vince pitelka on mon 13 nov 00
This has come around many times on Clayart, but it is important to mention
it again whenever anyone asks. Powdered manganese dioxide and chrome oxide
are not toxic in skin absorption in the raw state, because the particles are
far too large, and are not soluble. But don't breath the dust, and above
all do not breath the firing fumes.
Like so many other ceramic materials that are toxic under certain
circumstances, these seem to be fine if present in reasonable amounts locked
in a stable glass.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@dekalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
http://www.craftcenter.tntech.edu/
audrey leung on mon 13 nov 00
hello,
i'm sure there's someone out there who knows this topic well. please
enlighten the rest of us!
1) is it toxic in dust form only, or also in liquid form through the skin?
2) is it toxic to touch AFTER it's been fired (like on the outside of a teapot)?
3) and i assume it's not for use on food-contact surfaces. true?
4) what would be the appropriate and reasonable precautions? respirators?
rubber gloves? kiln venting? not using it?
thanks so much,
audrey leung
--- Karen Sullivan wrote:
> Studio Potter magazine ran an article about David Shaner,
> I am not sure how long ago, but within the last six months.
> Great article. Tony Clennell just mentioned it a few days ago.
> What is important to know is that Shaner was working with
> manganese dioxide in his glazes which developed a matt/crystal
> surface that was quite beautiful...He was firing his kiln inside
> his studio, and therefore was breathing the fumes that came from
> the kiln.
> He started having sever physical problems, and it took a few
> years for the medical evaluation to figure out that he had
> heavy concentrations of metal in his system...the article gives
> a detailed medical description. What I remember is that the metal
> had bonded on a cellular level with the oxygen molecules in his
> blood system.
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dan mickey on mon 13 nov 00
audrey,
I think the post that tony put up may start a large and maybe (i hope not)
heated debate. I am no expert and hardly ever follow the rules, BUT; i AM
positive that in dust/powder form manganese diox. is toxic also exposing
bare skin is'nt wise either. I would think that as a food safe glaze it is
also dangerous, but i don't know if glaze stability would matter or not. as
far as touching after use, as long as the material in question is in a glass
matrix i don't think touching it would be dangerous. Appropriate
precautions: I think the glaze David used is beautiful alright, and many
other people have, and are using it currently. so to say don't use it may be
a little harsh. as with any ceramic material; wear a mask, the rubber gloves
are also a good idea when working with manganese dry or wet. Kiln venting is
what the real issue is though. If youve read the article by david and also
saw my post when this first came up, then you know that the fumes from the
kiln are what did david in. He states that he took all the precautiions when
mixing and glazing, so he realized that his kiln was indoors and not vented
properly, I am sure his stack went through the roof but it was from looking
in the kiln all the time and those fumes were coming out during the firing.
I hope that i am relating this info the same as it was written, i haven't
read the article in awhile. but don't worry as i am sure you will recieve
many posts on this. Vince are you out there? i think you can shed some light
on this!
later
shane mickey
> hello,
> i'm sure there's someone out there who knows this topic well. please
> enlighten the rest of us!
> 1) is it toxic in dust form only, or also in liquid form through the
skin?
> 2) is it toxic to touch AFTER it's been fired (like on the outside of a
teapot)?
> 3) and i assume it's not for use on food-contact surfaces. true?
> 4) what would be the appropriate and reasonable precautions? respirators?
> rubber gloves? kiln venting? not using it?
> thanks so much,
> audrey leung
>
> --- Karen Sullivan wrote:
> > Studio Potter magazine ran an article about David Shaner,
> > I am not sure how long ago, but within the last six months.
> > Great article. Tony Clennell just mentioned it a few days ago.
> > What is important to know is that Shaner was working with
> > manganese dioxide in his glazes which developed a matt/crystal
> > surface that was quite beautiful...He was firing his kiln inside
> > his studio, and therefore was breathing the fumes that came from
> > the kiln.
> > He started having sever physical problems, and it took a few
> > years for the medical evaluation to figure out that he had
> > heavy concentrations of metal in his system...the article gives
> > a detailed medical description. What I remember is that the metal
> > had bonded on a cellular level with the oxygen molecules in his
> > blood system.
>
>
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Earl Brunner on tue 14 nov 00
The key words that Vince uses here would be "locked in
stable glazes"
I have a glaze formula that calls for 35% Manganese Dioxide
and 15% copper carbonate. It is a wonderful metallic
bronze. Probably deadly as all get out. In all of it's
forms.
