Patent GB-754059-A (GB)
Title: Improvements in or relating to the photographic production of monochromatic and multi-coloured pictures
IPC: G03C11/18
Filed: 1954-08-16
Abstract: 754,059. Photographic pictures. WATSON, G. H. R. (Variofix (Proprietary), Ltd.). Aug. 16, 1954, No. 23800/54. Class 98 (2). Pictures, primarily for advertising purposes, are produced on portable plates as of asbestoscement, aluminium or plastic material or on surfaces such as walls as of masonry, wood or metal, by sealing the pores of the base if it is composed of porous material, superimposing a light-sensitive material, projecting a picture thereon, developing and fixing the latent image, removing the emulsion from the unexposed parts, covering the surface with a prime coat of oil paint, and removing the oil paint together with the emulsion from the exposed parts. Various procedures are described or suggested, thus an asbestos-cement plate may be soaked in zinc fluosilicate solution and dried to seal the pores, coated with a colourless chlorinated rubber varnish, sensitized with a gelatino-silverhalide emulsion, exposed by projection from a half-tone positive, treated with a hardening developer, fixed, treated with water at 40- 50‹ C. to remove unhardened emulsion, and, after the hardened emulsion has dried, with a pine-gum varnish, and then the oil paint. When the latter has dried the surface is washed with luke-warm water to remove the paint and varnish on the hardened emulsion and then with dilute sulphuric acid to remove the emulsion, and a coat of colourless chlorinated rubber varnish is applied to make the final picture weatherproof. For multicolour pictures the emulsioning and other procedures are repeated with exposures through a plurality of diapositives, a suitable sequence being blue, yellow, red and black. Metal base-plates may be degreased with ammonia, roughened if necessary before treatment, and then, desirably, covered with a coat of chlorinated rubber varnish, containing a white pigment before sensitization and procedure as above. Plates prepared from asbestos, cement and calcium carbonate may be sealed with nitrocellulose varnish, or an existing surface such as a wall may be covered with a coating of calcium carbonate or ground limestone with nitrocellulose varnish as agglutinant, and treated similarly except that a stronger sulphuric acid is used so as to remove both emulsion and the nitrocellulose varnish from the exposed parts, and then the surface may be treated with a gum arabic-nitric acid solution to etch the carbonate areas and produce a thin layer of calcium nitrate which does not retain oil paint when wet in such areas, so that a final colouring may be applied over the whole surface to adhere to the prime coat on the unexposed parts but which can be washed off the exposed parts. If desired, the exposed parts may be coloured by application of oil paint when the calcium nitrate layer is dry. Relief pictures may be made by continued action of the gum arabic-nitric acid solution on the exposed parts, such solution having no effect on the paint and varnishprotected unexposed parts. Production of a multi-coloured picture with colours such as red, blue and yellow disposed side-by-side, using - successive exposures and taking advantage of the property of calcium nitrate of accepting paint when dry and refusing it when wet, is referred to.