The end of the year is a perfect time to set aside an hour some evening, grab a pot of hot tea, and go through your fabric stash to identify the fiber content of any unknown pieces. Here to assist is the Fabric Burn Test. Grab a holiday candle or a lighter (matches smell of sulfur), a fireproof plate (such as glass or china) and swatches from your fabric stash, and get ready to play domestic scientist! You will need to carefully observe the following; how fast is the fabric burning, what does it smell like, is there a bead or after-flame, and what sort of ash is left behind? Keep the following in mind: burn actual fabric, as the selvedge edge may not be the same fiber as the main piece of cloth and could give a false content reading. Always hold your swatch with metal tweezers, not your delicate fingers. Hold the swatch over water before setting it on fire. Do not sniff burnt fiber until the smoke dissipates. Do not touch the fabric until bead cools. All synthetic fibers should be considered to be a serious drip danger and fume hazard. If you suffer a burn, submerge you skin in ice water immediately. A burn test may not distinguish between cotton and other cellulose fibers, some fabric may have finishes that affect burn results, and weighted silk (with added chemicals) may react more like synthetic fiber.
Acetate: burns quickly, sparking and sputtering. Melts into very hot bead with burning drip danger. The odor is very much like vinegar or burning pepper. No ash. There is black smoke. Fume hazard!
Cotton: Burns very quickly with a large yellow flame. The fire will creep along the threads. The odor is like burning paper. The ash is brown grey, feathery and floats away. There is grey or white smoke.
Linen: Burns slower than cotton. The odor is similar to paper or burning wood. The ash will be dark grey and can be heavier than cotton due to thicker yarn.
Nylon: Will melt , shrink or fuse to itself. Nylon smells like beans, celery or burning string. There are hard glassy beads that cannot be crushed, and hot drip danger. Fume hazard!
Polyester: Quick burning, shrinks away from flame and may flare. Forms a round hard bead. No ash. A slightly sweet chemical odor, and black smoke. Fume hazard!
Rayon: This fiber will burn very quickly with no flame and no melting. The smell of burning rayon is similar to paper or rags. There will be little ash; it will be powdery and blacker than cotton.
Silk: Will burn slowly, the burning stops if withdrawn from the flame. The odor is like burned hair or charred meat. The residue will form round hard beads which are easily crushed. There is little smoke.
Wool/cashmere/mohair/alpaca: Has a smaller slower flame and will not flare. Wool will sizzle and curl. The odor is like burnt hair or feathers. Ash will be crisp and dark. It will crumble if crushed. There is dark smoke and moderate fume.