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Analogue Tape Preservation Archivist
Sound Archives/Nga Taonga Korero
PO Box 1531
Radio New Zealand House
Level 1, 51 Chester Street West
Phone +64 3 374 8443
Fax + 64 3 374 8448
>>> [log in to unmask] 24/01/2008 4:46 a.m. >>>
At 04:56 AM 2008-01-23, Steve Puntolillo wrote:
>Hi Marie --
>Thanks for bringing this up. I would also be very interested in this
>Just wondering if anyone else has had to deal with backcoated tape
>with mold severe enough to cause the backcoating and oxide layer to
>(seemingly) inseparably. I have been searching for info on what to do
>this situation but have found nothing. Anyone have any ideas?
I am not doubting that mold is a possible (probably) cause of
back-coating and mag-coating bonding to the point of significant
blocking/pinning and causing "pull-outs" of one (or the other or
both) of the coatings when unspooling.
HOWEVER, I have seen this condition in non-moldy tapes as well. It is
rare to be this bad, but it does happen. I have seen several instances
(a) A tape I received that was already wound through before I got it
the oxide half on the back-coating. Wouldn't even spool
(b) Moldy tapes that were damaged by unspooling (by me) prior to
the client knew the risk and, at that time, I didn't bake
first. This was only one
song of which he ended up finding a better copy.
(c) Non-back-coated tape (possibly 3M176) that had pinning and that
ripping sound on rewind (this was the first one I encountered)
corrected by a dry cold soak inside double plastic bags with
a silica gel desiccant.
(d) Similar to above, but not corrected with the same
treatment--this one was mostly
near the hub. Remember (c) and (d) were NOT back-coated.
(e) 3M201 pins on a regular basis, especially closer to the hub.
For this tape, 1.88 in/s
de-spooling seems to work. These tapes were stored in SE
Missouri in unknown
climatic conditions, but the area can be very hot and humid
in the summers.
The British Library under the direction of the late Peter Copeland
(formerly of this list) in circa 2001 (when I had the 3M176 issue)
described their "grandfather clock" which was a 1 RPM unspooler where
the tape was at the bottom of the cabinet, warm, dry air was blown
through the cabinet and the re-spooler was at the top. Peter reported
that they were experiencing trouble with triple-play tape and
developed this tool to help recover this.
Other discussions have talked about a separation "knife" to break the
coatings free of each other. The angles of everything in this
scenario are critical, and I suspect a "follower" would need to be
built that would go inside the reel and keep the angles the same.
Sounds like some of our disc playback friends might have some
suggestions for minimizing error here <smile>.
While I have little/no confirmation of this, I think that one of the
reasons (c) was successful was that there was enough
shrinkage/expansion to break the cross-wrap bonds at a microscopic
level without causing pullouts. Why (d) has not been successful is
anyone's guess. That tape is now in someone else's care as it fits
his mandate for gratis reformatting better than mine.
Dr. Ric Bradshaw (for many years, IBM's tape guru) has suggested that
it was no surprise that back-coated tapes exhibited the type of
pinning that you described, especially under the pressure of the
inner wraps on the reel. Since in at least some instances, the binder
chemistry for the back coat and the mag coat are similar, as the
polymers break down, under the pressure the material can migrate from
one to the other at least to the extent that they can become
inter-twined and cause the effect that you are describing.
As I said at the start, the mold could also act as an "adhesive"
between layers, but in a polyester tape, there are fewer nutrients, I
believe, in the tape for the mold than in an acetate tape.
Thanks, Marie, for the link to the Texas paper on mold. IPA has been
suggested by Peter Brothers as well, but as you especially know, too
much of it can be damaging.
My technique for removing mold is generally something like this:
(1) Don respirator -- not just a paper mask
(2) Go to garage where I have a winding machine, food dehydrator,
old shop vac.
(3) Open all outside doors (both roll-up ones and the rear personnel
(4) Check repirator
(5) Remove a tape from its box
(6) Bag any ancillary paper metadata for possibly sending to a
paper conservator later
(7) Inspect tape
(8) If it has noticeable mold in the windows, vacuum first then wipe
moist cloth to remove the mold (note: moist could be one of
(9) If tape needs baking, bake in mold-contaminated food dehydrator
(10) Wind tape through "mold transport" against wiping pads,
pads as needed
(11) Inspect tape for obvious signs of mold, if so, repeat (10)
(12) clean old reel if worth it (i.e. nice aluminum reel), replace
it if not worth it
(13) discard all paper and reels in outdoor garbage can - destined
(14) if baker was used, run w/o tape for a bit to make sure as much
mold as possible is out
(15) thoroughly wash hands/arms/face with soap and water
What fluid to use? I have used both IPA and a dilute chlorine bleach
solution. In all instances I inform my client that the mold removal
may have long-term bad effects on the tape and I will generally
digitize these tapes as best as I can at 96/24 assuming they will
never be played again. So far, I have not seen degradation from the
chlorine bleach and in reading some ancillary literature (not related
to tape) it has been said for some types of mold chlorine is a more
effective killer than IPA. I am conflicted on this and need more
information. The Texas paper tried IPA with acetate tape and noticed
some changes in the analysis spectra.
I hate cleaning moldy tapes and ones as bad as Steve describes should
be considered close to terminal.
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information:
Quality tape transfers -- even from hard-to-play tapes.