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

BUT that current itself does heat the foil a bit and if the foil is thin
enough...


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.

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


--
To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
that they know how little is really possible -
and how hard it is to achieve it.