Metallic microCrystals
The surface of this glaze is covered in metallic micro crystals.
This glaze has few metallic micro crystals.
It contains less silica.
This glaze also has few metallic micro crystals
This glaze has more CaO and less MgO than satIron_ZG_1O_0
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 .25
Al2O3 .52
SiO2 3.2
molecular percent Silica 64%
K2O .2
Al2O3 .52
SiO2 3
molecular percent Silica 63%
K2O .25
Al2O3 .52
SiO2 3.18
molecular percent Silica 64%
Distinct crystals grow in a glaze and compete for resources. These three
glazes contain the same components in different proportions.
The low silica glaze surface has a somewhat lumpy surface, an indication
of high viscosity.
Movement of materials within this glaze will be slower as a result of its
higher viscosity. This slowed transport favors
The glaze which is lower in MgO is thereby higher in CaO. The MgO may be
important to the crystal growth, alternatively,
The Initial glaze - the starting point for this note: is the Glaze
satIron_ZG_1O_0
Glaze satIron_ZG_1O_1Q_0
Glaze satIron_ZG_1O_1
bowl are ~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
Initial glaze
Empirical Formula satIron_ZG_1O_0 :
Na2O .24
Li2O .24
CaO .17
MgO .1
Fe2O3 .21
P2O5 .05
Glaze with less silica
Empirical Formula glaze satIron_ZG_1O_1Q_0 :
Na2O .3
Li2O .23
CaO .17
MgO .1
Fe2O3 .2
P2O5 .04
Glaze with CaO replacing MgO
Empirical Formula glaze satIron_ZG_1O_1 :
Na2O .24
Li2O .24
CaO .26
MgO .01
Fe2O3 .21
P2O5 .05
Remarks
These glazes are waxy microcrystalline glazes.
What determines
when the metallic micro crystals appear?
Decreasing silica in a glaze can decrease or
increase viscosity of the glaze.
In this case decreased silica increased
the viscosity.
the growth of crystals
from local materials, while retarding the accumulation of distant
particles.
Perhaps this indicates a dependance of the metallic micro
crystals on distant particles.
the additional CaO which
substituted for the MgO provides the opportunity for calcia rich crystals to
form at the expense
of the metallic crystals.