"Richard J Kinch" wrote in message
. ..
What is this stuff? I've found exactly one secret knot that won't pull
apart for tying ends together. Try it.

It is expanded PTFE just like the material they make their gaskets from. I
have always been amazed at W.L. Gore; this company has built a whole range
of businesses around creative uses of basically the same stuff:
http://www.gore.com/en_xx/products/index.html