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Yesterday, October 17, 2000, I was so bored that I went and microwaved a freebie AOL CD-ROM. So, I put the CD into the microwave, and pressed 'Start'. These weird blue sparks crackled over the CD, and I panicked and turned it off. I took out the CD, and it was cracked. There were big cracks and little cracks in a radial pattern. But, the weird thing was that they were inside the clear plastic part of the CD, so although it looked really cracked, it wasn't possible to feel the cracks at all. However, I was still bored.

I will now go and write, a million times, "I am not a potential candidate for the Darwin Awards" .

First of all, you're lucky you didn't ruin your microwave. Never, ever ever ever ever put anything metallic in a microwave in such a way that it touches the inner walls (floor & ceiling) of the microwave.

Second of all, congrats on the light show. What you did was basically nuke the inner aluminum platter, which wasn't a very bright thing to do, but is very pretty to watch. Each CD is designed to have a Polycarbonate layer underneath an aluminum platter (the junction of the two is what creates the bits which hold the information stored on the CD). On top of this layer is a thin acrylic layer, which anything which is written on the CD face is placed on. Microwaving the CD ruins this middle aluminum level, because, as I'm sure you're now aware, aluminum is an excellent conductor of electricity.

Any metal placed in a microwave is subject to arcing. Whenever you cook something in the microwave, the microwaves bounce all about the walls, and when it hits molecules in the food, it causes them to vibrate, generating heat. However, when metal is placed in this type of a field, the microwaves are disrupted. The air between the walls of the microwave and the metal object become ionized, which serves as a perfect conduit for electricity. This is arcing, and is why you saw the pretty light show. Further exposure to this type of arcing would not just produce a pretty electrical light show, but would be followed up by the distinct aroma of burning plastic, as the heat generated by the arc burns a hole in the inner walls of the microwave

Next time you do this, make sure to have handy a fire extinguisher, and a spare microwave.

For the record, my friends across the hall last year microwaved dozens upon dozens of cds in their microwave.
If you're going to do this, be sure to:
  • Place the cd on a paper plate, both to avoid having the cd actually touch the walls of the microwave, and to collect the little pieces of aluminum
  • Only do it for about 4 seconds... the pretty lights stop after that much time, and the chances you'll fuck up your microwave probably increase as well
  • Don't bother putting more than one cd in at a time... the microwaves get spread out, and each cd is less interesting to look at
Also, don't stand around and breathe in real deeply when you open the microwave door, as there will be a rich aroma from melting plastic in the cd. And as always, don't stand directly in front of a microwave while it's operating, or in 30 years you'll get prostate cancer.

I would like to point out that the distinctive smell which eminates from the microwave, post-light show is not molten plastic, but rather ozone; the CD should not get hot enough to melt, but the substantial arcing is definitely enough to produce some ozone, and you really don't want to breathe that stuff...

There is a far more impressive way to destroy a CD-R disc and possibly a microwave oven, which I have discovered, and, may I add, I am quite glad that my parents have not found out that I discovered it.

It was late one night when a CD-burning session produced a coaster. Out of sheer boredom, I cracked the disc in half. Due to the previous application of a CD Stomper label, this allowed the reflective layer of the CD to be neatly peeled off in one piece!

Never having been the even remotely sane type, I decided to see what would happen if I microwaved the resulting object. I placed it on a ceramic plate and put it in the oven, set the timer to five seconds, and let the poor thing have it.

Here are the results...

0-1.2 seconds: Nothing happened, as the filament in the magnetron tube was still in the process of warming up.
1.3 seconds: Blue flashes first visible on test subject.
1.4 seconds: "WOW, COOL!" ... Observer noted that blue flashes were much more intense and far more visible than those which occur while microwaving a normal CD.
1.5 seconds: Color of light produced changed from blue to orangish-white.
1.6 seconds: Observer says some choice swear words as test subject becomes a fiery torus of plasma!
1.7 seconds: Microwave oven emits really pathetic power-supply buzz. Timer makes equally pathetic "BEeeeeeeeeeeeeeeeeep" noise and goes blank.
1.8 seconds: Test subject bursts into flames. 1.9 seconds: Experiment is terminated, remains of test subject removed from microwave. 9" high flames are gleefully consuming it, producing an AWFUL smell. Flames extinguished using kitchen sink. 45 seconds: Removal of soot from microwave oven commences.

Oh, did I mention that you should NOT try this at home?

The reason that there is a pretty light show when you microwave a compact disc is because of induced surface currents on the metallic layer in the disc. The time-varying electric field excites high-frequency currents in this metal layer, which very quickly heat the metal up to the melting point. At this point you see the wonderful fireworks.

The radial and circumferential burn marks on the disc have to do with the electromagnetic modes that are excited in the microwave, and the resulting electric current distribution on the metal layer.

Consider http://home.c2i.net/metaphor/mvpage.html, where this guy has figured out how to use the microwave energy to melt and cast lots of different metals using a regular microwave oven. Don't try this at home, kids ...

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