CDs DVDs Weaker than Thought

[Guest guest]

How To Care For

CDs And DVDs

By Peter Svensson

6-9-4

 

(AP) -- Dan Koster was unpacking some of his more than 2,000 CDs

after a move when he noticed something strange. Some of the discs,

which he always took good care of, wouldn't play properly.

 

Koster, a Web and graphic designer for Queens University of

Charlotte, N.C., took one that was skipping pretty badly and held it

up to the light.

 

"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.

 

"We were all told that CDs were well-nigh indestructible when they

were introduced in the mid-'80s," Koster says. "Companies used that

in part to justify the higher price of CDs as well."

 

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.

 

Koster has taken to copying his CDs on his computer to extend the

life of the recordings. Unfortunately, it's not easy to figure out

how long those recordable CDs will work.

 

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.

 

"When you go to a store and buy a DVD-R, and this goes for CD-R as

well, you really don't know what you're getting," he says. "If you

buy a particular brand of disc, and then get the same disc and brand

six months later, it can be very different."

 

This renders the frequently heard advice to buy name-brand discs for

maximum longevity fairly moot, he says.

 

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.

Koster's friend Mark Irons, of Corvallis, Ore., stored his CD

collection in a cabin heated by a wood-burning stove. The

temperature would range between 40 degrees and 70 degrees in the

space of a few hours. Now, the data layer of some of his CDs looks

as if it's being eaten from the outside.

 

Irons is still pretty happy with CD technology, since it beats vinyl

LPs and tape for longevity. Now that he's moved his discs to an

apartment with a more stable temperature, he's noticed that the

decay has slowed.

 

"I'm hoping they'll hold out till that next medium gets popular, and

everyone gets to buy everything over again," he says.

 

How to care for CDs and DVDs

 

Some handling tips for CDs and DVDs, including the recordable

versions, from the National Institute of Standards and Technology.

 

Do:

 

1. Handle discs by the outer edge or the center hole. Your

fingerprints may be acidic enough to damage the disc.

 

2. Use a felt-tip permanent marker to mark the label side of a CD.

The marker should be water-based or alcohol-based. In general, these

will be labeled "nontoxic." Stronger solvents may eat through the

thin protective layer to the data.

 

3. Keep discs clean. Wipe with cotton fabric in a straight line from

the center of the disc toward the outer edge. If you wipe in a

circle, any scratches may follow the tracks of the CD, rendering

them unreadable. Use CD/DVD-cleaning detergent, isopropyl alcohol or

methanol to remove stubborn dirt.

 

4. Return discs to their plastic cases immediately after use.

 

5. Store discs upright (book style) in their cases.

 

6. Store discs in a cool, dry, dark place with clean air.

 

7. Open a recordable disc package only when you are ready to record.

 

8. Check the disc surface before recording.

 

Do not:

 

1. Touch the surface of the disc.

 

2. Bend the disc. This may cause the layers to separate.

 

3. Use adhesive labels, since they can warp the disc or unbalance

it.

 

4. Expose discs to extreme heat or high humidity. Don't leave them

in sun-warmed cars, for instance.

 

5. Expose discs to extremely rapid temperature or humidity changes.

 

6. Expose recordable discs to prolonged sunlight or other sources of

ultraviolet light.

 

For CDs especially do not:

 

1. Scratch the label side of the disc. It's more sensitive than the

transparent side.

 

2. Use a pen, pencil, or fine-tip marker to write on the disc.

 

3. Try to peel off or reposition a label. Again, you risk

unbalancing the disc.

 

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