Jeff Tsai on tue 17 sep 02
I recall someone, I think Ron or John Hesselberth, posting to the list a
while back and giving the formula for a glaze that, when fired, looked
perfectly stable but when exposed to vinegar, i think, dissolved very quickly.
I wanted to use this as an example for a class and was wondering if anyone
had written it down because I don't know what keywords to search under to
find it.
-jeff
John Hesselberth on tue 17 sep 02
Hi Jeff,
I use a couple. One is called Toshika Green. You'll find the recipe for
it in the current issue of Clay Times, p39 or in Giorgini's Handmade
Tiles book, p 138. Another is G206 Jade Green--you can find that in our
book on p 20 or in Ceramic Formulas: The Complete Compendium by Conrad,
p 162. There is at least one in Lana Wilson's Book, Ceramics: Shape and
Surface (Purple/Pink, p36). Lana, though, knows that glaze is
unstable--she purposely uses glazes like this as a decorative technique.
There are lots of these glazes around though. Just look for one with
silica down at, say, 1.6 or below and 4% or more copper. You can be
virtually certain it won't pass the vinegar test and it may be bad
enough to fail within the confines of a classroom session given a little
exposure to lemon or lime juice.
I also know of a couple commercial glazes that are just as bad. I don't
pass that info around publicly, but I can be convinced to share it
privately for valid educational purposes (and yes I have told the
manufacturer--so far I don't think they have done anything about it)
Have fun. This makes an excellent classroom demonstration. I will
never forget the gasp from 4-500 people when I showed the slides of the
lemon slice demo at NCECA in Charlotte.
Regards,
John
On Tuesday, September 17, 2002, at 02:19 AM, Jeff Tsai wrote:
> I recall someone, I think Ron or John Hesselberth, posting to the list a
> while back and giving the formula for a glaze that, when fired, looked
> perfectly stable but when exposed to vinegar, i think, dissolved very
> quickly.
>
> I wanted to use this as an example for a class and was wondering if
> anyone
> had written it down because I don't know what keywords to search under
> to
> find it.
>
> -jeff
>
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Frog Pond Pottery
PO Box 88
Pocopson, PA 19366
Fax or phone: 610-388-1254
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