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.