At 06:59 PM 2009-02-21, Sarah Norris wrote:
Hello,
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
http://is.gd/kqVy or found here:
http://www.richardhess.com/tape/history/index.htm
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
http://mint.ua.edu/pdf/reviews/Spring%202002/Pollution%20Prevention.pdf
http://www.research.ibm.com/journal/rd/302/ibmrd3002H.pdf
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.
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.