Glaze material · Fluxes, feldspars & frits
Talc
Also sold as: magnesium silicate
Magnesium and silica: a secondary flux in glazes and a body flux at low temperatures.
In published recipes
Used in 1,975 of 10,859 glaze recipes (18%)
Typical amount when present
8.1% of the dry batch — half of recipes fall between 5% and 13%.
Fired surface of those recipes
Glossy 58% · Semi-glossy 17% · Satin matte 12% · Satin 12%
Most often mixed with
Materials that appear in the same recipes most often.
Chemistry
- Raw formula
- 3MgO·4SiO2·H2O
- Molecular weight
- 379.3
- Fired formula
- MgO·1.3SiO2
- Equivalent weight
- 126.4
From Linda Arbuckle's materials table. Mineral formulas are idealized; buy an analysis for the bag you have. Equivalent weight is the weight that supplies one molecule of the fired oxide — the number glaze calculation uses.
What potters should know
Reduces crazing and gives smooth, buttery surfaces with magnesium's colour response. Supply has become uncertain over asbestos-contamination concerns; a suggested replacement in glazes is roughly 80% nepheline syenite plus 20% dolomite.
Handling and safety
Some talc deposits have been associated with asbestos-like minerals; buy from a supplier who certifies the source and never breathe the dust.
Dry ceramic materials generate respirable silica dust. Use a NIOSH-approved N95 or P100 respirator and adequate ventilation when mixing dry, and wet-clean surfaces.
This information is provided for planning purposes and is derived from publicly available sources including OSHA regulations, NIOSH guidance, and manufacturer safety data sheets. It does not constitute professional safety advice. Consult your material suppliers' SDS documents and applicable local regulations for authoritative safety guidance.
Questions
- How much Talc do potters use in a glaze?
- Across 1,975 published glaze recipes containing it, the typical amount is 8.1% of the dry batch, with half of recipes between 5% and 13%. Colorants and additives sit far lower than fluxes and glass formers; treat these as a range to test around, not a target.
- What cone is Talc used at?
- It appears in recipes across the range; the most common cones among published recipes are cone 6, cone 10, cone 9. Where a material sits depends on the rest of the recipe more than on the material itself.
- Is Talc safe to use?
- It carries a specific hazard flag: Some talc deposits have been associated with asbestos-like minerals; buy from a supplier who certifies the source and never breathe the dust. Read the supplier's SDS and follow local rules before using it, and never assume a glaze is food-safe without testing.
Related materials
| Glaze material | recipes | typical |
|---|---|---|
| Dolomite | 2,402 | 10% |
| Magnesium carbonate | 384 | 5.5% |
Sources. Usage figures are computed by Claybench over 10,859 glaze recipes compiled from publicly shared community recipe collections (snapshot 2026-02-27) — counts only; no recipe is reproduced, and the figures describe that collection, not every recipe in existence. Material roles and notes are paraphrased from Linda Arbuckle's Ceramic Materials handout unless noted. Hazard notes summarise supplier SDS guidance; read the SDS for the product you buy.
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