Alumina and Color
First and third column components of the empirical/seger formula of these two
glazes are nearly identical, only alumina
The low alumina glaze
This glaze shows a mix of colors. The inside of the bowl which has a heavier
glaze application shows mostly reds, pinks and black.
The dominant colors are dark, dark red, dark orange, and black.
The design is created by adhering a mask and then applying the main
glaze. After drying, the entire pot is
The high alumina glaze
This glaze is a light yellow-tan with a sprinkling of red. The red markings
form bands where the glaze is thick.
The dominant colors are pale in contrast to the colors of the low alumina
glaze above.
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 with a hold of 20 minutes at 2300 deg F
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
K2O .24
Al2O3 .47
SiO2 3.2
molecular percent Silica 63%
K2O .23
Al2O3 .52
SiO2 3.1
molecular percent Silica 62%
A red glaze, and a speckled tan glaze which differ in alumina
is substantially different.
The higher alumina glaze has a lower silica:alumina ratio.
Glaze satIron_ZG_1O_1Q_1PFe
The thinner sections
of the outside are dominated by yellows, oranges and black, though even there,
darker
red's are visible.
bowl is ~5 inches in diameter
coated in wax, then the mask is
removed and the open area filled in with a second glaze.
Glaze satIron_ZG_1O1Q1_2
bowl is ~3 inches in diameter
oxidation firing to cone 10 in an electric kiln
Firing profiles
Up Fire profile
Down Fire Profile
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Empirical Formula Glaze satIron_ZG_1O_1Q_1PFe
Na2O .22
Li2O .24
CaO .16
MgO .14
Fe2O3 .3
P2O5 0.04
Empirical Formula glaze satIron_ZG_1O1Q1_2 :
Na2O .21
Li2O .25
CaO .17
MgO .14
Fe2O3 .3
P2O5 .04