I have used Aurifil invisible thread since I started quilting 5 years ago. At the time I started using it, I did not know that the thread was made from nylon. I have enjoyed using this nylon thread and have never had a problem with it. Frequently, I draw a design with a Frixion pen (I know many people don't like these pens), quilt it with the Aurifil thread, then, with my iron on cotton, use steam to remove the Frixion markings. So far, I have never melted the thread. Maybe I have just been lucky. At any rate, some of the quilts have been washed many times and the invisible thread that I used for quilting is holding up well. I'll be honest, if I had known that the Aurifil thread was nylon, I would not have bought it; but I am very, very pleased with it and enjoy FMQ with Aurifil invisible thread.