Capillary Pressure

Substrate Tension

Mill engineers regulate surface energy parameters during the wet end forming stage to govern capillary pressure across the entire web width. Sizing agents applied at the size press alter contact angles, modifying how deeply liquid varnishes penetrate porous linerboards during offset printing runs. Operators monitor the resulting penetration rates to prevent excessive binder migration from starving surface pigment layers, which otherwise causes dusting and poor print density.

Tight tolerances across production shifts ensure that incoming folding boxboard accepts aqueous barrier coatings evenly without pinholing or premature strike through. Converting plants verify these wet out characteristics using standard Cobb tests before releasing substrates to high speed gluing lines.

Wetting Dynamics

Surface active contaminants disrupt natural absorption kinetics, forcing converters to adjust machine speeds to compensate for altered capillary pressure values inside the fibrous matrix. Fibres sourced from recycled pulps exhibit higher surface heterogeneity than virgin kraft pulps, creating localized variations in fluid absorption across a single sheet. Converting machinery must apply uniform nip pressure during lamination to overcome variable void fractions within the paperboard structure.

Final print quality depends on matching fountain solution delivery rates to the specific imbibition speed of the substrate.