Reactions at the interface between three glazes

The interaction at the interface of adjacent glazes.

Several closeups of the interaction region of the three glazes are shown and, for context, a picture of the pot.

The background glaze is alkTi_Z2D_1PZn, the foreground design is glazed with hankPaper_Z1R_2C_1 layered over
satIron_ZG_1Munge_1_Y. hankPaper_Z1R_2C_1 contains cobalt and copper.

The design is created by adhering a mask and then applying the main glaze. After drying, the entire pot is coated in wax,
then the mask is removed and the open area filled in with a the design inlay glaze, which when dry has a second glaze applied atop it.

Close up Images of the interaction region

full view

Image of the piece

full view

bowl with background glaze alkTi_Z2D_1PZn

and inlay satIron_ZG_1Munge_1_Y overlaid with hankPaper_Z1R_2C_1

bowl is ~7 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 alkTi_Z2D_1PZn :

K2O        0.05
Na2O        0.11
Li2O        0.15
CaO        0.25
MgO        0.35
ZnO        0.09

Al2O3        0.40

SiO2        3.79
TiO2        0.22

molecular percent Silica 70%

Inlay Glazes

Empirical Formula satIron_ZG_1S_1Munge_1_Y :

K2O        0.06
Na2O        0.53
Li2O        0.2
CaO        0.2
MgO        0.01

Al2O3        0.54
Fe2O3        0.21

SiO2        2.99
P2O5        0.17

molecular percent Silica 61%

hankPaper_Z1R_2C_1 :

K2O        .13
Na2O        .12
Li2O        .05
CaO        .14
MgO        .02
BaO        .3
SrO        .24

Al2O3        .42

SiO2        2.7
TiO2        0.14

molecular percent Silica 63%

Added:
1% cobalt carbonate
0.7% Copper Carbonate

Remarks

All three glazes belong to different glaze families. The background glaze is a rutile blue glaze that is high in rutile and
contains ZnO. The first inlay glaze applied, satIron_ZG_1S_1_Y is a saturated iron glaze high in alkali metals
and phosphorus; the top layer inlay glaze, hankPaper_Z1R_2C_1 contains both BaO and SrO in addition to TiO2.

The top inlay glaze was applied in a thick layer, causing it to flow through both the bottom layer of inlay as well as the
background glaze. As a result the surface coverage of the inlay is substantially greater than the size of the original
inlay mask which is seen in the regions where both inlay glazes flowed, leaving behind the bare clay body.
Though this design crawled substantially, it is interesting in its effects.

The decision to apply a second inlay glaze was an instantaneous reaction to the failure of the first inlay glaze to stick to the pot.
I scrapped of what didn't stick, sprayed with water, then applied a second, more compliant glaze.

The patterns created by the flow of the inlay glaze through the background glaze reveals the immiscibility of the three glazes;
they flow through and around each other, rather than mixing into one homogeneous fluid.

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