Shifting Edges
Another glaze near
iron_Alex_0 .
Previously we have seen:
iron_Alex_0PSiMAlk
with higher silica and alumina that resulted in denser, but smaller versions of
and
iron_Alex_1 with lower alumina, but also lower alkali metals,
which is a micro-crystalline matte glaze.
The glaze shown in this note, iron_Alex_2, is closest to iron_Alex_1,
having the same alumina and silica
iron_Alex_2 has the acicular crystals in a glossy matrix seen in iron_Alex_0.
bowl is ~ 4 inches in diameter.
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 2310 deg F with a hold of 20 minutes at 2310 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 0.10
Al2O3 0.53
SiO2 2.96
molecular percent Silica 63.6%
For reference the parent glaze:
K2O 0.07
Al2O3 0.53
SiO2 2.97
molecular percent Silica 63.5%
iron_Alex_2 has very nearly the same empirical formula as iron_Alex_1, having
only slightly higher alkali metals,
iron_Alex_2 shows its fluidity by a slight drip of glaze at its foot.
iron_Alex_0's acicular crystals in a glossy matrix;
but higher alkali metals. In
its empirical formula, CaO is replaced by alkali metals.
Image of the glaze iron_Alex_2
inside
outside
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 iron_Alex_2 :
Na2O 0.33
Li2O 0.13
CaO 0.34
MgO 0.10
Fe2O3 0.15
P2O5 0.02
Empirical Formula iron_Alex_1 :
Na2O 0.33
Li2O 0.12
CaO 0.38
MgO 0.10
Fe2O3 0.15
P2O5 0.02
Remarks
and slightly lower CaO. I attribute
the difference in appearance to its higher alkali metals, because previous
tests
that adjusted CaO ratios did not produce significant differences in
glaze appearance..