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Silkworm cocoons
Silk is a wonderfully strong, light, soft, and sensuous fabric produced from cocoons of the Bombyx caterpillar, or silkworm. Of all the fabrics, silk is regarded as the finest and most beautiful. It has a wonderful sheen---the result of triangle-shaped fibers that reflect light like prisms and layers of protein that build up to a pearly sheen---and can be dyed a host of wonderful colors. The late fashion editor of the Washington Post Nina Hyde wrote, “Designers revel in its feel, its look, even its smell." [Source: Nina Hyde, National Geographic, January 1984, ╟]

Intricately embroidered brocades have traditionally been greatly prized in Japan. Nishijin-ori is the name of the 500-year-old craft of silk weaving that was centered primarily in Kyoto. The are several hundred classifications of Nishin-ori weaves and patterns. Common images include cranes, flowers and geometric patterns. Master weavers can recreate a Van Gogh painting with silk thread.

Some of the most beautiful weaves include Shokkokin, a vivid rubicund weave originating from Changjiang, China; Rikyubai, a gold pattern modeled after the Japanese apricot; Monjiro, an ivory weave used by Buddhist priests; Itoya-rinpo, a beautiful circular pattern; and Shikami-Monchohankon, a pattern with a teeth-baring lion modeled after images on Chinese bronzeware from the 16th century B.C.

Silk can be used for all sorts of things. In addition to being woven into fabric, it has been made into cold cream in China, beauty powder and parachutes in the United States, teeth braces in Italy and fishing nets around the world. Bicycle racers say that tires made with silk give them a smoother ride and better traction. Skiers like it because it wicks away moisture and scientist say silk is stronger than steel. In Japan silk artists are revered as national treasures. In India corpses are covered with silk shrouds as a sign of respect. Frugal Ben Franklin splurged on a silk kite for his famous electricity experiments and the first French atomic bomb was dropped from balloon made partly of silk.╟

Good Websites and Sources: Wikipedia article on the History of Silk Wikipedia ; History of Silk silk-road.com ; Wikipedia article on silk Wikipedia ; Wikipedia article on Silkworms Wikipedia ; Wormspit wormspit.com ; Raising Silkworms silkwormshop.com ; Making Silk chateau-michel.org ; Silk Making with Pictures designboom.com ; Tomboco.com tomboco.com.au ; Traditional Crafts of Japan---Weaving kougei.or.jp/english ; About Silkworms silkwormmori

Links in this Website: JAPANESE CLOTHES Factsanddetails.com/Japan ; KIMONOS AND JAPAN Factsanddetails.com/Japan ; FASHION IN JAPAN Factsanddetails.com/Japan

Early History of Silk

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8th century Sogdian silk
According to a Chinese legend, silk was discovered in 2460 B.C. by the 14-year-old Chinese Empress Xi Ling Shi who lived in a palace with a garden with many mulberry trees. One day she took a cocoon from one of the trees and accidently dropped it hot water and found she could unwind the shimmering thread from pliable cocoon. For hundreds of years after that only the Chinese royal family was allowed to wear silk. Xi Ling Shi is now honored as the goddess of silk.

The oldest concrete evidence silk weaving are impressions found on a bronze urn dated to 1330 B.C. The provincial museum in Hangzhou houses silk threads and embroidery knots that may be 4,500 years old. In 1982 brickyard workers stumbled across a ancient tomb from 300 B.C. with remarkably well preserved silk quilts and gowns. ╟

The secret of making silk remained in China for 2,000 years. Imperial law decreed death by torture to those who disclosed it. No one is sure when the secret first seeped out of China, but it is known to have reached Japan by way of Korea by the A.D. forth century and said to have been brought there by four Chinese girls. It is also said that silk was brought to India by a Chinese princess who hid eggs and mulberry seeds in the lining of her head dress.

History of Silk in Japan

19th century dancing girls
Printed silks from the 8th century survive from an 8th century palace in Nara. The traditional, Japanse, multi-storied, thatch-roof homes contained an attic at the top to keep mulberry-leave-munching silkworms. The Empress of Japan still feeds silkworms on the palace grounds each spring.

For a long period of time Japan produced the best quality silks in the world, better than those produced in China. In the 19th century silkworm eggs from Japan that were resistant to the rare disease of tacherie, silkworm Nosema disease and flacheriem, as confirmed in a report by Louis Pasteur in 1865, saved the silk industry in Europe.

