Russel Fouts on sat 3 apr 04
>> I am also guessing that the traditional preparation of the surfaces of oribe removes oxides from the urface.>>
Could you go into that in some detail. I know a little but it would be
interesting to know more.
Russel
--
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Ivor and Olive Lewis on sun 4 apr 04
Dear Friends,
I would be suspicious about using an acid wash to remove the surface
traces of Copper from Copper bearing glazes.
Some of the acids used will also attack boron bearing substances and
release them, as I pointed out in a recent post about the
qualitative identification of boron using Sulphuric acid.
There are some modern ceramics which are deliberately treated in this
way to make microporous filters where the channels have molecular
dimensions. You would not be able to distinguish them from an opaque
porcelain. Check the records of the ACerS to verify this.
I think we should face facts. Many Copper compounds dissolve in
water, some dissolve in aqueous acid solutions. It would be hard to
find any that are insoluble in water or acid.
Were Copper or its compounds freely soluble in Magma melts it would
never be found as a native, that is a natural, raw metal. Take a
lesson from Nature and accept that we will not make it change its
behaviour. I think I am beginning to understand why.
Best regards,
Ivor Lewis. Redhill, South Australia
----- Original Message -----
Russel Fouts said:
>> I am also guessing that the traditional preparation of the surfaces
of oribe removes oxides from the urface.>>
Mike Martino on sun 4 apr 04
Hello All,
As I understand this, the process (called 'shibunuki') is the process of
cleaning the oxidized material from the surface of the ware. I've never
personally performed this process, so the following is out of a Japanese
book of mine on how to make and treat Oribe wares (I know, I know, it's the
old I'm not a doctor but I play one on TV bit, sorry).
In the pictures I've seen, Oribe green emerges from the kiln a dirty
green/brown color and this treatment is necessary to bring out it's real
color. Traditionally, the base of the stem (the horse chestnut counterpart
to that little belly button looking green thingy left on an orange after you
pluck the stem out, can't remember what those are called, in fact I don't
think I've ever known)on horse chestnuts are soaked in water to make a
mildly acid solution.
Nowadays, them new fangled fancy potters use a 3% hydrochloric acid solution
to soak the wares in for about half an hour. I've also read that if you keep
the used "dirtied' solution for a few days and soak the ware in that, you
will get a nice brown staining in the crackle of the glaze which gives the
pots good 'flavor'.
Hope this helps,
Mike
in Taku, Japan
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Lee Love
Sent: Sunday, April 04, 2004 9:20 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Foodsafe Oribe
Russel Fouts wrote:
>Could you go into that in some detail. I know a little but it would be
>interesting to know more.
>
>
Hi Russel. Maybe Rick could tell us. He mentions doing it in
Japan. I have never used it. Actually, I've never used oribe
(except in a couple tests), but have used sage nuka, which is copper but
a different glaze. I also developed a boro-lithium "Glassy Green"
that was a little higher temp than MacKenzie's, adding MacKenzie's
colorants to a Chappel glaze.
I mentioned the trip to Stillwater I shared here and Jean
reminded me that MacKenzie was treating some Glassy Green ware when we
arrived, so that is how we heard the story from him about finding out
about oribe treatment from Ken Matsuzaki.
Lee In Mashiko http://mashiko.org
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Lee Love on sun 4 apr 04
Ivor and Olive Lewis wrote:
>Dear Friends,
>I would be suspicious about using an acid wash to remove the surface
>traces of Copper from Copper bearing glazes.
>Some of the acids used will also attack boron bearing substances
>
I don't believe boron is a common material in oribe. Not in
the recipes I have seen.
Here is a good one for you Ivor. (don't try this at home.) I
was told that the "poorman's hydrochloric acid" is toilet
cleaner. I use to know the common acid in toilet cleaner, was it
acidic acid? Can't recall now. If I remember correctly, the
"natural" cleaners use citric acid.
Hey, how about a bunch of squeezed lemons? Coca Cola?
;-)
I was asking Jean today, what Japanese foods would you not
use with an enamel decorated plate made by Sensei. She said it was
difficult to think of an acidic Japanese food.
Lee In Mashiko
John Hesselberth on sun 4 apr 04
Hi Lee,
Almost all foods are acidic to a greater or lessor degree. Even soy
sauce (pH 4.4-5.4 -- for those reading this who are not familiar with
pH numbers, anything below 7.0 is considered acidic). Tofu is one of
the few foods that is slightly alkaline at pH 7.2. There is a huge
list of food pHs on the US Government's FDA site. If you are
interested, check it out at:
http://www.cfsan.fda.gov/~comm/lacf-phs.html
Regards,
John
On Sunday, April 4, 2004, at 05:34 AM, Lee Love wrote:
> She said it was
> difficult to think of an acidic Japanese food.
http://www.frogpondpottery.com
http://www.masteringglazes.com
Lee Love on sun 4 apr 04
Russel Fouts wrote:
>Could you go into that in some detail. I know a little but it would be
>interesting to know more.
>
>
Hi Russel. Maybe Rick could tell us. He mentions doing it in
Japan. I have never used it. Actually, I've never used oribe
(except in a couple tests), but have used sage nuka, which is copper but
a different glaze. I also developed a boro-lithium "Glassy Green"
that was a little higher temp than MacKenzie's, adding MacKenzie's
colorants to a Chappel glaze.
