Glaze type · Iron glazes
Oil spot
Across 66 published recipes: mostly cone 6 and cone 10, fired in oxidation and reduction; 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 |
|---|---|---|---|
| Silica | 83% | 24.2% | 13.33–25% |
| Red iron oxide | 73% | 8% | 7–10% |
| EPK | 49% | 5% | 5–11.25% |
| Whiting | 47% | 5.71% | 4.4–10.5% |
| Talc | 35% | 7.8% | 6–10% |
| Cobalt carbonate | 26% | 4% | 2–4% |
| Custer feldspar | 26% | 46.39% | 24.55–69.5% |
| Kaolin | 24% | 9.35% | 5.67–17.47% |
| Zircopax | 21% | 10% | 10–10% |
| Potash feldspar | 21% | 40% | 22.75–56.5% |
| G-200 feldspar | 21% | 30% | 30–30% |
| Ferro frit 3134 | 17% | 18.3% | 4.9–30% |
| Dolomite | 15% | 5% | 4.7–6.16% |
| Wollastonite | 11% | 6.1% | 5.5–10% |
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 | 57.8% | 54.35–60.45% |
| Al2O3 | 11.43% | 8.58–13.17% |
| B2O3 | 3.58% | 1.32–7.19% |
| Na2O | 2.77% | 1.68–3.97% |
| K2O | 3.26% | 2.62–4.68% |
| CaO | 4.86% | 3.37–5.85% |
| MgO | 1.27% | 0.35–2.52% |
| Fe2O3 | 6.85% | 5.33–8.34% |
| CoO | 1.72% | 1.12–2.42% |
Related types
Questions
- What is a Oil spot glaze?
- In 66 published recipes, Oil spot glazes are mostly fired to cone 6 and cone 10 in oxidation and reduction, with a Glossy, opaque result. The defining materials are Silica, Red iron oxide, EPK, Whiting, Talc.
- What cone is Oil spot fired to?
- The most common cones in published recipes are cone 6 and cone 10; 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 Oil spot glaze?
- Median fired analysis: SiO2 57.8%, Al2O3 11.43%, B2O3 3.58%, Na2O 2.77%, K2O 3.26%, CaO 4.86%. 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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