WORKING UP PRINTS A term usually applied to working up photo graphs by means of crayon or water colour. The air-brush may be employed effectively for soft, shaded or clouded backgrounds, or for any mass of shading that is required to be evenly or delicately graded or perfectly flat.
The prints most suited for treatment are those on matt-surfaced bromide or gaslight papers ; the colour dries with a matt or smooth surface and becomes disagreeably evident on any paper with a semi-glossy surface, and still more prominent on a glossy print. The materials required are water colours and brushes of good quality, small saucers or china palettes for mixing the colours, and prepared ox-gall. A little of the last-named is mixed with the colour if the surface of the print is so repellent that the colour will not take readily. For black prints, the best pigments are lamp black, blue-black, ivory black, and zinc white or Chinese white. Ivory black is required only for warm black prints. For all excepting the deepest tones a little white should be mixed with the black to destroy its transparency and give body or solidity. All the pigments should be purchased in the moist form in tubes. For brown and
purple-toned prints other pigments will be necessary, the most suitable being either Van dyke brown or burnt umber, which may be combined with ivory black for various shades of brown ; and neutral tint and either scarlet madder or alizarin crimson for mixing different shades of purple. Crimson lake and carmine should be avoided, as they are very fugitive.
The aim should be to strengthen or modify in depth, and to follow the character of existing work as closely as possible. The added work should improve the photograph as a photograph. For this reason, the outlining of details should not be attempted.
In working up photographs for process repro duction, the colours employed must be such that their photographic value is the same as their visual effect. For working in black, process white, Blanc d'argent, and process black should be employed. Blanc d'argent is not permanent, but it possesses great body and mixes with black for producing greys. Chinese white reproduces as a distinct grey.