Capillary Absorption Testing Standards in Coated Printing Substrates
Substrate capillary absorption speeds govern ink setting rate, dryer energy consumption, and cross-web print defect thresholds across high-speed converting runs.
Board Coating Consolidation
Coating Transition
Transitioning a wet coating color applied to paperboard into a stable, dry porous structure occurs through a distinct dewatering and packing process. This immobilisation of pigments, referred to as board coating consolidation, begins as water drains into the paperboard base or evaporates from the surface. The process concludes when the suspended particles can no longer move independently, locking the coating structure into its final porous state.
It represents a critical phase that defines the mechanical and optical properties of the finished board surface, establishing the baseline for printability.
Pore Formation
Capillary forces drive the remaining liquid vehicle out of the void spaces during the later stages of drying. As the particles are forced closer together, they form a solid network with a specific distribution of pore sizes. This network determines both the light-scattering property of the coating and its capacity to absorb print inks.
Drying Phase
Controlling the temperature profile along the drying section of the coating machine is essential to prevent binder migration. High initial drying rates can pull the latex binder to the surface, creating an uneven skin that hinders future ink absorption and leads to printing defects. A gradual drying strategy ensures uniform consolidation and avoids surface defects.