At 06:59 PM 2009-02-21, Sarah Norris wrote:
>I'm looking for any manufacturing information available about Ampex 
>456 and Shamrock 041 tape.  Anything would help, including 
>manufacturing dates and anything known about materials or 
>formulations used.  All information and references are much appreciated.

Hello, Sarah,

What an interesting question. May I suggest that you read my recent ARSCJ paper    or found here:
if you haven't already for background and some chipping away at the problem.

Michael Biel provided a more in-depth analysis of the Shamrock tape 
that I could have, but his explanation expands on what I would have 
said, which is basically, Shamrock tape is anything that didn't meet 
spec that might still show some ability to record and play back. 
3M/Scotch did this too with Melody tape, but when the FTC required 
location of manufacture to be placed on the box, 3M stopped selling 
the stuff (at least in the U.S.) but Orradio/Irish/Ampex/Quantegy 
(that's the lineage of the plant) proudly put Opelika, Alabama on the 
boxes. Think of it this way, selling "seconds" (or "thirds" or 
"fourths") was a LOT cheaper than paying the trash man to haul it away.

As to 456, it is the poster child for Sticky Shed Syndrome (SSS), 
however, all tape manufacturers seemed to have created batches of 
tape which suffered from this. In discussing this recently with Ric 
Bradshaw, a PhD chemist and tape expert, he said that polyester 
polyurethane is a good choice for a binder, but the reaction has to 
be controlled. He also said that crosslinking may not have been the 
correct choice to achieve the best long-term performance (he has yet 
to elaborate on that to me).

Another thing I think we know is that there were oligomers and other 
remnants of the manufacturing process which may not have completely 
reacted remaining in the tapes when they were shipped. The incomplete 
reactions and the excess component parts MAY be a contributing factor 
to tape degradation and could very well explain the batch-to-batch 
variations we've seen from all manufacturers.

Some hints can be teased out of this and related papers

I do have the reference somewhere to the typical family of polyester 
polyurethanes probably used, but can't spend any additional time at 
the moment on this and the above two were what I could quickly find 
in Google. The second one has two authors that deserve to be noted 
Bradshaw and Bhushan.

As to manufacturing specs, much of this lived in the minds of the 
operators, I suspect, who are now long-gone. Some of the people from 
Redwood City may know something, but they are all getting on in years 
and I suspect most if not all of the documentation is well-recycled. 
The real details were considered trade secrets and even some people 
who are still around are loathe to discuss all the details.

On the other hand, the lack of control and the us-vs-them attitude 
that may have existed at some level between Opelika and Redwood City 
cannot be ignored as factors. The folks in Opelika were making tape 
before being bought by Ampex and that could be a root of some of the issues.



Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada       (905) 713 6733     1-877-TAPE-FIX
Detailed contact information:
Quality tape transfers -- even from hard-to-play tapes.