Down is an animal cluster: filaments radiating from a nucleus, a dandelion of trapped air. Synthetic fill is polyester (or other man-made fibre) doing a similar job with crimp and hollow sections. “Down cotton,” “silk down,” “feather silk” on a hangtag is almost always polyester, sometimes mixed with pulverised feather. The China Feather and Down Industrial Association has spent years saying that out loud. If the fill is not down, do not write down.
TrimGem will quote both constructions. The fibre name on the label is the legal line.
What down is
A cluster holds still air. More clusters, more warmth per gram, more money. Down fibres and feather fibres that have broken off are not clusters. Products stuffed with pulverised feather plus polyester, marketed as “down silk,” can test under 1% down cluster. They are cheap, poor insulators, and sometimes an irritation and hygiene problem.
What “down cotton” is
Polyester engineered for loft: fine denier (good lots <1.2 D), high void, 3D crimp, void fraction claimed above 85% on better lots. Soft, light, washable, low odour, fast dry. Ski and city jackets use it honestly. It is not a down cluster. Fill-power talk on polyester (sometimes 450–550 “equivalent,” or a centimetre loft) is a marketing translation. Real fill power is a down method (next note).
Trade-offs
- Down: best warmth-to-weight when dry; comfort; cost; can leak through a poor shell; professional clean or careful wash; loses loft when soaked unless treated.
- Polyester fill: cheaper, wet-tolerant, no animal story, easy care, less warmth per gram than good down, especially in serious cold and wind. Better than bad “fake down” that is pulverised feather.
Chemistry: protein vs PET. Allergies and ethics sit on that line, not on a photo of a goose.
Law and labels
GB/T 14272-2021 (down apparel): a down garment is filled with down; down cluster content ≥50%; duck vs goose and fill weight must be stated. “Down cotton” does not meet that definition.
Older Chinese language used “down content” that could include fibres. The newer emphasis is cluster content. IDFB communication has also tightened when the word “down” may be used (cluster thresholds on labels and web copy). If you export, follow the market’s down-labelling rule, not a factory nickname.
How to buy without the trap
Look: mill, fibre, species + cluster % + fill weight, care, standard number. If the hangtag says down-cotton / feather-silk, it is not down.
Feel: some small feathers in a down mix are normal; powder clouds and itchy dust are not; rubbing should not snow fibre through a claimed down-proof shell.
Smell: sour or chemical is a hygiene or formaldehyde conversation.
Write down (goose/duck, cluster %, fill power, fill weight) or polyester (dtex, gsm or grams, bonded or loose). Synthetic fill is a legitimate TrimGem family. Counterfeit down wording is not a family. It is a labelling failure.