Ann Brink on wed 24 aug 05
I've heard that the fats get extremely hot quickly, and I bet that the area
under the melted butter started to expand from heat and the edges of the
bowl were still cool, setting up stress. Just my opinion.
Ann Brink in Lompoc CA
----- Original Message -----
From: "Paul B"
To:
Sent: Wednesday, August 24, 2005 6:04 PM
Subject: POT EXPLODED IN MICROWAVE!
> My mom put some butter in a bowl i gave here and put it in a microwave to
> melt it for about a minute and it exploded! The bowl had a glaze with 10%
> RIO lining the inside and part of the outside. I know you are not supposed
> to put metal in microwaves and i wonder if that was the cause? I don't see
> how the body could be at fault since it has been used with so many baking
> items.
> Anyone out there have an opinion?
> thanks,
> Paul
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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Daniel Semler on wed 24 aug 05
Hi Paul,
I'm wondering if the bowl was fully vitrified or not ? If not and it had
absorbed a bunch of water then maybe that was the cause. By 'explode' do you
mean that it literally exploded in a large number of small fragments, or that
it broke into a few bigger pieces ? If larger pieces are available you could
still test the absorption.
There are so many experiments that come to mind to test here. Of course you'd
want to be prepared to lose a microwave or two, eg. does the pot get hot when
in the microwave alone and heated, would having a plastic cup with some water
in microwave with it have helped, would an unglazed version of the pot made in
the same way have reacted this way ? Butter can get very hot, perhaps severe
thermal gradient is the real culprit, which is why a description of the
'explosion' would really help. I think there was a post like this concerning
some sort of sugar being heated like this a while back.
Thanx
D
L. P. Skeen on wed 24 aug 05
Paul, we'd need to know more about the pot itself; RIO in the glaze matrix
isn't going to be bothered in the microwave. If I had to guess, and I do,
since you didn't provide any information about the pot, I'd say that your
bowl wasn't water tight, that the clay absorbed some water, which was then
overheated by the microwave to the boiling point, and then just as will
happen when you put wet ware in a kiln and jack it up to bisque fire, the
steam built up inside the pot and pot went boom boom.
My two cents, but you'll have to do the adjustment for inflation yourself,
as I don't do math.
----- Original Message -----
From: "Paul B"
> My mom put some butter in a bowl i gave here and put it in a microwave to
> melt it for about a minute and it exploded!
Patrick Green on wed 24 aug 05
I suppose the iron could have done it, but that
wouldn't be the first place i looked. you said she
baked in it often? perhaps the abunance of use made a
few hairline cracks. If the pot was glazed and the
boby still had some softness to it it could have soak
in some water from washing or use, then when put into
the microwave (since a microwave heats by exciting
water molecules, unlike baking which just increase the
temp via flame or conduction) It could have done so
inside the clay body and thus POP. Kinda like fast
bisquing a wet pot. I suppose it is possible even if
the body was to temp,(vitrafied{i know i misspelled
that}) that some water might have been able to get
between cracks in the glaze or in the body and have a
similar effect. was it a glossing glaze or matte? (i
know both can have crazing but i find it happens
easier in a gloss glaze)
do you have a similar pot to test if perhaps it was
the Iron, by repeating the incedent?
ANyway thats my thoughts on it. But I am just
beginning at the moment so take it for what its worth
:) Good luck with this mystery
--Pat
--- Paul B wrote:
> My mom put some butter in a bowl i gave here and put
> it in a microwave to
> melt it for about a minute and it exploded! The bowl
> had a glaze with 10%
> RIO lining the inside and part of the outside. I
> know you are not supposed
> to put metal in microwaves and i wonder if that was
> the cause? I don't see
> how the body could be at fault since it has been
> used with so many baking
> items.
> Anyone out there have an opinion?
> thanks,
> Paul
>
>
______________________________________________________________________________
> 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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terry sullivan on wed 24 aug 05
Paul,
We had quite a discussion on this a while back on clayart.
I don't know what your clay was or what the firing temp was so here is
my expirience:
Earthen ware pots do absorb water through the unglazed parts.Even if
this is just the bottom rim. This seems to be excellerated if the piece
is washed in a dishwasher which uses high temp steam in the cycle.
My first expirience with this was an earthenware mug from Cost Plus.
Each morning I would put the mug in the microwave with water and a tea
bag for my morning tea.
What I found was that the handle was to hot to touch but the water was
still only warm.
