ret on mon 19 may 97
---------- Forwarded message ----------
Date: 18 May 97 10:38:40 EDT
From: Monona Rossol <75054.2542@CompuServe.COM>
To: ret
Subject: Manganese question (fwd)
---------- Forwarded message ----------
Date: Sat, 17 May 1997 10:46:29 EDT
From: "Robert Speirs, M.D. 766 X4450"
----------------------------Original message----------------------------
A friend and I use a high manganese bronze glaze for certain non
functional pieces. However, she recently glazed some cups with it on
the outside with a clear glaze inside. Since the lips would touch the
outside of the lip of the cup where the bronze glaze is, do you believe
there is a potential health problem?? (Monona, are you listening?) I
was very emphatic telling her how deadly manganese dioxide can be. She
said she would not sell the cups until she heard your answer.
Thanks for you help on this and a million thanks to all who have
responded to my questions regarding my new studio and concrete floor,
etc. Laura in Oregon
---------------------------------------------------------
This question is easy to answer ethically but tough to answer technically.
Ethically, we can rely on the FDA standard for glassware that doesn't allow
decals or decorations that leach lead within a certain distance (1/4 inch I
think) from the rim. That's probably a good plan for use of other toxic
metal-containing glazes, too. And although I can't tell you about it yet,
there are going to be some new regulations in this area announced by the FDA
sometime in the next couple of months.
The difficult part of the answer is caused by the fact that we don't
know how much manganese the bronze glaze leaches. It could be
insignificant. In general, however, glazes that achieve a metallic sheen from
metal compounds leach like crazy. The only case I know of in which iron
poisoning occurred over time in an adult was from a metallic-sheen iron glaze
on the inside of coffee cups used daily. And it take a hell of a lot more
iron to cause a problem than manganese.
Wish I could be more specific. I also will not be able to rebut the
arguments I might get on this point. I'm catching a plane in a couple of
hours and I wont be picking up my messages again until May 24.
Bye 'til then.
Monona
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