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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.



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