Wendy Hampton on sat 11 oct 97
I put a mug full of water I got from a potter in my microwave the other day
and after about 2 1/2 minutes I smelled something burning. I opened the oven
and the glaze on the rim of the mug was black and bubbling. The entire mug
had crazed - not small spider crazes but large black lines. The only thing
different I did from the last time I put this mug in the microwave was that
the water was sitting in the mug overnight.
Can anyone explain what happened and what could be done to prevent this
occurance?
Thanks
Wendy from Bainbridge Island WA
Talbott on sun 12 oct 97
Wendy...
That is one for the book!... Was the mug coated in sugar or what?
Or perhaps a pastry shaped like a mug?. Any mug or "functional" pottery of
any description, should contain glaze components that will not melt until
they reach at least cone 6..1230 C or 2245 F. Perhaps your microwave is a
nuclear reactor in disguise... I would take the mug back to the "potter"
and demand a cash refund... ...Marshall
>----------------------------Original message----------------------------
>I put a mug full of water I got from a potter in my microwave the other day
>and after about 2 1/2 minutes I smelled something burning. I opened the oven
>and the glaze on the rim of the mug was black and bubbling. The entire mug
>had crazed - not small spider crazes but large black lines. The only thing
>different I did from the last time I put this mug in the microwave was that
>the water was sitting in the mug overnight.
>Can anyone explain what happened and what could be done to prevent this
>occurance?
>Thanks
>Wendy from Bainbridge Island WA
1ST ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1997)
http://fmc.utm.edu/~dmcbeth/cag/naples.htm
2nd ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
Details will be forth coming!!!
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
http://webchat12.wbs.net/webchat3.so?Room=PRIVATE_Clayarters
---------------------------------------------------------------------
Ed Pierce on sun 12 oct 97
Wendy,
A microwave oven works because the frequency of the microwave radiation
excites certain resonances of the water molecule. So, any non-conducting
(non-metallic) material that contains moisture will be heated. Your dry cup
did not have enough moisture in its walls to be noticeably heated by the
microwave energy, whereas the soaked cup did. The boiling off of a
combination of liquid intentionally held within a cup and any absorbed cup
surface water would normally keep a cup that does contain some wall
moisture from getting too hot. In the case of the soaked cup, and in
particular it's rim, the microwave energy absorbed by the moisture within
the cup's body could not be removed fast enough by the boiling off of the
cup's held and surface water. As a result the cup over heats.
Because of its speed and efficiency, conveyer-type microwave ovens are
currently being used commercially for bisque "firings".
There is a parallel here to the problem of bisque firing damp clay too
fast. I would not recommend using a microwave oven to dry out soaked
ceramics. It could be dangerous!
Ed
>----------------------------Original message----------------------------
>I put a mug full of water I got from a potter in my microwave the other day
>and after about 2 1/2 minutes I smelled something burning. I opened the oven
>and the glaze on the rim of the mug was black and bubbling. The entire mug
>had crazed - not small spider crazes but large black lines. The only thing
>different I did from the last time I put this mug in the microwave was that
>the water was sitting in the mug overnight.
>Can anyone explain what happened and what could be done to prevent this
>occurance?
>Thanks
>Wendy from Bainbridge Island WA
Talbott on mon 13 oct 97
Any functional mug worth its weight in sand should not absorb water. That
is one reason that the surface has a vitreous glaze. I also don't think
any such mug which Wendy described would be considered to be food safe.
....Marshall
>----------------------------Original message----------------------------
>Wendy,
>
>A microwave oven works because the frequency of the microwave radiation
>excites certain resonances of the water molecule. So, any non-conducting
>(non-metallic) material that contains moisture will be heated. Your dry cup
>did not have enough moisture in its walls to be noticeably heated by the
>microwave energy, whereas the soaked cup did. The boiling off of a
>combination of liquid intentionally held within a cup and any absorbed cup
>surface water would normally keep a cup that does contain some wall
>moisture from getting too hot. In the case of the soaked cup, and in
>particular it's rim, the microwave energy absorbed by the moisture within
>the cup's body could not be removed fast enough by the boiling off of the
>cup's held and surface water. As a result the cup over heats.
>
>Because of its speed and efficiency, conveyer-type microwave ovens are
>currently being used commercially for bisque "firings".
>
>There is a parallel here to the problem of bisque firing damp clay too
>fast. I would not recommend using a microwave oven to dry out soaked
>ceramics. It could be dangerous!
>
>Ed
1ST ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1997)
http://fmc.utm.edu/~dmcbeth/cag/naples.htm
2nd ANNUAL CLAYARTERS' GALLERY - NAPLES, MAINE (Summer 1998)
Details will be forth coming!!!
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
http://webchat12.wbs.net/webchat3.so?Room=PRIVATE_Clayarters
---------------------------------------------------------------------
Jasper Stil on tue 14 oct 97
------------------
On Sun, 12 Oct 1997 09:44:48 EDT, you wrote:
=3E
=3EThere is a parallel here to the problem of bisque firing damp clay too
=3Efast. I would not recommend using a microwave oven to dry out soaked
=3Eceramics. It could be dangerous=21
=3E
=3EEd
=3E
At a seminar last september near Amsterdam, Peter Lane and Arne Ase
turned their pots and put them directly in a microwave oven to dry for
the continuing of the demonstration of their technics.
Just what I've witnessed.
M. Claire
Carol Jackaway on tue 14 oct 97
Wendy,
I have heard of mugs getting small "spider" crazing but never bubbling.
The microwave should never be able to "burn" the glaze (which is what you
described). You mentioned you had used the mug before, could something have
been on the rim?
I think you should hold on to the mug and so it off as a ceramic
oddity!!
Carol Jackaway
CoilLady
Parkside Pa.
cloudy and I am sneezing .....alot!!:(
Roxanne Hunnicutt on tue 21 oct 97
I would think the glaze was crazed and water was boiling on the SURFACE of the
glaze. You say the glaze boiled? And blackened? Wow!
Tell us your findings!
Rox in OR with clear lovely warm-enough-for-no-sweater days and evenings too.
Talbott wrote:
> ----------------------------Original message----------------------------
> Wendy...
> That is one for the book!... Was the mug coated in sugar or what?
> Or perhaps a pastry shaped like a mug?. Any mug or "functional" pottery of
> any description, should contain glaze components that will not melt until
> they reach at least cone 6..1230 C or 2245 F. Perhaps your microwave is a
> nuclear reactor in disguise... I would take the mug back to the "potter"
> and demand a cash refund... ...Marshall
>
> >----------------------------Original message----------------------------
> >I put a mug full of water I got from a potter in my microwave the other day
> >and after about 2 1/2 minutes I smelled something burning. I opened the oven
> >and the glaze on the rim of the mug was black and bubbling. The entire mug
> >had crazed - not small spider crazes but large black lines. The only thing
> >different I did from the last time I put this mug in the microwave was that
> >the water was sitting in the mug overnight.
> >Can anyone explain what happened and what could be done to prevent this
> >occurance?
> >Thanks
> >Wendy from Bainbridge Island WA
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