How to tell real silk from synthetic satin

Identifying genuine mulberry silk from synthetic satin requires either access to the garment in person or a reliable specification from the vendor. The methods below are applicable when shopping in person — at a boutique, a market, or when assessing a vintage or pre-owned piece.

The burn test

This is the most definitive test for fibre identification, but requires access to a loose thread or a small snip from a seam allowance.

Method: hold a short length of thread (2–3 cm) with tweezers or tongs and apply a flame briefly.

Silk (protein fibre): burns slowly, with a small flame that self-extinguishes when removed from the heat source. Smells distinctly of burning hair or horn — the characteristic smell of burning protein. Leaves a crushable, powdery black ash.

Polyester (synthetic fibre): melts rather than burns. Produces a drip of molten material, smells of burning plastic or sweet chemicals, and leaves a hard, brittle, fused bead rather than an ash.

Cotton/modal/cellulosic fibres: burn more readily than silk, continue burning after the heat source is removed, smell of burning paper or wood, and leave a soft grey ash. Not easily confused with silk.

The burn test distinguishes protein fibres (silk, wool) from synthetic fibres (polyester, nylon) and from cellulosic fibres (cotton, linen, modal) clearly.

The ring test

Method: form a ring by touching thumb and index finger, creating an opening of about 1 cm diameter. Pull a small section of the fabric through the ring.

Silk: passes through a small ring with minimal resistance because the smooth, fine filaments have very low friction against each other and against skin. Moves fluidly.

Polyester satin: bunches, catches, and creates more resistance passing through the same ring because the filaments have slightly higher surface friction and the weave resists the compression.

This test is less definitive than the burn test — fine polyester and silk can feel similar — but it provides a useful additional data point when a burn test is not possible.

The feel test

Method: place the fabric flat against the back of your hand for thirty to sixty seconds.

Silk: is cool to the touch and warms quickly against skin, taking on the body temperature within thirty to sixty seconds. The transition from cool to warm is the distinctive quality.

Polyester satin: feels warm at first touch — it does not have the initial coolness of silk — and does not change temperature significantly after contact.

This test is reliable for distinguishing silk from polyester satin in casual assessment. It is less reliable in very warm rooms or when both hands are warm.

Online purchasing

None of these tests applies to online buying. For online purchases, the only reliable indicators of genuine silk are:

1. Explicit fibre specification: "100% mulberry silk" or "100% silk" with a momme weight stated
2. Care label specification confirming dry-clean or hand-wash only with silk-appropriate detergent
3. Price point: genuine 16-momme silk at a boutique price is not inexpensive; if the price feels too low for what is claimed, it usually is

For more on reading product specifications, see buying lingerie online — what to check. The materials guide covers fibre identification in the full fabric context.