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cone 06 firing disaster

updated sat 30 nov 96 on fri 8 nov 96

Hi All,
I just talked to another VT potter who is having business crushing problems
in her firings. It had been mentioned on Clayart before but I thought I'd try
again because I didn't understand the true problem from the original post
She is firing Sheffield cone 06 clays(red and white) in a gas venturi burner
kiln and using underglazes with Gare gg1700 fritted lead glaze over them. She
fires oxidation.
In the glaze firing a deposit shows up on the shoulders and rims of pots.
It's sort of like what soluble salt deposits look like, but this is in the
glaze firing. Nothing shows up before that. She has tried other glazes with
the same result. This didn't start til she had been using her kiln for 2 1/2
The problem goes away when she fires to 05 but them her sgraffito lines of
her most popular design disappear. The problem goes away in an electric kiln
but she can't afford to buy a new kiln to replace the gas one.
Any ideas out there? One idea is that it's lead migrating around the kiln.
Let me know any ideas and I'll give her the posts. Her kid has her computer.
Jennifer in Vermont, squirming at the idea of having a problem this bad and
wanting to help.