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.
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.
> 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
> 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.
> 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.
>> On Feb 2, 2012, at 11:34 PM, "Corey Bailey"<[log in to unmask]>
>>> 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
>>> 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.
>>> Corey Bailey Audio Engineering