Rice-Straw Ash (藁灰)
A standard material in Glazecalc's library: its oxide analysis, unity contribution and hazards.
What it is
- Kind
- Fluxes
- Status
- Historical
- Formula
- SiO₂ 79.62%, K₂O 10.53%, CaO 2.8%, P₂O₅ 1.61%, MnO 0.71%, MgO 0.89%, Fe₂O₃ 0.26%, Al₂O₃ 0.27%, Na₂O 0.35%, LOI 2.92%
- Also called
- 藁灰, わら灰, warabai, Rice straw ash
- Similar materials
- Synthetic Rice-Straw Ash (合成藁灰)
- Source
- Guzmán A., Delvasto S., Sánchez E., 'Valorization of rice straw waste: an alternative ceramic raw material', Cerâmica 61 (357), 2015, Table II, process D (XRF) (2015)
Historical: potters made their own by burning rice straw, and it is not sold as a standard material. This is one sample, of Colombian rice straw burnt in an outdoor furnace and then heated to 800 °C for 2 hours, not washed. Straw ash varies with the straw, the soil and the burning: in the same study, hotter burning gave more silica and less potash, and Digitalfire's rice straw ash has 77.26% SiO₂ but only 3.29% K₂O. Its 0.59% chlorine and 1.74% sulfur are counted here as lost on firing.
Oxide analysis and unity formula
Glazecalc has the analysis of Rice-Straw Ash (藁灰) as weight percent of the raw material. The unity contribution is the moles of each oxide in the amount of Rice-Straw Ash (藁灰) that holds 1.0 mole of flux, which is how Glazecalc adds it into a recipe's unity formula.
| Oxide | Weight % | Unity contribution |
|---|---|---|
| SiO₂ | 79.62 | 6.644 |
| K₂O | 10.53 | 0.560 |
| CaO | 2.8 | 0.250 |
| P₂O₅ | 1.61 | 0.057 |
| MnO | 0.71 | 0.050 |
| MgO | 0.89 | 0.111 |
| Fe₂O₃ | 0.26 | 0.008 |
| Al₂O₃ | 0.27 | 0.013 |
| Na₂O | 0.35 | 0.028 |
- Equivalent weight
- 501.36
- Fired weight
- 486.72
- Loss on ignition
- 2.92%
The equivalent weight is the grams of Rice-Straw Ash (藁灰) that hold 1.0 mole of flux. The fired weight is what is left of that after firing.
Hazards and safety
Hazards: Contains crystalline silica, and unwashed ash is caustic when wet; wear gloves and avoid breathing the dust.
Use it in a recipe
Add Rice-Straw Ash (藁灰) to a recipe in the Glazecalc calculator to see what it does to a glaze's unity formula.