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Deterioration of Acetate TAPES and FILM

Hi, ARSC and AV-Media Matters folk.

Sorry for the cross-post, I think there is a good percentage of non-overlapping membership.

As many of you know, Jim Wheeler and I transferred useful content from 51 reels of tape dating from the late 1940s. This cache belonged to Bill Palmer who, for some time in the early days, was Jack Mullin's partner in getting professional tape recording off the ground in the USA. These tapes are all 1/4-inch (or 6.5mm) wide and are both acetate- and PVC-based formulations. The acetate-based tapes are coated, the PVC-based tapes are homogeneous (that is to say that the magnetic particles are embedded in the film, not coated on it).

We've had some great advice from film preservationists to test for "vinegar syndrome" using the Acid-Detection (A-D) strips from the Image Permanence Institute of the Rochester Institute of Technology. We are now thoroughly confused. While the A-D strips are showing some acidity in the boxes, they are showing more acidity in the acetate tapes (1.0-2.0, partially depending on wind density and other factors), but even a measurable amount (1.0) on the PVC tapes. The latest test put the tapes in ZipLoc freezer bags for about 18 hours with the strips. An empty bag showed a good clean "0" and a strip left out in my home office showed after a week of LA air still very close to "0!"

What I don't understand is that I've been seeing posts concerning severe degradation of magnetic films (both 16mm and 35mm) while neither Jim nor I have any significant reports of the same type of degradation from audio tapes.

We are wondering if there is any significant degradation of acetate audio tapes from "vinegar syndrome" in any archive? And, if so, what are the storage conditions both physical and climatic?

If there isn't any significant degradation of tapes, but there is of films, we're trying to understand the differences (we're especially interested in the state of 1/2-inch and wider acetate-based audio tapes to understand the relationship of media thickness to the problem) and what the causes of the differences might be. This is partially to avoid creating the same conditions that have accelerated this degradation for film, and hopefully to understand what the audio community has done--probably by dumb luck--that can be transferred to the film community to arrest/prevent further "vinegar syndrome" deterioration in the magnetic films.

The major difference that we see relates to storage practice. Audio tapes are typically stored inside cardboard boxes of moderate acidity. Many turn brown (or the inserts turn browner) with age and show all the telltale signs of acidic paper degradation). We are aware that archival boxes are (or at least were) available. It seems that magnetic films are typically stored in sealed metal cans--typically plated steel.

Any information about degrading acetate audio tape and "vinegar syndrome" would be greatly appreciated.



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