Glaze type · Surfaces & effects
Crater
Across 24 published recipes: mostly cone 6 and cone 8, fired in oxidation and reduction; Stony matte, 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 |
|---|---|---|---|
| Silica | 92% | 11.18% | 9.3–19.75% |
| Silicon carbide | 83% | 2.5% | 1.38–3.5% |
| Titanium dioxide | 63% | 5% | 5–11.29% |
| Kaolin | 50% | 11% | 8.5–12.65% |
| Nepheline syenite | 46% | 60% | 60–60% |
| Bentonite | 33% | 2% | 2–2% |
| EPK | 25% | 17.5% | 12.1–30.75% |
| Ball clay | 25% | 10% | 7.17–11.25% |
| Whiting | 25% | 22.24% | 14.25–24% |
| Lithium carbonate | 21% | 1% | 1–16% |
| Barium carbonate | 21% | 20% | 17.5–29.84% |
| Copper carbonate | 17% | 3.6% | 3–5.55% |
| Strontium carbonate | 17% | 20% | 18.5–20% |
| Potash feldspar | 17% | 45.84% | 41.24–49.93% |
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 | 46.63% | 44.97–54.28% |
| Al2O3 | 12.88% | 11.08–16.44% |
| Na2O | 4.08% | 1.31–5.58% |
| K2O | 2.71% | 2.24–4.89% |
| CaO | 1.58% | 0.28–10.39% |
| TiO2 | 4.52% | 0.44–9.51% |
What potters should know
Craters come from gas released in the melt — silicon carbide is the usual agent.
Related types
Questions
- What is a Crater glaze?
- In 24 published recipes, Crater glazes are mostly fired to cone 6 and cone 8 in oxidation and reduction, with a Stony matte, opaque result. The defining materials are Silica, Silicon carbide, Titanium dioxide, Kaolin, Nepheline syenite.
- What cone is Crater fired to?
- The most common cones in published recipes are cone 6 and cone 8; the full distribution is on this page. Atmosphere matters as much as cone for this family: oxidation and reduction.
- What is the typical chemistry of a Crater glaze?
- Median fired analysis: SiO2 46.63%, Al2O3 12.88%, Na2O 4.08%, K2O 2.71%, CaO 1.58%, TiO2 4.52%. 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.
Claybench checks a glaze against your clay body and cone before it lands on a plan
Recipes, materials, hazards and cone fit — the same reference behind this page, inside the studio planner.