I mentioned the trip to Stillwater I shared here and Jean
reminded me that MacKenzie was treating some Glassy Green ware when we
arrived, so that is how we heard the story from him about finding out
about oribe treatment from Ken Matsuzaki.
Lee In Mashiko http://mashiko.org
Dewitt on sun 4 apr 04
At 09:47 AM 4/4/2004, you wrote:
>Almost all foods are acidic to a greater or lessor degree. Even soy
>sauce (pH 4.4-5.4 -- for those reading this who are not familiar with
>pH numbers, anything below 7.0 is considered acidic). Tofu is one of
>the few foods that is slightly alkaline at pH 7.2. There is a huge
>list of food pHs on the US Government's FDA site. If you are
>interested, check it out at:
>
>http://www.cfsan.fda.gov/~comm/lacf-phs.html
Interestingly, tea is also listed as alkaline at 7.2 though I imagine that
might vary by the type of tea.
deg
Ivor and Olive Lewis on mon 5 apr 04
Dear Lee Love,
I do not recall inferring that Oribe glaze contains Boron. I told the
group that some of the acids which might be used could deplete Boron
bearing substances. I now have more information about the solubility
of various elements when combined with the Silicate Ion (SiO3).
It is possible that some toilet cleaners contain an acid substance to
remove the lime deposits. Unless manufacturers wish to divulge the
contents of their products who would know?
Some beverages contain one of the Phosphoric acids, again you need to
be party to the recipe to find out which. Acid in Japanese foods ? I
thought Japanese culinary culture was famous for pickles, preserved in
Sake Vinegar.
Best regards,
Ivor Lewis. Redhill, South Australia
Lee Love on mon 5 apr 04
John Hesselberth wrote:
> Almost all foods are acidic to a greater or lessor degree.
Yes, I think "lessor" is the key word. If you have
experience in nutrition, you know that there are a range of acidic,
neutral and basic foods. Back in the days of the "Brown Rice Fast",
my Zen teacher's wife would warn folks that they should also drink apple
juice with the brown rice, to balance the pH. I never tried the
Brown Rice Fast, though I have the Watermelon Fast. :-) If you
look at the FDA site you mention:
http://www.cfsan.fda.gov/~comm/lacf-phs.html
you'll note that few foods are very acidic. Neutral, the pH of water
is 7pH. Most foods in the acidic range are only slightly acidic,
being more neutral than acidic. Rice and fish are in this range (6
to 7), very close to neutral. Any dry food is not likely to interact
with the glaze surface. Common sense is what is required.
Of course, there is also a huge range of functional work that is
not made specifically for use with food, especially here in Japan. One
of my specialties is work for the altar. I believe we can best
support our craft by educating people about the wide world of ceramics
and their proper use.
In the current Daruma, there is an article on
Andon, drip plates used under the traditional oil lamp. You can see a
fine Andon on the cover of the current Daruma magazine here:
http://www.darumamagazine.com/current.htm Most of these are probably
safe for use with most foods even though they were not originally made
for food. There are a couple pictured with Oribe glaze.
Lee In Mashiko http:/:/mashiko.org
Janet Kaiser on mon 5 apr 04
And the water used to make the tea? Seems to me that there must
be quite a wide range of tea readings, as there would be very few
with a completely neutral water supply.
I feel the expression, "acid test", is ever so slightly incorrect
in some ways and certain instances... Subject anything to extreme
alkalinity and it is just as likely to be affected to a similar
degree as with an acid of equal "strength"...
Sincerely
Janet Kaiser
*** IN REPLY TO THE FOLLOWING MAIL:
>Interestingly, tea is also listed as alkaline at 7.2 though I
imagine that
>might vary by the type of tea.
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terryh on mon 5 apr 04
Lee wrote,
>She said it was difficult to think of an acidic Japanese food.
lee, you aren't eating like japanese in japan!
acidic japanese food is very common, called su-no-mono or su-ae.
"su" is (rice) vinegar. nama-su with juliened radish and carrot;
with cucumber; saba-su; tako-su;...... all using san(3)-bai-zu(su),
that is 3:1 vinegar to water (or soup stock) dressing. there are
many other su-ae dishes (just like many many salada's). some
recipes call for ni(2)-hai-zu(su), 3:2 mixture (i think this is
right), for mostly sea food.
japanese also love to use pon-zu(su), japanese lemon, generally
with seared or broiled fish, some on raw fish.
pon-zu is also served on nabe-mono, casserole dish.
some fish are cured with vinegar, like ceviche. mackerel, for example.
some vegetables are also pickled with vinegar. most notably, plum
(ume-boshi). one ume-boshi (pickeld plum) placed at the center of
steamed rice creates a hole in aluminium lunch box lid.
vinegar is good for you :)
terry
terry hagiwara
terryh@pdq.net
http://www.geocities.com/terry.hagiwara
Lee Love on tue 6 apr 04
terryh wrote:
>some vegetables are also pickled with vinegar. most notably, plum
>(ume-boshi). one ume-boshi (pickeld plum) placed at the center of
>steamed rice creates a hole in aluminium lunch box lid.
