An Investigation on the Reduction of the Measurements for Quality Control in Four-Colour Newspaper Offset Printing Concerning Colour Deviation and Colour Variation

The four-color content is constantly growing in newspaper offset printing. Quality demands on the newspaper require the monitoring of color deviations on the printed product. The measurement of such deviations by the pressmen can only be stochastic and do not give an overall view of the color deviations that occur during the print run. The suggestion is made to print a highly sensitive color patch on the four-color page as a signal area for color deviations. This signal patch is continuously to be measured with a colorimeter and to be evaluated with regard to (E*ab value. Principal tests with chromatic gray and skin tone show that (E*ab value of the gray patch clearly reacts on color deviations in cyan, magenta, and/or yellow. Skin tone signals magenta and yellow deviations well, but leaves out cyan. The continuous monitoring of the (E*ab value of the signal patch makes it possible to signal the inadmissible color deviation to the pressmen as soon as a limit value has been overstepped. Following this signal a sample should be taken and the control strip should be measured in order to determine the nature and extent of the color deviation and to correct the machine settings.