John Hesselberth on tue 13 apr 04
On Monday, April 12, 2004, at 03:45 AM, Ivor and Olive Lewis wrote:
> Visual evidence suggests that if Copper oxide is soluble in a silicate
> melt then it is to a limited degree, and the values have yet to be
> established.
Hello Ivor,
I'm delighted to see you so intrigued by the copper questions. I wish
you well in figuring it all out! I would estimate that the solubility
of copper in a silicate melt in somewhere around 1-2% based on a large
number of leaching tests. That must be quite variable, though,
depending on what else is in the melt. At times I see glazes with 4 or
5 % copper (as the carbonate) that have very low leaching. That is if
the leaching results from lack of high solubility in the melt. I am
coming to believe that this is not a simple question of solubility in
the melt.
I would like to point out another interesting facet of its behavior.
Copper originally got a bad reputation in the scientific glaze
literature, not because it leached, but rather because it increased
the leaching of lead. That was determined about 75 years ago. In fact,
I'm not aware that anyone tested for the leaching of copper itself in
any significant way until I started doing it several years ago. At
least I've never seen any reports of that type in the literature. As
you know, all of the leaching analyses that were done back then were
done by very laborious wet chemistry analytical techniques--so people
looked only at lead. I started studying copper because of an
observation that glazes that faded in use often contained copper
combined with the knowledge from the literature study I had done which
showed the lead/copper problem. Of course in today's world it is a very
easy analysis to look for copper--or anything else for that matter.
So the "copper puzzle" may be a more complex issue of copper causing
some fundamental shift or change in the structure of a silicate melt
which "loosens up" the whole structure and makes it more prone to
attack by acids.
It is a fascinating subject for which there seems to be no easy answer.
It is clearly material for a doctoral level thesis in the field of
ceramic science. With the analytical tools available today I bet it is
a solvable puzzle. In the meantime, though, we do know how to minimize
copper leaching and how to test to be sure of our results. So I see no
reason not to use copper for glaze formulators who are careful in what
they do.
Regards,
John
http://www.frogpondpottery.com
http://www.masteringglazes.com
Craig Edwards on tue 13 apr 04
John: Thanks for your nice post on the "Copper Puzzle". It is truely
worth and is ripe for some deeper investigation. Why copper is not
receptive to the silicate melt might be easier to understand if we look
at copper as a coinage metal. One that can stand alone on the elemental
level. This suggests to me that copper has a certain predispostion to
be by itself. Just a thought. I wish that I had more time to think about
this. With the spring wood-firing and a trip to Korea-Japan, I'm afraid
that I'll have to be a pedestrian of this one. I am thoroughly enjoying
this thread. thanks
Craig Edwards
New London MN
>
Lee Love on wed 14 apr 04
John Hesselberth wrote:
> I would like to point out another interesting facet of its behavior.
> Copper originally got a bad reputation in the scientific glaze
> literature, not because it leached, but rather because it increased
> the leaching of lead.
This is a good point John. Originally, the concern was related
to the lead content in the old low-fired glazes.
MacKenzie developed his boro-lithium green, trying to get a green
with the brightness of the traditional lead greens, but with safer
materials. Just before I left St. Paul, inspired by MacKenzie's
glaze, I was developing boro-lithium green, brown and amber, but at
a higher temp than MacKenzie's glassy green (If I recall correctly, his
glaze is cone 4-5. Mine was cone 6.) The next step was to try and
make a lead-like yellow. I was doing this looking forward to making
leadless slipware. I don't have spodumene or Gerstley Borate here, so
if I continue, I will have to start all over.
My other interest in electric fire was majolica and I was having
good success with Linda Arbuckle's majolica and colorants. If I were
doing electric today, these are the two routes I'd follow. I still
hope to do woodfired majolica-like lowfire ware, like the old French
Jaspe ware.
