Scouring is a preparatory treatment of certain textile materials. Scouring removes soluble and insoluble impurities found in textiles as natural, added and adventitious impurities, for example, oils, waxes, fats, vegetable matter, as well as dirt. Removing these contaminants through scouring prepares the textiles for subsequent processes such as bleaching and dyeing. Though a general term, "scouring" is most often used for wool. In cotton, it is synonymously called "boiling out," and in silk, and "boiling off."