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608 History of Three-Color Photography
making the screen was with a greasy resist, and the process was said to be applicable to cinematography.
J. T. Smith215 considered the usual methods of making the patterns were all defective and proposed a compound one, in which a colloid resist was used to prevent the etching action of certain etching-coloring solutions on celluloid, which was to be the support. Stained fish-glue was applied in pattern to the base, then insolublized by dichromating and light or formaldehyde. The etching solution was preferably anilin with dyes dissolved in it. The process seems to have been a two-color one and after varnishing the emulsion was to be coated direct on the screen. A black and white monochrome picture was to be alternated with the colored ones. The same inventor216 would also prepare the surface of celluloid by treatment with abrading powder, or liquid with solvent action, and apply the dye in solution of solvents of celluloid.
The Compagnie Generale Phonographes et Cinematographies217 proposed to take a negative on a panchromatic film and color each picture on its positive and photograph the same through a tri-color screen. From the composite negative thus obtained, a positive was made and projected through a reduced line screen. W. G. Finnigan and R. A. Rodgers218 proposed to expose a film in contact with a piece of ground glass. From the negative a film covered with minute particles in any pattern, coated with positive emulsion was used, and the result was said to be in natural colors !
I. Kitsee219 proposed to make a template with transparent spaces equal to the opaque, and from this to make a master key of longitudinal lines the full width of the emulsion-coated base, by exposing to an arc lamp and then developing. From this a print was made on dichromated gelatin, containing a dye. The exposed parts would be hardened, whilst the unexposed would swell in water and the dye be discharged. The lines would also be raised up and the second color was to be applied by a roller. Later Kitsee220 proposed to apply the elements by means of rollers or a spray, using Canada balsam, dissolved in alcohol and stained up, then to dye the interspaces with another color. The inventor lays stress on his discovery that an aqueous solution of a second dye will not stain up a resinous resist, and claims the use of one color miscible only in alcohol and the other only in water. Later221 a template was to be made by reducing down by photographing squared paper, the alternate lines of the squares being filled up with ink. Apparently this was also a dichromated gelatin process. Another modification222 was a resinous resist and the celluloid itself dyed up. While a modification of the formation of the elements was patented.228
R. Wellesley and T. M. Saunders224 patented a method of transferring a color screen to a positive picture from a temporary celluloid support. The positive was to be passed through an adhesive-applying ap