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Re: [ARSCLIST] Proper storage of mylar/acetate tapes


Ideally, the two types of tape would be stored differently - acetate with
more humidity and mylar with less humidity.  If they share the same storage,
you'll need to compromise.  In my experience, the acetate can be remediated
be rehydrating it, which requires no high temperature exposure and in my
experience little or no negative sonic side effects.  We all know that
certain types of mylar/polyester tape stocks may need to be baked,
if exposed to too much humidity.  And baking can reduce high frequency
response (by how much, can be, and is often debated).

If I were faced with the same compromise of single storage for the two
media types, I would suggest biasing towards an optimal environment for
mylar/polyester for two reasons: (1) the bulk of your collection is
mylar/polyester, and (2) the acetates can be remediated with less negative
sonic impact.

Eric Jacobs

The Audio Archive, Inc.
tel: 408.221.2128
fax: 408.549.9867
Disc and Tape Audio Transfer Services and Preservation Consulting

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Tom Fine
Sent: Wednesday, October 29, 2008 4:35 AM
To: ARSCLIST@xxxxxxxxxxxx
Subject: [ARSCLIST] Proper storage of mylar/acetate tapes

A client of mine is moving to new digs and has the opportunity to set up a
better storage area for
their tapes. This is a collection of 500 or so reels, all have been
transferred to a managed digital
storage system. About 400 of the reels are old brown-oxide acetate/mylar
with a few odd cellulose
base in the bunch. The rest are more modern backcoated types (about a dozen
were trouble-era Ampex
456 and required baking before transfer).

I read through the following:

AES E-Library: Tape Storage Problems by Radocy, Frank

Imation document

Australian government:


There seem to be some conflicts about the following issues:

1. what humidity level is too low for acetate/mylar? And, what is the true
optimum temperature
range? The research done in the 50's by AudioTape (ie reaseach done by one
of the manufacturers at
the time the tape was being manufactured) indicates the 40-50 degrees F
recommended in the LOC
document may be too cold, especially at low humidity levels. The humidity
level recommendations for
older tapes seem to be in the 40-60% range, which is easily achievable in
the client's new digs, but
we want to make sure to get it right so the tapes don't curl any worse over
time. My own experience
in standard Northeastern US households is that acetate tapes hold up best
(ie don't develop edge
warp and terrible print-through) if stored in a cool, dry downstairs (with
"dry" being, real-world,
60-70% humidity usually, sometimes lower in winter months and "cool" being
temp range of about 55-70
degrees F). Obviously we are going to avoid a swinging range of temp and
humidity because that is
damaging to tapes, according to all research I've read.

2. the temp/humidity levels appropriate for mylar seem a little different
from backcoated tapes,
but, can the backcoated tapes "live" ok in a mylar-centric environment? In
other words, humidity and
temp may be a bit higher than sometimes recommended for backcoated tapes.
The client could store the
backcoated tapes in a separate area, but my thinking is, we know what tapes
have sticky-shed and we
know they'll need baking before playing in any case. The other tapes are 30+
years stable so
unlikely not to be fine under the better-than-before conditions (ie from now
on more constant temp
and humiditiy).

I should add, we only had one vinegar tape and it was determined that the
content was non-valuable
so the tape was destroyed. The sticky-shed tapes did have valuable content
but I got a very good
transfer so it's unlikely they will need to be played again. The client is
more concerned about
keeping the analog material as a backstop if the digital archive ever fails.

Thanks in advance for your input. I am particularly interested in what
storage conditions are being
used for large collections of similar tapes.

-- Tom Fine

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