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Re: [ARSCLIST] Fwd: Sticky AGFA PEM 469
Charles:
I read the paper by Dr. Bertram years ago and understood the paper just
fine. I have also spoken personally with Dr. Bertram on a number of
occasions. I am, on the other hand, somewhat bemused about why you bring up
Dr. Bertram's paper on print-through in response to my query about the
existence of specific data.
The effects of elevated temperatures on print-through have been observed and
acknowledged for some time. The paper by Dr. Bertram is quite good and you
do the community a disservice to imply that only someone with an advanced
degree in both mathematics and physics could possibly understand it. Should
anyone wish a greater understanding of the print-through phenomenon, I
highly recommend reading it. It is quite good and quite easy to digest.
However, my earlier comment was not about print-through. You stated in your
posting that you found a noticeable drop off of signal that you attributed
to baking. I simply asked if you had any quantifiable data on the phenomena
that you stated you had observed: the drop off of signal, not print-through.
Print-through is a different phenomenon.
If you have the data, fine. If you don't have the data, fine. I'm not
saying it isn't possible. I just said that, after significant looking,
neither I nor the technical commission could find any firm data on signal
loss due to baking- we found lots of data about print through in a wide
variety of circumstances- but that's not relevant to the specific question
asked!
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: Tuesday, April 08, 2008 2:16 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] Fwd: Sticky AGFA PEM 469
Peter: You can find a mountain of information on this subject in an
article "The Print-Through Phenomenon" written by Dr. Neal Bertram and
published in October 1980 AES journal, Volume 29, No. 10, pages 690
through 705. The paper is highly technical and will only be completely
understood by those who have advanced degrees in Mathematics and
Physics. All the information is there, but it may not be in the data
form you might want or like. If not, someone can work up a data
format if they are willing to do some additional homework. I
mentioned the negative effect baking has on print through in my own
AES paper and worked out the figures for the specific case I had in
mind. It was not possible to go far into great detail as it gets long
and complicated very quickly. The above paper should answer all your
questions.
Charles Richardson
On Apr 7, 2008, at 12:22 PM, peter@xxxxxxxxxxxxx wrote:
> 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