How to Identify Any Fabric: The Burn Test, Step by Step

You've inherited a mystery bundle from a destash, found an unlabelled remnant at the bottom of your stash, or bought a beautiful piece at a market with no fibre content in sight. Before you cut into it — or worse, iron it on the wrong setting — you need to know what it actually is. The burn test is the closest thing sewing has to a forensic lab, and you can do it at your kitchen sink in five minutes.

What the burn test actually tells you

Every fibre family burns differently. Natural plant fibres like cotton and linen burn like paper, because chemically they nearly are. Animal fibres like wool and silk burn like hair. Synthetics like polyester and nylon don't really burn at all — they melt. Watch how a small snippet behaves near a flame, and the fabric identifies itself: by how it burns, how it smells, and what it leaves behind.

Safety first — this is non-negotiable

Work over a sink or a metal tray, never near your fabric stash or curtains. Hold the snippet with metal tweezers or pliers, never your fingers — synthetics drip molten polymer when they melt, and those drips stick to skin. Have water within reach, tie back long hair, and do this away from children and pets. You need a piece no bigger than a postage stamp; cut it from a corner or seam allowance.

The method

Hold the snippet with tweezers and bring it slowly towards a small flame — a lighter or a candle. Note what happens as it approaches, in the flame, and after you remove it. Then smell the smoke cautiously and examine the residue once cool. Four clues, one verdict.

Reading the results

Cotton and linen ignite quickly with a steady yellow flame, keep burning when removed, and smell exactly like burning paper or leaves. The residue is a soft, feathery grey ash that crumbles to nothing between your fingers. Linen burns slightly slower than cotton. If this is your result, you're holding a plant fibre — wash warm, iron hot, sew with confidence. Browse our cotton fabrics if you've fallen for the type.

Wool is reluctant to ignite, sputters and often self-extinguishes when removed from the flame, and smells unmistakably of burning hair. The residue is a dark, crushable bead — gritty, not glassy. Silk behaves similarly (it's also a protein fibre) but with a milder smell, sometimes compared to charred meat, and a black bead that crushes to powder.

Polyester shrinks away from the flame before melting rather than burning, produces black smoke, and smells faintly sweet and chemical. It leaves a hard, round, glassy bead you cannot crush. Nylon also melts rather than burns but smells of celery — genuinely, celery — and leaves a hard grey-brown bead.

Viscose and rayon trick people: they're man-made but from plant cellulose, so they burn fast like cotton with the same papery smell and soft ash — often even faster, with little to no afterglow bead at all. Our viscose collection is full of exactly this lovely, breathable chameleon.

The blend problem

Most modern fabrics are blends, and a poly-cotton will give you mixed signals: it burns and melts, smells of paper and chemicals, and leaves ash with hard beads embedded in it. That mixed verdict is itself the answer — you have a blend, and the dominant behaviour hints at the dominant fibre. Stretch fabrics complicate things further: the few percent of elastane in a stretch fabric is usually too small to read in a burn test, so test the base fibre behaviour and assume the stretch comes from elastane.

Why it matters for your sewing

Fibre content decides everything downstream: your iron temperature (polyester scorches and glazes at settings cotton shrugs off), your washing routine, your needle choice, and whether the garment will breathe on an August afternoon. Five minutes at the sink saves a ruined project later.

Found out what your mystery fabric is — or decided to skip the mystery entirely? Every fabric at Fabriques lists its full fibre content on the product page, with samples from £1.49 so you can feel before you commit. Start at All Fabrics and filter by fibre.