micro-crystals in a modified oribe glaze
In this modification of an oribe glaze of David Woof, sufficiently long holds
in the downfire
This glaze is shown in two firings, the first with no downfire holds, and the
second with
In the firing with no downfire holds we see a clear transparent emerald
glaze. By contrast
The bowls are ~4 inches in diameter.
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
Turn Kiln Off
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
300 deg F an hour to 1650 deg F with a hold of 8 hours at 1650 deg F
400 deg F an hour to 1900 deg F with a hold of 4 hours at 1900 deg F
K2O 0.13
Al2O3 0.36
SiO2 2.75
molecular percent Silica 66.7%
Added:
5% black copper oxide
This second firing has a total of 12 hours of time added in its cool down.
It has an 8 hour hold at
Here the distribution of the time, down then up is not like that which would
have obtained in any
I did two pairs of firings, each firing in a pair had the same total time
in the downfire holds,
produce extensive growth of micro-crystals within the glaze.
extensive downfire holds.
with sufficient downfire holds, a much crystallized
surface is seen.
Image of the glaze oribe-woof-PAlAlk in Firing 1
Image of the glaze oribe-woof-PAlAlk in Firing 2
oxidation firing to cone 10 in an electric kiln
Firing profile 1
Up Fire profile cone 10
Down Fire Profile cone 10
Firing profile 2
Up Fire profile cone 10
Down Fire Profile cone 10
Clay body is a grolleg porcelain from Clay Art Center in Tacoma, WA.
glaze composition
Empirical Formula oribe-woof-PAlAlk:
Na2O 0.04
CaO 0.64
MgO 0.19
Remarks
1650 degF followed by a four hour hold at 1900 degF.
Firings in large fuel burning kilns might easily
have had even more time in
the cooldown.
traditional firing, and I do not know that for this glaze
that makes a difference. I do believe that
the extent of the time does.
yet distributed differently. The first pair
firings had a total downfire time of 8 hours,
the second pair 12 hours.
The difference between this glaze in the two firings of each pair
was minimal, the difference between a firing with 8 hours of downfire
holds and 12 hours of
downfire holds was substantial.