yet again cobalt colors
Here is a glaze, zincSr_Z3U_1, in three firings; my regular firing, and two
"invert" firings, which drop,
This glaze will be pink only if thin, and the bowls in Firing 2 and Firing 3
were glazed thick on the inside,
All three firings have the same upfire protocol.
Firing 1:
The downfire is my regular down firing, with holds at 1850 degF,
1750 degF, 1700 degF and 1650 degF.
Firing 2:
The downfire drops with a hold at 1650 degF, then rises back up with a hold at
1850 degF, then back down
Firing 3:
The downfire drops with a hold at 1550 degF, then rises to 1650 with a hold,
rises to 1750 with a hold,
The reasoning behind inversion of the order of the downfire holds is discussed
here .
The design is created by adhering a mask and then applying the main
glaze. After drying,
bowls are ~6 inches in diameter.
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 one hour hold at 1650 deg F
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 1650 deg F then a 3 hr hold at 1650 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 1700 deg F then a 2 hr hold at 1700 deg F
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 1550 deg F then a 1 hr hold at 1550 deg F
300 deg F an hour to 1650 deg F then a 1 hr hold at 1650 deg F
400 deg F an hour to 1750 deg F then a 2 hr hold at 1750 deg F
400 deg F an hour to 1900 deg F then a 3 hr hold at 1900 deg F
K2O 0.13
Al2O3 0.53
SiO2 2.78
molecular percent Silica 64.51%
Added:
2.5% Cobalt Carbonate
K2O 0.18
Al2O3 0.64
SiO2 3.54
molecular percent Silica 64.9%
then come back up.
and thinner on the outside. For this
reason, I show the bottom of these bowls.
with a hold at 1700 deg F.
and finally rises to 1900 degF with a hold,
and that's it.
the mask is removed and the open area filled in with a
second glaze, using a bulb syringe
with a needle applicator.
Image of the glaze zincSr_Z3U_1 in Firing 1
Image of the glaze zincSr_Z3U_1 in Firing 2
inside
outside
Image of the glaze zincSr_Z3U_1 in Firing 3
inside
outside
oxidation firing to cone 10 in an electric kiln
Firing profiles
Firing 1 profile
Up Fire profile cone 10
Down Fire Profile cone 10
Firing 2 profile
Up Fire profile cone 10
Down Fire Profile cone 10
Firing 3 profile
Up Fire profile cone 10
Down Fire Profile cone 10
Clay body is a grolleg porcelain from Clay Art Center in Tacoma, WA.
glaze composition
Empirical Formula zincSr_Z3U_1:
Na2O 0.34
CaO 0.02
MgO 0.20
SrO 0.14
ZnO 0.17
Inlay Glaze:
Empirical Formula inlay hiAlk_Z3P_Z3V_0:
Na2O 0.41
CaO 0.31
MgO 0.10
P2O5 0.07
TiO2 0.21