Hi Richard,
Many thanks for your very helpful clarifications on Davis's work. It's obvious to me that the article I linked is very limited as far as explaining the scope of his work and how it goes beyond what's been previously done. From that article, the reader would have no idea that much of anything had been previously done, as far as real research, which is certainly not Dr. Davis's fault.
As far as the mistakes in the article that I alluded to, here are the issues I have:
-Bing Crosby would not have had any views on the sound of vinyl records in 1947. The vinyl LP was introduced the next year, and I'm sure that the article was not alluding to the handful of vinylite 78s that had been issued after the war (Crosby was an American Decca artist and I don't know whether or not they made any vinylite 78s). I have a feeling that what the author was really referring to were 16-inch lacquer transcription discs that had been used to record radio programs. Granted, vinyl pressings were sometimes made from these discs for circulation to various broadcasting outlets - at the very least, the statement about Crosby's alleged dissatisfaction with "vinyl records" requires some clarification.
-The article quotes Davis as mentioning "toaster ovens" as one of the methods used for restoring sticky-shed tapes. Surely he meant convection ovens. After all, we're talking about baking tapes, not broiling them. I hate to think what might happen to a tape in a toaster oven, with a red-hot heating element just inches from the reel, and no fan to circulate the heat.
-I would really appreciate your thoughts on this one: It seems to me that Charles Richardson's greatest contribution was in nailing down the real cause of this problem. Specifically, that it's related to the binder that holds the back coating to the tape and not the oxide. According to Richardson, only back-coated tapes have this problem and, however one might view his solution, which is stripping the back coating off of the tape, it apparently does fix the problem permanently. If the problem was in the binder holding the oxide to the tape, removing the back coating would not permanently correct the problem. The article does mention back coating, but not as the cause of the vast majority of sticky-shed problems. Are there non-back coated tapes that suffer from this problem? If there are, they must be a relatively small minority of the total number of sticky-shed tapes. Again, please correct any misunderstandings I might have on this issue.
-The article makes no mention of the scientifically-correct description of the problem, which is binder hydrolysis. Sticky-shed syndrome is the more colloquial name for it, and I'm surprised that an article posted on a scientific web site would avoid calling it by its technically correct name.
In sticky-shed tapes I've baked, mostly Ampex 456 and 406, I've consistently observed the following: after baking the tapes leave thin, dry, black strands on the tape guides when the tape is wound back and forth. Is this consistent with Dr. Davis's finding that baking causes the residues to melt back into the bulk polymer layer? I really don’t know the answer to this question, but on the face of it, it appears that baking dries the moisture out of the binder that had oozed out to the edges of the tapes, leaving the dried, black strands that are separated from the tape by the tape guides on the transport. Davis implies that tight winding the tape squeezes the moisture-laden binder out to the edges of the tape. That I can believe.
Incidentally, there's no mystery to the chemistry behind Richardson's method for removing the back coating from tapes. As his patent states, it's just alcohol. I don’t know how many of you may have tried this: Dip a Q-tip into a bottle of isopropyl alcohol and then rub it on the back coating. The back coating comes right off (importantly, the "business side" of the tape is unharmed).
So, I do not mean to disparage Dr. Davis's work, which was not given an adequate overview by that article. However, I do have a problem with "toaster oven," if indeed that's what he really said.
Best,
Gary
-----Original Message-----
From: Association for Recorded Sound Discussion List <[log in to unmask]> On Behalf Of Richard L. Hess
Sent: Saturday, April 11, 2020 1:22 PM
To: [log in to unmask]
Subject: [EXTERNAL] [ARSCLIST] Recent musings on Dr. Andrew Davis's research paper
Hi, All,
I am not trying to pick any fights but I feel I must speak up concerning the work that Dr. Andrew Davis of the Library of Congress is doing.
I spent a substantial amount of time talking to Dr. Davis, including spending time with him during several lunches at LoC Culpeper during the
2018 AES Audio Archiving conference.
Andrew's slide deck is linked from the article:
<https://www.morressier.com/article/towards-understanding-thermal-remediation-degraded-archival-reeltoreel-audio-tapes/5e736c6bcde2b641284abb13?>
ICYMI
One of the things that we must understand is that there are different levels of "knowing." I've transferred enough philosophy/theology tapes addressing this subject to know I don't know about knowing and probably never will know.
However, I can offer some general thoughts on what Dr. Davis and his colleagues are trying to do.
He says in his slide deck that thermal treatment (baking) of tapes is widely used but not well understood. Here's that nasty "knowing" thing.
We all know it works, and I keep a web page semi-current with things we think we know about specific tapes.
<http://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/degrading-tapes/>
Note that the title of Dr. Davis's paper is "Towards understanding the thermal remediation of degraded archival reel-to-reel audio tapes."
TOWARDS the UNDERSTANDING ... there's that knowing thing again.
i've heard it from many people whom I respect, including Dr. Ric Bradshaw, retired lead chemist at IBM tapes, that we have never fully explained how "baking" works, he knows it works, we know it works, but he suspects that Cuddihy's explanations in his papers are convenient and wrong.
For starters, there is the implication (if not outright stated) thought that the degradation process is a reversible chemical reaction with the tape going back to the way it was. Bradshaw's opinion--and I believe other research has backed this up--is that it is not a fully reversible process. The clue here is that the molecular weight of the binder molecules after baking is lower than that of the un-damaged tape...although the procurement of samples in various conditions is difficult today. In other words, baking causes shorter chains to be made, not the long chains originally intended.
