John Baymore on mon 19 may 97
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Lead in glazes is an interesting topic. Glazes can be made
badly and leach lead into food, and they can be made very well and
leach such low amounts that standard testing cannot even detect any
lead.
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I think the whole conversation in this post was extremely well put. Good
overview of the subject. Way to go, Bill!
I particularly liked the discussion of .......... it's important to use it
well or someone will take notice............ . I think that is ALL TOO
TRUE.
IMHO.......... I think that there is a real possibility that we will see
barium release included in the FDA 's rules within the next 5-10 years. I
think that the studio potter's propensity for taking a "glaze" composed of
something like 30-35% Barium Carbonate, dumping in a handfull of Copper
Carbonate, calling it "Peacock Blue" , and slapping it on serving platters
has helped contribute to this situation. Such inappropriate "fuel for the
fire" will help the "regulators" push for the need of regulation.
If we police ourselves better, we may help hold off the need for formal
regulation.
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(snip>Can anyone explain what is "glazes made badly" and "glazes made very
well"
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In a basic sense, glazes (with lead) made badly will leach unacceptable
levels of lead while glazes made well will not leach lead that is
detectabile with current testing.
Sorry if that sounds "flip" in a way, but it is the way of the thing. The
only way to be sure about leaching issues is to do random sample testing of
work, after doing your chemistry homework in the original molecular
formulation and good raw material sourcing control in the compounding of
the batch.
If you choose to use a potentially toxic material like lead, it seems to me
that you just can't get away from the necessity of testing.
One main reason for this is the fact that the thickness of application of
the glaze slurry to the pot and also the firing cycle can affect lead
release. So even if the glaze batch is composed well, a variation in the
application or firing can make a generally "good" glaze leach more than it
ususally does.
The "lower tech" the controls you have in place for these aspects of the
process, the higher the likelyhood that you will have major variations in
the leaching qualities of the fired product. Since the consequences of
these variations can be significant (morally as well as financially), it
would seem that you either have to not use the material or be prepared to
do whatever is necessary to make sure that it is used well.
As the saying goes....... "If you can't do the time, don't do the crime".
BTW...... none of this discussion going on addresses the appropriate
handling of the materials by the potter (or assistants) in the studio.
This in reality may be one of the more significant issues in routinely
handling lead compounds.
_________________________________
First of all we are all unique in our genetic make up. Offering the
example
of one man surviving exposure to chrome is not exactly a scientific study.
There are those among us who will be affected by exposure to chrome. When
we know how to tell who will be and who won't - then we will be able to
make an inteligent choice.
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Ron.......... simply beautiful!
And ditto for lead compounds. And manganese...... and ....... and.......
and.......
Another issue here is the total burden placed on the body from ALL "toxic"
asssaults. If your body's systems are fighting a lot of little battles
with all the things you are exposed to in your life, who knows when the
next one will "push it over the edge"? Best to be as careful as possible
with ALL toxic materials.
Best,
........................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752
JBaymore@Compuserve.com
Russel Fouts on tue 20 may 97
John,
>> One main reason for this is the fact that the thickness of application
of the glaze slurry to the pot and also the firing cycle can affect lead
release. So even if the glaze batch is composed well, a variation in the
application or firing can make a generally "good" glaze leach more than
it usually does. <<
Lawrence in his book shows a pretty dramatic difference in lead
release depending on whether the atmosphere in the kiln is moving or not as
well. Moving = less, not moving = more (the book is 7 flights down in the
studio and I'm still in my jammies so I'm not going to go get it, so
there!)
Sounds reasonable given lead's tendency to volitize but I've never
heard anyone else mention it (in the MANY discussions regarding lead on
this list)
Russel ("I love the smell of Clayart in the morning" paraphrasing
Robert Duval, "Apocolypse Now")
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* Russel Fouts, CI$: 100021,23,
Bruxelles, Belgium
Internet: 100021.23@CompuServe.Com
"It took more then one man to change my name to Shanghai Lil."
MD
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