ZrSiO4. Zirconium silicate. Zircon. A purified, micronized glaze opacifier. 10%-15% Ultrox Extra added to most clear glazes produces a good white. Add to coloured glazes to make opaque pastels. It can be used in recipes calling for Zircopax, Superpax, etc. (alternate brands and grades differ somewhat in effective opacifying power depending onhowfinely ground they are; Ultrox Extra isa slightly more effective opacifier thanUltrox 500W).

For more information on Ultrox, see theDigitalfire.com Reference Libraryof ceramic materials.