Much of heir early engagement between Japan and France revolved around the silk trade. In the 18th and 19th centuries, Lyon, France was a major center of silk and textile production center. For a while the purchase of silkworm eggs and raw silk from Japan by France accounted for more than half the world’s production.

Before World War II, the export of silk was a major source of foreign currency. In the 1920 and 30s, before nylon was invented, Japan supplied much of the silk used to make silk stockings. The silk industry boomed in Japan in the late 1960s and early 1970s when women who never had money before all of sudden had to buy not just one but several silk kimonos. Dried cocoon futures reached its peak in 1969.

By the end of the 1970s the silk market was in decline as Japanese women became interested in Western clothing. The silkworm business has virtually collapsed due to competition from China and improved quality of synthetic fibers. Japan’s last silk spinning factory closed in April 2003. Trading ended in March 2004 due to dwindling local silk production.

Prof. Masao Makagaki, an insect geneticist at the Shinshu University in Nagano Prefecture, developed a super-strong “spider silk” by inserting spider thread genes into silkworm eggs. Socks made with the material are slated to put the market in 2010. Researchers are also working making fishing line and surgery sutures with it.

Rumors and the History of Silk in Japan

The silk industry in Japan was dealt a serious blow by the invention of nylon in the United States before World War II. Henshu Techo wrote in the Yomiuri Shimbun: “People told a story about the origin of the synthetic fiber's name as if it were true. They said it was an acronym that people in the U.S. textile industry, which had been waging an uphill battle against the advancement of Japanese silk, shouted in exultation: Now You Laugh Old Nippon. [Source: Henshu Techo, Yomiuri Shimbun, July 17 2012]

“Japanese literature scholar Yasaburo Ikeda wrote about this story in "Nihon Koji Monogatari" (Stories of historical events in Japan) published by Kawade Shobo Shinsha Publishers Inc. The story was nothing but a popular belief, but it well illustrates how the Japanese silk industry, which led the modernization of this country like a locomotive, had been enjoying prosperity. [Ibid]

“It has been reported that a symbol of the silk industry, the Tomioka Silk Mill in Tomioka, Gunma Prefecture, will be recommended by the government to UNESCO for designation as a World Cultural Heritage Site. It was established in 1872 as a public-run model factory by the government, which was rushing to promote industrial development. [Ibid]

“A reckless rumor spread at that time, probably due to imagination about the red wine foreign engineers drank: If you work at the mill, your blood will be taken out. The government thus faced difficulty in recruiting workers for the mill. This anecdote evokes how things were in the past. The red brick building still stands there as though resting in the afterglow of history's sunset. [Ibid]


Silkworms are not worms but caterpillars, the larvae of moths. They belong to two families: Bombycidae (the commercial silkworm), which feed on mulberry leaves, and Saturniideae (the so called wild silkworms), which primarily eat oak leaves.

All butterfly and moth caterpillars produce silk, as do spiders, but only silkworms produce the lustrous, long fiber that is made into commercial silk. Most commercial silks comes from the Bombyx mori, a silkworm that originated in China. Over 300 varieties of this caterpillar are found in China today. More than 600 varieties are found in Japan. Tussah wild silkworms are bright yellow in color and may reach a length of six inches. Their silk is strong but rough and doesn't die very well.

Domesticated silkworm moths have been described as "machine devoted to sex" but are essentially flightless so they must search for mates on foot. If necessary they can travel a considerable distance to find a mate. Male silkworm have such a good sense of smell they can smell females 6½ miles away.

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Mulberry trees

After several hours of mating the female lays 300 to 500 eggs, each not much large than a pinhead, then dies within two or three days. The eggs, which require cold weather to trigger development, hatch anywhere from six weeks to 12 months after being deposited.

The eggs hatch producing grubs that develop into larvae (the caterpillars or silkworms) and spend several weeks munching on mulberry leaves and molting. When they outgrow their skin, the simple squeeze out it, jaw and all, and grow a new one. After tossing off their skin for the forth time they begin find a place and being making their cocoon. After about a month they emerge as moths.


The process or raising silkworms and unwinding their cocoons is called scriculture. Silkworms have to be carefully taken care of: they need to be fed regularly and maintained in a carefully controlled environment. It is a labor intensive industry, generally requiring lots of people willing to work for low wages.

