How To · Fashion · Fabrics
The Burn Test: A Guide to Fiber Identification
Labels fade and tags are often misleading, but the physics of fiber doesn't lie. This is how to determine exactly what you are wearing.
5 min read · IrisIn an era of clever marketing and 'vegan leather' euphemisms, the tactile experience of fabric is often secondary to the label. However, understanding your wardrobe's DNA is the first step toward better garment care and smarter curation.
If you have a mystery vintage find or a garment with a missing tag, you don't need a lab. You need a pair of tweezers, a heat source, and a keen eye for how fibers respond to fire.
Natural fibers return to the earth; synthetics simply retreat from the flame.
Step one · 1 minute
The Source Selection
Locate a hidden seam or an interior hem where you can safely extract a single thread or a tiny swatch. Do not attempt this on the garment's visible face. You only need about two inches of thread to conduct a reliable test.
Always prioritize a single thread over a swatch to minimize damage.
Step two · 1 minute
The Approach
Hold the fiber with your tweezers and slowly move it toward the edge of a flame—a lighter or a candle works best. Do not plunge it into the fire immediately; observe how the fiber reacts as it nears the heat. Synthetics will often shrink or curl away from the flame before touching it.
Perform this over a non-flammable surface like a ceramic sink.
Step three · 1 minute
Observe the Ignition
Touch the fiber to the flame. Natural fibers like cotton and linen will ignite immediately, burning with a steady, bright flame. Synthetics, conversely, will melt, hiss, and sputter, often forming a hard, plastic-like bead at the end.
If it smells like burning hair, you are likely holding protein-based wool or silk.
Step four · 1 minute
The Scent Test
The olfactory evidence is the most accurate indicator. Burning cellulose (cotton, linen, rayon) smells like burning paper or wood. Burning protein (wool, silk) smells distinctly like singed hair. Burning synthetics (polyester, nylon) smells like chemicals or melting plastic.
Take a quick, cautious sniff immediately after extinguishing the flame.
Step five · 1 minute
The Ash Analysis
Once the flame is out, examine the residue. Cotton and linen leave behind a fine, powdery grey ash that crumbles easily between your fingers. Synthetics leave a hard, dark, irregular bead that cannot be crushed.
Wait at least 30 seconds for the residue to cool before touching.
How to know it works.
You have successfully identified the fiber if the physical reaction (melting vs. burning) and the scent profile align with the expected characteristics of the suspected material.
Questions at the mirror.
What if it's a blend?
Blends will show mixed results. If a fabric is 60% cotton and 40% polyester, you will likely see a partial melt and a partial ash, often with a chemical scent masking the paper scent.