Bleaching may be defined as the alteration of coloring matter in such fashion as to cause it to reflect more true white, or the solubilizing of such coloring matter to make it possible to wash out the color substance, or both.  (2) The most common method of bleaching is the oxidation of the coloring substance although reduction with ZnS2O is sometimes used with ground-wood. This discussion will be limited to bleaching by means of oxidizing agents namely: chlorine and calcium hypochlorite