High Speed Ink Liquid Interface Dynamics in Ultra Light Coated Virgin Hardwood Graphic Papers
Ultra-light coated virgin hardwood papers demand sub-50nm coat pore radii to balance high-speed inkjet solvent absorption against hardwood fiber swelling.
Capillary Pore Volume
Void Structure
Interconnected air spaces inside a paper coating or fibre network determine the capacity of the material to absorb liquids. The term capillary pore volume designates the total space available for fluid transport within these microscopic channels. This property controls the rate of ink drying and adhesive set time on the carton board.
Measurement Process
Evaluation of the void network uses pressurized mercury intrusion or liquid absorption methods to calculate the distribution of pore sizes. In capillary pore volume assessments, mercury is forced into the dry sheet under increasing pressure to measure the volume of voids at varying diameters. The relationship between applied pressure and intruded volume reveals the pore neck size distribution within the pigment matrix.
This test provides a structural map that guides the formulation of high performance clay or carbonate coatings for uniform print results.
Coating Ingress
Coating formulators adjust the balance of fine and coarse pigments to optimize the void structure for specific printing processes. When capillary pore volume is too low, ink solvent remains on the surface, causing slow drying and eventual set-off on the press. High volume levels can drain the ink binder too quickly, leaving the pigment unbound and prone to rubbing off the page.