I theroized that the cup/mug had absorbed water from the bottom unglazed
rim in the dishwasher and that water was heating up the clay from the
inside out. To test this theory; I took a new mug and put it in the
microwave. No heating of the mug. Then I took one that had been through
the dishwasher cycle several times and put it in the microwave.
Low and behold, it was scorchingly hot to touch.
So the superheated steam from the dishwasher cycle was infusing the
earthenware with water which was heating up in the microwave even though
there was nothing in the mug.
I had a different expirience with a craftshow bought stoneware mug a few
years before. I made my tea every morning with water and a tea bag in
the microwave. One day the mug just dissintigrated into little pieces.
I think this may have been due to two processes: one that the
stoneware was not as vitrified as it should have been and was absorbing
water from the dishwasher, but also from the heating of the iron in the
clay body by the microwaves on a dayley basis.
So we have two, or more, things happening here. One is that a clay body
can absorbe water which will be heated to steam by microwaves and cause
heating of the pot. The other is that iron is also heated by microwaves
and might cause structural failure.
One thing is for sure: steam is a very powerfull force. It can cause
explosions and transfer heat very fast. Faster than it can escape via
pours in an earthenware piece. That means explosion or at least super
heating of the clay body.
My two cents,
Terry Sullivan
Nottingham Center for the Arts
WWW.nottinghamarts.org
pdp1@EARTHLINK.NET on wed 24 aug 05
Hi Paul,
If the Claybody of the Bowl had even a slight degree of absorbancy in
unglazed areas, and had retained Water in it's minute interior interstices
from it's occasins of washing...
The Water, in turning readily to steam, might cause it to 'explode'.
Phil
Las Vegas
----- Original Message -----
From: "Paul B"
> My mom put some butter in a bowl i gave here and put it in a microwave to
> melt it for about a minute and it exploded!
<<>>
> Anyone out there have an opinion?
> thanks,
> Paul
Paul B on wed 24 aug 05
My mom put some butter in a bowl i gave here and put it in a microwave to
melt it for about a minute and it exploded! The bowl had a glaze with 10%
RIO lining the inside and part of the outside. I know you are not supposed
to put metal in microwaves and i wonder if that was the cause? I don't see
how the body could be at fault since it has been used with so many baking
items.
Anyone out there have an opinion?
thanks,
Paul
Bob Santerre on thu 25 aug 05
I microwave my Tenmoku glazed dinnerware (cone 10 stoneware) all the
time. Never explodes! Your bowl probably had adsorbed some water and
the steam production caused the explosion. Test the water adsorption of
your fired clay body. If it's greater than 2% your body is not being
fired to maturity.
Bob
///////////////////////////////////////////////////////////////////////////////////////////////////////////////
Paul B wrote:
>My mom put some butter in a bowl i gave here and put it in a microwave to
>melt it for about a minute and it exploded! The bowl had a glaze with 10%
>RIO lining the inside and part of the outside. I know you are not supposed
>to put metal in microwaves and i wonder if that was the cause? I don't see
>how the body could be at fault since it has been used with so many baking
>items.
>Anyone out there have an opinion?
>thanks,
>Paul
>
>______________________________________________________________________________
>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.
>
>
>
>
>
Brant Palley NMCLAY.com on thu 25 aug 05
Red iron oxide does cause the surface of the pot to get very hot, but, i
suspect it was water in the clay turning to steam that caused the bomb.
Check the absorption of the clay body.
Brant Palley
www.nmclay.com
John Hesselberth on thu 25 aug 05
On Aug 24, 2005, at 9:04 PM, Paul B wrote:
> My mom put some butter in a bowl i gave here and put it in a microwave
> to
> melt it for about a minute and it exploded! The bowl had a glaze with
> 10%
> RIO lining the inside and part of the outside. I know you are not
> supposed
> to put metal in microwaves and i wonder if that was the cause? I don't
> see
> how the body could be at fault since it has been used with so many
> baking
> items.
> Anyone out there have an opinion?
> thanks,
> Paul
Hi Paul,
Your pot 'exploded' because the clay was not vitrified and had absorbed
enough water through dishwashing or whatever to cause the problem. Iron
in a glaze does not cause this problem. I and others have tested up to
15% iron oxide in a glaze on a well vitrified body and not seen any
unusual heating in a microwave.
