Influence of Pigment Size on Wet Ink Gloss Development, 1997 Advanced Coating Fundamentals Symposium Proceedings

The development of wet ink gloss at short times is reported for the first time using actual printing inks and paper coatings. The ink gloss is recorded every 0.1 second after printing and followed for 20 seconds. The gloss at short times correlates well with the final gloss and the tack-build slope: this result indicates that the leveling of filaments after printing is a critical step to obtain high gloss prints. Fine pigment sizes are found to arrest the leveling of filaments formed in the printing nip. This arresting of leveling produces a lower gloss ink film compared to the unprinted coating surface. One theory that explains the results is that ink solvent or vehicle is removed from the ink layer to thicken the remaining ink film. A theoretical model is proposed to describe the surface-tension-driven leveling of ink films while vehicle is being removed. The model points out the important properties of inks and coatings which promote ink film leveling.