Re: [AV Media Matters] Newbie to list question - tape baking, is it

[midshires@cix.co.uk]

>However, my view is that Ampex *had* a perfectly good product which
>was changed without proper accelerated life-testing (which would have
shown
>up this problem quite quickly)

Not necessarily. You need to look at the complete set of facts. Recording
tapes in the 1950s and 1960s were made using whale oil, and users indeed had
no major problems. At least not with the performance of the tape but more
with their consciences and the ecology lobby. Pressure was put on the tape
manufacturers to find a synthetic substitute for the whale oil and that's
when the hydrolysis problems began. Accelerated life testing has its uses
but is not a complete substitute for prolonged and practical 'in-the-field'
experience. You have only to look at dozens of different plastic products
that have become brittle or distorted as a result of plasticisers leaching
over time -- or once-beige and attractive-looking computer peripherals and
photocopiers that have turned a foul nicotine brown in six or seven years.
Plastics technologists are clever guys but not always as clever as they
think they are.

My understanding is that in the mid-1970s,  3M (Scotch) and Ampex, both
major tape manufacturers, started experimenting with their formulas. They
thought they were introducing major improvements,  but instead created a
tape much more prone to hydrolisation than anything had ever been. Because
the problem did not show up for years,  the formulas did not get  corrected
until sometime in the mid-1980s. Theoretically any tape could get hydrolised
over a long period of time, especially if stored in a high-humidity
situation, but in practice most squeaky tapes were made (roughly speaking)
between 1975 and 1985.

The OTR FAQ has the following to say on the subject:

A20.  There are at least two causes for 'squeaky reels' on a reel-to-reel
tape recorder.  (1) The tape edge may be rubbing against the rim of a
distorted take-up reel, or (2) the oxide  may be sticking to your erase (or
other) heads.  If the former, the least frustrating alternative is probably
a new take-up reel. If the latter, Fred Korb left this note:
 If you have any squeaky reels that you would like to recover, I will be
glad to send you more information on how to do it. Just send me a  stamped
self addressed #10 envelope and I will  respond. Send your request to: Fred
Korb, c/o Oldtime Radio Collectors and Traders Society, 725 Cardigan Court,
Naperville, Illinois 60565-1202. I am willing to help you preserve the
sounds of radio days gone by.

[Editor's note: Fred's method consists of a kit by which a
lubricating film can be automatically applied to the tape as it is
played. I tried it. Although temporary, it does indeed work! I'd
recommend it for those squeaky tapes that you wish to re-record onto
newer reels.]

Richard Fish <lodeston@bluemarble.net> also left this helpful info
about an alternative method:

Hydrolisation is the culprit.  The tape material - the  backing, or
the binder compound used to stick the magnetic particles to the
plastic backing - has absorbed water from the air.  The water
molecules actually make  the tape expand a bit, so it doesn't fit
the machined tape-guides properly anymore; and they can interfere
with  the lubrication impregnated into the tape; and it is theorised
they can even interfere with the polished smoothness of the tape
surface.

The lubrication system was certainly used in this country (Great
Britain). A friend of mine, who worked at Ashford (Middlesex) for
Sony, told me kept a special tape transfer bay for replaying
squealing tapes, in which distilled water was applied to the tape
immediately ahead of the replay head. The recovered signal was then
re-recorded onto new tape. This plant was retained for many, many
years just in case customers sent in squealing tapes.

Finally, as for the validity of patents, it may be worth remembering
what a patentee is granted -- namely, the right to protect his/her
invested efforts (for a defined period) against commercial
competitors. To secure compensatio n from an infractor, the patentee
would have to demonstrate commercial loss. Given that people using
the baking technique to recover 'lost' or fugitive information would
have demonstrably suffered loss at the hands of the self-same
patentee, they would have the weight of  moral  right on their sides
and only a foolhardy tape manufacturer would seek to drag its
reputation into disrepute by bringing a case for infringement.

Andrew Emmerson,
Writer for Television Technology & Broadcasting magazine, Studio Sound, etc.
etc.

