Gskwira@AOL.COM on wed 20 sep 00
We're in the process of choosing a new white stoneware body for Cone 6
functional work, fired in an electric kiln. A couple of bodies that look
pretty good, and are conveniently available, scare me a bit because they have
a broad firing range: One is listed as Cone 4-10, for example. Another is
listed by the suipplier as Cone 06-8 -- but I've used it in a wood fire, and
it seemed to turn out fine at Cone 10. I fear that firing a clay at the lower
end of its range raises possibilities that it will be insufficiently
vitrified, will take in water over time, and will result in crazing or other
problems -- getting hot or even exploding in a microwave oven, for example.
The absorbtion rate on the second of these bodies, by the way, is listed by
ther supplier as 0.9% at Cone 6.
Comments? Key points to consider? Absorbtion-rate guidelines for functional
ware? Useful testing procedures to determine safety? I'd appreciate any
thoughts y'all might have.
--Greg Skwira/Michigan
Cindy Strnad on wed 20 sep 00
Hi, Greg.
I am, unfortunately, not an expert in clay bodies. I keep working on
learning more, though. One thing I can tell you is that you should
definitely get a body whose upper limit is listed as ^6 if you want to fire
it to ^6. Listing clay as a ^4-^10 body is ridiculously stretching things.
^06-8 is even farther out. Silly. I'll even go so far as to say deceptive,
but then I'm in kind of a grumpy mood this morning.
Get a body whose range is ^5-6, then test it to see if it's suitable to your
work and your glazes. Test a sample for water absorption. Don't take the
dealer/ manufacturer's word for it. You don't know what kind of testing they
do or don't do, and it's quite possible there are even some out there who
just make up a number and stick it on the box. At least the guys I buy from
are honest enough to say they have no idea. Well, they're the only
ones close enough that I can afford the shipping, and luckily, the clay has
always been very good for me.
I hope you find something that works well for you.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
www.earthenvesselssd.com
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