copper aqua purple

Firing profiles

Up Fire profile

150 deg F an hour to 250 deg F

400 deg F an hour to 1800 deg F

300 deg F an hour to 2050 deg F

120 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F

Down Fire Profile

300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F

300 deg F an hour to 1700 deg F then a Three hour hold at 1700 deg F

25 deg F an hour to 1650 deg F then a one hour hold at 1650 deg F

Clay body is a grolleg porcelain from Tacoma Clay Art Center.

Empirical Formula glaze alexanderBowl_Z15_0 :

The glaze with added .5% copper carbonate, 2% tin oxide, and 1% silicon carbide.

K2O        .08
Na2O        .05
CaO        .7
MgO        .17

Al2O3        .48

SiO2        2.65

molecular percent Silica 64%

Remarks

This is a non-traditional formulation for a copper red glaze, it is an exploration.

I am fascinated by varigated, multi-colored glazes, which the usual glossy copper red isn't. Then too I hadn't any success
producing such a glaze with local reduction. Yet copper with its multiple oxide states is fascinating.

Here I push the composition of the base glaze in a direction that I hoped would produce a more varied result.

Slow diffusion of oxides within a glaze works against a uniform melt. Because this promotes phase separation resulting in multi-textured,
multi-colored results, I made choices that would slow oxygen movement and reoxidation. With lower silica and higher alumina than
the usual formulation for a copper red glaze, I expected that oxygen movement within the glaze would be slower. With local reduction
via silicon carbide as a reducing agent, perhaps the result would be slower reoxidation. The result was this semi-matte aqua and purple glaze.