Lee In Mashiko
http://mashiko.org
Lee Love on wed 14 apr 04
Craig Edwards wrote:
> level. This suggests to me that copper has a certain predispostion to
> be by itself. Just a thought. I wish that I had more time to think about
> this. With the spring wood-firing and a trip to Korea-Japan, I'm afraid
> that I'll have to be a pedestrian of this one. I am thoroughly enjoying
> this thread. thanks
Here is a new spin on "leaching copper." I have made my sushi
platters to cover a large Italian made terracotta flower pot I bisque my
Mashiko kaki in. A lady saw a temmoku and kaki platter and asked if
I could do it in Nuka and Sage, so I did. She wanted it for ikebana.
(My Japanese customers think may casseroles are ikebana pots too. :-)
But the size to cover the kaki pot could only go on the top shelves
in the woodkiln, because it was to big to fit between the props. But I
hit Seger 11 to 12 at the top and the Sage ran and stuck to the
shelves a little. That's why I got to keep it. I've made some
smaller ones I can put lower in the kiln, in the seger cone 8 area.
But the ikebana lady got me thinking: My wife always always
puts a copper coin in the bottom of a vase to hold cut flowers. She
learned years ago, that the copper in the water keeps the flowers alive
longer. Got me thinking, maybe a copper glaze should be put inside
all functional vases, but you would have to make sure there was some
solubility from the copper. Save your pennies for the piggy bank.
Could be a new marketing gimmick! I mean, nobody cares if a vase is
oven proof or microwave safe. ;-)
Lee In Mashiko, Japan http://mashiko.org
Ivor and Olive Lewis on wed 14 apr 04
Dear Craig and John,
The coinage metals all have anomalous electron shell structures. The
are also among the most "Metallic" of all the metals possessing
exceptional degrees of electrical and heat conductivity. I understand
this is because their electrons do not stay close to the nucleus or
some similar reason but tend to readily migrate under the influence of
temperature difference and differences in electrical potential..
The copper/lead nexus may be due to the formation of intermetallic
compounds of the form xPb.yCu (see the metal phase diagrams) or a
chemical called Copper Plumbate Cu2O.PbO (see the oxide phase
diagrams). I would imagine this to be freely soluble in all mineral
acids and possibly in weak organic acids.
There is so much we do not know which, as you say, would be resolved
using the new tools.
Decoration with copper glazes Keep them out of the wells of plates and
dishes, but reserve them for the flanges.
Best regards,
Ivor Lewis. Redhill, South Australia
----- Original Message -----
From: "Craig Edwards"
To:
Sent: Wednesday, 14 April 2004 3:07
Subject: Re: Copper leaching/solubility
> John: Thanks for your nice post on the "Copper Puzzle". It is truely
> worth and is ripe for some deeper investigation. Why copper is not
> receptive to the silicate melt might be easier to understand if we
look
> at copper as a coinage metal. One that can stand alone on the
elemental
> level. This suggests to me that copper has a certain predispostion
to
> be by itself. Just a thought. I wish that I had more time to think
about
> this. With the spring wood-firing and a trip to Korea-Japan, I'm
afraid
> that I'll have to be a pedestrian of this one. I am thoroughly
enjoying
> this thread. thanks
> Craig Edwards
> New London MN
>
> >
>
>
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Ivor and Olive Lewis on thu 15 apr 04
Dear Lee,
One of the clues to copper ore deposits in this region of Australia
was the lack of vegetation in areas where the soil was rich in copper.
Because of its toxicity Copper kills soil bacteria and subterranean
fungi, essential for the well being of many native species.
The copper coin, rather than keeping the flowers alive may be killing
bacteria and microscopic invertebrates which would cause the stems to
decay and promote death of the display.
Best regards,
Ivor Lewis. Redhill, South Australia
Bobbruch1@AOL.COM on thu 15 apr 04
Lee In Mashiko (glazing for a wood firing) writes:
The above warning is valid.=A0=A0 It is a much better=20
way to approach these issues than saying that=20
Raku, earthenware, oribe and sage are not=20
functional ware.=A0 =A0 =A0 Or that all functional ware=20
must be microwave and dishwasher safe.=A0=20
We need to make safe work but we also
need to educate people about the proper=20
use of traditional and folk
pottery.=A0 =A0 =A0 In our mad rush for progress,=20
we need not trample and loose what is=20
good from our heritage and our past.
