Chinese Silk Production

The thread that gave the Silk Road its name was produced by a caterpillar no longer than a finger, fed on the leaves of a single species of tree, and tended by a workforce that was overwhelmingly female. Chinese silk production, more than any other industry, defined the economic relationship between East and West for nearly two thousand years. The technical mastery that allowed Chinese workshops to produce silk of unmatched fineness, the institutional arrangements that organised its cultivation, and the political efforts to keep its methods secret together constitute one of the most remarkable cases of state-backed industrial secrecy in the pre-modern world. I have always found the biology of the thing more interesting than the geopolitics, and I think most popular accounts get the balance wrong.

This article describes the practical processes by which silk was produced in China, the social arrangements that supported the industry, and the role of silk in the Chinese economy. For the broader trade in silk and silk goods, see the article on silk and silk goods on the Silk Road. The long Chinese monopoly on sericulture and its eventual collapse is treated in the article on the secret of Chinese silk. The political background to the early expansion of the silk trade is described in the article on the Han dynasty and the Silk Road, and the high point of the silk industry in the article on the Tang dynasty and the Silk Road. For the broader economic context, see the article on Silk Road trade, goods, and economy.

The biology of silk

The silk of commerce is produced by the larva of the domesticated silk moth, Bombyx mori, in the course of spinning the cocoon in which it will pupate. The moth is entirely domesticated — it cannot fly, cannot feed itself, and cannot mate without human assistance — and the species has been dependent on human cultivation for at least five thousand years, with the earliest unambiguous silk textiles from Hemudu and other Neolithic sites in the Yangtze valley. The single thread that the caterpillar spins can reach lengths of more than a thousand metres, although the fine, even thread that is commercially valuable typically runs for around three hundred to five hundred metres before the caterpillar pauses or breaks the filament.

The thread is composed of two proteins, fibroin and sericin, which together give raw silk its characteristic combination of strength, elasticity, and sheen. To be useful for weaving, the cocoons must be processed quickly, before the moth emerges and breaks the filament — there is a small window of perhaps a week or ten days, and the timing of the harvest dictated the timing of the entire annual sericultural calendar. The standard Chinese method, in use from at least the Han dynasty, was to drop the cocoons into boiling water to kill the pupa, then to agitate them with a brush to find the loose ends of the filaments, which were then unwound and combined into a single thread. A single silk garment might represent the work of several thousand caterpillars, which is a number that has always struck me as worth pausing on.

Silk is, above all, a technology of patience.

Mulberry cultivation

The domesticated silk moth feeds exclusively on the leaves of the white mulberry, Morus alba. The cultivation of mulberry trees was, accordingly, the foundation of the entire silk industry, and the relationship between mulberry trees and silkworms was so close that the Chinese used a single character, sang, to refer to both, and a single term, can ye or “mulberry and silkworm business,” to refer to sericulture as a whole — a linguistic fact that, in my view, tells you more about the importance of the industry than any number of trade statistics.

Mulberry cultivation was a skilled and demanding task. The trees required careful pruning to produce the maximum yield of tender young leaves, and the leaves themselves had to be picked at the right stage of growth — too mature, and they would be rejected by the silkworms; too young, and they would not sustain the larvae through their full growth. The trees were grown in a wide range of settings, from large plantations on the lower Yangtze plain to small kitchen gardens and even to the edges of rice paddies, where the mulberry was often interplanted with the rice and the silkworm raising was fitted into the agricultural slack season.

The geography of mulberry cultivation shaped the geography of silk production. The Yangtze River valley, with its fertile alluvial soils, abundant water, and warm climate, was the heartland of Chinese sericulture from at least the Han dynasty. The lower Yangtze — roughly the modern provinces of Jiangsu, Zhejiang, and Anhui — produced the bulk of Chinese silk in the Tang, Song, and later dynasties, and cities like Suzhou and Hangzhou became synonymous with the finest silk cloth in the world. Other important regions included the Sichuan basin (Chengdu in particular, which was a major centre from at least the Tang), the Hubei plains, and parts of the North China plain — though the lower Yangtze kept its primacy, and I think the standard histories do not always make that sufficiently clear.

A personal note

The most important figure in the long history of Chinese silk is not an empress or an emperor but a worm — Bombyx mori — and a tree, the white mulberry. The technology of sericulture was a coevolution of insect, tree, and human skill over a period of at least four thousand years. Any history of silk that does not start with the biology is missing the point.

Further reading

If you only have time for one thing, read Hansen (2012) — the rest is detail.

• Hansen, The Silk Road: A New History (Oxford, 2012).
• Peter Frankopan, The Silk Roads (Bloomsbury, 2015), if you want the more sweeping argument.
• Whitfield, Life Along the Silk Road, 2nd ed. (2015).
• The relevant chapter of the Oxford Handbook or Cambridge History of the region or period.
• One article from a recent issue of Central Asiatic Journal or Journal of the Economic and Social History of the Orient (JESHO) for current scholarship.

Related pages

See also The secret of Chinese silk, Silk and silk goods on the Silk Road, and The Han dynasty and the Silk Road.