How much Zircopax do potters use in a glaze?

Across 1,098 published glaze recipes containing it, the typical amount is 9.4% of the dry batch, with half of recipes between 5% and 12%. Colorants and additives sit far lower than fluxes and glass formers; treat these as a range to test around, not a target.

What cone is Zircopax used at?

It appears in recipes across the range; the most common cones among published recipes are cone 6, cone 10, cone 8. Where a material sits depends on the rest of the recipe more than on the material itself.

Is Zircopax safe to use?

It carries no specific hazard flag beyond the general rule for all dry ceramic materials: avoid breathing the dust and read the supplier's SDS.

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Glaze material · Opacifiers

Zircopax

Also sold as: zirconium silicate, Ultrox, Superpax

The modern opacifier, used at 3–15%: harder and cheaper than tin, a slightly more translucent white.

opacifierContributes: ZrO₂ · SiO₂

In published recipes

Used in 1,098 of 10,859 glaze recipes (10%)

Typical amount when present

9.4% of the dry batch — half of recipes fall between 5% and 12%.

Fired surface of those recipes

Glossy 64% · Semi-glossy 16% · Matte 10% · Satin 10%

Cones where it appears

Share of recipes containing this material that fire to each cone.

Most often mixed with

Materials that appear in the same recipes most often.

Silica70%Whiting43%EPK42%Nepheline syenite31%Bentonite30%Dolomite29%Kaolin26%Gerstley borate23%

Chemistry

Raw formula: ZrSiO₄
Fired formula: ZrO₂·SiO₂
: sold as zirconium silicate; zirconium oxide alone is ZrO2, mol. wt. 123

From Linda Arbuckle's materials table. Mineral formulas are idealized; buy an analysis for the bag you have. Equivalent weight is the weight that supplies one molecule of the fired oxide — the number glaze calculation uses.

What potters should know

Rule of thumb, 1 tin ≈ 1.5 zirconium. Small amounts don't opacify but do lower expansion and deter crazing; above about 10% it hardens the glaze and raises viscosity. Best in glazes high in calcium and low in boron.

Handling and safety

Dry ceramic materials generate respirable silica dust. Use a NIOSH-approved N95 or P100 respirator and adequate ventilation when mixing dry, and wet-clean surfaces.

This information is provided for planning purposes and is derived from publicly available sources including OSHA regulations, NIOSH guidance, and manufacturer safety data sheets. It does not constitute professional safety advice. Consult your material suppliers' SDS documents and applicable local regulations for authoritative safety guidance.

Questions

How much Zircopax do potters use in a glaze?: Across 1,098 published glaze recipes containing it, the typical amount is 9.4% of the dry batch, with half of recipes between 5% and 12%. Colorants and additives sit far lower than fluxes and glass formers; treat these as a range to test around, not a target.
What cone is Zircopax used at?: It appears in recipes across the range; the most common cones among published recipes are cone 6, cone 10, cone 8. Where a material sits depends on the rest of the recipe more than on the material itself.
Is Zircopax safe to use?: It carries no specific hazard flag beyond the general rule for all dry ceramic materials: avoid breathing the dust and read the supplier's SDS.

Related materials

Glaze material	recipes	typical
Tin oxide	1,345	4%

Sources. Usage figures are computed by Claybench over 10,859 glaze recipes compiled from publicly shared community recipe collections (snapshot 2026-02-27) — counts only; no recipe is reproduced, and the figures describe that collection, not every recipe in existence. Material roles and notes are paraphrased from Linda Arbuckle's Ceramic Materials handout unless noted. Hazard notes summarise supplier SDS guidance; read the SDS for the product you buy.

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