- Opacifier
- Very high melting point of 4892°F, second only to magnesium oxide
- As an opacifier (comprised of 1-15% Not recipe), particles remain unmelted and suspended in glaze, giving it reflective quality hard white is sometimes called (refrigerator white.”.
- To temper this bright white you might add .25% iron oxide or perhaps use equal amounts of zirconium silicate and tin oxide to opacify glaze
- Makes glazes stronger and more expensive, by weight, than tin oxide.
- Has low expansion and contraction rate
- May reduce crazing
- Has high surface tension and viscosity
- Will stiffen glaze.
- Usually introduced as zinc silicate
- Won’t create opaque mattes because contains glass-former, silica
- Insoluble and has no known toxicity.
- Zircon, zirconium oxide, and zirconium silicates, including brand-name products Zircopax, Ultrox, Supertax, and zircopax Plus are all insoluble sources of zirconium.