Lee - try to start dealing with reality!!!!!=20
just because you are trying to pretend=20
that that you are a 15th century Japanese=20
potter is not an excuse for playing in never
never land when you deal with other people.
If you want to assume that your customers
will know the proper way to use your work -
and that it will never be misused - even when=20
that customer sells or gives your pot away -
then you must still believe in the tooth fairy.
If you don't care - well then, why not just say
that? But to defend your outmoded views with:
"I'm living in a pretend world of the most
wonderful ancient culture ever and I don't want=20
anyone to disturb that fantasy" - does a disservice
to the other 3999 Clayarters who are trying to
learn some new information from Ron et al.
JMHO - Bob Bruch
Edouard Bastarache Inc. on thu 15 apr 04
Lee and Bob,
people here tend to forget that only 2 metals are regulated in all
of the "modern" countries when it comes to the safety of glazes
intented to be used on utilitarian wares.
It is not because a few persons, members of this list, want to pass their
own laws that we have to follow them.
As John H. has said there is a difference between "stable" and "toxic"
in dealing with the behaviour of glazes.
Let us not forget that there are myriads of specialists in different fields
of health and safety who work full time or act as consultants for a myriad
of governements throughout modern countries.
It is not only a matter of being "politically correct or not", it is mainly
a matter of health sciences.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
----- Original Message -----
From:
To:
Sent: Thursday, April 15, 2004 7:56 AM
Subject: Copper leaching/solubility
Lee In Mashiko (glazing for a wood firing) writes:
The above warning is valid. It is a much better
way to approach these issues than saying that
Raku, earthenware, oribe and sage are not
functional ware. Or that all functional ware
must be microwave and dishwasher safe.
We need to make safe work but we also
need to educate people about the proper
use of traditional and folk
pottery. In our mad rush for progress,
we need not trample and loose what is
good from our heritage and our past.
Lee - try to start dealing with reality!!!!!
just because you are trying to pretend
that that you are a 15th century Japanese
potter is not an excuse for playing in never
never land when you deal with other people.
If you want to assume that your customers
will know the proper way to use your work -
and that it will never be misused - even when
that customer sells or gives your pot away -
then you must still believe in the tooth fairy.
If you don't care - well then, why not just say
that? But to defend your outmoded views with:
"I'm living in a pretend world of the most
wonderful ancient culture ever and I don't want
anyone to disturb that fantasy" - does a disservice
to the other 3999 Clayarters who are trying to
learn some new information from Ron et al.
JMHO - Bob Bruch
____________________________________________________________________________
__
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.
Bobbruch1@AOL.COM on fri 16 apr 04
Lee Love writes:
Bobbruch1@AOL.COM wrote:>that?
But to defend your outmoded views with:
Lee, I don't have enough knowledge
on the subject to have a view.
Having been on this list for a few years -
and having a view of John and Ron's book -
I DO have considerable amount of respect
for their research and opinions.
It "seems" as if they are
trying to tell US something - and,
if you choose to ignore that, it is
certainly your privilege. You appear to
choose to do more than ignore it -
you publicly decry their opinions.
And, you offer no research or proof
to back up your widely opened mouth -
just the blither of your opinions -
which are worth about as much as mine -
very little.
Ron's comments are not only opinions,
they are backed up
by YEARS of research.
Based on that alone, they seem worthy
of consideration - something that you
apparently are not able to give them.
If you have never done the research yourself,
perhaps you should listen.
If you are not willing or able to listen
to those more qualified to discuss the subject
than you are,
perhaps you should consider keeping quiet.
my guess is that most people on this list
would want to learn from some one
with the most knowledge
and not from someone
with the biggest mouth.
If you done some research,
then you should present it now.
If you have not done
any work in the area,
then you could try the
novel approach
of listening to someone
who knows more than you do.