If you will check the absorption of your fired clay body you will
probably find that it is above 3%. A body like this can survive oven
heating because it is much slower than microwave heating. You need to
fire that body to a higher cone or get a body that will vitrify at
whatever cone you are firing to. You don't say where you are firing,
but if you are working with earthenware you need to switch to stoneware
to keep it from happening.
Regards,
John
John Hesselberth
http://www.frogpondpottery.com
http://www.masteringglazes.com
Jennifer Boyer on thu 25 aug 05
I can confirm that my stoneware pottery has had trouble with this kind
of cooking (fatty foods only partially covering the surface of a pot)
even in a normal oven.
They haven't exploded, just cracked. One was a plate that had nachos on
it(bits of cheese randomly hitting the pot, and one was a pie plate in
which there was an oval meatloaf which only partially covered the
bottom.....I'm sure this butter problem was a case of thermal shock,
not a glaze problem. Was it earthenware? There is also a problem with
earthenware retaining water and breaking from steam expansion. Butter
would have made a very quick temp rise in a damp pot.
Jennifer
On Aug 24, 2005, at 9:48 PM, Ann Brink wrote:
> I've heard that the fats get extremely hot quickly, and I bet that the
> area
> under the melted butter started to expand from heat and the edges of
> the
> bowl were still cool, setting up stress. Just my opinion.
>
> Ann Brink in Lompoc CA
>
>
> ----- Original Message -----
> From: "Paul B"
> To:
> Sent: Wednesday, August 24, 2005 6:04 PM
> Subject: POT EXPLODED IN MICROWAVE!
>
>
>> My mom put some butter in a bowl i gave here and put it in a
>> microwave to
>> melt it for about a minute and it exploded! The bowl had a glaze with
>> 10%
>> RIO lining the inside and part of the outside. I know you are not
>> supposed
>> to put metal in microwaves and i wonder if that was the cause? I
>> don't see
>> how the body could be at fault since it has been used with so many
>> baking
>> items.
>> Anyone out there have an opinion?
>> thanks,
>> Paul
>>
>>
> _______________________________________________________________________
> _____
> __
>> 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.
>
> _______________________________________________________________________
> _______
> 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.
>
>
************************
Jennifer Boyer
Thistle Hill Pottery
Montpelier, VT
http://thistlehillpottery.com
Snail Scott on thu 25 aug 05
At 09:04 PM 8/24/2005 -0400, you wrote:
>My mom put some butter in a bowl i gave here and put it in a microwave to
>melt it for about a minute and it exploded! The bowl had a glaze with 10%
>RIO lining the inside and part of the outside. I know you are not supposed
>to put metal in microwaves and i wonder if that was the cause? I don't see
>how the body could be at fault since it has been used with so many baking
>items.
If there were enough metal in a glaze to be
conductive, you might see sparks and eventually
ruin the machine. (This can happen with metallic
luster overglazes, for instance.) The pot won't
explode, though. And I seriously doubt that a
10% iron glaze could be a factor.
If the pot exploded, that's probably because there
was moisture trapped in the clay, underneath the
glaze. This is mainly a problem with earthenware,
but porous underfired stoneware could do it,
too. It isn't a big issue with baking dishes because
the heat increase is gradual, and the moisture has
time to escape or dry out. With a microwave,
though, the moisture is heated directly and very
quickly, resulting in steam explosions that can
destroy the pot.
I suspect your clay has some porosity, and a means
for moisture to enter, either through a dry foot or
through crazing. Handwashing can reduce the
likelihood if it's rinsed and dried, and not left to
soak in the sink. Dishwashing can force the moisture
deeper into the clay than handwashing due to the
prolonged contact with hot steamy water - far more
than most hand dishwashing, even if you do it 'by
the book' like Wayne! ;)
-Snail
Paul B on thu 25 aug 05
Thanks for the replies on this one.
Just to clarify things a bit, it was a stoneware body fired somewhere
between cones 9-10. I believe the pot was made a couple years ago when i
was just starting to mix my own clay and it is quite possible that the
absorption on some of my early formulas was not exactly 2%, but as i recall
when i tested some of the earlier ones i found them to be closer to being
overfired rather than under, with absorption less than 1% on at least one
occasion.
It does however sound like the piece that exploded had absorbed moisture
into the body so maybe the pot was in a cool part of the kiln and
underfired; but i wonder if what really did it in was the combination of
localized heat from the butter and moisture in the body?
At least i can rule out the idea that it was the iron in the glaze.
thanks again,
Paul
Ron Roy on fri 26 aug 05
Hi Paul,
Perhaps it would help if you describe what you mean by "exploded."
