Effect of Inverted Down-Firing on a high titanium glaze
Inverting the order of the downfire holds transmutes a high titanium glaze.
The rutile
Both Firing 1 and Firing 2 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
The reasoning behind inversion of the order of the downfire holds is discussed
here .
The inlay design is created by adhering a mask and then applying the main
glaze. After drying,
bowl is ~4 inches in diameter
bowl is ~ 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
K2O 0.12
Al2O3 0.60
SiO2 3.28
molecular percent Silica 63.4%
K2O 0.15
Al2O3 0.90
SiO2 3.57
molecular percent Silica 61.8%
Blue streaks visible in second firing bowl are cobalt contamination.
crystal clusters grow unrestrained, morphing a softly translucent
glaze with disjoint crystal clusters
into a white enamel coating.
with a hold at 1700 deg F.
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 hiAlk_Z3P_MAl in Firing 1
inside
outside
Image of the glaze hiAlk_Z3P_MAl in Firing 2
oxidation firings to cone 10 in an electric kiln
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
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Empirical Formula hiAlk_Z3P_MAl:
Na2O 0.51
CaO 0.35
MgO 0.02
P2O5 0.06
TiO2 0.22
Inlay Glaze:
Empirical Formula inlay lis-again:
Na2O 0.49
CaO 0.30
MgO 0.06
Fe2O3 0.22
P2O5 0.08
Remarks