>
First question Terry, would you tell people not to use traditional
Japanese pottery because of "food safety" reasons?
Umeboshi are pickled with salt, not vinegar. The juice is incorrectly
called vinegar. Macrobiotics see this as an alkaline food and is used
for stomach ailments like car sickness and the like because of this.
The Kushi institute says:
>Alkalizing Effect of Umeboshi
>We can maintain a weak alkaline pH (of about 7,35) in our blood by
regularly consuming umeboshi.
.
http://kushi.yourwebinfo.com/webinfo/prezentace.asp?site=1&page=64
Japanese food acidic?
It really is a matter of degree. Japanese vinegar is pretty mild
compared to vinegars used back home:
> RICE VINEGAR
> Usually made from fermented rice or rice wine. Originating in China
> and Japan. Chinese rice vinegars are stronger than those of Japan and
> range in colour from colourless ,through various shades of red and
> several shades of brown. Compared to other types of vinegar Chinese
> and , especially , Japanese vinegars are very mild ; almost sweet.
> Japanese rice vinegar is very mild and mellow and ranges in colour
> from colourless to pale yellow. There are two distinct types of
> *Japanese vinegar* ; one made from fermented rice and the other is
> made by adding rice vinegar to sake.
> http://www.nationalimporters.com/history/history.asp?articleid=39.
Lee in Mashiko, Japan
surf with Lee: http://hachiko.com
Craig Edwards on thu 8 apr 04
Hello All: With all the posts on copper leaching I tried the lemon test
on a published oribe glaze. I thought that it would be a good lesson for
my students. Hmmm. Before I go any further here is the recipe- I think
it came from a Claytimes Article--so I don't think that I'm giving away
someone's secret glaze.
Shaner Oribe ^10
Custer 2930
Flint 2400
Whiting 2120
EPK 1190
Black Copper Oxide 350
It was fired in an electric kiln.
Well to make a long story short --nothing happened(the lemon slice was
on there for three days). I looked at it with a magnifying glass, no
change. Next I tried muriatic acid 26%, HCL solution. Strong stuff.
Still nothing.
Although I have worked in clay testing labs, I've never done copper
leaching tests on a high level.
With what has been said about copper in glazes, I'm thinking that there
is probably some leaching going on. But how can I tell. Does someone on
the list have the procedure for determining copper leaching on a more
quantifiable level.
Regards,
Craig the bewildered,
New London MN
Lee Love on thu 8 apr 04
Craig Edwards wrote:
>
> Well to make a long story short --nothing happened(the lemon slice was
> on there for three days). I looked at it with a magnifying glass, no
> change. Next I tried muriatic acid 26%, HCL solution. Strong stuff.
I've had the same results with the lemon test on my Sage Nuka Craig..
Maybe the trick is not to use low silica copper glazes as John H. did.
I will write a long reply to Ron soon, on a diversity of methods.
I put up my recipes for Nuka, Nuka Sage, L.G. Clear and Reeve's
synthetic Mashiko Kaki at the photos pages, listed as comments. These
are in "American" materials. Many people have asked for these (sorry I
didn't answer privately):
For Nuka: http://public.fotki.com/togeika/pots_from_mashiko/sage.html
For John Reeve Synthetic Mashiko Kaki:
http://public.fotki.com/togeika/pots_from_mashiko/aut_0006.html
Lee In Mashiko
surf with Lee: http://hachiko.com
John Hesselberth on thu 8 apr 04
On Thursday, April 8, 2004, at 08:36 AM, Craig Edwards wrote:
> With what has been said about copper in glazes, I'm thinking that there
> is probably some leaching going on. But how can I tell. Does someone on
> the list have the procedure for determining copper leaching on a more
> quantifiable level.
> Regards,
> Craig the bewildered,
> New London MN
Hi Craig,
This glaze was leach tested by Tom Wirt and Betsy Price a few years
ago. It leached 52.5 mg/l which is a lot in my view. Vinegar/lemon
testing only shows up the very worst of glazes, although usually I can
see some visible color or sheen change at 50 mg/l. On a few glazes I
have seem visible difference as low as 20-30 mg/l. I have set my own
personal limit at 6--Monona would favor 1.3 (the water limit). I know I
can make very attractive glazes and still be below 6 and my personal
view is that the water standard is not relevant or directly comparable
to glaze testing.
The results for Shaner's Oribe are posted on my web site at:
http://www.frogpondpottery.com/glazestability/glaze0120.html
You can also find instructions for having a lab quantitatively test for
leaching at:
http://www.frogpondpottery.com/glazetest.html
I should add that you may have just enough different ingredients or
firing conditions that your version of Shaner's Oribe may perform
better than Tom/Betsy's. I would guess that it will still show pretty
high leaching numbers, but maybe not 52. This is not a perfectly
reproducible result.
Regards,
John
http://www.frogpondpottery.com
http://www.masteringglazes.com
Craig Edwards on thu 8 apr 04
John; Thanks for your input; I'm sorry to say that the glaze that you
refer to is not the glaze that I posted. Same name, different glaze.
Do you know what the test is that the labs do?
Thanks again for all your contributions.
