Copper Red Electric Firing
I show two copper red glazes, fired in an electric Kiln. The two glazes
differ only in the amount of silica each contains,
as shown in the
Empirical Formula.
cone 10 oxidation
The Firing profile
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 2300 deg F
20 minute hold at 2300 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.
high silica glaze
K2O .18
Al2O3 .37
SiO2 3
molecular percent Silica 68%
add:
Copper Carbonate 0.5%
low silica glaze
K2O .18
Al2O3 .37
SiO2 2.5
molecular percent Silica 63%
add:
Copper Carbonate 0.5%
high silica glaze
low silica glaze
Note that the low silica glaze shows little copper red, and is otherwise a
pale turquoise. I don't know if this is an artifact of
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Empirical Formula glaze cu-red-Z1N-0 :
Na2O .18
Li2O .15
CaO .24
MgO .01
SrO .20
ZnO .04
SnO2 .04
Silicon Carbide 1%
Empirical Formula glaze cu-red-Z1N-1 :
Na2O .18
Li2O .15
CaO .24
MgO .01
SrO .20
ZnO .04
SnO2 .04
Silicon Carbide 1%
glaze cu-red-Z1N-0
bowl is ~4 inches in diameter
glaze cu-red-Z1N-1
bowl is ~ 4 inches in diameter
Remarks
firing local copper
red glazes in an electric kiln.