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Summary:
This paper reports on an extension of a previous paper on the subject of color variations on press. There it was explained that inherent type color variations define the lowest level of color variation that can be realized under a given set of press operating conditions. To begin, a more detailed description is given of the procedure used to assess the magnitude of such density variations. Measurements of inherent type variations on two typical offset presses are presented and compared with three similar sets from the previous paper, for the purpose of establishing a benchmark for printing on coated paper. This is followed by presentations of data that show the effect on inherent type variations of an impervious substrate, stochastic versus conventional screening, the absence of water, and the use of a non-paste ink. The conclusions include a definition of the upper bound of inherent type density variations on a lithographic press, the effect of the above process changes on density variations, and an explanation of the factors that determine the shape of the curves of density variations versus screen or dot area.