June Perry on mon 4 dec 00
Cindy, I ran this on my glaze software and it has a high silica to alumina
ratio (9+), which would put it in the gloss category. It is also very high in
calcium, which I suspect, if fast cooled and held 200degrees below top
temperature for a couple of hours, would probably go more matt, because of
calcium and barium crystals forming.
I have a friend who has a gorgeous cone 6 calcium eutectic matt which she
fires with her cone 6 crystalline glazes, using the technique mentioned
above. The same glaze in a regular cone 6 firing is on the shiny side.
This glaze would also go more matt if you dropped the silica down to 5 and it
would still be in a cone 6 silica range according to my program; but it would
raise the expansion of the glaze.
In addition, you could try adding some calcined kaolin 2-5% or about 2%
alumina hydrate to matt it some more.
The glaze has 1+% iron which is acting as a color modifier for the cobalt.
You can try subbing grolleg for the ball clay to lower the iron a bit and to
lower the titanium which is contributing to the green color. You will still
have a bit of iron and titanium from the pumice, but the substitution of the
grolleg, which has no titanium and less than half the iron of the OM#4 ball
clay, may help a little.
My glaze program shows calcined kaolin as being iron and titanium free, so
using more of the calcined would also lower the overall iron content a bit
and also matt the glaze a bit more because of it's higher alumina, lower
silica content than ball clay or regular kaolin.
Regards,
June (finally got the new Skutt pro operating and am doing the first breaking
in bisque firing!).
Cindy Strnad on mon 4 dec 00
Hi, guys.
I did a bit more testing on some of the glazes I posted here last time, and
came up with one puzzling result. Not an unpleasant result, but not at all
what I was expecting. The glaze in question is:
Volcanic Blue Matte ^6
PUMICE 40
WHITING 20
BARIUM CARBONATE 5
OM #4 BALL CLAY 20
FLINT 15
First off, I'm not sure where the "matte" comes from, as the glaze has never
turned out matte for me, even with a fire-down, but that's beside the point.
It's a nice satin, and I'm pleased with its surface. It's the color that's
got me scratching my head.
The recipe calls for 0.5 percent Cobalt Oxide. I tried it with that (long
ago) and got a nice gray-blue, which wasn't what I was looking for at the
time. So now I'd like that for a piece I had in mind, but I tried it with 1%
Cobalt Carbonate just for variety's sake. I got a saturated "candy" blue
that I didn't care for much. Nice, if that's what you want, but I want the
sky just after twilight has passed, but before full dark. So, that wasn't
quite the thing.
Soooo, I thought, well, heck, I'll just add some iron or rutile. I thought
maybe rutile might wash out the darkness a bit, so I went with iron.
It's green. Very nice dark, subdued forest green, but
not quite the thing, you know?
(In case anyone wants a nice forest green from cobalt carbonate: I added 5%
red iron oxide.) And yes, the glaze is thick enough. In fact, it's greenest
where it's thickest. Nary a hint of blue at all, at all. Of course, your
pumice is likely from a different volcano than mine, and you may not get the
same results, but it's worth a try.
I'm sure switching back to the specified cobalt oxide will meet all my
needs, but this puzzle is puzzling me. Why would iron make the cobalt turn
green? I thought it was rutile/titanium that did that? And if there's some
odd ingredient in the pumice that turned it green, why didn't it do that
anyway, without the iron?
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Paul Lewing on tue 5 dec 00
June Perry wrote:
> My glaze program shows calcined kaolin as being iron and titanium free, so
> using more of the calcined would also lower the overall iron content a bit
> and also matt the glaze a bit more because of it's higher alumina, lower
> silica content than ball clay or regular kaolin.
June, your other advice was pretty dead on, but I think you're trusting
your software's database a little too much on this one. Calcining
kaolin should have no effect on the iron or titanium content. All you
lose in calcining is organic stuff and hydroxyls (chemically combined
water). So for calcined kaolin to be free of Fe and Ti, the original
must also be.
Paul Lewing, Seattle
Chris Clyburn on mon 26 jul 04
I just finished firing a large batch of glaze tests. BTW thanks to everyone
on their advice on the purple glazes, using soda spar vs. potash spar. I
wound up finding an old, well hidden supply of F-4, so I didn't need to
substitute.