Craig Edwards
New London MN
John Hesselberth wrote:
>
> Hi Craig,
>
> This glaze was leach tested by Tom Wirt and Betsy Price a few years
> ago. It leached 52.5 mg/l which is a lot in my view. Vinegar/lemon
> testing only shows up the very worst of glazes, although usually I can
> see some visible color or sheen change at 50 mg/l.
> The results for Shaner's Oribe are posted on my web site at:
>
> http://www.frogpondpottery.com/glazestability/glaze0120.html
>
Lee Love on fri 9 apr 04
Hi Craig,
Another thing occurred to me in reading folks comments on Oribe
(from John's comments that changing silica levels made red for him),
is that oribe is traditionally fired in oxidation and it WILL NOT turn
red when fired properly. Also, the long soak John and Ron recommended
may effect the copper oxide. As Hank has told us about his experience
with Shino and the soak, soaking helps the oxide crystallize on the
surface of the glaze. It might be desirable to fire oribe the
traditional way (sometimes the old farts from way back actually knew
better :-) .) and of course, paying attention to the traditional use of
the glaze helps too. Only education will protect us from our own
stupidity and presumptions. As they say, when your only tool is a
hammer, all the problems look like nails.
Also, if you go here, there is a google translation
of Edouard's explanation of copper toxicity. Knowledge and a little
common sense helps keep us from reacting in fear. It really is good to
know about copper, with all that copper plumbing bringing water into
our homes!
http://translate.google.com/translate?sourceid=navclient-menuext&hl=en&u=http%3A//www.digitalfire.com/education/toxicity/copper.htm
(if the above link is broken, manually paste it together.)
"Copper is an essential element in mammalian systems. Ilness occurs when
diet is deficient or intake is excessive. The principal route of
exposure is through ingestion, but inhalation of copper dust and fumes
occurs in industrial settings. Toxicity has resulted from treatment of
burns using topical copper compounds. Copper has been reported to be
absorbed internally from prostheses, intrauterine devices, hemodialysis
units using copper-containing equipment, and copper azide impregnation
of the skin after an explosion."
Lee In Mashiko
Surf with Lee http://hachiko.com
Ivor and Olive Lewis on fri 9 apr 04
Dear Craig Edwards,
There are two things you can do.
The first is to evaporate your test Hydrochloric acid test liquor to
dryness and do a platinum wire Flame Test. Although the flame may be
contaminated with Sodium (from the felspar you may be fortunate to see
a Green to Green blue colouration. You can always cross check by doing
a reference test with copper oxide and a drop of strong HCl.
The second is to evaporate to dryness and do a Borax Bead Test on the
residue. Look for a slight green colouration of the bead.
These are only Qualitative tests but they do give an indication.
If you wish to do Wet tests which involve H2S please contact me direct
or get a Student text which incorporates instructions for Chemical
Analysis.
Best regards,
Ivor Lewis. Redhill, South Australia
.
Carol Tripp on fri 9 apr 04
Hi Guys,
Last year, I came up with a recipe that yeilded a brilliant bright blue
turquiose. I tested it with lemons and with vinegar - no noticable change.
Then I had it tested at the lab and it leached 36.4mg/L of copper and John H
and I decided not to bother posting the recipe or the results on his site
because there really isn't a need for yet another copper- leaching glaze out
there. The recipe analysis pointed to the glaze being strong but the lab
showed otherwise. It was not low in silica and had 3% copper. You just
never know...copper is problematic.
Best regards,
Carol
Dubai, UAE
>
>Craig Edwards wrote:
>
>>
>>Well to make a long story short --nothing happened(the lemon slice was
>>on there for three days). I looked at it with a magnifying glass, no
>>change. Next I tried muriatic acid 26%, HCL solution. Strong stuff.
Then Lee Love wrote:
>I've had the same results with the lemon test on my Sage Nuka Craig..
>Maybe the trick is not to use low silica copper glazes as John H. did.
> I will write a long reply to Ron soon, on a diversity of methods.
>
_________________________________________________________________
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Craig Edwards on fri 9 apr 04
Hello Ivor: Thanks for the information. Yes, I've already started to
evaporate the HCL solution. I'll try the flame test. I guess that I'm
just a curious person.
I was hoping on finding an easy precipitation that I could do. I'm sure
its there, but being lazy I thought that I would just ask instead of
looking it up;O).
Thanks again. Your help is always appreciated.
Craig Edwards
New London MN.
Ivor and Olive Lewis wrote:
>Dear Craig Edwards,
>There are two things you can do.
>The first is to evaporate your test Hydrochloric acid test liquor to
>dryness and do a platinum wire Flame Test. Although the flame may be
>contaminated with Sodium (from the felspar you may be fortunate to see
>a Green to Green blue colouration. You can always cross check by doing
>a reference test with copper oxide and a drop of strong HCl.
>The second is to evaporate to dryness and do a Borax Bead Test on the
>residue. Look for a slight green colouration of the bead.
>These are only Qualitative tests but they do give an indication.
>If you wish to do Wet tests which involve H2S please contact me direct
>or get a Student text which incorporates instructions for Chemical
>Analysis.
>Best regards,
>Ivor Lewis. Redhill, South Australia
>
>
>
>
>
John Hesselberth on fri 9 apr 04
Hi Craig,
The test is a 24 hour leaching in 4% acetic acid (room temperature)
followed by atomic absorption spectroscopy of the leachate. It is the
same procedure the FDA specifies for lead and cadmium, with different
filters on their equipment to find whatever you ask them to look for.
