Ray Aldridge on thu 18 nov 99
I have to say first that the effort to find out a bit about these stains
has been my strangest experience on Clayart.
I'd never before thought of potters as the sort of people to whom political
correctness was more important than fact, but I guess I have to bid adieu
to that bit of comforting naivete.
Several posters to the thread took the view that there was no practical
difference between encapsulated stains and lowfire enamels-- they all
contained cadmium and that was that. To me this made about as much sense
as saying that a fishing sinker and a hollowpoint bullet emerging from the
barrel of a Smith and Wesson at 1300 feet per second were equally
dangerous, because both were made out of lead.
But even more distressing to me was the realization that there were some
folks here who resented the discussion itself, who felt that we shouldn't
even be talking about the safest way to use these pigments. One poor soul
even wrote me a nasty little note about my "trivial nitpicking questions,"
and then removed a link to my website. I was particularly saddened by
this small-minded treatment, because this was a person I had previously
held in the highest esteem, one who had been very helpful to me and many
others, and a person whom I would have expected to understand that
researching obscure scientific and legal facts requires a lot of
nitpicking, particularly if you don't know much about the subject.
I eventually came to understand that the impulse driving these well-meaning
folk was the same impulse that drives school boards to kill off sex
education in the high schools-- the pious hope that if we just tell kids
not to do it and then never mention the subject again, they won't do it.
I'm sorry, but it's just as stupid to tell several thousand potters not to
use these stains without rigorous testing and then attempt to quash any
ensuing discussion on the safest way to use them. The kids are gonna do
it, and so are the potters, and many of them will take the company's word
for the safety of the product, and they will not have their glazes
rigorously tested. This may be distressing. It's still the truth. No
amount of wishful thinking or sanctimonious admonitions will change it. Far
more practical, in my opinion, to offer these potters guidance on how best
to achieve a reasonable degree of safety, short of complete abstinence or
rigorous testing.
(By the way, I want to thank those who gave freely of their expertise,
including, among others, Ron, Edouard, Monona, and especially Michael
Banks. Their cheerful rationality made up for the rest.)
My opinion, for what it's worth, is that used in a relatively normal and
durable high temp glaze, these stains are probably pretty safe. So why
won't I be using them?
Well, it's partly because there's no practical way for me to test them
exhaustively. My technique involves freely layering slips and glazes, and
even though my use for these stains would have been as accents on top of
these layered glazes, I don't think there's any way I could be absolutely
sure that these small areas were not leaching cadmium, even in an ideal and
tested glaze, because I could never be certain that the glaze carrying the
encapsulated cadmium was not affected in some detrimental way by the fairly
active glazes underneath.
And it's partly because my primary decorative vehicles are large serving
bowls. I intend that these bowls be used in the kitchen on a daily basis,
and though few people serve a gallon of salsa and then store it in a wide
shallow bowl, the possibility exists.
But mostly, I have to confess, my decision is driven by marketing
considerations. My literature says "my glazes contain no lead, barium, or
cadmium." I can't imagine how to reword this to reflect the use of
cadmium, in a way that wouldn't be a red flag to a discerning buyer. No
matter how reassuring the copy, the message will still be that the glaze
does indeed contain a dangerous metal. It's just not worth the risk that I
might lose a sale. No single material is so vital to my work (except the
clay itself) that I would jeopardize sales to use it. If I don't sell, I
can't afford to make pots.
I suppose that if I were intending to use the stuff on the outside of pots,
on surfaces that never come into contact with food, I might simply omit any
mention of cadmium. In fact, I tried this omission out on one of my web
pages briefly, in anticipation of the possibility that I might use the
stain, but it made me uneasy just to look at it. A lie by omission is just
as serious to me as a lie by commission. Unfortunately I suffer from an
obsessive regard for honesty, one that frequently exasperates my more
flexible friends when it pops up in inconvenient situations when a little
white lie would be useful and harmless.
Anyway, I'm not looking down my long self-righteous nose at anyone who does
use these stains. But if it's at all practical in your situation, have the
glaze tested. And if that's not possible, use the kind of glaze Michael
Banks has indicated might work best-- maturing well above the boiling point
of cadmium, durable, not excessively alkaline, not overloaded with flux,
with alumina and silica in fairly normal amounts, with a small amount of
zirconium to retard the stain carrier's tendency to go into solution. Most
of all, be honest with your customers about what you're doing.
So there you have it. I still need an oxidation pink, so I'm back to the
alumina-manganese stains that can stand C8. Of which more anon.
Ray
Aldridge Porcelain and Stoneware
http://www.goodpots.com
madwa on fri 19 nov 99
Ray
I applaud your wee conversation - good common sense should hold us all in
good stead. I believe that we as potters, are responsible for the dangers
we pass on to our customers and that it's up to each one of us how much
danger we're willing to pass on. I, for one, am not willing to pass on any
knowingly.
Sharry
| |
|
