The development of the Snow Glaze
A pot with a background glaze resembling fallen snow was seen here:
That glaze, in a previous firing, while having an interesting surface texture, did not show the opaque inclusions
resembling snow seen in the glaze in the second firing.
In that second firing, there was a related glaze with snow texture.
I show, side by side, the first glaze hankPaper_Z18_0 in the two firings.
I also show, side by side, the two glazes, hankPaper_Z18_0, and hankPaper_Z19_0 in the second firing.
The same firing protocol was used for both firings.
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 cone 10 firing.
K2O 0.14
Al2O3 .44
SiO2 2.7
molecular percent Silica 64 %
K2O 0.14
Al2O3 .43
SiO2 2.6
molecular percent Silica 64 %
The pot with glaze hankPaper_Z18_0 in the second firing has a thicker glaze
application. As the thickness of the application
was not uniform in either firing or on either pot, close examination of the
first pot with almost no snow shows hints
where the glaze is thicker. Similar examination of the the second pot, shows
absence of snow where the glaze is thinner.
The pot with the glaze hankPaper_Z19_0 had a thick glaze application, possibly
with a thinner application it also would not have snow.
Although these glazes are sufficiently similar in composition to make one
question whether they are distinct glazes,
the glaze hankPaper_Z19_0 lacks Lithium and has less Rutile than the glaze
hankPaper_Z18_0. This variance is sufficient
to attribute the differences in glaze performance to composition rather than
chance.
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Empirical Formula background glaze hankPaper_Z18_0 :
Na2O 0.09
Li2O 0.01
CaO 0.40
MgO 0.02
BaO 0.27
SrO 0.07
TiO2 0.1
Empirical Formula design glaze: hankPaper_Z19_0:
Na2O 0.08
CaO 0.42
MgO 0.01
BaO 0.28
SrO 0.07
TiO2 0.05
glaze hankPaper_Z18_0 in two firings
bowls are ~ 6.5 inches in diameter
Left result in first firing and Right result in second firing
glaze hankPaper_Z18_0 and glaze hankPaper_Z19_0, same firing
Left hankPaper_Z18_0 and Right hankPaper_Z19_0
Left bowl is ~ 6.5 inches in diameter, right bowl is ~4 inches in diameter
Full View of pots
bowl glaze hankPaper_Z18_0 in first firing
bowl glaze hankPaper_Z18_0 in second firing
bowl glaze hankPaper_Z19_0
Remarks