I used silk once to sew down the binding but it kept breaking--sure is silky to the touch though!. For your applique, i do think it would be ok, or a #60 poly like Superior MicroQuilter. But you might also try Superior's or YLI's invisible thread. Be sure to use a thread net to keep it from spooling off too fast and a smaller needle as it's super fine. superior's has both totally clear and a smoky clear for darks. that is usually what I use if I have multiple colors to work on.