Causes of yellowing of indigo-dyed, acid washed denim jeans and methods to prevent yellowing are discussed. Several reasons for yellowing are postulated, including the presence of residual manganese from potassium permanganate oxidation, residual iron from the cotton and destruction of the washing machine, and the presence of high levels of transition metals such as titanium, tin, manganese, copper, and aluminum. Several techniques are effective in removing yellowing elements. A good rinse will remove residual metals. If manganese dioxide is the yellowing agent, chemical neutralization may be necessary before rinsing. Some studies, however, suggest that neutralization increases the iron level dramatically. Chelating agents may also be effective in removing transition metals.