The weird thing is, I tired a glaze that was supposed to be matte white and
instead turned out to be a crystalline-like glaze with a white snowflake
pattern over a pale blue background. The oddest thing about this was the
glaze does not run at all, and was not fired on a crystaline firing
schedule. It was loaded with a lot of zinc though (which if I remember
correctly, zinc is the source of crystals in crystalline glazes.)
Any way, it was a ^6 firing, and my fring schedule was 100F/hr to 200, hold
for 5 hours, 150F/hr to 1400, the 270/hr to 2232. The 200 soak time was
becuase I was testing each glaze for results in raw glazing and biqued
glazing. The glaze recipe follows:
Lithium carbonate 12
Whiting 5
Kaolin 28
Flint 55
(+) Titanium dioxide 8
(+) Zinc oxide 25
I realize this is most likely not a food safe glaze, due to lithium and high
zinc content. I was wondering if anybody could tell me how I wound up with a
non-fluid crystaline glaze without any soak times? I'm not complaining, it
is the beautifal glaze, it's just a bit odd from what I know of glaze
chemistry (which admitidly is a bit limited).
Chris Clyburn
Lee Love on mon 26 jul 04
Chris Clyburn wrote:
>. The 200 soak time was
>becuase I was testing each glaze for results in raw glazing and biqued
>glazing.
>
Chris,
Did you get the same results on both once fire and bisque?
On your once fire, was it glazed green or leather hard?
--
Lee in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
Edouard Bastarache Inc. on tue 27 jul 04
Paul,
right on !!!
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: "Paul Lewing"
To:
Sent: Tuesday, July 27, 2004 11:03 PM
Subject: Re: weird glaze results
> on 7/25/04 10:10 PM, Chris Clyburn at chris_clyburn@COX.NET wrote:
>
> > I realize this is most likely not a food safe glaze, due to lithium and
high
> > zinc content.
>
> Hi, Chris. What's your problem with zinc?
> It's bad enough that people avoid lithium because a few people speculate
> that there might possibly be a problem for a tiny percentage of the
> population, even though there is no scientific study that has proved any
> harm from leached lithium.
> But zinc oxide has been used safely in glazes for hundreds of years, and
was
> the chemical of choice to replace lead back in the 19th century. Do you
> have some new information on this?
> By the way, this glaze also has silica in it, which we do know causes
> silicosis. Let's not get paranoid here.
> Paul Lewing, Seattle
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
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melpots@pclink.com.
>
>
Ivor and Olive Lewis on tue 27 jul 04
Dear Chris Clyburn,
Have you missed out one or more of your ingredients from your basic
glaze before you add the Titanium and zinc oxides?
You give
> Lithium carbonate 12
> Whiting 5
> Kaolin 28
> Flint 55
> (+) Titanium dioxide 8
> (+) Zinc oxide 25
If you have not you may have discovered an new species of crystal
which no one has experienced before.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Chris Clyburn on tue 27 jul 04
On Tue, 27 Jul 2004 11:27:43 +0930, Ivor and Olive Lewis
wrote:
>Dear Chris Clyburn,
>Have you missed out one or more of your ingredients from your basic
>glaze before you add the Titanium and zinc oxides?
>You give
>> Lithium carbonate 12
>> Whiting 5
>> Kaolin 28
>> Flint 55
>> (+) Titanium dioxide 8
>> (+) Zinc oxide 25
>If you have not you may have discovered an new species of crystal
>which no one has experienced before.
>Best regards,
>Ivor Lewis.
>Redhill,
>S. Australia.
Ivor,
I have triple checked the ingredients, and the glaze is the way it was
written down. If I have found a new crystal glaze, I cannot, unfortunately,
take credit for it. I am in a school environement, and I needed a matte
white this trimester and didn't have time to develop one, (like the purples
I needed in my previous post. I found this recipe in our archives. No author
was given and it was simply called matte white. It listed the results simply
as a buttery matte white with no texture. The only things I can think of
causing this odd result of crystals froming in a non-fluid glaze with no
soak times without it being noted by whoever formulated the recipe
originally would be: 1. the original creator mixed their test wrong (I take
notes after adding each ingredient to double check myself), 2. Our chemicals
may be contaminated (it is a school after all) or 3. Somehow the results
have to do with my firing schedule.
