more cobalt colors
The glaze, zincSr_Z3W_0 is a descendants of zincSr_Z3S_0
Prior descendants of zincSr_Z3S_0 are
The appearance of this glazes is subtly transformed by an inversion of the
order of the downfire holds
All five 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 deg F, then back down
Firing 3:
The downfire drops with a hold at 1550 deg F, then rises back up with a hold
at 1650 degF, then a hold at
Firing 4:
The downfire drops with a hold at 1650 degF, then rises back up with a hold at
1850 DegF, drops with a hold
Firing 5:
The firing drops with a hold at 1650 degF, rises back up with a hold at 1900
degF, drops with a hold at
Firing 6:
The firing drops with a hold at 1650 degF, rises back up with a hold at 1850
degF, drops with a hold at
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,
The first five bowls are ~6 inches in diameter, the last is ~9.5 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
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
400 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
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
400 deg F an hour to 1900 deg F then a 3 hr hold at 1900 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
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
400 deg F an hour to 1850 deg F then a 3 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
K2O 0.19
Al2O3 0.53
SiO2 3.08
molecular percent Silica 66.8%
Added:
2.5% Cobalt Carbonate
K2O 0.18
Al2O3 0.64
SiO2 3.54
molecular percent Silica 64.9%
My only reliable conclusion - any substantial change in the ordering or
length of the holds has an effect.
There were two firings with a hold at 1900 degF, Firings-3 and Firing-5, both
with three hour holds. The Firing-3
The two firings, Firing-4 and Firing-6 differ only in the length of the hold
at 1850 degF. The result in
shown here .
shown here .
in the firing. I show this glazes in the six
firings: Firing 1, and Firing 2, Firing 3, Firing 4, Firing 5 and Firing 6.
with a hold at 1700 deg F.
1750 degF, then finally a hold at 1900 degF.
at 1750 degF, then finally a hold at 1700
degF.
1750 degF, then finally a hold at 1700 degF.
1750 degF, then finally a hold at 1700 degF.
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_Z3W_0 in Firing 1
Image of the glaze zincSr_Z3W_0 in Firing 2
Image of the glaze zincSr_Z3W_0 in Firing 3
Image of the glaze zincSr_Z3W_0 in Firing 4
Image of the glaze zincSr_Z3W_0 in Firing 5
Image of the glaze zincSr_Z3W_0 in Firing 6
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
Firing 4 profile
Up Fire profile cone 10
Down Fire Profile cone 10
Firing 5 profile
Up Fire profile cone 10
Down Fire Profile cone 10
Firing 6 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_Z3W_0:
Na2O 0.28
CaO 0.02
MgO 0.19
SrO 0.14
ZnO 0.18
Inlay Glaze:
Empirical Formula inlay hiAlk_Z3P_Z3V_0:
Na2O 0.41
CaO 0.31
MgO 0.10
P2O5 0.07
TiO2 0.21
Remarks
ends with the hold at 1900 degF, the
Firing-5 has holds below. The result in Firing-3 seems more dramatic,
perhaps the lower holds erased some of that.
Firing-6 shows more pink and a paler blue.
Can that really have been the result of a longer hold at 1850 degF? It
is
possible that a different geometry for the bowl, and a slightly larger
size resulted in a different
glaze thickness. There were several other
cobalt glazes fired in both Firing-4 and Firing-6, all showed a
consistent shift in the balance between pink and blue.