How much Alumina do potters use in a glaze?

Across 112 published glaze recipes containing it, the typical amount is 8.2% of the dry batch, with half of recipes between 3% and 18.8%. 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 Alumina used at?

It appears in recipes across the range; the most common cones among published recipes are cone 10, cone 5, cone 6. Where a material sits depends on the rest of the recipe more than on the material itself.

Is Alumina 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 · Additives

Alumina

Also sold as: alumina hydrate, calcined alumina

Pure alumina: refractory, it stiffens a melt — and outside the glaze it is the wadding and kiln-wash material.

stiffens the melt (alumina)Contributes: Al₂O₃

In published recipes

Used in 112 of 10,859 glaze recipes (1.0%)

Typical amount when present

8.2% of the dry batch — half of recipes fall between 3% and 18.8%.

Fired surface of those recipes

Matte 43% · Glossy 28% · Semi-matte 16% · Satin matte 14%

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.

Silica44%Kaolin39%Whiting32%Ferro frit 313432%Nepheline syenite27%Bentonite24%Zinc oxide22%Titanium dioxide21%

Chemistry

Raw formula: Al₂O₃
Molecular weight: 102
Fired formula: Al₂O₃
Equivalent weight: 102
: alumina hydrate Al2(OH)6: 156 → Al2O3, eq. wt. 156

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

Rarely a glaze ingredient in quantity; used in wax resist on pot galleries and to keep highly fluxed clays from sticking to each other in firing.

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 Alumina do potters use in a glaze?: Across 112 published glaze recipes containing it, the typical amount is 8.2% of the dry batch, with half of recipes between 3% and 18.8%. 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 Alumina used at?: It appears in recipes across the range; the most common cones among published recipes are cone 10, cone 5, cone 6. Where a material sits depends on the rest of the recipe more than on the material itself.
Is Alumina 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
EPK	4,397	11.7%

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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