ckcowl

there are different invisible threads on the market- you want a poly one- not a nylon---the nylon is the one that melts- with time will become brittle- and when it breaks gives you those poky ends--like you find on some shirt tags that will drive you insane.
visit Superior threads web site and read about the different threads- weights, properties and uses before spending your money on a thread you may not be happy with.