Glaze type · Traditions & specialties
Raku
Across 107 published recipes: mostly cone 08 and cone 06, fired in raku and oxidation; Glossy, opaque.
Materials that define it
Share of recipes containing each material, and the typical amount when present. Materials link to their reference pages.
| Material | In recipes | Typical | Half of recipes |
|---|---|---|---|
| Gerstley borate | 56% | 64.5% | 50–76.15% |
| Copper carbonate | 53% | 5% | 3–10% |
| Nepheline syenite | 29% | 19.8% | 14.29–22.22% |
| Silica | 23% | 10% | 6.5–13.93% |
| Bentonite | 21% | 2% | 2–2% |
| EPK | 19% | 6.3% | 4.24–9.9% |
| Bone ash | 16% | 20% | 18.3–25% |
| Borax | 16% | 40% | 17.61–50% |
| Colemanite | 14% | 50% | 26.31–60% |
| Lithium carbonate | 13% | 15.39% | 9.03–28.36% |
| Tin oxide | 13% | 2.31% | 1.3–3% |
| Copper oxide | 12% | 3% | 2–6.65% |
| Zircopax | 11% | 8.65% | 8.01–14.81% |
| Red iron oxide | 11% | 3.25% | 1.9–7.75% |
Typical fired chemistry
Median oxide analysis (weight %) across the recipes that report one, with the interquartile range. Silica and alumina set the melt; the fluxes and colorants make the family.
| Oxide | Median | Half of recipes |
|---|---|---|
| SiO2 | 25.92% | 14.1–41.65% |
| Al2O3 | 4.58% | 2.85–6.37% |
| B2O3 | 17.71% | 11.66–20.52% |
| Na2O | 3.69% | 2.68–5.42% |
| K2O | 0.73% | 0.28–1.4% |
| CaO | 13.87% | 8.43–18.88% |
| MgO | 1.68% | 0.1–2.57% |
| CuO | 2.96% | 1.88–4.79% |
Questions
- What is a Raku glaze?
- In 107 published recipes, Raku glazes are mostly fired to cone 08 and cone 06 in raku and oxidation, with a Glossy, opaque result. The defining materials are Gerstley borate, Copper carbonate, Nepheline syenite, Silica, Bentonite.
- What cone is Raku fired to?
- The most common cones in published recipes are cone 08 and cone 06; the full distribution is on this page. Atmosphere matters as much as cone for this family: raku and oxidation.
- What is the typical chemistry of a Raku glaze?
- Median fired analysis: SiO2 25.92%, Al2O3 4.58%, B2O3 17.71%, Na2O 3.69%, K2O 0.73%, CaO 13.87%. Treat these as the centre of a range, not a target — the same family spans different fluxes and cones.
Sources. Every figure is a statistic computed by Claybench over 10,859 glaze recipes compiled from publicly shared community recipe collections (snapshot 2026-02-27); no recipe is reproduced. Colour-chemistry notes are paraphrased from Linda Arbuckle's Ceramic Materials handout.
Colorant and flux notes touch on materials with handling hazards (barium, cobalt, chrome, manganese, lead in historic recipes). Read each material's page and its supplier SDS before mixing; test any food surface.
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