Lesley Alexander on mon 10 dec 01
Just in case anyone is assuming there is no cadmium leaching from cerdec
stains, I'd like to mention that when I had a test done on 4% of red
cerdec in a clear glaze it yielded .003 mg/L of cadmium.... the
contamination level allowable in drinking water (EPA) is .005.... I
suppose one would be careful about using the glaze on food surfaces,
just in case, and particularly if using larger proportions of stain.
Lesley
John Hesselberth on tue 11 dec 01
on 12/10/01 2:14 PM, Lesley Alexander at celadon@SILCOM.COM wrote:
> Just in case anyone is assuming there is no cadmium leaching from cerdec
> stains, I'd like to mention that when I had a test done on 4% of red
> cerdec in a clear glaze it yielded .003 mg/L of cadmium.... the
> contamination level allowable in drinking water (EPA) is .005.... I
> suppose one would be careful about using the glaze on food surfaces,
> just in case, and particularly if using larger proportions of stain.
> Lesley
Hi Lesley,
Although I am not a fan of using cadmium in glazes under any circumstances I
would point out that the FDA standards for leaching of cadmium from ceramic
glazes (which is all that matters legally) range from 0.25 to 0.5 mg/l
depending on the type of vessel. Your 0.003 mg/l is nearly 100 times lower
than the lowest legal limit. Water standards are a useful (and extremely
conservative) reference point, but they are not something we need to meet
unless we are being super, super, super cautious.
Regards,
John
Web sites: http://www.masteringglazes.com and http://www.frogpondpottery.com
Email: john@frogpondpottery.com
"The life so short, the craft so long to learn." Chaucer's translation of
Hippocrates, 5th cent. B.C.
Alex Solla on mon 17 dec 01
which begs the obvious question: what was the formulae
and temperature of the glaze that the stain was used
in. How did you prepare the glaze? Did you ball mill
it?
Where did you have it tested? Have you tested for
leaching of colorants from that same base? Would be
nice to know for better evaluation.
-Alex
--- Lesley Alexander wrote:
> Just in case anyone is assuming there is no cadmium
> leaching from cerdec
> stains, I'd like to mention that when I had a test
> done on 4% of red
> cerdec in a clear glaze it yielded .003 mg/L of
> cadmium.... the
> contamination level allowable in drinking water
> (EPA) is .005.... I
> suppose one would be careful about using the glaze
> on food surfaces,
> just in case, and particularly if using larger
> proportions of stain.
> Lesley
>
>
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Ron Roy on mon 17 dec 01
We should also keep in mind that the standard test we use is with room
temperature vinegar.
There are other conditions we should keep in mind according to the use some
of our ware is going to have to perform under.
Consider how acid tomato sauce is and how much pasta is baked and stored in
some of the ware we make. Put those facts together with many of the
unstable glazes so many potters use and you are going to get much higher
release numbers.
I say - think about what you put on the market and be consevative about
this. In the long run you will at very least sleep better.
RR
>> Just in case anyone is assuming there is no cadmium leaching from cerdec
>> stains, I'd like to mention that when I had a test done on 4% of red
>> cerdec in a clear glaze it yielded .003 mg/L of cadmium.... the
>> contamination level allowable in drinking water (EPA) is .005.... I
>> suppose one would be careful about using the glaze on food surfaces,
>> just in case, and particularly if using larger proportions of stain.
>> Lesley
>
>Hi Lesley,
>
>Although I am not a fan of using cadmium in glazes under any circumstances I
>would point out that the FDA standards for leaching of cadmium from ceramic
>glazes (which is all that matters legally) range from 0.25 to 0.5 mg/l
>depending on the type of vessel. Your 0.003 mg/l is nearly 100 times lower
>than the lowest legal limit. Water standards are a useful (and extremely
>conservative) reference point, but they are not something we need to meet
>unless we are being super, super, super cautious.
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Nevin Murtha on tue 18 dec 01
I am not sure this will take us to an answer but drinking water standards
are based in part on the amount of water a "average" person consumes. As a
geologist a frequently have soils tested to determine if chemicals in them
could leach. The lab procedure uses acetic acid. Thus a would support that
plain water leaching does not appear to be an appropriate test. However we
have no way to tell how often a pot will be used or for what. I concur with
Ron on the better safe than sorry approach.
-----Original Message-----
From: Ron Roy
To: CLAYART@LSV.CERAMICS.ORG
Date: Monday, December 17, 2001 11:56 PM
Subject: Re: Cerdec yellow glaze
>We should also keep in mind that the standard test we use is with room
>temperature vinegar.
>
>There are other conditions we should keep in mind according to the use some
>of our ware is going to have to perform under.
>
>Consider how acid tomato sauce is and how much pasta is baked and stored in
>some of the ware we make. Put those facts together with many of the
>unstable glazes so many potters use and you are going to get much higher
>release numbers.
>
>I say - think about what you put on the market and be consevative about
>this. In the long run you will at very least sleep better.
>
>RR
>
>
>>> Just in case anyone is assuming there is no cadmium leaching from cerdec
>>> stains, I'd like to mention that when I had a test done on 4% of red
>>> cerdec in a clear glaze it yielded .003 mg/L of cadmium.... the
>>> contamination level allowable in drinking water (EPA) is .005.... I
>>> suppose one would be careful about using the glaze on food surfaces,
>>> just in case, and particularly if using larger proportions of stain.
>>> Lesley
>>
>>Hi Lesley,
>>
>>Although I am not a fan of using cadmium in glazes under any circumstances
I
>>would point out that the FDA standards for leaching of cadmium from
ceramic
>>glazes (which is all that matters legally) range from 0.25 to 0.5 mg/l
>>depending on the type of vessel. Your 0.003 mg/l is nearly 100 times
lower
>>than the lowest legal limit. Water standards are a useful (and extremely
>>conservative) reference point, but they are not something we need to meet
>>unless we are being super, super, super cautious.
>
>Ron Roy
>RR# 4
>15084 Little Lake Rd..
>Brighton,
>Ontario, Canada
>KOK 1H0
>Residence 613-475-9544
>Studio 613-475-3715
>Fax 613-475-3513
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
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