Craig Martell on wed 11 dec 02
Kat sez:
>Petalite has no thermal expansion and would help with thermal shock. The
>more you can get into the body the better it is.
Hi:
Petalite does have an expansion coefficient. It's lower than any of the
other feldspathic materials but it's not zero. I think Bruce's original
body question concerned a lower fire clay and petalite wouldn't work at
all. There has been a lot of research and testing done with petalite
bodies for flameware and ovenware and there is a higher failure rate in
petalite bodies that are fired below cone 11. If any of you folks have
ever done fusion buttons of petalite at cone 10 you probably have noticed
that it doesn't fuse as well as K and Na spars at that temp. So you need
to fire it higher to get the lower expansion benefits. I think that you
would need at least 25% petalite in the body to render it more flame and
oven proof. In a low fire body there would be not benefit at all from
petalite and it's spendy.
regards, Craig Martell Hopewell, Oregon
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