Reactions between adjoining glazes

The interaction between two adjacent glazes.

Closeups of the interaction region of the two glazes are shown and, for context, a picture of the pot.

The design is created by painting rubber latex on the bisque pot then after the latex has cured, applying the main glaze. After drying,
the latex is removed and the open area filled in with a second glaze.

Close up Images of the interaction region

full view

Image of the piece

full view

plate with glaze satIron_ZG_1S_1Munge_h and inlay copperYellow_Z26_1

plate is ~9 inches in diameter

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 satIron_ZG_1S_1Munge_h :

K2O        .06
Na2O        .51
Li2O        .21
CaO        .21
MgO        .01

Al2O3        .53
Fe2O3        .22

SiO2        3.18
P2O5        .16

molecular percent Silica 62%

Inlay Glaze

Empirical Formula glaze copperYellow_26_1 :

K2O        .27
Na2O        .27
CaO        .25
MgO        .12
ZnO        .09

Al2O3        .71
Fe2O3

SiO2        3.62

molecular percent Silica 68%

Remarks

The width of the interaction region varies, it is as much as 3/4 of an inch.

The reaction region contains colors and textures not seen elsewhere in either glaze. In parts of the design,
the reaction region has entirely taken over the area covered by the inlay glaze copperYellow_Z26_1.
Most surprising to me were the distinctive rings of colors fanning outward from the design in the reaction region.

The background glaze satIron_ZG_1S_1Munge_h exhibits a metallic precipitate which is a gold color. The inlay glaze copperYellow_Z26_1
has no metallic phases. Yet there is a prominent silvery gunmetal metalic phase visible in the interaction region.
Where did that come from?

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