Researchers Abuse Discs

Surprise! Some brands of DVD-R, DVD+R, DVD-RW, and DVD+RW discs may be unreadable in less than ten years.

“We found that some media are capable of lasting several tens of years, though we don’t know what several tens of years actually is, but certainly longer than five or ten years,” explains Oliver Slattery, a researcher with the Digital Media Group at NIST (National Institute of Standards and Technology). “Other discs would probably be dead in under ten years. Our results tell both stories.”

How are consumers supposed to know which discs will last for decades and which ones won’t? To resolve this potentially sticky situation, a coalition of disc manufacturers announced on July 2 that they had agreed to a standard set of stress tests for recordable and rewritable DVD discs. Based on the test results, they could rate a disc’s longevity and provide a label that certifies an approximate life expectancy. Like an expiration date on a carton of milk, the label could indicate the effective lifespan for a particular brand of discs.

Since we don’t want to wait 50 years to determine whether a disc will really last 50 years, researchers use accelerated conditions to extrapolate longer periods of time. In short, they severely abuse the discs to find out how they’ll hold up under ordinary conditions. The discs are subjected to extremes of heat and humidity you wouldn’t wish on your worst enemy.

The challenge is to maximize the environmental stress — but not to a point where you alter the physical properties of the disc. Apply too much heat, and the disc begins to melt. Approach the boiling temperature of water, and the moisture inside the disc reacts in an uncharacteristic manner.

It’s a delicate balance. “If you do the temperature or humidity too quickly, you’ll start causing condensation,” says Slattery. “If a drop of water falls on the media, that could lead to a different effect than you’re trying to monitor.”

“There’s also the stability of keeping the equipment going at certain temperatures,” says Fred Byers, a researcher with the Digital Media Group at NIST. The test chambers are often quite large. “Some companies have walk-in chambers, where you walk in and set things on shelves,” he explains.

A full test procedure could take six months to two years to complete and require hundreds of discs for each brand tested. So next time you buy a recordable DVD disc and wonder how long it might last, consider the discs that are stuck in the lab and the abuse they endure, all for the sake of progress.