Measuring Water Induced Roughening of LWC Paper and Its Effect on Printed Gloss, 1996 Process & Product Quality Conference Proceedings

M. A. MacGregor

VSPT

We developed a millsite procedure to precisely apply water to lightweight coated paper in the small amounts occurring in commercial web offset printing. The reduction in Hunter 75º gloss is an indirect measure of the roughening effect that this thin water film has on the white paper. Commercial offset printing trials suggest that less than half of the white paper gloss reduction appears as a printed gloss reduction. This is because the Hunter gloss measurement does not distinguish between the gloss reduction from macro-roughening and that from micro-roughening which the ink film later covers. Despite this limitation, the simple water treatment procedure can still help to identify more quickly paper making process and material changes that give reduced roughening and have a chance to improve the final printed gloss. Not all of the water-induced roughening occurs at the fiber dimension level; the coating also exhibit-ed a significant micro-scale roughening from the water. Key words: Hunter 75º gloss, fiber rising, print roughening, facet angle, IGT Print Tester.