Tony Hansen on sat 11 jan 97
> Can anyone out there give some advice on the following glaze recipe:
> Neph. Sey - 56.0 Barium Carb. - 41.9
> Kentucky Ball Clay - 1.4 Lithium Carb. - 0.7
> Copper Carbonate - 3.0
> Currently I am experiencing bubbling and blisters...This glaze always used to
Wow. That's the highest barium I've ever seen in a glaze. Watch out about functi
There is almost no clay in this glaze. That accounts for the settling.
As far as blisters go, try checking the web page at
http://digitalfire.com/magic/archive/blister.htm
=================================================================
Tony Hansen, IMC - Publishers of INSIGHT/FORESIGHT/Magic of Fire
Get INSIGHT 5 beta at http://digitalfire.com/insight5.htm
ZALT@aol.com on tue 14 jan 97
I would be interested to know what colours work best with this glaze. I
feel that the glaze is probably a touch of overfired. Try a test a cone or
two lower than you are doing now.
Terrance F Lazaroff
St Hubert, Quebec, Canada!!!!
Lili Krakowski on fri 23 nov 07
I am writing with this caveat: Barium should be kept out of the pottery
studio, and the first thing Tonya should do is replace barium with
strontium. I am addressing this for the general "About Blistering"
information, and in no way as an endorsement of this glaze.
Tonya writes that a glaze that for 3 years had worked well at c.9/10
reduction in a gas kiln
has now started blistering. She tried two new batches of glaze, things did
not improve. Blisters, blisters blisters.
She then ate a lot of icecream--wise move, ice cream is one of the potter's
best tools for glaze problem solutions--
and decided to apply a c.6 glaze atop of the blistered pots, refire at c.6
electrically and there you are! The
icecream did its thing! Pots were fine.
Here is her recipe and the GlazeMaster (TM) calculations
Bar. Carb. 22.83
whit 9.78
Custer 56.52
om4 10.87
zinc ox 5.98
copper carb 4.24
rutile 4.24
bento 2.0
Na2O .076
K2O .162
MgO .008
CaO .261
BaO .302
ZnO .191
AL2O3 .338
SiO2 2.015
Checking GM again the barium exceeds the "limits" and the Al2O3 is
high....But we know the glaze worked--so what happened?
Fraser in "Ceramic Faults and Their Remedies"--a wonderfully succinct
book--tell us that "severed overfiring" makes the glaze boil, leaving
blisters. This is not our case here. Very rapid firing as the glaze
followed by rapid cooling also can cause blistering. Fine. This is info to
file away, but does not apply here.
What are his cures? Replacement of some ingredients by others...does not
really seem to apply here--except for the barium problem-- as the glaze has
worked.
Lowering alumina may help....
Now that we have done that: this glaze worked. Then it stopped. Tonya
tells us she had the kiln checked out...so that is not it.
Where do we look?
1. Changes in clay body. Always test each batch of clay body as it comes
into the studio. Always keep a batch (or lots of test tiles) of the clay
bodies. If a glaze stops working check it out on the "old" body on which it
DID work. Yes, yes, you ordered the same brand you have ordered for years
BUT: manufacturers also experiences changes in the materials they get. They
mix the same "body" but it is NOT the same. The Archives will give you all
that info.
2. Changes in glaze materials. Not that likely here, but can apply as
several glaze materials while sold under same name also are subject to
variations.
In this case, however I think that something someplace has changed, and
while the colorants --copper carb and rutile--one of which being a flux and
the other slightly refractory--are not, I think, to blame--I still would
look for a change in materials
As the c.6 application helped I would do two series of tests:
1. A straight line blend of the original glaze reducing alumina, as per
limit formula.
2. A blend of the c.6 and the c.10 glaze, which would reduce the melting
point to where at a certain point you get what you want.
I also--but I know nothing about reduction --would try slowing the firing
near maturity, and slowing the cooling after the kiln is turned off...i.e.
keeping at close to max heat a little while.
And again: always have one or two other "bodies" in the studio so as to be
able to check relatively easily if the body is at fault.
And a question for the fuel burning gurus: I seem to remember reading that
as fuelburners age they lose their "tightness"--could Tonya's problem be
that with age her kiln is less "tight" and that it is cooling faster,
preventing proper healing?
