Brenda Phillips on thu 3 aug 06
Dear wise ones,
Does 'food safe' on commercial glazes mean that the glazes do not have =
lead or cadmium or does it include other safeguards against leaching?=20
Is there a standard beyond lead and cadmium or is it different for each =
company? =20
Thanks,
Brenda from Manchester, CA
John and Judy Hesselberth on thu 3 aug 06
Hi Brenda,
It's not possible to answer your question definitively. The law only
requires minimal leaching of lead and/or cadmium to be 'food safe' --
lead and cadmium free are not required. You can find the specific
standards on the FDA site or on my web site at:
http://www.frogpondpottery.com/glazestability/undglazestab.html
California has somewhat stricter standards.
There are glazes being sold by companies who know what they are doing
and care. There are also glazes being formulated by those who don't
know or care or are content to meet the minimum standards of the law.
It is difficult to tell which is which. Asking them directly is the
only possible way to tell--and if you get an evasive answer, beware.
Two companies that have responded best to my questioning on this
subject are Spectrum and Opulence. Spectrum has their glazes tested
for leaching and submits the results to an industrial toxicologist at
Duke University. They have told me they will share the results with
people who ask. Opulence has their glazes reviewed by an industrial
glaze consultant who, I believe, knows what he is doing. Although I
haven't met him, he has an excellent reputation.
I have invited other companies to tell us their testing procedures
here on Clayart. The silence is deafening. I have to conclude they
don't do any, but I would love to have to eat those words. So I raise
the question once again. Tell us, glaze manufacturers who monitor
Clayart, what your procedures are. Inquiring minds want to know.
Brenda, I hope this helps you. It is one of the many reasons I
decided to mix my own glazes--I really wanted to know how they would
perform.
Regards,
John
On Aug 3, 2006, at 1:01 PM, Brenda Phillips wrote:
> Dear wise ones,
> Does 'food safe' on commercial glazes mean that the glazes do not
> have lead or cadmium or does it include other safeguards against
> leaching?
> Is there a standard beyond lead and cadmium or is it different for
> each company?
>
> Thanks,
> Brenda from Manchester, CA
Martin Butt on sat 5 aug 06
John,
I'm glad I read clayart to the bottom yesterday! I'd hate to be lumped in
with glaze companies that don't know or care, because I do care about our
customers safety and satisfaction. In addition to being the originator of
Coyote Cone Six Electric Glazes, I have been a potter for 30 years; I want
my pots to be safe and to stand up well to everyday use, and I'm sure my
customers expect the same.
Our testing procedures consist of the following:
1. We have our cadmium bearing glazes (9 of our 72 colors) tested for
leaching on a regular basis. We use inclusion stains and very stable glaze
bases for these colors so the results have always been well below the FDA
standards. Even so, we encourage our customers to have their ware tested
because of the possible variations in firing, and the label on every
cadmium bearing glaze says that. We have a link to the lab we use,
Brandywine Laboratory, on our websites product safety page at
http://coyoteclay.com/productsafety.html
2. We test all our glazes with a 4 day soak in vinegar; if there is a
visible change in color or texture it will be labeled as "not recommended
for food use".
3. We have over a hundred students and studio members that use these glazes
every day here at Coyote. This may be our best testing method to find out
what to expect from our glazes in real life. This turned up one glaze that
passed the vinegar test, but showed discoloration from storing coleslaw-why
coleslaw and not vinegar I can't tell you. Also great for seeing glazes
after many trips through the dishwasher.
We also have leach tests done for glazes that contain potentially harmful
oxides. So far, this has not turned up serious leaching in glazes that
weren't already labeled "not recommended for food use" and in fact has been
reassuring for a couple of high copper glazes that I wondered about.
Of course, this brings up the question of what do you do with leach test
results. As I mentioned in my off list email to you, I continue to wrestle
with what "food safe" means in light of the lack of legal guidelines for
most materials. To those of you who are interested in this issue I highly
recommend reading John's article on understanding glaze stability at
http://www.frogpondpottery.com/glazestability/undglazestab.html
I have included a few quotes (with permission) from that article which make
good sense to me.
"What then are the goals we might set for ourselves. This is a complex
question and one for which their is no definitive answer at the present
time except for the regulated metals of lead and cadmium."
"But what about such metals as copper, manganese, cobalt, boron, lithium
and the other metals that usually end up in the form of metal oxides in our
glazes? Should we worry about them. I hasten to point out that there is no
evidence of anyone ever having been harmed by these metals leaching from a
pottery glaze."
"We believe it is a matter of good craftsmanship to make our glazes as
stable as possible and certainly durable enough to have a long life in
ordinary use and to avoid adding undesirable flavor to food served in them."
