vince pitelka on sat 30 nov 02
> I have been thinking about how to answer this in a concise way. I do think
> you are right about the surface iron being able to oxidize enough to not
be
> a flux enough to melt through the glaze.
Ron -
I think you have it right. I have always bisqued to cone 08, and at that
temperature it is apparent that the surface iron can re-oxidize to the
ferric oxide. At a higher 06 or 04 body reduction temperature there would
be far less chance of re-oxidation. I had been a potter for quite a few
years before I figured out the benefits of a "climbing" or "partial"
reduction after body reduction, and after that time I used to get a fair
number of pieces from almost every firing that would show little or no iron
speckles.
I agree that when iron deep within the body is reduced by excessive early
reduction in a glaze firing or by going through the "water smoking" period
to fast or with too little oxygen present in a bisque firing, the effect is
pretty much irreversible, producing carbon coring and often causing bloating
later in the glaze firing.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://iweb.tntech.edu/wpitelka/
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