Bob Bruch
mailtoandrew@FSMAIL.NET on fri 16 apr 04
Dear All,
I ve been amazed at some of the comments to this post.
What has =93ethnocentric perspective=94 to do with safety? Apart from some
minor external differences the human body is the same the world over.
=93Politically correct?=94 A truly odd accusation when health, and the real
dangers that can be posed to it are being discussed.
Why is earthenware even mentioned? It is a type of body, and the
discussion is about glaze or decoration that is applied to the substrate.
To quote =93...the use of pottery in America is somewhat limited.=94 How? Wh=
at
are other countries supposedly doing?
=93... in Japan, the aesthetic is not hobbled by industry criteria...=94 Wha=
t
is this criteria? That users are not poisoned? Anyway the discussion is
about safety not aesthetics!
Claiming tradition some how allows the sale of potentially dangerous
products is truly frightening.
And the suggestion about teaching customers is naive. Some may be
interested in the background to a particular decoration and the
applications for which it is unsuitable. Most will not, and to a point
neither should they expected to be ... items that are sold for food use
should be safe.
Is it feasible to so narrowly restrict the use of food vessels? What does
one say ... that it is OK to place food of pH 7 for 1 hour, and anything
more will leach toxins?
Hearing something like this will lead many, understandably, to assume the
ware is not worth the risk and decide not buy. This will also help
establish the impression of dangerous products.
Also as was noted by an earlier post what happens when ware gets given
away or sold by the original customer?
Yes tradition and the work of earlier potters can be an inspiration but we
should not be hampered by them. My taste is not for Hamada or Leach, in
fact I consider much of it rather ugly. Am I wrong... no that is my taste,
and equally I would not criticise anyone who feels otherwise. Aesthetics
and taste are personal and subjective. However science and technology are
not, and it is to these that one must look when considering the protection
of health.
From another related post was =93This scare mongering is not advancing
studio ceramics=94 Wow ... it is by ignoring the issue and not discussing it=
that has the real danger of seriously damaging the craft, and peoples
health. Hide from it, ignore it, refuse to accept it or consider it
irrelevant to craft and traditional potters and the likely outcome at some
point is a headline case of poisoning. The result could well be
authorities imposing stringent regulations. Not sure? Talk to industrial
manufacturers about why Californias Proposition 65 was introduced, and its
consequences.
There have been cases where serious and irreparable damage has been caused
to people by the use of bad ceramic ware, and not just from Mexico, but
from ware made in North American and European studios. This is not scare
mongering it is concerned, and hopefully intelligent, debate.
Good ceramics can be beautiful, functional and safe.
That s my rant over, and apologies if it may have offended anyone as that
is not my intention.
Regards,
Andrew
Lee Love on fri 16 apr 04
Bobbruch1@AOL.COM wrote:
>that? But to defend your outmoded views with:
>
>
>
Bob,
Your ethnocentric perspective is a good example of why we need
to look outside our particular culture's point of view. Other cultures
and other times in history can inform us. If we could start
understanding this in America, we would better be able to take our place
of leadership in the world. What are YOU afraid of?
Lee In Mashiko
Lee Love on fri 16 apr 04
Edouard Bastarache Inc. wrote:
>It is not only a matter of being "politically correct or not", it is mainly
>a matter of health sciences.
>
>
Nicely said Eduourd! It is a matter of education, the free exchange
of information, and approaching saftey in a rational manner.
To me, the bright red flashing warning sign, that people are
supporting "politically correct" views, is when they categorically
dismiss whole areas of work that they don't have any understanding
about: Raku not functional? Sen No Rikyu and all the tea masters are
wrong. Eathernware unsafe? I will not give up Linda Arbuckle
majolica. Copper glazes not functional? I refuse to smash my
glassy green MacKenzie bowl. Won't pass the microwave test?
Please, give me all your mat Nuka Shoji Hamda pieces.
Of course we can always learn from science, but we can
also learn from how work is traditionally used. Our understanding of
the use of pottery in America is somewhat limited. We can learn if
we are willing to look outside our own culture.
Lee In Mashiko
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