RE: [AV Media Matters] Print-through

[Graham Newton <gn@audio-restoration.com>]

Stuart Rohre
rohre@ARLUT.UTEXAS.EDU posted to AV-Media-Matters@topica.com...
On the subject: Re: Print-through

>Steve raises a good point about those tapes having stiction near the hub.
>I too, have seen that, but luckily on the instrumentation reels, there is
an
>obvious packing difference there, when there is layer to layer adhesion.
>Always look at the pack before moving tape on problamatical older ones,
and
>Steve's bake first seems to do no harm.
According to conversations I have had with engineers at Ampex (now Quantegy)
the "bake first" idea may not be a good practice.

The current thinking is that baking is finite and has a limit to the number
of
times you can recover a tape by the baking process.  It seems that each time
you bake, you drive out some of the components that aid the process, thus
making it progressively more and more difficult to achieve a stable and
usable
result.

The end point is a condition where baking will NOT reverse the sticky
condition
and your tape is trashed for good, unless some other process is worked out
that
will compensate accordingly.

It is already well known that a baked tape will revert to the sticky
condition
within a matter of time depending on humidity of storage conditions and thus
will require baking every time it is to be re-used, presuming enough time
has
elapsed between the baking and the next usage requirement.

The safest guidelines appear to be:-

Bake ONLY when needed for transfer purposes

Use the MINIMUM temperature range (120 - 130 degrees Fahrenheit or lower)
and
the MINIMUM duration (estimated 3 to 6 hours) to accomplish the task, that
is,
driving out the moisture that is causing the sticky-shed problem.

Be prepared to do the BEST possible transfer to another medium, and do it
promptly, within a few days of completing the baking process

Leave the tape in tight wind, tail out condition, and return it to storage.
I suggest tight wind, tail out, since I can't think of any better means to
store them, even though the sticky-shed problem results in the expansion of
the
tape layers due to the moisture accumulation, and the inner layers will thus
be
subject to pressures that may cause its own damage.  At least the even wind
will minimize the audibility of such damage.

These measures will conserve the "bakeability" of the tape for possible
future
needs.

Since technology will progress, there will doubtless come a time when better
transfer or restoration means are at hand and it will be desirable to
re-transfer the deteriorated tape.  It would be prudent to make it easier to
do
so by following the above guidelines.

... Graham Newton

--
Audio Restoration by Graham Newton, http://www.audio-restoration.com
World class professional services applied to phonograph and tape
recordings for consumers and re-releases, featuring CEDAR processes.