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.
What an interesting question. May I suggest that you read my recent ARSCJ paper
http://is.gd/kqVy 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: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.