David Hendley on tue 23 nov 99
To Ray Aldridge,
I appreciated the reasoning behind your decision to not
use encapsulated cadmium stains. Everyone should or
should not use materials after careful consideration.
I have been using the encapsulated stains for about 5
years, so I obviously came to a different conclusion.
I find your marketing concern, which you say is your
primary motivation for shunning the stains, very curious.
I have never, in 25 years of selling pottery, heard a single
customer mention the word 'cadmium'. Ditto for 'barium'.
It's simply not a concern.
(As an aside to Louis Katz's post yesterday, yes, there
is usually a small amount of barium contamination in
strontium. So I've heard, and according to the analysis
from my supplier.)
>From a marketing point of view, I think it would be a
blunder for my literature to say that my pottery contains
no cadmium or barium, even if it were true.
Why in the world would I want to start talking about
dangerous chemicals that I don't use?
This would be akin to a politician stating on his literature
that he is not a racist, when he has never been so accused!
Also, Ray, and anyone else who advertises that they use
no cadmium: Do you ever use those neat under/overglaze
pens? Where does that bright stoneware red come from?
Lead, of course is a different story, and is in the public
consciousness.
I also do not think I am being dishonest with my customers
by using cadmium and not telling them.
I use these stains only in slips that are painted on the
outside of vessels. No food contact is possible. No glazes
are put over the slips that could dissolve the color. And the
color stays there; it's dense and opaque. In 5 years, I've
used maybe 5 pounds of stain.
I'm satisfied that this pottery is safe. I'd like to hear from
anyone, hopefully to the whole list, who thinks that what
I am doing is hazardous or irresponsible.
I do think it would be reckless to blindly use encapsulated
cadmium stains in glazes that will be in contact with
food or drink. I am frankly somewhat amazed that this
product is being marketed as 'safe' by a big international
corporation. The risk/reward ratio just seems too risky for
a big company to take the chance that no problems will
develop. Maybe that's why the stains are so expensive;
half the cost pays for liability insurance and to pay for
possible future claims!
I know that the use of lead in the past just about bankrupted
some very large ceramics & materials companies.
Best regards,
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: Ray Aldridge
Subject: Why I won't be using encapsulated cadmium stains (long)
| ----------------------------Original message----------------------------
| 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
|
Ray Aldridge on fri 26 nov 99
At 10:47 AM 11/23/99 EST, you wrote:
>----------------------------Original message----------------------------
>To Ray Aldridge,
>I appreciated the reasoning behind your decision to not
>use encapsulated cadmium stains. Everyone should or
>should not use materials after careful consideration.
>
>I have been using the encapsulated stains for about 5
>years, so I obviously came to a different conclusion.
>I find your marketing concern, which you say is your
>primary motivation for shunning the stains, very curious.
>I have never, in 25 years of selling pottery, heard a single
>customer mention the word 'cadmium'. Ditto for 'barium'.
I'm sure you're right that most customers are not concerned about these
metals. But I believe my approach has significant marketing advantages. To
illustrate, back in the early 70s, when I first started selling pots, not
many studio potters said anything about lead on their hangtags (if they
even had hangtags) even though most of us did not use lead. And as is the
case with cadmium now, few customers knew enough to ask about lead. But I
noticed that a number of commercially successful potters did indeed notify
their customers that their glazes were lead free. I realized that their
customers were reacting favorably to this information; it was a powerful
symbolic gesture. These potters were explicitly concerned about the health
of their customers, and the customers responded with greater trust. I
started advertising the fact that my wares were lead-free, and I saw this
interaction personally.
There are other reasons as well to mention cadmium and barium in one's
literature. For one thing, it gives customers a starting point for
conversation-- and that's always good, from a selling viewpoint. And it
gives one a small advantage, I believe, over other potters who do not
explicitly notify their customers that their glazes are free of noxious
substances. If confronted with two pots of similar desirability, many
customers are going to buy the one that has the most reassuring copy
attached to it, all else being equal. That's why the guys on Madison
Avenue get the big bucks.
>Also, Ray, and anyone else who advertises that they use
>no cadmium: Do you ever use those neat under/overglaze
>pens?
No.
>I'm satisfied that this pottery is safe. I'd like to hear from
>anyone, hopefully to the whole list, who thinks that what
>I am doing is hazardous or irresponsible.
>
I don't think so. It's my (inexpert)opinion that these stains are fairly
safe even on surfaces that might contact food, as long as the glaze is
fairly normal and fired well above the boiling point of cadmium. I don't
see the possibility that fumed cadmium might settle on interior glazes as
very likely, especially in your case, because you're firing in a
fuel-burning kiln. Any fuming is going to be immediately diluted by the
enormous volume of gases passing through the kiln during the time the
cadmium might be expected to vaporize from adjacent kiln surfaces. As a
rationale for why this is probably not a serious concern, anyone who's done
any amount of saltfiring knows how difficult it is to get the salt fumes to
interact with the clay inside a bowl or other vessel; if you want a
functional surface, you have to glaze these insides with a suitable glaze.
And in that case, you're dumping pounds of salt into the fireboxes, closing
the damper, etc. The possibility that the few grams of cadmium which might
evolve from the stains could form any measurable deposit inside your pots
seems pretty remote to me.
Ray
Aldridge Porcelain and Stoneware
http://www.goodpots.com
| |
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