Silk
Silk is light, smooth and strong for its weight, but it’s damaged by sunlight and most production kills the silkworm. Here is what the sources say.
At a glance
Origin: Animal protein fiber spun by silkworms, mostly the domesticated Bombyx mori.
How processed: Natural, minimally processed: cocoons are heated to kill the pupa and soften the gum, then the filament is reeled. Eri (“peace”) silk is spun from cocoons the moth has left. No chemical dissolving.12
What it is and how it’s made
A silkworm wraps itself in a protein filament bonded by a gum called sericin. In sericulture the pupa is killed inside the cocoon by steam or hot air before it can break out, and heat softens the sericin so the filament can be unwound.1
One cocoon filament runs about 500 to 1,500 meters. It’s strong but too thin to use alone, so several are reeled together into one thread.1
Mulberry silk from Bombyx mori is about 90% of world production. The other commercial silks are tasar, muga and eri.2
China is the biggest producer and India the second; silk is under 0.2% of the global textile market.3
How it wears
| Strength | The reeled filament is continuous and very strong for its weight.1 |
|---|---|
| Sunlight | UV light breaks silk down. In one weathering test, silk fabric lost about 94% of its breaking strength after 150 days outdoors, and it yellowed.4 |
| Moisture | ASTM’s table of commercial moisture regains, used when fiber is traded by weight, lists silk at 11%.5 |
| Warmth and breathability | Studies of clothing and body temperature find construction matters more than fiber; we found none on silk garments specifically.6 |
| Odor | The odor studies we rely on cover wool, cotton and polyester, so we make no odor claim for silk.7 |
| Care | Because sunlight weakens and yellows silk, dry and store it out of direct sun.4 |
Environmental notes
- A University of Oxford life cycle study of Indian silk found most of the impact comes from producing cocoons, chiefly growing and fertilizing mulberry; cocoon drying and irrigation also mattered.8
- Footprint scorecards have ranked silk badly: PETA cites the Higg MSI rating silk worst of the fibers compared. Regulators have said Higg MSI can’t support fiber comparisons, and the coalition behind it paused consumer use.91011
Counterpoints and caveats
- Most silk production kills the silkworm: the pupa is killed with steam or hot air so the cocoon can be reeled in one piece.1
- “Peace” or “ahimsa” silk usually means eri-type silk spun from cocoons the moth has already left. We found no legal or independent definition of the term.2
- It’s fragile in sunlight, which limits it for outdoor wear.4
- Most production statistics come from the International Sericultural Commission, which promotes silk.3
Buying tips
- “100% silk,” or silk with cotton, wool or linen, is all natural. Silky fabrics labeled polyester, viscose or modal aren’t.
- If killing the pupa matters to you, look for eri or “peace” silk and ask how it was made, since the term has no standard definition.2
- Silk long underwear is thin; layer it for real cold.
Common garments
- Ties and pocket squares
- Shirts and camp shirts
- Thin base layers and long underwear
- Knitwear blended with wool or cotton
Short answers
- Is the silkworm killed to make silk?
Usually, yes. In standard sericulture the pupa is killed with steam or hot air before it emerges, so the cocoon can be reeled as one filament.12
Counterpoint: Eri silk lets the moth emerge first and is spun instead of reeled.
- Why does silk fade or weaken?
UV light breaks down the silk protein; a weathering test found heavy strength loss and yellowing.4
Counterpoint: Months outdoors is far harsher than normal wear.
Where to find it
Scored brands have a natural-fiber share score; picks pages list specific products and are not scored.
We don’t list a brand or picks page for this yet.
Sources
Industry-funded, trade-body and advocacy sources are flagged. Product labels read October 31, 2026.
- 1Food and Agriculture Organization of the United Nations. Silk reeling and testing manual, chapter 1. FAO Agricultural Services Bulletin, 1999.
- 2International Sericultural Commission. Types of silk. Web page, current page. Intergovernmental body that promotes the silk industry.
- 3International Sericultural Commission. Statistics: global silk industry. Web page, current page. Intergovernmental body that promotes the silk industry.
- 4Ming, Jiang, Zuo. Natural and artificial weathering of B. mori silk fabric. Advanced Materials Research, 2011.
- 5ASTM International. Standard tables of commercial moisture regains and commercial allowances for textile fibers (D1909). Standard, 2020.
- 6Gavin. Clothing and thermoregulation during exercise. Sports Medicine, 2003.
- 7Laing (University of Otago). Natural fibres in next-to-skin textiles: current perspectives on human body odour. SN Applied Sciences, 2019.
- 8Astudillo, Thalwitz, Vollrath (University of Oxford). Life cycle assessment of Indian silk. Journal of Cleaner Production, 2014.
- 9PETA. First-ever alpaca wool exposé: workers tie up, stretch out, and cut animals. Press release, 2020. Animal-rights advocacy group that opposes all animal fibers.
- 10Norwegian Consumer Authority, with the Netherlands ACM. Consumer authorities issue guidance on environmental claims to the textile industry. Regulator guidance, 2022.
- 11Sustainable Apparel Coalition (now Cascale). Statement from the SAC regarding the Norwegian Consumer Authority and environmental claims. Industry statement, 2022.
Updated October 31, 2026. All fiber guides · Why the label matters