micro-crystals in another modified oribe glaze

Another modification of an oribe glaze of David Woof, holds in the downfire
produce extensive growth of micro-crystals within the glaze.

This glaze is shown in two firings, the first with no downfire holds, and the second with
somewhat less extensive downfire holds than in the previous modification, shown here.

In the firing with no downfire holds we see a transparent turquoise glaze with hints of
texture where the glaze is thick. By contrast, with holds in the downfire, variegated crystal
clusters are seen. These crystal clusters are rather different that the crusty crystals
seen in the above note. This may be attributed to either the change in holds, the change in the
formula, or a combination of both.

Image of the glaze oribe-woof-MAlk-PSi in Firing 1

full view

Image of the glaze oribe-woof-MAlk-PSi 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-PSi:

K2O        0.08
Na2O       0.03
CaO        0.72
MgO        0.17

Al2O3      0.28

SiO2       3.05

molecular percent Silica 70.1%

Added:

5% black copper oxide

Remarks

This second firing has a total of 8 hours of time added in its cool down, distributed between the
temperatures of 1850 degF and 1650 degF.

Because this is a different mod of David Woof's oribe glaze than the previous note, the difference in
the result is likely attributable to the glaze composition as well as the firing profile.

This is a low alkali metal glaze, yet rather low in alumina which produces a fluid glaze which
will allow crystal growth.

Carol's Home Page