Lili Krakowski
Be of good courage
Vince Pitelka on fri 23 nov 07
Lili Krakowski wrote:
>I am writing with this caveat: Barium should be kept out of the pottery
> studio, and the first thing Tonya should do is replace barium with
> strontium. I am addressing this for the general "About Blistering"
> information, and in no way as an endorsement of this glaze.
With all due respect for Lili and her very strong social and humanitarian
conscience, there is no reason at all to eliminate barium or maganese from
the ceramic studio. They both can be used perfectly safely. Neither should
be used in a glaze to be used on food-contact surfaces if that glaze is matt
or imbalanced. This is simply a matter of education. Potters need to learn
how to formulate and test stable glazes, so that barium or manganese (or
chrome or copper) are locked in a stable glass on the surface of the pot.
That is just a matter of personal responsibility for any serious potter.
I do not want to see the glaze-formulation options for the potter diminished
in any way if the materials in question can be used safely, and barium and
manganese can be used perfectly safely. Strontium simply is not an
effective substitute for barium. Please do not feed me that standard line
about barium carbonate being used as rat poison. There are so many things
in ceramics that are potentially dangerous, and too much water will kill
you. This is just a matter of safe and sensible use, and any intelligent
person is capable of that. Let's give our fellow potters a little credit
for a modicum of common sense and responsibility.
Go ahead and use that barium and manganese, but do it safely and
responsibly.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Hank Murrow on fri 23 nov 07
On Nov 23, 2007, at 8:44 AM, Lili Krakowski wrote:
> I am writing with this caveat: Barium should be kept out of the
> pottery
> studio, and the first thing Tonya should do is replace barium with
> strontium.
Dear Lili;
Perhaps sage advice for Tonya, yet hardly applying to everyone.
I use glazes containing Barium in my work for the table, and all have
been thoroughly tested in Canada for Ba and Cu release. I do not use
any glaze containing Ba that has not been tested. please don't send
the barium Police west to Eugene!
Cheers, Hank
www.murrow.biz/hank
tonya Johnson on sun 25 nov 07
Dear Lili,
Thank you so much for taking the time to reply. I'm going to print out all
the emails and read through them. I will sub the barium. I think it's 7.5
strontium for 10.0 barium? I do want to add that I suspect my draw in the kiln is
not as good as it once was. It's a MFT (with a sprung arch--lol) that has a
pipe for the chimney. I may need a new pipe? I do seem to have a lot of gas
in the kiln. Anyway, thanks again. Tonya
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Ron Roy on sun 25 nov 07
Hi Hank,
I am interested in barium glazes that release little or no barium - any
chance you could share some information for a just cause?
How much release do you consider safe?
RR
>On Nov 23, 2007, at 8:44 AM, Lili Krakowski wrote:
>
>> I am writing with this caveat: Barium should be kept out of the
>> pottery
>> studio, and the first thing Tonya should do is replace barium with
>> strontium.
>
>Dear Lili;
>
>Perhaps sage advice for Tonya, yet hardly applying to everyone.
>
>I use glazes containing Barium in my work for the table, and all have
>been thoroughly tested in Canada for Ba and Cu release. I do not use
>any glaze containing Ba that has not been tested. please don't send
>the barium Police west to Eugene!
>
>Cheers, Hank
>
>www.murrow.biz/hank
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ron Roy on sun 25 nov 07
Hi Vince,
Do you know of any potters who have formulated a glaze with barium that
will not release it in contact with acidic food.
I think you are being very optimistic about who knows how to do what.
I have seen what is going on out there and I'm telling you - some of it is
criminal.
The glaze we are talking about here is unstable - and eveyone who see's it
needs to understand that - so we need to talk about it
RR
>With all due respect for Lili and her very strong social and humanitarian
>conscience, there is no reason at all to eliminate barium or maganese from
>the ceramic studio. They both can be used perfectly safely. Neither should
>be used in a glaze to be used on food-contact surfaces if that glaze is matt
>or imbalanced. This is simply a matter of education. Potters need to learn
>how to formulate and test stable glazes, so that barium or manganese (or
>chrome or copper) are locked in a stable glass on the surface of the pot.
>That is just a matter of personal responsibility for any serious potter.
