Fiber Comparison
Wool vs. cotton, synthetics and down.
No fiber wins everything. Wool's strengths are staying warm when damp, resisting odor and not burning easily. Synthetics win on drying speed and abrasion, and down wins on warmth for its weight when it's dry.
REF-01
Side-by-Side
| Wool | Cotton | Polyester / fleece | Down | |
|---|---|---|---|---|
| Warmth (dry) | High | Low | High | Highest for its weight |
| Warmth when damp | Good | Poor | Good | Poor unless treated |
| Moisture it can absorb | A lot, as vapor | A lot, feels wet | Very little | Clumps when wet |
| Drying speed | Slow | Slow | Fast | Slow |
| Odor resistance | Very good | Fair | Poor | Good |
| Abrasion resistance | Moderate | Moderate | Good | n/a (shell) |
| In a fire | Chars, self-extinguishes | Burns | Melts and drips | Burns |
General comparisons; blends, weaves and treatments change the details.
REF-02
Why Wool Stays Warm When Damp
- It absorbs moisture as vapor: wool can take up a large share of its own weight in water vapor before it feels wet, pulling sweat away from skin.
- It releases heat as it absorbs: when wool takes up moisture it gives off a small amount of heat, which slows the chill of damp clothing.
- Crimp keeps loft: wool's spring keeps air trapped in the fabric even when damp. Cotton collapses and holds liquid water against the skin.
REF-03
Odor & Fire
- Odor: wool absorbs odor molecules and gives bacteria less to work with on the surface, so it can be worn many times between washes. Polyester tends to hold onto smells.
- Fire: wool has a high ignition temperature, a high moisture and nitrogen content, and tends to char and self-extinguish rather than melt. That's why it's used for firefighter and military layers and aircraft upholstery.
REF-04
When to Choose What
| Situation | Best pick |
|---|---|
| Cold, wet, or variable weather | Wool, or wool over a synthetic base layer |
| Multi-day trips without washing | Merino wool |
| High output, sweat, fast drying | Synthetic base layer, wool midlayer |
| Maximum warmth, dry cold, lightweight | Down jacket |
| Around campfires, sparks or stoves | Wool outer layer |
| Hot, dry everyday wear | Cotton or lightweight merino |