GB555785A - Apparatus for photographic printing - Google Patents

Abstract

555,785. Paints. DEHN, F. B. (Martin Co., G. L.). June 27, 1941, No. 8131. Drawings to Specification. [Class 95] [Also in Group XX] A photographic plate for receiving copies of drawings &c. consists of a metal support having on its surface a light-sensitive layer which is prepared from pure bone gelatine and is separated from the metal by a layer of white paint which is inert with respect both to the metal and the sensitive layer. The original is preferably made on a metal sheet as of aluminium or an alloy thereof, the surface of which may be anodised and coated with white paint. It is photographed on to a plate of aluminium or aluminium alloy, the surface of which may be emulsion layer coated over a substratum of white paint which is inert to both the metal support and to a light sensitive emulsion, e.g. a paint known under the Trade Name Preparakote and consisting principally of titanium dioxide, zinc oxide, powdered pumice, naphtha and mineral spirits. The emulsion may be prepared by dissolving the pure bone gelatine in water, adding an aqueous solution of potassium iodide and potassium bromide, and then adding under a safe light, an aqueous solution containing silver nitrate, nitric acid, and salicylic acid (preservative). The emulsion is digested at 125‹F. in a light-tight container for four hours and is then wiped on the painted metal surface with absorbent cotton.