Glaze material · Colorants
Copper oxide
Also sold as: black copper oxide, red copper oxide
The stronger copper colorant — same colours as the carbonate at lower percentages.
In published recipes
Used in 445 of 10,859 glaze recipes (4.1%)
Typical amount when present
2% of the dry batch — half of recipes fall between 1.2% and 4%.
Fired surface of those recipes
Glossy 53% · Matte 21% · Semi-glossy 16% · Satin matte 10%
Most often mixed with
Materials that appear in the same recipes most often.
Chemistry
- Raw formula
- CuO
- Molecular weight
- 80
- Fired formula
- CuO
- Equivalent weight
- 80
- red copper oxide Cu2O: 143 → CuO, eq. wt. 70.6
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
Black oxide is the common form; red copper oxide does not mix with water. In raku post-firing reduction it gives thin metallic copper surfaces that may re-oxidise over time.
Handling and safety
Copper compounds are toxic raw and can leach from unstable or high-copper glazes; test food surfaces.
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 Copper oxide do potters use in a glaze?
- Across 445 published glaze recipes containing it, the typical amount is 2% of the dry batch, with half of recipes between 1.2% and 4%. 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 Copper oxide used at?
- It appears in recipes across the range; the most common cones among published recipes are cone 6, cone 7, cone 5. Where a material sits depends on the rest of the recipe more than on the material itself.
- Is Copper oxide safe to use?
- It carries a specific hazard flag: Copper compounds are toxic raw and can leach from unstable or high-copper glazes; test food surfaces. Read the supplier's SDS and follow local rules before using it, and never assume a glaze is food-safe without testing.
Related materials
| Glaze material | recipes | typical |
|---|---|---|
| Copper carbonate | 1,779 | 3% |
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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