Posted on 08/26/2014 9:52:12 AM PDT by a fool in paradise
Many institutions have their archives stored on CDs — but the discs aren't as stable as once thought. There is no average life span for a CD, says preservationist Michele Youket, "because there is no average disc."
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Back in the 1990s, historical societies, museums and symphonies across the country began transferring all kinds of information onto what was thought to be a very durable medium: the compact disc.
Now, preservationists are worried that a lot of key information stored on CDs — from sound recordings to public records — is going to disappear. Some of those little silver discs are degrading, and researchers at the Library of Congress are trying to figure out why.
In a basement lab at the library, Fenella France opens up the door to what looks like a large wine cooler. Instead, it's filled with CDs. France, head of the Preservation, Research and Testing Division here, says the box is a place where, using temperature controls, a CD's aging process can be sped up.
"By increasing the relative humidity and temperature, you're increasing the rate of chemical reaction occurring," she says. "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 [take to] age."
France says part of what they are trying to do here is determine the minimal conditions needed for libraries and archives everywhere to preserve CDs.
"Smaller institutions don't have the resources to control environments tightly," she says. "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 [if] it's stable, then that's usually the best thing."
Unfortunately, this testing has also found that not all CDs are the same. Michele Youket, a Library of Congress preservation specialist, plays a CD of classical piano rhapsodies by Erno Dohnanyi. It crackles, and eventually the sound just cuts out.
This is a variant of what's called "CD rot," Youket explains. In this case. it's what's called "bronzing." The outer coating of the CD erodes, leaving a silver layer exposed. And when you leave silver exposed, it tarnishes.
"So it's actually changing the composition, and that's why you hear the scratching there," Youket says.
And here's the thing about CDs: Youket says part of what makes it hard to preserve CDs is that they are not uniform. There were a lot of different standards of manufacturing, depending on the year and the factory.
"This phenomenon of bronzing was particular to only discs that were manufactured at one particular plant in Blackburn, Lancashire, in England," and only between 1988 and 1993, Youket explains.
"Everyone always wants to know the answer to the same question, 'How long do CDs last? What's the average age?' " Youket says. But "there is no average, because there is no average disc."
The Library of Congress has around 400,000 CDs in its collections, ranging from congressional records to popular music, and the library regularly gets donations of CDs.
Real estate records and titles were also moved from microfilm to CD beginning in the 1990s all around the country, says Jim Harper, president of the Property Records Industry Association.
"They just made the move because they thought anything that was digital, anything that was electronic, was going to be far superior to anything from the past," Harper says. "And it turns out that that was indeed wrong."
With budgets tight for local governments, Harper says most are not going to be able to move to another form of storage in the near future.
PRIA has been taking Youket out to speak to county officials, to at least make certain they understand the problem they're facing.
"We've been working very hard to ... say, 'Listen, if you're going to use these things, you better be careful what you buy, because it's not all created equally,' " Harper says.
Increasingly, CDs aren't being created at all. The record shops that sold them are going out of business, and new computers don't come with CD drives any more. Even so, many of us still have dozens or hundreds of CDs. All Tech Considered Museums Give Video Games Bonus Life, But The Next Level Awaits
Researcher France says many of them can actually last for centuries if they're taken care of. "The fastest way to destroy those collections is to leave them in their car over summer," she says — "which a lot of people do."
Sadly, your favorite CDs — the ones you've 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 still-unknown problems in the future.
Which makes CDs like every single other medium you can store information on.
Funny, my LPs are fine.
And - they sound much much better than CDs.
For years in my EE classes, I demonstrated CD vs LP on a very high end system, with audio levels precisely matched using sources that had LP and CD matches. The students were not told which was which - only that they were listening to either source A or source B.
When asked to vote, the LP never ever lost.
And - of course - some students felt that I was trying to fool them.
Oh, the EE class was in digital signal processing....so yes, I know the subject.
With CDs losing data in the 5-20 year lifespan, that makes them terrible as an “archival data” system.
They certainly were not advertised that way.
The very early CD’s had a problem with self destruct because of some of the ingredients reacting over time.
