In the field of rotogravure, print quality requirements are particularly high. Increased brightness and whiteness in substrates, such as paper and paperboard, have increased the visual assessment of white area contamination, i.e. background discoloration in non-image areas. This has been increasing over recent years with no evident explanation. Publishers have made efforts to increase print quality by using whiter substrates, which has lead to a visual appearance of rotogravure background darkening (RGBD), in the in the most serious cases called toning. Another phenomenon that occurs in rotogravure printing is missing dots, i.e. areas where the engraved cells are unable to transfer ink. The aim of this work was to investigate what causes toning (background discoloration) and missing dots in gravure printing. Toning is a non-wanted result of ink oozing from under the edge of the doctor blade onto the non-image areas of the gravure cylinder. The cause of missing dots is insufficient ink transfer into/out from engraved cells and generally pinpointed to non-uniform contact between the engraved cells in the printing cylinder and the substrate.
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