ABSTRACT
Textiles are made repellent to withstand the stresses of use and of the environment. Thus, rainwear is treated to withstand a downpour directed at its outer surface. A firehouse is tightly woven to contain water under pressure against its inner surface. Finished textiles are for the most part hydrophobic. Nylons, polyesters, and wools are inherently water repellent; and finishing processes usually convert even hydrophilic textiles into hydrophobic ones. In the capillary system of textiles, the advancing contact angle is a measure of the maximum value the fluid stain assumes on spreading or inflating. Dry, particulate soils also tend to build up in irregular voids and cross-over points. The mechanism is mainly that of mechanical entrapment where soiling increases with the weight and complexity of the fabric. Surface irregularities, and pits and crevices, need not always be smoothed over or filled in to increasing soiling resistance.
