Improving print quality of coated paperboard

Uniform fiber coverage and low surface roughness are typical characteristics of premium-coated paperboard In a competitive market situation, papermakers have to make the best compromise between these two characteristics, since the former requires contour coating and the latter demands a more leveling coating process. This article demonstrates the possibility to obtain substantial improvements in print quality by simply changing the coating leveling elements (rods or blades) on a conventional coating head without any costly investments. The most common leveling elements for coating of paperboard, namely smooth rods and steel blades (running in bent mode) are here compared to soft-tipped DUROBLADE and systematically evaluated in different combinations for pre-coat and topcoat operations. The measurement results of coating surface roughness, gloss and brightness have been evaluated and compared with the actual print quality Somewhat astonishingly, and perhaps unexpected for many in the paper industry, the relationship between measured PPS, gloss and/or brightness is quite a poor indicator for the rating of printability and of the visual appreciation of the printed sheets. The used materials and methods, together with the trial conditions and resulting values are all described and presented in this article.