I’m pretty sure they will last longer than you can find a reader for them.
I guess that depends on how often you play them. When I was young I played certain records and cassettes so much they wore out and/or lost sound qualilty pretty fast. For that type scenario, CD's are a pretty good medium. If you are just going to store them in a drawer, then not so much.
Digital guys depend on the Nyquist theorem for reproduction fidelity, but they ignore the quantization errors. I think that that is where the media comes up short.
Voyager carries its message on a gold plated copper disk. Wonder what will remain of the message if it’s ever recovered. Might be misconstrued and start an interstellar war.
“With CDs losing data in the 5-20 year lifespan, that makes them terrible as an “archival data” system.”
I still have a lot of CD’s from the 1980’s. All playing fine.
I use mine mostly for storing pictures & data. How will they fare in that usage? Are flashdrives better?
Lois Lerner should have said that her emails are all stored on a cd . . . which degraded.
CD lifespan loss isn’t from overplay, it’s from oxidation.
Periodic backups is a time consuming and costly process. Then there is the whole “verification” of the dupe. And the storage...
Scratched records will still play. Dirty records will still play.
90 years later even.
Playing them more or playing them less isn’t the issue, since the information of the layer on the disc is read through the polycarbonate substrate. What is at issue is the reflective layer comprised of aluminum will oxidize if exposed to air, which is why the top of the disc is sealed with an acrylic layer (in the early days we used solvent based lacquering materials and then switched to UV based material for both environmental and cost issues). So depending on how what type of environment the disc is exposed to over it’s lifetime (humidity and temperature) it could last for decades.
3M (later Imation) was offering a product that guaranteed 100 years for archival purposes that was more expensive than other CD-ROMs at the time.
In any event, with the cheap cost of external/portable hard drives today it would be silly for anyone to NOT backup their CD’s on those drives and then burn copies if their original discs ever deteriorated beyond playability.
I took DSP at the USCG from an amazing teacher by the name of Hartnett. He did the same thing to demonstrate that zero insertion and digital filtering wasn’t all it was cracked up to be.
He went out and bought up huge collections of albums predicting:
1. Morons would throw treasure out the window to make way for the CD.
2. CDs would eventually be exposed for what they were, and that not everything that should be preserved on CDs, would be.
He also warned that changing media was a convenient way for a civilization to forget all kinds of important recorded history, and that governments would one day use it as a tool.
That was my point. If you want something you can play over and over for a couple of years with no loss of sound quality, CD is a good medium. If you want something that will last a much longer time and you aren't concerned about sound degredation then other mediums are better. It all depends what you are looking for. All mediums have their plusses and minuses.
All true, but for the average consumer the CD is a more sensible buy, because he is not willing to take the special care needed to protect an LP from contact with the needle [cleaning the LP, proper balance, proper cartridge damping, and so on.] And most turntables that casual consumers of music are willing to pay for would not afford sufficient protection even if he took the time and care required.
We don’t need spinning discs anymore. That is 1990s technology at best.
If you take a 1 hour video clip (mp4, avi, mpg, etc) at roughly 250mb and put it to DVD so it will play on a DVD player, it suddenly takes 4GB. Same with an album’s worth of digital audio files (even in higher audio formats than mp3).
The equipment manufacturers (which also happen to own major labels) don’t want to see the market give up the “discs”.
They don’t think people would pay $200 for a chip or “cartridge” with all of the Beatles albums on it.
Plus if you scratch a disc, it can’t be resold on the used market and you may even buy the same album you already purchased.
dvdisaster http://dvdisaster.net/en/index.html
I tested this free software by writing a full data DVD and then making a 25% backup data file.
I then took the DVD to the workbench and drilled several holes into it.
The software was able to fully recover an image of the DVD.
For important data I recommend two copies of the original data disk stored in different locations and two copies of the recovery data also stored in different locations.
Protecting your important data is not easy, cheap or fun.
But losing that data is even less fun :-(
Large hard drives are getting really cheap so it is a good idea to always buy two identical drives and store the same data on both. It is very unlikely that both drives will ever fail at the same time (Unless you work at the IRS)
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