Patent GB-190815050-A (GB)
Title: Improvements in or relating to the Photographic Reproduction of Colours.
Inventor: CAILLE EDMOND CHARLES GUISLAIN
Filed: 1908-07-15
Granted: 1909-07-15
Abstract: 15,050. Caille, E. C. G. July 16, 1907, [date applied for under Section 91 of Patents &c. Act, 1907]. Colour photography. -In a process of colour photography, the object is photographed through a screen comprising a number of lines and dots A, B, C, arranged as shown and coloured orange, green, and violet, and the support or surface on which the final picture is produced is covered with a corresponding series of lines and dots coloured with the complementary colours blue, red, and yellow, suitable registering- marks being provided on the screen and on the support. From the negative first obtained, a transparent positive or "intervening cliche " is made. The coloured support, having been coated with a sensitive emulsion, is exposed under the transparent positive. After developing, fixing, and washing, the colours on the support appear in these parts which were masked by the opaque parts of the positive, while those parts which correspond to the transparent parts of the positive are covered with black of silver. These black portions are then whitened by immersing the support in a solution of bichloride of mercury, subsequent tarnishing being prevented by abstaining from washing, thus leaving a little of the bichloride in the film. Certain other chlorides such as bichloride of copper may be used instead for whitening, bichloride of mercury being used afterwards for fixing. In a modification, ,the object is photographed through the screen directly on to a removable pellicle which, after whitening as described, is transferred to the coloured support. In another modification, a zinc or other printing-surface is prepared by known processes from the transparent positive, and the block obtained is coated with a fatty white ink and caused to make an impression on the coloured support. In making the screen, three negatives corresponding to the three networks are prepared by photographic reproduction of originals drawn to a larger scale. The glass or like support coated with a thin layer of bichromated gelatine is then exposed under one of the negatives, washed, and dyed with the appropriate dye. A second thin layer of the gelatine is then applied and exposed under another of the negatives, washed, and dyed, and similarly a third layer is applied and correspondingly treated. A. colourless transparent varnish or a well insolated layer of bichromated gelatine may be applied after each dyeing. The lines of the screen may be of greater or less width according to whether the corresponding colour is required to predominate or not, and any suitable pattern may be used other than that shown. Suitable dyes are specified. The Specification in its original form, as open to public inspection under Section 91 (3) (a), states also that the screen may be formed by the superposition of three separately prepared pellicles or films, and that there may be intervening white spaces in the design of the screen. The supports consist of paper or cardboard made non-hygroscopic and inextensible, and the coloured lines and dots are produced on them by any suitable means such as micrographic machines, or by means of bichromated gelatine printing-surfaces obtained by photographic processes from the negatives used in making the screen; To prevent the colours from being spoilt by the subsequent treatment they may be coloured with an impermeable varnish. This subject - matter does not appear in the Complete Specification as accepted.