Synthetic Wood Ash (合成土灰)
A standard material in Glazecalc's library: its oxide analysis, unity contribution and hazards.
What it is
- Kind
- Fluxes
- Formula
- SiO₂ 17.34%, Al₂O₃ 3.45%, Fe₂O₃ 0.33%, CaO 36.09%, MgO 5.88%, Na₂O 0.02%, K₂O 0.15%, LOI 36.74%
- Also called
- 合成土灰, gōsei dobai, Synthetic dobai
- Sold in
- JP
- Source
- 佐賀県陶磁器原料株式会社 (Arita): 釉薬原料の化学分析表, the supplier's typical analysis of what it sells (undated; read 2026-11-04). Second analysis: 吉田博和ほか「笠間焼の新素地・新釉薬の開発」, 茨城県工業技術センター研究報告 43 (2014), 表6
A typical analysis from one supplier in Arita: check it against your own supplier's. A synthetic stand-in for 土灰, the mixed wood ash of Japanese ash glazes; it is not real ash, which varies a great deal. The supplier's figures add up to 96.45%, so the 3.55% they leave out is counted here as lost on firing, with its LOI of 33.19%. A 2014 analysis by the Ibaraki industrial technology centre of another 合成土灰 was much the same: SiO₂ 18.2%, CaO 33.6%, MgO 8.1%, LOI 33.8%.
Oxide analysis and unity formula
Glazecalc has the analysis of Synthetic Wood Ash (合成土灰) as weight percent of the raw material. The unity contribution is the moles of each oxide in the amount of Synthetic Wood Ash (合成土灰) that holds 1.0 mole of flux, which is how Glazecalc adds it into a recipe's unity formula.
| Oxide | Weight % | Unity contribution |
|---|---|---|
| SiO₂ | 17.34 | 0.365 |
| Al₂O₃ | 3.45 | 0.043 |
| Fe₂O₃ | 0.33 | 0.003 |
| CaO | 36.09 | 0.813 |
| MgO | 5.88 | 0.184 |
| Na₂O | 0.02 | 0.000 |
| K₂O | 0.15 | 0.002 |
- Equivalent weight
- 126.36
- Fired weight
- 79.94
- Loss on ignition
- 36.74%
The equivalent weight is the grams of Synthetic Wood Ash (合成土灰) that hold 1.0 mole of flux. The fired weight is what is left of that after firing.
Hazards and safety
Hazards: Avoid breathing the dust.
Use it in a recipe
Add Synthetic Wood Ash (合成土灰) to a recipe in the Glazecalc calculator to see what it does to a glaze's unity formula.