Impact of local variation in coating structure on uniformity in print gloss

Abstract

Point-to-point variation in the gloss of a print has been reported to be one of the most visually disturbing aspects of a printed paper. This work sought to determine the effect of pigment and binder content on the coating structure, surface properties, and print gloss variations occurring in a printed offset paper. The results from a pilot coating and full-scale sheet-fed offset printing trial are reported, with special emphasis on uniformity in print gloss. The effect of calendering and print impression also was considered. Uniformity in print was analyzed in terms of print gloss variation (PGV) in the heavily inked areas. Calendering and point-to-point variation in coating porosity had a significant effect on PGV. The observed nonuniformity in print is discussed in terms of local variations in coating porosity and local variation in coating micro-roughness. Under the conditions investigated, uniformity in surface porosity decreased with increasing latex content, but increased with clay content.