A few weeks ago someone wanted to be able to tell the difference in the fibers in fabric. this was in Kaye Woods newsletter this week. page 7
COTTON-When you light it, burns with a steady flame and smells like burning leaves. The ash is soft and crumbles easily. LINEN-Takes longer to light and smells like burning paper or leaves. The ash is much like a cotton ash. SILK-Burns slowly and smells like hair or feathers burning. The ash is grayish and crumbles easily. WOOL-Sputters when trying to light and smells like burning feathers or hair. The ash is black and turns to powder when crushed. ACRYLIC-Burns and melts easily and smells kind of like vinegar or something acidic. The ash remnant will be hard like a black bead. NYLON-Melts and burns slowly and smells like burning celery. The ash is like a hard gray or brown bead. POLYESTER-Melts and burns at the same time and can bond quickly to any surface it drips on. The odor is sweet and kind of fruity and the ash is like a hard, black bead. RAYON-Burns very fast and smells like burning leaves or feathers. There will be very little ash residue. ACETATE-Burns and melts easily and smells like vinegar or something acidic. The ash will be a hard, black bead.
A lot of the man made fibers, have the same distinctions and will be harder to categorize. When you try the burn test on a fabric blend, it is supposed to burn in the way each fabric would if it was an individual piece. This test is not as reliable with blends.