As always, Richard has made some very astute comments regarding the 
issue of re-hydration. I have only had experience with Magnetophon type 
L tapes; the only type C tapes I have ever seen were in the Mullin 
collection and a few reels in a couple of archives I've worked with. 
Either way, you will need a set of modified guides for the 6.5mm tape (I 
used a heavily modified Studer A-80 transport for most of these, which 
required a bit of precision machining to get right, but other machines 
with modified guides should work as well).

I used distilled water with a small amount of Kodak wetting agent, but I 
don't think it makes too much difference. On most tapes, I've 
re-tensioned the tape with a reverse (flipped) wind on the pack to 
reduce cupping after about an initial 24 hour exposure, and then treated 
it for another 24-48 hours before cleaning and playing. There are 
probably some other viable approaches, but this has worked quite well on 
a number acetate base tapes from the 1940's to the 1960's.

--Scott

Scott D. Smith CAS
Chicago Audio Works, Inc.

On 12/9/2011 4:14 PM, Richard L. Hess wrote:
> Hi, Simon,
>
> I apologize for not responding sooner to your question.
>
> Magentophonband Typ C was produced up until 1944 when the factory 
> burned in an industrial accident. From then until the end of the war 
> (and beyond) Typ L was the only tape manufactured in Germany (as far 
> as I know). Typ L is Luvitherm (PVC) and is one of the few homogeneous 
> tapes ever manufactured. Typ C is a much more conventional coated 
> acetate tape.
>
> When I transferred several dozen reels of Typ C (a total of 51 mostly 
> Typ C and Typ L from the Mullin-Palmer collection and a few dozen more 
> from the Eve Mullin Collier collection) all of the Typ C tapes played 
> well, even though they were somewhat stiff. I can imagine that they 
> have become even stiffer in the intervening years.
>
> I transferred a half dozen Tonschreiber B reels (also Typ C, if I 
> recall correctly) a few years later for Stanford (these were part of 
> the Ampex Museum Collection which is now housed at Stanford). These 
> had been stored in metal cans as opposed to the cardboard boxes of the 
> other collections (I also did a few reels of mostly Typ L for the 
> Pavek Museum). These reels stored in metal cans were suffering from 
> vinegar syndrome.
>
> The first caveat I have is that these tapes are 6.5 mm wide as opposed 
> to 6.35 mm wide and if you are having difficulties playing them or 
> they are bouncing around part of the issue may be binding in the 
> guides. I ended up taking a file to the worn side of a set of fast 
> guides in one of my Sony APR-5000 head assemblies in order to widen 
> the guides to more easily accommodate the tape (I can loosen the guide 
> and turn it back to a never-worn side for 6.35 mm wide tape).
>
> The one tape that I had from the Eve Mullin Collier collection that 
> was very stiff (much like a carpenter's tape measure with the cupping 
> in it) was of concern. This was the early (circa 1935) tape and was 
> only made for about two years if I recall correctly). I called 
> Friedrich Engel in Germany and we talked about it a bit. He suggested 
> a process of hydration. I placed the tape above some water in a closed 
> plastic storage bin for about 24 hours.
>
> When I removed the tape, it was like a silk ribbon--very pliable. The 
> tape played fine (unfortunately, Mullin had used it as an experimental 
> tape and there were only series of test tones on it. I ended up not 
> digitizing it at all. Too bad, after all that work, but it proved the 
> concept.
>
> I tried rehydration once more with an acetate tape that had fallen 
> behind a wood stove in Vermont and stayed there several winters. It 
> was of no use because the edges of the tape were actually fused 
> together in spots, so nothing would help. It appeared that the 
> rehydration process weakened the tape, but the wood-stove treatment 
> didn't do it any good previously.
>
> If you are looking for more information about acetate film, the Image 
> Preservation Institute (IPI) at Rochester Institute of Technology has 
> some information on their website.
> https://www.imagepermanenceinstitute.org/
>
> Some of their papers are cited in my paper on tape degradation that 
> was originally presented at the Audio Engineering Society's 121st 
> convention in October 2006 in San Francisco was published in the ARSC 
> Journal in the Fall of 2008. It is available here:
> http://www.richardhess.com/tape/history/HESS_Tape_Degradation_ARSC_Journal_39-2.pdf 
>
>
> IPI is also a source of information on vinegar syndrome. As Tom 
> mentioned, Kodak tape is quite susceptible.
>
> Here are a few links related to Vinegar Syndrome from my site, 
> including the old German tapes in cans.
> http://richardhess.com/notes/2006/10/16/acetate-tape-buffered-by-cardboard-box/ 
>
> http://richardhess.com/notes/2006/10/19/circa-1943-german-acetate-tape-anomaly-or-mine-canary/ 
>
> http://richardhess.com/notes/2009/04/07/kodak-durol-triacetate-tape-with-bad-vinegar-syndrome/ 
>
>
> Here is a list of many degrading tapes and the current thoughts of 
> what to do with them.
> http://richardhess.com/notes/formats/magnetic-media/magnetic-tapes/analog-audio/degrading-tapes/ 
>
>
> I see while I was typing this Don Tait mentioned rehydration.
>
> Cheers,
>
> Richard
>
> On 2011-12-08 6:48 PM, Simon Kunz wrote:
>> Dear all,
>>
>> I would like to use camphor on a brittle acetate tape to smoothen it 
>> and make it playable. I have recently read of this procedure for film 
>> and I wondered if it would work in magnetic tapes as well.
>> Does anyone have some experiences with this kind of treatment? Are 
>> there any published articles concerning this topic? (whether applied 
>> to film as to magnetic tape)
>>
>> The tape I would like to treat is a Magnethophon Typ C from 1943.
>>
>> Every hint is appreciated! If you prefer you may contact me off-list.
>>
>> Simon Kunz
>