Silk Defined

What Silk Is

Silk is a natural protein fibre, some forms of which can be woven into textiles. The best-known type is obtained from the cocoons of the larvae of the mulberry silkworm, Bombyx mori, reared in captivity in the practice known as sericulture. A caterpillar spins each cocoon from a single continuous filament, and that filament, reeled and twisted together with others, becomes raw silk thread. The shimmering appearance of silk is due to the triangular, prism-like structure of the silk fibre, which refracts incoming light at different angles and produces the changing depth of colour that no flat filament quite reproduces.

Moth caterpillars provide the silk used for textiles, but silk production occurs more widely in nature: several other insects produce silk, especially bees, wasps and ants, which sometimes use it in nest construction, and various arachnids, notably spiders, produce a silk that differs at the molecular level from caterpillar silk. For the textile buyer, though, silk means the cultivated fibre: a filament that is naturally strong for its fineness, smooth against the skin, absorbent enough to take dye in deep, even shades, and comfortable across temperatures, which together explain its luxury status across centuries.

The Five Commercial Types of Silk

There are five major types of silk of commercial importance, obtained from different species of silkworms feeding on different food plants. India has the distinction of producing all five. Mulberry silk constitutes the bulk of world production. It comes from Bombyx mori, which feeds exclusively on mulberry leaves; these silkworms are completely domesticated and reared indoors, which gives producers the most control over quality and produces the fine, white, even filament most people picture when they hear the word silk. Unless qualified, silk on a label means mulberry silk.

The other four are grouped as non-mulberry silks. Tasar, also called tussah, has a copperish colour and coarser texture, is produced by Antheraea mylitta feeding on asan and arjun trees outdoors, and is used mainly for furnishings. Oak tasar is a finer tasar produced in India by Antheraea proyeli feeding on oak in the sub-Himalayan belt, and in China, the major producer, by Antheraea pernyi. Eri, also known as endi, comes from the domesticated Philosamia ricini feeding mainly on castor leaves, and is spun from open-ended cocoons rather than reeled. Muga is a golden-yellow silk exclusive to Assam in India, from the semi-domesticated Antheraea assamensis feeding on som and soalu, and is highly valued for fine clothing such as saris.

Silk in China, India and Thailand

Silk fabric was first developed in ancient China, with some of the earliest examples dated to around 3500 BC, and legend credits the Chinese empress Lei Zu with developing it. Silks were originally reserved for the rulers of China, then spread through Chinese culture and trade across Asia, becoming a staple of pre-industrial international trade; the trade was so extensive that the major routes between Europe and Asia became known as the Silk Road. Archaeological finds, including intricately woven and dyed textiles roughly 2,500 years old, confirm a sophisticated Chinese silk industry far earlier than written records alone would prove, and silk reached the Indian subcontinent, the Middle East, Europe and North Africa.

India has its own long silk history: silk is known as paat in the east, pattu in the south and resham in Hindi and Urdu, and archaeological evidence suggests sericulture using wild silk threads existed in the Indus Valley region at a very early date. India became the second largest producer of silk after China and the largest consumer, with Karnataka a leading producing state and centres such as Kanchipuram, Dharmavaram, Mysore and Banaras famous for hand-woven, hand-dyed silk saris, often with silver threads woven in. In Thailand, two types of silkworm produce silk year-round, women traditionally weave on hand looms, and a single fine thread is combined with others by hand-reeling to produce a usable strand of raw silk.

Silk Fabrics, Dupioni and the Modern Market

From the filament, silk becomes many fabrics. The same fibre can be woven as smooth satin, crisp taffeta, sheer chiffon, textured raw silk or heavy brocade, depending on the yarn preparation and weave. One named fabric type is dupioni, also written douppioni or dupion: a plain-weave, crisp silk fabric produced using fine thread in the warp and uneven thread, reeled from two or more entangled cocoons, in the weft. That uneven weft creates tightly woven yardage with a highly lustrous surface crossed by the characteristic slubs that make dupioni instantly recognisable and popular for formal garments and furnishings.

Silk also reached North America: James I of England introduced silk-growing to the American colonies around 1619, and in the nineteenth century Paterson, New Jersey became a United States silk centre, although imports remained important. The Second World War interrupted silk supplies from Japan, prices rose sharply, and industry turned to substitutes such as nylon, followed by synthetic silk-like fibres made from lyocell that can be difficult to distinguish from real silk. Understanding what silk is, a protein filament with a definable structure and named regional types, is the surest way to judge those substitutes and to read any silk label or price list with confidence.