X-Message-Number: 2654
Subject: CRYONICS: Tape longevity
Date: Sat, 19 Mar 1994 23:42:19 -0500
From: "Perry E. Metzger" <>

> From: 
>         I don't believe it.  T.V. news broadcasts regularly pull video 
> footage older than ten years.  I have personally viewed VHS movies 
> older than 10 years.  Heck, I even know a guy (my dad) who listens to 
> 8 track cassettes more than 25 years old.

I do believe it because its a well known phenomenon. Although the
longevity of tape has increased thanks to experience in producing the
medium, it is routine to find that tape recorded in the early 1960s
has had the magnetic film detach from the substrate; in fact, much of
the problem of producing CDs from old records arises because the
master tapes have decayed. (Ten years is probably fine for analog
media -- I'd really hesitate, though, to see digital data recorded on
videotape stored for that long -- half inch nine-track tape is
probably good for longer). Furthermore, decay occurs in the tape
material itself. CDs are also expected to decay in the long run,
although not nearly so fast.

Color film undergoes extreme color decay, too. Look at some color
prints from the 1960s if you want to see an example. If you want long
term storage of color film, you are best off doing separations into
three black and white images, since normal silver halide black&white
film is far more stable than color film.

It has been theorized that copper telluride optical disks should be
stable for centuries, but I've never heard of any other medium
expected to last that long.

There is also the problem that in 100 years it is highly unlikely that
anyone will have equipment that can be used to play VHS or similar
tapes even if you can get them to surivive.

I would suggest that the proper strategy is to combine the following,
on the assumption that one of the two will work even if the other doesn't:

1) digitally record the film, and transfer the media ever few years.
2) produce a set of high quality conventional film prints which are
   stored in liquid nitrogen. Conventional film has the advantage that
   even if reproduction equipment isn't available in a century it will
   be trivial to produce, since it is so low technology. It is also
   likely to survive liquid nitrogen storage very well.


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