Absorption Rate
Direct liquid intake describes the speed at which paper fibres pull water into their structure through physical proximity. The contact moisture sorption of a substrate determines how quickly aqueous inks or adhesives penetrate the surface during high speed converting. Physical intake is distinct from vapor transmission because it involves the movement of liquid water into the capillary structure.
Conversion Influence
Coating formulations and surface sizing agents regulate the speed of fluid uptake. If contact moisture sorption occurs too rapidly, the carrier fluid in an ink may migrate into the core and leave pigments poorly bound on the surface. Conversely, insufficient absorption leads to slow drying and potential smearing on the folder-gluer.
Control of fibre orientation and refining levels helps maintain the necessary balance for bonding.
Measurement Protocol
Standardized pressurized tests quantify the volume of water absorbed over a fixed duration. A high contact moisture sorption value indicates a porous or unsized sheet that will likely require higher adhesive application rates. Instruments measure the weight gain of a sample after exposure to a liquid column for specific intervals such as sixty or one hundred seconds.
Surface energy also influences how the liquid interacts with the outer layer. Testing ensures that the material meets the requirements for glue lap integrity and print density.
