RE: [AV Media Matters] Regular winding/rewinding of tape and film.

[rohre@arlut.utexas.edu]

A presentation by Sony to our Lab on 8mm formats several years ago, stated an
minimum expected lifetime for conventional oxide 8mm tape, (versus Metal
Particle) of 50 years, given GOOD STORAGE CONDITIONS.  But, how many tapes,
really are written once and then put away, and not put back on a machine as
most are in a library of active data?  Thus, reuse is a life factor.

The emphasis on storage is mine, but that is the key.  No matter the format,
if the storage conditions do not control both temperature and humidity well,
many formats will not last as long as they could under ideal conditions.
Cuddihy of JPL did a paper showing virtually unlimited life for tape of
plastic basefilm and oxide layer, if it was stored at neutral humidity and a
suitably lower temperature.
Although I believe his data was based on accelerated life testing on tape
coupons, his paper remains one of the best test reports on the issue of tape
lifetime.  Other factors affecting any plastic based media include
ultraviolet, and environment that would encourage outgassing of the solvent
constituents of the plastics.  (The things that wear out your plastic
automobile dashboards).
Many materials are also affected by other elements of the atmosphere, and in
some applications, we used a dry nitrogen environment to protect recordings
being made in a deep ocean buoy.

Of course, JPL was concerned with such issues, because of the tape recorders
needed in deep space probes that take years to get to Jupiter and the outer
solar system.  The recorder serves to accumulate data as digital streams that
can then be replayed at the low data rate needed by the deep space
transmission link.

If the base film remains flexible, the metal particle formats might be a long
life archival coating, because of the smaller particle and thus more intimate
bonding to the base film.  Some early CDs had issues of being read because of
dyes used in coloring the labels, but current ones should have the life of any
plastic of that type.

Almost of as much concern, is will there be a transport capable of playing the
media, after years of storage?  With the rapid evolution of small formats this
is a bothersome question for the archivist today.