Abstract: Method and composition for preserving fibrous materials. A urethane and thinning agent are mixed, and a fibrous material is contacted with the mixture and dried. An anti-oxidant, thinning agent or drier may optionally be mixed with the urethane and thinning agent. Extenders, plasticizers and ultraviolet light absorbers may also be used to advantage in some applications. The method and composition have particular application for use as a preservative for fishing and shrimping nets, uralkyd resins being the preferred urethane for this use.