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Re: [ARSCLIST] Ampex 456 - tip of the iceberg...chemistry
Much of this research has been done by Joe Iraci et al at Canadian Conservation Institute. Include them in your plans
>>> tflists@xxxxxxxxxxxxxxxxxxx 6/16/2006 10:06 PM >>>
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.