Studies in Wrap-Around Letterpress Printing.

A designed experiment consisting of 81 tests was run by GATF to determine how certain plate and press variables affect the quality of direct printing from thin, wrap-around relief plates. Five variables, each at three levels, were examined: these were (1) type of plate, (2) batch of plate, (3) type of impression cylinder packing blanket, (4) amount of impression squeeze, and (5) ink film thickness. The criteria of quality were tone reproduction, smoothness in shadow tones, midtone jump, embossing and resolution. Experimental details are given and findings concerning the interrelationships between the various factors are presented.