ret on sat 22 mar 97
---------- Forwarded message ----------
Date: 21 Mar 97 22:27:19 EST
From: Monona Rossol <75054.2542@CompuServe.COM>
To: ret
Subject: Re: barium research (fwd
Hodaka Hasebe wrote:
----------------------------Original message----------------------------
> I think that the following very serious test results are memtioned without
> contexts. Does this apply to all glazes using Barium with any firing
> range? <
I've seen results at cone 9-11, and cone 5-7. Looks like it probably is a
problem at any firing range in which barium is used.
> Are you suggesting zero tolerance on Barium for food related pottery. <
There isn't even a zero tolerance for lead in glazes. I suggest looking at
the 2 ppm EPA drinking water standard as a rough guide.
> If not, closer to the subject we deal with, like contents of glaze, better
> I can understand .<
But it doesn't look like there will be any way soon to relate the percent in
the glaze to the amount that leaches on a test. If there were a lot more
data, it might be possible to find something like a Thorpe's ratio to guide
potters, but for now, testing the finished ware is the only way to know.
(Thorpe's ratio was a ratio of lead to silica and alumina that roughly
predicted lead release.)
> And I do want to understand this matter better. Could
> you give me more specifics on at least these two examples, such as kinds of
> glaze (possibly a recipy) and which cone fired to, or hoplefully in general
> guideline--does a type of 1) base glaze make- alkaline, magnesia..etc. 2) %
> contents of barium used, 3)type of clay, 4) firing range- cone 6 or 10 make
> any differnce? <
Not one of these questions have an answer. This is what masters candidates
in pottery schools and technical colleges should have been working on for the
last ten years instead of producing yet one more dull paper on Bernard Leach.
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/
Hodaka Hasebe on mon 24 mar 97
Thank you Monona.
Now I know that some glaze in any firing range may have a problem.
As you stated that "it doesn't look like there will be any way soon to
relate the percent in
the glaze to the amount that leaches on a test" for contents of barium in
glaze, I want to make sure I understand collectly. Let me ask the
following questions, and I assume that answers for following 6 variables
are all YES. Am I right or wrong ?
Have you seen (tested) any corn 8-10 glaze with 2% barium carbonate (out of
total 100%) under any variation (e.g. gloss, matt, alkaline....) which
exceeded the 2 ppm EPA drinking water standard ? How about 10% and 25%?
On the other hand, have you seen (tested) any corn 8-10 glaze with 2%, 10%
or 25% barium carbonate under any variation (e.g. gloss, matt,
alkaline....) which did not exceeded the the 2 ppm EPA drinking water
standard?
Thanks.
hasebeh@vivanet.com
Ron Roy on tue 25 mar 97
>----------------------------Original message----------------------------
>Thank you Monona.
>Now I know that some glaze in any firing range may have a problem.
>As you stated that "it doesn't look like there will be any way soon to
>relate the percent in
>the glaze to the amount that leaches on a test" for contents of barium in
>glaze, I want to make sure I understand collectly. Let me ask the
>following questions, and I assume that answers for following 6 variables
>are all YES. Am I right or wrong ?
>
>Have you seen (tested) any corn 8-10 glaze with 2% barium carbonate (out of
>total 100%) under any variation (e.g. gloss, matt, alkaline....) which
>exceeded the 2 ppm EPA drinking water standard ? How about 10% and 25%?
> On the other hand, have you seen (tested) any corn 8-10 glaze with 2%, 10%
>or 25% barium carbonate under any variation (e.g. gloss, matt,
>alkaline....) which did not exceeded the the 2 ppm EPA drinking water
>standard?
>Thanks.
>hasebeh@vivanet.com
Hi Hodaka,
I assume you want my comments even though your post was to Monona.
Did you miss my post on the tests done on Barium glazes by Janet De Boos?
The article is in Ceramics Technical issue #3. She did not publish all the
results - none on what happens when you add in 3% and 6% copper. You can
get the full results fron Janet DeBoos, at The Ceramics Workshop,
Austrailian National University School of Art, PO Box 804, Canberra ACT
2601, Australia.
The cost is $A10. I tried an international money order but it was expensive
so I just gave them a credit card authorization.
Don't have it yet but the published results for cone 10 and 11 (30 glazes)
are in the CT article.
One of the conclusions she came to: release is related to amount of Barium
in the glaze. It is also related to how well the glaze fits into standard
limit formulas used to determine glaze durability.
I have seen tests on two cone 6 glazes. One had 2% Barium Carb and released
0.98ppm - the other had 4% Barium Carb and released 0.02ppm. The main
difference between the two glazes - The glaze which released 0.98ppm (and
had the least amount of Barium) was just under in Silica according to the
limit formulas I use.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
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