If you want them, I have the FDA procedures as pdf files and can
forward them to you off list. Let me know.
John
On Thursday, April 8, 2004, at 12:41 PM, Craig Edwards wrote:
> Do you know what the test is that the labs do?
> Thanks again for all your contributions.
http://www.frogpondpottery.com
http://www.masteringglazes.com
Edouard Bastarache Inc. on fri 9 apr 04
Lee,
it is a part of my text posted on Tony Hansen's site.
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/
Ron Roy on sat 10 apr 04
First of all it was I that said - when I tried to alter an oribe to make it
more stable I lost the colour - in reduction - many potters fire oribe in
reduction by the way.
Oxides do not come to the surface during a long soak - that happens as the
glaze cools - when the excess oxide can no longer stay soluble in the
glass.
Yes -I agree - Only education will protect us from our own stupidity and
presumptions.
Many toxicologists disagree on what is harmful and what is not - best to
get many view points and draw your own conclusions. Taking the information
that only supports what you want to believe is not the best way - far from
it.
I was just going over some old posts from Michael Banks - who used to post
to this list. Knew his geology inside out from what I could percieve. His
opinion about copper in glazes - best to avoid it because of the problems
it presents.
I do think it is possible - now that we are paying more attention to what
makes glazes durable and stable - and testing them.
RR
> Another thing occurred to me in reading folks comments on Oribe
>(from John's comments that changing silica levels made red for him),
>is that oribe is traditionally fired in oxidation and it WILL NOT turn
>red when fired properly. Also, the long soak John and Ron recommended
>may effect the copper oxide. As Hank has told us about his experience
>with Shino and the soak, soaking helps the oxide crystallize on the
>surface of the glaze. It might be desirable to fire oribe the
>traditional way (sometimes the old farts from way back actually knew
>better :-) .) and of course, paying attention to the traditional use of
>the glaze helps too. Only education will protect us from our own
>stupidity and presumptions. As they say, when your only tool is a
>hammer, all the problems look like nails.
>
> Also, if you go here, there is a google translation
>of Edouard's explanation of copper toxicity. Knowledge and a little
>common sense helps keep us from reacting in fear. It really is good to
>know about copper, with all that copper plumbing bringing water into
>our homes!
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Carol Tripp on sat 10 apr 04
Hi Lee
The glaze was high in alkalines to get the copper to give blue. ( I am not
going to publically post the recipe for reasons stated previously.)
I broke my own rule of clarity when I failed to make it clear that the
point I was trying to make was that lemons and vinegar don't always force a
"show" of leaching. (And that was such a lousy sentance.) Lab testing is
the definative test.
Best regards,
Carol
Dubai, UAE
Where it is spitting with rain - wouldn't it, on the day I need some pots to
dry FAST.
Lee wrote, in part:
>Carol, what caused the copper to be "brilliant bright blue
>turquoise"? Could other things in the recipe contribute to the
>leaching? Difficult to know without seeing the recipe.
>
> My bright blue/green recipe started out as a glaze with barium in
>it. I never used it with barium.. Pete Pinnell, about 12 years or
>so ago, when not a lot of people doing it, clued me into the amount for
>strontium substitution in the glaze. I get some great colors,
>especially in wood fire and soda.
>
>
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Ivor and Olive Lewis on sat 10 apr 04
Dear Lee,
I like the comment about Copper Azide.
Not you common or garden ceramic raw material ! ! But I did read
somewhere recently about the solution being used to paint patterns on
clay.
Best regards,
Ivor Lewis. Redhill, South Australia
Earl Krueger on sat 10 apr 04
Ivor,
Since the azides has been mentioned perhaps
you might like to comment on their explosive
tendencies. I have heard that they have the
propensity to collect in sink P traps and then if
the trap dries out the force of a drop of water
can set them off.
Earl K...
Bothell, WA, USA
Ivor and Olive Lewis on sat 10 apr 04
Dear Carol,
One Milligram per litre is one part per million.
A long time ago I attended a conservation meeting concerned with the
use of coal mine workings as disposal dumps for toxic wastes. The
principle proponents of the proposal were going on about the minuscule
amounts that might leach into the water table or seep along strata to
discharge into the sea.
I asked him to please illustrate One Part Per Million. I was told it
was so insignificant that you would never notice so I pointed to the
space under the table where he was sitting and told him that there
were at least a million cubic centimetres in that space. "So What was
the reply! "Well" I said, "You would have to be blind not to notice a
sugar cube if there were one there at your feet" . All a matter of
scale. They were proposing several thousands of tons of cyanide,
dioxin etc.
We might never notice a few ppm in a cup full of vinegar. A
precipitation test would hardly show cloudiness. The flame test just
might give a glimmer. Your result shows that we must be careful.
Thanks for sharing your information.
Best regards,
----- Original Message -----
From: "Carol Tripp"
To:
Sent: Friday, 9 April 2004 4:36
Subject: Re: Foodsafe Oribe
> Hi Guys,
> Last year, I came up with a recipe that yeilded a brilliant bright
blue
> turquiose. I tested it with lemons and with vinegar - no noticable
change.
