Dead Media Beat: compact disk rot

*The US Library of Congress torture-tests a variety of compact disks. Some last splendidly, they're good for centuries, just like the industry used to claim when they said they would outlast vinyl records. Others decay pronto, eating themselves up in twenty years. Unfortunately the disks were manufactured in a wide variety of ways and nobody kept track of the parameters that might cause them to "rot."

*Keeping them cold and dry seems to help.

https://www.loc.gov/preservation/resources/rt/CDservicelife_rev.pdf

Viewing the data as a histogram shows that the data is distributed in clusters of life expectancy values, with the majority of failures clustered at the beginning of the graph, and smaller clusters popping up at various points further out along the X-axis, showing a wide range in the quality of compact disc media relative to factors that affect longevity.

This distribution of life expectancy may be the result of various construction parameters such as type and cure of sealcoat layer, paint used to print the label, presence of corrosion inhibitors in the reflector layer, thickness and purity of materials, or other physical characteristics. The results of this experiment demonstrate how differences in disc composition make it difficult to predict the lifetime of optical discs on a grand scale, or define an "average lifetime" for this type of media. There are too many variables in the manufacturing process, and formulations change over time….