Karl P. Platt on wed 2 apr 97
I don't know who wrote:
> .Lead is a different story...there are many elements that are more
> dangerous than Barium.. Cadmium, Celenium, Vanadium, Strontium <
You should really watch out for di-hydrogen oxide. Too much or too
little of that and you die. Unfortunately, it's everywhere and I hear
the EPA is considering a process against God for this misery.
And:
>I think you will have trouble finding a case of Barium poisoning in the USA<
They simply don't exist outside of really whacky extremes such as:
To which Monona replied:
>>There was a case of a girl who poisoned her father a few years ago with barium
Of course, this has nothing to do with ceramic glazes. It's just an
extreme anecdote.
>> Further, It is very unlikely that barium glazes that have been "properly fir
And Monona Replied:
>>I rely on the good potters of Clayart to take issue with this statement.<<
I'm a lousy potter and I will speak on behalf of the presence of Ba in
ceramic glazes.
Leaching of Ba from a ceramic glaze has a couple of aspects worth
considering. Ba can exist in a glaze either as a component in a
crystalline material, BaSiO3, for example or it can be involved in the
glassy material present as an ion. Let's be clear that Ba isn't sitting
about in the glaze freely waiting to leap off and corrode someone's
health.
The Ba ion is very large. it's the larges ion you'll meet in a glaze. As
such it isn't the most likely candidate to be extracted by any corroding
solution. It's fat, er, gravitationally challenged, and has a hard time
being squeezed out of a glaze. Among the our monovalent friends (the
"RO" materials) Mg, because it's tiny, is the most likely to go into
solution. Solubility is also a very strong function of temperature. If
the "standard"leaching test referred to above was of the "accellerated"
variety which uses hot acetic acid (vinegar), then the results were
seriously skewed -- indeed, Ba tends to be released more readily than
the other Ro components. Of course no-one drinks hot vinegar -- or cold
vinegar for that matter.
Noting the above, one should be clear that BaO, CaO, MgO, etc, are the
least likely characters to come out of a glaze and go into leaching
solution. Actually, the first to go are the alkalies.
Leaching, apart from the chemical constitution of the glaze, depends on
a variety of factors such as:
The ratio of leaching solution to the surface of the container
The "specific surface" presented by the surface -- Shiny glaze surfaces
actually present a vastly smaller surface area to reaction than matte
glazes.
Whether or not the solution is agitated has huge effects.
The time of contact is a critical factor, too. Here remember that the
residence time of any sort of foodstuff in contact with the glaze is
usually limited to the course of a dinner --- not hours. However, one
wants to remember that ovenware is subject to the higher reaction rates
one sees at elevated temperatures -- ie, leaching, if it can occur, will
do so at an accellerated rate.
I hate being redundant, but I want to mention again my experiences
making chemical vat lining tiles. The glaze contained about 4% BaO and
the tiles never failed, showed color changes or spoiled product owing to
leaching. These were used in a variety of applications which included
heated inorganic acids, etc., including applications in the foor
processing industry.
The point is that condemning this or that glaze component as a matter of
ideology is, well, dumb. i. "Barium is BAD" Remember that the US
tableware industry used fritted lead glazes for decades and decades
without any recorded incident. Out of the Millions of items of trouble
free tableware made by US producers, the only documented cases of
leaching problems (poisoning) have been with foreign products.
Especially rustic stuff from Latin America where smearing litharge onto
a pot passes for glazing in a lot of places. Untold thousands of
man-hours have gone into studying making stable glazes and this wealth
of information is free to anyone who wants to go look it up.
>>the EPA set a barium maximum contaminant level for your
drinking water at 2 ppm.<<
This is practically 2 orders of magnitude higher than PB or Cd leaching
standards in the TCLP test -- which is another useless exersize.
If so desired, I'd be happy to take this out to more detail -- anyone
interested in studying the thermodynamics of these corrosion reactions?
It's very worthwhile from the perspective that they show quite plainly
that under all but real extreme cases there's more danger walking across
NeW York's West Side Highway at 4:30 PM or in breathing in LA on a hot
August afternoon.
OK, all that said, I'm off to eat.
Karl P. Platt
27 degrees south studying silver in glassy things
Nils Lou on mon 7 apr 97
Karl, Thanks for the warning. I have been using di-hydrogen oxide
ROUTINELY all my life and now I am suffering the consequences. My bones
ache when I get up in the morning, I need glasses to watch the movies, and
my skin is definately beginning to wrinkle. My doctor says there is no
cure AT ALL! I have even lost 10 to 12 yards on my drives. What am I to do
now that it is too late? Shall I give up making pots? Somebody out there
help pass the word. It is just too dangerous.....drifting off. Nils
Karl David Knudson on wed 9 apr 97
> ----------------------------Original message----------------------------
> Karl, Thanks for the warning. I have been using di-hydrogen oxide
> ROUTINELY all my life and now I am suffering the consequences.
Isn't di-hydrogen oxide also notorious for the fact that the government
has been secretly pumping it under major cities for years now?
Conspiracies abound as to the purpose of that.
The other Karl
HOSKISD@fsa.wosc.osshe.edu on wed 9 apr 97
>From: Nils Lou
>Subject: Re: Ba leaching.....again and again and again
>To: Multiple recipients of list CLAYART
>
>----------------------------Original message----------------------------
>Karl, Thanks for the warning. I have been using di-hydrogen oxide
>ROUTINELY all my life and now I am suffering the consequences. My bones
>ache when I get up in the morning, I need glasses to watch the movies, and
>my skin is definately beginning to wrinkle. My doctor says there is no
>cure AT ALL! I have even lost 10 to 12 yards on my drives. What am I to do
>now that it is too late? Shall I give up making pots? Somebody out there
>help pass the word. It is just too dangerous.....drifting off. Nils
Nils,
Let me recommend altering the di-hydrogen oxide with combination of
(in varying amounts): sodiuum benzoate, fructose, phosphoric acid, esters,
and carbonic acid. This is a combination to be used for moderate internal
consumption. In sufficient amounts it will add girth (to you not your drive).
It may also help you to forget the aching bones, and depending on how
many internal applications, may help fill out the layer under the skin so
wrinkles are not as noticable. Things could be worse. Some parts of
the country are presently suffering from a flood of di-hydrogen oxide.
Don
Don Hoskisson
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