RE: [AV Media Matters] Audio Vinegar Syndrome

[llufrio@icaic.inf.cu]

Hello, Mr. Green.

The "disease" analogy is a very good one, and very easy for
archivists with
no chemical science knowledge to understand. The very name
Vinegar Syndrome,
instead of using the technical term acetate ester decomposition is the
beginning of it.

Acetic acid is given off when cellulose acetate is decomposed. This acetic
acid (the main component of vinegar) is very volatile, so it comes off as
gas. Since this decomposition occurs in a humid environment, the acetic
vapours combined with water vapour produces an acidic atmosphere. This
acidic (low pH) atmosphere triggers or accelerates the
decomposition of the
cellulose acetate ester which happens to be in that acidic
atmosphere, hence
the spread or contagion of the chemical decomposition to rolls of film or
tape not already decomposing.

This is the reason why zeolites are helpful if incorporated as a
filtering,
gas absorbing medium in the air circulation system of film and
tape vaults.
Kodak "molecular sieve" is nothing more than that, only it's
designed to go
in small porous bags inside the film can, a solution for small collections
only, since you have to change it periodically as it becomes
saturated with
acetic acid.

The key word here is "auto catalitic", as you quote from Graham Newton's
site, a chemistry term meaning self accelerated or self triggered.

I believe the most important research on the chemical reactions
taking place
during cellulose acetate decomposition was made at the Manchester
Polytechnical Institute in the UK.

I hope this explanation serves to help you better understand, or maybe
increases your appetite for more :-)

Regards,

José E. Llufrío
<llufrio@icaic.inf.cu>