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

[rohre@arlut.utexas.edu]

Yes indeed,
Computer reel to reel tapes are the same basic construction as audio,
instrumentation reel to reel, and any Gamma Ferric Oxide formulation.  8mm
tapes of earlier types, and a number of other formats are of this type.

Most of the video type tapes were backcoated when VHS tapes did well with this
formulation.  Backcoating is simply a carbon type treatment that aids in
reducing print thru, lessens tendency of plastic layers to stick to the next
wrap, and was a great advance in tape construction.

Back coating reduces tendency of base film plastics to acquire a static
charge, and this helps tapes to pack well in high speed winding.

Because film is also a plastics technology, many of the storage considerations
for all tapes and films are similar.  Low humidity, a cool environment, and
careful handling to avoid dust pickup and contaminants are aids to long life.

Since CDs and DVDs are also plastic substrates, although thicker than tape;
they too will last longer if not subjected to abuses of high tempeartures,
dusty environments, etc.  Of some concern to me for archival masters is the
tendency of all plastics exposed to UV in lighting or sunlight to eventually
become embrittled.  Plastics have chemical constituents that out-gas or
evaporate over time, and I believe the decay mechanism is the loss of those
solvents or compounds, and in some plastics like tape urethane binders, the
uptake of mosisture into the molecule.

Stuart M. Rohre
ARL:UTX