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Re: [ARSCLIST] S-S-S and tape baking
Hi, Mike,
I replied on the Ampex list, but will here as well since there are
many people who are not on both lists.
Tom: <blush>
At 11:39 AM 6/4/2006, Mike Csontos Mwcpc4@xxxxxxx wrote:
About twelve years ago I salvaged tape from a local studio's radio commercial
masters for editing transfers of some oral history material for cassette
access. The tape was in Ampex 291, 414, 405; 3M 201, 175, and many
white boxes,
various lengths.
I found that black oxide back coated tape was useless because of SSS,
non-back coated tape was fine, regardless of oxide shade, and brown
oxide back coated
tape seemed OK. At the time I thought the SSS was a function of the oxide,
not the backing so I interspliced the scraps of brown coated and
non-back coated
tape.
...
Obviously mixing types of tape on a single reel is not good practice and
nobody on this list would do that, but this provides some idea of the wide
variation of tape condition over time even under identical storage
conditions (on the
same reel).
Mike,
I have been digging into this issue for several months now and I am
not much closer to an understanding than I was when I started. In
fact, the more I learn, the more I need to learn.
I have been reading "Tribology and Mechanics of Magnetic Storage
Devices, 2nd Edition" by Bharat Bhushan and have been talking to a
bunch of tape people.
What we think we know about why baking works may not be the whole
truth - I don't have a good summary yet as to what the truth is, but
chemists smarter than I have told me this.
There are perhaps 5-10 possible causes of squeal, and there is no
easy method yet to diagnose what the cause is. Without a diagnosis,
any attempted cure is craft not science. It's not that craft is bad,
it gets the job done, but I much prefer to understand.
One thing I have learned is that polymer chemistry/mechanics/physics
is VERY complex and, in fact, not necessarily completely understood
by former practioners. The science has advanced greatly in the last
twenty years in data tape, only some of that has filtered back to
audio tape. I'm not sure about video tape as I haven't been researching that.
Yes, there appears to be a correlation between back coating and SSS.
In an informal survey I took a month or so ago with one exception all
tapes that have responded to baking have also been back-coated.
Most if not all tapes that squeal and do not respond to baking are
NOT back coated. We have been calling these "loss of lubricant" tapes
but, again, there are many hypotheses relating to the cause of the
squeal, and most do not involve an actual loss of lubricant.
I feel that I'm back at square one, but will keep digging.
I think the only safe thing to say is that we cannot predict with
certainty the expected lifetime of any single reel of tape. I know it
sounds self-serving to say this, but if the tape is important, it
should be digitized.
While in this thread (and previously), Tom Fine has reported
excellent results with 111, I have seen some MINOR degradation
starting to set in on 111, and there have been some reports on
vinegar syndrome advancing on 111--rare, but not unknown.
It appears that while I thought it didn't matter when you baked, it's
now looking as if the degradation is progressing and hasn't
necessarily stopped.
I think if the tape is acetate or is on any of the known bad tapes,
it definitely needs to be transferred sooner rather than later.
Some known bad tapes are listed here:
http://richardhess.com/notes/2006/05/17/sticky-shed-loss-of-lubricant/
You can find the above article and a growing collection of tapetravesties at
http://richardhess.com/notes/category/archive-operations/tape-aging/
Some people suggest not trusting important tapes past the age of ten
years. One of these is a person who led tape making at a major manufacturer.
One copy of anything important is always a huge risk, but has been the norm.
Cheers???
Richard
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.