Shifting Edges
A descendant of the glaze seen
here .
The glaze shown in this note, iron_Alex_1, is derived from iron_Alex_0.
In its empirical formula,
Several small changes combine to generate something which is seemingly
unrelated to its source. iron_Alex_1
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 0.07
Al2O3 0.53
SiO2 2.97
molecular percent Silica 63.5%
For reference the parent glaze:
K2O 0.08
Al2O3 0.57
SiO2 3.0
molecular percent Silica 63%
iron_Alex_1 with lower alumina, but nearly the same silica has a higher
silica:alumina ratio, which one might
iron_Alex_1 shows its fluidity by the roll of glaze at its foot.
some alkali metals are replaced by CaO, and it has
less alumina.
is a fluid micro-crystalline
matte glaze. The only remaining resemblance to its ancestry would be the
occurrence of
a multiplicity of distinct intertwined, yet cleanly
delineated colors seen on its surface. The sharp boundaries
between the
various colors suggests that there are several distinct micro-crystals on this
surface.
Image of the glaze iron_Alex_1
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_1 :
Na2O 0.33
Li2O 0.12
CaO 0.38
MgO 0.10
Fe2O3 0.15
P2O5 0.02
Empirical Formula iron_Alex_0 :
Na2O 0.37
Li2O 0.14
CaO 0.32
MgO 0.09
Fe2O3 0.15
P2O5 0.03
Remarks
expect to generate a glossier
glaze. Conversely the lower alkali metals would be expected to give a more
matte glaze,
which is what occurred. Lower alkali metals trumped higher
alumina:silica ratio.