What Dr. Davis has attempted to do is go back to basic analytical techniques--techniques that were only available in rudimentary forms when Dr. Cuddihy and Dr. Bertram did their research for NASA's Jet Propulsion Laboratory. I believe that the instrumentation tapes used in those studies had a thinner mag coating than standard audio tapes which may further confound their results as compared to audio tapes.
I'm afraid that the last slide in Dr. Davis's presentation may be his interpretation of my voiced desire to end up with a "pool test kit" that can use a sacrificial end cut of a tape to determine the ideal remediation technique for the specific tape at hand.
Dr. Thiebout working at the PrestoSpace project a decade and a half ago was the first person I was aware of to apply Fourier Transform Infrared Spectroscopy (FTIR) to identifying tape mag coating "signatures." He also used mass-spectrometer techniques. Neither of these tools fit the description of pool-test kit for cost or ease of use. Dr. Davis's first attempt was to propose the water-droplet method which Mike Rivers has substantially used and evaluated and I have evaluated on a small scale.
Personally, I find its results too difficult to interpret. I might get better with it, but, honestly, I found the technique frustrating (thanks to Mike for supplying me with the micro pipettes needed to undertake the tests).
As to Dr. Davis not being familiar with the current research and standards, he has read my Fall 2008 (Vol.39, No. 2) paper "Tape Degradation Factors and Challenges in Predicting Tape Life."
Dr. Davis quotes the claims of the Ampex "Baking" patent in his slide deck.
The challenge with the Ampex patent is it is a PROCESS patent. A recipe for solving a problem. There is no science in it (and in my interviews with retired Ampex employees prior to publishing my 2008 ARSC paper, I found no distinct evidence of any science better than the flawed Cuddihy papers).
<https://www.richardhess.com/tape/history/HESS_Tape_Degradation_ARSC_Journal_39-2.pdf>
There is a desire among some researchers today to do research published in peer-reviewed journals (as opposed to trade magazines) to leave a strong foundation for future generations of tape restorers to draw upon.
Unfortunately to do that "right" many basic steps which have never been documented (and therefore we can assume have never been fully understood nor explained in a permanent form) must be reported on.
If people think there are papers that fully explain what is happening with degrading tapes at the polymer chemical level I think Dr. Davis, and I know I, would appreciate seeing them.
One of the young researchers who is very enthusiastic about audio tape restoration, Dr. Federica Bressan, put together a group of people including me and two Ph.D. chemists from the University of Padua to write an overview paper. Drs. Bertani and Sgarbossa contributed the deep dive chemical portion that went into the heart of the matter. Dr.
Bressan and I provided the practical "wrapper" for the science techniques. The paper is "Chemistry for Audio Heritage Preservation: A Review of Analytical Techniques for Audio Magnetic Tapes"
Heritage 2019, 2, 1551–1587; doi:10.3390/heritage2020097
https://www.mdpi.com/2571-9408/2/2/97
On page 1565 (don't worry, it's only 37 pages long), our paper discusses "Binder degradation" (Section 3.2).
On page 1567, our paper discusses "Stability of Magnetic Material"
(Section 3.3). This phenomenon has not been widely researched in the tape context, at least to the best of our knowledge.
We attempted to create a useful bibliography of existing work and the paper includes 125 references, spanning over five of its 37 pages.
Both of these papers are freely available to anyone.
One final thought. There has been past criticism in this (and other) fora about new researchers publishing what appears to be "dead-end"
research. One of the reasons they undertook this research was that it had not been previously published, so there was no way for them to determine that it would result in a "dead end." Publishing even "failed"
research (in the sense that it failed to deliver a hoped-for result) is, in itself, useful so other researchers know what to avoid, or the "failed" research might stimulate an insight in a future researcher who might go on to solve the problem, avoiding the pitfalls that caused the "failure" in the earlier research.
I am not suggesting that Dr. Davis's research is "failed" in any way, but it is one of those building blocks that he or others can build on.
For example, I find Dr. Davis's graph on page 14 of the slide deck most interesting. It is showing that "baking" is causing a phase change within the tape on the first pass. I think fully understanding that might lead to something very interesting. I did discuss an earlier version of this research with Dr. Davis and suggested that isolating that 55 °C blip to the mag coating, base film, or back coating might be useful. I don't know if he has done that yet. I've also suggested re-running the test at multiple times post-initial-baking to see if the
55 °C blip begins to reappear after time.
As an aside, I don't think that the article about Dr. Davis's research does it any favors, and I don't think the recent article about the work I did back in 2011 on the same website did much justice to that.
<https://phys.org/news/2020-01-pre-eruption-seismograms-recovered-mount-st.html>
I am identified in that one as "a Canadian audio recording professional," which is true, but a name mention would have been nice.
Perhaps these recent articles on the website are the result of the lack of face-to-face collaboration and an inexperienced new hire. I'd like to leave the benefit of the doubt as we struggle with our new reality of living.
I would also like to suggest that none other than Jay McKnight and a few other ex-Ampex people still do not think there is a proper physics explanation for how high-frequency bias works. He and Dr. Neil Bertram have been working on some papers over the last few years to better explain this "known" phenomenon.
Thank you for reading and thank you in advance for any comments you might make. Please stay safe everyone.
Cheers,
Richard
--
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm
Track Format - Speed - Equalization - Azimuth - Noise Reduction Quality tape transfers -- even from hard-to-play tapes.
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