Silk

Silk is a protein called fibroin, spun by the larva of the silk moth as a continuous filament to build its cocoon. A single cocoon yields something between six hundred and nine hundred metres of unbroken thread, which is what distinguishes silk from every other natural fibre: it does not have to be spun from short staples, only unwound.

The filament is triangular in cross-section, and that is why silk shimmers — the facets refract light like a prism at every angle. Its strength for its weight exceeds steel's, and its combination of strength with extensibility is still not fully matched synthetically.

Sericulture was a Chinese monopoly for something like two thousand years, protected by a death penalty for exporting eggs or the technique, and the Silk Road is named after the single commodity that justified the journey. Byzantium eventually obtained eggs by industrial espionage in the sixth century, in an episode involving two monks and a hollow staff that may or may not be true.

Its modern significance is partly as the thing that was replaced. DuPont set out explicitly to make a synthetic substitute for silk, and nylon was the result — announced in 1938, sold as stockings in 1940, and taken entirely by the war for parachutes within two years.