Bob Johnson on tue 30 jan 07
If you will indulge me with 2 questions in one evening:
I'm going to try some white stoneware at ^6 in reduction, and I'm
wondering whether there is any point in doing a body reduction, as
one would do for a regular stoneware body containing iron. I would
think that, in order to keep the white stoneware white, I should skip
the body reduction and keep the fire neutral (or even oxidizing)
until the glaze reduction phase. But I dunno...
Bob - in Oregon
Ivor and Olive Lewis on fri 2 feb 07
Dear Bob Johnson,=20
The degree of discolouration will, to a greater extent, depend on the =
residual Iron compounds in your clay. It is well known that marginal =
amounts can give rise to a warm cream colour when the white body is =
fired neutral to oxidising and pale grey under reduction.
What is not always realised is that the change from Ferric oxide to =
Ferroso-Ferric oxide is reversible, since Fe3O4 and FeO which contribute =
to the grey colour are unstable in the presence of Oxygen at elevated =
temperatures
So a body reduction at low temperature, might not be necessary. But as =
exposed surfaces may be reduced when you reduce your glaze, access to =
air might be beneficial after your glazes are mature.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Bob Johnson on fri 2 feb 07
Thanks! This makes sense. I'll try a neutral fire up to glaze
reduction and then a brief oxidation when the cones go down.
Anybody else have experience with white stoneware or porcelain in reduction?
Bob
At 2/1/2007 04:43 PM, you wrote:
>Dear Bob Johnson,
>
>The degree of discolouration will, to a greater extent, depend on
>the residual Iron compounds in your clay. It is well known that
>marginal amounts can give rise to a warm cream colour when the white
>body is fired neutral to oxidising and pale grey under reduction.
>
>What is not always realised is that the change from Ferric oxide to
>Ferroso-Ferric oxide is reversible, since Fe3O4 and FeO which
>contribute to the grey colour are unstable in the presence of Oxygen
>at elevated temperatures
>
>So a body reduction at low temperature, might not be necessary. But
>as exposed surfaces may be reduced when you reduce your glaze,
>access to air might be beneficial after your glazes are mature.
>
>Best regards,
>
>Ivor Lewis.
>Redhill,
>South Australia.
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
Hank Murrow on fri 2 feb 07
On Feb 2, 2007, at 1:13 PM, Bob Johnson wrote:
> Thanks! This makes sense. I'll try a neutral fire up to glaze
> reduction and then a brief oxidation when the cones go down.
> Anybody else have experience with white stoneware or porcelain in
> reduction?
I like to give a body reduction even when firing to cone 10 in Ox. The
body gets greyer and colder in tone, which I like under my glazes. The
oil spot glazes provide the only exception to that among my firing
regimes. I don't do them much, because I need to fill a cubic meter in
my kiln. That's a lotta oil spot!
Cheers, Hank, getting ready for my first studio sales event in 5
years......... Valentines Sale Feb 9th & 10th!
www.murrow.biz/hank
| |
|
