Re: [AV Media Matters] Audio Vinegar Syndrome

[rohre@ARLUT.UTEXAS.EDU]

I will take a stab at this assertion.

The appearance of vinegar smell from a tape/film is an indication of
chemical changes originating from exposure to too much humidity at
some point in the life of the media.  The media has started to
hydrolyze, (draw up excess moisture), and is emitting a
decomposition byproduct called amines. In tapes, the binder is
breaking down as it is the hydroscopic constituent of the formula.

I think it is perhaps excessive to characterize this process with
medical terms.  However, you can think of the generation of any high
proportion of chemical fumes, or acid fumes within a confined
enclosure as being likely detrimental, if another tape/film was in
the same confined space such as a box, or can. You simply would not
want an acid to deposit upon your media. And if the amine draws
moisture, it increases the danger to unaffected media in the same
enclosure.

I don't think it would immediately affect media in separate boxes on
the same shelf, and in fact I have some 900 tapes stored in metal
cabinets, and only single reels along a full shelf have ever
exhibited amine production, and in each case, some prior history of
too much exposure to high humidity was found to be a factor.  IE,
master tapes used once aboard ship may develop binder breakdown; but
copies that have been kept in moderate laboratory storage
conditions, do not fail.

Certainly, it is good to periodically check stored media for
degradation, but this is always one of the most difficult things to
do in a media using organization, where you are busier making copies
of current Masters, studying contents of specific media, and have
little time for conservation inspection. One thing we have learned
over the years, is that certain periods in tape production had
problem formulations, and we watch those tapes more than we watch
older/newer tapes.  With so many of our tapes coming out of Marine
(aboard research ship) environments, we have had to steel ourselves
to occasionally going after data and finding damaged media.  Lucky
for us, most instrumentation recording for science was done on mylar
base film, rather than acetate, and thus we can bake it.  I cannot
think of any contamination caused by acetate breakdown that could
affect other individually protected media. I would think in the case
of film, which is stored in metal cans, the damage would be confined
within the tightly sealed can.  Yet, I have seen a conveniently
large cannister used for two reels of media.  That may be more
common in the film industry. I hope these thoughts reassure the
archivists.  As always, a proper cool and dry storage environment is
a good defense, but then you have to deal with the prior history of
the media you archive, and if from outside sources, that may be a
problem in not knowing how well the media was stored before reaching
your facility.

Stuart M. Rohre
Applied Research Labs, ESL, Analog Digital Tape Facility
Univ. of TX, Austin