"Calif Bill" wrote in message
link.net...



Burned CD's can change. The reason being the construction. The critical
part of a CD is not the clear side but the shiny side. A pressed CD has
the dimples pressed in and then the coating is applied, and the distance
from the surface to the reflective coating does not change. A burned CD,
diffuses an internal material. If heat and chemistry happen, that
diffusion can grow or change. The reason a CD works is the light source
is reflected from the shiny coating or the diffused internal area. The
diffused or dimple is 1/2 wave length in depth, so you get a cancellation
of light. A dark spot. If there is damage to the reflective surface,
then bad data.



I read at some point in time:

A burned CD has an approximate storage life of only 3 years before it can
start having data errors simply due to aging. They are not recommended for
long term storage of important documents or files.

Interestingly, magnetic media (tapes) have an estimated data storage life of
approximately 100 years.

Eisboch