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In the 1990s, institutions began transferring all kinds of information - public records, music recordings - over to CDs. Now, there is concern that some of that information could disappear. NPR's Laura Sydell visited the Library of Congress where researchers are learning about the problem.
FENELLA FRANCE: This is actually where we have the materials.
LAURA SYDELL, BYLINE: Fenella France leads the way into a basement lab at the Library of Congress. Researchers here are speeding up the aging process of CDs in what looks like a large wine cooler. As she opens the door, France explains that she can actually control the climate inside this box.
FRANCE: By increasing the relative humidity and temperature, you're increasing the rate of chemical reaction occurring, so we're trying to induce what might potentially happen down the road. That gives us a feel for how long things are going to age.
SYDELL: France is the head of the Preservation, Research and Testing Division at the Library of Congress. She says part of what they're trying to do here is determine what are the minimal conditions for libraries and archives everywhere to preserve CDs?
FRANCE: Small institutions don't have the resources to control environments tightly. One of the things we try to do is sort of look at how wide can that range be, as long as it doesn't fluctuate too much. And it's stable, then that's usually the best thing.
SYDELL: Unfortunately, this testing has also found that not all CDs are the same. This is what CD rot sounds like.
(SOUNDBITE OF ALBUM, "RHAPSODIES BY ERNO DOHNANYI")
SYDELL: And what were we listening to, by the way?
MICHELE YOUKET: OK, right. This one was...
SYDELL: Michele Youket, a preservation specialist here, knows more about what's wrong with this CD than what's on it. Rhapsodies by Erno Dohnanyi. The CD has a variant of disc rot called bronzing. The disc's outer coating erodes, leaving a silver layer exposed.
YOUKET: What happens when you leave silver out? It tarnishes. So it's actually changing the composition. That's why you hear the scratching there.
SYDELL: Here's the thing about CDs - there were a lot of different standards of manufacturing depending on the year, the factory.
YOUKET: This phenomenon of bronzing was particular to only discs that were manufactured at one particular plant in Blackburn, Lancashire, in England.
SYDELL: And only between 1988 and 1993. Youket says part of what makes it hard to preserve CDs is that they are not uniform.
YOUKET: Everyone always wants to know - how long do CDs last? What's the average age? There is no average because there's no average disc.
SYDELL: The Library has some 400,000 CDs in its collections that range from congressional records to popular music. And the Library regularly gets donations of CDs. Beginning in the 1990s, many institutions moved audio archives to CDs - historical societies, museums, symphonies. All over the country, real estate records and titles were moved from microfilm to CD, says Jim Harper, president of the Property Records Industry Association.
JIM HARPER: They just made the move because they thought anything that was digital, anything was electronic was going to be far superior to anything from the past. And it turns out that that was indeed wrong.
SYDELL: Harper says with budgets tight for local governments, most are not going to be able to move to another form of storage in the near future. His organization has been taking Youket out to speak to county officials to at least make certain they understand the problem they're facing.
HARPER: We've been working very hard to dispel that notion. To say, listen, you know, if you're going to use these things, you better be careful what you buy because it's not all created equally.
SYDELL: And increasingly, CDs aren't being created at all. The record shops that sold them are going out of business and new computers don't even come with CD drives. But so many of us still have dozens or hundreds of CDs. Researcher France says, actually, many of them can last for centuries if you take care of them.
FRANCE: The fastest way to destroy those collections - to leave them in their car over summer, which a lot of people do.
SYDELL: Sadly, your favorite CDs - the ones you played a lot - are often the ones that are most likely to be damaged. These days, the Library of Congress is starting to archive material on servers, which France acknowledges could pose an entirely different set of unknown problems in the future. Laura Sydell, NPR News.
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