Thanks for linking that Richard, that's a great find and a fun read. There's some really excellent seat-of-their-pants science and engineering in there.
Andrew R. Davis, Ph.D. | Chemist
Preservation Research and Testing Division, Library of Congress
101 Independence Ave. SE | Washington DC, 20540-4560 | U.S.
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From: Association for Recorded Sound Discussion List <[log in to unmask]> On Behalf Of Richard L. Hess
Sent: Thursday, April 01, 2021 2:43 PM
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Subject: Re: [ARSCLIST] Experimental use of vinegar on magnetic tape contaminated by oxidized aluminum reels
Congratulations on a job well done!
I was reminded of the story of the Challenger Magnesium Reels...
In looking for more information, I came across this somewhat poorly edited interview transcript of a presentation and interview of Ric Bradshaw at IBM about the recovery of the Challenger tape. There's a lot of information in this--more than I recall having seen before, but also a bunch of asides, which, in a way, makes it all the more interesting.
On 2021-03-31 8:08 p.m., lists wrote:
> Occasionally, when video (and audio) tape is exposed to extremely adverse conditions for a period of time, especially when the tape has fungus growth, the aluminum reel can oxidize. This primarily happens on the inside of the aluminum flanges where the flanges are in close proximity to the tape wrap. The result is pitting and bubbling of the aluminum flange surface. This pitting and bubbling leaves a very rough, raised surface with multiple sharp edges. Should the tape edge impact these raised, sharp areas during playback, it is very likely that the tape edge will be severely damaged.
> The easiest way to deal with this is to replace the oxidized flanges with other flanges before playback. If replacement flanges are not available, we have found that it is also possible to burnish the aluminum flanges so that the raised areas are removed and the inside of the flanges are smoothed. This leaves some of the pitting but, since the pitting is below the plane of the flange surface, it won’t endanger the tape edge during playback.
> Unfortunately, we recently encountered a tape with this problem that was so severe that “standard” treatment was insufficient. The oxidized aluminum residue had bubbled up so as to fill the gap between the inside of the flanges and the tape edge. Large amounts of the oxidized aluminum residue were deposited on, and hardened on, the actual tape. None of the chemical treatments and/or procedures developed over the last 38 years, to safely decontaminate magnetic tape, were successful in removing the hardened, oxidized, aluminum residue from the tape. Some of the patches of hardened residue were 3/8 of an inch in diameter, and had bonded a significant number of tape wraps together, making it impossible to wind the tape without tearing it in multiple places unless the residue could be removed.
> Research into alternate, possible solutions came up with two interesting facts. First, distilled white vinegar has been used to dissolve/treat oxidized aluminum. Second, distilled white vinegar has been used to stain treat polyester materials. With this information, we tried a number of tests. We treated an oxidized aluminum flange with vinegar and had some, but not complete, success in removing the residue from the flange. Then we treated a couple of pieces of (unrecorded and uncontaminated) magnetic tape with vinegar, wiped the vinegar off and examined the effects over a number of weeks. During the test period, we observed no (short term) damage to the magnetic tape from the vinegar. There was no observable discoloration, no binder-base adhesion failure and no increased shedding.
> We, finally, tried the vinegar on the hardened aluminum oxide debris on the tape and were able to remove it without (visible) damage to the tape. We don’t know if there may be any long term effects of the treatment but it was successful in removing the contaminant and allowing the tape to be spooled without ripping.
> This is a fairly esoteric problem and we hope no one else to deal with it. We have processed hundreds of thousands of tapes and only a few hundred have had seriously oxidized aluminum flanges. Of those, this is the first tape we had to remove large amounts of oxidized aluminum residue directly from the tape itself. If you do run into this problem, however, we found that vinegar did work.
> Peter Brothers
> SPECS BROS., LLC
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> Audio and video restoration and re-mastering since 1983
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
Track Format - Speed - Equalization - Azimuth - Noise Reduction Quality tape transfers -- even from hard-to-play tapes.