How to tell what kind of yarn I have?

[Pariah]

I have to big thingies of really pretty yarn, and I have no idea what type of fiber it is. Is there anyway to figure this out?

Thanks!

[Think of Winter]

What's it feel like, and what does it look like? Cotton and linen have very little elasticity, kinda like rope. If it has some stretch and recovery, the most likely fibers are wool and acrylic. A burn test can supposedly distinguish between the two, but I've tried this myself with scrap wool, and it was hard for me to tell. Basically, you burn a piece of yarn, and if it melts into a hard bead it's acrylic, and if it turns into an ash and smells like burned hair, it's wool. Try Googling "fiber burn test." There's also bleach. Apparently, wool will dissolve in bleach and acrylic will not.

You could post a pic. Someone might recognize it.

[flapjack]

I'd go with bleach before burn- I just tried the burn test on a sweater to see if it would felt and I got a beaded effect, but the sweater has felted well so it can't have been superwash :
If you can get your hands on the Yarn Harlots Knitting Rules, she has a more comprehensive list of the mystery yarn identification techniques.