Granular Phosphorus
Here is a high phosphorus, high alkali metal glaze, with a non-glossy surface,
and a mottled texture resulting from the uneven distribution
inside of bowl:
Outside of bowl:
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
The glaze with .12 molecular fraction Phosphorus
K2O .15
Al2O3 .52
SiO2 3.2
molecular percent Silica 63.6%
This glaze has a heavily textured dark stony surface with variegated red
orange blooms in regions where phosphate granules are concentrated.
The striking orange-y blooms are the result of a non-uniform distribution of
trisodium phosphate in the glaze.
Another consequence of the uneven distribution of the trisodium phosphate
within the glaze slurry is the stony surface as it
As expected, these crystals are found in satIron_ZG_1P_1 in regions of high
phosphorus concentration.
of the large
TSP (trisodium phosphate) crystals in the glaze slurry.
Glaze satIron_ZG_1P_1
bowl is ~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
Empirical Formula glaze satIron_ZG_1P_1 :
Na2O .4
Li2O .21
CaO .1
MgO .14
Fe2O3 .19
P2O5 .12
Remarks
also causes an uneven
distribution of sodium within the glaze. The TSP carries a goodly quantity of
sodium along
with its phosphate.
In that prior test, satIron_ZG_0 has a full gloss surface as is expected of a
high alkaline metal glaze.
Therefore, the stony surface of satIron_ZG_1P_1 is a surprise given its high
alkali metal content.