Surface Interaction
Pigment retention at the substrate boundary defines this property during the lithographic cycle. Pressroom ink holdout dictates the degree to which a vehicle remains on the surface rather than migrating into the fibrous interior of the sheet. Variations in fibre density and sizing efficiency determine the resistance to penetration.
High levels of this attribute allow for sharper dot reproduction and increased optical density while lower levels lead to dot gain and substrate dulling.
Performance Limit
Uniform coating weight across the sheet provides the most reliable foundation for controlling liquid penetration. Mechanical pressure applied by the blanket cylinder during the impression cycle forces the fluid medium into the structure of the cellulose. If the internal sizing chemicals fail to fill the voids between fibres, the vehicle wicks away from the pigment, leaving behind a dry or chalky appearance.
Printers select stocks with specific surface energy ratings to match the viscosity of their chemical formulations. Proper balance ensures the fluid stays in the nip long enough to deposit the colourant without smearing under tension.
Measurement Standard
Quantitative assessment occurs by comparing the optical density of printed solids against an identical formulation applied to a non-porous reference material. Analysts evaluate the ratio of light reflected from the solid areas of the sheet to determine how much of the vehicle vanished below the surface plane. This calculation identifies the efficacy of clay coatings or synthetic binders in preventing structural loss of the ink film.
A stable bond between the ink and the top coating preserves the intended aesthetic and physical integrity of the print.
