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Kia ora Peter and all Thanks very much for this great read Peter. I too always read your posts! Great also to hear from Corey & Richard, always interesting. Have a good Easter! Marie On Thu, Apr 1, 2021 at 1:11 PM lists <[log in to unmask]> 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 > 973-777-5055 > [log in to unmask] > Audio and video restoration and re-mastering since 1983 >