Migrating abutting glazes
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 longquan_n_song_Z2G_2I_0, the foreground design is
glazed with iron_8_R_C10_13PSi.
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 0.15
Al2O3 0.43
SiO2 3.61
molecular percent Silica 71%
Added:
0.2% silicon carbide as local reducing agent.
K2O 0.11
Al2O3 0.56
SiO2 3.12
molecular percent Silica 63%
The background glaze and inlay glaze belong to different glaze families. The
background is high in CaO, moderate in alkali metals,
Iron from the inlay migrated into the background creating a range of iron colors.
The range of colors reflects the changes in iron concentration.
The background glaze developed crazing near the inlay, yet beyond the iron
induced color changes. This would indicate that other components,
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 longquan_n_song_Z2G_2I_0 and inlay glaze iron_8_R_C10_13PSi
bowl is ~7 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
longquan_n_song_Z2G_2I_0 :
Na2O 0.16
CaO 0.51
MgO 0.09
ZnO 0.09
Inlay glaze
Empirical Formula iron_8_R_C10_13PSi :
Na2O 0.45
Li2O 0.25
CaO 0.17
MgO 0.02
Fe2O3 0.28
Remarks
containing trace
amounts of iron; the inlay glaze is a saturated iron glaze, high in alkali
metals, and lower in silica.
As a result
the inlay glaze is fluid, the background glaze viscous.
in
addition to iron, are moving into the matrix.