quilterpurpledog

The burn test is certainly the most accurate to test for cotton. The others, the scrunching up test and looking to see how quickly it absorbs water, are good indicators also. If it is 100% cotton it will handle well as you work with it. Blends, because they don't wrinkle also do not crease well or press well in quilting applications. If you do a burn test be sure to wash your sample with detergent and dry before testing. This removes excess dyes and any chemical finishes applied to the fabric in the manufacturing process-they can affect the test results. Some cottons have a high percentage of polyester which will make them hard to manage in quilting and will ravel a lot. Others have just a little polyester to improve the drape of the fabric. Some people include blends in their stash because of the color values. Others just avoid them all together; I am one of those because I fear that the yarns can slip on themselves and ravel out.

Pennyhal

I use the burn test too. But I put a small piece of fabric, maybe a quarter size, in an old ashtray. I let it burn up completely. If it just cotton, you'll end up with ashes. If it is just poly, you'll end up with little hard balls. If it has both ashes and plastic, you'l know that it is a cotton/poly blend.

Wool will disolve in bleach. If you put it in bleach and it doesn't dissovle completely, you have a wool blend.

gvolle44

Along this line of testing, if you take a corner of the fabric and put in your mouth and give it a chew, cotton will appear to melt away, and non-natural fibers will feel wirey and course. The burn test looks at the ash. Chewing is quicker.

swizzy

In testing fabric with the burn test, I notice blends will usually have a dark smoke while all cotton fabrics does not

JustAbitCrazy

Easier than the burn test is the hot iron test. After washing and drying, iron on the hottest setting, which is too hot for synthetics, but not for cotton. If there is synthetic in the fabric, you will notice a pungent odor. 100% cotton never has that odor. 100% cotton has no odor, or occasionally smells sweet. If you don't know what I mean by the pungent odor, iron an article of clothing that you know is a cotton blend (by the tag). Don't use your Sunday best clothes for that.