Jess McKenzie on sun 20 sep 09
John Hesselberth said, in part ...
I would think you would want to start reduction before the
glaze seals over to get the maximum effect. ...
That "glaze seal" John referred to has an historic
significance. Those old Greeks we mentioned earlier today
took advantage of it. Put simply:
1. Parts of the pot were painted with terra sig or "Greek
Glaze." Then the pots were fired under conditons of both
oxidation *and* reduction.
2. First, oxidation fire produced a red iron.
3. Following that, reduction fire at a higher temp produced a
4. In reduction, the kiln temp reached high enough temps to
sinter (or "seal") the terra sig but not the basic clay.
5. After that, the kiln was aerated to allow re-oxidation to
a red iron, *except* for the reduced (black) iron, which had
been sealed by the sintered terra sig.
The result: black where the terra sig had been applied, red
where it hadn't--that fabulous Attic pottery y'all had to
study in Art History.
We'd be surprised if no one has done an MFA on this.
Good point, John.
~joan and jess in Sequim, WA