GB415399A - Improvements relating to photo-mechanical printing processes - Google Patents

Abstract

415,399. Producing photomechanical printing surfaces; photographs. ECKARDT, E. E., 39, Bayreuther Strasse, Dresden, Germany. Feb. 18, 1933, No. 5072. Convention date, Jan. 16. [Class 98 (ii).] Photographs or negatives giving the appearance of an etching or engraving are produced by subjecting a gelatine silver halide layer after exposure, development and fixing, to treatment in a warm water bath which tends to soften the gelatine, the softening process being continued until the silver image particles coalesce to form a reticulated or ' skeletonized ' pattern, as illustrated. The skeletonized image may be used for the production of photomechanical printing surfaces, e.g. it may form an etching resist or may be used directly for collotype &c. ; alternatively, it may be utilized for printing on to a chromate layer in which case the image is reddened by a uranium toning bath. The Specification describes a number of modified methods. Thus the plate or film may be subjected to a warm developing bath or a warm fixing bath ; to alternate warm and cold water baths ; to a very rapid developer ; to a warm oil bath ; or to a bath of potassium ferrocyanide, with or without alternating warm and cold baths. The silver image may be intensified, e.g. with mercury. Reference is also made to the use of silver halide emulsion containing starch, chalk or like translucent materials.