Steve:
As Eric mentions, long-term-low-humidity exposure will reduce "sticky shed".
It just takes a lot longer than "baking" and has some other side effects on
really bad tapes: if the tape is badly enough hydrolyzed that it has
"blooming" [actual "puddles" of oligomer residue] on the surface, it can
cause cross-linking of the oligomers without re-absorption into the binder
matrix. This can result in areas of hardened polymer on the surface of the
tape and, in the most severe cases, can "weld" wraps together. Note:
"blooming" is most common on 2" tape.
One of the benefits of low-humidity treatment (especially when combined with
temperature reduction) is that the primary vector of expansion and
contraction of magnetic tape with either humidity or temperature changes is
THICKNESS. Unfortunately, if you reduce humidity by "baking", the reduction
in tape thickness from the reduced humidity is off-set by the increase in
tape thickness caused by the raised temperature.
Because of this, low humidity treatment will shrink the thickness of the
tape and loosen the pack while it is also reducing the effects of "sticky
shed". When treating tapes with both fungus and sticky-shed for shorter
times (8-10 days), the slight reduction of the sticky-shed, along with the
loosening of the pack, can often result in a tape that can be slowly unwound
for cleaning. Once the majority of the fungus residue is removed, a tape
with bad sticky-shed can then be baked if needed for playback. The order of
treatment (heat, cold, low humidity, vacuum, dry wiping, wet wiping, etc.)
and the number of treatments depends on the specific condition of each tape.
As Eric also points out, the actual removal of the mold is another matter
and can present serious health hazards if not done under controlled
conditions.
Hey- no one said that restoring tape "the right way" is easy.
Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]
Tape restoration and disaster recovery since 1983
-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Steve Puntolillo
Sent: Tuesday, July 10, 2007 12:31 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] Moldy Tapes
Hi Peter --
Peter @ specsbros wrote:
> To drive the mold into dormancy, it is necessary to remove
> moisture from the mold, itself, and the tape. This can take
> up to 8 - 10 days of holding the tape in a controlled
> environment of around 30% RH. It can be done somewhat faster
> at lower RH and can take quite a lot more time if the RH is higher.
> (Note: baking is not recommended as, while it can sometimes
> work, it can also cause problems with moldy tape- depending
> on the type and amount of mold, baking can harden the
> mold-related residues and "bake" wraps together).
So, it sounds like you are recommending a low-humidity exposure at normal
temperature for several days followed by cleaning.
What if the tape also has a bad case of SSS? It seems as though you would be
stopped. You can't spool it to clean it because it has SSS and you can't
bake it to spool it because it has mold.
What do you recommend?
Thanks,
-- Steve
========================================================
Steve Puntolillo
Sonicraft A2DX Lab - Ultimate A_nalog 2 D_igital X_fers
http://www.sonicraft.com
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