Re: Bulk erase methods

In article <no.spam-546368.10085114072005@xxxxxxxxxxxxxxxx>,
no.spam@xxxxxxxxxx says...
> In article <pan.2005.07.13.22.18.03.757605@xxxxxxxxxxx>,
> Rich Grise <richgrise@xxxxxxxxxxx> wrote:
>
> > On Wed, 13 Jul 2005 16:57:58 +0000, Guy Macon wrote:
> >
> > >
> > >
> > >
> > > Naveed wrote:
> > >>
> > >>"Guy Macon" <_see.web.page_@xxxxxxxxxxxxxxxxxx> wrote...
> > >>>
> > >>> Barry Lennox wrote:
> > >>> >
> > >>> >On 11 Jul 2005 15:45:50 -0700, bigcat@xxxxxxxxxxx wrote:
> > >>> >
> > >>> >>What methods can be used to bulk erase a lot of floppies? I dont have
> > >>> >>one of those nice big electromagnets, and was wondering if anything
> > >>> >>else to hand could be used. I presume 2 seconds in a microwave with a
> > >>> >>load to prevent sparking is too risky, though I should try one.
> > >>> >>
> > >>> >>Cant think of anything else that causes a strong enough mag field...
> > >>> >>any ideas?
> > >>> >
> > >>> >Old magnetron magnets will do the job very nicely.
> > >>>
> > >>> Magnets do indeed destroy data, but if that's all he wants to do
> > >>> a bonfire is even better. If he wants to re-use the floppies he
> > >>> would be better off with something that creates an alternating
> > >>> magnetic field.
> > >>
> > >>If the magnet was attached to a drill running at low speed then that would
> > >>cause an alternating magnetic field.
> > >
> > > Excellent point.
> > >
> > > Which brings up the question, what is the optimal frequency?
> > > With an electromagnet you get 50/60 Hz unless you go to a lot
> > > of effort to get another frequency - and it works well - but
> > > with a motor/magnet it's easy to pick a frequency.
> >
> > The frequency is irrelevant. The point is to have a strong enough
> > magnetic field to line up all of the little magnetic thingies in
> > the media, and then turn them all around on the next half-cycle.
> >
> > A permanent magnet will line up all the little thingies, but then
> > you've got a magnet bias that could introduce confounding factors
> > when re-using the media.
> >
> > Anyway, with the AC field (hey, there's a usage of AC that we
> > didn't consider in the "Tastes Great-Less Filling" ACDC thing!),
> > just twirl the magnet fast enough that it can sweep the field
> > over the media once or twice.
> >
> > Then, the secret is, slowly move the moving magnet ( or half
> > a transformer, or whatever) away from the media, and as the
> > alternating field gets weaker and weaker, reversing fewer
> > and fewer thingies, until on the average, there's no
> > residual magnetism in the media.
> >
> > It's the same principle with CRT degaussers, but they use
> > a PTC thermistor in series with the coil. Press the degausser
> > button on your monitor - see the pretty patterns? And how
> > they decay? That's the principle that ends up with
> > negligible residual magnetization. I know there's a whole
> > nother jargon here, but, come on! :-)
> >
> > Anyway, Hope This Helps!
> >
> > Cheers!
> > Rich
> >
> >
>
> Years ago, bulk magnetic tape erasers were sold for erasing reel-to-reel
> magnetic tapes. You might be able to find one in an antiques store ;-)
> and use it for your purpose.

Digital media, floppys in particular, have a much higher coercivity
than reel-to-reek audio tape, so don't expect the "bulk eraser" to work
very well. A shredder is a far better method. If the floppys are to
be reused, formatting them will deter all but the black-hats.

--
Keith
.