Jay "MRL" McKnight actually has a paper looking at what might be a 
"safe" field.
(I don't see it currently indexed on his HTML, but Google found it)
and the IASA has a report and I'll leave the exercise to the student 
converting units
between Jay's paper and the IASA report.


Thanks for the kind words about my paper and website. I have a slightly 
different mental model of what you're describing:
(a) Temperature and humidity and especially the cycling thereof is not 
good for tapes.
(b) Tom Fine postulates (and I tend to take this seriously) that too-low 
humidity such as that recommended for storing tapes subject to SSS is 
very bad for acetate tapes.
(c) The binders that are extremely subject to degradation based on 
normal room temperature heat/humidity were improper applications/designs 
or poorly/incompletely reacted during manufacture.
(d) While storage conditions play a role, there are tapes with inherent 
vice that will self-degrade far more rapidly than other tapes. This 
"vice" was built-in during the design/manufacture process.
(e) Tape type numbers are only a loose approximation for identifying 
tape chemistries
(f) Lot-to-lot variations can be VERY substantial even within the same 



On 2013-04-17 3:42 PM, John Haley wrote:
> I just read your 2008 tape article from ARSC Journal, Richard, and looked
> at your website, thanks very much for sharing all this valuable info you
> have collected about the vicissitudes of various tapes.   I have not seen
> this much good collected empirical info anywhere else.  You're the man!
> I have always assumed that in addition to things that happen resulting from
> manufacture, tapes are highly affected by things like heat and humidity
> during the years that they have been stored.  A household in the Northeast
> that does not run a humidifier in the winter can get far dryer than the
> Sahara desert, to the detriment of everything in the house--furniture,
> wood, living things and things made from chemicals, like tapes.
> Thanks,
> John Haley
> On Wed, Apr 17, 2013 at 3:06 PM, Shai Drori <[log in to unmask]> wrote:
>> Jay I assume from MRL? If so, he has a little leaf he hands out with every
>> test tape he sells, that is a very interesting read. In short, he claims
>> (and I believe it) that the tapes are very robust and that if you read
>> through his description you realize that it takes a very strong magnetic
>> field to erase a tape.
>> Shai
>> בתאריך 17/04/13 7:01 PM, ציטוט Richard L. Hess:
>>   Hello, Gregorio,
>>> In general, the magnetic record seems to be rather robust and it mostly
>>> decays from close encounters with magnetic fields stronger than the
>>> Earth's. I know of no studies that have attempted to quantify this, but I'm
>>> copying Jay McKnight who may know of a study and if he has any information,
>>> I'll post it to the list.
>>> So, assuming no chemical or physical degradation (which mostly affect
>>> tape via spacing loss across part or all of the tape) and no close
>>> encounters of the strong magnetic kind, the S/N decay rate would be minimal
>>> (I don't want to say zero, but I suspect close to it).
>>> We had the discussion on the Studer list about whether tape or machine
>>> background noise is predominant and Jay chimed in with an "it depends". For
>>> master tapes, generally the tape noise is predominant. There are times at
>>> slower speeds and narrower tracks where head/electronics noise would be
>>> predominant.
>>> As to degradation factors, I have a page I try and keep updated where
>>> this is discussed.
>>> magnetic-tapes/analog-audio/**degrading-tapes/<>
>>> I hope this helps a bit.
>>> Cheers,
>>> Richard
>>> On 2013-04-17 12:32 PM, Gregorio Garcia Karman wrote:
>>>> Dear members,
>>>> I am looking for references in the literature dealing with the study of
>>>> the decay of magnetic remanence as an effect of tape aging. What is the
>>>> expected signal-to-noise decay rate under ideal conditions (i.e. no
>>>> chemical degradation)? In real life, what is your experience in regard to
>>>> different brands / models in similar storage conditions?
>>>> Thanks in advance and regards
>>>> Gregorio
>> --
>> בברכה,
>> שי דרורי
>> מומחה לשימור והמרה של אודיו וידאו וסרטים 8-35 ממ.

Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada                             647 479 2800
Quality tape transfers -- even from hard-to-play tapes.