CDs and DVDs Very Mortal

Lesson: never be an early adopter. I didn’t start accumulating CDs until 1990 and so far mine are holding up fine. Of course, I also store and handle mine properly, not to say anal-retentively, so that probably makes a difference:

Koster, a Web and graphic designer for Queens University of Charlotte, N.C., took one that was skipping pretty badly and held it up to the light.

“I was kind of shocked to see a constellation of pinpricks, little points where the light was coming through the aluminum layer,” he says.

His collection was suffering from “CD rot,” a gradual deterioration of the data-carrying layer. It’s not known for sure how common the blight is, but it’s just one of a number of reasons that optical discs, including DVDs, may be a lot less long-lived than first thought.

“We were all told that CDs were well-nigh indestructible when they were introduced in the mid ’80s,” Koster says. “Companies used that in part to justify the higher price of CDs as well.”

He went through his collection and found that 15 percent to 20 percent of the discs, most of which were produced in the ’80s, were “rotted” to some extent.

The rotting can be due to poor manufacturing, according to Jerry Hartke, who runs Media Sciences Inc., a Marlborough, Mass., laboratory that tests CDs.

The aluminum layer that reflects the light of the player’s laser is separated from the CD label by a thin layer of lacquer. If the manufacturer applied the lacquer improperly, air can penetrate to oxidize the aluminum, eating it up much like iron rusts in air.

But in Hartke’s view, it’s more common that discs are rendered unreadable by poor handling by the owner.

“If people treat these discs rather harshly, or stack them, or allow them to rub against each other, this very fragile protective layer can be disturbed, allowing the atmosphere to interact with that aluminum,” he says.

….Fred Byers, an information technology specialist at the National Institute of Standards and Technology, has looked at writeable CDs on behalf of government agencies, including the Library of Congress (news – web sites), that need to know how long their discs will last.

Manufacturers cite lifespans up to 100 years, but without a standardized test, it’s very hard to evaluate their claims, Byers says. The worst part is that manufacturers frequently change the materials and manufacturing methods without notifying users.

“When you go to a store and buy a DVD-R, and this goes for CD-R as well, you really don’t know what you’re getting,” he says. “If you buy a particular brand of disc, and then get the same disc and brand six months later, it can be very different.”

This renders the frequently heard advice to buy name-brand discs for maximum longevity fairly moot, he says.

DVDs are a bit tougher than CDs in the sense that the data layer (or layers — some discs have two) is sandwiched in the middle of the disc between two layers of plastic. But this structure causes problems of its own, especially in early DVDs. The glue that holds the layers together can lose its grip, making the disc unreadable at least in parts.

….Rewriteable CDs and DVDs, as opposed to write-once discs, should not be used for long-term storage because they contain a heat-sensitive layer that decays much faster than the metal layers of other discs.

For maximum longevity, discs should be stored vertically and only be handled by the edges. Don’t stick labels on them, and in the case of write-once CDs, don’t write on them with anything but soft water-based or alcohol-based markers. [AP]