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ARSCLIST  February 2012

ARSCLIST February 2012

Subject:

Re: Baking Digital Audio tapes

From:

Tom Fine <[log in to unmask]>

Reply-To:

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

Date:

Fri, 3 Feb 2012 13:21:25 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (225 lines)

There is an existing mitigation for vinegar-effected magnetic films. Contact one of the experts in 
Hollywood for info. Nick Bergh, who presented at ARSC last year, definitely knows the details on 
this. It's costly, but it can lead to good-fidelity recovery of valuable audio. Probably far too 
costly, for example, to apply to a vinegar-damaged Everest or Command mag-film. But when it's a 
master music track for a popular/famous classic movie, the business model (market demand) is there 
to justify the cost.

-- Tom Fine

----- Original Message ----- 
From: "[log in to unmask]" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, February 03, 2012 1:04 PM
Subject: Re: [ARSCLIST] Baking Digital Audio tapes


> Exciting news that there may be a cure for vinegar syndrome. Would this apply to film as well as 
> tape?
>
> Pls keep us informed of any new developments.
>
> Thanks
>
> Joe Salerno
>
>
> On 2/3/2012 11:02 AM, Richard L. Hess wrote:
>> Hello, Corey, Brian, Tom, and Chris,
>>
>> I think this is phenomenally interesting and am not surprised.
>>
>> Chris, I think you are lucky recovering tapes from the 1960s. There was
>> actually the introduction of a new problem in the 1970s with the change
>> to polyester polyurethane binders on tapes. This change in binder
>> material also was accompanied by a change to back-coated tapes where
>> there were two binders in contact with each other.
>>
>> So yes, tapes from the 1970s and later are more problematic than simpler
>> tapes from the 1960s in many instances.
>>
>> Our good friends in Austria may be close to disclosing a long-term fix
>> for vinegar syndrome, so that side of early tapes may be covered soon.
>> Thanks to Nadja Wallaszkovits and others for their work on this.
>>
>> Back to the specific subject at hand:
>>
>> While the precise mechanisms have been discussed at length, I am not
>> aware of a completely definitive molecular-level model of this process
>> (degradation + baking) that is fully accurate and complete. This is
>> discussed obliquely in my ARSC paper of a few years ago.
>> http://www.richardhess.com/tape/history/HESS_Tape_Degradation_ARSC_Journal_39-2.pdf
>>
>>
>> I am not certain how the time and temperature curves interact, but,
>> obviously there is a certain amount of energy under the curve as long as
>> one stays away from trigger points. I recently researched PET film a bit
>> more and found that the glass transition temperature (Tg) of the
>> basefilm is considered to be about 70 C while its melting point is
>> around 250 C.
>>
>> Let's look at the temperatures involved:
>>
>> The Ampex patent uses both 50 C and 54 C. Corey's post indicated that
>> they used 48 C.
>>
>> There is not a huge difference between 48 C and even 54 C when the
>> next step of possible risk is 70 C. (Sorry, science is done in C, but
>> these four temperatures are 118, 122, 129, and 158 F.) However, I am
>> not generally comfortable exceeding 54 C.
>>
>> The usual concern for digital audio tape is that the dimensional
>> stability of the basefilm will be damaged. If the Tg of the basefilm is
>> 70 C, then I don't think we need to worry at 54 C or below, especially
>> with a melting point of 250 C or so.
>>
>> The Tg of the mag coat of one squealing tape, by the way, was measured
>> at about 8 C. This helps support my cold playback concept. (Tg is the
>> point where the surface changes from glass-like to rubbery).
>>
>> ========
>>
>> There is another thought process involving long-term degradation as
>> plotted against time as well as the amount of treatment needed to make
>> the tape playable.
>>
>> If we look at some critical times we can see perhaps:
>>
>> Onset of SSS
>> Medium SSS
>> Heavy SSS
>> Almost impossible SSS
>>
>> Within a short period (less than a year?) a tape goes from playable to
>> needing baking. This appears to be anywhere from 5-10 years from date of
>> manufacture.
>>
>> Of course, all of these timings are modulated by storage humidity (and
>> to a lesser degree temperature and the fluctuation of both).
>>
>> At some point, casual baking (4 hours or so) stops being effective.
>> Let's say that's Medium SSS.
>>
>> Further on, we find we need to bake for 24 hours or a bit more. Let's
>> say that's Heavy SSS.
>>
>> At some point we see Almost Impossible SSS with one reel I was
>> successful with taking four 48 hour cycles to make it playable (it was
