Phosphorus
cone 10 oxidation
Firing profile
Up Fire profile
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
Down Fire Profile
A half hour hold at 1750 deg F
A three hour hold at 1700 deg F
slow downfire at 25 deg F an hour in the interval 1700 deg F to 1650 deg F
A one hour hold at 1650 deg F
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
We saw the glaze satIron_ZJ_1PPP here:
And this glaze with some Kaolin added here:
Here we see a saturated iron glaze satIron_ZT_0 with almost twice the
phosphorus as the glaze satIron_ZJ_1PPP.
In the respective empirical formulas
P2O5 is .24 vs .13.
The source of the phosphorus is bone ash, so CaO at 0.72 vs. 0.4 also is much
higher in this glaze. Correspondingly
total alkali metal is .27 vs .58.
The shift in background color and its
monochrome hue can be
attributed to its lower alkali metal components.
The uniform color of satIron_ZT_0 is most obvious at the spiral deformation on the inside of the bowl.
Note the clusters of silvery speckles which are nearly dense on the inside of
the bowl, also the deap garnet color of these same speckles
on the outside of
the bowl where the angle of incident light differs.
glaze composition
Emperical Formula satIron_ZJ_1PPP
K2O 0.02
Na2O 0.31
Li2O 0.25
CaO 0.40
MgO 0.02
Al2O3 .49
Fe2O3 .21
SiO2 3.1
P2O5 .13
molecular percent Silica 63 %
Emperical Formula satIron_ZT_0
K2O 0.01
Na2O 0.01
Li2O 0.25
CaO 0.72
MgO 0.01
Al2O3 .41
Fe2O3 .2
SiO2 3.1
P2O5 .24
molecular percent Silica 63 %
The bowls is ~ 3 inches in diameter.
The glaze is shown on the inside and outside
Glaze satIron_ZT_0
inside
outside