Near Neighbor Glazes
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 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.
I show three variants of the iron red glaze tomatoRed_0.
composition of the glazes
Emperical Formula tomatoRed_0:
K2O 0.14
Na2O 0.08
Li2O 0
CaO 0.56
MgO 0.22
Al2O3 .32
Fe2O3 .24
SiO2 2.9
P2O5 .11
molecular percent Silica 64 %
Emperical Formula tomatoRed_Z15_0:
K2O 0.15
Na2O 0.08
Li2O 0
CaO 0.55
MgO 0.22
Al2O3 .33
Fe2O3 .24
SiO2 2.96
P2O5 .18
molecular percent Silica 63 %
Emperical Formula tomatoRed_Z15_1:
K2O 0.14
Na2O 0.08
Li2O 0.00
CaO 0.56
MgO 0.22
Al2O3 .38
Fe2O3 .23
SiO2 2.85
P2O5 .11
molecular percent Silica 62 %
Emperical Formula tomatoRed_Z15_2:
K2O 0.18
Na2O 0.12
Li2O 0.00
CaO 0.48
MgO 0.22
Al2O3 .39
Fe2O3 .23
SiO2 2.9
P2O5 .11
molecular percent Silica 63 %
The bowls are ~3.5 inches in diameter.
Compare with tomatoRed_0
| glaze | primary difference from tomatoRed_0 |
|---|---|
| tomatoRed_Z15_0 | higher phosphorus |
| tomatoRed_Z15_1 | higher Alumina |
| tomatorRed_Z15_2 | higher Alumina and higher Alkali metals |
Conclusions
We see below in the images that:
More phosphorus in tomatoRed_Z15_0 shifted the glaze color to a mustard like yellow brown.
Higher Alumina in tomatoRed_Z15_1 shifted the glaze color to a redish brown.
Higher Alumina together with higher alkali in metals tomatoRed_Z15_2 morphed
the glaze into a a varigated mixed green brown, with dark spots.
No
longer an iron red, yet an interesting saturated iron glaze.
Note that tomatoRed_Z15_2 is tomatoRed_Z15_1 with higher alkali metals, the
transformation in appearance is the result of the
shift in the bases.
Images
The original glaze, from which the other glazes were derived:
tomatoRed_0
tomatoRed_Z15_0
tomatoRed_Z15_1
tomatoRed_Z15_2