Glaze type · Surfaces & effects
Crackle
Across 55 published recipes: mostly cone 6 and cone 7, fired in oxidation and reduction; Glossy, translucent.
Cones
Atmosphere
oxidation 66% · reduction 21% · raku 7% · neutral 5%
Surface
Glossy 43% · Semi-glossy 40% · Satin matte 9% · Matte 6% · Satin 3%
Transparency
translucent 47% · opaque 25% · transparent 14% · semi-opaque 14%
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 |
|---|---|---|---|
| Nepheline syenite | 58% | 80% | 44.61–86% |
| Bentonite | 47% | 2% | 2–2% |
| Silica | 46% | 12% | 9.5–22.54% |
| Whiting | 33% | 9% | 5.55–10.08% |
| Talc | 29% | 7.86% | 6.35–8% |
| EPK | 22% | 6.2% | 3.99–9.84% |
| Kaolin | 16% | 11% | 6.9–18.5% |
| Dolomite | 14% | 9.12% | 2.6–16% |
| Custer feldspar | 13% | 43.6% | 28.84–66% |
| Bone ash | 13% | 4% | 2.86–74% |
| Ferro frit 3124 | 13% | 5.77% | 5.77–7.5% |
| Gerstley borate | 13% | 46.51% | 12.5–80% |
| Magnesium carbonate | 13% | 31% | 3.9–41.18% |
| Lithium carbonate | 11% | 6.2% | 2.5–10.42% |
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 | 57.44% | 45.73–60.46% |
| Al2O3 | 15.48% | 10.93–20.32% |
| B2O3 | 1.42% | 0.8–8.06% |
| Na2O | 6.76% | 3.24–8.7% |
| K2O | 3.27% | 1.9–3.97% |
| CaO | 4.44% | 1.64–9.03% |
| MgO | 1.85% | 0.08–2.65% |
What potters should know
Deliberate crazing — a glaze whose expansion is higher than the body's. The same physics as the crazing defect, on purpose.
Questions
- What is a Crackle glaze?
- In 55 published recipes, Crackle glazes are mostly fired to cone 6 and cone 7 in oxidation and reduction, with a Glossy, translucent result. The defining materials are Nepheline syenite, Bentonite, Silica, Whiting, Talc.
- What cone is Crackle fired to?
- The most common cones in published recipes are cone 6 and cone 7; 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 Crackle glaze?
- Median fired analysis: SiO2 57.44%, Al2O3 15.48%, B2O3 1.42%, Na2O 6.76%, K2O 3.27%, CaO 4.44%. 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.