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ARSCLIST  February 2011

ARSCLIST February 2011

Subject:

Re: static noise

From:

Tom Fine <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Wed, 9 Feb 2011 13:59:35 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (141 lines)

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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