Copper Red

My first ever copper red in an electric kiln. More green than red, for all of that a good red, and no volcanic unprocessed silicon carbide.

A proof of concept, a good beginning.

The local reduction is produced by the inclusion of 1 % 1000 mesh silicon carbide in the glaze recipe.

These glazes, as all my glazes, are mixed with CMC gum which aids in maintaining the silicon carbide in suspension.

cone 10 oxidation

Firing profile

Up Fire profile

150 deg F an hour to 250 deg F

400 deg F an hour to 2050 deg F

120 deg F an hour to 2250 deg F

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

Down Fire Profile

A half hour hold at 1750 deg F

A three hour hold at 1700 deg F

slow downfire at 25 deg F an hour in the interval 1700 deg F to 1650 deg F

A one hour hold at 1650 deg F

The cones show this as a cone 10 firing.

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

glaze compositions

Empirical Formula glaze paulStubbs_0 :

K2O        .09
Na2O        .25
CaO        .57
MgO        .01
ZnO        .08

Al2O3        .4
B2O3        .09

SiO2       3.44
SnO2       0.02

molecular percent Silica 69 %

This glaze is given as copr_9 in Michael Bailey's book Oriental Glazes

I added ~1 % Zinc Oxide, 1 % Tin Oxide, 1 % silicon Carbide and 1 % Copper Carbonate

Empirical Formula glaze baggs_Littlefield :

K2O        .29
Na2O        .28
CaO        .37
MgO        .01
ZnO        .05

Al2O3        .58
B2O3        .38

SiO2        3.8
SnO2        0.03

molecular percent Silica 66 %

This glaze is given as an empirical formula in Sanders "Glazes for Special Effects".

I added ~1 % Zinc Oxide, 1 % Tin Oxide, 1 % silicon Carbide and 1 % Copper Carbonate

bowls are ~ 4 inches in diameter

glaze paulStubbs_0

full view

glaze baggs_Littlefield

full view

inside of bowl

full view

outside of bowl

Remarks

These glazes were advertised as cone 9/10, this firing was a hot cone 10. The colorless part of these pots is loss of color to vaporization of the copper.
This is classic overfired copper red glaze.

To compound overfired, the glazes were not applied sufficiently thickly.

The firing profile is my current one, there were other glazes in this firing that required the slow downfire,
which I expected would be irrelevant to the occurance of the copper red color.

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