This article will specifically address the subject of bleaching. It will examine criteria for determining when bleaching is safe and when bleaching is necessary, the ramifications of bleaching a textile, and the various types of bleaches. It is to be hoped that by the end of this article the reader will have a better idea about why conservators are reluctant to bleach, how bleaching affects their textiles, and why bleaching sometimes will not remove a stain. Staining is a problem often encountered in the textile conservation field. A stain is identified by an area on a textile which has discolored contrary to the intention of the maker.
Natural fibers are extremely absorbant materials.
Body oils, liquids, soils, and organic substances are all readily absorbed onto the textile fibers. These soils and organic substances oxidize over time to colored stains. Bleaching does not remove stains. The substances causing coloration of the stain is merely altered so that the color of the stain is less intense or invisible. Several molecular structures and physical phenomena give rise to color or darkening on a fiber.