Reproducing an oil spot glazes
firing to cone 10 in oxidation
The Downfire 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.
The glaze mashiko_ZJ_3 is seen here:
glaze composition
Emperical Formula:
K2O 0.04
Na2O 0.17
Li2O 0.13
CaO 0.26
MgO 0.40
Al2O3 .82
SiO2 5.74
For convenience The glaze in the first firing is shown:
a small 3.5 inch diameter bowl
The glaze in the second firing
a plate 9 inches in diameter
Note: This plate has an abstract design consisting of additional distinct
glazes
applied to the bare bisque independant of the background glaze.
Commentary
The glaze application on the inside of the plate is nearly twice as thick as
it was on the small thin conical bowl.
The result is that the oil spots
are larger, and the glaze is drier. The outside of the plate was glazed
thinner
and is nearly identical in appearance to that of the bowl.