has mastered the initial difficulties, to read some text book and make himself thoroughly acquainted with all the details and higher branches of the subject. Carbon Printing, as we know it to-day, is based on the fact that a mixture of gelatine with a chromic salt is gradually hardened and rendered insoluble on exposure to light. If, therefore, paper is coated with such a mixture of sensitized gelatine, containing any permanent pigment—Carbon was originally used, hence the name of the process—and if this paper is placed underneath a negative and exposed to actinic light, we shall have a positive image formed, consisting of soluble and insoluble gelatine; insoluble in exact proportion as the light has reached the surface of the pigmented compound. Develop ment consists in washing away with hot water those portions of gelatine which the light has not affected sufficiently to render insoluble. Now, without going more minutely into details at this stage, and perhaps frighten ing the beginner with imaginary difficulties, I would assure him that the process only needs care, cleanliness and exactness at every stage in order to ensure success.
To those taking up Carbon Printing for the first time, a start should be made with the " Single Transfer Process ". This is the simplest form and has some advantages over the " double transfer " because less manipulation is required, and, moreover, it is easier to produce prints on rough drawing papers by its means. The only objection to it is that everything becomes reversed; what was on tbe right hand side of the original is now on the left hand side of the print, but this is of little moment for purely artist;c work. Of course, where enlarged negatives are required, specially for Carbon Printing, they are usually made reversed, and such will give a true result after printing by the single transfer process. Eastman films may be printed through the film itself, i. e., with the celluloid side in contact with the " tissue "—as the pigmented printing paper is technically called—and the resulting print will render the picture in its correct aspect.
Carbon Tissue, Thermometer.
Black Varnish or Lantern Slide Binders, Alum.
Single Transfer Paper, a little larger than Actinometer.
the negative. Blotting Paper.
A Flat Squeegee—not roller. 3 Dishes (2 for cold water and one for Squeegeeing Board. Alum Solution).
Bichrornate of Potash. f Developing Tank or largre basin to hold Camel's Hair Mop Brush. hot water.
Carbon Tissue is the name given to the paper coated with pigmented gelatine and may be purchased from the photographic stock dealers in almost any desired color. When insensitive, it will keep in a dry place almost indefinitely. Should the beginner be able to purchase it ready sensi tized, he is advised to do so, because tissue sensitized in the making is usually manufactured from softer gelatine and consequently development is easier and quicker. Sensitizing is, however, a very simple operation, and if done at night the tissue is ready for use when dry the following morning and will keep in good condition for about a fortnight, although, when preserved in a calcium tin, such as is used for platinotype paper, its longevity is very greatly prolonged, The sensitizing solution is made as follows: Potassium bichromate, - - - - - - - f oz.