Talbott on fri 31 oct 97
Uranium??? Are not most isotopes of uranium radioactive? Why use
radioactive materials in pottery? Have you heard of Marie Curie and how
she eventually died... Marshall
------------------------Original message--------------------------
>.....clip......
>
>If you can get it, uranium oxide gives a clear, warm, yellow at 4% in
>egyptian paste. A mixture of 2% copper carbonate and 2% uranium oxide gives
>a greeny-yellow quite different from the rather harsh lime green of chrome
>and the turquoise of copper by itself. Otherwise I can only suggest
>manganese oxide ................. zap...........You can buy Naples Yellow
>and it gives a pale yellow at 8% but not as nice as uranium. The trouble
>with uranium is I dont think you can get it any more- I got mine when you
>could.
>
>......snip.......
>
>This is targeted for those with a little less experience in ceramics
>possibly reading this stuff on the list.........
>
>PLEASE.... before you mix up this stuff with things like uranium oxide,
>Naples Yellow (god forbid) and other slightly less toxic stuff like
>chromium and manganese compounds, get a good look at a toxicological
>reference like "Artist Beware" by Dr. Michael McCann. Look up what you are
>about to put in.
>
>This is stuff you'll handle probably with bare hands for extended periods.
>It'll create dust in the studio. You probably want to know what you are
>intimately handling. For example, take a real good look at the info on
>Naples Yellow.
>
>This situation sort of relates to another post in the last day or so about
>the school banning chromium compounds. The comment was something like
>....why didn't they tell us...... and .......I thought if you could buy it
>it was safe or they would have to tell us.
>
>Well..... actually...... it doesn't happen that way in the real world.
>This stuff isn't taught very much, and many faculty don't know about it so
>they are not passing it on. MSDS are supposed to be available from
>suppliers but often you have to bust down the door to get them...... they
>are not often offered without asking.
>
>It behooves you to research the health and safety issues of ALL the
>materials you are handling and save yourself some possible suprises.
>Knowledge is power.
>
>
>Best,
>
>..........................john
>
>
>PS: I'm sorry, but I just can't help but be looking out a little bit for
>the non "tech-weenies" and the newer clay workers at times. Naples Yellow
>sounds like a really nice pretty thing..... (and it is )..... such a lovely
>name........and you can buy it by the 50 pound bag if you want to and can
>afford it. But it DOES have a real downside. So do other things we can
>use.
>
>
>John Baymore
>River Bend Pottery
>22 Riverbend Way
>Wilton, NH 03086 USA
>
>603-654-2752
>JBaymore@Compuserve.com
2nd ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
Details will be forth coming!!!
http://fmc.utm.edu/~dmcbeth/cag/naples.htm
Celia & Marshall Talbott, Pottery By Celia, Route 114, P O Box 4116,
Naples, Maine 04055-4116,(207)693-6100 voice and fax,(call first)
Clayarters' Live Chat Room, Fri & Sat Nites at 10 PM EDT & Sun at 1 PM EDT
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Gavin Stairs on sat 1 nov 97
A few years back, I was involved in a project in which we handled and
manufactured a physics detector out of tons of depleted uranium metal.
No-one died, or even got a dose of radiation much more than the normal
background. I realize that most of the people on this list haven't a clue
what that means, but maybe I can try to elucidate a bit.
Every second or so, an ionizing particle or gamma ray passes into our
bodies. Some come from outer space (cosmic rays) and some come from the
rocks and soil, mostly from decaying uranium and thorium contained in the
earth. People in Denver (about 1 mile higher than most of the rest of the
continent's population) absorb a bit more than the rest of us, because
there is less of the atmosphere to shield them from the cosmic rays.
People around certain parts of Chicago and Montreal, for example, also get
more because the rocks there contain more uranium and thorium than
elsewhere. It varies by a factor of two or more depending on the locality.
Most radiation regulations limit intentional exposures from concentrated
materials like uranium oxide to an amount not significantly different from
this background dose. Although some people dispute this, there is no
compelling evidence that such exposure carries a significant increased risk
of disease.
When we handle uranium, we have to take precautions against oxide particle
contamination, particularly with respect to risk of ingestion or
inhalation. The problem is that uranium emits a wide spectrum of ionizing
particles which, when lodged in an internal organ such as the lung, produce
a concentrated local risk of tissue damage and carcinoma. Uranium and
other radioactive materials, like thorium, have this risk in addition to
the ordinary risks of heavy metals. It is mostly this risk which makes
uranium oxide dangerous. Stringent protection procedures are necessary to
safely handle this material, especially as a finely divided powder, which
carries a definite risk of inhalation and ingestion. Such precautions
normally include contamination suits and air filters, contamination
monitoring and hot zone exclusion procedures, and may also include shielded
work stations and remote handling equipment. In other words, don't try
this at home.
Uranium exposure risks are not acute: you don't drop dead on the spot.