> Then I had it tested at the lab and it leached 36.4mg/L of copper
and John H
> and I decided not to bother posting the recipe or the results on his
site
> because there really isn't a need for yet another copper- leaching
glaze out
> there. The recipe analysis pointed to the glaze being strong but
the lab
> showed otherwise. It was not low in silica and had 3% copper. You
just
> never know...copper is problematic.
> Best regards,
> Carol
> Dubai, UAE
>
> >
> >Craig Edwards wrote:
> >
> >>
> >>Well to make a long story short --nothing happened(the lemon slice
was
> >>on there for three days). I looked at it with a magnifying glass,
no
> >>change. Next I tried muriatic acid 26%, HCL solution. Strong
stuff.
>
>
> Then Lee Love wrote:
> >I've had the same results with the lemon test on my Sage Nuka
Craig..
> >Maybe the trick is not to use low silica copper glazes as John H.
did.
> > I will write a long reply to Ron soon, on a diversity of
methods.
> >
>
> _________________________________________________________________
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Lee Love on sat 10 apr 04
Carol Tripp wrote:
> Hi Guys,
> Last year, I came up with a recipe that yeilded a brilliant bright blue
> turquiose.
Carol, what caused the copper to be "brilliant bright blue
turquoise"? Could other things in the recipe contribute to the
leaching? Difficult to know without seeing the recipe.
My bright blue/green recipe started out as a glaze with barium in
it. I never used it with barium.. Pete Pinnell, about 12 years or
so ago, when not a lot of people doing it, clued me into the amount for
strontium substitution in the glaze. I get some great colors,
especially in wood fire and soda.
Lee In Mashiko
surf with Lee: http://hachiko.com
sdr on sun 11 apr 04
Lee said:
> If one is phobic about copper, a simple solution is to use your copper
> glazes only on the outside of ware, where it does not come in contact
> with food,>>>>>>>
All of this re-hash of copper/copper leaching/copper safety
leads me to note that on returning from a workshop at Western
Wyoming College last week, I found on my doorstep a box.
In the box was a pitcher, probably holds 3 quarts or so. It
is deceptively simple, and simply beautiful. It was made by long-time
functional potter Maishe Dickman. The pitcher has a beautiful
rich green glaze on it - translucent, semi-gloss (a bit shinier than
a semi-matt, but not much). Might be an Oribe, might be
Shaner, might be anything. Dunno. Obviously a lot of copper in it.
HOWEVER - the inside of the
pitcher has a white liner glaze, the green reaches from foot to
neck on the outside, the neck has been dipped in (apparently) a tenmoku.
Where the tenmoku overlaps the green there is a lovely wide
gold line, breaking up into a mixtures of blues and greens
and blending into the green glaze. It is altogether beautiful,
quite potterly, and thoughtfully done. It does seem to me that a bit of
sensible attention to detail is all that's required, and one can
use all the green glazes one might wish. If I decide to fill this
up with sangria or lemonade or tomato juice, I can do so
without concern.
regards
Dannon Rhudy
Ivor and Olive Lewis on mon 12 apr 04
Dear Lee Love,
I have no doubt about the correctness of information posted in the
past by Michael Banks.
You Quote <<...Melts with a high alumina/alkali,alkali earth ratios
have been found to have the highest proportions of octahedral sites
(ref: Feiss P.G. 1978, Economic Geology. V23, pp397-404, "Magmatic
Sources of copper in Porphyry Copper Deposits".>>>
I think "natural copper contents" is a reference to "Native Copper" an
almost pure metal such as that found in the major Canadian
emplacements
But note that the use of co-ordination numbers for the location of
ions is applicable to substances which have well defined crystalline
structures and lattice frameworks which proved for the location of the
dominant element, which in the case of the materials we use, is
Oxygen. We deal with an amorphous material which is only structured at
the Angstrom level but disordered at the micrometre level.
What I have not found in the geological list are minerals composed
only of Copper Silicon and Oxygen. All natural mineral containing
copper and silicate are associated with hydrogen. The neighbour of
Copper in the Periodic Table, Zinc, form a clearly identifiable
silicate crystal mineral or compound called Willemite. No one ever
speaks of the leaching of Zinc. So why should there be this
difference?
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.
Best regards,
Ivor Lewis. Redhill, South Australia
Hendrix, Taylor J. on mon 12 apr 04
Lee,
Are you sure you are using the archives to keep anyone honest? For
starters, Michael Banks was no fan of copper (rightly or wrongly) in a
glaze:=20
http://lsv.ceramics.org/scripts/wa.exe?A2=3Dind9908&L=3DCLAYART&P=3DR2358=
8&m=3D5
7752
Secondly, he said "probably even MORE prone" [emphasis mine], his
initial point being that copper is prone to leaching in silicate melts
of certain structures. He of course is extrapolating geological
knowledge of "natural copper contents" to stoneware glazes. He of
course calls for potters to make available their leaching research,
something that John Hesselberth was doing at the time and what prompted
Banks' posting in the first place.
I'm not certain why Banks excluded boron and phosphorous glazes from his
statement, but my guess is that boron and phosphorous being glass
formers as well as silica, they don't fall under the particular silica
structure to which he was referring. While, your statement might be
correct on its own, Banks doesn't seem to have made that claim in your
quoted section either way. Here is the link for those of you interested
in reading it directly from the archives:=20
http://lsv.ceramics.org/scripts/wa.exe?A2=3Dind9909&L=3DCLAYART&P=3DR7135=
0&m=3D5
7752
Just another voice for amelioration.
