Reactions between Two Glazes
cone 10 oxidation
Firing profile
Up Fire profile
150 deg F an hour to 250 deg F
400 deg F an hour to 2050 deg F
120 deg F an hour to 2250 deg F
60 deg F an hour to 2310 deg F with a hold of 20 minutes at 2310 deg F
Down Fire Profile
A half hour hold at 1750 deg F
A three hour hold at 1700 deg F
slow downfire at 25 deg F an hour in the interval 1700 deg F to 1650 deg F
A one hour hold at 1650 deg F
The cones show this as a hot cone 10 firing.
I wanted to reproduce the marvelous effect of the base glaze flowing through the inlay seen here:
The effect in that firing was the result of an exageratedly long firing between cone 5 and cone 10, resulting in a cone 11 firing. The next step for me, which was shown here:
was to alter the glazes, with the intent to get a flow at cone 10.
I modified only the inlay glaze, making it more fusible.
Interesting but not as exciting as the initial result.
Here I make the base glaze more fusible using the original inlay glaze.
The two glazes again ran together at the interface, with a pattern that is reminiscent of that achieved with a more fluid inlay and unmodified background glaze.
It would seem that rendering either of the two abutting glazes more fusible
results in greater interaction at the interface
Neither of these
approaches will create the 'waterfall' look seen in the original 'crystals',
which was the result of a higher firing.
Yet again the result was an interaction only at the interface, and not, as
desired, a transformation of the entire inlay.
The crystals of the
background glaze and its coloration give a counterpoint to the patterns
formed at the interface to the inlay.
Next I will use both the original background glaze, and the original
inlay glaze, the difference, that it will
no longer be used as an
inlay, rather as if it were a decorative reactive slip. That is, I shall do
a design on the bisque with
using the 'inlay' glaze, then pour the
background glaze over the entire pot, including the design.
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
I show details of the flows on a bowl ~6 inches in diameter. I also show a picture of the bowl.
glaze composition of the two glazes
Emperical Formula satIron_ZG_H_0_Z14:
K2O 0.07
Na2O 0.45
Li2O 0.27
CaO 0.16
MgO 0.05
Al2O3 .39
Fe2O3 .2
SiO2 2.55
P2O5 .046
molecular percent Silica 61 %
Emperical Formula candaceBlackB:
K2O 0.32
Na2O 0.15
Li2O 0.00
CaO 0.39
MgO 0.14
Al2O3 .62
Fe2O3 .24
SiO2 5.36
molecular percent Silica 74 %
Note: CandaceBlackB has some cobalt added
The markings on the inside of the deep bowl are a second glaze inlay. The
glaze is filled in to an area that had been masked prior to
the pouring
of first layer of glaze. It was then waxed with an emulsion wax prior to
stripping the mask.
Close up Images of various of the markings
Image of the whole piece
bowl with glaze satIron_ZG_H_0_Z14 and glaze inlay CandaceBlackB