Wet strength
Also: wet strength, wet tensile
The fraction of a paper's dry strength retained when saturated with water, critical for food-contact and labeling papers.
Wet strength is the tensile strength of saturated paper divided by its dry tensile strength. Normal paper loses 95 to 99% of its strength when wet. Wet-strength grades, treated with wet-strength resin (typically polyamide-epichlorohydrin, PAE), retain 15 to 40% of dry strength indefinitely.
Wet strength matters in tea bags, coffee filters, wet-label applications (beer bottle labels), meat pads, and sausage casings. Regulators set migration limits on PAE wet-strength resins for food contact.