What is strong enough to withstand more than 60,000 pounds of pressure per square inch, clastic enough to be stretched to 20 per cent of its original length, and comes in all the colors of the rainbow? Why, silk, of course!
Silk, though supple and filmy enough to be used for milady's most delicate garments, has the tensile strength of iron wire. It can be stretched longer than any other natural fiber and has a greater affinity to dyes than wool, flax or cotton. To list other virtues: production cost is negligible, low thermal conductivity makes it ideal in all seasons, and it has natural pliancy and luster.
Though known mainly as a material for apparel, silk has a myriad of other uses. Before World War II, it was the best material for parachutes as well as stockings. Though nylon has supplanted silk in both of these instances, there are many other cases where silk is a requisite. For example, no substitute has been found for it in armaments manufacturing; explosive powders are wrapped in silk before being placed in shells. As for its more prosaic uses-anyone who has worn both can testify to the merits of silk over nylon.
Sericulture started in China so long ago that its beginnings are lost in antiquity. As with most crafts of uncertain ancestry, legends galore have sprung up around the art of raising silkworms and unreeling silk from their cocoons. The only certainty is that the cultivation of silkworms for their silk began in China long before written history.
Credit for the discovery of sericulture and silk weaving usually goes to the wife of Huang Ti, the Yellow Emperor, who laid the foundations for a unified nation more than 2,000 years before the birth of Christ. The story of Empress Ssu Ling and her 2640 B.C. discovery is so widespread that it is accepted as gospel by most Chinese school-children.
Details are vague, but the Empress is said to have been strolling in the imperial gardens when she saw a worm spinning itself into a shell and got the idea of unraveling the cocoon into a continuous thread of silk. After inventing the loom, the Empress initiated and supervised the rearing of silkworms and the weaving of silk fabrics.
This legend may have had its origin in the fact that the Chinese silk industry has always had royal patronage. Just as the Emperor was the patron of agriculture, the Empress was patroness of the silk industry. Each spring, the Empress presided at sacrificial rites to honor the Goddess of Silkworms before picking the first mulberry leaf of the year. All court activity ceased while the imperial ladies devoted their time to raising the worms. At the end of the silkworm season, the women sent their cocoons to the Empress and a feast of celebration was held.
The Real Story
A second popular legend concerns the birth of the Goddess of Silkworms. At some time in the long ago, a beautiful country maiden betrothed herself to a white horse. This so enraged her father that he killed her. Soon after, the villagers found the girl wrapped in the hide of a white horse and dangling from a tree. As they watched, the girl was transformed into a worm and proceeded to spin a cocoon around herself. When the cocoon was complete, the girl stepped out and reeded the thread from the cocoon. Her mission accomplished, she rode off to heaven on the horse's hide. As she rose in the air, she called back to the astounded villagers: "Heaven has assigned me to watch over the silkworms!"
Somewhat less romantically than the legends suggest, it probably happened this way: during one of the periodic famines in China, someone put a cocoon in his mouth and the moistened cocoon started unraveling. Once it was realized that the cocoon could be unreeled into a long continuous thread, the next step was easy. Threads obviously could be twisted together to form stronger strands and these could be woven into a sturdy fabric.
There is ample evidence that sericulture was practiced in China long before other peoples found out that certain worms produced silk. Two instances which support this fact are:
—a single cocoon of an identifiable silkworm was found at the Neolithic site of Hsi-yin Tsun in Shansi province.
—old silk found wrapped around bronze burial objects of the Shang-Yin period (1766-1122 B.C.) proves that the art of weaving silk is at least 3,000 years old.
Sericulture and silk occupied positions of some importance in ancient China. For example:
—A government office of the 2nd century B.C. had the special duty of holding in reserve large stocks of consumer goods to stabilize prices. In 110 B.C., an old document reveals, this office had about five million rolls of silk in its warehouses.
—Silk formed a part of the imperial gifts to garrison forces when the Emperor went on inspection tours of the frontiers. In 16 B.C., the touring Emperor gave away a million rolls of silk.
—In the Tang dynasty (618-906), about a hundred thousand men were employed in silk factories outside Sian and silk was recognized as a medium of exchange. In 815, the Tang budget allotted 50 million pieces of silk for military expenditures.
Prized Possessions
Every spring, just before the first mulberry leaves appear, thousands of Chinese schoolchildren begin a massive swapping campaign. Cherished marbles and toys are exchanged for little squares of paper studded with silkworm eggs, each about the size of a drawing pin head. The eggs are stored in old chocolate or match boxes until mid-April, when they hatch into tiny worms, each little longer than a hyphen and barely the thickness of hair.
