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The Secret of Chinese Silk

For more than two thousand years, the technique of raising silkworms, reeling their cocoons, and weaving the resulting thread into cloth was the most…

For more than two thousand years, the technique of raising silkworms, reeling their cocoons, and weaving the resulting thread into cloth was the most closely guarded industrial secret in the world. From its origins in Neolithic China down to the sixth century CE, the production of silk was a Chinese monopoly so carefully protected that the very word sericulture — the raising of silkworms — became a term of mystery. The legend of the goddess Leizu, the imperial workshops of the Han dynasty, and the famous smuggling of silkworm eggs into Byzantium under the emperor Justinian are three stages in a long history of monopoly, secrecy, and eventual diffusion. I find it striking, in a way the standard treatments rarely emphasise, that the Chinese monopoly outlasted the Roman Empire, the Han, and the Sasanian dynasty, and was broken only when the Roman successor state in the East figured out the trick.

Leizu and the mythological origins

Chinese tradition attributes the invention of sericulture to Leizu, the wife of the Yellow Emperor. According to the legend, Leizu was drinking tea under a mulberry tree in the imperial garden when a silkworm cocoon fell into her cup. As she tried to extract it, the hot tea softened the gum that held the threads together, and a single thread unwound from the cocoon, running on indefinitely. She then developed the loom, raised silkworms on the mulberry leaves of the imperial garden, and presented the first bolt of woven silk to the emperor — and the standard version of the story leaves out the detail that Leizu is also credited, in some versions, with the invention of the foot-treadle loom, which is the kind of compression of two major inventions into one legend that ought to make the modern reader suspicious.

The Chinese silk monopoly is, in the popular imagination, the original industrial secret.

The legend is symbolic rather than historical, but it encodes important facts. Silk production was associated, from the earliest period, with the imperial house and with female labour. The sericultural cycle was governed by the mulberry tree, and mulberries were themselves cultivated with care. The technology of sericulture was treated as a state secret from the very beginning, in part because silk was a key item of tribute and a principal export. I think the standard view is wrong to treat the imperial monopoly as an early example of trade protection in the modern sense; the surviving edicts and the tomb evidence suggest something closer to ritual control of a sacred craft.

The imperial workshops

By the time of the Shang and Zhou dynasties, silk production was an established industry in the Yellow River valley. The Chinese character for silk, si, was in use by the Shang period, and tombs of the early Bronze Age have yielded fragments of woven silk, including the famous silk tapestry from the Mawangdui tomb dated to the second century BCE — a piece in the Hunan Provincial Museum that, in my view, anyone who wants to understand Chinese textile history has to see at least once. The women of the royal household were responsible for the sericultural calendar; the Book of Songs contains poems in which palace women describe the seasons of the mulberry, the feeding of the worms, and the reeling of the thread.

Under the Han dynasty, the imperial workshops of Chang’an produced silk on a large scale. The state licensed the production of certain grades of silk, restricted the export of silkworm eggs and adult moths, and punished smuggling with death. The Roman writer Pliny the Elder reported, in the first century CE, in the Natural History (book 11, chapters 22–26, if you want to check), that silk was combed from the leaves of trees, a misunderstanding preserved in several medieval bestiaries and that tells you quite a lot about what the Romans actually knew about where their most expensive import came from.

A personal note

The legend of the smuggled silkworm eggs, told by Procopius in the sixth century and repeated endlessly since, is almost certainly false in its details. The technology of sericulture was probably transmitted to Byzantium through a long, slow process of trade, not by a single heroic act of smuggling. The legend survives because it dramatizes a turning point; the truth is messier and less interesting.

Further reading

This is one of those topics where the standard reading list is long and the good reading list is short. Three works that I (the author) keep returning to:

  • The relevant Oxford Handbook or Cambridge History chapter — these are uneven but the good ones are very good.
  • A recent issue of Central Asiatic Journal (Brill) for what scholars are actually arguing about right now.
  • One primary source in translation. The Dunhuang manuscripts, in particular, are now mostly online; the British Library’s IDP database is the place to start.

Avoid the popular histories. They are usually wrong in small ways and large ones.

If you came to this article first, start with the main Silk Road guide (Chinese silk production). For the rest of the network, see: