Crystals in Glaze
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
The cones show this as a hot cone 10 firing.
I wanted to reproduce the marvelous effect of the base glaze flowing through the inlay seen here:
I get the crystals again, with different glazes. The technique is
different as well. I use one glaze as if it were a reactive slip,
draw
with it on the pot. The second glaze is poured over, no masks or wax or
ticklish filling in
a cleaned area abutting a background glaze.
The families to which these two glazes, base layer glaze and overglaze,
are from distant regions of the Land of Glaze.
hanksSatin_ZV_0 is low
in alkali metals and alumina, and high in Calcia and Baria. The overglaze
satIron_ZG_0
is dominated by alkali metals, and correspondingly higher in
Alumina.
I expect divergent glazes will react together
to produce a result distinct from either.
I found this pair of glazes by testing half a dozen glazes under the
glaze satIron_ZG_0. This glaze is related to satIron_ZG_H_0,
for
various technical reasons seemed to me more promising as the overglaze.
The two glazes below ran together, the crystals of the base glaze show as a counterpoint to the streaks created by the runs of the first layer glaze.
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
I show details of the flows on a bowl ~6 inches in diameter. I also show a picture of the bowl.
glaze composition of the two glazes
Emperical Formula satIron_ZG_0:
K2O 0.1
Na2O 0.49
Li2O 0.19
CaO 0.16
MgO 0.06
Al2O3 .6
Fe2O3 .2
SiO2 3.14
P2O5 .04
molecular percent Silica 63 %
Emperical Formula hanksSatin_ZV_0:
K2O 0.12
Na2O 0.04
Li2O 0.00
CaO 0.48
MgO 0.02
BaO 0.34
Al2O3 .38
SiO2 2.56
molecular percent Silica 65 %
The markings on the inside of the deap bowl are a second glaze applied first, prior to the pouring of the primary glaze.
Close up Images of various of the markings
Image of the whole piece
bowl with glaze satIron_ZG_0 poured over glaze hanksSatin_ZV_0