Mason Stains ® (by Mason Color Works) are colorants in frit form, which renders them insoluble, removes volatiles, and allows for better control of final product. When used as a glaze stain, we generally recommend adding the stain at 5-8% dry weight to a dry base glaze. The base glaze should contain 12-15% calcium carbonate (whiting) and be free of zinc to achieve the color desired. Mason Stains ® (by Mason Color Works) can also be painted on bisque as an underglaze. Experimentation is necessary to achieve the desired results, but the advantage of Mason Stains ® (by Mason Color Works) is their consistent results in glaze firing.