Re: [ARSCLIST] Thin tape decay

[dsbardella@xxxxxxxx]

> To the person who wrote mm, please note it's µm
> not mm.

Indeed it is.  The fact is, most of that post was copied directly from a
IASA document, micro meter symbols included.  Somehow the symbol must have
been reinterpreted as mm when copied on the LISTSERVE.  I guess the lesson
is "let copier/paster beware".

Having the exact caliper spec for each tape product is fantastic.  But for
the purposes of prioritizing tape collections in a sizable audiovisual
archive,  I think that (when combined with the thickness of binder, backing
and oxide) 1.5 mil based tapes can reasonably be considered to meet the
IASA guide of 52 micro meters.

Best,

The Person

Daniel Sbardella
The New York Public Library for the Performing Arts
40 Lincoln Center Plaza
New York, NY  10023

212.870.1609


                                                                           
             "Richard L. Hess"                                             
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             08/02/2006 02:45                                              
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Hello, Marcos,

I think that there are no specific ratios that
are useful for determining the degradation rate
of magnetic media. My research of the literature
and the anecdotal evidence seems to suggest that
original manufacturing formulation and anomalies
as well as storage conditions over its life can
affect the tape more than its thickness.

I also think that it's futile to try and save any
tape for 100 years, but rather we should focus on
saving the content. The more I read about even
PET base films and especially
polyester-polyurethane binders the more concerned
I become about century-plus "shelf storage" of analog magnetic tapes.

While a need to prioritize preservation
reformatting (aka "copying") of magnetic media is
important, I do not think it is an exact science.
In general, I would start with tapes with known
degradation symptoms, and do the oldest to the newest.

Following standard storage procedures should
hopefully preserve the tapes long enough to get them copied.

I would transfer acetate tapes before PET tapes
based on base film, but I would prioritize
polyester-polyurethane binder systems, especially
those that I have listed on my website (look
under the tape aging subject heading in the TIPS and NOTES Blog section).

And, yes, I would transfer 18 µm thick tapes
before 50 µm thick tapes. The thinnest tapes (18
and 26 µm nominal) do have a habit of pinning or
blocking, but that may not be related to their thinness.

To the person who wrote mm, please note it's µm
not mm. Also, as you know when measured in µm the
implication is that it is the total thickness of
the tape, while the mil measurement implies a
base film thickness. The two references that I
provided earlier today at www.aes.org/aeshc/ give
detailed information for the thicknesses of each
layer for open-reel audio tapes.

In Windows, you write µ [mu]  as ALT-0181. or,
conversely, you can call µm's micro metres or microns.

Cheers,

Richard

At 10:24 AM 8/2/2006, you wrote:
>Greetings
>
>Was wondering whether anyone on the list knows of any hard data out there
>(or even substantial anecdotal evidence) that shows that thinner tape
decays
>faster, and to what kind of physical decay thin tape is most susceptible
as
>time goes: cupping/curling, brittleness, shedding, etc. And even (and I
know
>this is asking much) whether, say, 0.5 mil is "twice as bad" as 1 mil, or
>"four times as bad", etc. This is not playback-related; rather, picture
two
>reels of the same formulation but different thicknesses, sitting side by
>side for a few years.
>
>Will appreciate any information.
>
>Thanks much
>
>Marcos Sueiro

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.