The halftone process is so much a part of printing today that it is often hard for printers to conceive of the notion of reproducing an image without a screen. Before the idea of breaking up an image into small dots came along however, printing was being done with lithographic methods which produced excellent results and the main concern of the theorist and technician was how to produce a more consistent, higher-quality, continuous tone image. Perhaps it is unfortunate that the advent of the halftone process distracted thought from this area to such a large degree, since it wasn't until the early 1950's, a century after the first photo-lithographic prints were made with bitumen on stone that interest became centered once again on the possibilities of creating continuous tone images using conventional commercial equipment. This revived interest in "screenless" methods of reproduction gave rise to many processes which employed concentional offset lithographic equipment to produce continuous tone images. While some variation was present in the approach of each of these processes, their fundamental principles were closely aligned with conventional lithography and it was eventually hypothesized and generally accepted that the mechanism of image formation in these plates had to do with the grain structure of the substrate being used. While excellent results were achievable with these plates, they exhibited a lack of consistency and a touchiness in the area of exposure which made them unsuitable for adoption in commercial use on more than a limited basis. In 1969 the Association Products Plate was introduced. This plate was unusual in that it seemed to be based in principle more on the collotype process than on conventional lithography; that is, it depended more fully on the light sensitive material being used than on the substrate. This plate too, exhibited lack of consistency and exposure problems which limited its adoption. Unlike the so called "random dot" processes mentioned above, the image forming mechanism of the Association Products Plate has not been satisfactorily defined. In choosing to study the Association Products Plate from the standpoint of coating variations it was hoped to arrive at a demonstrable relationship between the coatings and subsequent tone reproduction , such that, as the coatings moved from the influence of the plate grain, tone reproduction should exhibit greater consistency and predictability. This, it was hoped, would establish the coatings themselves as the primary imaging agents, pointing the way to further study. The results did not support this contention.
Library of Congress Subject Headings
Printing; Printing plates; Lithography--Metal plate processes
Department, Program, or Center
School of Media Sciences (CIAS)
Woodhouse, Mark, "A study of the effect of coating variations on tone reproduction in the Association Products Plate" (1979). Thesis. Rochester Institute of Technology. Accessed from
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