PROCESS A method of producing prints in pigment or ink applied with a brush. As contact printing is an essential part of the process it follows that an enlarged negative must be made before such a print can be obtained of a subject originally taken on a small plate. It was tc obviate this that the bromoil process was evolved. The steps preceding the actual pig menting are few and simple. Special papa made for the purpose may be obtained, but a variety that is perfectly satisfactory is that supplied for the final support in the double transfer carbon process. In any case it is simply a paper coated with gelatine. This has to be sensitised. It should then be stored in a calcium tube, but it is preferable to use it the next day if possible, so that it is best only to sensitise such quantities as are wanted for immediate use.
A lo per cent. solution of potassium bichromate is an effective sensitiser. It should be applied by means of a Blanchard brush (see Equal quantities of potassium bichromate solution and of methylated spirit are placed in a clean porcelain dish, which is tilted so that the solution lies at one end. One ounce of each is more than sufficient for half a dozen 12 in. by 10 in. sheets. A piece of the paper is laid face upwards on a pad of folded newspaper, and the brush is charged with solution and drawn across the paper first in one direction and then at right angles to it. Only enough solution should be taken to cover the surface. The stroking action in two directions is continued until the streaks on the surface practically disappear as the gelatine absorbs the sensitiser. The sheet
is then pinned up, by one corner only, to dry, and the other sheets treated similarly. The sensitising should be done by a yellow light that would be fairly safe for bromide work, and the drying completed in the dark-room. When dry, the sheets may be placed in a box or tube, and should be protected from actinic light with the same care as in the case of platinotype paper. In fact, the paper resembles platinotype in its sensitiveness to light, and in the character of the image that prints out under the negative. Printing is continued until all that is required in the finished print is visible.
The prints are now washed in several changes of water. The yellow bichromate stain first disappears, but washing should be continued until there is practically no trace of colour even in the darkest shadows. In cold weather the temperature of the later washing waters should be raised to 6o° or 65° P. or 18° C.). The paper finally shows the subject as a gelatine relief, the high lights appearing considerably raised. Pigmenting may be proceeded with at once, or the prints may be dried and stored away for future treatment. In the latter case it is only necessary to re-soak the prints until the relief is again evident. For the method of finishing the print, see the outline of procedure given under the heading " Pigmenting."