GB391493A - Improvements in and relating to colour photography - Google Patents

Abstract

391,493. Colour photography. WILLIAMS, J. E., Miskin Manor, Pontyclun, Glamorgan. Oct. 30, 1931, No. 30101. [Class 98 (ii).] In the production of coloured photographs by printing from colour-record negatives on to pigmented gelatine sensitized with bichromate carried by the final support, the sensitized gelatine applied to the support is so treated as to present a grained, irregular or reticulated surface. The development and preservation of half tones is thereby assisted and the layer is more effectively secured to the support. To obtain the irregular or reticulated surface, the sensitized gelatine emulsion is applied in the warm, liquid state to a muslin or linencovered lithographic stone, board, or other suitable surface and the damp print is squeezed thereon, cooled by a fan, stone or piece of glass, and stripped. A second or third coating may be similarly applied to obtain a greater depth of colour. A blue print is preferably utilized for the blue image. Thus, for a three-colour process, a blue print obtained from the orange negative is dried and coated with bichromated gelatine containing yellow pigment and is then exposed under the violet negative ; after development and drying, a red, bichromated gelatine emulsion is applied and a print is obtained from the yellow negative. For the yellow pigment, deep chrome with a little vermilion is employed ; and for the red, Alizarin crimson with a little vermilion. To preserve the whites, the blue print is brushed over with hydrochloric acid. As soon as the red image is developed, the print is immersed in a strong chrome alum bath and, after drying, is coated with a suitable varnish or gelatine glaze. In place of the blue print, a paper coated with a blue gelatine film may be employed. The prints may be made from a multi-colour screen plate, starch-grain negative, &c. by using complementary printing light for each print. More than three colours may be employed, e.g. a five-colour print may comprise a blue print with superposed prints in bright green, yellow, red, and mauve.