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ARSCLIST  January 2008

ARSCLIST January 2008

Subject:

Re: Mould/Mold

From:

"Richard L. Hess" <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Wed, 23 Jan 2008 10:46:10 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (131 lines)

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 info.
>
>Just wondering if anyone else has had to deal with backcoated tape infested
>with mold severe enough to cause the backcoating and oxide layer to merge
>(seemingly) inseparably. I have been searching for info on what to do in
>this situation but have found nothing. Anyone have any ideas?

Hi, Steve,

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 of this:
  (a) A tape I received that was already wound through before I got it with
        the oxide half on the back-coating. Wouldn't even spool 
properly anymore
  (b) Moldy tapes that were damaged by unspooling (by me) prior to baking as
        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 horrid
        ripping sound on rewind (this was the first one I encountered) that WAS
        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, 
and dedicated
        old shop vac.
  (3) Open all outside doors (both roll-up ones and the rear personnel door).
  (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 with
        moist cloth to remove the mold (note: moist could be one of 
several fluids).
  (9) If tape needs baking, bake in mold-contaminated food dehydrator
  (10) Wind tape through "mold transport" against wiping pads, changing
         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 
for landfill
  (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.

Regards,

Richard




Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes. 

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