Thai Woman Boiling Silk Cocoons

Thai Woman Boiling Silk Cocoons


Thai Woman Boiling Silk Cocoons - History

The discovery of the product silk from the silkworm species Bombyx mori occurred around 2700 BC. According to Chinese tradition the bride of Emperor Huang Ti, a 14-year-old girl called Hsi Ling Shi, discovered the invention of the first silk reel. Sericulture, the cultivation of the silkworm, spread through China making silk a highly valued commodity much sought after by other countries. In 139 BC the world's longest trade route was opened stretching from Eastern China to the Mediterranean Sea. It was named the Silk Road after its most valuable commodity. By 300 AD the secret of silk production had reached India and Japan.

Silk manufacture eventually reached Europe and America. During the 18th and 19th centuries Europeans produced several major advancements in silk production. By the 18th century England led Europe in silk manufacturing because of English innovations in the textiles industry. These innovations included improved silk-weaving looms, power looms and roller printing. Between 1855 and 1865 an epidemic called Pebrine disease, caused by a small parasite, raged through the industry. It was the French scientist Louis Pasteur who discovered that this could be prevented through simple microscopic examination of adult silkmoths. Much research was carried out on silkworms at this time, ultimately setting the stage for a more scientific approach to silk production. Silk production today is a combination of old and modern techniques.

Bombyx Mori

Silkworm is a common name for the silk-producing larvae of any of several species of moths. The larva is not really a worm at all but a caterpillar. There are several species of silkworm that are used in commercial silk production, however Bombyx mori is the most common.

Bombyx mori is native to China and was introduced into Europe and western Asia in the 6th century AD and into North America in the 18th century. It feeds entirely on the leaves of the mulberry tree, so has flourished only where conditions are suitable for large numbers of leaf-bearing mulberry trees. Bombyx mori has been cultivated over many centuries and is no longer known in the wild.

Silk - A Hardened Glandular Fluid

Silkworms possess a pair of specially modified salivary glands called sericteries, which are used for the production of a clear, viscous, proteinaceous fluid that is forced through openings called spinnerets on the mouthpart of the larva. As the fluid comes into contact with the air it hardens. The diameter of the spinneret determines the thickness of the silk thread, which is produced as a long, continuous filament.

Typical Commercial Silkworm Production

The first stage of silk production is the hatching of the silkworm eggs, in a controlled environment such as an aluminium box, which are then examined to ensure they are free from disease. The female deposits 300 to 400 eggs at a time. In an area the size of this page around 50 moths would deposit more than 20,000 eggs, each about the size of a pinhead. The female dies almost immediately after depositing the eggs and the male lives only a short time after. The adult possesses rudimentary mouthparts and does not eat during the short period of its mature existence.

These disease-tested eggs are raised in temperature and disease-controlled conditions. They are fastened to a flat surface by a gummy substance secreted by the female. The larvae hatch in about 10 days and are about 0.6cm long. Once hatched, they are placed under a layer of gauze and fed huge amounts of chopped mulberry leaves during which time they shed their skin four times. The larvae may also feed on Osage orange or lettuce. Larvae fed on mulberry leaves produce the very finest silk. The larva will eat 50,000 times its initial weight in plant material.

After it has achieved its maximum growth of 7.5cm at around 4 to 6 weeks, it stops eating, changes colour and attaches itself to a compartmented frame, twig, tree or shrub in a rearing house to spin a silk cocoon over a 3 to 8 day period. This is period is termed pupating.

A Hard Day’s Night

Steadily over the next four days the silkworm produces a fine thread by making a figure of eight movement some 300,000 times, constructing a cocoon in which it intends to spend the chrysalis stage where it is in a state of sleep and casting off its skin. After this the pupae begin the sixteen days that would normally result in the miracle of transformation to a winged being - the moth. However, if the pupa (chrysalis) remains alive it will begin to secrete an alkali, which eats its way through the cocoon, ruining the silk threads. Therefore during the commercial production of silk, only enough adult moths are allowed to emerge to ensure continuation of the species. Most of the remainder of the silkworms are killed by heat, e.g. immersion in boiling water, steaming or drying in an oven.

Hundreds Die

The amount of useable silk from each cocoon is small. One hectare of mulberry trees yields 11.25 tonnes of leaves, producing around 200kg of cocoons, but just 40kg of raw silk. The silk yield is many times smaller than this in countries such as Thailand, where the silk is reeled by hand rather than by machine. So it takes hundreds of tiny lives to produce just one silk scarf or tie.

Stud Bank & Breeding Research

A limited number of pupae are allowed to complete their chrysalis stage, the resulting silk moths being the stud bank that produces eggs to breed future generations of silkworm.

Much research has been carried out on silkworm breeding or sericulture worldwide over centuries and it continues today. Researchers are keen to establish a certain type of silkworm variety typically for low cost cocoons, disease resistance, high temperature resistance, polyphagy (ability to utilise more than one type of food), and choice quality silk. As with other types of animal farming industries, biotechnology is well established.

