Re: [ARSCLIST] Squealing Scotch 996

[Tom Fine <tflists@xxxxxxxxxxxxxxxxxxx>]

According to the list of 3M tapes:
http://recordist.com/ampex/docs/histgen/aorprod2.html

996 has a different binder type from know sticky-shed types (226, Classic
88x types). Is this problem present in more than one reel? What were the
storage conditions?

>From the reports I've seen on the Ampex list -- reports by reputable people
who more than likely understand what they're dealing with -- many types of
usually non-suspect tapes can develop sticky-shed-like symptoms under
extreme conditions. For instance, I'd state pretty strongly that Scotch 206
is immune to sticky-shed based on my experience with hundreds of reels
spanning from its introduction in 1969 until it was discontinued, but at
least a couple members of the Ampex list have encountered sticky 206. And, I
encountered a single reel of Scotch 208 -- out of a stack of several dozen
that had been in a warehouse and then an attic over a 20-year period -- that
was definitely sticky. 208 and 206 have the same binder and neither should
ever go sticky.

All of this leads me to speculate that many or all types of back-coated tape
can develop sticky symptoms, although the exact chemical nature of what's
happening to cause it may vary by type and situation (it could be several
completely different chemical processes, but the net result is the same -- 
squeaking or stalled/stopped tape motion and/or gummy residue on the guiding
path and/or heads). I've never heard of nor experienced any such symptoms
with non-back-coated tapes, but again this does not mean it's never happened
anywhere under any conditions. These tapes are allegedly prone to getting
brittle and having large-scale oxide shed, but again I've never seen that
with hundreds of old reels. I have, however, seen mold devour Scotch 211
that was in a damp basement. It was like a sci-fi movie: used isoprop wipe
on the mold and when it wiped off, there was only acetate backing with no
oxide about 1/8 down into the tape (ie half the width of the tape, from the
mold on the outside of the pack down), which had apparently been either
powderized or digested by the mold; actually, the same said mold also
dissolved part of the cardboard box. Good thing nothing priceless on the
reels! (NOTE: wear proper eye, nose, mouth and skin protective gear when
dealing with mold as some of it is very bad for human skin and respiration).

With almost every sticky tape I've encountered, baking it in my American
Harvest air-heat over solves the problem at least long enough to make a
transfer. One of the 3M veterans, either Del Eilers or Bill Lund, has said
that baking 12-14 hours and letting it cool 12-14 hours will solve the
problem long-term. I have encountered Ampex 406 that was so badly fused from
years of varying heat and cold and humidity (warehouse, then attic storage
conditions) that backing it just loosened it up so that unspooling it led
the oxide to rip the back-coat off the adjoining layer and still rendered it
unplayable. Luckily, none of those tapes contained any valuable content, so
they were unceremoniously tossed.

-- Tom Fine

----- Original Message ----- 
From: "Konrad Strauss" <konrad.strauss@xxxxxxxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxx>
Sent: Tuesday, November 08, 2005 5:45 PM
Subject: [ARSCLIST] Squealing Scotch 996


> I've just encountered a reel of Scotch 996 which is squealing. It does not
> seem to exhibit any symptoms of sticky shed - no buildup on the heads, and
I
> was under the impression that 996 did not suffer from stick shed.
>
> Any thoughts?
>
> -- 
> Konrad Strauss
> Director of Recording Arts
> Associate Professor of Music
> Indiana University School of Music
> http://php.indiana.edu/~kstrauss
> http://www.music.indiana.edu/department/audio/