Originally Posted by JustAbitCrazy

If you don't want to do the burn test, take a close look at the frayed threads around the edges. Polyester threads are visibly thinner than cotton threads. Compare those frayed threads to those on a known 100% cotton scrap. Now iron the fabric on the hottest setting, which is fine for cotton, but too hot for synthetics. If there is polyester in there, you will smell a pungent odor. Cotton only smells fresh or has no odor at all. If you are unsure about the pungent odor I am referring to, just iron a piece of KNOWN poly/cotton to identify that smell. I never need to iron fabric to id it. Another less reliable test is to scrunch the fabric in your hand and let it go to see how much it wrinkles--poly/cottons wrinkle very little or not at all.