waterproof and water-repellent fabrics, materials treated with various substances so as to make them impervious to water. Permanent waterproofing is achieved by first coating fabrics with rubber or plasticized synthetic resins, then vulcanizing or baking them. Fabrics so treated lose porosity and lightness and when rubberized are subject to cracking. Water-repellent fabrics, sprayed with or immersed in synthetic resins, metallic compounds, oils, or waxes, tend to remain porous and to retain their natural characteristics. Earlier treatments, such as tarring the surface (as for tarpaulin) or oiling (as for oilskin), have been supplemented by highly technical and varied processes and by the method of coating the fibers prior to cloth construction. Some woolen fabrics, especially Navajo blankets and tweeds and other napped textiles, are naturally water repellent.