David Bash wrote:

Hi Everyone,

In October I left my apartment in Los Angeles for 10 days to do
business outside the country, and for some silly reason closed the
door to my CD room, which is about 10 x 12 and houses about 6,000 CDs.
The CDs are all stored in their jewel cases, most of them upright. The
one window in the room is covered by a dark towel, to ensure that very
little light shines through. While I was gone there were about 5 days
where the outside temperature reached or exceeded 100 degrees
farenheight.

When I returned home and opened the door, it was hot in the room and
it smelled like something had burned (which, apparently, wasn't the
case). I had read that excessive exposure to heat can damage the
aluminum layer, causing holes to appear in the layer, making it
impossible to recover data in those spots. I had also read that CDs
use an interpolation process to compensate for that loss.

Anyway, it seems that every CD I've played that had been in the room
sounds worse than it did before, with most of the noticeable loss
manifesting as muddy, dull midrange and clipped high-end. In other
words, a huge loss of dynamic.

My question is: is this all in my head? Can CD damage due to excessive
heat manifest as a loss of fidelity? Hopefully someone here who has
expertise in these matters can help eliminate my fears.

CD-Rs and CD-RWs are rather heat sensitive, as it is the heat of the
higher power laser that does the recording in the first place. I don't
know the chemistry of the different types well enough to cite a specific
temperature, but that information is probably on the manufacturers
web site.
Pressed plastic CDs are not going to be bothered much by heat
below the level needed to soften and warp the disks. If you have
chemical vapors or lots of UV light present, then the damage that
they are already doing will be accelerated.
Pressed glass CDs are very heat tolerant, and if you really need
to do so, you can have the aluminum removed and replated on
them. Although I'd be surprised if you have them, as they are much
more expensive to make and there is little demand for them.

--Dale