Penetration Depth

Fluid Transport

Capillary pressure governs how fast water or ink moves through microscopic channels between adjacent wood fibres. Penetration depth depends directly on sizing agent concentration and the degree of internal hydrophobicity achieved in the wet end. Paper machines regulate this movement by adjusting press nip pressure to consolidate the sheet structure before drying cylinders lock the pore geometry in place.

Excessively porous furnishes accelerate fluid travel and cause striking through on lightweight packaging substrates.

Surface Retention

Contact angle measurements quantify wetting behaviour and predict how deep a droplet will sink into a paper surface upon impact. Penetration depth sets the threshold between optimal ink anchorage and undesirable print-through defects on thin catalogue stocks. Converting plants monitor this metric to prevent adhesive bleed-through during lamination processes where excessive glue migration ruins the appearance of the finished carton.