Cindy Strnad on thu 12 oct 00
Hi, Bass.
Thanks for your post on copper. Let me see if I'm understanding you
correctly. It seems to me you're saying that copper fumes (particularly
copper sulfate) and dust are dangerous, however, the copper compounds used
by potters (copper carbonate, and copper oxide?) are not considered a hazard
either to the potter, or to the user of the pottery. Is that accurate?
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Martin Howard on thu 12 oct 00
Edouard shows up here something that is a great worry for many potters and
perhaps we worry too much.
We try to keep our glazes so that they are **food safe**. OK, that is good.
So we try to keep away from lead, uranium, barium etc.
We can read about copper being poisonous. But it is an element which we need
as trace in our diet. We still make great efforts stop it leaching from our
glazes.
So, can anyone actually tell us how much is needed in our diet and how much
we are likely to get from pots glazed at different percentages of let us say
copper for starters?
Just received and devoured Ian Currie's Revealing Glazes. Very quick
delivery and excellent book.
But here I am making plates, bowls and mugs for the Esperantists of East
Anglia, using a 3% copper glaze which gives the green colour for Esperanto,
and Ian's book suggests I might be poisoning them. Ouch.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
Edouard Bastarache on thu 12 oct 00
COPPER & COMPOUNDS
Copper is a metal used as an alloy in brass and bronze, as a component in
some solders, in pigments such as emerald green, in ceramic glazes, and a=
s
a salt in the lithographic process.
Copper is an essential metal and the daily requirement has been estimated
at 30 micrograms/kg of body weight for an adult.
The normal concentration of copper in blood plasma is 1 mg/liter.
The gastrointestinal absorption of soluble copper is regulated by the nee=
d
and is usually around 50%; uptake may also take place after inhalation.
Elimination of copper is slow and takes place via bile.
The chronic accumulation of copper in the body is rare and occurs in
Wilson's disease caused by an inborn error of the copper metabolism
characterized by a diminished capacity to eliminate copper via bile.This
leads to secondary lesions in the liver and the brain.
The salts are irritants to the skin, eyes,and mucous membranes. Ingestion=
of
copper salts may cause vomiting, diarrhea, hemorragic gastritis, and
excessive salivation.
Copper sulfate has clinically (medicine) been used as an emetic. Vineyard
sprayers using a solution containing aqeuous copper sulfate developed
granulomatous and fibrotic lung lesions.Liver granulomatas containing cop=
per
have also been found in vineyard sprayers.Clinical liver disease is usual=
ly
not significant, but liver granulomas occasionally result in hepatomegaly=
,
necrosis and fibrosis.
Experimental studies in mice support that copper is an etiologic(cause) f=
or
lung fibrosis.
Inhalation of copper dust and fume results in irritation of the respirato=
ry
tract, ulceration and perforation of nasal septum, metallic or sweet tast=
e,
and in some instances, discoloration of the skin and hair.The inhalation =
of
metal fumes produced at high temperature, such as welding, may cause "met=
al
fume fever", an influenza-like(benign) illness.
Copper sulfate is also used in the whitewashing and leather
industry.Toxicity is primarily due to accidental and suicidal attempts, a=
nd
results in intravascular hemolysis, methemogloninemia, renal failure and
often death.
Remember clinical liver disease due to copper is not usually significant.
High copper content in drinking water and food may contribute to the
development of severe liver damage in infants.
Copper compounds used by potters are not considered hazardous as well as
for pottery users.Copper in glazes fluxed by lead compounds will leach mo=
re
lead.
Good studio housekeeping is always good practice. Avoidance of processes
generating unnecessary dust is also important and the wearing of an appro=
ved
dust mask when the exposure seems hazardous is also good practice.
REFERENCES :
1-Occupational Medicine,Carl Zenz, last edition.
2-Occupational & Environmental Medicine,Joseph Ladoue, last edition.
3-Hazardous Materials Toxicology, Sullivan & Krieger; last edition.
Hazardous Materials Used in Arts and Crafts,chapter 60,
Edouard Bastarache
Dans / In "La Belle Province"
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
-----Message d'origine-----
De : Martin Howard
=C0 : CLAYART@LSV.CERAMICS.ORG
Date : 12 octobre, 2000 16:55
Objet : Re: Copper glaze was: Black without manganese
>Edouard shows up here something that is a great worry for many potters a=
nd
>perhaps we worry too much.
>
>We try to keep our glazes so that they are **food safe**. OK, that is go=
od.
