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ARSCLIST  December 2016

ARSCLIST December 2016

Subject:

Re: Baking Tapes and Beyond

From:

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

Reply-To:

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

Date:

Thu, 8 Dec 2016 00:07:03 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (197 lines)

On 12/7/2016 22:08, Matt Sohn wrote:
> Richard Hess quoted Peter Copeland:
>
> "Sometimes the binder has oozed so much that it sticks the oxide onto
> the back of the next layer, and of course the oxide comes off and you
> lose the recording. This would have happened even if you had tried a
> straight playback. The only cure I know is to run from one reel to
> another very slowly and at extremely high tension. The layers then
> separate slowly and tangentially without damage to the oxide; but you
> will need a specially-modified tape deck with servo control of
> slowly-rotating spooling motors, and it may take a day or two for one
> reel to unwind. Do this in a warm room to allow some of the stickiness
> to dry immediately. We have a prototype machine (called “the Grandfather
> Clock”), which supplies warm air to dry a few feet of tape as it crawls
> from one reel to the other."
>
> I ask:
> So in the case of a delaminating reel, if I was going to use the
> 'Grandfather clock' method, would I want the tape to be humidified, or
> un-humidified?
> I ask because when I was at the Louis Armstrong archive, I had one
> acetate tape that delaminated near the end of the reel. I lost several
> feet of oxide before I stopped the machine, and took the reel off the
> player. I read about the GFC at the time, and as I recall, one
> recommendation was to humidify the tape by placing it in a humid
> environment (we used a plastic garbage can with some water in it and a
> platform to suspend the reel of tape) for a period of weeks or months. I
> think I left the tape there for six weeks or so, and when I tried to
> play it I got the same delamination. I didn't get a chance to try slow
> unwinding, and the tape remains unfinished as far as I know. I would
> assume that the more supple the oxide layer was, the more likely it
> would be to adhere to the backing.
>

First, I would like to contribute Peter Copeland's further explanation
in an ARSCLIST posting to me on on 2001-04-20

"> Dear All, Here at the British Library National Sound Archive we have
found a total of six double-play and triple-play Agfa tapes showing
similar symptoms. The oxide adheres to the backing of the next layer,
which in this case is glossy (not matt). At normal playing-speeds (7 1/2
ips) the oxide is completely wrecked in the process, and the tape
ruined. Neighbouring tapes in the same collections are usually OK, it
afflicts (I would guess) one tape in five hundred. We are currently
using outhoused contractors to get the sound off such tapes for
print-through reasons. The contractors are all mandated to unpeel the
outer turn of the tape very slowly, and if the oxide shows signs of
coming off, return them to us unplayed.

You cannot bake such a tape; as Richard Hess says, it's different from
the usual synthetic polyurethane binder problem. Following an accidental
discovery on my part, the solution seems to unwind the tape incredibly
slowly. I understand that what we call "Sellotape" here in England is
conversationally called "Scotch Tape" in America. If you pull some
Scotch Tape from the reel fast, it goes "pzzzzip" as it separates, while
if you pull it slowly it separates cleanly. We have built a prototype
machine (called a "Grandfather Clock", because that's what it looks
like) to unwind the tape incredibly slowly. The gearbox ratio can be
changed, but at the moment the takeup reel turns at one revolution a
minute, so a reel may take three days to unwind. As this happens, it
travels up the grandfather clock through a box fed with warm air from a
fan to dry it before it reaches the takeup reel. But until last week, we
hadn't enough examples of such tapes to test the machine thoroughly.

I hope to present the resulting design at the ARSC/IASA conference in
London in September.

Peter Copeland"

On 2003-02-27, Nigel Bewley wrote on ARSCLIST, quoting Matt Sohn:

"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.


[Nigel Bewley:]
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."

[Back to Richard]

I think that's the best picture of the GC we'll get.

The question I have in my mind is what is the "drying" that is being
done. My sense is that the tapes were put away damp, but perhaps it was
absorbed from the air as well. I don't think it was a washing process,
though Ric Bradshaw did a washing project on the reels of tape from The
Challenger to get various salts of corrosion off them. I have washed
cassette tapes to remove coffee spills, but...while it worked, the
client wasn't interested in paying for the effort.

I have also recovered a very damp cassette from a time capsule....but it
could have been worse.

I don't know if any intentional further wetting is a good idea for these
tapes that are adhered to each other by some unknown cause. If you know
there is dirt, coffee, or salts of corrosion then yes, water can
dissolve those, but we don't know why the adhesion is occurring in the
BL case nor in yours, right?

So I think adding more water to an already damp/hydroscopic system is
not going to be a recipe for success...just my gut reaction.

I have moistened a dried out carbonyl iron tape from the 1930s and it
turned from a carpenters tape measure into a satin ribbon and still had
strength. I tried it with an already distressed tape and it made it more
distressed. The difference was the CI tape had just dried out, the other
tape wsa distressed by being stored next to a wood stove for a Vermont
winter! I also think edges were welded, though it took me some time to
confirm that as it was only at a few points...per revolution.

We need to separate the discussion of this type of pulling-apart of the
mag coat and the base coat by adjacent-wrap adhesion from mag coat
FALLING OFF which is what I understand is happening with 206 and a few
tapes I've seen. There was no pulling off, just chunks falling off from
what I saw on the reel of Concert (and one other) tape.

I know this doesn't help, but I'm trying to save time of re-pursuing
already pursued dead ends.

Good luck!

Cheers,
Richard



--
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.

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