I am hopefully going to test this glaze again before the end of the week, to
see if I can duplicate the results as well as trying for some color
variations adding various oxides. Unfortunately, this trimester I do not
have time to test variables in the firing schedule. and I have no way of
testing with ingredients I know are pure and uncontaminated.
If anybody tries this glaze and gets similar, or differnet results, I would
be very interested to hear from them. I will try and photograph the test
piece before I leave for vacation this week and will post a link If I get it
done in time.
Chris Clyburn
Paul Lewing on tue 27 jul 04
on 7/25/04 10:10 PM, Chris Clyburn at chris_clyburn@COX.NET wrote:
> I realize this is most likely not a food safe glaze, due to lithium and high
> zinc content.
Hi, Chris. What's your problem with zinc?
It's bad enough that people avoid lithium because a few people speculate
that there might possibly be a problem for a tiny percentage of the
population, even though there is no scientific study that has proved any
harm from leached lithium.
But zinc oxide has been used safely in glazes for hundreds of years, and was
the chemical of choice to replace lead back in the 19th century. Do you
have some new information on this?
By the way, this glaze also has silica in it, which we do know causes
silicosis. Let's not get paranoid here.
Paul Lewing, Seattle
Ron Roy on wed 28 jul 04
This glaze is short of both silica and alumina so it is not going to be a
stable glaze in use.
The expansion is quite low as well so it will break pots when inside some
clay bodies and perhaps shiver as well - it should be very carefully tested
for fit on each clay you want to use it on,
The Lithium carb is very high - this can result in some very unusual fit
problems on some clay bodies. I would only recommend 2% lithium carb in a
glaze.
It would be quite easy to raise the expansion to a safer level by subbing
in some KNaO for some of the Lithium - and use some Spodumene as a Li2O
source.
to get the Carbonate down to 2%.
I am not surprised to hear that it melted at cone 5 - Zinc is a well know
melter at that temperature.
RR
>Lithium carbonate 12
>Whiting 5
>Kaolin 28
>Flint 55
>(+) Titanium dioxide 8
>(+) Zinc oxide 25
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on mon 2 aug 04
I wonder why why Austria specifies that glazes leach less than 3 mg/L?
Perhaps unstable glazes that leach Zinc into food affect the taste of that
food - that alone would be a good reason to at least find out how much is
leached.
There are no specific hazards listed in my references aside from the metal
fume fever that can happen from firing fumes.
Certainly a better idea to use stable liner glazes anyway - seeing as it is
not our job to be providing trace minerals to our customers.
Why not try a bit of zinc in your orange juice just to see if it improves
the taste.
By the way Paul - what has silica in a glaze got to do with silicosis -
don't you have to breath silica dust to get silicosis?
RR
>Hi, Chris. What's your problem with zinc?
>It's bad enough that people avoid lithium because a few people speculate
>that there might possibly be a problem for a tiny percentage of the
>population, even though there is no scientific study that has proved any
>harm from leached lithium.
>But zinc oxide has been used safely in glazes for hundreds of years, and was
>the chemical of choice to replace lead back in the 19th century. Do you
>have some new information on this?
>By the way, this glaze also has silica in it, which we do know causes
>silicosis. Let's not get paranoid here.
>Paul Lewing, Seattle
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Paul Lewing on tue 3 aug 04
on 8/2/04 6:06 PM, Ron Roy at ronroy@CA.INTER.NET wrote:
> By the way Paul - what has silica in a glaze got to do with silicosis -
> don't you have to breathe silica dust to get silicosis?
Of course. That just goes to prove my point that, if you're going to
eliminate everything from your studio that's potentially harmful under any
circumstances, you can't work with clay or glazes at all.
Silica, unlike zinc, has been proven to be harmful under some circumstances
(such as airborne dust). It's in much the same category as my example of
strontium. If you didn't know, you'd hear that strontium was radioactive,
so you wouldn't use it in your glazes. Well, it's not in the form that
potters use it. In the same way, one could hear that silica causes
silicosis, without getting the fact that that doesn't apply if it's wet or
if it's fired.
