Monona Rossol on fri 21 aug 98
---------- Forwarded message ----------
Date: Thu, 20 Aug 1998 10:47:17 EDT
From: Barbara Lewis
To: CLAYART@LSV.UKY.EDU
Subject: Re: Lead glaze safety
------------------------forwarded message------------------
The other thing that hasn't been mentioned, but I think Monona Rossol can
confirm, when Duncan/Mayco lead glazes were recently tested, they showed
higher concentrations of lead than was stated on the label or in their
literature. Barbara
>--------------------------reply----------------------------
It's a bit more complex. All the U.S glaze companies that used lead frits at
one time were labeling their glazes based on an acid leach test. If the
unfired lead frit glaze didn't leach more than 0.06% lead on the test it
could be labeled lead-free!
Only after it was documented that one of these lead free glazes poisoned a
nursing home patient who swallowed some did this practice change. It is
possible that glazes people have in their possession are mislabeled as lead
free. And it is even possible that some glazes being sold today still are
mislabeled in this way.
It is important to remember that people's digestive tracts are not just acid
and water. In addition to acid, ingested glazes will encounter enzymes,
cellular activity, heat, movement, alkalies, and more. We are very
efficient at leaching metals.
And in the lungs, acid tests are totally irrelevant. So hopefully, this test
is being abandoned by all the certifying toxicologists. In two lawsuits last
year against the major glaze manufacturers, Dr. Stopford of the ACMI (AP/CP
seal people) stated in deposition that this test was useless in predicting
absorption. (FYI: Duncan, Mayco, Amaco, and C & R were defendants.)
As for FIRED glazes that leach more lead than the FDA test--you are on
your own. You need to test your ware. Over a year ago, FDA went to a
professional potter in Maine who had all the right equipment and years of
experience. About half of the stuff they tested flunked.
And the FDA limits are not as strict as California's. (cups: FDA
0.5ug/ml; CA 0.1ug/ml) Even the major chinaware makers like Lenox and
Noritaki didn't pass the CA lead-leach standards until about 1991.
And still the major chinaware makers test samples from every kiln load.
Inexplicably, some loads fail and are discarded. If Lenox can't reliably
make lead-safe ware without testing, what makes some potters think they can?
Monona
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York NY 10012-2586 212/777-0062
http://www.caseweb.com/acts/
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