Fabric burn test: how to tell cotton, polyester, wool and silk apart
A burn test is the most reliable way to tell fiber families apart at home. Plant fibers, animal fibers and synthetics each behave differently in a flame, smell different and leave different residue. It won’t give you exact percentages, but it will tell you whether you’re holding cotton, wool or plastic.
Safety first
- Work over a sink, a metal tray or a glass dish, away from anything flammable.
- Use a small snippet (about 1 × 2 inches, or 2 × 5 cm) or a few yarns pulled from a seam allowance.
- Hold it with metal tweezers or tongs, never your fingers.
- Keep water nearby, ventilate the room, and keep children and pets away.
- Synthetics melt and can drip. Don’t touch the residue until it has cooled.
How to do it
- Bring the edge of the snippet slowly toward the flame. Watch whether it curls or shrinks away before it touches.
- Put it in the flame and watch how it burns: steadily, slowly, or melting.
- Take it out. Does it keep burning, glow, or go out by itself?
- Waft the smoke toward you to smell it, rather than breathing it in directly.
- Let the residue cool, then rub it between your fingers: soft ash, a crushable bead or a hard bead?
Burn test chart
| Fiber | Near the flame | In the flame | Smell | What’s left |
|---|---|---|---|---|
| Cotton | Doesn’t shrink away | Burns quickly with a yellow flame; may glow afterward | Burning paper or leaves | Fine, soft gray ash |
| Linen | Doesn’t shrink away | Burns like cotton, a little slower to catch | Burning paper or grass | Soft gray ash |
| Rayon (viscose) | Doesn’t shrink away | Burns fast and bright | Burning paper | Very little soft ash |
| Wool | Curls away | Burns slowly, sputters, often goes out by itself | Burning hair | Dark, crumbly bead you can crush |
| Silk | Curls away | Burns slowly, often goes out by itself | Burning hair | Dark bead you can crush |
| Polyester | Shrinks away and melts | Melts and burns, often with dark smoke | Sweet or chemical | Hard dark bead you can’t crush |
| Nylon | Shrinks away and melts | Melts and may drip | Like plastic | Hard tan or gray bead |
| Acrylic | Shrinks away and melts | Burns readily, melts and may drip | Sharp and acrid | Hard, irregular dark bead |
Reading blends
Most real fabrics are blends, and they give mixed signals. Some soft ash plus a hard melted edge usually means a natural fiber blended with a synthetic, such as a cotton-poly. You can tell that a synthetic is there; you can’t tell the ratio. If the exact percentage matters, the label is the only reliable source.
Wovens: test both directions
The lengthwise (warp) and crosswise (weft) threads can be different fibers, such as a cotton warp with a polyester weft. Pull a few threads from each direction and burn them separately.
When you’d rather not burn it
For a quilt top, a finished garment or an heirloom, you may not want to cut a sample. Fabric Identifier gives a likely answer from a photo, including the fabric name, the likely fiber content and the weave, with no snippet needed. It’s a first guess from what the camera sees, so where the fiber really matters, a burn test on a hidden seam allowance is still the stronger check.