For the few weeks of the silkworm's life span, these gray-white worms are prized above all other possessions. During this time, school lets out to a mad scramble of children rushing to forage for precious mulberry leaves to feed their tiny worms. Though parents may be grateful that their progeny at last have found a quiet pastime, teachers are exasperated by the lack of discipline. The children constantly peek into silkworm boxes during class hours. On the playground, frequent fist fights develop over the right to pick leaves from the easy-to-reach lower branches of the mulberry tree.
Uniform Growth
Though few youngsters have the patience to follow their hobby through to the final reeling of silk from cocoons, these junior sericulturists indicate the popularity of silkworm raising in China. Professional silkworm farmers follow much the same procedure as the schoolchildren, though with greater care and on a much grander scale. Since sericulture has as its aim the raising of silkworms for the purpose of reeling silk, one of the prime concerns is to keep the worms growing at a uniform pace.
Professional farmers raise the domestic silkworm or Bombyx Mori, which produces finer and stronger threads than other types. Ashy white in color, this preferred silkworm is about two inches long at maturity and reproduces only once a year.
The cycle of sericulture begins 10 days before the mid-April date when the mulberry trees break into leaf. Rolls of paper dotted with eggs are brought in from storage and allowed to mature at room temperature. Before central heating, the eggs were placed in the clothing to be warmed by body heat.
In mid-April, the worms hatch and are immediately brushed into bamboo baskets. Feeding starts right away with finely chopped, tender mulberry leaves. As the worms grow and the baskets become congested, the silkworms are redistributed into more spacious quarters.
Feeding continues with progressively coarser pieces of mulberry leaf. Toward the last week or so, the voracious worms consume 20 times their own weight in leaves, which then are fed to them by the branch. Something like a ton of leaves is needed to raise an ounce or so of newly hatched worms. Since a fully grown mulberry tree yields 80 pounds of leaves a season, more than 30 trees are needed to produce some 12 pounds of silk.
The progress of the silkworm is measured by the four months it goes through in a lifetime. Just before sloughing off its skin, the worm lies sluggish for 24 hours. During these periods of dormancy, the worms are segregated so that each batch will maintain the same growth rate.
By the 35th day, the worms indicate they are ready to spin cocoons. When they stop feeding and assume a semi-erect position, the silk farmer transfers them to straw trusses, with about 60-70 on each truss.
Liquid silk is secreted from two silk glands which run the length of the worm's body. As the liquid emerges, it is coated with sericin, a glandular excretion. This causes the liquid to harden as it meets the air. The thread of silk comes out in a continuous figure-of-eight pattern for about five days until the worm is completely enclosed in a casing made up of an uninterrupted thread of silk, usually 800-1,200 yards long.
Some of the cocoons are selected for perpetuating the species for next year's silk. These are allowed to emerge as moths after 8-10 days and then are paired. The females lay their minute eggs on sheets of paper, which then are washed, dried, and hung up in storage.
Silk Superstitions
The rest of the cocoons are removed for unreeling. The cocoons are immersed in hot water to kill the chrysalis, weight down the cocoon for easier handling, and dissolve the sericin binding.
The end of the filament is found, by hand in the old days and by a spinning machine-like device nowadays, and the silk is unwound on a reeling machine or filature.
The left-over chrysalis is used for fertilizer, while the refuse, silk surface floss, and damaged cocoons are spun into silk considered adequate - though inferior to reeled silk.
Present methods of sericulture differ little from those of olden days despite sporadic efforts to introduce modernization. In the early 20th century, for instance, the American silk industry subsidized the study of better methods of sericulture in three Chinese colleges. The project was abandoned when the new-fangled ideas proved unacceptable to Chinese silk farmers.
The farmers believed that their old method produced silk just as fine and just as marketable as that of the foreign technicians. They had always taken great pains to see to the silkworm's welfare, even to religious observation of old wives' tales handed down from generation to generation. An ancient silk farming manual gives these pointers to silk growers: "The silkworm cannot bear to be near where people pound in a mortar. Neither does it like mourning, nor pregnant women. It also shuns the smell of wine, vinegar, smoke, musk, and oil. It refuses damp mulberry leaves and will not eat hot ones."
When the silk is reeled, the role of the sericulturist ends and the weavers take over. In the old days, the farmer and the weaver were often one and the same person. Professional weavers were usually employed in wealthy households and exceptional craftsmen were preempted by the imperial court. Silk weaving processes and unusually complicated or beautiful patterns were sometimes held as guild or family secrets.
The silk weaving industry, treated as a craft skill for centuries, preserved many of its traditional characteristics until very recently. Looms differed little from their ancient prototypes, examples of which can be seen on relief sculpture dating to the Han dynasty. Today, power filatures and mechanized looms have taken over from primitive hand reeling and the old shuttle or hand looms.
