RE: [AV Media Matters] Convection Oven

[Jim Wheeler <Jimwheeler@aol.com>]

I believe that it is low humidity that is required to
"rejuvenate" the tape
binder and one way to obtain low humidity is to increase the
temperature.
Another way would be to seal the tapes in a container with
desiccant but at
room temperature.  This method would probably require a couple of weeks.

I always monitor both the temperature and the humidity in the
oven.  I keep
the temperature around 115 F.  I bake for 15 hours and have only
had a couple
of really bad tapes that I had to bake a second time.

Des Maderias was the Ampex engineer who discovered the baking technique
initially working on tapes I received from Richard Warren at
Yale.  Des found
that the baking made the tapes playable for at least a week and
as much as a
few months.  When the tape became unplayable again, he baked it
again.  He
repeated this process for many cycles over a three year period.
Des does not
recommend doing this.  He only did it to see if the process is repeatable.

I recommend baking to make the tape playable and then copying it.  After
copying it, store it in a cool and dry environment.  This is
critical if you
want the original to survive for many years.

I do not recommend cleaning tapes unless done by a professional.

The material that oozes to the surface never was properly
cross-linked so was
never part of the recording.  So, cleaning this debris off the
surface does
not deteriorate the recording as some people seem to have
assumed.  These are
short-chain oligimers with no useful purpose in life.

The change to urethane binder started in 1968.  BASF stayed with
PVC binder.
Does anyone on this Listserve have BASF tapes with sticky-shed?

Jim Wheeler