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Author Topic: Kitchen Foil....which way and why ?  (Read 12084 times)

Offline tweener

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Re: Kitchen Foil....which way and why ?
« Reply #25 on: 21/04/2004 03:30:47 »
I've zapped many CDs in microwaves - it's FUN!

They do arc and spark, but that is what is so fun.  If you have seen any really cheap sci-fi movies where the ship gets hit with the energy weapon and little sparks and tracers go all over the outside, that is about what happens with a CD.  The sparks are confined to near the surface of the CD and don't go to the walls of the oven.

I recommend filling a cup with some water (to absorb some energy), then set the CD on top of the cup so you can see it.  Set the oven for about 10 seconds and watch the show.  When the sparking stops, I stop the oven, but with the water in there, it doesn't really matter.  Sometimes the show is very short ( < 1 second) and sometimes it lasts several seconds.

For obvious reasons, I don't recommend this with a CD that has data you value.  They come out with a very "crackled" look to the metal.

And every microwave oven I've done this with continued to work after the "experiment".  So far.

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John - The Eternal Pessimist.
 

Offline MayoFlyFarmer

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Re: Kitchen Foil....which way and why ?
« Reply #26 on: 21/04/2004 06:55:42 »
I had a friend in college who used to save the clear discs that come on the ends of spools of blank CDs.  He'd then nuke a real CD to create the cool cracking pattern, and then glue the clear one on top of it and use them as costers, they were awesome!

Lift your skinny fists, like antennas to hevan!
 

Offline NakedScientist

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Re: Kitchen Foil....which way and why ?
« Reply #27 on: 21/04/2004 09:07:30 »
I made an interesting observation the other day.

When a plate with a gold band edging (and food in the middle) was placed in the microwave it produced a spectacular light show of sparks and arcs.

But when the aluminium dish from a Chinese takeaway (containing some food that was for re-heating - probably unwise) was placed in the microwave it could be heated without problems.

Why should this be ?
 

Offline gsmollin

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Re: Kitchen Foil....which way and why ?
« Reply #28 on: 22/04/2004 04:16:44 »
Doh! Don't put gold plated china in a microwave. Don't put metalic treated paper party plates in a microwave either. And you guys with the CDs are on your own.  Sure, it's fun, but then someone loses an eye.

Depending on the shape of the conductor, it can be in a microwave and not cause a spark. Some of the foil dishes have rounded edges, so the electic field termination is not so abrupt that the potential exceeds breakdown. I can never predict which will spark, or not, though. And I'm pretty sure it helps to have the foil dish full of food.
 

Offline NakedScientist

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Re: Kitchen Foil....which way and why ?
« Reply #29 on: 22/04/2004 06:01:36 »
hmm, but the plate gold banding also has rounded edges. Also, I've tried several foil dishes from various takeaways without triggering any fireworks, but the foil-lined packet that you get with your peshawari naan almost takes the microwave with it if you put one of those on cook !

In the immortal words of Ali G "How do you h'explain that ?"

TNS
 

Offline Donnah

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Re: Kitchen Foil....which way and why ?
« Reply #30 on: 22/04/2004 21:40:16 »
quote:
Originally posted by gsmollin

Doh!...Sure, it's fun, but then someone loses an eye.

Yeah, and we all know that after that they call it a sport.
 

Offline neilep

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Re: Kitchen Foil....which way and why ?
« Reply #31 on: 22/04/2004 21:55:23 »
So...do I do the deed and micowave a cd or not ?...to cd or not cd ? that is the question !! I am prepared to sacrifice a cd, cos I have about three hundred  stuck to my study wall (freebee ones).....

'Men are the same as women...just inside out !'
 

Offline gsmollin

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Re: Kitchen Foil....which way and why ?
« Reply #32 on: 23/04/2004 03:01:44 »
quote:
Originally posted by NakedScientist

hmm, but the plate gold banding also has rounded edges. Also, I've tried several foil dishes from various takeaways without triggering any fireworks, but the foil-lined packet that you get with your peshawari naan almost takes the microwave with it if you put one of those on cook !

In the immortal words of Ali G "How do you h'explain that ?"

TNS



You're not thinking three-dimensionally. The china cup is alumina, an excellent dielectric, and invisible to microwaves. So the microwaves see a round gold band, about three inches in diameter, a quarter inch high, and no more than 20 microinches thick. That's a lot thinner than aluminum foil, and a very sharp edge, indeed!
 

Offline tweener

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Re: Kitchen Foil....which way and why ?
« Reply #33 on: 23/04/2004 20:41:37 »
You're right gsmollin.  In addition to the sharp edge, it it also a loop, approximately one wavelength in diameter.  This makes a very efficient antenna, which will make for a very high current induced around the loop.  Once the loop breaks, most likely in several places, the current doesn't flow any longer.  When the metallic pieces are small enough, they just become little scatterers that don't really affect the overall resonance in the microwave.

And, you're right, there is no way to predict what is going to arc and what is going to peacefully co-exist in the oven.

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Re: Kitchen Foil....which way and why ?
« Reply #33 on: 23/04/2004 20:41:37 »

 

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