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Re: [ARSCLIST] TAPE resources online
At 05:10 PM 2007-08-16, Tommy Sjöberg wrote:
Hello list,
I was intrigued to read the US Patent 6797072
for curing sticky-shed tapes. It advocates
removal of the back-coating in a machine using
isopropyl alcohol and cotton swabs, wet and dry.
Now I'm wondering if anyone on this list has
tried the method and would say something about it?
Tommy Sjoberg
Hello, Tommy,
Charlie Richardson and I have differing opinions
about the potential efficacy of this technique
based on a different understanding of the
mechanism behind the degradation we're trying to arrest/cure.
It is my understanding that the underlying
chemistries of both the mag coating and the back
coating on most of the tapes affected by sticky
shed syndrome are similar and subject to
breakdown in the presence of moisture.
The polymer chains break in this hydrolytic
breakdown and even the baking technique does not
cause the long chains to reform, but it does
drive out the moisture to the extent that it makes tapes playable.
Having the two surfaces in contact with each
other exacerbates the condition, but removing the
back coating does not reverse the hydrolytic
breakdown of the mag coating nor does it remove
the propensity of this coating to break down in the presence of moisture.
I believe Richardson recommends cool and dry
storage after removing the back coating which is good for any tape.
Any tape that is starting to degrade should be
copied (generally today that means a good digital
copy) and while the original should be maintained
in case the copy proves faulty, I don't think
you'll get a better copy in ten or twenty years
than you will now. In fact, I think you'll get a worse copy in twenty years.
I do think Richardson deserves credit for
exposing the myth that the back coating is a
non-player in the degradation of the tape, but I
think he went too far to say it's the only player.
Polyester polyurethanes are often unstable. I am
now wondering if I need to replace some older
camera bags that appear to be starting to show a
relative of sticky-shed on the coated fabrics.
We've seen this breakdown in paint on Philips
test equipment as well. Recording tape is not the
only area where polyester polyurethanes are under-performing over time.
Cheers,
Richard
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.