CDs and DVDs Are Not Forever

Many of us labor under the mistaken notion that once we have burned files or images to a CD or DVD, they will exist on that media forever. Nothing could be further from the truth.

While CDs and DVDs are fine for file storage in the short term, you need to realize that they do indeed have a shelf life, and that shelf life is much shorter than you would assume. Depending on the substrate used to manufacture the discs, you could expect two to five years of readability, which could impact retrieval of your files.

“But I thought my files would always be safe on a CD/DVD!” you might be saying, mentally reviewing all the family photos, important files, and that unfinished novel you’ve got stored away in a desk drawer somewhere. Don’t panic yet, but understand that all CDs and DVDs are not created equal.

As with any product manufactured today, there are varying grades of quality in optical media. While the process for manufacturing CD/DVDs is the same, the materials that go into this process can vary widely, and it is these materials that affect the quality of the finished product.

How CDs and DVDs Are Made

The basic process for the manufacture of optical media is similar for both CDs and DVDs. Each is made with a polycarbonate plastic substrate containing a shallow spiral groove extending from the inside to the outside diameter of the disc. Added to this substrate is an organic dye recording layer (azo, cyanine, dipyrromethene or others) followed by a metal reflective layer (aluminum, silver, silver alloy, gold). These layers are sealed with a protective lacquer overcoat.

cd storage

How CDs and DVDs Work

Writing information to a CD or DVD is a process that uses heat to alter the dye layer into a series of bumps, which are read by a laser in a CD/DVD drive. The metal reflective layer behind the dye enables the laser to read the data contained in the bumps, and this is where problems can occur with the retrieval of data. Depending on the type of metal used in the reflective layer, the material can degrade over time, especially if exposed to extremes in temperature and humidity.

All CDs and DVDs Are Not Created Equal

Recordable and rewritable CDs and DVDs, because of the different types of metal used in the reflective layer, have differing life expectancies. The bulk of discount store discs utilize aluminum in their reflective layers, and the shelf life of these can be as short as two years. Aluminum has a tendency to oxidize when exposed to environmental factors, and though the disc is protected by a lacquer coating, this coating is not impenetrable. Higher quality CDs and DVDs are made with a 24K gold reflective layer, providing a significant upgrade in the quality and shelf life of the disc. Because pure gold does not oxidize when exposed to environmental factors, it maintains its reflective qualities for a longer period of time. Higher-quality gold discs, however, are considerably more costly than standard aluminum layered discs found at discount stores.

What Should I Do About Storing My Files, Then?

The best practice for long-term storage comes down to this: have a storage migration plan in place. Burning your data to a CD or DVD and then storing it with assumption it will be recoverable forever is short-sighted at best. If your files and photos are important enough to warrant being copied to a disc, then you must commit yourself to using the highest-quality discs available. Store your discs upright in plastic jewel cases, in an area that is cool, dry, and free of large fluctuations in temperature and humidity. Regular checks of the data stored on these discs should also be part of your storage program. If you’re really committed to keeping data for a long time (forever?), you may want to consider a transfer to another storage media such as magnetic tape.

And above all, realize that times change, and technology changes. What may be cutting-edge today could be old news tomorrow. Remember floppy disks?