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Author Topic: Why Does The Microwave Heat Up My Dry T-Shirt ?  (Read 13788 times)

Offline neilep

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« on: 18/07/2009 13:05:53 »
Dearest Microwaveable-T-shirtologists,

As a sheepy, I of course luff to wear T-shirts.....and now..it seems I like to microwave them too !

Look here,



My T Shirt In the M'Wave A Few Moments Ago
**

I thought Microwaves only heated stuff that had water in it !..so how does my microwave heat up my dry T-shirt ?..Cook for 30 seconds on high and it was nice and warm !


Do the Microwaves do any harm to my T-shirt ? Have I part cooked my T-shirt ?


There's no label saying what it's made from but it is a kind of lavender colour (like as if that really matters !..DOH !)


So, whajafink ?


Hugs & Shmishes


mwah mwah mwah !



Neil
Executive officer In Charge Of Asking This Question
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx






**Polite note: This site does not condone the microwaving of lavender coloured T-shirts !..or any other colour for that matter...or any other type of clothing....or any non food stuffs ! (this include my wifes cooking)


 

Offline SeanB

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #1 on: 18/07/2009 16:18:01 »
Microwaves heat up anything that has molecules that are polar, ie, where the charge distribution is uneven on the molecule. Water is the most common, but many things are able to be heated in a microwave. Easiest that comes to mind in the winter is the overpriced bags of reject Chinese wheat that are sold as warmers, to be used instead of a hot water bottle. They are microwaved for a few minutes until they are hot. These contain no water, especially after being warmed up. You also find ceramic ware that heats up, while others are unaffected. Heating depends on the molecules getting energy added, either from contact with a hotter object, or via being moved by a high power RF energy field. Thus remember that microwaves heat not only water, but almost any thing that is placed inside them, it is just that most of the time the water is a major component of the goods added.

Just remember that they can cause things to catch on fire if heated too long. My sister needed a new microwave after she did this one day, as she would dry dishcloths in the microwave and one day the time was around a minute too much...............

As to the label saying do not microwave, I would point out that a "Reasonable Person" would have read the instruction manual for the microwave, where it says that it is to be used for food only......... ;)

« Last Edit: 18/07/2009 16:20:39 by SeanB »
 

Offline ukmicky

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #2 on: 18/07/2009 19:32:52 »
Quote
I thought Microwaves only heated stuff that had water in it
Ice is made out of water and your microwave will not heat it. ;D

 

Offline neilep

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #3 on: 18/07/2009 19:47:32 »
Microwaves heat up anything that has molecules that are polar, ie, where the charge distribution is uneven on the molecule. Water is the most common, but many things are able to be heated in a microwave. Easiest that comes to mind in the winter is the overpriced bags of reject Chinese wheat that are sold as warmers, to be used instead of a hot water bottle. They are microwaved for a few minutes until they are hot. These contain no water, especially after being warmed up. You also find ceramic ware that heats up, while others are unaffected. Heating depends on the molecules getting energy added, either from contact with a hotter object, or via being moved by a high power RF energy field. Thus remember that microwaves heat not only water, but almost any thing that is placed inside them, it is just that most of the time the water is a major component of the goods added.

Just remember that they can cause things to catch on fire if heated too long. My sister needed a new microwave after she did this one day, as she would dry dishcloths in the microwave and one day the time was around a minute too much...............

As to the label saying do not microwave, I would point out that a "Reasonable Person" would have read the instruction manual for the microwave, where it says that it is to be used for food only......... ;)



This is a fantastic answer for which I am very grateful SeanB.



As soon as you mentioned the ceramics and the wheeat heating thingies ....the penny dropped. Your excellent information just hit it home !

yes.....yes...next time I will condcut an experiment to read the instructions.......

..thing is..I think I might need instructions to tell me to read the instructions !!


THANK YOU SeanB. :)
 

Offline neilep

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #4 on: 18/07/2009 19:48:49 »
Quote
I thought Microwaves only heated stuff that had water in it
Ice is made out of water and your microwave will not heat it. ;D




well....I'm convinced !  ;D
 

Offline Pumblechook

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #5 on: 18/07/2009 19:53:33 »
It is a myth like so many things which get passed around particularly on the Internet.  Microwave ovens work by dielectric heating.

http://en.wikipedia.org/wiki/Dielectric_heating

Materials vary... Polyethene or PTFE will remain cold in a microwave but PVC would melt if left in long enough.
 

Offline neilep

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #6 on: 18/07/2009 20:24:46 »
It is a myth like so many things which get passed around particularly on the Internet.  Microwave ovens work by dielectric heating.

http://en.wikipedia.org/wiki/Dielectric_heating

Materials vary... Polyethene or PTFE will remain cold in a microwave but PVC would melt if left in long enough.

