Some Factors in Bi-metal Lithography.

The relative unreliability of albumin and deep etch lithographic plates when used for long runs, has led to intense interest and study of the bi-metal plate. The use of two metals in the litho plate surface was proposed nearly fifty years ago. Several reviews have been published by Mertle, Elton, Blau, and others describing the several proposals and their processing characteristics. The bi-metal plate offers an opportunity for reliability on the press equivalent to that attained by Ietterpress processes. With the proper plate, giving improved plate life on long run jobs, it should be possible to reduce plate making costs mainly through reduced makeovers. Short runs can be benefited only if quality is improved, and no substantial amount of evidence is yet available to show that equivalent quality cannot be attained by conventional plates. Experimental results from nearly fifteen years of intermittent studies of bi-metal plates have indicated that good results can be attained from the chromium-copper plate produced either from negatives or positives by the etching methods.