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Re: [ARSCLIST] Fwd: Sticky AGFA PEM 469
Charles:
While working on the AES and ANSI technical commissions on magnetic tape
stability, we reviewed large numbers of documents from both private and
government labs from around the world (US, Canada, Japan, Germany ..., 3m,
Agfa, Sony...) and we were never able to locate any repeatable laboratory
testing that proved a signal deterioration associated with multiple baking
of a tape. There were anecdotal reports of such but no laboratory testing
to back up the anecdotes. If you actually have quantifiable laboratory
results to back up a loss of signal that can be specifically attributed to
baking of a tape (and contains sufficient controls in the testing protocols
to isolate the baking as the cause), I would love to see the results of the
testing. As I said, we looked for such a study and were never able to
locate one. We found lots of other interesting results but not this one, in
specific.
Peter Brothers
SPECS BROS., LLC
973-777-5055
peter@xxxxxxxxxxxxx
Tape restoration and disaster recovery since 1983
-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of Charles A. Richardson
Sent: Saturday, April 05, 2008 10:27 AM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Fwd: Sticky AGFA PEM 469
Dear Tom: What Claus describes with Ampex sticky tapes is exactly my
experience -- they go sticky again after about 30 days. What Claus
did not touch on but has definitely been my experience is that there
is audible deterioration after two or three bakings. Treble dropoff,
fuzzy upper midrange, the kind of stuff you hear in multi-track if
it's been run thru too many times for endless punch -ins.
I have spent the last 10 years researching the causes of such tape
problems. My own research, as well as the research of a well-regarded
forensic chemical laboratory which I engaged to find and explain these
complex chemical issues, confirms that the new remediation method that
I devised is very effective and restores the tape to excellent sonic
and mechanical performance. Although my research continued and
provides more information today, the paper I presented at AES in 2006
in San Francisco provides an explanation and drawings for both these
mysteries, namely why the tape becomes sticky again after baking, and
why sticky tapes have increasing high frequency losses and drop outs.
If you contact me off list, I would be glad to send you a copy of my
paper (and a newer follow-up paper) for your review and comment. In
addition I am working on new papers (and a prototype machine to
mechanize my process) which will soon be released.
Charles A. Richardson
Richardson Magnetic Tape Restoration
1938 Baltimore Annapolis Boulevard
Annapolis, MD 21409--6248
410-757-3733
On Apr 2, 2008, at 8:20 PM, Tom Fine wrote:
> Hi Goran:
>
> Thanks for digging these posts up.
>
> What Claus describes with Ampex sticky tapes is exactly my
> experience -- they go sticky again after about 30 days. What Claus
> did not touch on but has definitely been my experience is that there
> is audible deterioration after two or three bakings. Treble dropoff,
> fuzzy upper midrange, the kind of stuff you hear in a multi-track if
> it's been run thru too many times for endless punch-ins.
>
> I have also had experience with some Ampex tapes so badly stuck
> together that even baking would not make them un-spool correctly.
> The oxide would be "glued" to the back-coat of the layer ahead of it
> and thus would rip the back-coat off and end up an unplayable mess.
> This was with tapes that had been under extreme storage conditions
> (basements, attics, garages).
>
> As for 3M, I can say that Scotch 226 and 227 reels I've had the
> misfortune of dealing with behave pretty much like Ampex tapes. I've
> never seen this white film discussed in the old posts, just typical
> sticky-shed that is temporarily cured by baking. However, with 1-mil
> Scotch 227, I had to bake 18 hours and let cool 18 hours to make one
> pair of 3600' reels fully playable with no shedding. These
> particular reels happened to go back sticky within 2 weeks, because
> I tried to make another go at part of one and ended up with quickly
> discovering it was sticking and needed another baking. Luckily, the
> second pass worked great and those reels were disposed of later on.
>
> I have a bunch of Agfa PEM 468 1/2" reels recently given to me. I
> will report back if I run into any troubles. The two I've played so
> far are just fine, and one was literally in a basement closet for at
> least a decade.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "Goran Finnberg" <mastering@xxxxxxxxx
> >
> To: <ARSCLIST@xxxxxxxxxxxxxxxx>
> Sent: Wednesday, April 02, 2008 11:11 AM
> Subject: Re: [ARSCLIST] Fwd: Sticky AGFA PEM 469
>
>
>> Peter Brothers:
>>
>>
>>> The microwave process is called the XT process. It is patented,
>>
>> That´s correct.
