Volumetric Ratio
Coating formulation parameters express the ratio of solid pigment volume to total non-volatile component volume in dried paint or coating films. Calculating pigment volume concentration establishes the boundary between polymer-rich continuous films and porous, pigment-dominated surface coatings on paperboard. The percentage determines fundamental coating properties, including opacity, ink absorbency, surface gloss, and mechanical flexibility.
Binding Mechanics
Polymer resins bind inorganic pigments like calcium carbonate and kaolin clay together while adhering the coating layer to the underlying raw paperboard fiber matrix. When pigment volume concentration remains below the critical threshold, polymer binder fully encapsulates every pigment particle, producing a dense, non-porous coating with high specular gloss and strong tensile strength. As the ratio increases, binder volume drops relative to pigment surface area, eventually creating microscopic air voids within the dry coating matrix.
These air voids scatter light, boosting coating brightness and opacity while simultaneously increasing ink absorption speed during offset printing. Exceeding critical thresholds weakens binder cohesion, resulting in surface dusting, picking, and poor scuff resistance under press rollers.
Porosity Threshold
Exceeding critical volumetric limits causes binder starvation and severe coating flaking during box scoring. Converting lines maintain pigment-to-binder balances below critical thresholds to preserve fold endurance.
