When CDs first came out, they were marketed as being nearly indestructible. We were told we’d be able to throw them around like Frisbees, run over them with cars, and beat on them with a baseball bat and they’d still play perfectly. Obviously, that turned out to be a bit less than truthful, and most people know to take at least some level of care for their CDs and DVDs. Still, now that they’ve been around for a while, people are noticing the problem of “CD rot” where, for no clear reason, the data layer of the disc just starts to go bad.

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, 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.

More here.