a method is provided for increasing the water - repellency of a normally water - wettable , bonded , non - woven fabric bearing a surfactant selected from the group consisting of non - ionic surfactants and anionic surfactants . the method comprises heating a selected region of the fabric to an elevated temperature at which the surfactant is unstable , and maintaining the region at the elevated temperature for a time period sufficient to denature the surfactant without damaging the fabric .