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Hi, Corey,

Thanks for the kind words!

You can help if you have any of the tapes that are shedding shards of 
mag coat by sending small samples. I will have a shipping address in a 
few days. Also samples of similar tapes from the same project that don't 
have the problem would be useful.

More comments below under your questions.


On 6/1/2016 2:28 PM, Corey Bailey wrote:
> Hi Richard,
>
> Thank you for taking on this project. If there is anything I can
> contribute from the Left Coast, please let me know.
>
> Three questions immediately come to mind which could lead to some testing:
>
> Why do some audio tape formulations seem to last the test of time and
> other formulations are (almost) guaranteed to be SS? Generally, those
> tapes that are guaranteed to be SS are much newer formulations.

In order to make room for more magnetic particles, as I understand it, 
more aggressive binder material was used (the idea was to have more 
active magnetic domains and less glue). At the time (1970s), BF Goodrich 
sold a product called "Estane" I believe. (I am doing this from 
memory--I looked into it back in 2008 and it went nowhere). This was a 
family of products and there were also other, similar products. They had 
the magic characteristics needed.

Have you ever noticed some "polyurethane" coated tables, especially at 
restaurants have gone sticky? I believe that is the degradation of the 
polyester polyurethane and the lowering of its glass transition 
temperature, brought on by constant washing. I don't think it's left 
over Coke from the last patron.

> Does the back-coating of those tapes that are back-coated contribute to
> tape degradation? There has been some testing , mostly by Charles
> Richardson, that suggests that the back-coating may lead to SS over time.

I believe there has been other testing of this hypothesis, but I do not 
know the result. There are tapes which go sticky without back-coating, 
but it is conceivable that the back-coating can be a catalyst.

> Why are we now seeing evidence of SS with digital audio (and some DV)
> tapes? These formulations and manufacturing procedures are completely
> different than analog audio tape.

Are they really? By "completely different" are you referring to ME 
(Metal Evaporated) tape? I believe MP (Metal Particle) tape is still 
coated with a binder and that binder has gone sticky. I have seen both 
1/4-inch Digital Audio and DAT tape from Ampex, both bearing the part 
number 467 which have been rendered playable by baking. It would not 
surprise me if Ampex made this tape with chemically related binders to 
the analog audio tape, but with different size particles and coating 
specifications if it is MP tape, which I think most of the reel-to-reel 
DASH tape (at least in 1/4-inch) is.

We also had issues where some Mitsubishi DASH tapes could not play and 
we tried to get them into cold playback, but no one could do that. When 
that was happening (almost a decade ago now), everyone was afraid of 
baking digital audio tape. At the time, I suggested that stick-slip 
(even if you didn't hear a squeal) could be the culprit making the eye 
pattern close and the "bit slicer" fail to properly read enough bits.

I hope this helps,

Cheers,

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