[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [ARSCLIST] Ampex 456
----- Original Message -----
From: "Peter@xxxxxxxxxxxxx" <lists@xxxxxxxxxxxxx>
My guess is that the manufacturers of magnetic recording tape never thought
it would need to have a significant lifespan! Its commercial uses (for
example, as recording master tapes [which only needed to last until the
record was pressed, in theory], recording radio programs for later broadcast
[thus only to last until the broadcast] and such implied a short life
followed by disposability! So...nobody thought about "let's see what
happens to the tapes in <timespan>"...
Steven C. Barr
> 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.
> > >
> >
> >
>