CD Eating Fungus?

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Wed Jun 20 12:56:41 2001

At 10:39 AM 6/20/01 -0700, Fred wrote:
>In the meantime, this list has been putting a lot of effort into trying to
>come up with ways that what is apparently an urban legend COULD POSSIBLY
>be true. Has anyone tried playing them backwards?

I had thought it was common knowledge, the reflective layer in many CDs is
sputtered aluminum. When exposed to oxygen (as can happen when oxygen
migrates through the plastic or the plastic is cracked) the Aluminum
oxidizes and turns black. It does look a bit like a fungus but only because
it tends to follow the grain pattern in the deposited aluminum.
Aluminum-oxide is black and quite hard actually.

I've seen several examples of this in "real life" and while I have never
seen the process to actually _remove_ Aluminum from the disk it is
conceivable that the Al02 would form a different crystal matrix and thus
change its orientation relative to the original sputtering. That could
leave 'gaps' where the original reflective layer was.

So folks to don't understand chemistry invent the 'fungus' idea and off it
goes into urban legend-dom.

--Chuck
Received on Wed Jun 20 2001 - 12:56:41 BST