Magnetic tape deterioration

I would like to add a few points to some of the excellent email you have
recently gotten on this subject.

I am an expert in videotape restoration, and as such I get to see a
great deal of tape that is, shall we say, past its prime. In Doug
Nishimura's excellent memo, he gives you many of the reasons for tape
deterioration. One of the techniques he discussed is baking the tapes. I
very strongly urge readers *not* to consider doing this process
themselves.  Although this process has been used by some people in the
field that I trust, it must be done extremely carefully under tightly
controlled conditions for video tape.  Video tape that has stretched or
shrunk by as little as 1% may be virtually impossible to restore, and
the baking procedure is only used by our company as a *last resort*,
because in many cases it could destroy the master entirely. My
recommendation is that this procedure not be used unless there is no
other alternative (meaning that all other techniques have been
exhausted).

Although print through is a very big problem with audio tapes, it is not
a big concern with video tapes.  There are several reasons for this, one
of which is that the video information is helically recorded on the tape
so that a print through of video information is extremely unlikely, and
if it did occur, it would last for a tiny time (1 field).  In any event
in the hundreds of tapes that we have done, print through has not been a
problem for either the video or the audio portions of a video tape (even
though most audio tracks are longitudinal on video tape, print through
has not been an issue, partially due to the size of the tracks, the
strength of the field, the gap between tracks, and the size and position
of tracks relative to the overall tape).

Mr. Mark Ritchie's comments unfortunately contain some misinformation. I
am on the SMPTE committee revising the international recommendations for
videotape storing and handling which is currently in draft form and will
(hopefully) be released soon.  Although we are not allowed to mention
what is in the document, the recommendation of 50 Degrees F at 30% RH is
not the recommended conditions, and I know of no recommendation by any
organization or manufacturer that claims that the tape should be stored
in these conditions for 25 or 30 years, nor would state what the
condition of the tape would be after such a period of time.  In fact
"long" is considered only 10 years by many of the documents that are
either available now or under revision.

D3 is *not* a compressed format, and is a composite digital format.  The
digital format lineup is as follows:

    DCT - Compressed Component Format
    Digital Betacam - Compressed Digital Format, that is Component video
    D5 - Uncompressed Component
    D3 - Uncompressed Composite
    D2 - Uncompressed Composite
    D1 - Uncompressed Component

Currently we do *not* recommend Digital Video formats for long term
archival storage, and we strongly recommend to our clients not to use
Digital Video for these applications at the present time.  The reasons
for our position is as follows:

    *   This is a field of extremely fast technological innovation, and
        the "fallout" of manufacturers and formats is far from over.  We
        are in the midst of a "format war" and predicting the outcome is
        extremely difficult. As a result, the availability of machines
        or parts for any of these formats 15 years from now is extremely
        uncertain. Because these machines are so expensive the amount of
        machines that have been sold is extremely small, and even
        established formats that have sold many many more machines are
        difficult or impossible to get parts for at the current time.
        As a case in point, ask a SONY salesman how much a replacement
        front panel for a SONY 2000 1" videotaperecorder costs.  The
        answer will surprise you (they no longer exist).

    *   The chances of playing back an analog tape are quite good, the
        chances of playing back a digital tape after 15 years of binder
        hydrolysis may be very poor.  Unfortunately, when a digital tape
        (or a section of tape) fails it is a catastrophic failure, which
        means it cannot be played back--period. In our opinion the risk
        of a catastrophic failure is far too high with the current state
        of the technology.

    *   Very little digital videotape is currently being manufactured
        (as compared to other formats).  Tape manufacture is a
        continuous process that gets better with quantity.  Lower
        quantity means smaller batches, which means that the probability
        of variation of quality from batch to batch is higher which
        means that there is a better chance of getting tape that will
        not withstand the test of time as well as a format that is more
        popular. There are over 100 ingredients in videotape, and the
        recipe is a closely guarded secret for most manufacturers. Batch
        to batch consistency is a major problem in the industry.

    *   Lastly, do you really need to spend $50,000 for a videotape
        recorder for archival applications?  For most applications that
        do not involve broadcast applications involving multi-generation
        compositing, digital formats are overkill for the application.
        The technology is seductive, but may not be appropriate for the
        application.

Our recommendation at the present time is BetacamSP.  A new line of
machines have been recently introduced that are extremely cost efficient.
Tons of tape is made for this format, and we have experience with
several generations of machines in the field in harsh environments for
several years.  It is a component analog format (low color noise), has
very good frequency response, and all things considered a very good
format for the next few years until things settle down.

If you have any questions or need some help with tape restoration give
us a call 800-653-8434 (800-old-vidi). Our company currently has a large
quantity of both digital and analog videotape equipment, and as such we
are not biased in any particular direction. An interesting article on
this subject appeared in the NY Times, October 28,1993 Business Week
section.

Jim Lindner

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                  Conservation DistList Instance 7:46
                Distributed: Thursday, December 23, 1993
                        Message Id: cdl-7-46-001
                                  ***