Plainsman Clays | ALCA
Alumina Calcined
Calcined alumina is aluminum oxide that has already been fired, so nothing in it burns off or shrinks in the kiln. It is used in kiln shelf and batt washes, as a placing powder under work that might stick, and as a way of adding alumina to a glaze.
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Calcined alumina has been heated until bound water has evaporated, and it has settled into its stable form. It will not shrink or give off gas, and it stays solid to around 2070°C (3760°F), far above anything a pottery kiln reaches. That makes it useful anywhere ware meets shelf. It is applied onto batt and shelves as a wash. It is dusted under work that tends to stick, and kiln shelves and furniture are made from it. In a glaze, it adds alumina without the silica that comes with clay or the flux that comes with feldspar. Most of the alumina in a glaze already comes from those two, so calcined alumina is usually a small deliberate addition, and it dissolves into the melt more slowly than either.
- Aluminum oxide, calcined
- Stays solid to around 2070°C (3760°F)
- Will not shrink or give off gas in the kiln
- Used on batts and shelves as washes and as a placing powder
- Adds alumina to a glaze without silica or flux
