Monona Rossol on sun 22 sep 96
BACK-LEAD-LABS-UMBER
Told you I'd be gone for a while. But read interesting clayart stuff since I
returned. One thread reminded me that I left a recipe with friends to mix my
ashes with ball clay and feldspar and how to fire. Now I no longer have a
kiln--maybe compost?
RANDOM LEAD TESTING
I can't believe no one has commented on Crafts Report, October 1996, Page 96,
"Random Lead Testing Results in a Positive Experience." Its written by potter
Judith Leigh Pearson about how the Maine regional FDA selected her for lead
testing. She was using "lead safe" glazes which I have always said are anything
but. Of the six cups FDA tested, two passed the federal 0.5 ppm limit
(California's limit is 0.1), and the others did not. One even tested 9.9 ppm!
The potter has switched to lead-free and considers this a "positive experience."
But she doesn't seem to realize that she is legally responsible for damages
cause by any of the pots she has ever sold!
She also thought the problem could be fixed by simply relabeling the lead glaze
for firing at a higher temperature. Wrong.
I have told people at FDA for YEARS that all they would have to do is locate
craft potters using lead and they would see this problem almost every time. Now
at long last, there seems to be a program for doing this.
There are just too many variables to use lead safely in a small pottery. Even
big commercial potteries with all their special controls test routinely for
lead. Still, every now and then, a whole commercial kilnload fails.
One thing that is very WRONG with the article is that the major manufacturer of
the glazes and the representative that she discussed this problem with are never
named. Even if Judith didn't write this article, her name now can be obtained
through freedom of information. The name of the manufacturer of the glazes that
got her in trouble should be just as available.
However, Judith makes a perfectly wonderful point when she states:
... "This is a major concern since the manufacturer supplies to most of the
elementary and secondary schools across the country. The firings in any school
setting aren't even going to come close to the kind of regulating we
professionals maintain. This means that all of those kids are bringing home
potentially hazardous projects." ...
From your lips to God's ear, Judith.
TESTING LABS
Charles Williams and Gail Dapogny asked about testing labs. I'll list two, but
why don't you leave your snail mail address in my e-mail box and I'll send you a
data sheet on testing and how to interpret the results.
Professional Service Industries 850 Poplar Street Pittsburgh PA 15220
412/922-4000 ask for Chemistry Dept.
Environmental Research Inc. 309-267 W Esplanade N. Vancouver BC Canada V7M 1A5
604/986-0445 ask for Bob Brown
BURNT UMBER
Janet H Walker asked about an analysis for burnt umber:
You either will have to experiment and line blend a bit or you will need the
mineral and chemical analysis of the umber to use it as a ceramic ingredient.
If you know who the manufacturer is, ask for an MSDS. Good MSDSs have partial
analyses under the "hazardous ingredients" section. If they are really kind
folks, they will give you the analysis. Believe me, they have access to the
analysis from their supplier.
Burnt umber can be any of a variety of natural and synthetic iron oxides. They
usually contain many impurities, the most common being manganese.
Just as an interesting side note: A common finish for wood is linseed oil and
burnt umber. Of course, linseed oily rags are likely to spontaneously combust
and cause fires. And the manganese in burnt umber has been known to speed the
exothermic drying reaction of linseed oil and increase the risk of fire.
Monona Rossol, industrial hygienist Arts, Crafts and Theater Safety 181 Thompson
St., # 23 New York NY 10012-2586 212/777-0062
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