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Ooops, this is an answer to an earlier question by Lou that got stuck in
drafts and I forgot to post.

 As I indicated, I sometimes provide more info than most people want but it
is hard to be accurate with less, as short explanations are too easy to
misinterpret.

Your short term baking time is fairly common and seems to work ok for most
people to do transfers.  Long term baking requires a minimum of 3 to 5 days
before any significant cross-linking will occur. 2" 24 track can take 2
weeks or more to see a significant effect.

Standard baking temperatures are around 50 C.  We use slightly lower for
some tapes, slightly higher for others- but that gets very complicated and
long-winded.

We store at approximately 65 to 68 Fahrenheit and between 25 and 30% RH.
Standards put a maximum RH level at 50% RH but that is the maximum allowed.
The drier the better (for polyester-base tape; acetate-base tape you
shouldn't go below 30%RH).  Standards allow for lower temperatures than I
prefer.  I think the lower level is about 54 Fahrenheit so as not to affect
lubricants. I recommend a higher temperature and a lower humidity.  If you
store near room temperature and at a low humidity, it reduces/eliminates
issues of acclimatization and condensation when you remove the materials
from storage.

The standards for long-term storage can be somewhat misleading if not read
very carefully.  They supply a range of temp/RH combinations giving the
impression that the effects of temperature and RH are somewhat equal on tape
decay.  Actually moisture is the primary decay vector for magnetic tape and
temperature is mostly an issue as to how quickly or intensely the moisture
affects the tape.

The other important issue with long-term storage is stability.  Tape expands
and contracts with changes in both humidity and temperature.  The primary
vector of expansion/contraction is the tape thickness (not the length).
Variations in temp and humidity cause the tape to swell and shrink,
tightening and loosening the tape pack- potentially causing damage over
time.

Have a good holiday weekend.  


Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]
Audio and video restoration and re-mastering since 1983




-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Lou Judson
Sent: Friday, September 1, 2017 1:41 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] a question of semantics concerning sticky shed?

This is quite a wordy explanation, and I do not doubt or argue with it. My
only interest is in recovering tapes people bring me to transfer, and so far
have had excellent success, baking 8 - 10 hours, cooling the some amount of
time, and playing them then. I have not examined them later, the storage
comment was third-hand anecdotal, not personal or scientific.

But - can you please specify what you mean by "Short-term baking?" and is
long-term better? How short, how long and what temperatures? Also, what do
you recommend for long term storage after the treatment?

Thanks. Peter.
<L>
Lou Judson
Intuitive Audio
415-883-2689