The mordant most frequently used by natural dyers for animal and cellulose fibers and fabrics. It improves light and washfastness of all natural dyes and keeps colours clear. It is inexpensive and safe to use (but should not be ingested). This form of alum is refined from bauxite, the raw state of aluminum ore, and is free from the impurities some other alums can contain (such as iron). Use at 12-20% WOF.