Taylor, in Waco
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Lee Love
Sent: Sunday, April 11, 2004 10:40 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Foodsafe Oribe
...
I looked up the post and I think you"spun" what Michael said to support
your argument. If you read the quote below, you will note that
Michael says that copper is more prone to leaching in alkaline, high
silica glazes. Also, the leaching is effected by boron and phosphorous
(the archives keep us honest):
...
Lee Love on mon 12 apr 04
Ron Roy wrote:
>I was just going over some old posts from Michael Banks - who used to post
>to this list. Knew his geology inside out from what I could percieve. His
>opinion about copper in glazes - best to avoid it because of the problems
>it presents.
>
>
This really makes no rational sense and limits aesthetic expression.
If one is phobic about copper, a simple solution is to use your copper
glazes only on the outside of ware, where it does not come in contact
with food, or on forms that are not used for serving food. This is
primarily how the traditional copper glazes are used here in Mashiko (on
the outside of jars and sake bottles.)
Lee In Mashiko
surf with Lee: http://hachiko.com
Lee Love on mon 12 apr 04
Ron Roy wrote:
>I was just going over some old posts from Michael Banks - who used to post
>to this list. Knew his geology inside out from what I could percieve. His
>opinion about copper in glazes - best to avoid it because of the problems
>it presents.
>
I looked up the post and I think you"spun" what Michael said to support
your argument. If you read the quote below, you will note that
Michael says that copper is more prone to leaching in alkaline, high
silica glazes. Also, the leaching is effected by boron and phosphorous
(the archives keep us honest):
Michael Banks on tue 21 sep 99 (mjbanks@clear.net.nz
) wrote:
> It is clear from the geological literature that copper is more
> soluble in
> silicate melts (and glasses) ...
> ...Melts with a high alumina/alkali,alkali earth ratios have been
> found to have
> the highest proportions of octahedral sites and natural copper
> contents
> (ref: Feiss P.G. 1978, Economic Geology. V23, pp397-404, "Magmatic
> Sources
> of copper in Porphyry Copper Deposits".
>
> I believe these data are directly applicable to stoneware glazes
> (excluding
> boron and phosphorous glazes). The problem for potters is that
> copper in
> high alumina glazes is rendered a dull green colour, versus the
> bright
> blues, turquoise and reds possible in high alkali, low alumina
> glazes. But
> unfortunately alkaline glazes are probably even more prone to
> leaching
> (apart from limited copper solubility) because they are inherently
> less
> durable (softer) and craze prone (high surface area available for
> leaching).
>
Lee In Mashiko
surf with Lee: http://hachiko.com
Lee Love on mon 12 apr 04
sdr wrote:
> Obviously a lot of copper in it.
> HOWEVER - the inside of the
>pitcher has a white liner glaze, the green reaches from foot to
>neck on the outside, the neck has been dipped in (apparently) a tenmoku.
>Where the tenmoku overlaps the green there is a lovely wide
>gold line, breaking up into a mixtures of blues and greens
>and blending into the green glaze. It is altogether beautiful,
>quite potterly, and thoughtfully done. It does seem to me that a bit of
>sensible attention to detail is all that's required, and one can
>use all the green glazes one might wish. If I decide to fill this
>up with sangria or lemonade or tomato juice, I can do so
>without concern.
>
>
Thanks for the example Dannon. This is how oribe is usually
used in Japan. It is rarely used on the inside of a closed pot (I have
seen a few totally green little cups, but this is rare.). Typically, on
things like bottles and the sake pourers that look like teapots,
matchawan (things that hold liquid), the green is only dipped on the top
on the outside (on the matchawan, you sometimes see a little on the
inside lip. The base glaze is tan or gray.
--
Lee In Mashiko
Hendrix, Taylor J. on mon 12 apr 04
Lee,
The quoted excerpt [I have not included it] DOES make rational sense and
the rationale is not hard to follow if one is willing to do so. Your
simple solution is both simple and brilliant and I think has yet to be
disputed.
Since a solid rationale does exist for such observations of the
functioning of certain Oribe glazes I am finding it rather difficult to
pinpoint any phobic reaction to the use of copper. Let me know what you
mean.
Taylor, in Waco
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Lee Love
Sent: Sunday, April 11, 2004 10:29 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Foodsafe Oribe
...
This really makes no rational sense and limits aesthetic expression.
If one is phobic about copper, a simple solution is to use your copper
glazes only on the outside of ware, ...
Ron Roy on tue 13 apr 04
Yes - use em on the outside as much as you want - that is understood of
course. I have never said anything else but that.
And if you want to use em on the inside make a glaze that will hold em -
simple enough - a rational approach!
I had a look at the Nuka green glaze on your plate - beautiful glaze - but
it's going to leach copper into food on that plate - just a mater of time
and temperature.
RR
>>I was just going over some old posts from Michael Banks - who used to post
>>to this list. Knew his geology inside out from what I could percieve. His
>>opinion about copper in glazes - best to avoid it because of the problems
>>it presents.
