Migrating disparate abutting glazes
The interface of adjacent glazes from distinct glaze families. The matrix
glaze and inlay glaze overlap
The flowing of the matrix glaze, together with cross diffusion between the two
glazes, and crystal growth
The matrix glaze is a high iron glaze that is high in alkali metals and alumina, yet
relatively
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 same background and foreground glaze, with a substantially thinner
application of background glaze:
Greater glaze thickness resulted in more and larger crystal formation in the
matrix glaze.
The design is created by adhering a mask and then applying the main
glaze. After drying, the mask is removed
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%
Added:
1% Cobalt Carbonate
.67% Copper Carbonate
The background glaze is an immensely fluid glaze; it might be seen as a
celadon with high iron and low silica.
As sugar poured into tea spreads by diffusion into the entire cup, the higher
concentration of CaO
Most of the increase in area covered by the inlay is attributable to crystal
growth in the matrix (background) glaze.
The mask for the inlay is a simple wiggly line. After firing, a large part
of the area encircled by
by no more than an eighth of an inch before
firing, with no overlap whatever for large parts of the design.
The original
mask for the inlay was a wiggly curved line that enclosed an ovoid. A
scribble,
and nowhere more than half an inch across.
in both glazes, nearly filled the entire region
delimited by the individual lines of the masks.
low in silica, with a silica alumina ratio of 4.4. The inlay glaze
by contrast, is high in alkaline earths,
lower in alumina.
and the open area filled in with a
second glaze, using a bulb syringe.
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 ~9 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
Micro-crystals appear in this
glaze if applied thickly. Its low silica encourages phase separation in the
glaze.
The migration of additional CaO and MgO from the inlay glaze make
micro-crystal formation more certain,
and as seen here, some of those
micro-crystals are nearly 3/8 inch in diameter.
in the inlay glaze will migrate into the matrix.
the line is a mixture of inlay glaze,
matrix glaze, and crystals growing in the matrix.