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
>