John Hesselberth on sun 8 aug 99
Ray Aldridge wrote:
Yes, copper is confusing. There are no clear answers yet. There are
currently some tests going on at Alfred to determine how much really
leaches into food at normal use conditions (things like coffee, tomato
sauce, orange juice, milk). I've used a glaze for these tests which
contains copper, manganese and cobalt. I, too, believe the leaching test
is overly vigorous; however Monona says it is a pretty close simulation
of use with acidic foods. She told me that is how the test was
established. I couldn't find the data to demonstrate that in my
literature search. I'm from Missouri on this (apologies to our non-U.S.
members-- the state of Missouri has adapted the slogan "show me"-- they
are said not to believe anything until they've personally seen it proven,
or in this case personally seen the data). So, we'll see that data soon
when the tests I mentioned above are complete. And if the leaching test
is a close simulation, why has the lead standard for pottery been set at
7-30 times the allowable drinking water level? Political pull??
Wouldn't be the first time I guess.
We currently know a couple things about copper. It makes food taste
bitter at 10 mg/l or less. That certainly is not something I want to do
and I doubt you do either. That should be a pretty quantifiable upper
limit IF the leaching test is a reasonable simulation of what happens
with food (see above). The upper limit for drinking water is 1.3 mg/l.
I haven't succeeded in tracking down the scientific basis for that
standard. If anyone can point me toward it I would appreciate it. I'm
not sure one actually exists--it may have been established like limit
formulas were--observing what was out there at the time the standard was
established. If we were to ratio off the lead standard that would say
10-40 mg/l (depending on the type of vessel) in the leaching test would
be OK for copper. I can show you very attractive copper containing
glazes that leach more than 40 mg/l and a lot that leach over 10 mg/l. I
conclude we should be careful with copper until we know more. After all,
we are liable for the products we sell. I currently try to stay below 10
mg/l with my copper containing glazes. And it is possible to make very
attractive copper green glazes which leach <10 mg/l. It is also pretty
easy to make a glaze which leaches a lot more. The only way to know at
present is to test and that is what I do.
As to your copper water pipe question, while I've never measured it, this
is a very different situation. Water normally is in the copper section
of water piping only a few seconds. Even if it is there overnight it is
at room temperature. Also potable water is normally a little on the
basic side--if it is acidic it is nowhere near as acidic as, say, orange
juice or tomato sauce. If you are dealing with a tomato sauce in a
casserole dish being heated in a oven for an hour or more you would have
the potential to extract substantially more--maybe even several orders of
magnitude more--copper from a poorly designed copper-colored glaze than
you would from a copper pipe through which water is running.
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: email@example.com web site: http://www.frogpondpottery.com
"It is time for potters to claim their proper field. Pottery in its pure
form relies neither on sculptural additions nor on pictorial decorations.
but on the counterpoint of form, design, colour, texture and the quality
of the material, all directed to a function." Michael Cardew in "Pioneer
Ray Aldridge on tue 10 aug 99
At 07:05 PM 8/8/99 EDT, you wrote:
>As to your copper water pipe question, while I've never measured it, this
>is a very different situation. Water normally is in the copper section
>of water piping only a few seconds. Even if it is there overnight it is
>at room temperature. Also potable water is normally a little on the
>basic side--if it is acidic it is nowhere near as acidic as, say, orange
>juice or tomato sauce. If you are dealing with a tomato sauce in a
>casserole dish being heated in a oven for an hour or more you would have
>the potential to extract substantially more--maybe even several orders of
>magnitude more--copper from a poorly designed copper-colored glaze than
>you would from a copper pipe through which water is running.
I should probably be clear that I haven't used copper bearing glazes for
years, not since I became disenchanted with copper reds, which as you know
generally have very small amounts of copper.
And I understand what you're saying, but in the spirit of beating dead
equines: That tomato casserole might only be cooked once a week, and the
portion would usually be smaller in volume than one glass of water. If we
do the healthy thing, we'll be drinking 6 glasses of water a day (I'm
drinking more because there's no AC in the pottery shed and it's summertime
on the Gulf Coast). That's 40 times the amount of water as lasgna, so if
the water limit is 1 mg/l then the casserole would have to leach 40 mg/l to
be in the same realworld class as the amount we might get from an
"acceptable" water level.
Add to that the information that copper is not retained in the manner that
other "heavy metals" but is eliminated from the body over the course of
At any rate, my opinion, which admittedly isn't worth anything, is that
copper leaching in reasonably normal non-lead glazes is not a significant
threat to health.
Fredrick Paget on thu 17 may 01
Copper cooking ware should be coated inside with pure tin metal. There are
companies that do this for restaurants etc. Look in the phone book yellow
pages for tinning or retinning.
