The Natural Philosopher wrote
Rod Speed wrote
The Natural Philosopher wrote
MM wrote
Andy Dingley wrote
Adam Funk wrote

On a related note, is there a good & easy way to destroy data CDs? CDs or CD-ROMs?

If they're CD-ROMs, you can microwave them. You need to space them
apart if you're doing a batch (plastic toastrack, or else a $500
silicon wafer processing boat). You also need to do them for just
long enough to nuke the data layer, but without cooking the
plastic or there's a fume problem. For regular industrial use I
was able to use a cheap domestic microwave from Currys, but had
to mod it with a fixed timer and a single big push button.

CDs can't be nuked to reliably kill the data without getting them hot enough to cause a fume problem. Shredding is
easier, although you do need a hefty shredder.

I do not understand this penchant for microwaving CDs! Toxic, extremely obnoxious fumes will be released.

Absolute bull****.

Yes.

You simply dont understand: you are rapidly heating the conductive
metallisation which arcs and splits apart without even getting the plastic hot.

It uses the properties of the microwave to put heat into conductors,

No, in fact they just bounce off those. Thats why alfoil on the
ends of say chicken chicken drumsticks stops the ends burning.

Microwaves (to heat) need to get absorbed by something.

Yes, but the destruction of CDs when done right isnt done by heat.

They 'bounce off' thick metal film because they do get absorbed,

They bounce off thick metal film even when there is nothing to absorb them, like
when microwave is empty and you only have the thick metal walls etc there.

and that sets up currents that effectively cancel the EMF at that point this reflecting them back with if you like a
counteracting EMF generated by the foil.

That utterly mangles what actually happens.

Microwaves bounce around inside the microwave oven.

They dont get absorbed by the ends of the chicken drumsticks
that you have covered in foil just because they cant get thru the
foil and so whats under the foil doesnt get heated, and so doesnt
burn. You still get conduction of the heat thru the bone from the
part of the drumstick that isnt covered in foil and so is heated by
the microwaves.

BUT that current itself does heat the foil a bit

Nope.

and if the foil is thin enough...

The reason you get a spectacular light show is the very thin foil getting
vaporised by the currents that flow in the foil because its an antenna.

Nothing to do with heat.

Its a bit like saying you want see a voltage drop across a straight
piece of metal - well you wont until you have a larger enough current
and a small enough piece of metal and then you have a fuse.

Cut thats current, not heat.

CD metallization is thin enough to not withstand the currents needed to reflect the microwaves without fusing - that's
all.

Yes, and its not heat, its currents.