How do I tell the content of a piece of fabric?
 

I have some fabric that I want to be sure is 100% cotton.
I suspect it has polyester in it.
I once read something about burning a piece and examining what happens to the fibers.
Does anyone know how to tell?
Or know another method?

When in doubt I just won't use it, but I would like to know.

Thanks!
Linda

Yes you can do a burn test. Just google "fabric burn test" and Bob's your uncle!

Thanks for asking this question, I have a bag of scraps given to me a couple of years ago that includes some white fabric. I really need it to finish a quilt for my GD but I suspect it isn't 100% cotton. I forgot about the "burn test". I am going to try the fabric test later today.

Essentially for the burn test, take a small scrap of fabric, light a match to it in a fire-safe container (bowl; ash tray; etc.) If it is 100% it will leave ash. If there are synthetics in the fabric, the piece will melt vs burn. Let ash/piece cool completely or soak completely with water before disposing.

I did do that search, thanks to your suggestion, and I will do a burn test before I cut and sew. Thanks for the help!

I did the burn test before Christmas and the fabric just withered and melted, so I couldn't use it. I was making the microwave potholders.

I did the test once about 15 years ago. I assume that is what the results were. NOT keen on burning small swatch of fabric !!

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.

Here's a "burn test" link I bookmarked last year. It even includes a downloadable pdf reference chart.

http://www.threadsmagazine.com/item/...hreads-eletter

One only needs a piece about 1/4 inch x 1 inch to test. I light a candle and use a tweezers to hold the fabric.

Synthrtics also burn with black smoke and leave a crunchy ash. The residue stays hot much longer than cotton ash, so resist the urge to touch it right away.