"We're trying to predict, in terms of collections, which of the types of CDs are the discs most at risk," France said. "The problem is, different manufacturers have different formulations so it's quite complex in trying to figure out what exactly is happening because they've changed the formulation along the way and it's proprietary information."

Even CDs made by the same company in the same year and wrapped in identical packaging might have totally different lifespans. That's what Library of Congress researchers found when they tested twin copies of Paul Winter's Grammy-nominated 1987 album Earthbeat.

The two seemingly identical discs were exposed to extreme heat and humidity in an accelerated-aging machine. They cooked for about 500 hours at 175 degrees and in relative humidity of 70 percent—about what you'd expect on a sweltering July day in New York City, but not quite as humid as a rain forest. One of the CDs emerged relatively unscathed. The other was zapped of its musical data, completely destroyed by oxidation. You can see the ruined CD, which became almost totally transparent, on the right:

Library of Congress

"They started out looking exactly the same," France said. "I wish we could definitively say, you know, 'If you have a CD that was manufactured in 1984, that's terrible.' But it's not quite that simple."

If you're willing to part with your old CDs, the library will happily destroy them for you. "In the name of science!" France says. "And just so people know that no library materials are harmed." (Update: A spokeswoman with the Library of Congress asked me to let people know that the center now has a "sufficient supply of CDs for its research and testing.")

The Center for the Library's Analytical Science Samples is a laboratory for destruction, a place where researchers can practice "destructive testing" on non-library materials as a way to learn how best to care for actual library collections. Staffers at the center might opt for more destructive aging tests, like the treatment that Earthbeat suffered, or just let discs age naturally and check in on them every decade or so.

There are all kinds of forces that accelerate CD aging in real time. Eventually, many discs show signs of edge rot, which happens as oxygen seeps through a disc's layers. Some CDs begin a deterioration process called bronzing, which is corrosion that worsens with exposure to various pollutants. The lasers in devices used to burn or even play a CD can also affect its longevity.

Then there's the wear and tear that's more in line with what you'd probably expect to happen over time—like scratches and exposure to extreme temperatures. ("If you want to really kill your discs, just leave them in your car over the summer. That's a really great way to destroy them," France says.)

But it turns out that plenty of people don't know how to care for CDs properly in the first place. For instance, the best way to hold a CD is to pinch the hole in the middle, and the top surface of the CD—the side that faces up when it's playing—is more delicate than the bottom. Again, France: "People are generally more concerned about the scratches on the bottom, but actually you can get quite a lot more damage when you get scratches on the top layer because it goes through and impacts the metal reflective layer. So quite often you find people are really careful not to put their hands underneath, but holding it in the middle is better."