>
>I do not want to see the glaze-formulation options for the potter diminished
>in any way if the materials in question can be used safely, and barium and
>manganese can be used perfectly safely. Strontium simply is not an
>effective substitute for barium. Please do not feed me that standard line
>about barium carbonate being used as rat poison. There are so many things
>in ceramics that are potentially dangerous, and too much water will kill
>you. This is just a matter of safe and sensible use, and any intelligent
>person is capable of that. Let's give our fellow potters a little credit
>for a modicum of common sense and responsibility.
>
>Go ahead and use that barium and manganese, but do it safely and
>responsibly.
>- Vince
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Vince Pitelka on sun 25 nov 07
Ron Roy wrote:
> The glaze we are talking about here is unstable - and eveyone who see's it
> needs to understand that - so we need to talk about it
Ron -
I certainly was not trying to limit the conversation in any way. You and
others provide such a valuable service when you help potters evaluate their
glazes, or warn them when a glaze is undersupplied with essential
ingredients. In this case, I was simply responding to a comment suggesting
that barium be purged from the ceramics studio, and I am not willing to do
that. As a general rule at the Craft Center we never use barium glazes on
food-contact surfaces. But oh, those barium mats. There is nothing else
like them, and strontium doesn't do it. Those clearly are not food contact
glazes, but on vases or on the outside of food vessels they can be very
beautiful with no risk. That's the most important message.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
June Perry on sun 25 nov 07
Ron,
A few years ago when we had this barium discussion I did a google search on
Barium Toxicology and found some government info. Seems they don't have any
great warnings about it based on what I read. I read a lot of info on rat
testings but not much on human effects.
Barium does not accumulate in the body, so to do harm, one would have to
ingest quite a bit of it at a time, which is basically what I read in those
reports.
Barium naturally occurs in many water supplies which I also found
interesting.
I don't advocate high barium matt glazes, but I certainly think one can use
barium in the studio in small amounts in a well balanced glaze.
I'd be much more worried about Chrome, vanadium pentoxide and nickel - all
cancer causing materials than I do about barium. Managanese is another one I
would be more concerned about.
As others have said, there are a lot of materials that we use in our studios
that are very toxic; but we have to learn to handle them and use them wisely
for our own protection and for the protection of our customers.
Regards,
June
_http://www.shambhalapottery.com_ (http://www.shambhalapottery.com/)
_http://shambhalapottery.blogspot.com_
(http://shambhalapottery.blogspot.com/)
_http://groups.yahoo.com/group/sodasaltfiring_
(http://groups.yahoo.com/group/sodasaltfiring)
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Hank Murrow on sun 25 nov 07
On Nov 25, 2007, at 12:45 PM, Ron Roy wrote:
> Hi Hank,
>
> I am interested in barium glazes that release little or no barium -
> any
> chance you could share some information for a just cause?
>
> How much release do you consider safe?
50ppm. What info would you like to have/
Cheers, Hank
www.murrow.biz/hank
Edouard Bastarache Inc. on wed 28 nov 07
Manganese and barium are not regulated
for use on utilitarian wares in most modern
countries, including Canada and the USA.
I do not think we should take the place of
expert-toxicologists and legislators.
Most clayarters, if not all of them, do not
know enough to play their role.
Gis la revido,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
http://www.ceramique.com/librairie/
http://www.flickr.com/photos/30058682@N00/
http://myblogsmesblogs.blogspot.com/
----- Original Message -----
From: "Ron Roy"
To:
Sent: Wednesday, November 28, 2007 7:06 PM
Subject: Re: blistering glaze
> Hi Vince - no - that is not all you said.
>
> I am including what else you said here
>
> "We cannot do anything about people who are
> blatantly careless and ignore
> our cautions, but no one is going to be poisoned
> by occasional contact with
> a pot irresponsibly glazed with an unstable
> barium or manganese glaze."
>
> We can do something - and we are. And your
> comparison of barium toxicity to
> water toxicity does not help.
>
> I would like to know what you think is a
> reasonable level of barium release
> for a coffe mug - or better still - a cassarol?