>> not playable after two, and thinking this is all logarithmic, I just
>> doubled the previous baking).
>>
>> So, with these digi tapes we are in the early stages and they are
>> responding just like analogue tapes did back in the 1980s and 1990s. One
>> factor that is making the digi tapes easier to bake is that the coatings
>> on the digi tapes are thinner than on the analogue tapes.
>>
>> I predict that digi tapes will require longer baking times down the
>> road. Corollary to this thought: TRANSFER ALL THE DIGI TAPES NOW before
>> they become a bigger problem (not to mention machine parts availability
>> which is far, far worse now than analogue) and the parts are finer, less
>> generic, and more complex...is there a warning in that?
>>
>> ====
>>
>> What is Ampex 467? I have no idea what Ampex 467 really is other than a
>> cool-looking marketing number that combines the 400 designation of the
>> successful Ampex analogue line (406, 456, 407, 457) with the sleek "jet
>> age" favourite digit of Boeing (707, 727, 737, 747, 757, 767, 777) and
>> an arbitrary tens digit that is greater than 50.
>>
>> The reason I am so cynical about this is that 467 was used on DASH and
>> (R)DAT tape and I am pretty certain the cross-section of these tapes is
>> not the same. I have 1/4-inch 467 here (and it did not seem to suffer
>> from SSS in 2006 or so when I played with it for the paper) and I don't
>> think it looks/feels like anything a DAT machine would be happy playing
>> (if slit to the proper width). While thin, it is not DAT thin.
>>
>> I have had one happy experience baking a DAT tape within the last six
>> months (and no unhappy experiences ever...unhappy is defined as making
>> the tape worse). Here is a sample of one that DAT baking is also a
>> possible contender to solve that format's problems.
>>
>> ====
>>
>> One possible "end game" scenario for all this is someday baking a tape
>> for a week or two at 54 C and finding it still doesn't play. Did I
>> mention do it now? I'm glad to hear all the DASH copy work is going on
>> as I know that was a heavily relied upon format in Hollywood.
>>
>> Corey and Brian, please send me a private email
>> ([log in to unmask]) giving me permission to quote your posts on my
>> Degrading Tapes page. I think this is hugely important information as I
>> have been asked this question recently by someone who is running into
>> the same problems.
>>
>> Thanks again.
>>
>> Cheers,
>>
>> Richard
>>
>>
>>
>> On 2012-02-03 10:57 AM, Brian Bartelt wrote:
>>> My company, Post Haste Sound, was tasked by MGM to help migrate their
>>> DASH library. We found that many many elements were exceptionally
>>> problematic despite their relatively young age.
>>>
>>> We experimented with many different ways to improve playback and found
>>> low temperature baking to be the most effective method to improve
>>> playback, and ultimately had a playback success rate on the project of
>>> over 97%.
>>>
>>> Using these techniques we are now beginning other similar DASH
>>> migrations for other clients, as people continue to discover that
>>> their DASH assets aren't aging well.
>>>
>>>
>>> Thanks,
>>>
>>> BB
>>>
>>> On Feb 2, 2012, at 11:34 PM, "Corey Bailey"<[log in to unmask]>
>>> wrote:
>>>
>>>> Hi All,
>>>>
>>>> I thought the members of this list might find this interesting:
>>>>
>>>> Recently, some 1/2-inch Sony DASH (3324) format tapes were shipped from
>>>> the UK to the Warner Bros. Sound Transfer Dept in Burbank, CA. The tapes
>>>> would not play and exhibited Sticky-Shed Syndrome.
>>>> I was asked if I thought it would be safe to bake the tapes. My response
>>>> was that it could be risky and if we were to attempt it, the tapes
>>>> should
>>>> be baked at a much lower temperature for 24 hours or so. It was
>>>> decided to
>>>> try my suggestion since there was nothing to loose at this point.
>>>>
>>>> The details:
>>>>
>>>> 3 reels of Quantegy 1/2-inch 467 Digital audio tape, originally recorded
>>>> in August of 1999.
>>>>
>>>> 2 reels of Quantegy 1/2-inch 467 Digital audio tape, originally recorded
>>>> in May of 2004.
>>>>
>>>> The tapes were baked for 16 hours at 118 degrees F. and then left in the
>>>> oven for 6 additional hours as the oven cooled. The decision was made to
>>>> end the baking at 16 hours because the Transfer Dept. Supervisor
>>>> wanted to
>>>> test the results to see if there was any improvement that might warrant
>>>> further baking. The first tape tested played just fine so each tape was
>>>> tried in succession with the same positive results.
>>>>
>>>> Cheers!
>>>>
>>>> Corey
>>>> Corey Bailey Audio Engineering
>>>>
>>
>
> -- 
> Joe Salerno
> 

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