I just didn't want anyone to get the idea from Chris' post that zinc was
harmful, which someone could easily have inferred from that.
Paul Lewing, Seattle
Ron Roy on wed 4 aug 04
Hi Paul,
I'm not following the logic here - if potters don't ask questions - how
will we find all this out?
You seem to be saying - don't ask certain questions about materials unless
you know there is a problem - surely you can see the catch 22 in this?
Is it not better that we know what the problems are so we can protect
ourselves and make better ware - or should we just wander around in
isolation and hope we are doing the right thing.
You seem to be saying - lets not talk about these things - so potters will
not be afraid of everything. Does it not make sense to talk about it and
find out what the problems are - if any - with our materials - so we can
make more informed decisions about how to handle and use them?
There are some very good reasons for not using some materials - unless you
understand the problems how do we find out how to use them in a safe way.
It is one of the best parts of ClayArt - potters discussing the issues and
finding ways to cope with the problems. I don't see how asking anyone not
to talk about something solves anything.
RR
>> By the way Paul - what has silica in a glaze got to do with silicosis -
>> don't you have to breathe silica dust to get silicosis?
>
>Of course. That just goes to prove my point that, if you're going to
>eliminate everything from your studio that's potentially harmful under any
>circumstances, you can't work with clay or glazes at all.
>Silica, unlike zinc, has been proven to be harmful under some circumstances
>(such as airborne dust). It's in much the same category as my example of
>strontium. If you didn't know, you'd hear that strontium was radioactive,
>so you wouldn't use it in your glazes. Well, it's not in the form that
>potters use it. In the same way, one could hear that silica causes
>silicosis, without getting the fact that that doesn't apply if it's wet or
>if it's fired.
>I just didn't want anyone to get the idea from Chris' post that zinc was
>harmful, which someone could easily have inferred from that.
>Paul Lewing, Seattle
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ivor and Olive Lewis on wed 4 aug 04
Dear Paul Lewing,
An interesting point you make about radioactivity. No, there are no
naturally occurring isotopes of Strontium. What we have in the West
Pacific region is all attributable to the testing of Atomic Devices.
But there is one naturally occurring radioactive isotope of Potassium
which we conveniently ignore because we cannot avoid it. It is part of
our diet, is parcelled into our forms and has been so for an aeon,
since our primordial ancestors emerged in primeval ooze. Look for
Potassium 40, 0.0118% atomic abundance.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
.
Lee Love on wed 4 aug 04
Paul Lewing wrote:
>I just didn't want anyone to get the idea from Chris' post that zinc was
>harmful, which someone could easily have inferred from that.
>
>
Zinc is prescribed in cases of lead exposure. Taking zinc supplements
helps keep environmental lead from being taken up by the body. I
take a tab every day that includes calcium, magnesium and zinc.
--
in Mashiko, Japan http://mashiko.org
http://www.livejournal.com/users/togeika/ WEB LOG
http://public.fotki.com/togeika/ Photos!
Paul Lewing on thu 5 aug 04
on 8/4/04 8:03 PM, Ron Roy at ronroy@CA.INTER.NET wrote:
> You seem to be saying - don't ask certain questions about materials unless
> you know there is a problem - surely you can see the catch 22 in this?
I never said anything even remotely like that. What I keep trying to say is
that people hear a snippet of information, don't question it, take it as
fact, and act on it. Like my example of people hearing that strontium is
radioactive, so they quit using it. What I was trying to prevent here in
the first place was people reading the statement that a glaze couldn't be
food-safe because it had zinc in it, and assuming that that was true without
questioning it.
Of course people should ask questions. Who would ever assert otherwise?
Paul Lewing, Seattle
Paul Lewing on sun 8 aug 04
on 8/8/04 6:09 AM, Ron Roy at ronroy@CA.INTER.NET wrote:
> Which leads to what this is all about - and what would be the best way to
> answer such questions or talk about dubious statements? How do we try to
foster open discussions here?
I agree, Ron. That is the bottom line. I've said many times that every
clay worker needs to decide for her- or himself where to draw the line on
potential risk to themselves and their customers. I've also said before
that it is not possible to draw the line at zero tolerance for materials
that are hazardous in some situation, and still work with clay and glazes.
