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Re: [ARSCLIST] Ampex 456
Sorry for the delay in answering this thread but my E-mail went screwy on me
for a few days.
We have tested over 300,000 audio, video and data tapes. Thousands of these
tapes have exhibited binder hydrolysis. Thousands of others, however, have
had other problems. When we use elevated heat treatments, our incubation
times range from 3 hours to over 120 hours. The tapes that respond to 3
hour heat treatments exhibit frictional problems before treatment but do not
show significant amounts of low-molecular-weight oligomer residue. One tape
(our longest treatment), was a 2" audio tape that was so degraded that the
recording surface had a consistency similar to custard and could be scraped
off with a finger nail. 8 to 12 hours of treatment was ineffective but
after 160 hours, the tape played down without significant problems.
We also use laboratory ovens/incubators that are stable to 1/2 a degree,
have slow ramp up/down times and overheat safety shut-offs. We do not use
boxes with light bulbs. We have multiple incubators as we have found that
different tapes, at different stages of decay, require different
temperatures and different treatment times for best results. Frankly, I'm
surprised at the short incubation times most of the people in this thread
have recommended for SSS. Are the tapes being reported on tested prior to
treatment, to confirm the presence of oligomer residue, or is
short-duration baking sometimes done without prior confirmation that binder
hydrolysis is actually the problem?
Another issue that was brought up in this thread is the effect of the
backcoat on SSS. We have seen sufficient evidence that backcoating can act
as a decay catalyst that we feel the issue is pretty self-evident. On the
other hand, we have examined and treated a number of non-backcoated tapes
with SSS. It is rare, and mostly shows up in very early Scotch 2" video,
but it does exist. As such, SSS DOES happen on non-backcoated tapes!
Some interesting test results we collected during research into dealing with
binder-base adhesion failure may shed a little bit of light on moisture/heat
issues dealing with alleviating SSS. The "cold desiccation" process we
developed to reduce binder-base adhesion failure also works to treat SSS,
however, there are conditions where it should not be used:
When some tapes are badly hydrolyzed, the oligomer residue collects on the
tape surface in visible "puddles"(not my term, I got the "puddles" term from
an "un-named" manufacturer's R&D department). If tapes with these puddles
are subjected to "baking" (low moisture/high temperature), the puddles
reduce in size and disappear, leaving a smooth, fairly even tape surface.
(Note- if the puddles are chemically removed prior to treatment, the tape
thickness where the puddle was located is greatly reduced). If the tapes
with puddles are subjected to "cold desiccation" (low moisture/low
temperature), the puddles remain on the surface of the tape and harden into
a substance that can no longer be removed from the tape. The "hardened
puddles" are no longer soluble in chemicals used for extraction testing and
no longer shrink if subjected to heat. These hardened "puddles" act just
like binder material!
The testing we did shows that, whatever else "baking" does, the elevated
temperatures can cause some decay residue to be re-absorbed back into the
binder. Our testing also shows that removing moisture from some decay
residues alters their chemical structure (cross-linking?) so that the
resulting material acts more like the original binder.
Another interesting test result we have come up with is that, in certain
circumstances, the longer a tape is treated, the longer it remains playable.
I have often heard people claim that, after treatment, a tape must be played
down ASAP. We have done extended treatments to a variety of tapes and found
that some of them were still playable at least 6 months after the treatment
(Granted, such extended treatments are not commercially viable, but the
results are interesting from an informational point of view).
Tape decay is not a simple one-stop-shop and a lot of additional research
should be done( I applaud Richard's initiative and have been putting my 2
cents, as time allows). If we had not continued our research we would not
have found a way to deal with binder-base adhesion failure- a condition that
many simply considered terminal.
One thing I would warn about is not to throw the baby out with the
bath-water. Simply because testing and observation show that moisture is
VERY unlikely to be the only factor in SSS does not mean that it is not a
factor at all. Testing strongly indicates that it is a major factor.
Again, just because back coating seems to catalyze the decay reaction also
does not mean it is the only factor (binder can decay without the presence
of backcoating). Due to our testing, we've known for over a dozen years
that heat causes some decay residue to be re-absorbed into the binder but
that does not mean that cross-linking does not also occur. Some of our
procedures are also based on the premise of cross-linking.
The more we know, the more we can do. Just because new research indicates
additional factors/reactions are likely occurring, however, does not
necessarily invalidate older research. Theories and conclusions can be
incomplete without being totally invalid.
Peter Brothers
President
SPECS BROS., LLC
(973)777-5055
www.specsbros.com
Restoration and Disaster Recovery Service Since 1983
> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx]On Behalf Of Robert Hodge
> Sent: Thursday, June 22, 2006 10:55 AM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: Re: [ARSCLIST] Ampex 456
>
>
> The 64 and 40 hour numbers are based upon using a labratory grade
> incubation oven.
