From Mulberry Leaf to Cloth: How Silk Is Really Made

A silkworm, a mulberry tree and a single thread nearly a kilometre long. The quietly astonishing journey silk takes from cocoon to cloth.

Hold a silk scarf up to the window and it is hard to believe where it began: not in a mill, but in the mouth of a small, blind, flightless moth-caterpillar with an appetite for one particular tree. The story of silk is one of the strangest in the whole history of what we wear, and most of us have never been told it properly.

It starts with a leaf

The domesticated silkworm, Bombyx mori, eats one thing: the leaves of the white mulberry. It eats almost without pause for its short life, growing many times its birth size, and then it does the remarkable thing. From a gland running the length of its body it secretes a single continuous filament and, moving its head in a slow figure-eight perhaps tens of thousands of times, wraps itself in a cocoon.

That filament is the miracle. Unwound, the thread from one cocoon can run close to a kilometre without a single join, one of the longest natural fibres on earth. It comes out as twin strands of a structural protein called fibroin, glued together by a second, water-soluble protein called sericin, the gum that stiffens the cocoon into a shell.

From cocoon to thread

Raw silk is reeled, not spun. The cocoons are warmed to soften the sericin, the loose end of the filament is found, a fiddly and patient art, and the threads from several cocoons at once are drawn out and twisted together into one strong strand. This is also the step where the ethics of silk begin, since traditional reeling does not spare the pupa inside, and we have written honestly about whether silk is cruelty-free and sustainable rather than gloss over it. Later the sericin gum is washed away in a stage called degumming, and the fibroin beneath is revealed for what it is: soft, strong, and quietly luminous.

It is laborious in a way that explains the price. It takes thousands of cocoons to make the woven silk in a single scarf, which is the real answer to why is silk expensive, and why the weight of a finished cloth, its momme, is a fair measure of how much of this thread went into it.

The secret that built a road

The old story says that for three thousand years, only China knew how this was done. Legend hands the discovery to the Empress Leizu around 2700 BCE, who, the tale goes, was taking tea beneath a mulberry when a cocoon dropped into her cup and began to unravel in the heat, a shining thread lifting from the water. The secret, it is said, was guarded fiercely, and smuggling silkworm eggs out was for centuries punishable by death.

The truth, as ever, is a little more interesting. In 2026, archaeologists writing in the journal Science Advances described three silkworm cocoons unearthed at Sapalli Tepe, a Bronze Age settlement in what is now southern Uzbekistan, dated to around 1900 BCE and found beside the charred remains of mulberry wood. Whether the craft travelled or was learned anew, silk and its mulberry had reached Central Asia some four thousand years ago, long before the trade routes we call the Silk Road ever had a name. What is certain is that the hunger for this one fabric went on to carve those routes, moving not just cloth but religion, language and disease across whole continents. Few materials have moved history the way this single thread did.

Why it matters to the touch

All of this is why silk feels the way it does against your skin. Fibroin is a protein, chemically closer to your own hair and skin than to cotton or polyester, and the triangular filament is what throws back that shifting, inner light. When people say silk feels alive, this is what they are noticing, a fibre grown rather than manufactured. If you want the shorter version of where it comes from, we keep one here, and for the full origin story, you can start in ancient China.

Common questions

How is silk actually made? A silkworm spins a cocoon from one continuous filament. That filament is reeled off in warm water, several cocoons at a time, twisted into thread, degummed to remove the sericin, then woven into cloth.

What are fibroin and sericin? Fibroin is the strong, lustrous structural protein that becomes the silk you wear. Sericin is the water-soluble gum that holds the cocoon together and is washed away during degumming.

How long is the thread from a single cocoon? Close to a kilometre of unbroken filament, one of the longest continuous fibres in nature.

You can feel every step of that journey in a finished piece of mulberry silk, where a thread grown by a caterpillar becomes something you rest your face against each night.

A leaf, a caterpillar, a thread a kilometre long. It remains, five thousand years on, one of the few luxuries that is exactly as remarkable as it feels.