Silk
Natural protein fiber produced by silkworm (Bombyx mori) cocoon filaments. Defined by brilliant luster, smooth drape, and exceptional tensile strength relative to fiber diameter.
Technical Profile
| Fiber Class | Natural protein fiber |
| Origin | Silkworm cultivation (Bombyx mori) |
Decision Summary
Choose silk for formal occasion wear, luxury scarves, high-end linings, and bridal fabric where luster, drape, and the cool-hand feel are the primary requirements. Choose mulberry silk for maximum luster and dyeability; choose tussah for a matte, textured surface at lower cost. Avoid silk for high-activity use, machine washing, or any application where snag resistance or cost control are critical.
Why Silk Behaves the Way It Does
Silk is the only natural textile fiber produced in continuous filament form. A Bombyx mori silkworm spins a single brin of 600–900 meters to construct its cocoon [1]; multiple brin filaments are reeled together into a composite thread. The individual brin has a triangular cross-section with rounded edges — this geometry acts as a prism, refracting incident light at multiple angles simultaneously, producing the characteristic directional luster that shifts with viewing angle. No other natural fiber reproduces this because no other natural fiber has this specific cross-section at this scale.
The core protein is fibroin, coated during spinning with sericin — a gummy protein that binds the filament into the cocoon. Degumming (boiling in a mild alkaline solution) releases the soft fibroin; fully degummed mulberry silk is maximally brilliant and soft; partially degummed silk retains stiffness (the condition called "raw silk").
Technical Profile
| Property | Value | Notes |
|---|
|----------|-------|-------|
| Fiber form | Continuous filament (fibroin protein) | Only natural filament fiber |
|---|---|---|
| Tensile strength | 25–35 cN/tex (dry) [2] | High relative to weight |
| Elongation at break | 15–25% [2] | Holds pleats under stress |
| Moisture regain | 11% at 65% RH [2] | Moderate; lower than wool |
| Density | 1.34 g/cm³ | Lightweight for the warmth level |
Mulberry vs Tussah Silk
| Property | Mulberry Silk | Tussah Silk | Advantage |
|---|
|----------|--------------|------------|----------|
| Production method | Cultivated (Bombyx mori, controlled diet) | Wild-harvested (Antheraea moths) | — |
|---|---|---|---|
| Filament uniformity | High (consistent diameter) | Variable (irregular cross-section) | Mulberry |
| Luster | Brilliant, strongly directional | Matte, flatter | Mulberry |
| Dyeability | Excellent (full acid-dye palette) | Limited (natural tan base resists uptake) | Mulberry |
| Surface texture | Smooth, fine | Slubbed, textured | Contextual |
| Cost | Higher | Lower | Tussah |
Use-Case Matrix
| Application | Suitable | Why |
|---|
|------------|---------|-----|
| Formal and bridal gowns | ✓ | Luster, drape, cool hand against skin |
|---|---|---|
| Luxury scarves and accessories | ✓ | Lightweight warmth; dye depth |
| Garment and blouse linings | ✓ | Smooth glide over undergarments; breathable |
| Woven silk ties | ✓ | Excellent resilience under repeated knotting |
| Active or utility wear | No | Snag risk; hand-wash only; cost |
| Machine-washable basics | No | Fibroin degrades rapidly under hot-wash agitation |
Care Guide
Hand wash only in cold water (15–20°C) with a pH-neutral or silk-formulated detergent. Do not rub or wring — the filament surface scuffs easily. Roll in a clean towel to remove excess water; dry flat away from direct sunlight (UV degrades fibroin [3]). Press on the reverse side at the lowest heat setting using a pressing cloth. Dry cleaning is the safest option for structured silk garments.
Sources and References
[1] Hatch, K.L., Textile Science, West Publishing. Silk filament length, production, and fiber properties.
[2] Morton, W.E. & Hearle, J.W.S., Physical Properties of Textile Fibres, 4th ed. Woodhead Publishing. Tensile strength, elongation, and moisture regain data.
[3] Freddi, G. et al., UV Degradation of Silk and Its Prevention, Journal of Photochemistry and Photobiology, 2003.