What Is Silk and Where Does It Come From?
Silk is a natural protein fiber spun by silkworms — most of it by a single domesticated moth, Bombyx mori, which eats nothing but mulberry leaves and wraps itself in a cocoon of one continuous, gossamer-fine thread. Unwind that thread, twist it together with others, weave it, and you have silk: the only fabric in common use that an animal makes as a finished filament rather than something spun from fluff or pulled from a plant. It comes, in other words, from a caterpillar — and from a craft that began in China nearly 5,000 years ago and has barely changed since.
That single sentence hides a genuinely strange and lovely story. Here's what silk actually is, where it comes from, and how a moth's cocoon ends up against your skin.
So what exactly is silk?
It's a protein, not a plant fiber — and that's the key to everything people love about it. Where cotton and linen are cellulose drawn from plants, silk is made of fibroin, a protein held together by a natural gum called sericin. That protein make-up is why silk drapes and shines the way it does: each filament is a smooth, triangular prism that refracts light, giving silk its quiet, shifting luster. It's also why silk asks for gentle, cold washing — proteins don't forgive heat and harsh detergent.
Where does silk come from?
From a caterpillar, by way of a mulberry tree. The domesticated silkworm, Bombyx mori, hatches from a pinhead-sized egg and does little but eat mulberry leaves for around a month, growing some ten thousand times its original weight. When it's ready to pupate, it spins a cocoon around itself — secreting a single continuous filament of fibroin that, unwound, can run anywhere from a few hundred meters to well over a kilometer in one unbroken thread. That filament is the silk. The whole craft of turning living cocoons into thread is called sericulture, and it's painstaking: it takes thousands of cocoons to make a single garment's worth of fabric, which is a large part of why silk is so expensive. Bombyx mori, incidentally, has been bred by humans for so many thousands of years that it can no longer fly or survive in the wild — a creature wholly remade by its own usefulness.
How is silk turned into fabric?
Carefully. Most reeling is done by machine today, but the steps are the same. The cocoons are sorted and softened in warm water to loosen the sericin gum, then the end of each filament is found and several are reeled together — because a single strand is far too fine to use alone — into one usable thread. Those threads are twisted, sometimes dyed, and then woven. How tightly and heavily they're woven decides the fabric's grade and weight, measured in a unit called momme: the higher the momme, the denser and more durable the silk. The most uniform results come from mulberry silk, the smooth white silk of the Bombyx mori; coarser "wild" silks such as tussah come from other moth species with a more textured, golden character.
Where does the world's silk come from today?
Mostly from where it began. China remains by far the largest producer of raw silk, followed by India, with smaller industries in Uzbekistan, Thailand, Brazil and elsewhere — the International Sericultural Commission, which tracks the trade, puts China and India together at the overwhelming majority of world output. The reasons are partly climate (mulberry grows well, and silkworms are fussy about temperature) and partly heritage: these are the places that have practiced sericulture longest and best. So a silk pillowcase on a bed in the United States traces a line back through a reeling shed, a mulberry grove and a tradition that predates almost every other textile still in use.
A fabric with a 5,000-year head start
Silk's origin is half history, half legend. By tradition it was discovered around 2700 BC by the Chinese empress Leizu, when a cocoon is said to have fallen into her tea and unraveled into thread — and for centuries the secret of sericulture was guarded so jealously that it traveled the length of the ancient Silk Road as finished cloth long before the method itself escaped China. If the fuller story tempts you — the empress, the smuggled eggs, the trade route named after the fabric — it's worth the detour. For our purposes here, the short version is enough: silk is old, deliberate and quietly miraculous.
If you'd like to feel what all that craft amounts to, our LS Silk US pillowcases are 22-momme, made from 100% mulberry silk certified to OEKO-TEX® STANDARD 100 — and if you ever want to be sure what you're holding is the real thing, here's how to tell real silk from fake.
It's an unlikely thing to marvel at, a caterpillar's cocoon. But that's what silk is: a single fine thread, spun by a small creature on a diet of mulberry leaves, reeled and woven in a craft that goes back fifty centuries — and still, somehow, one of the softest things most of us will ever sleep on.