Crazing

Hi Xtra News, all very interesting. I think the items you unearthed
tend to direct us towards sensible caution and precautions but for the
sake of 'the public at large' those who sell their wares for use with
food must be even more cautious. Enough said, I hope.
Andy

On Fri, 25 Nov 2005 14:30:35 +1300, "Xtra News"
wrote:

Well I decided to do a bit more looking into this,

Well, I'm not sure what exactly you looked into. Only one of the
links you posted directly relates to food safety and crazing. The
others relate to food safety and leaching of toxic materials and/or
potter exposure to toxic materials. As I said before and I'll say
again, crazing and leaching are two separate issues. You can have a
glaze that crazes that doesn't leach significant amounts of toxic
materials and a glaze that leaches that doesn't craze. Or you can
have a glaze that does both or neither.

The question that was asked and the question that I answered related
to crazing. Both the issue of crazing and the issue of leaching /
material toxicity are important, but it is not helpful to jumble up
the two.

deg

"plodder" wrote in message
ups.com...
Hi Xtra News, all very interesting. I think the items you unearthed
tend to direct us towards sensible caution and precautions but for the
sake of 'the public at large' those who sell their wares for use with
food must be even more cautious. Enough said, I hope.
Andy


Yeah, probably. Been away apologies for not getting back sooner. I saw the
Portage Ceramic awards in Auckland while away, only briefly we were running
out of time. Its inspiring to see good work though.
I am sure that I have seen it online for previous years. This one won't be
online yet because it is still open but here is an article about it and one
persons work.
http://www.thebigidea.co.nz/article....&mode=&order=0

"Dewitt" wrote in message
...
On Fri, 25 Nov 2005 14:30:35 +1300, "Xtra News"
wrote:

Well I decided to do a bit more looking into this,

Well, I'm not sure what exactly you looked into. Only one of the
links you posted directly relates to food safety and crazing. The
others relate to food safety and leaching of toxic materials and/or
potter exposure to toxic materials. As I said before and I'll say
again, crazing and leaching are two separate issues. You can have a
glaze that crazes that doesn't leach significant amounts of toxic
materials and a glaze that leaches that doesn't craze. Or you can
have a glaze that does both or neither.

The question that was asked and the question that I answered related
to crazing. Both the issue of crazing and the issue of leaching /
material toxicity are important, but it is not helpful to jumble up
the two.

deg

Well it is a complex issue, but as mentioned before if you have underglaze
decoration and a crazed glaze over I believe that it could be a hazard for
food safety. I think it is an issue that we all need to keep vigilant about
because it is important, both unsafe glazes, or crazed glazes, esp over
underglaze decoration.

Lets bring up the barium and manganese dioxide issues for food safety
again... these sites here say that Manganese dioxide is poisonous on the
macro gram level.... as in over a thousand grams!!!! Are you going to
absorb hundreds of grams of Manganese dioxide from your glazed cup?
Hundreds, tens? More than likely you would have trouble measuring the
amount of manganese dioxide leached from a glaze. The same is true of
barium. Its poisonous on the macro gram level. I hate this. Its
irresponsible not to read the fricking articles about these substances
and then start this hysterical nonsense about food safety again. Barium
is not lead. Lead is very dangerous. It is poisonous on a microgram
level and leaches substantially from a glaze. Lead should not be used in
our studios. I would be more concerned about the effects of smoking
tobacco in a studio than any of the chemicals that we use. The effects
upon the potter of absorbing copper through our skin; the effects of
dust and fiber from kaowool on our lungs... Food safety from crazing is
really low on a list of what to worry about....
Russell Andavall

Xtra News wrote:

"Dewitt" wrote in message
.. .


On 22 Nov 2005 13:16:59 -0800, "plodder"
wrote:



I would like to pose
some questions about the hygene aspect of crazing. Why does industry
consider crazing a defect? Isn't any surface that is more difficult to
thoroughly clean a minor health hazard?


The primary reasons that industry considers crazing a defect are that
a piece with a crazed glaze is substantially weaker than a piece with
a glaze that "fits" properly and crazing is generally considered a
visual defect. Personally, I doubt that crazing presents a
significant hygiene issue and have never seen any research to indicate
it does, but eating off crazed and stained dinnerware is certainly
unappealing.

deg



Well I decided to do a bit more looking into this, I will not cut and paste
anybody, perish the though ) been there, but I will post some sites, OK
This one is fairly interesting
http://ceramic-materials.com/cermat/education/271.html
and this one by the same person
http://ceramic-materials.com/cermat/education/144.html

Run out of time, there were lots more sites. These two are not bad.
It is something I feel strongly about that I think many potters do not seem
as concerned as they should be IMO. Food safety with glazes is an issue.
Talking of the past and how human kind survived is one thing, but we know
that lots of people died of lead poisoning and today I trust that people are
not using unsafe lead glazes.
Take a look at these
http://www.lenntech.com/Periodic-cha...ents/Cu-en.htm

http://www.jtbaker.com/msds/englishhtml/m0715.htm

These are just two glaze ingredients, one usually thought of as unsafe, the
other as more safe, but you will see that we should take these things
seriously. This is of course particularly important for us as potters, and
I trust everyone wears masks and wet wipes to clean up etc etc.

On Tue, 29 Nov 2005 07:24:29 GMT, Russell Andavall
wrote:

Lets bring up the barium and manganese dioxide issues for food safety
again... these sites here say that Manganese dioxide is poisonous on the
macro gram level.... as in over a thousand grams!!!!

This primary concern with manganese is not leaching, but the exposure
to manganese fumes by the potter during the firing process. Over
time, exposure can result in Parkinson's disease like symptoms. For
more info see http://ceramic-materials.com/cermat/education/155.html
and http://www.ceramicstoday.com/articles/080999.htm

And while the dangers of barium may not be as extreme as some believe,
it is something that potters need to be aware of. Again, the danger
is problem the greatest for potters who don't know how to handle it
properly, though the leaching issue should not be dismissed. More
info at:
http://ceramic-materials.com/cermat/education/162.html

deg