vince pitelka on wed 31 oct 01
> Actually the shells are still there after the firing and interestingly
> enough it seems 3-4 days after they come out of the kiln they start to
flake
> and turn into powder. But straight out of the kiln they are still rather
> tough. Why being in the air for a few days finishes of the process I will
> let others figure out. Thats what happens to me ....
In the firing limestone or plaster inclusions in the clay turn into calcium
oxide or lime, which upon cooling absorbs water and expands, causing "lime
pops." The sea shells also turn into calcium oxide (with trace materials),
and upon cooling absorb water and expand, which simply causes them to
physicallydisintegrate.
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://www.craftcenter.tntech.edu/
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