LUMIERE COLOUR PROCESSES Reference is made elsewhere to the starch grain process (see " Autochrome Process " and Screen-plate Colour Photography "), but the brothers Lumiere had worked out various processes before this. In the bleach-out process they suggested (1894) the use of cyanine, quino line red and turmeric, and also a partial fixation of the results by means of metallic salts. In 1895, they exhibited prints produced from negatives taken through the usual set of red, green and violet screens, the positives being printed on bichromated films of gelatine or glue, soluble in cold water, which also contained some silver bromide or other inert insoluble matter, which increased the relief of the images. After development of the print, the silver bromide was dissolved out and the reliefs stained up and superimposed.
The process above described was introduced commercially, thin celluloid films being coated with the gelatine so that the printing could be done through the celluloid, thus obviating the necessity of double transfer or lateral inversion of the pictures.
In 1900, the brothers Lumiere exhibited a series of fine prints produced by the super position of bichromated reliefs on collodion supports, the following being an outline of the process : The screens for taking the negatives can be prepared by coating plate glass with a io per cent. solution of gelatine. When the gelatine is quite dry the plates should be immersed in the following baths, which should be at a temperature of 68° F. (20° C.), for about five minutes, then rinsed and dried. Two glasses of each colour should be cemented together with Canada balsam to form the screen : Green Bath Methylene blue N (5 % sol.) . 2 02. 411 mins. 143 ccs.
Auramine G (-5 sol.) to 2o oz. i,000 Bath Methylene blue N (5 % sol.) . . ro oz. 500 ccs.
Distilled water to . 20 1,000 Orange Bath Erythrosine J 5 % sol.) 9-1 oz. 474 ccs. Metanil yellow (sat. sol.) to 20 1,000 The dish should be well rocked whilst staining up the gelatine. The above colours are obtain able, methylene blue from Casella, auramine G and erythrosine J from the Badische Anilin and Sodafabrik, and the metanil yellow from Hepp and Oehler. The papers are prepared as follows : Plate glass should be well cleaned, dusted with French chalk, edged with rubber solution, and then coated with an enamel collodion of the following composition : Alcohol . . 9 oz. 444 ccs.
Ether . . xi ,, Pyroxyline . 105 grs. II g.
Castor oil . 24 rains. 2'5 ccs.
When the collodion is dry, the plate should be immersed in a 7 per cent. solution of gelatine at I io° F., and a sheet of baryta paper cut to the same size also placed in the gelatine. The baryta side of the paper should be brought into contact with the collodionised plate, and the two thoroughly squeezed together and then dried. When dry, the back of the paper should be varnished with Soehnee's white varnish A, diluted with an equal quantity of alcohol. After twelve hours drying the paper should be coated with the following mixture : Emulsion gelatine . . 2+ oz. 120 g.
Hard glue (Coignet) .2 k 120 Ammonium 6o Potassium citrate, neutral (25 % sol.) .384 nuns. 40 CCS.
Cochineal red . 9J grs. i g.
Alcohol . . . 4 oz. 200 ccs.
Water . . . 20 1,000 Soak the gelatine and glue in the water and dissolve at F., allow to cool down to 95° F., and then add the other ingredients, and finally the alcohol in small quantities. Filter the mixture and coat the paper, whilst on the glass, with the mixture, allowing about 90 nuns. or 2 ccs. for every too sq. in. or too qcm. The paper is then thoroughly dried exactly as in the carbon process, stripped from the glass, and exposed beneath the three nega tives, an actinometer being used to determine the duration of insolation. After exposure the print should be squeegeed into contact with a sheet of glass which has been previously collodionised with the above-mentioned collodion, and then coated with a -75 per cent, solution of rubber in benzole. The coated glass and the exposed print should be immersed in a dish of cold water, squeegeed into contact and placed under pressure for five minutes, then soaked in cold water for two hours so as to allow of complete expansion of the gelatine and paper. Development should be effected in water at 100° F., and the print allowed to soak for about half an hour, when the paper can be readily detached and the print developed as in the carbon process, and finally washed in cold water and immersed in alcohol for five minutes and dried. The relief prints thus obtained are dyed respectively red, yellow and blue, the necessary baths being as follows : Red Bath Erythrosine J (3 % sol.) f oz. 25 ccs.
Water to . . . 20 1,000 Yellow Bath Chrysophenine G . 32 grs. 3.3 g.
Water . . .i6 oz. 833 ccs.
Dissolve at 16o° P. and add Alcohol . . . 31 oz. 167 ccs.
Blue Bath Diamine blue P, pure (3 % sol.) . . 432 mins. 45 ccs.
Hard glue (15 % sol.) . if oz. 63 Water to . . . 20 1,000 The relief prints should be left in these baths for about twelve hours, then rinsed, and the red and blue impressions immersed in a 5 per cent, solution of cupric sulphate and then rinsed and dried. The yellow print must not be treated to the copper bath. It is possible to superimpose temporarily the images whilst on the glass supports and see if they are sufficiently stained ; corrections can then be made by deeper staining, or washing out some of the dye. The dyed impressions should be coated with a 1.5 per cent. solution of rubber in benzole, then collodionised with a i per cent. collodion, and the yellow print transferred to paper by means of a warm 15 per cent. solution of gelatine, the paper being stripped when dry and the red and blue impressions superimposed on this also.
In a later process MM. Lumihre suggested the making of the blue impression by conversion of the image of a bromide print by bleaching with potassium ferricyanide followed by ferric chloride, then coating this blue print with collodion containing tetrazotolylsulphite or tetrazoanisidinesulphite of soda and the chlor hydrate of 8-naphthylamine-ether. Exposing under the red printing negative and the action of light produces the red image. Another coating with collodion containing diazo-ortho toluidine sodium sulphite with metamidophenol or resorcin gave the yellow image. MM. Luniihre have also paid considerable attention to Lipp mann's process