And the only way anyone can make that decision is by educating themselves.
I also know from years of reading your posts and talking to you in person,
that you and I draw that line in different places. I completely respect
your perspective, but it is not mine. I'm much more likely to use a
material that might be hazardous to me than you would be, and I don't make
food-related ware, so that's not an issue for me.
>
> Part of the problem here is the term food safe.
I agree here, too. I think people want a simple yes-or-no answer about
whether something is OK to use, and it's not that simple.
If someone says there is no
> problem with zinc being food safe it raises other questions - specifically
> - is it wise to use a zinc glaze as a liner if that glaze is going to
> release tastable amounts of zinc into food?
Of course not. But that's a separate issue from whether the zinc will hurt
you or not. And it has more to do with the composition of the glaze than
the fact that it has zinc.
>
> By the way - Strontium carbonate always has some Barium carbonate
> associated with it - a small amount. In Austria and Slovinia Barium is
> controlled (1 mg/L) and Lee says Japanese potters are not allowed to use
> Barium. Is it possible that a glaze - loaded with Strontium - will leach
> enough Barium to be considered illegal in those countries?
Contrast this line of reasoning with Edouard Bastarache's recent contention
that there has never been a documented case of anyone being harmed by barium
leached from pottery. What happens is that those people who have already
eliminated barium from their repertoire now also eliminate strontium on the
chance that it might have a little barium in it. This without any testing,
or documentation, or even investigation to see if there is, in fact, barium
in their strontium. No attempt to see if the particular glazes they use
containing strontium release any of it at all, much less any barium.
The result is another material stigmatized, which is just what I was trying
to prevent in the case of zinc.
All I'm saying is that there's a risk in everything you do. It's up to you
to decide what's an acceptable level. And that only comes with education
and thought.
Paul Lewing, Seattle
Ron Roy on sun 8 aug 04
Hi Paul,
Which leads to what this is all about - and what would be the best way to
answer such questions or talk about dubious statements?
How do we try to foster open discussions here?
Part of the problem here is the term food safe. If someone says there is no
problem with zinc being food safe it raises other questions - specifically
- is it wise to use a zinc glaze as a liner if that glaze is going to
release tastable amounts of zinc into food?
My point is that durability is also part of the issue and even though zinc
is not labeled toxic - there are certain zinc glazes that should not be
used as liners because of other factors.
By the way - Strontium carbonate always has some Barium carbonate
associated with it - a small amount. In Austria and Slovinia Barium is
controlled (1 mg/L) and Lee says Japanese potters are not allowed to use
Barium. Is it possible that a glaze - loaded with Strontium - will leach
enough Barium to be considered illegal in those countries?
RR
>I never said anything even remotely like that. What I keep trying to say is
>that people hear a snippet of information, don't question it, take it as
>fact, and act on it. Like my example of people hearing that strontium is
>radioactive, so they quit using it. What I was trying to prevent here in
>the first place was people reading the statement that a glaze couldn't be
>food-safe because it had zinc in it, and assuming that that was true without
>questioning it.
>Of course people should ask questions. Who would ever assert otherwise?
>Paul Lewing, Seattle
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on mon 9 aug 04
Hi Paul,
Yes - we will agree to disagree - I say know your materials and design our
discussions so everyone feels free to ask about anything - and answer
questions in a way that promotes the idea that - the more we know - the
better we will be able to make functional pots.
By the way - did you not see that there were many people killed in South
America - when they used the wrong Barium compound for x-raying?
To imply that Barium has no adverse health effects is simply not realistic
by the way. It is an effective rat poison - that should make anyone
cautious for starters. One of the problems with Barium poisoning is - it's
difficult to diagnose if you are not looking for it. The effect - for one -
is the how it tends to paralyze muscles - so heart failure would be one of
the effects.
It is common practice to state dose by body weight - so how much Barium
would it take to affect a one pound fetus - I have asked that question many
times on this list - and there has never been an answer. What is it about
that question that is so hard to talk about?
So how much Barium is there in Strontium, and if you have 40% strontium in
a glaze - and it is grossly unstable - how much would leach into coffee?
