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glaze stability of low fire glazes

updated fri 26 may 00


John Hesselberth on thu 25 may 00

I taken the pledge to look at glaze stability for some low fire glazes
this summer. Since I don't normally work at low fire, I need some help.
I'd like some recipes to test. Ones that you like and use and contain
materials you might be concerned about. As always, I am most interested
in copper; however cobalt, manganese, nickel and chromium are also of
interest. I may well look at boron too; however that will be in all of
them. I will only be testing lead-free glazes and I would prefer boron
that is supplied via frit rather than via gerstley borate or one of the
replacements currently being developed. The gerstley borate situation is
just too unstable at the moment.

So this is your chance to have me test a recipe you've been wondering
about, but haven't quite gotten around to testing yourself. I will
initially choose about 6 glazes to test representing a range of
compositions and surfaces. I will, of course, directly inform the
submitter of the recipe of the results and will post them on my web site
for all to see.

I will bisque at only one temperature (probably 04), but am willing to
glaze fire in the range of 06-04. If you send me a recipe, please tell
me as much as you can about how it is best fired (e.g. automatic shut off
via small cone 06 in a kiln sitter can be quite different from visual
observation of large cone 06 going down).

Thanks for any help you can give me. To avoid cluttering the list it
might be best if you sent them to me off-list at

John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: web site:

"Pots, like other forms of art, are human expressions: pleasure, pain or
indifference before them depends upon their natures, and their natures
are inevitably projections of the minds of their creators." Bernard
Leach, A Potter's Book.