Patent GB-190818750-A (GB)
Title: Improvements in and relating to the Manufacture of Grained Screens for Making Colour Photographs
Inventor: BRASSEUR CHARLES LOUIS ADRIEN
Filed: 1908-09-07
Granted: 1909-01-21
Abstract: 18,750. Brasseur, C. L. A. Sept. 9, 1907, [date applied for under Section 91 of Patents &c. Act, 1907]. Colour photography; photo-mechanical printing; sceens.-Grained screens are made from grains of different colours, formed as spheres, distributed in a layer on a support, flattened, and bound together. The grains are blocks of celluloid or the like made of the desired volume ; they may be small cubes, cut from sheets, or small cylinders or prisms cut from threads ; filaments of artificial silk impregnated with celluloid may be used. These particles are dyed and rolled between disks or plates, heated if necessary, until they assume a spherical shape. They should be sifted and rerolled to obtain perfect spheres of equal diameter. The grains may be dusted on a tacky celluloid film or on glass, and are made to join one another by submitting the whole to heat and pressure between polished plates. Or a paper or like support may be stretched and coated with adhesive, such as gum, gelatine, rubber, &c. A shallow frame of cardboard is placed around the paper to retain the spheres, which are dusted on when the adhesive is nearly dry, so that the grains are not held where they strike. When the surface of the paper is covered with spheres of various colours, the adhesive is rendered tacky by moisture, beat, liquid spray, &c. ; when the adhesive has dried, the surplus grains are brushed off. The paper bearing the spheres can be transferred face down on to a thin film of celluloid, preferably poured on a polished metal plate and nearly dry ; when a readymade film is used, it is sprayed with a solvent of celluloid to facilitate adhesion of the spheres. The whole is submitted to heat and pressure to flatten the spheres and cause them to adhere together and to the film beneath, celluloid grains, when used, becoming integral with a celluloid film. To prevent the spheres from running into each other, the paper support can be sprayed with a solution of gelatine and acetic acid, or other isolating-material, an absorbing-roller cleaning the spheres where they touch the film ; or the spheres can be first rolled in or coated with some inert powder or material, such as gelatine. After transfer to the film, the paper support is removed, the interstices are filled by rubbing in suitably coloured powder of celluloid, a thin solution of celluloid is sprayed on the surface, and the film is polished between hot metal plates. To fill in any interstices, the film is daubed at such points with bichromated glue or gelatine and exposed to the action of white light from the reverse side, the soluble part being washed out, and the insoluble part dyed a suitable colour. The film can be finished with a spray of celluloid. The screens can be transferred on to an endless film for use with kinematographs &c. The grains on the paper support may be flattened and sprayed with celluloid to form a film, the paper may be removed and the uncovered side of the film sprayed with celluloid, the whole being then polished. The supporting-film may be of viscose &c. To make the celluloid adhere to the glass the latter must be treated with chrome-gelatine, which is partly exposed to harden it next the glass, and a solution of celluloid containing a common solvent of gelatine and celluloid such as glacial acetic acid is then poured on. The screens can be used, cemented between glass if necessary, either before or behind the lens or at or near the diaphragm plane of the lens. Black-and-white screens can be made from an equal mixture of black-and-white spheres, or preferably sealed between glasses. With any screen the mechanical effect may be broken up by using spheres of unequal diameters, but the quantities of each colour must be chosen to secure equal areas of the different colours. The spheres may be applied by a distributing machine feeding one colour at a time in a continuous row, different colours being fed in different rows, and the spheres may be packed more closely by slightly shaking or tapping the plate or frame before rendering the adhesive tacky, thus leading to the distribution of the spheres six about one, and to the formation of hexagons on the finished screen. Specifications No. 5597, A.D. 1892, No. 22,988, A.D. 1904, No. 9100, A.D. 1906, and No. 4932, A.D. 1907, are referred to.