Here is a
link to previous discussions on the topic. It happens to be the thread in which Knotty first posted. I was interested to see the evolution in positions of all of us since then. That is the thread where I used silk for my very heavy pearls and went on the hunt for an alternative.
As for drape, there is no difference in drape in a bracelet or necklace between silk and other threads. Even a very long rope can't be discerned as draping better with silk. I used silk to knot for years, until I tried to knot the Lumps of Coal necklace. Now I see its limits and I prefer Power Pro for everything. I strung my Bahraini pearls with it and they seem to like it just fine. And even if I catch it on something and pull before I realize it, it will not break. The pearls range from 1mm to 7mm and I knotted between each one. It drapes better with knots than without.
Steve,
Paspaley uses nylon. It does not fray like silk- however silk is prepared. It does not need glue. (Silk doesn't either, but most people don't seem to know that, even the best professionals.) I would not presume to tell you what thread to use, but I am sure you will look at the alternatives for yourself. The linked thread is quite interesting and has a lot of info. Several of us have been exploring threads for the last year -and sharing as we go.