>
> RR
>
>
>
>>Ron -
>>I certainly was not trying to limit the
>>conversation in any way. You and
>>others provide such a valuable service when you
>>help potters evaluate their
>>glazes, or warn them when a glaze is
>>undersupplied with essential
>>ingredients. In this case, I was simply
>>responding to a comment suggesting
>>that barium be purged from the ceramics studio,
>>and I am not willing to do
>>that. As a general rule at the Craft Center we
>>never use barium glazes on
>>food-contact surfaces. But oh, those barium
>>mats. There is nothing else
>>like them, and strontium doesn't do it. Those
>>clearly are not food contact
>>glazes, but on vases or on the outside of food
>>vessels they can be very
>>beautiful with no risk. That's the most
>>important message.
>>- Vince
>>
>>Vince Pitelka
>>Appalachian Center for Craft, Tennessee
>>Technological University
>>Smithville TN 37166, 615/597-6801 x111
>>vpitelka@dtccom.net, wpitelka@tntech.edu
>>http://iweb.tntech.edu/wpitelka/
>>http://www.tntech.edu/craftcenter/
>>
>>______________________________________________________________________________
>>Clayart members may send postings to:
>>clayart@lsv.ceramics.org
>>
>>You may look at the archives for the list, post
>>messages, or change your
>>subscription settings here:
>>http://www.acers.org/cic/clayart/
>>
>>Moderator of the list is Mel Jacobson who may be
>>reached at melpots2@visi.com
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
>
> ______________________________________________________________________________
> Clayart members may send postings to:
> clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post
> messages, or change your
> subscription settings here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be
> reached at melpots2@visi.com
>
>
>
> --
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> Checked by AVG Free Edition.
> Version: 7.5.503 / Virus Database:
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>
vpitelka on wed 28 nov 07
Ron Roy wrote:
"Hi Vince - no - that is not all you said.
I am including what else you said here"
Vince wrote: "We cannot do anything about people who are blatantly careless
and ignore
our cautions, but no one is going to be poisoned by occasional contact with
a pot irresponsibly glazed with an unstable barium or manganese glaze."
Ron wrote:
"We can do something - and we are. And your comparison of barium toxicity to
water toxicity does not help. I would like to know what you think is a
reasonable level of barium release
for a coffe mug - or better still - a cassarole?"
Dear Ron -
I don't really understand the tone of your message. It's a bit
confrontational, and I don't think I said anything to warrant that. This is
your area of expertise, and I defer to you here. As I clearly said, at the
Craft Center we do not use barium glazes on food-contact surfaces. I advise
potters to do the same thing unless they have their glazes tested. No
barium glaze should ever be used on a food-contact surface unless it has
been tested for barium release.
I am not sure why you picked my paragraph above to quote. Of course we can
do something, and we are, you especially, all the time, on Clayart and
elsewhere, and the ceramics world is safer because of your actions. But we
CAN'T do anything about the idiots who are blatantly careless and ignore our
cautions. The best we can do is talk to all the people who will listen, and
educate them about safe glaze practice. There are always going to be some
people who just design and mix glazes by the seat of their pants as so many
people did back in the 50s, 60s, and 70s. If they use barium, chances are
that some of those glazes are going to release barium. How much barium and
how dangerous is it? I don't know. You tell me how dangerous it really is.
Maybe Edouard can chime in on this and tell us what the implications are of
barium release into coffee, tea, lemonade, or whatever. I'd like to have
some more-specific information on this. If an oribe releases copper, or if
a beautiful barium mat releases barium, what is it going to do to us? Is it
cumulative? Can the amount released at one time into one glass of coffee or
orange juice reach critical levels of toxicity?
Thanks -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
John Britt on wed 28 nov 07
Ron,
Small amounts of barium carbonate can aid in blue celadons, can influence
copper reds, purples and blues, matte glazes will often use moderate
amounts to modulate color, etc.
John Britt
www.johnbrittpottery.com
Ron Roy on wed 28 nov 07
Hi June,
Austria only allows under 1 mg/l barium release for cook ware, packaging
and storage containers.
I agree - small amounts in a durable glaze is no problem - but why would
you use Barium then? It's the high Barium copper turquoise matts that
potters use so much - and I don't know how durable they are.
Body weight is a crucial factor when you talk about poisons
Does anyone have any information about how much Barium it takes to affect a
small fetus? Body weight is a crucial factor when you talk about poisons.
