#1  
  12-29-2009, 11:42 AM
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i read this article on the web and thought it would be of interest to members here. here are relevant points drom the article:

"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.

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.

But in Hartke's view, it's more common that discs are rendered unreadable by poor handling by the owner.

"If people treat these discs rather harshly, or stack them, or allow them to rub against each other, this very fragile protective layer can be disturbed, allowing the atmosphere to interact with that aluminum," he says.

Part of the problem is that most people believe that it's the clear underside of the CD that is fragile, when in fact it's the side with the label. Scratches on the underside have to be fairly deep to cause skipping, while scratches on the top can easily penetrate to the aluminum layer. Even the pressure of a pen on the label side can dent the aluminum, rendering the CD unreadable.

Fred Byers, an information technology specialist at the National Institute of Standards and Technology, has looked at writeable CDs on behalf of government agencies, including the Library of Congress, that need to know how long their discs will last.

Manufacturers cite lifespans up to 100 years, but without a standardized test, it's very hard to evaluate their claims, Byers says. The worst part is that manufacturers frequently change the materials and manufacturing methods without notifying users.

DVDs are a bit tougher than CDs in the sense that the data layer (or layers -- some discs have two) is sandwiched in the middle of the disc between two layers of plastic. But this structure causes problems of its own, especially in early DVDs. The glue that holds the layers together can lose its grip, making the disc unreadable at least in parts.

Users that bend a DVD to remove it from a hard-gripping case are practically begging for this problem, because flexing the disc puts strain on the glue.

Rewriteable CDs and DVDs, as opposed to write-once discs, should not be used for long-term storage because they contain a heat-sensitive layer that decays much faster than the metal layers of other discs.

For maximum longevity, discs should be stored vertically and only be handled by the edges. Don't stick labels on them, and in the case of write-once CDs, don't write on them with anything but soft water-based or alcohol-based markers.

Also, like wine, discs should be stored in a cool, dry place.
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  #2  
  12-29-2009, 11:42 AM
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Do:
1. Handle discs by the outer edge or the center hole.
2. use a non-solvent-based felt-tip permanent marker to mark the label side of the disc.
3. Keep dirt or other foreign matter from the disc.
4. Store discs upright (book style) in plastic cases specified for CDs and DVDs.
5. Return discs to storage cases immediately after use.
6. Leave discs in their packaging (or cases) to minimize the effects of environmental changes.
7. Open a recordable disc package only when you are ready to record data on that disc.
8. Store discs in a cool, dry, dark environment in which the air is clean.
9. Remove dirt, foreign material, fingerprints, smudges, and liquids by wiping with a clean cotton fabric in a straight line from the center of the disc toward the outer edge.
10. Use CD/DVD-cleaning detergent, isopropyl alcohol, or methanol to remove stubborn dirt or material.
11. Check the disc surface before recording.

Do Not:
1. Touch the surface of the disc.
2. Bend the disc.
3. Use adhesive labels.
4. Store discs horizontally for a long time (years).
5. Open a recordable optical disc package if you are not ready to record.
6. Expose discs to extreme heat or high humidity.
7. Expose discs to extremely rapid temperature or humidity changes.
8. Expose recordable discs to prolonged sunlight or other sources of ultraviolet light.
9. Write or mark in the data area of the disc (the area the laser "reads").
10. Clean by wiping in a direction going around the disc.

For CDs especially do not
1. Scratch the label side of the disc.
2. Use a pen, pencil, or fine-tip marker to write on the disc.
3. Write on the disc with markers that contain solvents.
4. Try to peel off or reposition a label.
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  #3  
  12-29-2009, 11:44 AM
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i'm not up to date with the cd/dvd technology.
have things improved since the 80s?

do we need to back up all the cds/dvds to hard drives?
but then, hard drives only last about 5 years or so (according to some manufacturers).

so, what is the best thing to do about all our cds/dvds?
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