Glaze type · Surfaces & effects
Crawl / lichen
Across 57 published recipes: mostly cone 6 and cone 5, fired in oxidation and reduction; Matte, opaque.
Cones
Atmosphere
oxidation 71% · reduction 19% · neutral 11%
Surface
Matte 44% · Glossy 22% · Satin 15% · Stony matte 11% · Semi-glossy 7%
Transparency
opaque 98% · semi-opaque 2%
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 |
|---|---|---|---|
| Magnesium carbonate | 63% | 30% | 20.5–33.57% |
| Nepheline syenite | 44% | 55% | 39.5–70% |
| Zinc oxide | 35% | 7.73% | 5–15.88% |
| Silica | 28% | 9.5% | 6.45–14.68% |
| EPK | 26% | 19% | 10.5–20% |
| Gerstley borate | 25% | 20.47% | 12.56–45.16% |
| Ball clay | 16% | 7.5% | 4–19% |
| Whiting | 16% | 7.51% | 5.5–23.57% |
| Ferro frit 3134 | 12% | 10% | 9–16% |
| Zircopax | 12% | 6.7% | 5.4–10% |
| Bone ash | 12% | 77.25% | 26.44–80% |
| Borax | 11% | 3.89% | 3.55–26.7% |
| Copper carbonate | 11% | 4% | 1.95–14.67% |
| Talc | 8.8% | 7.6% | 7.25–14% |
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 | 38.26% | 26.78–45.63% |
| Al2O3 | 12.93% | 7.68–18.13% |
| B2O3 | 3.48% | 2.6–9.25% |
| Na2O | 4.13% | 2.38–5.58% |
| K2O | 2.09% | 0.35–3.19% |
| CaO | 2.58% | 0.48–7.1% |
| MgO | 10.55% | 0.82–15.9% |
| ZnO | 8.18% | 5.2–16.91% |
What potters should know
Deliberate crawling — high surface tension from zinc, magnesium or a very thick coat. Compare the crawling defect.
Related types
Questions
- What is a Crawl / lichen glaze?
- In 57 published recipes, Crawl / lichen glazes are mostly fired to cone 6 and cone 5 in oxidation and reduction, with a Matte, opaque result. The defining materials are Magnesium carbonate, Nepheline syenite, Zinc oxide, Silica, EPK.
- What cone is Crawl / lichen fired to?
- The most common cones in published recipes are cone 6 and cone 5; 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 Crawl / lichen glaze?
- Median fired analysis: SiO2 38.26%, Al2O3 12.93%, B2O3 3.48%, Na2O 4.13%, K2O 2.09%, CaO 2.58%. 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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