Pre-damping effects on water absorption and drying dynamics in flexographic printing, TAPPI Journal November 2025

Application: The work presented here concerns the speed of fluid imbibition into a coating layer in the context of flexographic printing. However, this is also valid for other printing techniques, such as inkjet and offset lithography, where water needs to be quickly removed from the ink. Control of coating porosity with mineral and binder choice, as well as topography and surface energy, are already well-known factors in impacting good print quality and are often discussed in the literature. The technique of moistening the surface provides another lever in the design of coating for printing.

Author: Janet Preston, Eli Gaskin, and Martti Toivakka

ABSTRACT: Optimizing flexographic printability can involve the ink and the substrate, as well as the printing process. It has been widely reported in the literature that controlling topography of the substrate and its porosity are vital for good flexographic printability, especially when using water-based inks. This study focuses on how pre-damping a surface impacts liquid absorption and improves wet trapping (ink on ink with no intermediate drying) in flexographic printing. A Prüfbau universal print tester was adapted to analyze flexographic wet-on-wet ink printing and trapping using yellow and magenta inks for contrast. Slow drying of the first ink layer (yellow) leads to mottle when the second layer (magenta) is applied. The study explores the “wet sponge” hypothesis: a pre-damped surface should absorb liquid faster. The Lucas- Washburn equation describes long-term absorption, but it does not capture short-term uptake, which instead follows a linear dependence on time.