Statistical Analysis of Optical Density of Web Letterpress Printing.

A statistical analysis made of the inking variation in the printing of telephone directories to determine the major sources of variation contributing to inconsistency in the inking from page to page and also within a page is described. The sources of variation measured were the variation in each type of work: run-to-run variation on each press used; within run, cylinder to cylinders across the web, around the cylinder, and plate to plate variation. The analysis revealed a need for further study of plate thickness and other platemaking variations affecting darkness and sharpness of printing and also the correction of cylinder-to-cylinder differences.