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.
Dry Pick Strength
Surface Resistance
Paper coating integrity determines how well a substrate resists picking under the stress of high-tack inks during a printing operation. Dry pick strength measures the force required to lift fibers or coating particles from the sheet surface when ink film splits at press speeds. This property dictates the limit of ink viscosity a paper grade can withstand before surface failure ruins the printed image.
Low values indicate that the binder content within the coating lacks the cohesive energy to hold particles against the pull of a tacky ink. Operators monitor this metric to avoid blanket piling and debris accumulation that slows production lines.
Testing Method
Mechanical evaluation requires a printability tester to simulate press conditions with a standardized oil of known viscosity. Laboratory staff apply a controlled ink film onto a sample strip and increase the velocity of the impression until the coating separates from the base paper. The point where fibers or pigment particles begin to pluck marks the failure velocity of the material.
Specialized densitometers or visual inspection under magnification confirm the extent of surface damage at that specific speed.
Manufacturing Influence
Papermakers adjust internal sizing and coating binder ratios to improve the structural cohesion of the finished sheet. Higher concentrations of synthetic latex increase bond energy between pigments and fibers, which raises the threshold for mechanical separation. Calendering pressure during production also compresses the surface to ensure uniform ink transfer without promoting localized weakness.
Excessive moisture content in the substrate reduces these internal bonds, so precise drying control remains the primary method for maintaining consistent resistance levels across a mill run. Proper surface stability remains the absolute requirement for high-speed color registration and clear print fidelity.