Type: Natural fibre | Classification: Animal fibres | Sub-classification: Secretion fibre

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Fibre structure & physical properties

Fibre composition:


Diameter: 10-13 μm
Very fine: < 10 μm, Fine: < 20 μm, Medium: 20-50 μm, Course: > 50 μm

Length: Filament

Staple length: 500 - 1500 metres
short < 26 mm, medium 26-29 mm, long: 30-38 mm, extra long: 39 mm and over

Natural fibre colour: Cultivated silk is white; Wild silk is yellow or brown.

Microscopic Images (Cross sectional and SEM):

Cross-sectional view of silk fibres (courtesy of Dr Jinsong Shen, TEAM Research Group, De Montfort University, Leicester, UK) -
Image source:

Cross-sectional view of silk fibres (courtesy of Dr Jinsong Shen, TEAM Research Group, De Montfort University, Leicester, UK) –


Cultivated silk is finer, more even, triangular shaped with rounded corners cross section
Wild silk is less even, rectangular cross section

(CC) Sebastian Nordstrom
(CC) Sebastian Nordstrom
(CC) Sebastian Nordstrom
(CC) Sebastian Nordstrom


Smooth, flat surfaces of the fibrils reflect light giving silk a natural sheen (lustre); wild silk broader fibre with fine, longitudinal lines passing across the filament.

Fibre properties (Mechanical, Chemical and Thermal)

Mechanical Properties

Tensile strength (cN/dtex) : 2.6-3.5 dry 1.9-2.5 wet

Chemical Properties

Hydrophobicity: Hydrophilic

Moisture regain (%): 11%

Thermal Properties

Flammability: Silk is a protein fibre which behalves in a similar manner to wool when burnt. Silk can be difficult to ignite, tends to burn slowly, and smells like burning hair. The odour from wool is often less intense than that from silk. The ash is greyish-black and

Sustainability considerations

Silk is biodegradable; however there are ethical and ecological issues with cultivated silk. Wild silk (tussah) meets high ethical and environmental standards (until the dyeing stage). The tussah silkworm leaves a small hole when spinning its cocoon as an escape route, enabling longer filaments to be obtained. Colours are limited to the natural brown palette.

End uses

Apparel: underwear, luxury outerwear, gloves, linings, ties; good to humid climates.


How Its Made Silk [5m 5s]
David Baddiel: On The Silk Road [7m 47s]

Materials using this fibre

Additional resources

Taylor MA, 2004. Technology of Textile Properties. Third edition. Forbes Publications, London, UK.

Zhong Z and Xiao C, 2008. Fabric composition and testing. In: Fabric Testing. Ed: Hu, J. Woodhead Publishing Limited, Cambridge, UK.

ISO/TR 11827:2012 Textiles — Composition testing — Identification of fibres.

Houck, Max M. Identification of Textile Fibers. Cambridge : Boca Raton: Woodhead Pub. in Association with The Textile Institute ; CRC, 2009. Print.