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 iron_8_R_C10_13PSi, the foreground design is
glazed with satIron_ZG_1O_1Q_1MFe
The design is created by adhering a mask and then applying the main
glaze. After drying, the entire pot is coated in wax,
Previously I'd shown the glaze satIron_ZG_1O_1Q_1MFe as foreground glaze with
background glaze:
and also with background glaze:
Here, with the background glaze iron_8_R_C10_13PSi, in contrast to the prior
examples, the interaction region separates
The masked area is delineated by a thin black line. On the background side of
this line
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 .11
Al2O3 .56
SiO2 3.12
molecular percent Silica 63%
K2O .24
Al2O3 .47
SiO2 3.17
molecular percent Silica 66%
After firing, the area covered by the design mask is almost unchanged.
The inlay glaze and background glaze are of nearly equal fluidity, which
perhaps explains the stability of the boundary between the two glazes.
These are both high alkali metal glazes with similar silica.
iron_8_R_C10_13PSi has somewhat higher alumina and Iron,
then the mask is removed
and the open area filled in with a second glaze.
along the boundary of the original
mask into two distinctive bands.
is a diffused band of light red/orange crystals.
Close up Images of the interaction region
Image of the piece
bowl with glaze iron_8_R_C10_13PSi and inlay satIron_ZG_1O_1Q_1MFe
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 iron_8_R_C10_13PSi :
Na2O .45
Li2O .25
CaO .17
MgO .02
Fe2O3 .28
Inlay Glaze
satIron_ZG_1O_1Q_1MFe :
Na2O .22
Li2O .24
CaO .16
MgO .14
Fe2O3 .09
P2O5 .04
Remarks
lower Magnesia, and
no Phosphorus.