EPK Kaolin
A standard material in Glazecalc's library: its oxide analysis, unity contribution and hazards.
What it is
- Kind
- Clays
- Status
- Hard to get since 2025
- Formula
- SiO₂ 45.7%, Al₂O₃ 37.4%, Fe₂O₃ 0.79%, TiO₂ 0.37%, P₂O₅ 0.24%, K₂O 0.33%, Na₂O 0.06%, CaO 0.18%, MgO 0.1%, LOI 13.9%
- Also called
- EPK, Edgar Plastic Kaolin, EP Kaolin, Edgar Clay, Kaolin (EPK)
- Made by
- Edgar Minerals, Inc. (Edgar/Hawthorne, Florida); marketed by Imerys when this data sheet was issued
- Sold in
- US, AU
- Similar materials
- Wilco UPF Kaolin , Tile #6 Kaolin , Grolleg China Clay
- Source
- Imerys data sheet 'EPK Kaolin', Second Edition, June 2011 (Laguna Clay distributor copy) (2011-06)
A water-washed secondary kaolin from Edgar, Florida, long the standard US glaze kaolin because it suspends glazes well and fires white. Supply stopped around 2023 to 2025 and US suppliers now recommend Wilco UPF Georgia kaolin in its place.
Oxide analysis and unity formula
Glazecalc has the analysis of EPK Kaolin as weight percent of the raw material. The unity contribution is the moles of each oxide in the amount of EPK Kaolin that holds 1.0 mole of flux, which is how Glazecalc adds it into a recipe's unity formula.
| Oxide | Weight % | Unity contribution |
|---|---|---|
| SiO₂ | 45.7 | 74.846 |
| Al₂O₃ | 37.4 | 36.094 |
| Fe₂O₃ | 0.79 | 0.487 |
| TiO₂ | 0.37 | 0.456 |
| P₂O₅ | 0.24 | 0.166 |
| K₂O | 0.33 | 0.345 |
| Na₂O | 0.06 | 0.095 |
| CaO | 0.18 | 0.316 |
| MgO | 0.1 | 0.244 |
- Equivalent weight
- 9840.14
- Fired weight
- 8472.36
- Loss on ignition
- 13.9%
The equivalent weight is the grams of EPK Kaolin 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 (quartz); do not breathe the dust.
Use it in a recipe
Add EPK Kaolin to a recipe in the Glazecalc calculator to see what it does to a glaze's unity formula.