Hyplas 71 Ball Clay
A standard material in Glazecalc's library: its oxide analysis, unity contribution and hazards.
What it is
- Kind
- Clays
- Formula
- SiO₂ 71%, TiO₂ 1.6%, Al₂O₃ 18.5%, Fe₂O₃ 0.8%, CaO 0.1%, MgO 0.3%, K₂O 1.9%, Na₂O 0.3%, LOI 5.5%
- Also called
- Hyplas 71, Hyplas, HP71, Potclays 3407, Potterycrafts P3354, Valentine CB007, Bath Potters Hyplas 71
- Made by
- Sibelco (Devon, UK)
- Sold in
- UK, EU
- Source
- Valentine Clays technical data sheet 'Hyplas 71 Ball Clay' (mean values) (2025-03)
High-silica Devon ball clay with good plasticity, medium strength and low iron; fires ivory buff. A common ball clay in UK glazes and slips.
Oxide analysis and unity formula
Glazecalc has the analysis of Hyplas 71 Ball Clay as weight percent of the raw material. The unity contribution is the moles of each oxide in the amount of Hyplas 71 Ball Clay that holds 1.0 mole of flux, which is how Glazecalc adds it into a recipe's unity formula.
| Oxide | Weight % | Unity contribution |
|---|---|---|
| SiO₂ | 71 | 34.514 |
| TiO₂ | 1.6 | 0.585 |
| Al₂O₃ | 18.5 | 5.299 |
| Fe₂O₃ | 0.8 | 0.146 |
| CaO | 0.1 | 0.052 |
| MgO | 0.3 | 0.217 |
| K₂O | 1.9 | 0.589 |
| Na₂O | 0.3 | 0.141 |
- Equivalent weight
- 2920.73
- Fired weight
- 2760.09
- Loss on ignition
- 5.5%
The equivalent weight is the grams of Hyplas 71 Ball Clay that hold 1.0 mole of flux. The fired weight is what is left of that after firing.
Hazards and safety
Hazards: Fine dust contains respirable crystalline silica; avoid breathing it.
Use it in a recipe
Add Hyplas 71 Ball Clay to a recipe in the Glazecalc calculator to see what it does to a glaze's unity formula.