Plainsman Clays | PETA
Petalite
Petalite is a lithium aluminium silicate, and it supplies lithia to a body or a glaze in an insoluble form. It is used in flameware and ovenware bodies, where it lowers thermal expansion far enough for a pot to take direct heat.
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Petalite is mined and milled as a mineral concentrate. Its main use is lowering thermal expansion. Flameware and ovenware bodies are built around it, and it is also used in glazes to reduce crazing and improve resistance to thermal shock. Lithia is the lightest of the common fluxing oxides, so a given weight of it puts far more flux into a melt than the same weight of a heavier one. On the way up petalite converts to a lower expansion phase, a change that begins around 750°C. Petalite and the phase it becomes are packed almost identically, so the body does not swell as the change happens.
- A lithium aluminium silicate, sold as a milled mineral concentrate
- Supplies lithia in an insoluble form
- Lowers the thermal expansion of a body and of a glaze
- Converts to a lower expansion phase at almost the same density, so the body keeps its shape
