[ARSCLIST] Peeling acetate tape

["Bewley, Nigel" <Nigel.Bewley@xxxxx>]

Matt Sohn wrote:
I have run across a couple of tapes in our collection where the wraps near
the center hub are stuck together. as the reel unwinds, the oxide is peeling
off. The majority of the reel is ok, but the problem appears on the last
These are acetate tapes from the early 50's (the most recent one I have run
across is Orradio Irish brand "professional grade" No. 211). Is there any
way to remedy this condition? Any advice would be appreciated.


We too have the occasional problem with sticky tape.  We have been
reasonably lucky with our tape collections so far and have unearthed
relatively few problem reels.  For the most part these are dealt with by
baking in the usual manner.  We have had one or two that exhibit
particularly bad stickiness and these have been triple play Agfa stock.  (We
have a programme of live theatre recording; before we adopted DAT as a
location recording tool in 1989/1990 we recorded on a NAGRA tape machine at
7.5ips and in order to get the duration required for theatre recordings we
used double or triple play stock).  A few of those triple play reels have
become very sticky and we have developed the 'Grandfather Clock' to deal
specifically with these. I think that the stickiness in this particular Agfa
tape stock is a batch problem rather than across the board.  In fact we have
run out of sticky tape to keep the GC employed!  The GC was conceived and
developed by my predecessor Peter Copeland and our design/maintenance/repair
engineer Hugh Mash.  The GC is in fact still in development and one or two
refinements are being considered, but it essentially is up and running and
can best be described as a working prototype.  The GC stands about six foot
high, is about two foot wide and is supported by a flat plate thus forming a
stand.  The six foot by two foot monolith is made of plywood or similar
sheet material painted a tasteful matt black.  At the top of the GC there is
a spool motor, centrally mounted on the back of the sheet.  On the front of
the GC is the motor's spindle which can accommodate any standard size reel
(as with a pro tape machine).  The motor is geared to run at one revolution
per minute.  At the bottom of the GC is an inert spool spindle - by this I
mean it spins freely and is not powered by a spool motor.  This spindle too
can accommodate any standard size reel.   The spindle at the top of the GC
is for the take up reel and the spindle at the bottom is for the supply reel
- the sticky tape, in other words.

The Grandfather Clock is so named because at face on it resembles one,
especially when a NAB reel is in place on the take up spindle (the 'clock
face')!

The sticky reel is put on the bottom spindle and laced up to the take up
reel at the top of the GC.  There are no tape guides.  The tape path is
circa five feet long and passes through a perforated perspex box which is
about ten inches by five inches and two inches deep.  This is mounted on the
front of the GC, off centre and about half way up.  The tape is laced
through this box.  At the back of this box is a low powered warm air blower
which fills the 'hot box' with a gentle current of air.  We can control the
temperature of the air from room temperature to around 50 degrees Celcius.
The tape moves slowly through the hot box, is dried and so treated for its
stickiness.  The take up reel moves so slowly that the adhering layers are
peeled gently apart without the oxide being separated from the backing and
so damaging the recording.

The modifications that we have in mind are to make a bigger hot box so that
the tape is in contact with the warm air for longer and to add a
'anti-judder' control.  This will be an arm resting against the tape as it
comes off the supply reel.  The amount of pressure will be variable, and it
will be very small anyway, and this arm will absorb or otherwise iron out
the tendency for the tape to judder as the layers peel off.

We plan to take some photographs of the Grandfather Clock (a picture tells a
thousand words) and get these off by e-mail to interested parties.

Regards
Nigel Bewley
British Library Sound Archive
(eagle eyed readers will observe that we have officially dropped the word
'National').



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