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From: cbp@foster.avid.oz.au (Cameron Paine)
Newsgroups: rec.audio.high-end
Subject: Re: Tape Squeals
Message-ID: <6998@uwm.edu>
Date: 16 Oct 90 13:12:20 GMT
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Approved: tjk@csd4.csd.uwm.edu

In <6869@uwm.edu> JFARRINGTON@EAGLE.WESLEYAN.EDU (Jim Farrington) writes:

>In reply to Steve Graham's squealing reels, I think I can throw some light
>on the subject (though you may not like the answer).  [...]

Following this topic has made me feel slightly ill... We have ~500 hours
of seminal local music which was recorded onto (predominantly) Ampex tape
between 1979 and 1985. I have banned playing these tapes until I find a
way of extracting the material and this thread has provided the first
concrete information I've encountered. I had developed a different theory
and I'll mention it briefly because I think it has some merit. Note, I'm
not arguing the point with Jim. 

Tape relies on air as a lubricant. A layer of air molecules is trapped
between the successive layers of tape as it is packed onto the take-up
spool. The trapped air reduces the adhesion between adjacent tape layers.
I offer three observations to support this theory:

  * the shape of the `cutouts' on tape spools can noticeably effect the
    tape packing density. I believe this is because there is a relationship
    between airflow over the tape and the size (and possibly the shape) of
    the cutouts.
  
  * tape that has been stored and not played for a long period of time
    produces the scrape-flutter effect; tape of a similar age that is
    used more frequently is less likely to exhibit the problem. I ascribe
    this to a gradual loss of the air layer over time.
  
  * I have successfully eliminated the scrape-flutter effect by repacking
    the tape. This is a very tedious process since the best effects are
    achieved by multiple (> 10) unspool/respool cycles. I have used both
    a tape machine and a cart-winding machine to achieve this.

>Last Formula 9 helps on the heads to reduce friction, but is not the whole
>answer.  What you need to do is go to a fabric store and buy some stuff called
>"Pellon", a non-woven material used as a backing when making clothes. [...]

I fear that `Pellon' is a trade name, which is why I am having difficulty
locating it. Do you have any idea of its composition? Alternatively, do
you know who makes it?

I assume that you've attempted this process yourself. What effect does the
friction caused by the Pellon have on the oxide layer. Some of our tapes
are from BASF and these are notorious for shedding their oxide. Have you
noticed any disturbance in the dimensional stability of the base material?
Any other nasty side effects?

For those who are interested, I've posted a related article that explores
the next step - a better archiving medium.

Cameron (aka O.B. Coordinator, Radio 3PBS-FM, Melbourne, Australia)
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