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Re: [ARSCLIST] Ampex 456 - Research
Tom,
Funny you should mention it (funding some tape-specific research). I'm
working with Lars Meyers at Emory University to submit a research grant
applicaiton to NEH (major funder of Karl Haber's work on optical
playback of discs & cylinders). Our precis was accepted and we were
invited to submit a complete proposal to do some hard science on SSS.
After some discussion in/around the ARSC Technical Committee, we've
decided to postpone the submission until after we have more input (from
Richard Hess and others). There's a chance ARSC may be directly
involved in this endeavor, but we've barely begun discussions.
Stay tuned.
George Blood
Safe Sound Archive
-----Original Message-----
From: Tom Fine <tflists@xxxxxxxxxxxxxxxxxxx>
To: ARSCLIST@xxxxxxxxxxxxxxxx
Sent: Fri, 16 Jun 2006 20:36:11 -0400
Subject: Re: [ARSCLIST] Ampex 456 - tip of the iceberg...chemistry
You know, there should be a special ARSC meeting on this, maybe in
conjunction with the AES. Let's get the authors of these papers and
books if they can be persuaded. Let's get some good Chem 101 professor
to explain all this in layman's terms and let's see if some of the big
holders of tapes with a lot on the line (ie the record companies and
such large institutions as the LOC) can put up some $$$ to fund some
tape-specific research. I also think if one asked in the context of
getting to the bottom of this, the folks that Quantegy might share the
recipes for the sticky tapes (I understand they bought all of 3M's
recipes so they must have documentation on hand). I can't understand
why, all these years after this problem has been discovered, that there
are all these questions. It seems like the answers are known but the
dots aren't connected. Richard Hess has done the most dot connecting of
anyone who I know of who seems willing to share the information. He's
got a studio to run and he doesn't own a chemistry lab. So it seems
like there would be vested interest of the owners of all these valuable
sticky tapes to step up and make the answers clearer. Maybe there's a
political issue I'm not seeing?
-- Tom Fine
----- Original Message ----- From: "Richard L. Hess"
<arclists@xxxxxxxxxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxxxxxx>
Sent: Friday, June 16, 2006 8:05 PM
Subject: Re: [ARSCLIST] Ampex 456 - tip of the iceberg...chemistry
> Hi, Tom,
>
> The problem I'm having is connecting the dots. I'm talking with
chemists who understand these > things far better than I do and there
is some indication that some of the preliminary conclusions > in
Richardson's patent are perhaps closer to what really happens than what
Ampex says in their > patent or Bertram/Cuddihy in their paper. It's
all very complex and even the measurement > techniques are open to
interpretation.
>
> What we know from a large body of knowledge is that
baking/incubation works for the vast majority > of back-coated tapes. I
am less sure we know how/why it works precisely. We also know that with
> one or two exceptions, it doesn't solve any problems on
non-back-coated tapes.
>
> We can create a hypothesis that back-coating in contact with binder
has a catalytic effect on the > degradation of the binder. Additionally
we have a preliminary, back of the envelope level, study > that
suggests that there is truth in this, thanks to John Chester: >
http://stuff.jkc-lab.com/sticky-shed/ ;
>
> We do see gooey deposits of shorter molecular weights than the
original binder -- but longer > chains than the typical lubricants. In
a filled matrix, I am led to believe that the shorter > molecules do
not recombine. Now what exactly happens is harder to determine. There
are many > factors going on here.
>
> One mental model that might work (according to some) is thinking of
the tape binder as a sponge. > The sponge is the cross-linked
polyethelene-polyurethane binder with the oxide carried in it. The >
holes in the sponge hold the lubricant. When the lubricant is thrown
into the blender before > coating, it doesn't really bond with the
binder chemistry, but is trapped in the matrix. One > theory has the
lubricant being pushed out momentarily under the pressure of contact.
>
> But, what happens to the shorter fragments during baking/incubation?
I don't know yet. Richardson > has stated that when he sent tape to an
analytical lab, they said they hadn't seen evidence of > hydrolysis. We
pooh-poohed that at the time, but if we look at a paper from 1984 that
Ric Bradshaw > did where he used the lubricant extraction to calibrate
the binder extraction, the results are > different from the 1982
Cuddihy and Bertram paper. Also, the typical lubricants that permeate
the > binder matrix would repel water.
>
> Remember, Bradshaw is the one who salvaged the Challenger tapes
after others said they were > non-salvageable.
>
> There's a 1000+ page book, "The Tribology and Mechanics of Magnetic
Storage Devices" 2nd edition > by Dr. Bharat Bhushan who is at Ohio
State University and is a former colleague of Bradshaw's at > IBM.
Bradshaw/Bhushan et al are the team behind LTO and it's proprietary
predecessor (3480) data > tape formulation. This has had an excellent
track record.
>
> I don't think (m)any media-centric tape manufacturers analyzed the
tape issues as closely as the > IBM lab. There is a paper at the IBM
Research Journal by Bradshaw that is a help.
