Calcia replacing Magnesia in a Saturated Iron glaze
Here we show the result of replacing the MgO in a saturated Iron glaze with CaO.
The empirical formula's of the two glazes are identical except for the replacement of MgO in the first glaze with CaO in the second glaze.
Glazes are fired at cone 6 in an electric kiln.
The kiln is cooled slowly, at a rate of 25 deg F an hour in the temperature interval 1750 deg F to 1650 deg F, with a 1 hour hold at 1650 deg F.
glaze iron_185_0, High MgO, on bowl ~3.5 inches high
glaze iron_185_1 with MgO replaced by CaO on bowl ~3.5 inch high
The first glaze has CaO only as an impurity in other materials.
These are cone 6 glazes, nevertheless, the high MgO glaze is considerably more fused, and is a full gloss glaze.
The high CaO glaze, resulting from replacement of MgO with CaO, is a nearly dry matt.