Pair this with choosing fabric. The bolt end and the care tag are paperwork. Feel and flame are only backups when the paperwork is missing or you distrust a mystery remnant.
Read the label
The FTC’s Textile and Wool Acts require most textile products to name fiber content with generic names, country of origin, and a responsible business. Manufactured fibers must use generic names (polyester, nylon, rayon), not a trademark standing alone. Fibers at 5% or more by weight are named in order of predominance; 5% or less is usually “other fiber,” unless that sliver has a definite function (elastane in a stretch woven is the usual example). The FTC allows about a 3% tolerance on the stated percentages. Not a license to invent cotton.
The Care Labeling Rule (16 CFR 423) is a different label: washing or drycleaning instructions for wearing apparel. FTC “Clothes Captioning”: a minimum wash line is a method of washing and a method of drying, such as “Machine wash. Tumble dry.” That tells you how the garment was meant to live. It does not name the fiber. Use both tags when they exist.
Worktable orderContent tag → care tag → hand → optional burn on a waste yarn. Do not torch the only eight inches of a dead-stock silk.
Feel
Plant (cellulose: cotton, linen, rayon): often cooler, wrinkles, a paper-dry catch on linen. Protein (wool, silk): wool springs and smells faintly animal when wet; silk is fine, cool-smooth, loud when it is raw. Synthetics (polyester, nylon): often slick or waxy, hold a crease less, may feel warmer in a dense weave. Sewing.org’s fiber guideline still starts by sorting animal / vegetable / synthetic before any flame.
Burn, if you must
CCI Notes 13/18: a burn test distinguishes plant cellulose from animal protein. It is not usually the sole method. Sewing.org 4.107 and CCI agree on the split:
| Class | In / after flame | Smell | Residue |
|---|---|---|---|
| Plant (cotton, flax, rayon) | Does not shrink away; burns readily; afterglow | Burning paper, leaves, or wood | Fine grey or white ash |
| Protein (wool, silk) | Shrivels; slow; often self-extinguishes | Burning hair | Dark bead, easy to crush |
| Many synthetics (polyester, nylon) | Melt, drip, may self-extinguish | Sweet chemical or plastic | Hard, dark bead |
ACS classroom note: cotton smells like paper because both are cellulose; polyester shrinks, smells sweet-chemical, leaves a hard bead. Fumes from synthetics are not a parlor trick. Ventilate. Tweezers, a scrap, a non-flammable dish, and a way to put it out. Weighted silk (CCI) can char and hold shape instead of burning; do not call that “not silk” from one bead.
ACS again: coatings and mixed fibers throw the test. A cotton/poly shirting will give you both paper-ash and melt. Treat a mixed result as “blend, unknown ratio,” then sew a wash test.
No extra “fiber-ID kit” of gadgets. The tools are the tag, your fingers, and optionally a flame on waste yarn. Cutting tools live on the shears and mat kit.