A source of calcium oxide – a ubiquitous and very useful glaze flux. Though highly refractory (m.p.= 2570º C), calcia fluxes actively above 1100º C in combination with other oxides. It stabilizes and improves acid and craze resistance in high alkali glazes and is essential in the development of certain glaze colours.

For more information on calcium carbonate, see the Digitalfire.com Reference Library of ceramic materials.