Originally Posted by redmadder
Fabric content test: Cut a very small piece, maybe 1 inch by 1/4 inch. Hold with tweezers, light it on fire. (best do this over the sink).
Black smoke and a hard ash mean its synthetic or a blend. Smells like plastic burning.
Gray smoke and a fine, soft ash mean its plant fiber. And the smell of burning cotton is very distinctive.
I always roll the ash in my hands (allow a minute or so to cool), 100% natural fibers will be like powder, if any lump, then it is at least partially synthetic. If it's 100% synthetic you will probably just see the black lump, & no ash at all. I do mine over a metal tin or glass ashtray over the laundry sink in my garage, water handy, just in case.