Dan Koster was unpacking some of his more than 2,000 CDs after a move when he noticed something strange. Some of the discs, which he always took good care of, wouldn't play properly.
Koster, a Web and graphic designer for Queens University of Charlotte, North Carolina, 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.
"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.
Part of the problem is that most people believe that it's the clear underside of the CD that is fragile, when in fact it's the side with the label. Scratches on the underside have to be fairly deep to cause skipping, while scratches on the top can easily penetrate to the aluminum layer. Even the pressure of a pen on the label side can dent the aluminum, rendering the CD unreadable.
"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.
Users that bend a DVD to remove it from a hard-gripping case are practically begging for this problem, because flexing the disc puts strain on the glue.
http://www.cnn.com/2004/TECH/ptech/05/0 ... index.html"I'm hoping they'll hold out till that next medium gets popular, and everyone gets to buy everything over again," he says.