Making silk begins when a female silkworm lays her eggs. In China, the eggs are often produced in special institutions regulated by the government to make sure the eggs are healthy. Workers speed up the hatching process by soaking the eggs in chemicals. About a week after the eggs are laid, silkworm grubs emerge. They are around a quarter of an inch in length and the width of a hair. They squirm into huge flat baskets, filled with mulberry leaves and are placed on shelves.

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The silkworms spend their 25- to 28-day long lives in baskets, or trays, munching on mulberry leaves. Even though the baskets are open the silkworms do not try to escape. Silkworms are extraordinary eating machines. They can eat and breath at the same time, taking in oxygen from nine holes on the sides of their body, and make eating sounds compared with fizzing Alka-Seltzer. They are especially hungry right before they begin making their cocoons. In some cases they are fed ten times a day and their body weight increases 10,000 times in their short lives.

The main raw material other than the silkworms themselves are the leaves from mulberry trees. In the past, mulberry trees were raised on hilly areas while lowlands were devoted to rice growing, and peasants had to spend a lot of time picking leaves off the trees. These days the leaves are produced on trees grown on plantations very far from where the silkworms are raised and trucked in to wear the silkworms are raised.

A hundred kilograms of mulberry leaves yields 25 silkworm cocoons. The caterpillars used to make the kimono devoured over 135 pounds of mulberry leaves. The 8,000 worms supply silk for ten blouses, consume approximately 350 pounds of mulberry leaves. The leaves from plantation-grown mulberry trees are plucked, chopped and prepared for the silkworms. In Japan, they are mixed with beans and agar into a concoction that looks like sweet bean paste. After the trees are stripped they are pruned and sprayed for next year's crop.

Silkworm Care

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Trays with silkworms
The silkworms are kept in rooms with temperatures between 75̊F and 80̊F. Lights are left on around the clock but are not allowed to shine directly on the caterpillars. Great care is taken to keep the rooms clean and measures are taken to prevent the caterpillars from being exposed to drafts, smoke, odors and noise. Women who raise silkworms in Hangzhou can not smoke, wear make-up or eat garlic, and they must wear clean sandals.

The quality of silk is often determined by the quality of care the silkworms receive. According to ancient Chinese guidelines that are still followed today: "First of all, the bark of a dog, crow of a cock, even a fowl's smell can upset freshly hatched worms. Second, larvae should rest on dry mattresses; and they must sleep, eat, and work in harmony."

"Third, A worm out of sync with the rhythm and transformation of the majority is buried or fed to fish to avoid any variation in the silk. Forth, drowsy newly hatched worms are tickled with a chicken feather to prod development. And finally, the attendant, called silkworm mother, should have no bad smells, should wear clean simple clothes so as not to stir the air, and should not eat chicory (or even touch it)."

Workers bring in huge supplies of mulberry leaves for the silkworms to eat and clean the trays where they live. After they hatch 20 kilograms of silkworms eat about three kilograms of mulberry leaves a day. As they grow they eat more and more. After a month the grubs have grown into larvae that consumer 300 kilograms of mulberry leaves a day. Not long after that the silkworms stop eating and spend about a week making their silk cocoons. The original 20 kilograms of grubs produced from 80 to 120 kilograms of silk, which silk producers buy at around $1 or $2 a kilogram. Some worms are allowed to hatch into moths. Their eggs are collected

Silkworm Cocoons

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Sorting silk cocoons
Silkworms are about three to four inches long when they raise their heads, indicating they ready to begin spinning their cocoons. At this stage they are transferred to trays containing piles of straw on which the caterpillars attach themselves to spin their cocoons.

Once anchored in place the caterpillars move their head in a figure eight position weaving the cocoon around their bodies. Viscous liquid silk is produced by a pair of 15-inch-long glands inside the caterpillars body and ejected through a small hole at a rate of about a foot a minute. When it comes into contact with air it hardens into silk. The caterpillar surround itself completely with a cocoon made of a single continuous filament over a mile long.

After the silk is harvested in China the cocoons are carried in table-size baskets to government purchasing stations. The commune is paid, depending on quality and weight, about three dollars a kilogram (2.2 pounds) for the crop. Some cocoons are set aside to allow the caterpillars to metamorphose into moths for egg production but most are made into silk cloth.

Two or three thousand cocoons yield a pound of silk cloth. It takes 110 cocoons to make a tie, 630 for a blouse, 900 for a shirt, 1,700 for dress and 3000 for a heavy silk kimono.

