Again, my real-world (reel-world) experience is that circa 1950's and 1960's brown-oxide
non-backcoated tapes, especially those of acetate base and especially 1-mil acetate base, are very
prone to warping, becoming brittle and otherwise having playback difficulties if exposed to long
periods of too-hot and/or too-dry conditions. Including un-air-conditioned shelving in a first floor
room of a suburban NYC home (too hot in the summer, too dry in the winter). I have heard reports of
tape that did not have previous problems developing brittleness and oxide-shed when moved from a
records-storage facility to a very dry climate-controlled archive designed around parameters to
store sticky-prone backcoated tapes.
Similar 50's/60's acetate tapes stored in a cooler downstairs area (not a wet basement) do not have
warping or brittleness. Similar acetate tapes stored in a known moderately damp basement are
sometimes moldy but not brittle and, if stored tight-wound, are not warped. Similar acetate tapes
stored for 10+ years in a non-climate-controlled attic were all unusable due to warping and
brittleness.
As far as I know, image media generally does not involve as thin an acetate film as magnetic tape, I
think that might be part of the issue.
To each their own, but I will not expose any acetate tapes I value to very low humidity levels, at
any temperature, and I avoid temperatures over mid-60's.
For what it's worth, my again real-world experience with sticky-shed tapes is that even keeping them
in a warm/dry environment (furnace area of a dry downstairs), even in a plastic bag with
anti-moisture packets, does not prevent them from going back sticky. I'd love to see more controlled
experimentation along those lines -- attacking the question of, can you bake a tape once and store
it in some fashion where sticky-shed won't return? If the answer is no, then designing super-dry
tape storage facilities is useless in regards to sticky-shed and potentially harmful to
non-sticky-prone tapes.
-- Tom Fine
----- Original Message -----
From: "Richard L. Hess" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, February 09, 2011 10:29 AM
Subject: Re: [ARSCLIST] static noise
> Hi, Tom,
>
> You raise a good question. I qualified my statement in that I was concerned with hydrolysis but
> there is another factor.
>
> I understand your point about acetate tapes and I had to hydrate a 65-year-old carbonyl iron tape
> when I transferred the Mullin-Palmer collection, but...
>
> If you research at the Image Permanence Institute at Rochester Institute of Technology, you will
> find an application called a "Preservation Calculator" and they use the relationship between room
> temperature and relative humidity to estimate the number of years before some amount of decay sets
> in. I don't recall all of the details, but I suspect there is a paper explaining the calculations
> somewhere on their website.
>
> Here are a few examples
> Temp °C / °F -- RH -- Preservation Index (Years)
> 20/68 -- 40 -- 58
> 20/68 -- 50 -- 44
> 20/68 -- 60 -- 34
> 22/72 -- 40 -- 45
> 22/72 -- 50 -- 34
> 22/72 -- 60 -- 26
>
> As I understand this, it applies generally to all organic-based material, and I think cellulose
> acetate falls into that category.
>
> At none of these combinations, is there a risk of mold germination, but, for example
> 25/77 -- 70 -- 14
> The program estimates 156 days until mold germination.
>
> I know in growing up in a non-air-conditioned house in Forest Hills, New York, our basement had
> mildew and perhaps mold. Here with central air conditioning and a dehumidifer in the basement, I
> do not detect any mold/mildew and the numbers don't generally go above 50%.
>
> One thing that still bothers me to some extent is when one thinks of what %RH is a measure of, the
> amount of water vapour in the air relative to its saturation point, the less I am convinced that
> this is truly the correct measure. %RH varies with temperature for the same moisture content. Dew
> Point is another interesting way of looking at this and IPI also has another version of the
> Preservation Calculator called a Dew Point Calculator.
>
> Cheers,
>
> Richard
>
>
> On 2011-02-09 7:17 AM, Tom Fine wrote:
>> Hi Richard:
>>
>> 40% for acetate and early polyester too? I thought low humidity only for known sticky-shed
>> formulations??
>>
>> My experience with early-era brown-oxide tapes is that they curl/warp less and get brittle less
>> if kept at more typical Northeastern US humidity levels. Tapes I've handled that were kept in
>> very dry environments were sometimes very brittle and in extreme cases would shed oxide as they
>> moved thru a transport. Splices also tend to dry out and fail at low humidity for these era
>> tapes.
>>
>> -- Tom Fine
>>
>> ----- Original Message ----- From: "Richard L. Hess" <[log in to unmask]>
>> To: <[log in to unmask]>
>> Sent: Wednesday, February 09, 2011 7:10 AM
>> Subject: Re: [ARSCLIST] static noise
>>
>>
>>> Shai,
>>>
>>> Thank you for passing this along. Sadly, the author, John Pytlak, passed a few years ago, as you
>>> may recall. He was one of the real bright lights on the AMIA list. Several others are also gone.
>>>
>>> I would caution about handling magnetic tape long-term at 50-60 % RH as it might increase
>>> hydrolysis. The general recommendation for tape is 40%.
>>>
>>> Regards,
>>>
>>> Richard
>>>
>>> On 2011-02-09 5:55 AM, Shai Drori wrote:
>>>> Dear members
>>>> I received the following link through the AMIA list. I was about vitalizing film but turns out
>>>> Kodak has a few suggestions about controlling static build up. Worth reading.
>>>> Shai
>>>> static
>>>> <http://www.kodak.com/US/plugins/acrobat/en/motion/newsletters/archived/pytlak/booth.pdf>
>>>>
>>>
>>> --
>>> Richard L. Hess email: [log in to unmask]
>>> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
>>> http://www.richardhess.com/tape/contact.htm
>>> Quality tape transfers -- even from hard-to-play tapes.
>>>
>>
>
> --
> Richard L. Hess email: [log in to unmask]
> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
> http://www.richardhess.com/tape/contact.htm
> Quality tape transfers -- even from hard-to-play tapes.
>
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