Snow Flake continues
Glazes are fired at cone 6 in an electric kiln.
The kiln is cooled slowly, at a rate of 50 deg F an hour in the temperature interval 1850 to 1700.
It is then cooled 25 deg F an hour in the temperature interval 1700 deg F to 1650 deg F.
There is then a 1 hour hold at 1650 deg F.
We last saw snow flake as:
glaze hiAl_4X_2 cylinder bowl ~4 in high
summary seger formula:
total alkali metals .77
alkaline earths equally divided between CaO and MgO
Alumina .66
Silica 3.3
Titania .23
Here we see that same glaze again in a different firing, on a differently shaped pot:
glaze hiAl_4X_2 bowl ~6 inches in diameter
The snow flakes are present - that much is reproducible. The shift in the
ground color from blue to pale yellow is not in itself distressing,
and the
glaze is attractive. But....
This glaze shivered badly on the outside of the pot.
We see two descendants of this glaze:
hiAl_4V_4Y_0
hiAl_4X_2Y_1
glaze hiAl_4V_4Y_0
This glaze is hiAl_4X_2 with a decrease in Alumina and silica.
The silica:alumina ratio is unchanged as are the bases.
We observe the glossy blue ground of hiAl_4X_2, and the dispersion of opaque white and translucent glossy blue regions on the glaze surface.
inside bowl ~5 inches in diameter
outside bowl ~5 inches in diameter
glaze hiAl_4X_2Y_1
This glaze is hiAl_4X_2 with most of the CaO replaced by MgO.
There are no other changes.
The sharp demarcation between matt and gloss regions is strong, the entire glaze
is glossier, the effect of the increase in MgO is a glossier glaze.
inside bowl ~5 inches in diameter
outside bowl ~5 inches in diameter
I now have a range of compositions which give a glossy transparent ground
phase with opaque matt inclusions.
These glazes seem at risk of
shivering.
The glossy region of all of these glazes exhibit what might
be considered
internal pre-shivering cracks.