>>
>>
>
>This really makes no rational sense and limits aesthetic expression.
>If one is phobic about copper, a simple solution is to use your copper
>glazes only on the outside of ware, where it does not come in contact
>with food, or on forms that are not used for serving food. This is
>primarily how the traditional copper glazes are used here in Mashiko (on
>the outside of jars and sake bottles.)
>
>Lee In Mashiko
>surf with Lee: http://hachiko.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on tue 13 apr 04
Wrong post Lee - I am not in the habit of lying by the way.
Post #1(I am including it because I know Ivor will find it interesting - is
the position of Cu at the beginning of the list significant?)
Date: Tue, 3 Aug 1999 14:17:00 EDT
Reply-To: Ceramic Arts Discussion List
Sender: Ceramic Arts Discussion List
From: Michael Banks
............. The chalcophile elements are only weakly attached in silicate
materials and include quite a few nasties. Of relevance to ceramists, they
include Cu,Cd,Sb,Ag,Bi,Pb,Zn, which suggests that these elements will be
only weakly attached to the Si and O atoms in glazes. The anomaly in this
group is Zn, which does not always behave like a typical chalcophile
although it partitions strongly into sulphides in meteorites and smelter
concentrates. Zinc seems to be dual in nature, being also able to form
stable silicates. This anomaly is known to occur because of zinc's high
electrode potential, which is more typical of the lithophile group. The
prediced behaviour of this group in glazes (excepting zinc) is born out by
experience, as this group are easily induced to exsolve from the glass by
subtle changes in composition, atmosphere, etc. I think it would be wise to
exclude chalcophile group elements (excepting zinc) from glazes to be used
in contact with food and drink.
Post #2
Date: Sat, 7 Aug 1999 14:56:31 EDT
Reply-To: Ceramic Arts Discussion List
Sender: Ceramic Arts Discussion List
From: Michael Banks
Subject: Let me rephrase "oxides"
Dunno Ray, but there has been a lot of informed comment in the past on this
forum about copper. If it leaches, it can't be good for you. Personally I
don't like using any copper glaze on foodware, tested to be low-leach or
not.
Purely anecdotally, I've heard that the higher than ideal levels of copper
in our diet, is implicated in causing the declining sperm counts in western
men (sorry, can't remember where I read it). So if you want a chemical
vasectomy, go for it! But remember, all that cytotoxic metal is also
carousing around inside your other organs too.
Michael Banks,
>I looked up the post and I think you"spun" what Michael said to support
>your argument. If you read the quote below, you will note that
>Michael says that copper is more prone to leaching in alkaline, high
>silica glazes. Also, the leaching is effected by boron and phosphorous
>(the archives keep us honest):
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Lee Love on wed 14 apr 04
I saw in the archives my original post from '97 related to Warren
MacKenzie and his Glassy Green. He was treating a pot that was black
with muriatic acid. After the bath and the wash, it came out bright
green. I own one of these bowls and have used it for many years,
without fear. It would be interesting to test this glaze for leaching
after the muriatic treatment.
Ron Roy wrote:
>Wrong post Lee
>
Looking at all the posts puts Michael's comments in the proper
light and takes the "spin" off your original comments on them. Spin is
not lying, but it is not providing all the facts.
The one I shared was based on what Michael knew as
scientific fact. He explained in the posts you shared that his
decision not to use copper in glazes was based on anecdotal evidence
and his "feelings" about it.
Michael wrote:
>Purely anecdotally, I've heard that the higher than ideal levels of copper
>in our diet,
>
Lee In Mashiko
Lee Love on wed 14 apr 04
Lee Love wrote:
> I saw in the archives my original post from '97 related to Warren
> MacKenzie and his Glassy Green. He was treating a pot that was black
> with muriatic acid. After the bath and the wash, it came out bright
> green. I own one of these bowls and have used it for many years,
> without fear. It would be interesting to test this glaze for leaching
> after the muriatic treatment.
Muriatic and Hydrochloric acids are the same (Muriatic is a
"traditional" name):
> . MURIATIC ACID
>
> *************************************************************************************************************************
> *SECTION I - IDENTIFICATION
> CHEMICAL NAME & SYNONYMS:* Hydrochloric Acid
> *FORMULA:* HCl
> *TRADE NAME:* Muriatic Acid
> *DESCRIPTION:* Colorless to pale yellow liquid with pungent,
> suffocating odor.
> *CAS NO.* 7647-01-0
> *HMIS HAZARD RATINGS: *Health Hazard: 3 Fire Hazard: 0 Reactivity: 0
> *************************************************************************************************************************
> *SECTION II - PHYSICAL DATA
> Boiling Point:* 110C *Boiling Point:* 110C/230F
> *Vapor Pressure:* 50 – 60 m/hg *Specific Gravity (H_2 O=1):* 1.160 –
> 1.1884
> *% Volatile by Volume:* N/A *Vapor Density:* N/A
> *Solubility in water:* Complete *Evaporation Rate:* N/A
> *************************************************************************************************************************
> *SECTION III - HAZARDOUS INGREDIENTS
> *MATERIAL CAS NO. CONTENT HAZARD DATA
> Hydrochloric Acid 7647-01-025.00 31.4 - 37% Corrosive
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