THE PHOTOGRAPHY OF COLOUR 365 



plate, and any three-colour process can be worked from these 

 records. 



The subtractive method, in which the three coloured prints 

 are superposed, and each subtracts its quota from the light 

 that passes through, was foreshadowed by Du Hauron and by 

 Charles Cros. The production of transparencies in this way 

 engaged the attention of Mr. Ives, and in 1893 he showed me 

 a very fine example, perhaps 8 in. by 6 in. or larger. But it is 

 to Mr. Sanger-Shepherd and his firm that we owe the establish- 

 ment of this process, and the supply of the necessities for it, so 

 that it can be worked by any one who wishes to do so. The usual 

 three colour records are obtained ; the one from the red screen 

 is printed on a lantern transparency plate and the image is 

 toned to a greenish blue colour, and the other two records are 

 printed on bichromated gelatine films supported on celluloid, 

 exposing through the celluloid. These, after development in 

 warm water, are stained by suitable dyes, and then mounted on 

 the greenish blue image, preferably by cementing them together 

 with Canada balsam. One advantage of this method is that the 

 three coloured images can be tentatively placed together, and if 

 one colour is predominant a little of the dye can be washed out 

 from that print, while if one is deficient it can be stained deeper. 

 A somewhat similar method was introduced in 1895 under the 

 name of " Pinatype " by Messrs. Meister, Lucius & Briining. 

 Three transparencies are prepared from the ordinary three 

 negatives, and under each of these is exposed a sheet of 

 bichromated gelatine. These gelatine prints are washed, and 

 each is immersed in its appropriate dye solution. The dye is 

 absorbed where the gelatine has not been acted on by light, but 

 where the combined action of light and the bichromate has fully 

 affected it, it is hardened and does not absorb the dye. These 

 are called " print plates," for their function is to give up the 

 dyes they have absorbed to a sheet or glass coated with a soft 

 film of gelatine, which is pressed into optical contact with each 

 "print plate" in turn. The "print plates" can be used re- 

 peatedly. Messrs. Sanger-Shepherd have perfected * somewhat 

 similar method for making colour prints on paper , but their 

 gelatine prints, which absorb the dye and then give it up to form 

 the final picture, are developed in warm water and so form low 

 reliefs. As " carbon " prints can be made in any colour, some 

 of the firms that make carbon tissues have devised methods by 



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