I once bought a copper yogurt bowl from a Turkish coppersmith in Ismir and
he tinned it in my presence before finishing the deal. He heated it on his
forge and wiped around inside it with a fluxing material then sprinkled on
tin granules, let the tin melt and wiped it around the inside with a rag.
Result was a nice shiny pure tin coating that lasted for years.
A tea kettle would probably require acid cleaning and electroplating to
coat the inside.
If you have a tea kettle that was used in a hard water area the inside is
probably coated with a nice scale and who knows what is under it? I have no
idea whether the copper would leach through the scale.
>Not altogether unrelated to copper glaze discussion: I have a lovely, very
>old Brittish 100% copper tea kettle. I've polished it to like new condition.
>Now, is there any danger in using such a kettle for regular tea preparation?
From Fred Paget, Marin County, California, USA
Roger Bourland on thu 17 may 01
Not altogether unrelated to copper glaze discussion: I have a lovely, very
old Brittish 100% copper tea kettle. I've polished it to like new condition.
Now, is there any danger in using such a kettle for regular tea preparation?
Ababi on fri 18 may 01
If you would see, usually copper pots, are covered in there inside, with
another metal. Even the nonscientific small manufactures, in my region,
learnt not to use the copper pot as it is.
----- Original Message -----
From: "Roger Bourland"
Sent: Thursday, May 17, 2001 4:49 PM
> Not altogether unrelated to copper glaze discussion: I have a lovely, very
> old Brittish 100% copper tea kettle. I've polished it to like new
> Now, is there any danger in using such a kettle for regular tea
> Send postings to firstname.lastname@example.org
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
> Moderator of the list is Mel Jacobson who may be reached at
Edouard Bastarache Inc. on wed 31 mar 04
Acute Toxicity :
Gastrointestinal Tract :
Because copper is an essential element, toxicity is uncommon, as with =
all essential elements.=20
Most reports of acute toxicity are from suicidal attempts from ingesting =
copper sulfate. However, death is rare, owing to copper sulfate's emetic =
"Ils sont fous ces quebecois"
clennell on wed 14 apr 04
While some of you are debating copper in Oribe i just ordered some copper
ribs from Chris Henley. I asked him why he made copper ribs and here is the
Ah yes...why copper?...well, years and years ago, I did a short stint as
piece-work thrower for a local guy named Brent Bennett...he produced lamp
bases, ash urns, hurricane lamps, and a whole line of stuff that he sold
through a designer to hotels....I digress.....Brent wanted me to use his
ribs...they were copper and brass....I found that with the copper ones you
could anneal the thing, bend it to the curve I needed to reproduce, then
tap, tap, tap it lightly with a hammer on a hard surface to work harden it
and it would stay in that shape.....when you moved on to another shape, you
just annealed it again and re-shaped it....I would imagine that, since no-
one else has bothered to do this, it hasn't caught on.....also, I had one
order for copper ribs when I first started, so I just put out the
offer...haven't a clue about the why anyone else would use them. I shy away
from orders for those really thin steel ones...the stock is expensive and
that stuff is like working with ginsu knives. Besides, the big boys can
punch out those things by the thousands for next to nothing.
Here is guy that knows materials and process. i support that! If I didn't
spend enough money in the US on pots I have to come home and spend more on
Tony and Sheila Clennell
Sour Cherry Pottery
4545 King Street
CANADA L0R 1B1
bill edwards on thu 12 may 05
Lee, you made a good point. Many of the same materials
are materials found in Nature. We have limits as to
how much we can handle and each human body is
different. Copper in some people just simply won't
work because they cannot use the material in the same
manner a healthy body may under different
circumstances. This can be said for iron too and
several other materials many of us refer to as
The limits that are known are already set and those
are done most often via drinking water standards.
Testing to that degree is the best possible way to
make an accurate determination and even then that
means it is the most leachate that could be pulled
from a specimen within a determined amount of time. So
we go back to....
Check at home - Use lemon or perhaps vinegar for
several days. Its acidic. If it pulls color, there's
some issues with the mixture that may be easily
remedied. Possible a heat related problem from poor
melt. Raise the silica level, change some materials
around and fire accurately. Then when you are
satisfied, a lab can give you the best scientific
evaulation possible if they are certified. Their
business and name implies to me they are within the
grasp of regulation and understand the methods well
and how to carry them out. We don't even need to talk
about the toxicology of the product unless your end
use is to sell the glaze in powder or liquid form. A
lab and a toxicology report are different and provide
much differnt information regarding proper use. The
lab will give you the information needed to determine
if you have materials leaching out beyond the norms
based on consumption, toxicology determines damages
and how this compound of chemical effects the human
body and assigns a danger or non-dangerous labeling or
accesses potential for damages. Chronic means over the
long haul and can still be just as deadly as a toxic
accute dose, it just takes much longer and the
suffering still leads to the same end.
