Albert Strauss on sat 17 may 03
I have a book of glaze recipes calling for lead bisilicate. As this
ingredient is just about unobtainable, and I want to glaze some dinnerware,
I need a substitute. Can someone recommend a way to modify these formulas
to eliminate the lead? Thanx
Regards
Al Strauss
PS can someone suggest a source for lead bisilicate in the US for use on
non-utilitarian pieces?
Lily Krakowski on sat 17 may 03
Sorry to be cruel and simplistic: THE ANSWER IS NO.
There are no "substitutes" for lead. Lead gave beautiful low fired glazes,
of a warmth and richness that has not been truly replicated. There are
glazes that come close to lead in beauty, almost, but not quite. Most of
these are boron based glazes.
Technically speaking: A replacement for bisilicate can be found by using a
lead containing FRIT. If you have calculated the formula, fritting it
should be easy IF YOU CAN LOCATE THE FRIT. A number of dealers no longer
carry lead frits. They too have insurance considerations.
I would suggest you abandon the idea of "converting" a lead glaze and plunge
into trying/testing the vast number of leadless ones around. But the way it
would be done would be to go with the formula and replace the bisilicate
with a leadfree frit that maintains proper silica content.
Forgive the bearer of bad news...And if I may add--I would not use lead in a
glaze even for non-utilitarian pots.
Albert Strauss writes:
> I have a book of glaze recipes calling for lead bisilicate. As this
> ingredient is just about unobtainable, and I want to glaze some dinnerware,
> I need a substitute. Can someone recommend a way to modify these formulas
> to eliminate the lead? Thanx
> Regards
> Al Strauss
>
> PS can someone suggest a source for lead bisilicate in the US for use on
> non-utilitarian pieces?
>
Lili Krakowski
P.O. Box #1
Constableville, N.Y.
(315) 942-5916/ 397-2389
Be of good courage....
iandol on sun 18 may 03
Dear Albert Strauss,
Are you talking about glazes for Earthen Ware, middle fire or Cone 8 and =
above??
As far as I know, there is no direct substitute for Lead as a glaze =
ingredient. Bristol Glazes which employ Zinc Oxide were invented to =
overcome some of the drawbacks of Lead as a flux.
Lead Bisilicate removes the hazards associated with ingestion of lead =
chemicals in the pottery. It is also a way of reducing the solubility of =
the glaze in use. In a well controlled situation, with correct =
formulation of the glaze, lead release can be reduced to acceptable =
levels.
My own solution to getting a bright glaze with the optical qualities of =
a transparent lead glaze was employ a high Sodium Felspar glaze and fire =
to stoneware temperatures. But this glaze does not develop the brilliant =
colours associated with a Lead Glaze.
Best regards,
Ivor Lewis
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