Sometimes that could mean it simply cracked - but other times it would mean
- into many small pieces - and anything in between.
I might help if you would send me the recipe of the glaze - just to check
and see if the glaze is a low expander - ronroy@ca.inter.net
I don't keep copies of the glazes I work on by the way - if you lose a
revision from me - it's gone.
I got a call a few weeks ago - from a person who had ordered a dinnerware
set - to help determine what the cause was. Some dinner plates had cracked.
I know the clay body and the calculated expansion of the glaze was in a
normal range - so that was not the problem.
It turns out the plates were being warmed in a microwave oven that had a
dish warmer feature. They actually did an experiment on a third plate and
it cracked.
Has anyone else had any experience with this?
RR
>Thanks for the replies on this one.
>Just to clarify things a bit, it was a stoneware body fired somewhere
>between cones 9-10. I believe the pot was made a couple years ago when i
>was just starting to mix my own clay and it is quite possible that the
>absorption on some of my early formulas was not exactly 2%, but as i recall
>when i tested some of the earlier ones i found them to be closer to being
>overfired rather than under, with absorption less than 1% on at least one
>occasion.
>It does however sound like the piece that exploded had absorbed moisture
>into the body so maybe the pot was in a cool part of the kiln and
>underfired; but i wonder if what really did it in was the combination of
>localized heat from the butter and moisture in the body?
>At least i can rule out the idea that it was the iron in the glaze.
>thanks again,
>Paul
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Linda Blossom on mon 29 aug 05
Ron said:
It turns out the plates were being warmed in a microwave oven that had a
dish warmer feature. They actually did an experiment on a third plate and
it cracked.
Hi Ron,
What do you mean by a dish warmer feature? I am wondering if this is
something like the plates made for microwaves that help to brown the food?
Linda
Ithaca, NY
Ron Roy on tue 30 aug 05
Hi Linda,
I have never seen it but he said it was a feature of his microwave. One of
the workers at the shop - where the dinner set was sold - said she has a
microwave oven with that same feature and was going to test some ware -
they have not told me how that worked out.
I would like to hear from anyone who has an oven with a plate warmer
feature. I would be interesting to all dinnerware makers if it is a risk
for studio made dinnerware.
I'm sure it is not the browning plates - but rather a built in feature.
RR
>Ron said:
>It turns out the plates were being warmed in a microwave oven that had a
>dish warmer feature. They actually did an experiment on a third plate and
>it cracked.
>
>
>Hi Ron,
>
>What do you mean by a dish warmer feature? I am wondering if this is
>something like the plates made for microwaves that help to brown the food?
>
>Linda
>Ithaca, NY
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Wayne Seidl on tue 30 aug 05
Ron:
Our microwave has a built in convection oven and a broiler element
integral to the design. One appliance, three functions; we have it
mounted over the stove. Made by Panasonic, though Sharp now makes
one too. One of the "features" of our oven is that one can program
partial cooking in both convection and microwave, so that you get
quick food that tastes "right". You can warm plates with the
convection cycle, if you are so inclined, but your oven can do that
too, or even a toaster oven.
If they stuck that pot in under those circumstances, I'm not
surprised it blew. Especially with oil or butter in it, or even
cheese.
Hey, it's not diamond, it's ceramic! There are limits to the
material and the stress it can endure...but of course no one wants
to hear that.
Best,
Wayne Seidl
(I wonder if diamonds would explode if heated? Hmmm...)
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Ron Roy
Sent: Tuesday, August 30, 2005 1:10 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: POT EXPLODED IN MICROWAVE!
Hi Linda,
I have never seen it but he said it was a feature of his microwave.
One of
the workers at the shop - where the dinner set was sold - said she
has a
microwave oven with that same feature and was going to test some
ware -
they have not told me how that worked out.
I would like to hear from anyone who has an oven with a plate warmer
feature. I would be interesting to all dinnerware makers if it is a
risk
for studio made dinnerware.
I'm sure it is not the browning plates - but rather a built in
feature.
RR
Daniel Semler on tue 30 aug 05
Hi Ron,
Did a bit of snooping on this one. Check out this link below for a plate
warming system for microwaves. It uses a pad in between each plate in a stack.
The microwave heats the pad, the pad heats the plate. Note that it does not
cover the rim, in the example shown.
There seem to be several variations on this theme out there. Is this
the sort of
thing that they are using ?
Thanx
D
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