>So we try to keep away from lead, uranium, barium etc.
>We can read about copper being poisonous. But it is an element which we
need
>as trace in our diet. We still make great efforts stop it leaching from =
our
>glazes.
>
>So, can anyone actually tell us how much is needed in our diet and how m=
uch
>we are likely to get from pots glazed at different percentages of let us
say
>copper for starters?
>
>Just received and devoured Ian Currie's Revealing Glazes. Very quick
>delivery and excellent book.
>
>But here I am making plates, bowls and mugs for the Esperantists of East
>Anglia, using a 3% copper glaze which gives the green colour for Esperan=
to,
>and Ian's book suggests I might be poisoning them. Ouch.
>
>Martin Howard
>Webb's Cottage Pottery
>Woolpits Road, Great Saling
>BRAINTREE, Essex CM7 5DZ
>England
>martin@webbscottage.co.uk
>
>________________________________________________________________________=
___
___
>Send postings to clayart@lsv.ceramics.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
melpots@pclink.com.
John Hesselberth on thu 12 oct 00
Martin Howard wrote:
>So, can anyone actually tell us how much is needed in our diet and how much
>we are likely to get from pots glazed at different percentages of let us say
>copper for starters?
Hello Martin,
This is from one of my posts last Spring. It partly answers your
question. If you want to read the entire post, search under copper
leaching.
----
I once did a calculation of how long this leaching could go on. I don't
remember the exact numbers anymore; however there is enough glaze on a
typical piece of pottery for it to go on for a long time. For example,
if there are 10 grams of glaze containing 5% copper carbonate on the
inside of a mug, it contains about 0.3 gr of copper. If that leaches at
10 mg/l into, say, 200 ml of liquid in the cup you only leach out 2 mg
with each leaching. That gives enough copper (and/or glaze??) for 150
leachings. Of course the reality is that even if the cup leaches 10 mg/l
in the standard test, it will probably leach less than 0.5 mg/liter (or <
0.1 mg per cup of coffee) in normal coffee drinking use. That 0.3 grams
originally in the mug ought to be good for more than 3000 cups of coffee
at that rate. And far more if what you suggest is the actual case. And
of course, we now know we can make at least some glazes containing 5%
copper carbonate that leach significantly less than 10 mg/l in the
standard test.
----
The FDA recommended daily intake of copper is 2 mg/day.
The only way to really know what your mugs are doing is to have them
tested. If you don't have a local source I'll offer an opinion if you'll
send the recipe and the firing conditions. I have tested an awful lot of
pots for copper release at this point. I use it in my research on making
stable glazes because it is so hard to keep in a glaze. i know if I can
keep it in, I have a pretty good glaze.
Regards, John
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is, perhaps, still necessary to say that the very best glazes cannot
conceal badly shaped pots..." David Green, Pottery Glazes
Edouard Bastarache on fri 13 oct 00
Right Cindi,
1-The inhalation of metal fumes produced at high temperature,
such as welding, may cause "metal fume fever",
an influenza-like(benign) illness.
2-Vineyard sprayers using a solution containing aqeuous
copper sulfate developed granulomatous and fibrotic lung
lesions.Liver granulomatas containing copper have also
been found in vineyard sprayers.
3-Copper compounds used by potters are not considered
hazardous as well as for pottery users.
Later,
Edouard Bastarache
Dans / In "La Belle Province"
edouardb@sorel-tracy.qc.ca
http://www.sorel-tracy.qc.ca/~edouardb/
-----Message d'origine-----
De : Cindy Strnad
=C0 : CLAYART@LSV.CERAMICS.ORG
Date : 13 octobre, 2000 06:50
Objet : Re: Copper glaze was: Black without manganese
>Hi, Bass.
>
>Thanks for your post on copper. Let me see if I'm understanding you
>correctly. It seems to me you're saying that copper fumes (particularly
>copper sulfate) and dust are dangerous, however, the copper compounds us=
ed
>by potters (copper carbonate, and copper oxide?) are not considered a
hazard
>either to the potter, or to the user of the pottery. Is that accurate?
Right Cindi
Later,
>
>Cindy Strnad
>Earthen Vessels Pottery
>RR 1, Box 51
>Custer, SD 57730
>USA
>earthenv@gwtc.net
>http://www.earthenvesselssd.com
>
>________________________________________________________________________=
___
___
>Send postings to clayart@lsv.ceramics.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
melpots@pclink.com.
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