I don't find this kind of discussion scary - I find it interesting - and if
it brings up questions that can't be answered I can decide for myself on
how to act.
As for zero tolerance - it is impossible - who ever said that? It is
certainly not a good argument to not inform ourselves about our materials.
I clipped out most of our discussion - it was getting too long - not trying
to be underhanded - RR
>> By the way - Strontium carbonate always has some Barium carbonate
>> associated with it - a small amount. In Austria and Slovinia Barium is
>> controlled (1 mg/L) and Lee says Japanese potters are not allowed to use
>> Barium. Is it possible that a glaze - loaded with Strontium - will leach
>> enough Barium to be considered illegal in those countries?
>Contrast this line of reasoning with Edouard Bastarache's recent contention
>that there has never been a documented case of anyone being harmed by barium
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Paul Lewing on tue 10 aug 04
on 8/9/04 11:55 AM, Ron Roy at ronroy@CA.INTER.NET wrote:
> I say know your materials and design our
> discussions so everyone feels free to ask about anything - and answer
> questions in a way that promotes the idea that - the more we know - the
> better we will be able to make functional pots.
Amen.
>
> By the way - did you not see that there were many people killed in South
> America - when they used the wrong Barium compound for x-raying?
>
> To imply that Barium has no adverse health effects is simply not realistic
> by the way. It is an effective rat poison - that should make anyone
> cautious for starters.
But this example isn't realistic either. Comparing the risk from drinking a
glassful of a barium compound to the risk from barium leached from pottery
is like comparing the risk of dying from smoke inhalation when you're
trapped in a car fire to the risk of emphysema from second-hand smoke. Not
anywhere near the same level of dosage, exposure or risk.
And the other question this example brings up is this: If those people
drank the "wrong" form of barium in a medical procedure, obviously there was
a "right" form. Is the form leached from glazes the "right" form, the
"wrong" form, or another form entirely? And is the compound leached from
pottery the same as rat poison?
Paul Lewing, Seattle
Ron Roy on wed 11 aug 04
Hi Paul,
Yes - you are right - drinking barium Carb. is not the same - I was not
saying that - I am saying that Barium is a poison.
You can try to say that the oxide form is different from the leached form
or the soluble form - I don't think there is any reason to make the
assumption that any of those would not be harmful. Just look at lead as an
example.
I don't know enough about that to say - but I would expect the leached
metal would be more concentrated. Anyone have any hard info about that?
You can recommend using poisons in glazes if you want - I don't think it's
a good idea for potters who make functional pots - unless you know how to
make stable glazes - and have the testing done to prove them stable.
It will not be hard to find toxicologists that say it does not mater - but
for everyone you find that does - I will find another who says it is wrong
to use poisonous materials in unstable glazes.
RR
>But this example isn't realistic either. Comparing the risk from drinking a
>glassful of a barium compound to the risk from barium leached from pottery
>is like comparing the risk of dying from smoke inhalation when you're
>trapped in a car fire to the risk of emphysema from second-hand smoke. Not
>anywhere near the same level of dosage, exposure or risk.
>And the other question this example brings up is this: If those people
>drank the "wrong" form of barium in a medical procedure, obviously there was
>a "right" form. Is the form leached from glazes the "right" form, the
>"wrong" form, or another form entirely? And is the compound leached from
>pottery the same as rat poison?
>Paul Lewing, Seattle
>
>______________________________________________________________________________
>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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Earl Krueger on thu 12 aug 04
Yin or Yang?
Bad or Not Bad?
Any or None?
Idealism because it's easier to deal with.
The real world is fuzzy.
Sorta Yes, Sorta No.
0.6 Bad, 0.4 Not Bad.
There's been no fuzziness in this discussion?
Since the current concern is Barium what are
the fuzzy characterizations? Is:
One part per Million "Really Bad",
One part per Billion "Sorta Bad",
One part per Trillion "Somewhat Bad",
Ten atoms per cubic centimeter "Very Marginally Bad"?
What's the background noise on Barium consumption?
How much does eating from a plate with Barium glaze
add to this; 0.1%, 1%, 10%.
To discuss this in a Real-World context we must move
beyond Yin and Yang and answer the difficult questions.
Earl K...
Bothell, WA, USA
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