Re: [ARSCLIST] Ampex & Sticky Shed Syndrome

[James Lindner <jim@xxxxxxxxxxxxxxxxx>]

Actually I can remember a presentation at the AMIA conference (which was
then FAC/TAC) in New York where someone showed a videotape of cleaning EIAJ
tapes using ISO - and that had to be maybe 1990 or so. I didn't think much
of it then and I don't think much of it now - although I did experiment with
it way back. The issue really is that you can use a solvent - ISO is not
particularly good - I always found TriClor to be much gentler. If I wanted
to get tough Xylene provided industrial strength usually too strong and too
fast to get anything subtle done.

While I certainly say plenty of backcoat adhesion and breakdown of the back
coat - which after all is essentially binder applied without the particles
and in a much thinner coat - I certainly don't think there is any basis for
some of the statements in this patent.

You know - another way of removing the sticky shed syndrome is to remove the
oxide binder system side while you are removing the backcoat - that will
certainly solve the problem - and leave you with a nice clean piece of PET!
LOL

jim

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        Jim Lindner
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-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of Richard L. Hess
Sent: Monday, December 20, 2004 5:48 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Ampex & Sticky Shed Syndrome

At 10:15 AM 12/20/2004 -0500, James Lindner wrote:
>They received the patent on August 17, 1993. They have plenty of time. As
>for Richards comment suggesting prior art - I believe that one would have
to
>argue that the paper you suggested was in fact a public disclosure and that
>more then one year had lapsed from the time of that disclosure and the
>patent application. But they may have made a preliminary filing in which
>case they would probably be OK. Also I don't believe there is any rule in
>terms of disclosing ALL The research in any given field in a patent
>application - indeed I believe that one is required to disclose what other
>patents the invention may rely on.

Hi, Jim,

The prior art that I'm suggesting was published in the IEEE Transactions on
Magnetics, Vol MAG-18, No. 5, September 1982.

Patent 5,236,790 was filed on Mar. 31, 1989

George's comments were very interesting in that the Ampex patent would be
an improvement on the process where I suggest that changing the temperature
to shorten the processing time should be obvious to someone skilled in the
art from the Bertram/Cuddihy paper from 1982.

But now on to today's patent: Richardson's 6,797,072 for removal of
back-coating.

It makes some assumptions that we need to revisit as we've been told that
they are categorically wrong:

>Nearly every tape that has Backcoating has "Sticky Shed" problems
>to a varying degree. Thus, Applicant has concluded that the
>Backcoating is the bad actor in this situation. While Backcoating
>may have helped with some mechanical issues in the
>1960s, it left behind a chemical time bomb which is destroy-
>ing tapes today and will do more destruction in the future
>until and unless a process is used to solve the "Sticky Shed"
>problem.
...
>In the worst case situations, the
>sticking Backcoating would rip the Oxide off the base of the
>tape, thus completely destroying all the magnetic data on the
>tape.

Well, this is very interesting. This doesn't explain the tape from the
1960s and 1970s without backcoating that is losing its oxide at Cal State
Fullerton (CSF) due to high humidity storage. I certainly think the Bertram
paper addresses the issues.

Now, I can see how Richardson in US Patent 6,797,072 can make the above
claims as most of the tapes which suffer from sticky-shed are tapes that
are backcoated, CSF notwithstanding. I think the common thread here is that
there are now two binder systems--perhaps both using the same chemical
components--that are deteriorating. But my observations is that while the
backcoating may have degradations and is suffering from sticky shed,
usually the oxide is as well.

A very interesting read.

Also, Marie O'Connell discolsed her use of an isopropyl drip for playing
tapes to this list on 12 May 2003 which predates the filing of this patent
by four months. While it's not the same, I think the isopropyl drip while
hinted at in the Richardson patent is a separate invention and, I think,
clearly Marie's.

Cheers,

Richard