The effects only become apparent after a relatively long period of time, at
which point it may be too late to do anything about it. For this reason,
radiation has the spooky image of a silent killer. This makes it easy to
exaggerate the risks and inflate the fears. Radiation is an everyday risk,
akin to the risk of crossing a street. The risk is much greater in some
places than in others. We don't try to cross city thruways at rush hour,
because it is foolhardy. We don't hesitate to cross a country lane. And,
with precautions in place, we safely cross city streets every day. Yet
thousands of people lose their lives in this simple, everyday act every
year. That doesn't make us paranoid about street crossing. Nor should it
make us paranoid about radiation danger. It should make us assess the
risk, and act accordingly.
In the case of uranium oxide, I believe it is foolish, not to say illegal,
to handle it without precautions that are beyond the reach of most potters.
If you have more than a very small amount, you should probably get the
authorities to dispose of it safely. If you are dead set on using it, at
least observe stringent precaution to avoid inhaling any dust: filter mask
of the highest quality, avoid getting it on clothing, wash carefully after
every potential exposure. Get a radiation counter and check for leakage
and contamination. Do NOT dispose of it down the drain or in a landfill.
You are recklessly exposing other people without their knowledge.
Please also note that food ware with uranium oxide glaze is not legal in
many places.
Marie Curie died probably as a result of long exposure to many radioactive
isotopes in conditions that we would not at all countenance today. She was
concentrating radium, polonium and other radioactive elements by open
evaporation of salt solutions. Many of these materials are very much more
dangerous than uranium; particularly radium, which is very radioactive.
She worked daily, over many years, at high risk of contact with such
materials, and also absorbed many times the background rate of whole body
radiation while surrounded by tons of radioactive materials in her lab.
There was no shielding or contact protection, as radiation was then in its
infancy as a laboratory curiosity, and no-one knew of the dangers.
At 08:56 AM 31/10/97 EST, Marshall wrote:
>----------------------------Original message----------------------------
>Uranium??? Are not most isotopes of uranium radioactive? Why use
>radioactive materials in pottery? Have you heard of Marie Curie and how
>she eventually died... Marshall
stairs@echo-on.net
http://isis.physics.utoronto.ca/
416 530 0419 (home) 416 978 2735 (work)
Toronto, Ontario, Canada
Evan Dresel on mon 3 nov 97
Sigh, uranium again. All isotopes of uranium are radioactive. The three
isotopes which make up the bulk of natural uranium are uranium-234,
uranium-235 and uranium-238. Nearly all the uranium **by mass** is
uranium-238. However, approximately half of the radioactivity is from
uranium-238 and half from uranium-234. That's because uranium-238 decays to
uranium-234 and uranium-234 has a shorter half life. After a certain amount
of time the decay chain reaches steady state and the uranium-234 is decaying
at the same rate it is being produced. Uranium-235 produces very little of
the radioactivity because there is little of it present (it is however very
important to those in the massive eistruction business). In depleted
uranium some of the uranium-235 has been removed. Almost certainly an even
greater proportion of the uranium-234 has also been removed. How much, I
don't know. All of the uranium isotopes are alpha emitters. That means the
radioactivity can be stopped by a piece of paper or the dead-layer of your
skin. Alpha particles however, can be quite destructive once in your body
-- particularly if inhaled into your lungs. Here's the catch -- all the
isotopes of uranium have extremely long half-lives. What that means is that
there isn't much radiation unless you have a whole lot of the stuff. The
proposed drinking water standard for uranium in the US is set mainly by it's
possible chemical effect on the kidneys, not on its radioactivity. My
suspicion is that uranium is fairly benign in glazes but haven't done enough
research. I strongly disagree with the answer, "It's radioactive, it will
kill you and your customers."
If you don't want to use radioactive materials in your pottery, you better
stop using potash-feldspar and probably nearly every clay. Potassium-40 is
present in all potassium containing materials and is quite radioactive. You
can measure the radioactivity from the potassium in fertilizer using a
simple hand-held geiger counter.
Just trying to put things in perspective.
-- Evan in W. Richland WA where winter is just around the corner
At 08:56 AM 10-31-97 EST, Marshall wrote:
>----------------------------Original message----------------------------
>Uranium??? Are not most isotopes of uranium radioactive? Why use
>radioactive materials in pottery? Have you heard of Marie Curie and how
>she eventually died... Marshall
> ------------------------Original message--------------------------
George Mackie on thu 6 nov 97
It was me who opened the can of worms by mentioning uranium oxide as a
yellow colouring agent in Egyptian paste when a woman in Australia,
Deoborah Zinn, posted an enquiry on this topic. I also mentioned Naples
Yellow, and opened another Pandora's box with that. I just want to say
here that the Naples Yellow I had in mind was the Mason Stain, which is
formulated without lead or antimony, so is not deadly. It is praseodymium
basically. They shouldnt really call it Naples Yellow, which though
hazardous, has a long and honourable history back to Roman times. As for
Uranium, clearly the potter who uses it should avoid inhaling it but the
beads I made with it gave off no more radioactivity than the background
level in the lab where they checked it for me. I thought of putting
"Ravaged by Guilt" as the subject of this letter but it would be a lie.
All potters surely know by now that some of the products they handle are
potentially hazardous and I just assumed Deborah knew this - also I
doubted very much if she could get uranium oxide even in Australia that
land of rugged individualists. George
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