Interacting glazes at a vertical interface
Glazes interacting at a vertical interface.
The matrix (i.e. background) glaze and inlay glaze do not overlap before firing.
The matrix glaze is a full gloss with micro-crystalline inclusions as seen in
the image of the mug.
The inlay glaze, iron_Alex_1_1 is a microcrystalline
matte.
The background and inlay glaze differ more in appearance than in composition.
The matrix glaze iron_Alex_0_mashiko
has higher phosphorus than the inlay
glaze iron_Alex_1_1. The two glazes interact so completely that the location
of
the original design mask is entirely obscured. No part of the inlay
glaze remains recognizable on the mug. It is interesting
that
nevertheless there are features seen in the interaction region that are not
seen in either glaze. Note the midnight
black glassy region, and the
scattered bright red micro-crystals.
Several closeups of the interaction region of the two glazes are shown, the
inlay glaze, and for context,
a picture of the pot.
The background glaze is iron_Alex_0_mashiko, the inlay design is glazed with iron_Alex_1_1.
The design is created by adhering a mask and then applying the main
glaze. After drying, the mask is removed
and the open area filled in with a
second glaze, using a bulb syringe with a needle applicator.
Close up Images of the interaction region
Image of the inlay glaze
iron_Alex_1_1
Image of the piece
mug with glaze iron_Alex_0_mashiko and inlay glaze iron_Alex_1_1
mug is ~3.5 inches in high
oxidation firing to cone 10 in an electric kiln
Firing profiles
Up Fire profile
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
Down Fire Profile
300 deg F an hour to 1750 deg F then a half hour hold at 1750 deg F
300 deg F an hour to 1700 deg F then a Three hour hold at 1700 deg F
25 deg F an hour to 1650 deg F then a one hour hold at 1650 deg F
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Background glaze
Empirical Formula iron_Alex_0_mashiko :
K2O 0.05
Na2O 0.23
Li2O 0.19
CaO 0.37
MgO 0.16
Al2O3 0.55
Fe2O3 0.17
SiO2 3.3
P2O5 0.11
molecular percent Silica 64.4%
Inlay Glaze
Empirical Formula iron_Alex_1_1:
K2O 0.09
Na2O 0.26
Li2O 0.09
CaO 0.45
MgO 0.11
Al2O3 0.51
Fe2O3 0.15
SiO2 2.9
P2O5 0.02
molecular percent Silica 63.4%
Remarks
The original inlay, as placed in the kiln, was a simple curve, about
three-eights of an inch thick. All else is the
result of the reaction of
the inlay glaze with the background glaze.