Print gloss is one of the most important attributes of a printed product. While is it well known that gloss mainly depends on the surface smoothness, it is less well understood how paper, inks and varnishes interact to generate a specific gloss. Ink films are known to start from a highly textured structure after the splitting of the ink film, but need to level to a smooth surface before the ink solidifies.
A model is developed that predicts the surface tension driven leveling of an ink film. The model inputs are the ink rheology, the surface tension of the ink, and the solids of the ink. In addition, the pore structure of the paper is taken into account to predict the setting of the ink on the paper. The model includes the formation of a filtercake that grows during setting, but then limits the leveling of the ink film. Other predictions, based on other ink setting models are compared.
The model results are compared to experimental results. The low gloss that can be obtained with certain inks and ink film thicknesses is linked to the ability of the ink films to level. As ink oil are absorbed into the coating layers, the filtercake thickness increases decreasing the ability of the ink film to completely level.