Silk

Silk is a natural protein fiber produced by certain insects, most notably the larvae of the domesticated silkworm Bombyx mori. The fiber consists mainly of fibroin, a crystalline core protein, encased in sericin, a gummy coating that binds the filaments together. Silk is spun as the larva constructs a cocoon, and the cocoons are harvested and processed to unwind the continuous filament, which is then reeled, spun, and woven into textiles. To harvest the fiber without breaking the cocoon, some methods involve killing or boiling the pupa; others aim to unwind complete filaments.

Silk has a long history of domestication in China, dating to antiquity, and became a major trade commodity along the Silk Road. Sericulture— the cultivation of silkworms and the production of silk— spread to other parts of Asia, Europe, and the Middle East. In addition to cultivated silk from Bombyx mori, wild silks produced by other moth species (such as tussah, eri, muga, and tasar) give varied colors and textures.

Properties include a low density, high tensile strength, and good elongation, with a smooth texture and natural luster. Silk is breathable and dye readily, but can be sensitive to sunlight and abrasion. Common uses are textiles for clothing and furnishings, as well as medical sutures and biomaterials research, reflecting silk’s biocompatibility and degradability. Sericin, once considered waste, is also used in some cosmetic and dermatological products.

Current silk production faces sustainability concerns related to land use, water consumption, and pesticide runoff; ongoing research explores alternative silks, waste reduction, and lab-grown or recombinant silk proteins to vary properties and production methods.