Details:
Summary:
The various factors which affect color variations on letterpress and offset printing, between sheets or signatures, and within sheets or signatures, are described and discussed. Theoretical calculations for the magnitude of ghost images are described. Also, the use of variance of ink-film thickness to compare the effectiveness of various roller arrangements is described and illustrated with an example. The relationship between starvation patterns, vibration, and key spacing is discussed. The problems with the ink fountains are described and the improved nylon block segmented ink fountain blade is described. Finally methods are discussed by which these various factors may be evaluated by actual press tests using densitometer readings and statistical quality control methods.