Scott Hunnicutt on sat 28 oct 06
I have always been told that copper red glazes are not food safe. Is this
true? I have been looking at several of the copper red recipes that I have
and they all contain very small amounts of copper carbonate. Like
around .3-5% of copper carb. Does this small amount of copper carb make
the glaze not foodsafe?
L. P. Skeen on sat 28 oct 06
Scott, I believe you're confusing the low fire red glazes made with =
lead, (a la Ben Owen, III in Seagrove) with copper reds. NOT the same =
thing at all.
Lead =3D poison, for the most part.
L. P. Skeen, Summerfield NC
Get your 2007 Clay Lover's Calendar at =
----- Original Message -----=20
From: Scott Hunnicutt=20
I have always been told that copper red glazes are not food safe. Is =
Janine Roubik on sat 28 oct 06
I thought that cone 10 copper reds were not considered the best for food, not because of the copper (copper is in my vitamins and some cooking pans), but because they are usually low alumina and may erode over time with dishwasher/acids. But I'll have to admit, I did make a few mugs w/ my copper red, just because they're pretty.
But yeah, low-fire reds w/ lead or cadmium a definite no-no. Unless the cadmium is one of those encapsulated stains, and you've had it tested under your firing conditions for release.
And that's all I know ; )
"L. P. Skeen" wrote:
Scott, I believe you're confusing the low fire red glazes made with lead, (a la Ben Owen, III in Seagrove) with copper reds. NOT the same thing at all.
Lead = poison, for the most part.
L. P. Skeen, Summerfield NC
Get your 2007 Clay Lover's Calendar at http://www.living-tree.net/calendar.htm
----- Original Message -----
From: Scott Hunnicutt
I have always been told that copper red glazes are not food safe. Is this true?
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Daniel Semler on sat 28 oct 06
What's in the glaze ? Copper is hard to keep in a glaze and 5% =20
seems like a lot for a copper red - did you mean 0.3 - 0.5 ? At lower =20
percentages it should not be a big deal. A number of high fire copper =20
reds contain some barium carbonate. David Hendley did an article in CM =20
one time on removing it. The glazes looked the same without it. Of =20
course they don't contain much of it usually. I have had a barium =20
containing copper red leach tested and it didn't leach enough for me =20
to worry about - please don't take that as a general statement on =20
copper reds with barium carb. I've also done some tests subbing barium =20
with strontium in copper reds and that seems fine too.
You can easily get this tested if you want. Actually finally, after =20
turning the place upside down, before looking in the folder marked =20
Glazes, I found the leach test. It leached more copper than barium in =20
the standard test, and there's about 4.3% barium carb and only 0.5% =20
Snail Scott on sun 29 oct 06
At 02:20 PM 10/28/2006 -0400, you wrote:
> From: Scott Hunnicutt
> I have always been told that copper red glazes are not food safe. Is
Most copper reds have a relatively low oxide
content, and are decently durable glazes;
no reason I can think of to avoid them as
a class. Some particular recipes will be
below optimum stability, but even if they were
much less durable I doubt that they would be
seriously non-foodsafe. Most versions don't
have much 'bad stuff' to leach out.
Where have you heard that copper reds are
Ron Roy on sun 29 oct 06
There are some people who cannot have any extra copper (Wilson's disease) -
and for them the copper reds would be unsafe.
I think you may talking about stability - and that will differ a lot
between different copper reds. You would find the differences by leach
I would not be concerned about copper leaching from copper reds - there is
very little copper to start with.
As someone else mentioned - the lack of alumina may make some degrade in
the dish washer. Make two tiles of each copper red and leave one in the
dishwasher and compare it to the other one every few weeks - you will see
which are the more stable eventually.
>I have always been told that copper red glazes are not food safe. Is this
>true? I have been looking at several of the copper red recipes that I have
>and they all contain very small amounts of copper carbonate. Like
>around .3-5% of copper carb. Does this small amount of copper carb make
>the glaze not foodsafe?
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