Kewl !! Thanks Pumblechook...with all this info on a  staurday night I am truly spoilt !!
Thanks for the link and information.
 

Offline MonikaS

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #7 on: 18/07/2009 23:46:41 »
yes.....yes...next time I will condcut an experiment to read the instructions.......

Bah! Humbug! Reading instructions is for chickens! Not sheepies!
 

Offline Karen W.

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #8 on: 19/07/2009 10:33:30 »
I have never heated clothing in the microwave but I did heat those aroma therapy gloves and slippers filled with the  seedy stuff for scent and warmth holding properties!
 

Offline Bass

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #9 on: 19/07/2009 17:55:48 »
Have you tried wearing the t-shirt whilst it is in the microwave.  (MMmmmm, I can already smell roast mutton...) ;D
 

Offline neilep

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #10 on: 19/07/2009 18:11:22 »
yes.....yes...next time I will condcut an experiment to read the instructions.......

Bah! Humbug! Reading instructions is for chickens! Not sheepies!

Besides as a sheepy, I of course can't read !...nor type.....erhmmmmm....DOH !!  :D ::)
 

Offline neilep

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #11 on: 19/07/2009 18:13:18 »
I have never heated clothing in the microwave but I did heat those aroma therapy gloves and slippers filled with the  seedy stuff for scent and warmth holding properties!


Did ewe mam ?..all by yourself ?...gosh !!  ;)...slippers and gloves eh ?.....sounds aromatherapytastic !!
 

Offline neilep

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #12 on: 19/07/2009 18:19:12 »
Have you tried wearing the t-shirt whilst it is in the microwave.  (MMmmmm, I can already smell roast mutton...) ;D

Hurrumpth !!







 

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #13 on: 19/07/2009 18:42:47 »
"I love the smell of mint sauce in the morning."
Robert Duval
 

Offline Pumblechook

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #14 on: 19/07/2009 19:11:23 »
I suppose cotton is never completely water free.

Polyester is not a lossy dielectric.
 

Offline MonikaS

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #15 on: 19/07/2009 22:22:59 »
yes.....yes...next time I will condcut an experiment to read the instructions.......

Bah! Humbug! Reading instructions is for chickens! Not sheepies!

Besides as a sheepy, I of course can't read !...nor type.....erhmmmmm....DOH !!  :D ::)

*scratching head* <ponder>
Oh yeah, must be those hooves (or what ever sheepies have on the end of their legs)
 

Offline techmind

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #16 on: 20/07/2009 00:03:29 »
As I wrote on another thread a few days ago, a microwave oven pumps 700watts (or whatever it's rated for) of microwave energy into the enclosure - it has to go somewhere. If there's nothing in the oven that is a more effective absorber, it'll still put heat into poorer absorbers in there.

Energy which doesn't get absorbed in the main cavity will inevitably be dissipated in the magnetron (which generates the microwaves in the first place), and if the oven is operated for too long with too little absorbing material in there then the magnetron is likely to overheat (potentially destructively).
 

Offline Pumblechook

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #17 on: 20/07/2009 21:12:06 »
If you put a low loss material such as polyethylene or PTFE in there it wouldn't absorb much of the Radio Frequency energy very much and might damage the magnetron.   I am not sure what happens to a magnetron with no load. It might actually produce less RF output but still use the same or even more DC power and it will overheat. 
 

Offline Ians Daddy

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #18 on: 09/08/2009 07:08:37 »
I suppose it could also be ambient moisture in the material of the shirt.

Just a thought.
 

lyner

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #19 on: 09/08/2009 22:12:55 »
As I wrote on another thread a few days ago, a microwave oven pumps 700watts (or whatever it's rated for) of microwave energy into the enclosure - it has to go somewhere. If there's nothing in the oven that is a more effective absorber, it'll still put heat into poorer absorbers in there.

Energy which doesn't get absorbed in the main cavity will inevitably be dissipated in the magnetron (which generates the microwaves in the first place), and if the oven is operated for too long with too little absorbing material in there then the magnetron is likely to overheat (potentially destructively).

Actually, it may not actually deliver its rated power unless it is working into an appropriate load. If a transmitter is not 'matched' to its load, it may overvolt (high standing wave ratio, it's called 'in the trade') or you can get excessive currents flowing in the cavities. I think it may not be as much of a problem with modern devices as popular opinion suggests. If it really were such a potential risk, there could always be protective cut-outs installed to save excessive damage.
How many catastrophic failures have we actually heard of? I've not heard of one.
 

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Why Does The Microwave Heat Up My Dry T-Shirt ?
« Reply #19 on: 09/08/2009 22:12:55 »

 

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