>>
>> I have saved this from the ARSC list in 2004 that gave some more
>> information coming directly from Terry O´Kelly of BASF:
>>
>> -----------------------------------------
>>
>>>>> ctrelby@xxxxxxxxxxxxxxx 9/28/2004 5:06:38 PM >>>
>>
>> Hi John,
>>
>> Welcome to the 70's tape pit. I'm sure you have heard about sticky-
>> shed
>> syndrome etc.
>>
>> Environmental law changes forced most tape manufactures to change the
>> formula of their binder in the early 70's. This has left us with
>> resulting
>> sticky-shed and other artifacts. Scotch/3M I have found not to
>> exhibit
>> sticky-shed unless it was stored VERY poorly, but* A fine white
>> powder
>> will
>> in many cases be released and distribute itself on the tape path and
>> heads.
>> It is very hard to see, and in many cases you have to look at the
>> erase
>> head
>> (it's black) to see this. The powder is fine enough that it will
>> slowly
>> deteriorate the Hi frequency play-back response during a pass.
>> The baking of tapes is not a fix-all solution. It was specifically
>> developed
>> by a group of engineers from Ampex to solve the sticky-shed issues.
>> AGFA
>> developed their own solution to the same problem. (I'll include an
>> email
>> from a BASF engineer to our Video Director at the end of this
>> posting).
>> No
>> such study was done by Scotch/3M to my knowledge but I have found
>> that a
>> pass or two on a pellon based cleaning machine with light tension
>> will
>> clear
>> off the powder and render the tape playable. This process can also be
>> done
>> by hand if you are very careful.
>>
>> I know this doesn't answer your question about TDK, but I have not
>> encountered tapes from the 70's from TDK, and have no direct solution
>> for
>> you. It sounds like and cleaning pass is in order for you, BUT
>> PROCEED
>> WITH
>> CAUTION, and test on lengths of tape with no audio, since you might
>> damage
>> the tape in trying to find your solution.
>>
>> The following excerpt is from and email from Terry O'Kelly,
>> formerly of
>> BASF
>> to Pat Shevlin, Xepa Digital. (130 @ 8hrs refers to 10.5" dia, 2"
>> tape -
>> I
>> would still suggest this process is done by engineers with
>> experience to
>> assure a successful result)*
>>
>> ...
>>
>>
>> "I do have good records of the Agfa XT process and the AMPEX
>> process for
>> driving water molecules out of the polyurethane binder. Agfa used a
>> microwave, but the oven had to be so carefully controlled over a
>> short
>> period of time that it was not generally recommended for users.
>> IDT in
>> West
>> Palm Beach licensed the Afga method, but I don't know if they are
>> still
>> around.
>>
>> The Ampex method used a convection oven with an internal fan that
>> moved
>> heated air around the tape. The tape was slowly brought to a
>> temperature of
>> 130 degrees F. for a period of about 8 hours. Plastic reels could be
>> used,
>> but it was better to have transferred the tape to a metal reel. The
>> transfer process itself helps to redistribute tension in the tape
>> pack
>> to
>> make it more uniform. More than one tape required a spacer such as
>> an
>> empty
>> metal reel. Once the tapes had cooled to the touch, they were good
>> for
>> about 30 days; but copying the data as soon as possible was
>> safest. The
>> binder would begin to absorb water again after 30 days, but the
>> linking
>> structure of the binder would be damaged enough that a second
>> baking may
>> not
>> have prevented the oxide/binder combination from delaminating or
>> rubbing
>> off
>> altogether.
>>
>> The goals of both the Ampex and Agfa methods were the same: drive the
>> water
>> molecules out. The XT process was faster but more difficult
>> without a
>> very
>> controlled environment. The Ampex process was slower but easy to
>> follow
>> for
>> most people."
>>
>> ...
>>
>> I hope you find this helpful.
>>
>> Claus.
>>
>> Claus Trelby
>> Managing Engineer/Partner
>>
>> XEPA Digital
>> 1137 Branchton Road, 19-N-3
>> Boyers, PA 16020-0137
>> www.xepadigital.com
>> ctrelby@xxxxxxxxxxxxxxx
>> P:724-794-3686
>> F:724-794-3292
>> C:805-490-1730
>>
>> --------------------------------------------------------------
>>
>>
>>
>>
>>
>> --
>> Best,
>>
>> Goran Finnberg
>> The Mastering Room AB
>> Goteborg
>> Sweden
>>
>> E-mail: mastering@xxxxxxxxx
>>
>> Learn from the mistakes of others, you can never live long enough to
>> make them all yourself. - John Luther