- Alkaline earth flux
- Melts at 4658°F
- Begins fluxing at 2012°F
- Produces glazes with strength, hardness, durability, and resistance to scratching and acids
- Most widely used and dependable flux above 2012°F
- Very stable melter
- helps reduce warping
- Large amounts (>30%), creates rivulets in glaze
- slow cooling will produce calcium mattes
- Has moderate effect on color, except in large amounts where it may have bleaching effect on iron oxide (basis for delicate celadon glazes)
- Assists in color of temmoku and kaki/tomato reds
- Medium viscosity
- High surface tension
- igh to intermediate expansion and contraction rate
- Material isn’t volatile at ceramic temps
- Soluble sources of calcium oxide are Gerstley borate and its substitutes, colemanite, ulexite, bone ash, TCP (tri-calcium phosphate), and wood ash
- Insoluble sources are whiting (limestone), wollastonite, dolomite, some feldspars and most Frits (slightly soluble)