How much Red iron oxide do potters use in a glaze?

Across 2,413 published glaze recipes containing it, the typical amount is 4% of the dry batch, with half of recipes between 2% and 9.1%. 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 Red iron oxide used at?

It appears in recipes across the range; the most common cones among published recipes are cone 6, cone 10, cone 9. Where a material sits depends on the rest of the recipe more than on the material itself.

Is Red iron oxide 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 · Colorants

Red iron oxide

Also sold as: iron oxide, ferric oxide, RIO

The everyday iron colorant: tan to brown to red-brown in oxidation, celadon to temmoku in reduction.

colorantContributes: Fe₂O₃

In published recipes

Used in 2,413 of 10,859 glaze recipes (22%)

Typical amount when present

4% of the dry batch — half of recipes fall between 2% and 9.1%.

Fired surface of those recipes

Glossy 61% · Semi-glossy 19% · Matte 11% · Satin 9%

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.

Silica82%Whiting62%EPK39%Bentonite31%Dolomite27%Custer feldspar27%Kaolin26%Talc26%

Chemistry

Raw formula: Fe₂O₃
Fired formula: Fe₂O₃
: ferric

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

Red iron is finer than black. Yellow to olive in high-alkaline glazes; amber in glazes with barium or strontium. In reduction, roughly ½–3% with calcium gives celadons and 10–15% temmoku; 1–6% with calcium phosphate can give blues.

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 Red iron oxide do potters use in a glaze?: Across 2,413 published glaze recipes containing it, the typical amount is 4% of the dry batch, with half of recipes between 2% and 9.1%. 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 Red iron oxide used at?: It appears in recipes across the range; the most common cones among published recipes are cone 6, cone 10, cone 9. Where a material sits depends on the rest of the recipe more than on the material itself.
Is Red iron oxide 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
Black iron oxide	81	2.8%
Yellow iron oxide	119	2%
Rutile	1,518	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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