A tea dust glaze with increased alumina
A tea dust glaze with increased alumina becomes a tenmoku glaze with oil
spots.
The glaze iron_DG3_PAl is
a descendant of the tea dust glaze seen
here .
The tenmoku glaze iron_DG3_PAl has substantially higher alumina than
satIron_Z1D_G_3 seen above, while
150 deg F an hour to 250 deg F
400 deg F an hour to 2050 deg F
120 deg F an hour to 2250 deg F
60 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 0.27
Al2O3 0.76
SiO2 3.8
molecular percent Silica 65.8%
For comparison the empirical formula of the tea dust glaze:
K2O 0.27
Al2O3 0.61
SiO2 3.8
molecular percent Silica 67.7%
The discrete crystals that grow in satIron_Z1D_G_3 are sufficiently small,
that a slight increase in alumina
The iron that is a component of the crystals in the tea dust glaze
satIron_Z1D_G_3 remains in the
In the more viscous glaze, movement of oxides is slower and crystal growth
size is limited by the amount of movement
I don't think the replacement of a small amount of BaO with MgO had a
significant effect on this glaze.
most of the other oxides in its empirical
formula are virtually identical. The small amount of BaO in satIron_Z1D_G_3
is
replaced by MgO.
Bowl with glaze iron_DG3_PAl
inside
outside
bowl is ~ 4 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 iron_DG_3_PAl :
Na2O 0.27
Li2O 0.29
CaO 0.11
MgO 0.06
Fe2O3 0.22
Empirical Formula satIron_Z1D_G_3 :
Na2O 0.27
Li2O 0.28
CaO 0.11
MgO 0.01
BaO 0.06
Fe2O3 0.21
Remarks
is enough to inhibit their growth
altogether.
glaze matrix in the glaze iron_DG3_PAl,
resulting in a darker nearly black color. The surface microcrystals that
occasionally coalesce to form nascent oil drops are impeded in size by the
viscosity of the higher alumina glaze.
possible before freezing sets in at
the glass transition.