Silica and Color
First and second column components of the empirical/seger formula of these two
glazes are nearly identical, only silica
The low silica 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.
This glaze has a waxy texture.
The design is created by adhering a mask and then applying the main
glaze. After drying, the entire pot is
The high silica glaze
This glaze is a glossy light yellow-orange.
The glaze is pale in contrast to the deep colors of the low silica
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 .25
Al2O3 .48
SiO2 3.88
molecular percent Silica 68%
A red glaze, and a yellow-orange glaze which differ in silica
is substantially different.
The higher silica glaze has a higher 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
reds 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_3
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_3 :
Na2O .22
Li2O .23
CaO .15
MgO .15
Fe2O3 .31
P2O5 .04