Colors preponderant in the famous Han silks are still the most favored today: bright crimson, brown, yellow, beige, bronze, olive green, emerald green, peacock blue, dark blue, white, and black. Even the decorative patterns of modern weaves differ little from those of the past. Popular still are natural and stylized designs incorporating birds, animals, geometric symbols, cloud scrolls, and floral motifs.
Stuff of Togas
Even before Marco Polo returned home with wondrous tales of exotic Cathay, silk was one of the most sought-after Chinese commodities. The great silk route meandering from western China through Turkestan to the Near East and India took Chinese silk fabrics to Greece and Rome during the 1st and 2nd centuries A.D. Later, Europeans found it more expedient to set up their own weaving industry and by the 6th century, skeins of raw silk had been substituted for the bulky finished goods.
The journey was expensive and slow. Constant search for new routes only ended in failure. Alexander the Great was said to have been partially motivated by a desire for silk when he marched on Persia. Even Columbus' search for a new route to the Indies was in part prompted by the demand for silk. By the time silk reached Rome, a garment was worth its weight in gold, Pliny tells us. Parsimonious Romans forbade their wives to wear silk because of the prohibitive cost. Besides, they claimed, the finely woven, diaphanous material was too immodestly revealing for a proper Roman matron. But these prudish considerations were obviously of no avail, because silk continued to enjoy great popularity. Clearly, the Europeans had to learn how to grow and raise their own silkworms.
For centuries the Chinese managed to keep sericulture one of their best-guarded secrets. Death was the punishment for anyone caught smuggling silkworm eggs out of the country.
It was not until the early part of the 3rd century B.C. that China’s nearest neighbor got the secret. Four Chinese girls went via Korea to teach the mystery to the Japanese. A temple in memory of these girls still stands in Settsu, and Japan today is the world's top producer of silk.
Secret Smuggled Out
In the other direction, knowledge of sericulture was supposed to have been carried to India by a Chinese princess who concealed silkworm eggs and mulberry seeds in the lining of her headdress. A silk industry may have existed in India well before the Christian era.
Though Aristotle spoke of a form of sericulture in Cos, an island in the eastern Aegean, the Coan silk must have been quite inferior, because there is no evidence that it was in any great demand. True sericulture spread to the West via the Byzantine Empire around 550 A.D.
The story goes that two Nestorian monks from Persia learned the process of sericulture during their long residence in China. Upon returning to Constantinople, they reported their findings to Constantine, who promptly ordered them back to China to bring home the makings of a silk industry. The two monks left China a second time with the requisite eggs and seeds hidden in the hollow insides of their pilgrim's staffs. The hardy eggs survived the journey and sericulture began in Europe.
Taiwan was not considered suited to sericulture in the past. The climate was too humid and hot-silkworms prefer the more temperate weather of central China. There was no systematic planting of the mulberry trees essential to a silk industry. And neither the prewar Chinese government nor the Japanese occupiers had much interest in developing sericulture. During the Japanese occupation, sericulture was encouraged on a minor scale only as a means of keeping the aborigines under control. The few mulberry trees of the island grew wild in inaccessible mountain areas inhabited only by the aboriginal tribes.
All this has changed now and raw silk may become a major foreign exchange earner for the Republic of China. With Japan producing less silk because of increased concentration on manufacturing, and with the United States still eager to import some US$27 million worth of raw silk a year, Taiwan silk is assured of a market.
The island has a plan to increase production 20 times in eight years to 6,000 bales (132 pounds bale) of raw silk worth US$4 million. Present production is only 300 bales grown mostly as a family sideline in mountain areas. The Taiwan Silk Corporation processes most of this for domestic consumption.
Working on the new plan is the Silk Improvement Department of the Taiwan Provincial Agricultural Experimental Station. A group of retired servicemen is being helped to develop an experimental plot of about seven hectares of mulberry trees and a small farm of hardy silkworms crossed with the Thailand breed to increase their resistance to heat. If the test is successful, some 3,000 hectares of old tea plantations and marginal land on mountain slopes will be converted into mulberry orchards.
To stimulate the interest of farmers and persuade them to take sericulture seriously rather than as sideline, the Silk Improvement Department is working on ways to use the mulberries. Through judicious pruning of the trees, crops that are predominantly leaf-bearing can be alternated with berry-producing crops. Experiments have already given rise to jam, preserves, liqueurs, and syrups made from mulberries.
China was known for its silk long before the world found out about other aspects of its culture. The time may come when China is again the world's largest producer of the lustrous silken fabrics that no petrochemical textile has yet been able to equal.