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ARSCLIST  January 2016

ARSCLIST January 2016

Subject:

Re: One more sticky-shed data point - Richardson treated tape

From:

Tom Fine <[log in to unmask]>

Reply-To:

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

Date:

Fri, 22 Jan 2016 15:05:42 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (113 lines)

This is very informative and helpful, Peter. Thank you.

If funding comes through, I may get a chance to digitize a large library of Ampex back-coated tapes 
that have been long-term stored cold/dry. It will be interesting to see what the sticky-shed 
situation is, how much baking time if any is required, and I will make it a point to test tapes 
baked early in the project at the end of the project and see if low-humiditiy/low-temp storage has 
kept them un-sticky for XX months or years the project takes.

-- Tom Fine

----- Original Message ----- 
From: "lists" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, January 22, 2016 12:05 PM
Subject: Re: [ARSCLIST] One more sticky-shed data point - Richardson treated tape


> Tom:
>
> One answer to your question below was in my earlier posts.  The short chain
> polymers in the backcoat are more subject to hydrolysis than the long-chain
> polymers in the recording surface.  In addition, once hydrolyzed, the
> oligomer residue formed is more hydrophilic than the polymer matrix and
> allow the tape to retain more moisture, inducing more hydrolysis.  One thing
> that may not have been clear: it takes a longer exposure to high humidity
> conditions, and higher humidity conditions over all, to hydrolyze the
> long-chain polymers.  There are humidity conditions where short-chain
> polymers will hydrolyze and long-chain polymers won't.  There are
> short-chain  and medium-chain polymers in the recording surface but many
> fewer than in the backcoat due to quality control when the polyester matrix
> is created for the recording surface.  Some of the recording surface may
> hydrolyze but not to the extent that it interferes with playback.
>
> So, in answer to Richard's comments (didn't read till this post till after
> my initial response here), there is a threshold at which hydrolysis will
> occur and it is different for long, medium and short-chain polymers.  Also,
> remember, hydrolysis is a bi-directional chemical reaction.  Not only is
> there a threshold at which hydrolysis will occur, there is also a threshold
> at which hydrolysis will run in the other direction and the oligomers will
> cross-link back into polymers.  Testing has been done but the threshold is
> dependent on the length of the polymers, the RH, the absolute humidity and
> the temperature.  There are too many variables to give a "threshold" for
> tape in general.
>
> Another post by Tom- no, the Richardson-treated tape may well not go
> "sticky" eventually, depending on the ongoing storage conditions (or it
> might if the humidity is too high).  Some of the recording surface may
> hydrolyze but, the greater concentration of long-chain polymers in the
> recording surface that don't hydrolyze under "reasonably" low humidity
> conditions , may not result in a "sticky" effect.  In International
> standards (and laboratory testing), the hydrolysis issue is addressed, not
> by if some of the binder hydrolyzes, but if sufficient hydrolysis residue is
> present at any given time to interfere with playback.   As extreme examples:
> if you store your tapes in 90% RH at 85 degrees, the tapes are very likely
> to get "sticky" whether you have removed the backcoat or not.  Again, if you
> store your tapes at 20% RH at 60 degrees, the tapes are unlikely to get
> sticky whether you have removed the backcoat or not.  I don't know of
> specific data about a set point of RH/temperature/ absolute humidity to
> differentiate between when a backcoated and non-backcoated tape is likely to
> produce enough oligomer residue to become "sticky".  There are factors
> concerning the exact mix of long-chain/medium-chain/short-chain polymers in
> the binder, whether any of the binder has already hydrolyzed before storage
> at the "set point" and the tolerances of the playback machinery.  To make
> matters more complicated, there are conditions where some of the polymers in
> the binder are undergoing hydrolytic breakdown while, simultaneously,
> oligomers in the binder are cross-linking back into polymers- messy for
> calculations.
>
> Peter
>
> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:[log in to unmask]] On Behalf Of Tom Fine
> Sent: Thursday, January 21, 2016 7:55 PM
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] One more sticky-shed data point - Richardson treated
> tape
>
> Hi John:
>
> I'm pretty sure Peter is aware of Richardson's work, but for those who
> haven't dove deep into the weeds of tape degradation and playback ...
>
> Charlie Richardson has developed a proprietary process, which he has not
> described in detail or provided any public photos or videos of, which
> removes the back-coat from sticky tapes. My assumption is that it involves
> some sort of solvent and perhaps a scrubbing device that doesn't seem to
> harm the oxide surface. He has claimed he does not first bake the tapes,
> that he has a method where the tape will unspool and the back-coat is then
> removed. Not having any evidence either way, I'll believe his claims until
> proven otherwise.
>
> A couple of years ago, I asked him to use his method to un-stick an old
> Ampex test tape I had that I knew was sticky, based on attempted unspooling
> of stuck tape at the beginning of the reel, and the fact that the look, feel
> and smell of the tape was clearly Ampex 406 type. He sent me back the tape,
> back-coat removed, and indeed it did playback with no problems. He asked to
> keep the tape to perform "further tests and treatments," but I declined,
> wishing to keep it under normal NY room-atmosphere conditions and seeing if
> it went sticky again. So far, it has not. I will keep trying it out every
> 12 months or so and reporting back. When I started this thread some time
> ago, my point was to say, this treatment did not render the tape unplayable
> (as I feared it might), and it has kept the tape playable and
> non-residue-creating for the past 2+ years. And this once again circles back
> to one of my main questions -- if sticky shed is due to problems with the
> binder, then why would removing the back-coat seem to first of all make a
> tape un-sticky and second keep it un-sticky for a long period of time, if
> not permanently?
>
> -- Tom Fine
>
> 

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