Glaze material · Fluxes, feldspars & frits
Borax
Also sold as: sodium tetraborate
A soluble source of boron and sodium — a flux that brings bright alkaline colours.
In published recipes
Used in 143 of 10,859 glaze recipes (1.3%)
Typical amount when present
12% of the dry batch — half of recipes fall between 5% and 32%.
Fired surface of those recipes
Glossy 46% · Matte 26% · Semi-glossy 18% · Satin 11%
Most often mixed with
Materials that appear in the same recipes most often.
Chemistry
- Raw formula
- Na2O·2B2O3·10H2O
- Molecular weight
- 382
- Fired formula
- Na2O·2B2O3
- Equivalent weight
- 382
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
Being soluble it migrates in the bucket and on the pot; frits are the stable way to add the same oxides.
Handling and safety
Soluble in water — can migrate to the surface as it dries and irritate skin; handle with gloves and keep out of food-contact glazes unless fritted.
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 Borax do potters use in a glaze?
- Across 143 published glaze recipes containing it, the typical amount is 12% of the dry batch, with half of recipes between 5% and 32%. 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 Borax used at?
- It appears in recipes across the range; the most common cones among published recipes are cone 04, cone 05, cone 06. Where a material sits depends on the rest of the recipe more than on the material itself.
- Is Borax safe to use?
- It carries a specific hazard flag: Soluble in water — can migrate to the surface as it dries and irritate skin; handle with gloves and keep out of food-contact glazes unless fritted. 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 |
|---|---|---|
| Gerstley borate | 1,926 | 14.5% |
| Soda ash | 469 | 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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