There will never be any testing on humans - we rely on animal testing to
indicate when to be careful.
RR
>Ron,
>
>A few years ago when we had this barium discussion I did a google search on
>Barium Toxicology and found some government info. Seems they don't have any
>great warnings about it based on what I read. I read a lot of info on rat
>testings but not much on human effects.
>Barium does not accumulate in the body, so to do harm, one would have to
>ingest quite a bit of it at a time, which is basically what I read in those
>reports.
>Barium naturally occurs in many water supplies which I also found
>interesting.
>I don't advocate high barium matt glazes, but I certainly think one can use
>barium in the studio in small amounts in a well balanced glaze.
>I'd be much more worried about Chrome, vanadium pentoxide and nickel - all
>cancer causing materials than I do about barium. Managanese is another one I
>would be more concerned about.
>As others have said, there are a lot of materials that we use in our studios
>that are very toxic; but we have to learn to handle them and use them wisely
>for our own protection and for the protection of our customers.
>
>Regards,
>June
>_http://www.shambhalapottery.com_ (http://www.shambhalapottery.com/)
>_http://shambhalapottery.blogspot.com_
>(http://shambhalapottery.blogspot.com/)
>_http://groups.yahoo.com/group/sodasaltfiring_
>(http://groups.yahoo.com/group/sodasaltfiring)
>
>
>
>
>
>**************************************Check out AOL's list of 2007's hottest
>products.
>(http://money.aol.com/special/hot-products-2007?NCID=aoltop00030000000001)
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, or change your
>subscription settings here: http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ron Roy on wed 28 nov 07
Hi Vince - no - that is not all you said.
I am including what else you said here
"We cannot do anything about people who are blatantly careless and ignore
our cautions, but no one is going to be poisoned by occasional contact with
a pot irresponsibly glazed with an unstable barium or manganese glaze."
We can do something - and we are. And your comparison of barium toxicity to
water toxicity does not help.
I would like to know what you think is a reasonable level of barium release
for a coffe mug - or better still - a cassarol?
RR
>Ron -
>I certainly was not trying to limit the conversation in any way. You and
>others provide such a valuable service when you help potters evaluate their
>glazes, or warn them when a glaze is undersupplied with essential
>ingredients. In this case, I was simply responding to a comment suggesting
>that barium be purged from the ceramics studio, and I am not willing to do
>that. As a general rule at the Craft Center we never use barium glazes on
>food-contact surfaces. But oh, those barium mats. There is nothing else
>like them, and strontium doesn't do it. Those clearly are not food contact
>glazes, but on vases or on the outside of food vessels they can be very
>beautiful with no risk. That's the most important message.
>- Vince
>
>Vince Pitelka
>Appalachian Center for Craft, Tennessee Technological University
>Smithville TN 37166, 615/597-6801 x111
>vpitelka@dtccom.net, wpitelka@tntech.edu
>http://iweb.tntech.edu/wpitelka/
>http://www.tntech.edu/craftcenter/
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, or change your
>subscription settings here: http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
June Perry on wed 28 nov 07
Hi Roy,
If you do a thorough reading on the toxicology, you would find that the big
thing with barium is that unlike other oxides, it is not stored in the body.
The body rids itself of those small amounts that occur naturally in many
water supplies.
The risk of it, according the toxicology reports that I've read is large
doses at one time and I don't think anyone in a studio is breathing in or
drinking from a vessel that would release the amount that would be toxic. So a
small amount of it in a well balanced glaze will be safe; and if you use those
reports as a criteria, I would guess that even a glaze with a bit more barium,
wouldn't release enough of it at one time to harm anyone.
Lord, when I think of the Woo yellow and other glazes that were used in the
70's on mugs, pitchers etc, and we're all still here. When I had some tests
done for heavy metals I have copper, lead and manganese, but no barium in my
system, even though I used a set of Woo yellow mugs for years.
Everyday things we eat like nutmeg can kill us too if we eat a teaspoon of
it and water will kill a person if they drink too much at one time; but we
don't ban nutmeg or water. We learn to live within the limitations of these
things.
I think we have to use care and use all the information we have available;
but I also think there are many too scare tactics where they aren't really
called for based on the toxicology.
