How permanent are CDs?CDs are complex laminate structures vulnerable to damage by light, humidity, temperature mishandling, and pressure. Since CD information is stored in blocks of data with EDAC correcting codes it isn’t easy to determine when a CD is about to fail. CDs can be destroyed in a few minutes through poor handling or damaged from a few hours of being stored outside of their jewel cases. Since CDs vary little over time (until they fail), they may be duplicated without generational loss of information.
Storage or handling that would not destroy tape or paper, such as bending, pressure, or light exposure, can destroy a CD. Don’t count on CDs to last many decades because the polycarbonate substrate used on most CDs has a shorter life than paper or film. Few companies warranty their discs for more than a decade. Don’t dispose of your paper or film originals when using CDs for access copies. Most CD's fail because of:
- Physical stress leading to delamination, warping, and/or improper tracking
- Dirt or grit scratching media and leading to losses of information
- Yellowing of the plastic or light recording layer
- Low reflectivity due to oxidation of the aluminum layer (also known as laser rot)
Many CDs include a lacquer for durability, a reflective layer (usually aluminum; sometimes more stable gold), dyes (most frequently organic), and a substrate (often polycarbonate plastic, sometimes metal or etched glass) onto which the signals are etched by laser light.
Unlike CD-Rs containing cyanine, which lose their characteristics more quickly from exposure to light and heat, gold CD’s offer increased stability, longevity and durability .
Accelerated aging tests by the manufacturer show that MAM Gold can be used as a reliable storage media for more than 300 years.
All of the main components in the MAM Gold CD-R are very stable in the environment; plastic (polycarbonate), Phthalocyanine dye and gold (which does not oxidize).
Don’t get your preservation data from vendors. In the past vendors have often not disclosed when their products were non-archival or shortlived.
Additional information on preservation sources for media production, storage, housing standards include: