Glaze Reactions in a spotted Iron Glaze

An iron matrix glaze, with midnight black and silvery gunmetal micro-crystalline inclusions,
has a glossy blue-green inlay. The resulting design has fragments of glassy blue laced with
chaotic yellow tracings.

Close inspection of the yellow tracings show them to bound the glassy inlay on one side, the black of the
matrix glaze on the other.

Perhaps the entire inlay slid just a bit down the wall of the pot, perhaps a quarter of an inch,
allowing iron from the matrix glaze to penetrate nearly all of the inlay.

The matrix (i.e., background) glaze and inlay glaze overlap minimally before firing. The width of the
original inlay varied from an eighth of an inch to three eighths of an inch.

The background glaze is oribe-satIron; the inlay design is glazed with oribe-woof-PAlkAl-PSiMg

The design is created by adhering a mask and then applying the main glaze. After drying,
the mask is removed and the open area filled in with a second glaze, using a bulb syringe
with a needle applicator.

The close-up images were heavily edited to enhance detail and colors are brighter as a result.
The colors of the full image of the bowl are as they appears in bright light.

Close up Images of the interaction region

full view

Image of the piece

full view

bowl with glaze oribe-satIron and inlay glaze oribe-woof-PAlkAl-PSiMg

bowl is ~7 inches in diameter

oxidation firing to cone 10 in an electric kiln

Firing profiles

Up Fire profile hot cone 10

150 deg F an hour to 250 deg F
300 deg F an hour to 1800 deg F
200 deg F an hour to 2050 deg F
120 deg F an hour to 2320 deg F with a hold of 25 minutes at 2320 deg F

Down Fire Profile hot cone 10

300 deg F an hour to 1850 deg F then a 2 hr hold at 1850 deg F
300 deg F an hour to 1750 deg F then a 1 hr hold at 1750 deg F
300 deg F an hour to 1700 deg F then a 3 hr hold at 1700 deg F
25 deg F an hour to 1650 deg F then a 1 hr hold at 1650 deg F

Clay body is a grolleg porcelain from Clay Art Center in Tacoma, WA.

glaze composition

Empirical Formula oribe-satIron :

K2O        0.15
Na2O       0.28
CaO        0.39
MgO        0.18

Al2O3      0.52
Fe2O3      0.21

SiO2       3.39
P2O5       0.05

molecular percent Silica 65.57%

Added:

5.0% cobalt carbonate

Inlay Glazes:

Empirical Formula oribe-woof-PAlkAl-PSiMg:

K2O        0.17
Na2O       0.05
CaO        0.49
MgO        0.29

Al2O3      0.35

SiO2       3.3
P2O5       0.01

molecular percent Silica 70.68%

Added:

5.0% Copper Oxide

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