Silk Production

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Silk spinning
A typical three- to four-centimeter-long cocoon produces a 1- to 1.5-kilometer-long filament. Raw silk needs to be cleaned and twisted into heavier yarns before it is ready for cloth making. This process is called throwing. It is highly mechanized and is similar to spinning cotton. An average factory can produce about six tons of raw silk a month.

The production of silk in a processing mill usually begins when the silk cocoons are placed in a hot-air chambers to kill the caterpillar pupa and dry out the cocoons in such a way that the unbroken silk threads remains undamaged. If they silkworms were allowed to live they would damage the silk threads when they broke out of the cocoon. The cocoons are soaked in hot water to soften them up and get rid of the natural glues. Silkworm cocoon are sometimes yellow and pink; these colors are boiled out during processing. Women often work all day with the hot cloudy water, which is too hot for most of us to touch.

To make silk yarn, the nearly invisible strands from five to eight cocoons plucked from the hot water and plied together and placed into the eye of a reeling machine, which pulls the thread from the cocoons, twists them together into a single yarn that is 800 to 1,200 meters long and is wound on spools. Natural glues left on the strands bind the yarn together. At factories in China, women stand all day in front of reeling machines. If a cocoon stops bobbing, the person operating the reeling machines knows a strand has broken or run out and the end of another cocoon is unraveled and put in its place.

During a second reeling, the silk is measured into specific lengths. The silk yarn is then graded for shipment. The process the silk goes through afterwards often depends on the quality of the silk. Weighted silk is colored with dye and dipped in a solution of metallic salts that add weigh and give it a sheen. Spun silk is made from the floss and other wasted filaments of the silk process. These fibers are carded and spun into yarn using methods similar to those used to make wool.

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Silk thread

Wild silk comes most from two kinds of moths: the Antherea mylita of India and the Antherea pernyi of China. The strands from the cocoons made these moths are coarser and more difficult to unravel. They are often made into spun silk.

Silk Industry in Japan

Silk production is largely automated and done in factories but the raising of silk worms to make silk is still very a “cottage industry” done primarily at people’s homes. In some cases government provides anyone who is willing to raise silkworms with 20 kilograms of very small silkworm grubs, which are placed in special boxes in special rooms and fed mulberry leaves gathered from trees near the homes of the farmers raising them.

Gumma Prefecture has traditionally been Japan's principal silk producing region. When the silk industry was at its peak Gumma's 25,000 silk raising houses produced more than 40 percent of Japan's silk. Now there are less than 1,000 silk-raising houses.

Everything in a Japanese silk factories was mechanized even the plucking of mulberry leaves. The work place was as sterile as a silicon chip plant, with humidity, airflow, and temperature are all monitored five times a day. Visitors to silk factory were required to wash in a soupy solution tinged with formaldehyde and and wear a starched scrub suit and a gauze face mask. Looms were driven by computers. [Source: Nina Hyde, National Geographic, January 1984]

In the 1980s, more than a billion caterpillars at a silkworm station in Tokorozawa, Japan crawled and fed on blocks of man-made, mulberry-leaf-soybean-cornstarch concentrate, which looked like "granola bars." Caterpillars that refused to eat were prodded with a feather in the direction of their meal. A Japanese physiologist who helped devise the diet, told National Geographic, "It is much easier to prepare food for a person than a silkworm." Over 50 percent of Japan's silkworms were raised this way. [Source: Hyde]

The Gumma Sericultural Experiment Station has breed silkworms that produce pink, yellow, orange, blue, purple and green silks. To achieve this the silkworms are fed dyes mixed with ground mulberry leaves. The colors they eat don't always match up with the colors they produce. To achieve purple the silkworms are fed food mixed with red and blue dye. Colored silk produced in this way is better than died silk because its is dyed to the core and has a more natural color.

These days silkworm technology is being applied to genetic engineering and biotechnology. The National Institute of Agrobiological Sciences in Tsukuba, Ibaraki Prefecture has genetically engineered silkworms with genes that cause fluorescence in jellyfish and coral and manipulated them to produce interferon, a medicine used to treat a number of ailments. Japan is a leader in the race to decode the silkworm genome.

Image Sources: University of Washington; Silk Road Foundation; Beifan.com http://www.beifan.com/; Nolls China website http://www.paulnoll.com/China/index.html; Columbia University; Ray Kinnane, Visualizing Culture, MIT Education

Text Sources: New York Times, Washington Post, Los Angeles Times, Daily Yomiuri, Times of London, Japan National Tourist Organization (JNTO), National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

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© 2009 Jeffrey Hays

Last updated August 2012

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