Monona Rossol on thu 5 mar 98
ANSWER to Bill Palmer who wrote:
> As far as I know the FDA has never established limits for cobalt
> leachability. Nor have I ever heard of anyone routinely testing for it.<
In 1989, FDA called for comments about the leaching of other metals, but
there was not enough data in existence. I have collected some barium
leaching data. One lab test showed a pot made with a commercially
available cone 6 glaze leached between 3000 and 4000 ppm barium. I have a
letter from Dr. Stopford (ACMI) stating that a cup that leaches 800 ppm could
kill a small child.
A number of people have had ware tested for barium and there is an Australian
paper on barium leaching. I found one other paper that also looks at
leaching of zinc.
I also think you probably were not on Clayart back a while ago when a potter
wrote that she made a cobalt blue dinner ware set for a friend and intended
to test the ware. The first step was to place vinegar solution in a cup.
But the next morning, the inside of the cup had turned white.
These incidents are indicative of the kind of leaching problems potters can
have. It is important that metals other than lead or cadmium be monitored.
I am sending you a data sheet which discusses this problem and suggests using
the EPA drinking water MCLs as seat of the pants guidelines.
> It is commonly used with hotel china that is subject to as much regulatory
> scrutiny as any ware. Most hotel china is fired between cone 8 and 11. <
Always keep in mind that some hotel china and most other common consumer
china patterns from major manufacturers did not meet the 0.1 ppm California
lead leaching standard until just a couple of years ago.
> If are interested in having your ware tested or would like to know how
> testing is done, let us know. <
If you know of a lab that would like to be included in a recommended list of
labs who agree do the FDA leach test and then test the leachate for other
metals, let me know. I am working on such a list and will publish it
nationally.
Monona Rossol, industrial hygienist
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York NY 10012-2586 212/777-0062
http://www.caseweb.com/acts/
Brad Sondahl on fri 6 mar 98
So Bill Palmer wrote:
It is commonly used with hotel china that is subject to
as much regulatory scrutiny as any ware. Most hotel
china is fired between cone 8 and 11. <
And Monona Rossol Replied:
Always keep in mind that some hotel china and most
other common consumer china patterns from major
manufacturers did not meet the 0.1 ppm California lead
leaching standard until just a couple of years ago.
Just to keep things honest, neither statement relates to leachability of
Cone 10 stoneware. Most hotelware and commerical slipware is bisqued
very hot (cone 10 or above) , and fired with a low fire glaze.
Monona's statement on lead emission clearly refers to this sort of
glaze, since lead vaporizes at stoneware temps, and is not a factor in
stoneware glazes.
I personally think stoneware glazes (well balanced) are likely to be
more impervious to leaching, but only testing will tell. I'm getting a
little doubtful of anecdotal evidence...
--
Brad Sondahl
http://www.camasnet.com/~asondahl
Contributing to the potluck of the WWW
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