A simple method for identifying the composition of garment fabrics is the burn test. To perform it, pull a small strand of fabric containing both warp and weft threads from the seam edge, ignite it with a flame, observe the characteristics of the burning flame, smell the odor emitted as the fabric burns, and examine the residue left behind. By comparing these observations with the fabric composition listed on the garment’s care label, you can determine whether the stated composition is accurate and verify the authenticity of the material.
I. Cotton Fiber and Linen Fiber Both cotton fiber and linen fiber ignite readily upon exposure to flame, burn rapidly, produce a yellow flame, and emit blue smoke. The differences between the two in terms of odor during combustion and the nature of the resulting ash are as follows: cotton burns with a paper-like odor, whereas linen burns with an odor reminiscent of plant ash; after burning, cotton leaves behind a very fine black or gray ash, while linen yields a small amount of off-white ash.
II. Wool Fiber and Silk When exposed to flame, wool produces smoke, forms bubbles as it burns, burns relatively slowly, and gives off a pungent odor reminiscent of burning hair. The resulting ash consists mainly of glossy, black, spherical particles that crumble easily when pressed between the fingers. Silk, when ignited, shrinks into a clump, burns slowly with a hissing sound, and emits an odor similar to scorched hair. After combustion, it leaves behind small, dark brown–black, spherical ashes that disintegrate readily when rubbed between the fingers.
III. Nylon and Polyester Nylon, chemically known as polyamide fiber, rapidly shrinks and melts into a white, glue‑like mass when exposed to a flame. It burns with dripping and bubbling, producing no visible flame; once removed from the flame, it is difficult to sustain combustion. It emits an odor reminiscent of celery, and the light brown molten residue that forms upon cooling is not easily crushed. Polyester, chemically known as polyester fiber, is readily ignited and begins to melt and shrink near a flame. During combustion, it melts while emitting black smoke, burning with a yellow flame and giving off a characteristic aromatic odor. The resulting ash is a hard, dark brown lump that can be crumbled between the fingers.
4. Acrylic and Polypropylene Fibers Acrylic fiber, chemically known as polyacrylonitrile fiber, softens and shrinks when exposed to heat; when ignited, it produces black smoke and a white flame, continuing to burn rapidly after the flame is removed while emitting a pungent, meat‑like odor. The resulting ash consists of irregular, hard, black lumps that crumble easily when rubbed between the fingers. Polypropylene fiber, chemically known as polypropylene fiber, melts and shrinks upon contact with a flame; it is highly flammable, burning slowly after the flame is removed and producing black smoke. The upper portion of the flame is yellow, with a blue tip, and it gives off an oil‑like odor. The ash formed after combustion comprises hard, round, light yellow‑brown particles that crumble readily when pinched.
5. Vinylon and Chlorine Fiber Vinylon, chemically known as polyvinyl alcohol‑formaldehyde fiber, is difficult to ignite; it melts and shrinks near the flame. When burning, a small flame appears at the tip, which grows larger as the fiber melts into a viscous mass, producing thick black smoke and a bitter, pungent odor. After combustion, it leaves behind small, black, bead‑like particles that can be crushed with a finger. Chlorine fiber, chemically known as polyvinyl chloride fiber, is highly resistant to burning; it extinguishes immediately upon removal from the flame. Its flame is yellow, with greenish‑white smoke issuing from the lower end, accompanied by a sharp, irritating, acrid, and acidic odor. The resulting ash is a hard, irregular, dark brown‑black mass that is difficult to crush between the fingers.
6. Spandex and Fluorinated Fibers Spandex, chemically known as polyurethane fiber, melts and burns when exposed to flame; the flame is blue, and it continues to melt and burn after being removed from the flame, emitting a distinctive pungent odor. The resulting ash is soft, fluffy, and black. Fluorinated fiber, formally called polytetrafluoroethylene fiber—referred to by ISO as “fluorite fiber”—only melts in the presence of a flame, is difficult to ignite, and does not sustain combustion. Its edge flame appears bluish‑green and carbonizes; it decomposes upon melting, releasing toxic gases, and the molten residue forms hard, round, black beads. In the textile industry, fluorinated fibers are commonly used to produce high‑performance sewing threads.
7. Viscose Fiber and Cuprammonium Fiber Viscose fiber is highly flammable, burns rapidly, produces a yellow flame, and emits a smell reminiscent of burning paper. After combustion, it leaves little ash, in the form of smooth, twisted, light‑gray or gray‑white fine powder. Cuprammonium fiber, commonly known as “tiger kapok,” ignites almost immediately upon exposure to flame, burns quickly with a yellow flame, and gives off an ester‑acid odor. It leaves very little ash—only a small amount of dark gray residue.