Monona Rossol on mon 24 nov 97
Ron Roy wrote:
----------------------------Original message----------------------------
> The material used in glazes is usually Barium Carbonate - if that is what
> is ment in the following statement - all the statements are false! <
>----------------------------Original message-------------------------
Ron wrote this about the following and he was dead right.
>Barium used in a glaze intended to be functional should have no more than 5%
>barium. If the glaze contains more, it will leach. Barium is more toxic to
>your body, in the fired state ( as in a glaze ) than it is in the raw state.
>Your body can absorb the barium when it is leached out into food. As a raw
>materials it is not absorbed easily, that is why they use it for barium
e-rays. >K Griffith
The percentage tells you very little. There are glazes that contain much
more than 5% that don't leach significantly. There are glazes with 5 % that
do. In fact all glazes leach. What separates good glazes from bad is the
amount they leach. All people making food ware with toxic glaze ingredients
should test periodically.
Soluble barium ion is similarly toxic whether absorbed from leach
barium-containing food or from barium carbonate. Barium sulfate is used for
GI tests because it is not solublized by any of the mechanisms in the body:
acid, enzymes, etc.
Monona Rossol, industrial hygienist
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York NY 10012-2586 212/777-0062
http://www.caseweb.com/acts/
Ron or Sue Corl on tue 25 nov 97
Hi Monona,
Even though I am studying glaze making until my eyes are leaching,
is there know way to substitute Barium Sulfate for Barium Carbonate. I
understand that the molecular structure is different but can't we alter
other oxides in the glaze to keep the analysis the same?
I know that the books say to substitute Strontium for a non-toxic
substitute but I haven't had great success with that.
Thanks,
Ron
Big Baby Head Pottery
Monona Rossol on wed 26 nov 97
Ron wrote:
----------------------------Original message----------------------------
> Hi Monona,
> Even though I am studying glaze making until my eyes are leaching,
> is there know way to substitute Barium Sulfate for Barium Carbonate. I
> understand that the molecular structure is different but can't we alter
> other oxides in the glaze to keep the analysis the same?
> I know that the books say to substitute Strontium for a non-toxic
> substitute but I haven't had great success with that. <
--------------
As I understand it the sulfate radical makes a lot of trouble in glazes in
general.
But I think the real problem is that you are not privy to enough information
from your suppliers. For example, I would like to see them provide particle
size distribution and detailed batch analyses just like they do for the big
manufacturers.
I remember when potters were trying to substitute Gerstley Borate for
Colemanite and were having terrible problems. It turned out the problem was
the substitute was of a larger particle size and wouldn't integrate with the
other glaze chemicals properly. The strontium problem may be something just
that simple.
Potters are a small market and they kind of get the leavings of the industry
customers.
Sorry I can't be much help on this one.
Monona
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