Copper pipes are often still used in water systems. I
do mean often! We can continue this on forever and we
do need to discuss the dangers, but we don't need to
see home grown toxicologists ruling the roost to boost
whatever it is without proper credentials or in the
very least, a valid reason as to why they deem their
statements much more worthy than the next? This group
lost some very great toxicologists and lab experts
that used to be here because of the same crap coming
from a few who would argue with a sign post on every
Ed is still around and his experience is vital to the
group. BUT.... Often there are a few who want to argue
with a toxicologist that aren't schooled on the
subject and have made themselves poster children for
the level and degree they haven't yet earned. I agree,
foolishness is dangerous but most can rest assured
that we have seen very few of our potters falling off
like flies from all these chemicals. If they were we'd
all be in a blazing panic and throwing out materials
Let us learn and be a close group and let it be known
that I deeply care for all of our people. But it is
time we worked more as a team instead of pissing
contests to see who can sell the most books, or muster
up better marketing for a product. We have been there
and done that and are experts for certain on that end
of the stick.
Please take note - I am not mad. I care for all people
and wish everyone whatever their dreams are. I do wish
it was much more inclusive and not as exclusive to
some people who try to post to this group. I have been
here for years and it doesn't bother me but based on
the multiple mails I get, it does bother others who
could offer something worthy to our group. Be
peaceful, live, love and laugh a little!!!
Edmar Studio and Gallery
Yahoo! Mail Mobile
Take Yahoo! Mail with you! Check email on your mobile phone.
Lee Love on sat 14 may 05
bill edwards wrote:
>Ed is still around and his experience is vital to the
Of course he is around. :^) Please sign on to his humor list, if you'd
Edouard is very level headed on the subject of glaze materials and
toxicology. Check his webpage out related to copper:
From the recent studies, I would say the the antibacterial properties
of copper plumbing far outweighs any hazards. As someone else pointed
out, the biggest hazard in copper plumbing is the lead solder, but if
you know what you are doing, any contamination can be almost nil.
Plastic plumbing does not have the same antibacterial qualities.
As I mentioned previously, originally, the concern about copper was
related to the solubility copper created in lead based glazes. But this
concern, somehow, has been used to cause concern about copper by itself.
If you read below, toxicity related to copper is almost unheard of. The
few medical cases that we know of , as Edouard says, is from people
trying to commit suicide by ingesting copper sulfate. Copper deficiency
is far more likely to be a problem.
Steve says some people are sensitive to copper. Roy says he is sensitive
to iron. Some people are sensitive to peanuts. When you have unusual
sensitivities, you need to look out for yourself. It would be ridiculous
to ban peanuts from the world, just because some people are allergic to
them. It is best to use some common sense.
I include some quotes from Edouard's article:
The daily copper requirement has been estimated at 30 micrograms/kg of
body weight for an adult. After ingestion, maximum absorption of copper
occurs in the stomach and jejunum.
Copper is bound initially in the serum to albumin and transcuprein, then
later is bound more firmly to ceruloplasmin, which binds more than 75%
of circulating copper.
Absorption is increased in copper deficiency and is impaired in
Copper is distributed throughout the body but is stored primarily in
liver, muscle, and bone.
The normal concentration of copper in blood plasma is 1 mg/liter.
In all mammals, copper is an essential trace element involved in :
-fundamental cellular respiration,
-free radical defense,
-connective tissue synthesis,
Absorbed copper is initially bound to albumin and is transported from
the gastrointestinal tract to the liver where it is transferred to
Urinary excretion is enhanced by increased molybdenum intake, cirrhosis,
and biliary obstruction.
Copper is eliminated principally through the feces after excretion into
the bile. Urinary excretion of copper is low in humans.
Healthy adults have urinary concentrations of less than 100µg per 24 hours.
III-Symptoms and Clinical Signs :
A-Acute Toxicity :
1-Gastrointestinal Tract :
Because copper is an essential element, toxicity is uncommon, as with
all essential elements.
Most reports of acute toxicity are from suicidal attempts from ingesting
copper sulfate. However, death is rare, owing to copper sulfate's emetic
李 Lee Love 大
in Mashiko, Japan http://mashiko.org
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Mike Gordon on fri 19 aug 05
my question to you is what can I melt all this copper in? what fire
can I use to get it hot enough to do this?
Travis, Copper melts at 1981 Degrees F. With the amount of copper you
are talking about you will need to do a lot of melts. You need a
crucible to melt it in and ingot molds to pour it into after it is
melted. A lot of work! Why not contact a local bronze foundry and sell
it to them, it might be a higher price than a recycle place. I think
the price of copper is on the rise also. Good luck, Mike Gordon