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safety of barium glazes fired at ^6?

updated sat 30 nov 96 on thu 14 nov 96

I am new to glazemaking, and am trying to teach myself, so please forgive
what may seem to be a foolish question.

While I have read that barium carbonate is highly toxic in its raw form, I
am unclear of its safety in fired glazes, e.g. fired to ^6. Is it unsafe
to use barium in any glaze intended for contact with food?

On a similar note, are there other elements or compounds (other than the
obvious lead) which should definately be avoided in dinnerware glazes?
Coaching on this important issue would be very appreciated. Thanks.

Scott Harper

Tony Hansen on fri 15 nov 96

Barium has the potential to be very dangerous in glazes. If you know how
to use it safely; great. If you don't I wouldn't touch it for food-safe

Heavy metal colors should be watched. Glazes that your put large amounts
of color into should have adequate silica and alumina.

Do whatever you want on decorative glazes, but for your liners get one
good functional balanced transparent that fits your clay and color,
opacify and condition it for an infinite variety.

Tony Hansen, IMC