>
> The Belfer Audio Archive does not use devices such as food dryers as
> part of its' preservation and restoration programs..
>
> R. Hodge
>
> Robert Hodge,
> Senior Engineer
> Belfer Audio Archive
> Syracuse University
> 222 Waverly Ave .
> Syracuse N.Y. 13244-2010
>
> 315-443- 7971
> FAX-315-443-4866
>
> >>> parker@xxxxxxxxxxxxxxxxx 6/16/2006 6:12 PM >>>
> Agreed. I have Bill Lund's notes on this subject for an AES
> presentation he
> made, and his recommendations are largely consistent with a Quantegy
> engineer's recommendation who contacted me several years ago.
>
> I can only guess that the 64 hours and 40 hours suggestions for baking
> time
> are for food dryers or some other low wattage device.
>
> When confronted with the much larger mass of the 2" tapes, low wattage
> devices might well take much longer to reach the desired temperature. A
> good
> convection oven with steady air movement that reaches and maintains
> the
> proper temperature shouldn't take 64 hours.
>
> I routinely used to treat up to fourteen (14) 2" reels of Ampex tape
> for ten
> (10) hours with excellent results, all at one time. There were spaced
> with
> 1/4" hubs for improved airflow. That's something like 140 pounds of
> tape.
>
> And the tapes I treated were stored in New Orleans, where there is
> plenty of
> moisture.
>
> ---
> Parker Dinkins
> MasterDigital Corporation
> CD Mastering + Audio Restoration
> http://masterdigital.com
>
>
>
> on 6/16/06 4:05 PM US/Central, Tom Fine at tflists@xxxxxxxxxxxxxxxxxxx
>
> wrote:
>
> > Bill Lund, formerly of 3M, and a tape chemistry expert, suggests 12
> hours
> > bake, 12 hours cool to
> > room temp before playing. I trust Bill and have used that method
> successfully
> > numerous times.
> > Earlier experiments with shorter times were not residue free but did
> result in
> > playability.
> >
> > No offense to the LOC, but Bill actually worked at 3M and was
> involved with
> > figuring out what was
> > wrong with Scotch 226.
> >
> > -- Tom Fine
> >
> > ----- Original Message -----
> > From: "Robert Hodge" <rjhodge@xxxxxxx>
> > To: <ARSCLIST@xxxxxxxxxxxxxxxx>
> > Sent: Friday, June 16, 2006 10:09 AM
> > Subject: Re: [ARSCLIST] Ampex 456
> >
> >
> >> Hi,
> >>
> >> I suspect that due to the increased surface area of your tape, you
> >> would have to increase the baking time normally used for 1/4 inch
> tape.
> >>
> >> Library Of Congress recommends 8 hours at 130 degrees for pre 1975
> and
> >> 5 hours at 130 degrees for post 1975 and later for 1/4 inch tape.
> >> I've never baked 2 inch , but this is the path I'd follow unless
> >> someone has done it differently with success.
> >> 64 hours at 130 pre 1975 and 40 hours 130 for 1975 and later.
> >> ( Seems like a lot. ) But the math indicates it so. And the same
> >> amount of time for cooldown which is equally important..
> >>
> >> Best of luck !
> >>
> >> Bob Hodge
> >>
> >> Robert Hodge,
> >> Senior Engineer
> >> Belfer Audio Archive
> >> Syracuse University
> >> 222 Waverly Ave .
> >> Syracuse N.Y. 13244-2010
> >>
> >> 315-443- 7971
> >> FAX-315-443-4866
> >>
> >>>>> arclists@xxxxxxxxxxxxxxx 6/16/2006 8:42 AM >>>
> >> At 06:51 AM 6/16/2006, Lars Gaustad wrote:
> >>> Hi,
> >>> I have got a 2" Apmex 456 that is really sticky.
> >>> I has been stored at 8 C 35% RH for 8 years,
> >>> which makes me believe that the stickyness is not related to
> >> hydrolysis
> >>> (SS),
> >>> as such storage should rejuvenate the tape just as well as baking
> >> will.
> >>>
> >>> Any suggestions?
> >>
> >> Baking should still rejuvenate it if past history is any guide. I'm
> >> looking for a good explanation of precisely why baking works, but
> >> I've been told by people who understand these things that the
> >> generally accepted explanation is not the whole story.
> >>
> >> There does appear to be mounting evidence that there is interaction
> >> between the back coat and the oxide binder system. Again, no
> answers
> >> at this time.
> >>
> >> I'm not being mysterious, I'm slowly studying this.
> >>
> >> Thanks for a really useful data point.
> >>
> >> Many of the people working on this are not on this list and I'm
> >> taking the liberty of passing on your observations to them.
> >>
> >> Cheers,
> >>
> >> Richard
> >>
> >>
> >>> lars gaustad
> >>> preservation adviser
> >>> national library of norway
> >>> www.nb.no
> >>
> >> 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.
> >
>
>