Reactions at the interface between two glazes
The interaction at the interface of adjacent glazes.
Several closeups of the interaction region of the two glazes are shown and,
for context, a picture of the pot.
The background glaze is satIron_ZG_Ip7_5, the foreground design is
glazed with alexanderBowl_0_Z1Y.
The design is created by adhering a mask and then applying the main
glaze. After drying, the entire pot is coated in wax,
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 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
K2O .07
Al2O3 .71
SiO2 3.13
molecular percent Silica 63%
K2O .09
Al2O3 .43
SiO2 2.7
molecular percent Silica 65%
The background glaze, and inlay glaze belong to different glaze families. The
background is a high alumina glaze,
Analogous to the spread of dye poured into water, the components move from
high to low concentration across the inlay boundary.
The contrasting composition of the two glazes creates an interaction region
that covers nearly all of the original design
then the mask is removed
and the open area filled in with a second glaze.
Close up Images of the interaction region
Image of the piece
bowl with glaze satIron_ZG_Ip7_5 and inlay alexanderBowl_0_Z1Y
bowl is ~10 inches in diameter
oxidation firing to cone 10 in an electric kiln
Firing profiles
Up Fire profile
Down Fire Profile
Clay body is a grolleg porcelain from Tacoma Clay Art Center.
glaze compositions
Background glaze
Empirical Formula satIron_ZG_Ip7_5 :
Na2O .44
Li2O .2
CaO .12
MgO .17
Fe2O3 .1
P2O5 0.04
Inlay Glaze
alexanderBowl_0_Z1Y :
Na2O .05
CaO .70
MgO .16
Remarks
high in alkali metals, containing both
iron and phosphorus; the inlay glaze is a high in calcia. The high
viscosity
of the inlay glaze is a consequence of its low alkali metal
content.
The resulting cross
diffusion; the movement of the alkaline earths from inlay into background, and
the alkali metals
from background into inlay, creates a design which is only
suggested by the original mask.
in addition to an even larger
region of the background glaze.