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monona on food safety: glazed vs. unglazed pots (fwd)

updated tue 18 apr 00 on mon 17 apr 00

> ---------- Forwarded message ----------
> Date: Sun, 16 Apr 2000 18:02:54 EDT
> From:
> Reply-To: Ceramic Arts Discussion List
> Subject: Re: Monona on Food safety: Glazed vs. Unglazed pots
> Resent-Subject: Re: Monona on Food safety: Glazed vs. Unglazed pots
> ----------------------------Original message----------------------------
> Monona wrote:
> "Clay is a crystalline mineral in which the molecules are organized in a
> pattern and strongly held. Not all crystalline materials are inert--but
> clays really are about as inert as you can get."
> ---------------------------------
> I wonder if unglazed pots that are high-fired (and therefore vitrified)
> would be moreso safe than pots with glaze, based on the inertness of clay,
but the
> lack of inertness, with glass-formers (glazes).
> Monona, could you comment on this?
> Thanks for your good information.
> Milton NakedClay@AOL.COM <

Glad to. Clay doesn't stay "clay" in the kiln. Heat dissolves the various
clay minerals, the clay's free silica contaminants, iron, etc., into a
glass-like or vitreous mass. The clay, then, becomes only a silica and
aluminum contributor to that mix. But you are right, that the high
silica/alumina content should result in a rather stable material.

But high fired clayware would also be safer than glazed ware just because
there are not many metals present there that would be toxic. A little iron,
some aluminum and that's about all of significance that should come out of
such ware. It would also be important to fire high enough that the ware
isn't porous.

It would be fun to find out.

Monona Rossol
181 Thompson St., # 23
NYC NY 10012-2586 212/777-0062