On the one hand I might use it in my own studio, on
nonfunctional surfaces, on the other hand I would never put
a bucket of it out in the City lab where I teach, fire, and
mix glazes. Too many people disregard posted and lectured
(and lectured and lectured) cautions.
vince pitelka wrote:
>
> This has come around many times on Clayart, but it is important to mention
> it again whenever anyone asks. Powdered manganese dioxide and chrome oxide
> are not toxic in skin absorption in the raw state, because the particles are
> far too large, and are not soluble. But don't breath the dust, and above
> all do not breath the firing fumes.
>
> Like so many other ceramic materials that are toxic under certain
> circumstances, these seem to be fine if present in reasonable amounts locked
> in a stable glass.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Home - vpitelka@dekalb.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
> http://www.craftcenter.tntech.edu/
>
> ______________________________________________________________________________
> 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.
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
vince pitelka on wed 15 nov 00
> what if i used manganese dioxide mixed with red iron oxide in a stain
which
> i then brushed onto the outside of a teapot? there is no glaze to "lock"
it
> in. should i be concerned about touching this teapot too much? what about
> using it? the tea would touch this outer surface on the spout edge. is it
> dangerous to drink tea that has touched this surface?
> maybe it will be an occasional use only teapot. =(
Audrey -
I do not have an answer, but perhaps some of the glaze gurus will. The iron
will flux to some degree in a high-firing, so there will be some interaction
with the claybody beneath. But I do not know whether this surface will
release manganese in everyday handling. Even if this turns out to be OK, I
would make absolutely sure not to use this manganese-iron stain anywhere
where the tea might touch it.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@dekalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
http://www.craftcenter.tntech.edu/
audrey leung on wed 15 nov 00
vince, thank you for your reply.
i have one followup question though, in response to this statement:
> Like so many other ceramic materials that are toxic under certain
> circumstances, these seem to be fine if present in reasonable amounts locked
> in a stable glass.
> Best wishes -
> - Vince
what if i used manganese dioxide mixed with red iron oxide in a stain which
i then brushed onto the outside of a teapot? there is no glaze to "lock" it
in. should i be concerned about touching this teapot too much? what about
using it? the tea would touch this outer surface on the spout edge. is it
dangerous to drink tea that has touched this surface?
maybe it will be an occasional use only teapot. =(
thanks vince (and any others who have info)
audrey leung
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dan mickey on wed 15 nov 00
thanks vince, i knew you would have further insights into this subject! i am
pleased to hear that mang diox is not toxic in raw state, i was always told
that it was, i guess the people who told me that meant the dust was
dangerous. thanks again
shane mickey
> This has come around many times on Clayart, but it is important to
mention
> it again whenever anyone asks. Powdered manganese dioxide and chrome
oxide
> are not toxic in skin absorption in the raw state, because the particles
are
> far too large, and are not soluble. But don't breath the dust, and above
> all do not breath the firing fumes.
>
> Like so many other ceramic materials that are toxic under certain
> circumstances, these seem to be fine if present in reasonable amounts
locked
> in a stable glass.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Home - vpitelka@dekalb.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
> http://www.craftcenter.tntech.edu/
>
>
______________________________________________________________________________
> 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.
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John Hesselberth on thu 16 nov 00
>> what if i used manganese dioxide mixed with red iron oxide in a stain
>which
>> i then brushed onto the outside of a teapot? there is no glaze to "lock"
>it
>> in. should i be concerned about touching this teapot too much? what about
>> using it? the tea would touch this outer surface on the spout edge. is it
>> dangerous to drink tea that has touched this surface?
>> maybe it will be an occasional use only teapot. =(
Hi Audrey,
There is no way to answer your question without testing the pot the way
you want to make it. As Vince said there will be some interaction with
the clay, but if it still has a metallic look it is probably quite
unstable. Will that work its way into the tea in significant quantities?
Probably not, but who knows?
It is worth repeating what Vince originally pointed out, though. The
primary hazard from manganese is breathing the dust or the fumes. Skin
absorption or ingestion are less of a concern. I certainly agree with
Frank Tucker though that incorporating POWDERED manganese dioxide into a
clay body is pretty dangerous--maybe even just plain stupid. No matter
how good our housekeeping we are all guilty of generating some small
amount of clay dust (and manganese dust with black clay) during our
normal work in our studios. No way would I have one of the black clays
in my studio!
My view on use of powdered manganese dioxide is that it can be safely
incorporated into a glaze if you know what you are doing (both in glaze
formulation and in materials handling). The potter is at far more risk
than the ultimate users because she is handling the powder and/or
breathing the kiln fumes. Uses other than that are an unknown risk. Do
you really want to take it?
Regards, John
John Hesselberth
Frog Pond Pottery
P.O. Box 88
Pocopson, PA 19366 USA
EMail: john@frogpondpottery.com web site: http://www.frogpondpottery.com
"It is, perhaps, still necessary to say that the very best glazes cannot
conceal badly shaped pots..." David Green, Pottery Glazes
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