CD Rot

An article by the Associated Press describes how CDs deteriorate. CDs are made of plastic and a thin layer of aluminum. It's the aluminum that is stampted with the data (a.k.a "music"). The top (or label) side of the CD is covered by a thin layer of laquer. It turns out that the label side is more delicate than the bottom (or read) side.

If the top gets scratched, oxygen in the air interacts with the aluminum, causing the aluminum to oxidize, forming pinholes. (Having grown up in "The Aluminum City" of Kitimat BC, I know aluminum metal does not "rust" because it oxidizes so quickly. Unfinished aluminum has a dull finish, because of the layer of oxidation.)

One of my children's CDs does not work, because she wrote hard on the label with a ballpoint pen. This tore through the laquer and the aluminum, creating a see-through CD -- ie, one that doesn't work.

DVDs are tougher, with a layer of plastic top and bottom. But, the article notes, the glue holding the two plastic halves together can sometimes fail. Bending DVDs may cause them to fail sooner.

The claim of manufacturers that CD and DVD discs last 100 years cannot be verified independently, due to the constant change in manufacturing processes. CD-R and DVD-R (recordable) discs are thought to have a shorter lifespan, because their heat sensitive layer decays faster than aluminum. Keep them out of hot areas, and keep them from physical damage. (This is starting to remind me of "Diskette Handling Tips"!)

You can read the entire article here.

One solution is to make multiple backups. After converting all my LP records and music CDs to MP3 format, I have the master MP3 collection on a 120GB external hard drive, and a backup copy on DVDs (which hold about 80 standard CDs of music, each) stored offsite.

Comments

[Darren Young]

A good document of CD/DVD archiving recommendations can be found here...

http://www.itl.nist.gov/div895/carefordisc/CDandDVDCareandHandlingGuide.pdf

[Darren Young]

I see the link got cut off. You should be able to access the information from this one...

http://www.itl.nist.gov/div895/carefordisc/