It's SCIENCE!

I needed some solid yellow fabric for blocks for Block Lotto, and I pulled out these pieces. Now, I knew that one of them was 100% cotton, because I bought it myself for a project from a year ago. And the other one I inherited from my mom. I remember the project my mom used the yellow for, and she is not a quilter, so I did not know what the other scrap was made of. Or which was which! So I had to figure out a way to determine the fabric content of these two specimens.

{I have to admit I love stuff like this!}

Now, I have heard other quilters refer to a "burn test" before. And I'll admit that I had no idea what that was. What do you burn? What are you looking for? Do you just burn the whole piece and then it doesn't matter what it was made of?
Here's our specimens. We'll call them lefty and righty. Same color, maddeningly enough. Lefty had a larger weave. Neither was what I'd call shiny or slick.

So I did a little checking around and figured out what I was looking for. I cut a little piece of each one and lit a candle. Then I stuck each piece in the candle and let it start to burn. (If you do this, please do it near a sink or a bowl of water. Be safe please!)
So here's the results. Lefty burned like a candle wick and went to soft ash, so it's cotton. Righty shrunk up away from the flame and left a plasticky residue when it burned on the edge in little beads, so it has synthetic fibers in it, most likely polyester.

All in all, a fun experiment!