For the dyeing use may be made, among other colours, of the following baths (three-colour dyes, A. von Hiibl, 1912) or mixtures of them Rh.odamine, S. . .2-2 gr.
(o-25.grm.
Solid bluish green Bayer - 9 gr gin.) Naphthol yellow . . 44 gr.
Alcohol 90° . 2 OZ. 2 02. 2 02.
(100 C.C.) lice C.C.) (ice c.c.) Glacial acetic acid - - 50 min. 50 min.
(5 c.c.) (5 c.c.) Saturated chrome alum solution . . - I oz.
(5c c.c.) Water, to make . OZ. 20 02. 20 OZ.
(1,000 C.C.) (r,000 c.c.) (I,000 c.c.) After the dyeing, which, at the dilutions given, may take several hours, the excess of dye is removed by a brief rinse.
When there is occasion to superimpose several component images, the final effect may be judged by packing the glasses bearing these images in two wooden blocks, placing the whole well above an opal glass or white paper. The necessary corrections, general or local, may then be made by fresh dyeing or by decolorizing with water rendered slightly alkaline with ammonia. Each of the pictures is then mordanted, as previously described, rinsed, and put aside to dry.
The dried images are coated with a 1-5 per cent solution of rubber, then with a i per cent solution of collodion. To superimpose the pic
tures, use is made of a temporary support, pre pared as indicated below, cemented to one of the pictures, with a 15 per cent solution of strong glue. After complete drying, the paper is removed, bringing the print with it. This latter is applied on the next image by means of an alum-gelatine solution, made as follows— Hard gelatine - . 1,000 gr. (520 grin.) Glycerine . . . i oz. (50 c.c.) Chrome alum, io% solution i dr. (so c.c.) Water, to make . • 20 OZ. (1,000 c.c.) Registration being controlled through the glass, the squeegee is used to remove any excess of gelatine, and the whole is left to dry. The paper, carrying with it two pictures, is then removed, and the process repeated for the succeeding image. This method may be used to transfer the whole series of the pictures to glass, or to keep it as a film. In both cases the paper will be detached from the block of images by immersion in warm water, which dissolves the glue but not the hard gelatine.