Print Mottle of Wood-Containing Paper: The Effect of Fines and Formation, 1996 Process & Product Quality Conference Proceedings

Xintong Lu and David C.S. Kuhn

University of Toronto

Print mottle is an essential factor for evaluating the printability of paper. The present study investigated the relationship between print mottle and several paper properties for a series of 100% TMP offset printed handsheets with well controlled fines content. The handsheets were made with white water recirculation system to maintain fines levels of 0%, 20%, 30% and 40% by weight. Settling times of 5 and 120 seconds were chosen to vary the formation levels. The samples were printed in an IGT proof printer and the print mottle of each sample was determined by a print mottle tester. The formation of the paper was measured by the Video Beta Radiographic Technique. In addition, standard paper properties were measured. The results indicate that the formation of paper is affected by both the settling time and the fines content. As expected, longer settling times resulted in worse formation. However, the effect of fines content was more complex than expected and is more accurately described as an interaction between drainage and mean fibre length. The print mottle is correlated to formation at each fines level. In this study, traditional large scale measures of paper properties could not adequately describe the print mottle variations measured.