I am not sure I would agree with Peter that polyester tapes can be stored at
0% RH without damage. Although there are some in outer space, that is a
special case. I guess it would depend on the specifics - I don't think there
has been any testing to support that there would be no damage - certainly
not any long term or accelerated aging testing that I have ever heard of. I
don't think that encouraging the hermetically sealing of tons of tapes is a
good idea. I can tell you that operationally (not storage) I can think of a
number of problems trying to play back at 0% RH. Don't even think about it
even if you could. There would be the acclimatization issue of going from 0
to a more normal environment for playback.


        Jim Lindner
        Media Matters, LLC
        Email: [log in to unmask]
        Address: 500 West 37th Street, 1st FL
        New York, N.Y. 10018
        eFax (646) 349-4475
        Mobile: (917) 945-2662

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Friday, June 11, 2004 1:42 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] storage media

A few extra comments and observations:


Polyester-base tape does not have any structural component that requires
water.  Brand new tape will exhibit some moisture content when tested but
water content in the tape can be considered a contaminant.  It is
conceivable that polyester-base tape can be stored at 0% humidity without
damage and no hydrolysis will happen- the tape should not "physically" decay
(Of course, dimensional changes associated with the reduced humidity can
cause serious pack-slip). Acetate-base tape will be damaged by 0% humidity.

Sealing containers:

No standard tape case is either water or air-tight.  This is done on purpose
to allow moisture trapped in the tape or case to escape.  Tapes have been
successfully, hermetically sealed but the process required pre-processing to
insure that the humidity level sealed in the container was very low.  One
process required a few weeks of pre-processing and the tapes were sealed up
under light vacuum conditions.  If you seal up a polyester-base tape that
still has a high moisture content you can actually accelerate the decay.

Cardboard vs. plastic cases:

It is unlikely that archives are going to replace all of their
cellulose-based boxes with plastic cases but, under certain circumstances,
plastic cases are better.  First, we have examined thousands of cardboard
tape boxes that have started to decay and deposit debris on the tape.  This
can cause playback problems, particularly with video and high-data-density
recordings.  Second, plastic cases provide substantially more protection to
the tapes if there is a disaster.  We have been doing disaster recovery of
magnetic tapes for over twenty years and tapes in plastic cases usually show
less than 1/2 the disaster-related exposure exhibited by tapes in cardboard.
The reasons are fairly obvious: cardboard provides little protection from
crushing or piercing damage, it burns fairly easily, it allows water to pass
through, it absorbs and retains water and it promotes fungal growth if it
stays wet for any length of time.

Peter Brothers
(201) 440-6589

Restoration and Disaster Recovery Service Since 1983