Interesting thread. I would recommend that you check with Dr. Bob at Superior Threads. He provides a wealth of information that is well documented. I personally would not use nylon for any technique because of its low melting point-think ironing and pressing. Polyester is a much better choice and comes in many forms for many uses. I personally prefer Bottom Line in beige or gray if I want an invisible appearance. I frequently use it in the bobbin with a cotton thread on the top. It always looks good.