X-Message-Number: 2655
Subject: CRYONICS Videotape
From:  (Charles Platt)
Date: Sun, 20 Mar 94 11:15:38 EST

Re magnetic tape:

It is true that old tapes may hold up well. I own open-reel 
four-track audio tapes from thirty years ago, and I can still 
play them. 

Video, however, is a different matter. The tracks are far 
narrower, they are recorded diagonally across the tape, and 
the timing of the signal is far more important. Thus, if the 
tape shrinks slightly, it can seriously affect the picture. 
By comparison, if audiotape shrinks slightly, the results are 
barely detectable. 

Another long-term problem is that the binder (which glues the 
magnetic particles onto the mylar tape) can deteriorate with 
age, with the result that metal oxide particles fall off the 

"Print through" is also a problem, especially with very thin 
(long-playing-time) tapes. The coils of tape, tightly wound 
in the cassette, affect each other magnetically. For this 
reason, it's often recommended that tape should be wound and 
rewound periodically, to reposition the "layers" with 
reference to each other. 

Lastly, of course, tape can be demagnetized. Even if there is 
no interference from a magnetic field, it seems that very 
small fluctuations in the magnetic pattern can gradually 
disappear over time. I have noticed that my very old 
audiotapes have a poorer frequency response now than when I 
first recorded them (and this cannot be entirely explained by 
my aging hearing). 

For archival purposes, tape sucks. Unfortunately, however, 
there are no substitutes. We'll have to wait another twenty 
years or so for EPROMS to be big enough and cheap enough to 
store video. 

In the meantime, I suggest that archives should include 
monochrome photographic negatives, and perhaps color xeroxes 
on acid-free paper. These are two very stable ways to store 

--Charles Platt

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