Cobb Test

Surface Sizing

Sizing efficiency dictates how effectively cellulose fibers resist capillary action and subsequent liquid migration through the sheet matrix. Wetting dynamics depend heavily on rosin or alkyl ketene dimer retention levels achieved during sheet formation on the wire. High absorption rates signal inadequate chemical barrier formation, which leads to immediate box failure under high humidity storage conditions.

Converting plants reject incoming linerboard rolls failing the minimum Cobb threshold because poor water repulsion ruins subsequent starch adhesive bonding during flute lamination.

Moisture Defense

Hydrophobic performance protects corrugated containers from structural collapse when stacked inside refrigerated freight environments for extended periods. Condensation accumulation on exterior box walls tests the limits of internal sizing applied during primary paper manufacturing. Excessive liquid penetration softens the fluting medium, reducing the edgewise crush strength required for safe warehouse pallet stacking.

Finished packaging specifications establish strict upper limits for fluid uptake to ensure corrugated boxes maintain stacking integrity throughout supply chain distribution cycles.