This to me is a question that is not easily to answered. John Hesselberth
and Ron Roy have touched on it in their book and conclude that rather than
talk about the issue in terms of "food safe" instead ""safe to use with food
provided the clay/glaze fit issues ... are also addressed" (not to put words
in their mouth but that the glaze does not shiver or craze (so it does not
would allow bacteria or mold to grow). Copper easily leaches out of glazes.
Their Spearmint has leaching of copper at 1.63mg/l. They treat this as a
glaze safe to use for functional ware but they do not call it food safe. I
highly recommend Mastering Cone 6 by Hesselberth and Roy if you do not have
it.

I use copper bowls to beat my egg whites. I most certainly get more copper
out of that than I would out of almost any copper glaze I have ever used
however if the glaze is leaching a great deal of copper you have to ask
yourself do you really want the taste of food tainted with metal whether it
is dangerous our not. And then there is the issue of the glaze itself
losing it's beauty. You want a stable glaze for safety, for function and
for beauty.

If you want to be ridged about it and error on the side of safely then you
would not use a glaze on the inside of any piece which could hold food that
has lead, cadmium, barium, cobalt, copper (heavy metals) in it and that fits
the clay perfectly. In other words a liner glaze of white, clear or
brown....

John and Ron suggest using EPA standards for water (note that cobalt, copper
and lithium are not listed by the EPA).

http://www.epa.gov/OGWDW/dwh/c-ioc/cadmium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/chromium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/copper.html
http://www.epa.gov/OGWDW/dwh/c-ioc/barium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/selenium.html
http://www.epa.gov/OGWDW/dwh/c-ioc/lead.html

"Elaine Stutt" wrote in message
...
I know we're not too active here but i'd be interested in your
definition of food safe and how you determine if a glaze or particular
piece of pottery is food safe. Anyone reading this in the next month
or so feel free to chime in.

Thanks,

Elaine