> http://www.research.ibm.com/journal/rd/302/ibmrd3002H.pdf ;
>
> Another article that is of a bit of interest (with some minor
audio-related historical errors up > front) is
www.research.ibm.com/journal/rd/474/bradshaw.pdf and it provides the
history of data > tape.
>
> As I said, I'm learning about this and I don't have answers. I know
others who don't have answers > as well. The thought is methodical
measurements and lots of questioning and brainstorming will > help us
create a better picture.
>
> Imagine this scenario:
> Tape is made with proprietary formulations
> These formulations were well understood in terms of the then-current
state of the art
> The production lines have some variations
> The variations are now studied deeply and certainly not to the level
of today's polymer chemistry
> Today's scientists can only evaluate snapshotted degrading tape as
even NOS sealed
> tape is degrading
> We can't get back to what really new virgin tape looked like to
compare and we
> don't really know the formulations of the tape nor how these were
really
> applied/modified in production. Lots of production aspects can
modify chemical behaviour
>
> In some circles, including people who made the tapes, they were not
considered archival. 10-15 > years was a typical life expectancy for a
tape--at least in some circles. Have many of them done > better?Yes!
Absolutely! But is it harder to get high quality off aging tapes?Yes,
for some.
>
> Analog magnetic recording was a rather imperfect science that took
the world by storm. I think we > all have our work cut out for us. I
suspect we'll know more in a couple of years, including > whether it's
safe to freeze tapes to preserve them as is done with film and paper.
Yes, I know > what the standards say, but at this point it is necessary
to consider other options to what we're > doing. Remember when Corbis
bought out some of the NY Stock Photo Agencies (Black Star?)? Henry >
Wilhelm was behind the move to the Pennsylvania mine and freezing
conditions. Why? Even if they > had started digitizing the entire
collection right then, if the material had been kept under the >
then-current conditions some of it would be gone before its turn would
come up for digitization.
>
> Yes, I'm speculating, although I prefer to say formulating
hypothesis that need testing and > evaluation <smile>. I am also
standing on the shoulders of people who have/are researching this >
material. A lot of very good work has been done into arcane and minute
aspects of the tribology > and mechanics of magnetic media--at least
1000 pages of it IN SUMMARY! Connecting the dots is a > very hard part
of this.
>
> Some interesting snippets.
>
> A mixture of fatty acid ester lubricants that was a common lubricant
in tape freezes at about 20C.
>
> Other charts show the modulus of elasticity as a two-horned curve
with peaks around 0C and 20C.
>
> Pressure in the tape pack contributes to SSS severity (and other
items like pinning of the tape to > the backing below in
non-back-coated tapes). This varies throughout the wind.
>
> What we've been calling "Loss of Lubricant" that causes squealing
may not be, it may be a > flattening of the asperities (or peaks) of
the oxide of the tape increasing head-to-tape contact > area and
exacerbating stiction.
>
> Archivists want help predicting the lifetime of specific tapes. This
is an almost impossible task. > I know it sounds self-serving, but the
more I learn the more I really think that the "tape on the > shelf"
model is too high a risk and all tapes we care about should be migrated
to managed digital > stores within the next few decades. That is the
safest approach. Anything short of that is > gambling.
>
> I used to think SSS would be a non-issue and we could bake anytime,
but in the seven years I've > been doing this seriously, it seems the
required baking times are slowly increasing.
>
> Anyway, Tom, I wish I had simple answers for you and everyone on
this list. I think the best > answer to the problem is what you and I
are doing. We have to hope that once we create digitial > files, that
the clients' IT departments will preserve them along with the email and
the financial > records.
>
> I don't think that there is a foaming reaction, but one of the
chemists is on this list and > perhaps he has a more specific answer to
your question. The molecular weights of the molecules as > shown by
Fourier Transform Infrared Spectroscopy typically show degradation
products in roughly > the 5,000 g/mol region, with lubricants being in
the under 500 g/mol region and the binder being > in the 50,000 g/mol
region (I'm simplifying, but this is illustrative).
>
> I don't know if the behaviour of these 5,000 g/mol particles is well
understood during the baking > cycle. I also left my shorter message
appended to this thread, but snipped a bunch of the middle > stuff.
>
> Cheers,
>
> Richard
>
> At 06:28 PM 6/16/2006, Tom Fine wrote:
>>Another interesting point in this thread is the gentleman from
Norway saying that despite constant >>temp/very low humidity storage,
SSS rear its head reliably. Richard Hess has speculated and
>>researched a lot about this topic. As I understand it, it's not clear
that SSS is a purely >>ambient-humidity mechanism and may indeed have
nothing to do with moisture. I'd like to know, has >>anyone ever done
detailed analysis of the "goo" on a sticky tape and compared its makeup
to the >>binder material on unstuck or baked tape? I'd like to know if
this is some sort of gas reaction >>with some chemical in the binder,
leading to a foaming action, rather than having to do with H2O >>levels
in the air. Hey, I don't pretend to know chemistry beyond 10th grade
regents course, so >>please let me know if I'm speculatin' out my butt.
>
>>>>>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.
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