As I've said before, I worry much more about chrome, nickel, vanadium,
cadmium, vanadium pentoxide - the carcinogens as well as manganese which can
ultimately kill as well. Too much iron in a persons system can cause heart
attacks. Are we going to ban temmokus or saturated iron reds. I don't think so.
Let's face it, just about everything we use from cobalt to silica is
potentially harmful to us and/or our customers. We just have not go into panic mode
like some posters saying this or that material should never be used. We have
to be responsible on both sides of the equation.
Regards,
June
_http://www.shambhalapottery.com_ (http://www.shambhalapottery.com/)
_http://shambhalapottery.blogspot.com_
(http://shambhalapottery.blogspot.com/)
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(http://groups.yahoo.com/group/sodasaltfiring)
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Edouard Bastarache Inc. on thu 29 nov 07
Ron,
They also have kangaroos in Australia.
"When in Australia, do like the Australians."
There are also those who think they should
act as toxicologists without the proper
knowledge.
The standard you say is proposed in Australia
is the the same as for our drinking .
I do not think drinking water standards should
apply to metals leaching from utilitarian ceramic
wares; and I am not the only one to think so, even
on this list.
Gis la revido,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
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----- Original Message -----
From: "Ron Roy"
To:
Sent: Thursday, November 29, 2007 7:39 PM
Subject: Re: blistering glaze
> Well - there are toxicologists and there are
> toxicologists - they are just
> as many who think we should be a lot more
> careful than we are.
>
> As for legislators - I wonder what happened in
> Austria to make them think
> it was necessary?
>
> RR
>
>>Manganese and barium are not regulated
>>for use on utilitarian wares in most modern
>>countries, including Canada and the USA.
>>
>>I do not think we should take the place of
>>expert-toxicologists and legislators.
>>
>>Most clayarters, if not all of them, do not
>>know enough to play their role.
>>
>>Gis la revido,
>>
>>Edouard Bastarache
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
>
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Ron Roy on thu 29 nov 07
Not sure that is true.
Didn't David Hendly so some copper reds without zinc and barium and found
no difference?
Looks like there are some experiments to do here. Anyone who wants to have
any barium glaze reformulated without it - to see if it's really needed -
just let me know and I'll do some recalculation for you.
RR
>Ron,
>
>Small amounts of barium carbonate can aid in blue celadons, can influence
>copper reds, purples and blues, matte glazes will often use moderate
>amounts to modulate color, etc.
>
>John Britt
>www.johnbrittpottery.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ron Roy on thu 29 nov 07
Well - there are toxicologists and there are toxicologists - they are just
as many who think we should be a lot more careful than we are.
As for legislators - I wonder what happened in Austria to make them think
it was necessary?
RR
>Manganese and barium are not regulated
>for use on utilitarian wares in most modern
>countries, including Canada and the USA.
>
>I do not think we should take the place of
>expert-toxicologists and legislators.
>
>Most clayarters, if not all of them, do not
>know enough to play their role.
>
>Gis la revido,
>
>Edouard Bastarache
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
John Sankey on fri 30 nov 07
"Manganese and barium are not regulated
for use on utilitarian wares in most modern
countries, including Canada and the USA.
I do not think we should take the place of
expert-toxicologists and legislators."
As one with some 30 years experience in the health effects of
incidental pesticide exposure on those with respiratory
illnesses, I can assure you that "expert-toxicologists" are among
the nastiest and most narrow minded people I have ever met. Among
other things, they control our Canadian pesticide regulatory
agency and are so proud of their narrowmindedness that they have
refused to allow a single medical doctor to ever be involved in
the regulation of pesticides in Canada.
Legislators only act when need is made obvious to them. How is
anyone to know to what extent their health has been impaired by
the plates they eat from?
Edouard, you ought to pay more attention to the precautionary
principle. In the case of the terrible effects of pesticides on
those few with severe asthma and environmental illnesses, I can
assure you that it is needed in that area. I support Ron's
efforts to apply it to our pottery.
Vince asked, "Can the amount released at one time into one glass
of coffee or orange juice reach critical levels of toxicity?"
It's been shown many times that storage of acidic foods in
containers with leachable metals can do that within a few
days in a frig. So can heating of foods more than once in a
container.
--
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