I have some mystery white yardage in my stash. I don't remember what it is, I was wondering if there was any way to tell if it was cotton or a cotton/poly blend?

Snip off a little piece & give it the burn test. If it smell like burning leaves or paper and leaves Soft, Lacey & Gray Ash - Easily Crushed, then it's cotton.

here's a chart: http://www.ditzyprints.com/dpburnchart.html

bonus - youtube video http://www.youtube.com/watch?v=kb4tCcnA6jo

Do a burn test. Cut a small piece and set fire to it. If it is cotton you will just have white ash. If it's poly it will smoke and you'll end up with a hard melted piece.

YES! basically the same kinda thing as testing for mystery yarn (i do alot of knitting). THanks Ladies!