The NIST (National Institute of Standards and Technology) released a guide "for librarians and archivists" about the care and handling of CDs and DVDs, available here (PDF):

Care and Handling of CDs and DVDs

And a one-page summary.

The guide contains extensive information about the structure of the discs, how to store them (curious fact, you shouldn't store them horizontally), life expectancy, effects of humidity, light, notes about marking, labels... a good read.

Looks like I know what I'm doing for the next hour or so...

Less than 68f, brrrrr, will not be possible around here but for about 3 months of the year, and even then I could not stand it.

Thank you for the link.

It in turn links to another interesting document. A Compact Disc introduction, that covers in depht the Compact Disc technology. It is quite recent (07 / 2003 ).

http://www.disctronics.co.uk/downloads/tec...ntroduction.pdf

The moral of the shorter story:
Store CD's Vertically,
avoid temperatures below 4C/39F and above 20C/68F (we all need to switch to Kelvin),
avoid relative humidity levels below 20% (???!???!!) and above 50%,
avoid direct sunlight or UV lamps

The third recommendation I do not fully understand.
Why should there be a minimum relative humidity?
There cannot be much water in the polycarbonate lattice or the laquer top coating to begin with, so losing water to the dry air should not be an issue (for their integrity).

The full version mentions such obvious precautions as not exposing a CD to benzene or acetone.
The question then arises, what about diethyl ether and tetrachloroethylene?

Definitely the definitive guide to CD handling. The NIST is a very valuable organization and has been so for a very long time.

edit:
The document PIO2001 has linked to is also quite interesting, but in a somewhat different way. There is a good short section on CD copy protection for instance, and a fine explanation of frames and subcode channels.

added clarification

Maybe it is meant to keep additional components from vaporizing out of the dye or polycarbonate ... if the water's partial pressure in the air (which is relative humidity) falls beneath a certain value, it could be possible that some kind of agent (maybe some kind of polycarbonate flexibilizer or agent to maintain it's amorph structure for translucence) can vaporize into the air more easy and leave an embritteled or "milky" polycarbonate. I don't have the opportunity to test this myself so up to this point this is pure speculation.

It could also be possible that this is just a pure precaution ...

Why is it bad to store CDs horizontally?

I'd better get rid of my horizontal CD racks then!

Still, by "a long time" they could mean 5 years or 50 years. In 50 years, I doubt I'll care.

Cheers,
David.

In all seriousness a CD is rather light so I doubt the CD will droop while rested in a horizontal postion while it is in the case. If it does I think that will happen over and VERY LONG period of time. Another point I should make is that you should worry more about the damaging effects of the environment rather than this, as those elements would decay so to speak the CD faster than leaving it in a horizontal position.

Regards

AgentMil

yes, but it's easier to change its position than the environment it's also easier to argue about that