Date: Wed, 22 Dec 1999 16:20:48 -0800
To: AV-Media-Matters@topica.com
Subject: RE: [AV Media Matters] tape baking
Message-ID: <0.10003996.2074567266-212058698-945908428@topica.com>
MIME-Version: 1.0
Content-Type: text/plain

William Real wrote
>It should be possible, for example, to articulate how baking
alters, if at all, the other materials (besides the signal and the binder)
present in the physical "artifact" that might have some cultural value of
its own.

The third component in the physical artefact, or tape is the substrate,
polyethylene terapthalate (PET), which expands and contracts at a rate of 1
x 10-6 metres per degree centigrade, and does the reverse at double the
level per %RH.  You can find this standard figure in data books.  A reel of
tape is quite long and so this small change can become significant, and the
baking can cause deformation of the tape pack.  However, careful spooling
and respooling tends to alleviate the problem and baking does make the tape
playable.

Jim Wheeler wrote
>Testing at the Australia National Library indicates that the only problem
with baking audio tapes at 120 F is about a one db loss at high frequency.

In the testing referred to above we also found that the temperature was
critical (though the loss was under 1dB)  Baking at very low temperatures
and humidities may make the tape playable over very long periods, but did
not entirely reverse the artefacts of binder degredation, likewise with
surface cleaning such as pelon.  Very high temperatures can damage the tape.
We bake at 60 degrees C which is about as low as we could get and still be
effective.

However, with the testing we carried out with hundreds of degraded tapes we
did find a lot of variations that were all grouped together as "Hydrolysis"
or "Sticky tape syndrome".  It is difficult to tell if they are all the same
phenomenon, though they do all respond to similar treatment.  So far an
unambiguous description at a molecular level has evaded the chemists who
have attempted to investigate the problem, which is not to say they haven't
found some pretty good insights.  I look forward to the upcoming JTS for
further developments.

Kevin Bradley
a/g Manager: Digital and Audio Preservation Resources
National Library of Australia
Canberra   ACT 2600
AUSTRALIA

Tel:  +61-2 6262-1381
Fax: + 61-2 6262-1653
Email: kbradley@nla.gov.au
NLA home page: http://www.nla.gov.au
Change is inevitable, except from a vending machine

>----------
>From: 	RealW@CarnegieMuseums.Org[SMTP:RealW@CarnegieMuseums.Org]
>Sent: 	Thursday, 23 December 1999 6:04 AM
>To: 	AV-Media-Matters@topica.com
>Subject: 	RE: [AV Media Matters] tape baking
>
>Jim Lindner wrote:
>"Most often we are concerned about the material that is recorded on the
>tape
>but not about the artifact itself - but that is not always the case. In
>some
>cases there is great value to the original artifact - and baking any
>artifact or doing other types of things like this is a major issue in the
>conservatorial world.  I had the fortune of working on Andy Warhol's
>original videotapes.... if there were nothing on them - they still had
>artifact value.  Is it appropriate to bake tapes such as these?  That is
>an
>open question and I would be interested in hearing what people think."
>
>Readers of this list might be interested to know that many conservators
>refer to a document, the AIC Code of Ethics, for guidance in making sound
>decisions about how to treat the objects entrusted to them. The document
>can
>be found at http://conservation-us.org/pubs/ethics.html
>
>Readers might also be interested to know that conservators often employ
>methods that, in untrained hands, could indeed be disastrous, but are not
>in
>themselves necessarily inappropriate conservation techniques. These
>include,
>for example, heating and humidifying paintings, washing works of art on
>paper, and cleaning sculptures with lasers.
>
>An overriding principle in the conservation profession is that there are
>no
>individual techniques that are appropriate in every instance. The decision
>about what method to use is guided by careful judgement based on the
>characteristics of the object to be treated, the goals of the treatment,
>and
>the experience and ability of the conservator.
>
>In the case of baking polyester recording media vs. other treatment
>methods,
>it would be interesting to have some quantifiable information to
>supplement
>the useful empirical and anecdotal information that has so far been shared
>on this list. It should be possible, for example, to articulate how baking
>alters, if at all, the other materials (besides the signal and the binder)
>present in the physical "artifact" that might have some cultural value of
>its own.
>
>William Real