The Secret of Silk

Forty-nine grams.

A hen's egg resting in the palm of a hand weighs more than that. Forty-nine grams is so light that, with eyes closed, a person would hardly know anything was there.

Now comes the part that is hard to believe. Those 49 grams are not a scrap of paper, and not a bird's feather. They are the weight of an entire garment.

A real garment, with a body, a collar and two long sleeves. Laid flat, its fabric alone covers 2.6 square meters. The body of the gown is 128 centimeters long. From the tip of one sleeve to the tip of the other, it measures 190 centimeters. All that cloth, and yet the whole gown folds small enough to fit inside a matchbox.

Take away the two sleeves and the collar, and the body that remains weighs only 25 grams.

This gown does not hang in the glass case of some modern tailor. It was brought up from an ancient tomb at Mawangdui, in the city of Changsha, in Hunan. The woman buried there was a noblewoman of the Han dynasty, and she had lain there for more than 2,000 years. Through all that time, the gown stayed whole. People call it the thinnest gown in the world, thin as a cicada's wing, light as a wisp of smoke.

So forget who sewed it. The better question is what kind of thread could ever be this light.

That thread comes out of the mouth of a caterpillar.

The caterpillar is the silkworm. Its body is soft and ivory white, about as thick as a little finger. It eats no grass, no flowers, no fruit. It eats exactly one thing in the world, and that is mulberry leaves. From hatching to the day it stops eating, a silkworm lives about 20 to 30 days, depending on whether the weather is warm or cold. In that short span it grows through five stages and sheds its skin four times. Each stage lasts only a few days: it eats, then sheds again.

On the last day, the silkworm stops eating. It lifts its head, sways it steadily from side to side, and begins to spin out a thread of silk. It keeps turning like this for three to eight days, winding the thread around itself, until it disappears completely inside a small cocoon about the size of a thumb tip.

That cocoon is a single thread of silk, wound up. No joins, no breaks. By rough estimate, the thread would stretch for hundreds of meters if it were all unwound.

The trouble is that it is far too fine. So fine that one strand alone is good for nothing. The silk reeler soaks the cocoons in hot water so the gum coating them softens. Then the reeler feels for the end of each thread and joins about ten strands from ten cocoons. Only with ten strands together does it become a thread strong enough to string on a loom.

Here the number 49 starts to grow. One gown takes a great many cocoons. A great many cocoons means a great many silkworms. And all those silkworms need a great many mulberry leaves.

So the most interesting part of this craft is not at the loom at all. It is out on the bank of a pond.

In Huzhou, in Zhejiang, people worked out a way to grow mulberry leaves more than 2,500 years ago, and it still sounds clever today. They dug ponds for water. The earth they dug out was piled into high banks all around. On those banks they planted mulberry trees.

The mulberry leaves were picked to feed the silkworms. Once the silkworms had eaten their fill, their droppings went into the pond as food for the fish. Four kinds of fish live in the pond, each at home in its own layer of water. One feeds near the surface, one hangs in the middle, and one keeps close to the bottom, so none takes another's share. Then, at the end of the season, people dredge the mud from the bottom of the pond and spread it back onto the mulberry banks. That mud feeds the roots of the mulberry trees. The trees put out new leaves for the silkworms.

That is how the circle closes. Leaves feed silkworms, silkworms feed fish, and pond mud feeds the leaves. Nothing in that pond is treated as waste. The ponds also hold water back each rainy season, so the whole area floods less. This landscape of ponds and mulberry banks is now recognized by the Food and Agriculture Organization of the United Nations as agricultural heritage of the whole world.

In 2009, this whole long craft was added to the UNESCO list of the intangible cultural heritage of humanity. Not the fine silk alone, but the whole chain of work: growing mulberry, raising silkworms, reeling the silk, twisting the thread, and only then weaving. The craft is still alive in Zhejiang, in Jiangsu, and in Chengdu in Sichuan. Every April, the women who raise silkworms pin flowers of many colors in their hair and hold a festival. Old tales say that the first person to discover silk thread was a woman named Leizu. That is a story passed down by word of mouth, though, not something written in the histories.

The craft is older than anyone once guessed. In Henan, in China, archaeologists found pieces of silk more than 5,000 years old. From the same area came a small silkworm carved from bone, 6.4 centimeters long. It is shaped in the curve of a worm spinning its silk. So 5,000 years ago, someone sat and watched a silkworm long enough, and fondly enough, to carve it.

Silk is light, compact and precious. So for generation after generation, people carried it from the markets of one region to the markets of another, trading it for things their own home did not have.

In Vietnam, trays of silkworms are nothing unusual at all. Generations of children grew up beside round bamboo trays set in the front room of the house, scattering mulberry leaves for the silkworms day after day. Grandmothers and aunts picked mulberry leaves, fed the silkworms and then sat reeling silk. The uncles tended the mulberry fields and carried the droppings off to feed the garden. The work was so hard that older generations had a saying for it: nuôi tằm ăn cơm đứng. Those who raise silkworms eat their rice standing. People were so busy that even meals were eaten standing, quickly, before going back to the trays.

So China and Vietnam share a very old craft, one that belongs to the whole region. People in this part of the world, long ago, all noticed the same thing. Plant a tree with big leaves, raise a small caterpillar, and draw a thread out of it.

Today Lâm Đồng is the largest mulberry and silkworm region in Vietnam, with about 17,000 households making a living from this work. Bảo Lộc silk has been shown as far away as Japan, India, France and Italy. And in Vạn Phúc, in Hà Đông, the looms have been running for more than 1,000 years and still have not stopped.

In Vạn Phúc, the looms click steadily, like light rain on a roof. If someone cut a length of freshly woven silk and laid it in an open hand, it would slip between the fingers like water, soft and almost weightless.

Forty-nine grams. Lighter than a hen's egg. And behind that tiny number stand a pond, a green bank of mulberry trees, a school of fish down in the pond, and a small caterpillar that quietly ate leaves for almost a month to give that much.