The longevity of CDs and DVDs is not well understood by the average consumer. Many inexpensive (silver) CDs and DVDs last as little as 2 to 5 years and even best quality (silver) CDs can last a few short decades even when properly stored. Technical, industry standard, environmental "torture chamber" testing is one of the best current methods to accurately assess disc longevity.

Factors Affecting Disc Longevity:

• The reflective layer material. Silver can tarnish rendering the laser incapable of reading data on a CD-R. Gold and some alloys offer far superior reflective layers because they will not tarnish or oxidize.
• Dye stability. Phthalocyanine dye is a much more stable dye than cyanine or azo dye. Higher stability means significantly less dye fading which impacts the lasers ability to read/write data.
• Polycarbonate. Optical grade polycarbonate improves the ability to read and write data. Lower quality polycarbonate can be less clear and or have other characteristics that distort the lasers ability to read/write.
• Temperature and humidity. High temperature and humidity can cause oxidation in the silver reflective layer and cause certain dyes to fade.
• Intense Light. Bright sunlight and even office light can severely impact dye fade in some dyes.
• Poor quality lacquer coatings, which can permit oxygen and humidity to impact the dye and reflective layers.
• Solvents, like in felt tip markers, which can eat through the protective layers on a CD and cause the reflective layers and dyes to change.
• Excess pressure (like when writing with a ballpoint pen) can dent the reflective layer or scratch the polycarbonate making it difficult or impossible for the laser to read/write.

The consumer who buys inexpensive discs to store precious picture memories, critical data, and important movies and music is likely to experience disc failure resulting in an inability to read data previously written to a disc or even to write to an old disc. This is due to the quality of materials used in manufacture or through the improper handling of the disc.
Archivability is defined as the length of time data can be stored and accessed. There is NO single method or media capable of insuring 100% archivability.

The best procedures to insure archivability include:

• Use a highest quality Gold disc built for long life, like the KODAK Preservation CD-R or KODAK Preservation DVD.
• Store your media in a dark, dry, humidity controlled environment, and in a protective case like a jewel case to help protect the disc from scratches.
• Don't write on CD-Rs except in the center hub area. Ballpoint pens can dent the reflective layers and solvent based felt tip markers can compromise the reflective and dye layers.
• Utilize redundancy of storage methods; computer hard drive, high quality Gold disc (CD-R/DVD), hard copy of the data.
• Upgrade your redundant storage methods as new technology becomes available.

There are many articles and studies done to substantiate the basic information provided in this discussion. An excellent source for proper handling and storage of discs is called "Care and Handling of CDs and DVDs - A Guide for Librarians and Archivists", NIST Special Publication 500-252 written by Fred Byers and available from:

The National Institute of Standards and Technology
U.S. Dept. of Commerce
100 Bureau Drive
Gaithersburg, Maryland 20899
www.nist.gov

or contact: Steve Mizelle
President, KMP Media, LLC
(585) 279-9087
smizelle@kmpmedia.com

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