micro-crystals in a modified oribe glaze

Another modification of an oribe glaze of David Woof.

This glaze is shown in two firings, the first with no downfire holds, and the second with
the downfire holds of the modification, oribe-woof-MAlk-PSi, shown here.

With the same holds as above, yet a distinct formula, the differences are attributable to the
changed composition of the glaze.

In the firing with no downfire holds we see a transparent emerald. By contrast, with holds in
the downfire, diffuse clusters and streaks of white particles are seen. These clusters are subtler
than the crystals seen in the above note. This may be attributed to the higher alumina in this glaze.
The shift to a bluer color may be attributed to the increased MgO.

Image of the glaze oribe-woof-PAl-PSiMg in Firing 1

full view

Image of the glaze oribe-woof-PAl-PSiMg in Firing 2

full view

The bowls are ~4 inches in diameter.

oxidation firing to cone 10 in an electric kiln

Firing profile 1

Up Fire profile cone 10

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 min at 2310 deg F

Down Fire Profile cone 10

Turn Kiln Off

Firing profile 2

Up Fire profile cone 10

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 min at 2310 deg F

Down Fire Profile cone 10

300 deg F an hour to 1850 degF with a hold of 2 hours at 1850 degF
300 deg F an hour to 1750 degF with a hold of 1 hours at 1750 degF
300 deg F an hour to 1700 degF with a hold of 3 hours at 1700 degF
25 deg F an hour to 1650 degF with a hold of 1 hours at 1650 degF

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

glaze composition

Empirical Formula oribe-woof-MAlk-PAl-PSiMg:

K2O        0.10
Na2O       0.04
CaO        0.61
MgO        0.25

Al2O3      0.35

SiO2       3.29

molecular percent Silica 70.6%

Added:

5% black copper oxide

Remarks

This is a low alkali metal glaze, with alkali metal:alumina ratio nearly the same as the glaze in the
prior note, resulting in similar fluidity at maturation.

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