I agree that this is a complex question, and in the interest of avoiding a
painfully long post, let me just summarize. In the absence of any generally
accepted definition of "food safe", I too like the concept of good
craftsmanship. Our glazes are stable and durable-many have been in use at
Coyote for 15 years or more and are holding up beautifully.
The only difference I see in our approach to making well crafted glazes is
our starting point; while you said "For my part, I am going to continue to
try to learn how to make my glazes as stable as possible while still being
attractive.", I would say I'm going to make the most beautiful and
interesting glaze I can, and then if needed adjust it to be suitably stable
and durable. I believe we might end up in the same place, we just start
from opposite ends.
Thanks,
Martin Butt
Coyote Clay & Color
coyoteclay.com
Date: Thu, 3 Aug 2006 17:21:23 -0400
From: John and Judy Hesselberth Subject: Re: food safe on commercial glazes?
Hi Brenda,
It's not possible to answer your question definitively. The law only
requires minimal leaching of lead and/or cadmium to be 'food safe' --
lead and cadmium free are not required. You can find the specific
standards on the FDA site or on my web site at:
http://www.frogpondpottery.com/glazestability/undglazestab.html
California has somewhat stricter standards.
There are glazes being sold by companies who know what they are doing
and care. There are also glazes being formulated by those who don't
know or care or are content to meet the minimum standards of the law.
It is difficult to tell which is which. Asking them directly is the
only possible way to tell--and if you get an evasive answer, beware.
Two companies that have responded best to my questioning on this
subject are Spectrum and Opulence. Spectrum has their glazes tested
for leaching and submits the results to an industrial toxicologist at
Duke University. They have told me they will share the results with
people who ask. Opulence has their glazes reviewed by an industrial
glaze consultant who, I believe, knows what he is doing. Although I
haven't met him, he has an excellent reputation.
I have invited other companies to tell us their testing procedures
here on Clayart. The silence is deafening. I have to conclude they
don't do any, but I would love to have to eat those words. So I raise
the question once again. Tell us, glaze manufacturers who monitor
Clayart, what your procedures are. Inquiring minds want to know.
Brenda, I hope this helps you. It is one of the many reasons I
decided to mix my own glazes--I really wanted to know how they would
perform.
Regards,
John
On Aug 3, 2006, at 1:01 PM, Brenda Phillips wrote:
> Dear wise ones,
> Does 'food safe' on commercial glazes mean that the glazes do not
> have lead or cadmium or does it include other safeguards against
> leaching?
> Is there a standard beyond lead and cadmium or is it different for
> each company?
>
> Thanks,
> Brenda from Manchester, CA
Paul Lewing on sat 5 aug 06
On Aug 5, 2006, at 3:32 PM, Martin Butt wrote:
This turned up one glaze that
passed the vinegar test, but showed discoloration from storing
coleslaw-why
coleslaw and not vinegar I can't tell you.
I seem to recall that vegetables in the cabbage family have a lot of
sulphur in them. Could this be the reason?
Paul Lewing
www.paullewingtile.com
John and Judy Hesselberth on sun 6 aug 06
On Aug 5, 2006, at 6:32 PM, Martin Butt wrote:
> I'm glad I read clayart to the bottom yesterday! I'd hate to be
> lumped in
> with glaze companies that don't know or care, because I do care
> about our
> customers safety and satisfaction. In addition to being the
> originator of
> Coyote Cone Six Electric Glazes, I have been a potter for 30 years;
> I want
> my pots to be safe and to stand up well to everyday use, and I'm
> sure my
> customers expect the same.
Hi Martin,
What a pleasure to have to eat my words with respect to Coyote Cone 6
Glazes. Our conversation off line and your response to Clayart gives
me high confidence that you are paying attention to this issue and
are doing your best to make sure your glazes are suitable for their
intended use. You are obviously going well beyond the minimum
requirements!
I also know you have some really beautiful glazes and, therefore,
confirm the statement I have made a number of times that having
stable, durable glazes results in very little compromise of aesthetic
choice.
Thanks for responding. It is always a happy event when a supplier
demonstrates, by responding on Clayart, that they are doing their
best to supply quality products and care about their customers.
The cole slaw is a puzzle--I may have to experiment a bit with that.
Regards,
John
Ivor and Olive Lewis on mon 7 aug 06
Dear Friends,
Coleslaw, in addition to Cabbage, Onion, and Shredded Carrot, is =
moistened with a cold sauce devised from Egg Yolk, Olive Oil, with White =
Vinegar or Lemon Juice. No doubt to enhance taste it will contain a dash =
of Common Salt.
So ceramic corrosion is to be expected.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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