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Re: [ARSCLIST] Acetate tape discolours tape box

Hi, Tom,

Perhaps I assumed too much in my paper, but film -- especially 35 mm magnetic film -- is a major victim of Vinegar Syndrome (VS). The acetic acid is a catalyst and as Bev said, after a certain point, it auto-catalyzes. Iron is also a catalyst which is why film/tape stored in steel cans (like the Tonschreiber Magnetophonband Typ C) will suffer more -- much more -- than tape stored in cardboard.

The amount of acetate basefilm in mag film is much greater than tape. I believe the basefilm thickness is about 5 mil vs. 1.5 mil for tape.

One of the reasons for posting the picture was that there is an ongoing discussion about the two potentialities for mag tape vs. mag film for VS.
(1) Tape will never deteriorate like film because there are different amounts of the active chemicals
(2) Tape will deteriorate like film but the time scale is longer.

I am a proponent of (2). Michael Casey and others believe (1) until (2) is proven, but following the advice from (2) is obviously more conservative, but costs more.

This is the reason that I hope that Joe Iraci and I can develop a test for freezing acetate tape and see if the "DO NOT FREEZE" warnings we have been given are really valid. It is known that freezing acetate film will slow down the VS process enough that it essentially becomes a non-issue. If Joe and I can get to a point (and the testing is being delayed for unavoidable reasons) where we are comfortable that freezing is safe at least for acetate tape, then this becomes less of an issue.

The Corbis purchase of the Black Star photo library included pulling the library out of the hot, steam-heated Manhattan office building it was in and freezing it in a limestone mine in NW Pennsylvania. When I spoke about this with Henry Wilhelm a few years ago (on my way to the AMIA conference in Portland) he said that there probably wasn't time to digitize the entire collection in the previous storage conditions because by the time they got to the last images, they would be deteriorated beyond usability.

I think my Tonschreiber reel is a "mine canary" for all acetate tapes.

Why some fail and others don't is very complex. It has to do with initial chemistry and long-term storage conditions.

We are not sure that the Image Permanence Institute (IPI) Acid Detection Strips (A-D strips) are accurate with tape -- or even useful. They have been calibrated for film.

I'm considering buying a pH meter and testing that box before I return it to the client. (any suggestions on good or bad pH meters would be appreciated).



At 01:52 PM 10/17/2006, Tom Fine wrote:
Hi Bev:

OK, this is great. Now I understand a lot better. Thanks!

The key seems to be, better to get the tapes transferred sooner.

One big question remains -- why do some acetate backed tapes seem to get this worse than others? Again I say that I've never run into a vinegar-smelly AudioTape reel but often find this with Scotch 111 and even 131.

If someone is set up to look at breakdown amounts or pH or whatever you measure to see if vinegar has set in and how bad it is, I can probably dig up a few small samples of both Audiotape that is not obviously acidic and Scotch tape that is.

-- Tom Fine

PS -- I am told that Scotch and Audiotape 35mm mag-film from the late 50's into the 60's has a very bad tendancy to develop this problem and the film does shrink and curl. Now, why is this material so likely, indeed guaranteed to develop this and break down? Is it because of the thicker film base made of acetate, thus more concentrated material to develop and self-feed on the syndrome?

Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.

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