— A spokesperson for EMI, commenting on research done on the permanence of compact discs by the record label Nimbus in 1988. Nimbus, the first CD manufacturer in the UK, said that it had done some research into the disc rot issue and found that most discs will self-destruct after between eight and 10 years. The company's findings, which went against prevailing theories of the time that CDs were indestructible, blamed the problems on improper dyes that reduced the quality of the discs. As highlighted by the quote, record companies were at first skeptical, but Nimbus' concerns about disc integrity turned out to be important and true."I suppose that if you ran a knife over a disc it would not do it any good, and you might destroy it if you stubbed out of cigar on it. But you could pour jam on it without causing any damage."
Why disc rot is a massive challenge for both archivists and collectors
Even though it is only one little dot, it represents damage that cannot be repaired. No scratch removal process can restore the data that is now lost. The game is forever damaged, and likely to get worse over the years.
Now, many sources online will claim that disc rot is a limited-scope problem, concerning only a few years worth of discs from certain manufacturers, (and CD-Rs) and that it is not wide-spread.
But when I learned about this problem, I checked my several hundred discs between Sega CD, Turbo CD, Saturn, and even Dreamcast games and found DOZENS had this problem. Several expensive games I owned were mint—except when held to the light I could see one or more little white dots that proved my game had damage. Some of these I went back to play after not touching for years and found they now would occasionally lock up or not play at all. I had a few FACTORY SEALED games that I opened and found the same thing.
Michele Youket, a preservation specialist at the Library of Congress, often deals with similar situations in her role. She says that this kind of silent destruction, which shows up in three different forms—the "bronzing" of discs, small pin-hole specs located on the discs, or "edge-rot"—became an important one for the national library when the organization started archiving music on CD formats, with the format's weaknesses soon becoming apparent.It has been a nerve-shattering nightmare for a collector like me.
Five notable facts about disc rot, according to the Library of Congress
- Discs with significant errors are often still at least partially readable, according to Youket. "In the case that a disc has an uncorrectable error, depending on where this error occurs much of the data is still recoverable," she explained in an interview. "Many discs with high errors are still playable, and depending on the content—audio, video, or data—even an uncorrectable error may not be serious."
- A scratch at the top of a CD is more problematic than one on the bottom. Why's that? Youket says that the standards for these optical formats include built-in error-correction schemes that can work around scratches in at the bottom of the discs. "However," she says, "because the reflective layer is only covered by a thin coating of acrylic with an ink-printed label, scratches to the top surface can penetrate through and damage the reflective layer."
- DVDs generally have better integrity than do CDs because the disc's reflective layer is pressed inside the polycarbonate discs. But the discs are often more susceptible to breaking apart due to chemical reactions between the layers and the polycarbonate discs—and as a result, layers can delaminate over time. Dual-layer discs tend not to hold up so well.
- Recordable discs don't last as long, in part because of the organic dye used to record the bytes onto discs, which Youket says is vulnerable to degradation—particularly in the case of recordable DVDs, which have higher levels of light sensitivity, making them more susceptible to failure. Additionally, she says the way a recordable disc is burned is a major factor in defining its lifespan—a poorly recorded disc tends to wear out more quickly.
- Proper storage and handling helps. Ultimately, Youket notes that, according to LoC's own aging tests (which determined the life expectancy of discs based on changes in their bit-level error rate), discs are much more likely to survive over long periods if they're handled correctly and stored in good conditions. "These studies have shown that a well-made pressed compact disc can last many decades if stored and handled properly," she noted, adding that "discs that are stored in harsh environmental conditions with elevated temperature and/or humidity will have shorter expected lifetimes than discs stored in more controlled conditions."