Calico
The glaze shown here cooper_404_1Na_PZn, is stunning... and dunted. It is high
in ZnO, yet many glazes
Replacing some BaO with SrO gives the glaze cooper_404_1Na_PZn_PSr.
Alternatively increasing
Many of the calico family of glazes feature a glossy amber phase out of which
the crystals grow.
It seems that cooper_404_1Na_PZn has greater crystal fraction in the final
melt, which causes it
cooper_404_1Na_Z4E_1 has a pale pink matrix, and steel blue micro-crystals
which have sharp contrast
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 0.32
SiO2 2.37
molecular percent Silica 64.2%
added:
1.5% Nickel Oxide
K2O 0.07
Al2O3 0.32
SiO2 2.38
molecular percent Silica 64.2%
added:
1.5% Nickel Oxide
K2O 0.07
Al2O3 0.33
SiO2 2.74
molecular percent Silica 67.3%
added:
1.5% Nickel Oxide
K2O 0.06
Al2O3 0.33
SiO2 2.83
molecular percent Silica 68%
added:
1.5% Nickel Oxide
are equally high in ZnO and don't dunt. For
comparison we show three of them here.
are three of them.
the silica gives the glaze cooper_404_1Na_PZn_PSi.
Last is the glaze cooper_404_1Na_Z4E_1 which
has lower alkali metals and
higher silica.
This phase is visible in both cooper_404_1Na_PZn_PSr, and
cooper_404_1Na_PZn_PSi,
yet seems not present in the glaze
cooper_404_1Na_PZn.
to have lower thermal expansion, perhaps the cause of
its dunting. Is the lack of the amber fluid phase
the cause of the greater
micro-crystal growth?
with the pink, but are small. The crystal content
of this glaze seems low compared to other of the
calico glazes, perhaps
in this case that accounts for it not dunting.
Image of the glaze cooper_404_1Na_PZn
inside
outside
bowls is ~6 inches in diameter
Image of the glaze cooper_404_1Na_PZn_PSr
inside
outside
Image of the glaze cooper_404_1Na_PZn_PSi
inside
outside
Image of the glaze cooper_404_1Na_Z4E_1
inside
outside
except otherwise noted 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_PZn :
Na2O 0.26
CaO 0.04
MgO 0.01
BaO 0.20
ZnO 0.42
Empirical Formula cooper_404_1Na_PSr :
Na2O 0.17
CaO 0.04
MgO 0.01
BaO 0.20
SrO 0.09
ZnO 0.42
Empirical Formula cooper_404_1Na_PSi :
Na2O 0.26
CaO 0.04
MgO 0.01
BaO 0.20
ZnO 0.42
Empirical Formula cooper_404_1Na_Z4E_1:
Na2O 0.14
CaO 0.03
MgO 0.01
BaO 0.34
ZnO 0.42