Effect of Inverted Down-Firing
The clusters of surface micro-crystals in an iron-Titanium glaze morphs with
an inversion of the order
The design is created by adhering a mask and then applying the main
glaze. After drying,
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:
This is an 'invert' firing, following the procedures used by the glass ceramic
folk, which is to drop low for neucleation of
bowl is ~ 6 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 0.06
Al2O3 0.56
SiO2 3.67
molecular percent Silica 66%
K2O 0.18
Al2O3 0.64
SiO2 3.54
molecular percent Silica 64.9%
At what temperature do the crystal seeds, i.e. nuclei, form and at what
temperature do they grow?
Centura by Corningware is an example of ceramics that are created by starting
with glass that is
Firing 2, the firing I refer to as the invert firing, follows that
glass-crystal pattern in that it drops
Here, the result is greater variety of colors and textures, a shift in balance
of color, and in the
of the downfire holds in the firing. The
variety of colors and textures increases, while the size of the
clusters
decreases.
the mask is removed and the open area filled in with a
second glaze, using a bulb syringe
with a needle applicator.
crystals, i.e. crystal
seeds, then come back up for the growth of the micro-crystals. In this case,
the downfire
drops with a hold at 1650 degF, then rises back up with a hold at
1850 deg F, then back down with a hold at 1700 deg F.
Image of the glaze hiAlk_satIron in Firing 1
inside
close up
Image of the glaze hiAlk_satIron in Firing 2
inside
close up
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_satIron:
Na2O 0.62
CaO 0.29
MgO 0.03
Fe2O3 0.10
P2O5 0.08
TiO2 0.15
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
With both copper red glazes and iron red
glazes, there are reports of getting the good color by refiring
in a
bisque firing. The effect is to bring the glaze back up to melting
temperature
after it has already cooled and solidified.
transformed by a process of nucleation and growth into a
crystal. In that case, they drop the glass to a low
temperature to form the
nuclei, then raise the temperature to grow the crystals.
low for a hold of several hours,
then comes back up.
size of the resulting crystal clusters.