Craig Martell on wed 22 aug 07
Hello Fellow Shelf Washers:
I've had some problems with porcelain "plucking" and I've figgerd it out so
I thought I tell you all about my error so that perhaps it would be of
future help. Or, something like that.
I use a very fine mesh alumina oxide for some of my glazes. It's said to
be 325 mesh which is ultra fine as far as I'm concerned. I used it in my
shelf wash, which is 75% alumina oxide (not hydrate) and 25% kaolin. I use
the wash on Crystars and Advancers and I fire to cone 10-11 Reduction in a
propane fired kiln. I ran out of coarser mesh alumina so I used the fine
stuff. With this wash using fine alumina I got a lot of plucking which
seconded quite a few pieces. Since alumina is so refractory I thought the
mesh size wouldn't matter. I was dead-ass wrong. So I got a new bag of
100 mesh fused alumina, which is basically alumina oxide and that did the
trick. I just unloaded a fire and no plucking at all.
You can get all kinds of alumina oxide from Refractory
companies. Georgie's in Portland, Or got a 100 lb bag of the 100 mesh for
me from High Temp. Inc. also in Portland. I buy kiln bricks and Ceramic
Fiber from High Temp. They have alumina Ox. down to 48 mesh.
Just thought I'd pass that along to anyone interested.
regards, Craig Martell Hopewell, Oregon