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warping bowls (long)

updated thu 19 nov 98


Joyce Lee on wed 18 nov 98

Once ALL of my bowls warped; now only an occasional one does, or perhaps
several in one load might have that ugly ovaly shape. When that happens,
I read my notes from the firing and almost always find that I've stopped
taking some "basic" action that I learned on Clayart. These basics for
me are:

1) Check that the foot has a flat trim and is proportioned well.
2) Big one! slowly for even heating. This is the one I'm most
apt to forget. As long as my bowls are still lumpy/dumpies much of the
time, this step is very important. The temperature of the air at the
base of the pot may be different than the temperature around the rim at
critical times during the firing.
3) Sprinkle silica sand on the shelf for a ball-bearing type ride.
4) Dry bowls upside down. Dry bowls evenly.
5) Use flat kiln shelves.
6) Be sure those rims are strong, even, and defined.
7) Sometimes adding more flare to rims helps, all else being done. If
I'm having more problems than usual with warping, I fire a load with
exaggerated flared rims. Usually look fine...especially, if decorated,
unless one really looks closely, then maybe not so fine.
8) Recheck my most basic centering and opening moves. If I'm getting
careless, I can force the rim where I want it, but clay memory takes
over during the firing...and it's warpsville. Clay...all the points/

In the Mojave enjoying the contrast of the puffy clouds scudding just
above the small glass bottles on the window sill...bottles with greens,
blues, browns enhanced by years out in the desert sun...before winding
up in my computer room. Lots of irony there.