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Summary:
Gloss is an important aspect of a printed sample in terms of quality. Gloss dynamics have not been well documented yet. A good understanding of the influence of the ink rheological properties on gloss and its dynamics is not available. The wet ink gloss evolution on Mylar film was recorded every 0.1 second, immediately after printing, and followed for 60 seconds. A specially designed gloss-meter directly mounted on a KRK was used to record the ink film gloss dynamics. Two inks with different setting rates were tested. Both inks were characterized on a rheometer in terms of steady and dynamic behaviors. As the leveling proceeds with the time, the ink film surface becomes smoother, increasing the ink film gloss. On plastic film, the high setting rate ink produces a lower print gloss development than the low setting rate ink. Rheological measurements reveal that the high setting rate ink has a higher viscosity and a faster elastic structure recovery for the range of shear rates involved during leveling. Thus, after printing on the plastic film, the higher viscosity of the high setting rate ink slows down the leveling and its faster elastic recovery limits the extent of leveling. On thin films of paper coatings, at high pigment volume concentration, the two inks are set by capillary sorption of the ink mobile phase into the porous structure of the substrate and the ink rheology has little influence. On a coating containing a large content of latex that is non interactive with the ink mobile phase components, the ink leveling patterns are similar to the case of the plastic film. However, when printed on a coating containing a highly interactive latex with the ink components, the ink rheology is the most important factor to determine the gloss dynamics. This results contribute to a better understanding of the ink gloss development as related to the ink rheological variables.