How to identify a vintage fabric

The fibre timeline

Each fibre below has a hard earliest-possible date of commercial introduction. Finding the fibre means the garment is post-that-date.

The burn test — by fibre type

The burn test is the single most reliable at-home fibre identification method. Pull a thread of about an inch from an interior seam. Hold it with tweezers in a flame; observe how it burns, how it smells, and what residue remains. Never burn a thread from a valuable piece — only from an interior seam allowance.

• Cotton: Burns rapidly with a yellow flame. Smells like burning paper. Leaves a fine grey ash that crumbles when pinched.
• Linen: Burns similarly to cotton but slightly more slowly. Smells like burning paper. Grey ash.
• Wool: Burns slowly, often self-extinguishes. Smells unmistakably like burning hair. Leaves a black crumbly residue that crushes into a fine powder.
• Silk: Burns slowly, often self-extinguishes. Smells like burning hair (similar to wool but lighter). Leaves a brittle black bead that crumbles.
• Rayon / viscose: Burns rapidly with yellow flame. Smells like burning paper (similar to cotton). Leaves a very fine grey ash.
• Nylon: Melts and beads before burning. Smells like celery (slightly sweet, chemical). Leaves a hard grey-black bead.
• Polyester: Melts and beads. Smells sweet, slightly chemical. Leaves a hard dark bead that does not crush.
• Acrylic: Melts and burns with a black smoky flame. Smells acrid. Leaves a hard black irregular bead.
• Acetate: Melts and burns. Smells like vinegar. Leaves a hard dark bead.
• Spandex / Lycra: Burns and melts with a chemical smell. Often appears as a thin elastic thread alongside the main fibre.

The hand test — by feel

Experienced dealers identify many fibres by touch alone. The relevant variables are temperature (silk and linen feel cool; wool and cotton feel warm), drape (silk and rayon drape fluidly; cotton and linen drape stiffly), and surface (silk has a soft sheen; rayon a duller sheen; polyester a slick artificial sheen). The hand test is faster than the burn test but less reliable for fakes.

Weighted silk and its destruction

Silk fabric was routinely 'weighted' — treated with metallic salts (often tin or iron) — from the mid-nineteenth century through the 1930s. The treatment added body, drape, and apparent quality, but the metals catalyse fibre degradation over time. Weighted silk eventually 'shatters': splits along fold lines, cracks at stress points, and disintegrates in your hand. Any Victorian, Edwardian, or pre-1930s silk garment that splits when gently folded is weighted silk in late-stage deterioration. The damage is irreversible. Never wet-clean weighted silk; the water accelerates the chemical breakdown.

Microscope identification

If you have access to a microscope (40× or higher), fibre identification becomes almost unambiguous. Cotton fibres look like flat twisted ribbons. Linen fibres look like bamboo, with periodic 'nodes' along their length. Wool fibres show overlapping scales. Silk fibres are smooth, transparent, almost glass-like rods. Synthetic fibres are typically perfectly uniform rods or have characteristic cross-sections (polyester is often trilobal). For collectors handling thousands of dollars of vintage, an inexpensive USB microscope is a worthwhile tool.