Thank you for this information! Several years ago my youngest daughter borrowed a strapless prom dress from a friend and I sewed on some straps as she was very thin and did not have much to hold the dress up. When she was done with the dress, I tried to "unsew" the straps and could not see the stitches very well so I took the dress outside in the sun, along with one of those magnifying glass that you put around your neck. I was "unpicking" away and kept smelling some sort of burning smell - lo and behold - the dress was on fire from the magnifying glass! Not too bad though.