Wool
Natural protein fiber from the fleece of sheep. Scale-and-crimp architecture traps insulating air, absorbs moisture vapor without feeling wet, and provides near-complete wrinkle recovery. Choose wool for temperature regulation and odour resistance; avoid when fast drying or hot-wash care is required.
When to Choose Wool
- Tailoring & Suiting: highly suitable
- Outerwear: highly suitable
- Upholstery & Home: highly suitable
Common Uses
Technical Profile
| Fiber Class | Natural protein fiber |
Decision Summary
Choose wool when you need natural temperature regulation across varying activity levels, wrinkle recovery without ironing, and odour resistance over multi-day wear. Avoid wool when pack weight matters more than warmth, or when machine washing at standard temperature is required without Superwash treatment.
Why Wool Behaves the Way It Does
Wool's defining properties trace to a layered fiber architecture. The cortex — roughly 90% of fiber mass — consists of interlocking helical keratin chains in a bilateral arrangement that generates natural three-dimensional crimp. Surrounding the cortex, overlapping cuticular scales point toward the fiber tip. When agitated in warm water, directional scale movement causes adjacent fibers to migrate and lock permanently — the mechanism behind felting.
The crimp creates a molecular spring that traps still air between coils and enables absorption of 14–18% of fiber weight in moisture vapor before the fabric feels wet [1]. Critically, the absorption is exothermic: the heat of sorption releases warmth during moisture uptake, which is why damp wool can feel warmer than dry synthetic insulation of similar weight. This dual thermal and moisture function explains wool's performance across activity levels and temperatures that no synthetic fiber replicates.
Technical Profile
| Property | Fine Merino (17–22 µm) | Crossbred (25–36 µm) | Why it matters |
|---|
|----------|----------------------|---------------------|---------------|
| Fiber diameter | 17–22 µm [2] | 25–36 µm | Prickle threshold ~22 µm; determines next-to-skin wearability |
|---|---|---|---|
| Tensile strength | 9–16 cN/tex [3] | 10–18 cN/tex | Lower than cotton; offset by high elongation recovery |
| Elongation at break | 25–35% [3] | 25–40% | High elasticity = near-complete wrinkle recovery at room temperature |
| Moisture regain | 14–18% at 65% RH [1] | 14–18% | Absorbs moisture vapor without feeling wet |
| Felting threshold | >40°C with agitation [4] | Same | Wool/delicate cycle essential; Superwash treatment enables hot wash |
| Thermal conductivity | ~0.036 W/mK [5] | ~0.040 W/mK | Low conductivity = effective thermal insulation |
Use-Case Matrix
| Application | Grade / diameter | Why wool works | When to reconsider |
|---|
|-------------|-----------------|----------------|-------------------|
| Base layers (next-to-skin active) | Fine Merino 17–19 µm | Soft; moisture-wicking; odour-resistant over multi-day use | Polyester is cheaper and dries faster |
|---|---|---|---|
| Dress suiting | Fine Merino 18–22 µm | Natural drape; wrinkle recovery; breathability | Less abrasion-resistant than polyester blend |
| Mid-layer knitwear | Fine–Medium 20–28 µm | Thermal regulation; natural loft without synthetic look | Cashmere preferred at premium price points |
| Outerwear coating | Crossbred 28–36 µm | Durability; weather resistance; structural body | Synthetic insulation is lighter per warmth unit |
| Socks | Fine–Medium Merino blend | Blister prevention; moisture management | Pure wool wears through at heel; add nylon reinforcement |
When Wool is Not the Right Choice
| Need | Better alternative | Why |
|---|
|------|------------------|-----|
| Machine wash at 60°C | Polyester | Wool felts above 40°C without Superwash treatment |
|---|---|---|
| Maximum abrasion resistance | Nylon or polyester | Wool's scale surface wears at friction points (heel, elbow) |
| Chlorine or saltwater exposure | Polyester | Chlorine degrades wool keratin permanently |
| Lowest cost per garment | Cotton or polyester | Wool carries a significant retail price premium |
Care Summary
| Method | Rule |
|---|
|--------|------|
| Machine wash | Wool/delicate cycle, ≤30°C, slow spin; Superwash-treated wool: 40°C |
|---|---|
| Dry | Lay flat; do not hang wet knits (weight stretches the structure) |
| Iron | Steam only; wool cycle (≤150°C) |
| Store | Fold flat; never hang knitwear long-term |
Sources and References
[1] Morton, W.E. & Hearle, J.W.S., Physical Properties of Textile Fibres, 4th ed. Woodhead Publishing. Heat of sorption and moisture regain values.
[2] International Wool Textile Organisation (IWTO), Fiber Diameter Measurement Standards. IWTO-12 protocol.
[3] Hatch, K.L., Textile Science, West Publishing. Tensile strength and elongation data for wool grades.
[4] Wortmann, F.J. & Höcker, H., Advanced Wool Textile Technology. Felting threshold conditions.
[5] Frydrych, I. & Dziworska, G., Thermal Comfort Properties of Wool Fabrics. Conductivity data.
Buy Wool Fabric
- Cashmere Wool Suit Fabric — Premium Suiting Weight
- Abraham Moon 50% Wool Blend — British Heritage Tweed
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