David W McDonald on mon 23 aug 99
Ron,
Here's the letter I received from Jon Pachini at Laguna:
LAGUNA CLAY COMPANY Ceramic Research and Supplies
Mineral Ceramic Products * S. Paul Ward Co. * Westwood Ceramics *
Pacifica Potter's Wheels * Miller Ceramics
June 29, 1999
David McDonald Limberlost Pottery 721 First St.
Prescott, Ariz. 86301
Subject: Amador Bloating
Greetings David,
Here is the gradient bar I fired TO 2400* F. Ox. If you're not familiar
with how to read one of these, the temp-chart coincides with the marks on
the bar. The highest temp reached being 2410* @ position #8. The temp
drops off in both directions, but at different rates. The only bloat
occurs at the high point. I've included a bowl thrown from your clay that
was fired cone10 in our test kiln. The only bloat is in the foot, where
it's thickest and carbon cored. I think your bloating was more temp
related than atmosphere. By backing off of the feldspar a bit we seem to
have gotten away from the over vitrification that was taking place. By
firing your bisque higher and soaking at the end point you will reduce
the risk of trapping organics and gasses that also contribute to the
bloating in the high fire.
I am currently evaluating all the suspect sand we have in stock and am
revamping our QA on this material. Sorry to have put you through this
ordeal, Thank-you for your patience and your assistance in resolving this
problem.
Best regards,
Jon Pachini
Clay Manager Laguna Clay Co.
CALIFORNIA
14400 Lomitas Avenue
City of Industry, CA 91746
(818) 330-0631
Fax (818) 333-7694
COLORADO
2625 S. Santa Fe Dr., I -B
Denver, CO 80223
(303) 722-5575
Fax (303) 722-5298
OHIO
301 Gomber Avenue Cambridge, OH 43725
(818) 330-0631
Fax (818) 333-7694
NEW YORK
4022 Mill Road
Skaneateles, NY 13152
(315) 685-8378
Fax (315) 685-3152
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