Mineral Coating Pigment Packing Micro Geometry and Pore Volume Distribution
Pigment micro-geometry and particle packing dictate coat pore volume distribution, controlling ink vehicle absorption rate, print gloss, and coat strength.
Binder Migration Dynamics
Particle Movement
Physical transport describes the redistribution of liquid or solid components within a coating as the moisture evaporates. High heat or rapid airflow often triggers binder migration dynamics which pull the latex or starch particles toward the surface. This movement changes the chemistry and porosity of the final dried layer.
It is a fundamental factor in the production of coated papers for offset and inkjet printing.
Drying Rate
Capillary action moves the fluid phase toward the evaporation front and carries the smaller binder particles with it. If the drying rate is too fast, the binder concentrates at the extreme surface and seals the pores. This phenomenon is known as mottle and results in uneven ink absorption.
Slower drying allows the binder to remain distributed more evenly throughout the coating thickness.
Print Quality
Substrate porosity also influences the direction and speed of the movement. A highly absorbent base sheet pulls the fluid downward into the fibres and creates a depleted region near the surface. This depletion can lead to dusting or picking during the print run because the coating is no longer held together strongly.
Controlling the balance between heat and absorption is the primary way to manage these dynamics.