zinc erratic
Two glazes with calico markings, cooper_404_1Na_Z4A and cooper_404_1Na_Z4A_2,
the markings on the first
The end glazes are mixed yellow, ivory and two shades of aqua, with the
characteristic calico-type
The middle glaze, a different animal, blue and white, teal blue, many shades
of blue, a smooth waxy surface
That dunting crack proves a line is crossed, this glaze has distinctly
different thermal expansion
The two recipes were added, then normalized, so perhaps it's not entirely "in
the middle," yet close! The
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 2310 deg F with a hold of 20 minutes at 2310 deg F
300 deg F an hour to 1850 deg F then a 2 hr hold at 1850 deg F
300 deg F an hour to 1750 deg F then a 1 hr hold at 1750 deg F
300 deg F an hour to 1700 deg F then a 3 hr hold at 1700 deg F
25 deg F an hour to 1650 deg F then a 1 hour hold at 1650 deg F
K2O 0.07
Al2O3 0.31
SiO2 2.34
molecular percent Silica 64%
added:
1.5% Nickel Oxide
K2O 0.07
Al2O3 0.33
SiO2 2.39
molecular percent Silica 64.2%
added:
1.5% Nickel Oxide
K2O 0.07
Al2O3 0.32
SiO2 2.37
molecular percent Silica 64.2%
added:
1.5% Nickel Oxide
rather subdued if the glaze is thin, the second
with low viscosity, sticks to the kiln shelf if thick.
I thought to
average the two, the result is is the glaze cooper_404_1Na_PZn.
sharply defined polygonal regions of the
various colors. Both have that slightly sandpapery surface
texture
created by zinc surface needle crystals.
and a huge dunting crack.
behavior than the end members of the line blend
out of which it originated.
three glazes have very similar empirical formulae,
such a strong jump in properties in nearby glazes
is intriguing.
Image of the glaze cooper_404_1Na_Z4A
inside
outside
Image of the glaze cooper_404_1Na_Z4A_2
inside
outside
Image of the glaze cooper_404_1Na_PZn
inside
outside
bowls are ~3.5 inches in diameter
oxidation firing to cone 10 in an electric kiln
Firing profiles
Up Fire profile cone 10
Down Fire Profile cone 10
Clay body is a grolleg porcelain from Clay Art Center in Tacoma, WA.
glaze compositions
Empirical Formula cooper_404_1Na_Z4A:
Na2O 0.27
CaO 0.04
MgO 0.01
BaO 0.18
ZnO 0.43
Empirical Formula cooper_404_1Na_Z4A_2:
Na2O 0.25
CaO 0.04
MgO 0.01
BaO 0.21
ZnO 0.41
Empirical Formula cooper_404_1Na_PZn :
Na2O 0.26
CaO 0.04
MgO 0.01
BaO 0.20
ZnO 0.42