Thai Silk Production

The Thai silk moth is adapted to tropical conditions and is multivoltine, producing at least ten batches of eggs each year. Silk from the Thai moth is hand reeled from green cocoons. These are cocoons that still contain the live pupae. These small cocoons do not have the pupae 'stifled' or killed prior to the thread being unwound, as that would make it difficult to reel. The green cocoons are placed in hot, nearly boiling water, which loosens the end of the thread. With less than 10 days available before the moths emerge and ruin the cocoon, the Thai workers may run out of time, limiting the scale of the industry. Even experienced workers rarely produce more than 300g per day. The pupae may be eaten by local workers. Similar production techniques have been used in India, although increasingly Indian silk is woven using machines.

Chinese & Japanese Silk Production

The moth favoured in China and Japan is univoltine or bivoltine, producing one or two batches of eggs annually, which enter a diapausal state (suspended development) and can then be treated to induce hatching at a commercially convenient time. Cocoons are large and lend themselves to machine reeling, offering a long, continuous filament. The adult moths retained for reproduction purposes are too fat to fly, as the best fliers do not produce as much silk. The stifled or dead pupae are usually composted to feed the mulberry trees.

Whilst the tropical silkworm favoured by Thailand is a natural, hardy creature quite capable of surviving in the wild state, the larvae farmed by the industrialised mass production techniques of China and Japan are selectively bred creatures aimed at maximum output for minimum input.

The Silk Thread

Silk is a continuous filament fibre consisting of fibroin protein secreted from two salivary glands in the head of each larva and a gum called sericin which cements the two filaments together. Silk must be reeled off the cocoon quickly before the pupa begins to rot and taint the thread with unpleasant smells. The cocoon is then softened in hot water to remove the sericin, which frees the silk filament ends for reeling or filature. Single filaments are drawn from cocoons in water bowls and combined to form yarn. This yarn is drawn under tension through several guides and eventually wound onto reels. The yarn is dried, packed according to quality and is now raw silk ready for marketing. The worn and withered body of what was intended to become the wondrous flying creature slips silently away.

Fibre Properties

Silk is a natural protein fibre containing about 70-75% of actual fibre fibroin and about 25-30% sericin. Silk filaments are very fine and long - as much as 300 to 900 metres in length. Silk has a high natural lustre and sheen of a white or cream colour and is one of the strongest fibres at 2.6 to 4.8 grams per denier. When it is dry the elongation (elastic recovery) varies from 10-25% and when wet it will elongate as much as 33-35%. Silk has a relatively high standard moisture regain of 11%. At saturation the regain is 25-35%. Silk can be dyed before or after it has been woven into a cloth. It can be woven or knitted.

Types of Silk

Next, the raw silk is twisted into a strand sufficiently strong for weaving or knitting. This procedure is called throwing, and prevents the thread from splitting into its constituent fibres. Four different types of silk thread may be produced from this procedure: crepe, tram, thrown singles and organzine. Crepe is made by twisting individual threads of raw silk, doubling two or more of these together, and then twisting them again. Tram is made by twisting two or more threads in only one direction. Thrown singles are individual threads that are twisted in only one direction. Organzine is a thread made by giving the raw silk a preliminary twist in one direction and then twisting two of these threads together in the opposite direction. In general, organzine thread is used for the warp threads of materials, tram threads for the weft or filling, crepe thread for weaving crinkly fabrics and a single thread for sheer fabrics.

Broken or waste filaments and damaged cocoons are retained, treated to remove the sericin, and combed. This is then processed into yarn, marketed as spun silk, which is inferior in character to the reeled product and much cheaper. Low grade silk is made from damaged cocoons that were spoiled by emerging moths used for breeding stock. Filaments from the coarse outer portion of the cocoon, which is removed by brushing before reeling, and the inner portion of the cocoon, which remains after reeling the raw silk, are mixed with silk from damaged cocoons to make low grade silk.

In common with all other animal production systems, nothing is wasted if it can be sold.

After the silk is harvested from the cocoons it is brought to the weavers for dyeing and preparation for weaving. Today most dyes are chemical although a lac (insect) dye was once used as well as plant dyes.

Another product of sericulture is silkworm gut. Immediately before the cocoon stage, pupae are killed by immersion in an acid bath. Their bodies are opened and the fluid, which hardens upon contact with the air and would otherwise be used to build the cocoon, is removed from their silk glands. This 'gut' was once favoured by surgeons for stitching and by anglers for lines, but has now been almost entirely replaced by nylon, although it still figures in some surgical and contraceptive applications.

World Silk Production

World silk production has more than doubled during the last 30 years in spite of the availability of man-made fibres. China and Japan have been the main silk producers, together manufacturing more than half of the world production each year. Chinese silk is highly prized throughout the world. Since 1949 silk making methods have been modernized and silk is of better quality.

World Raw Silk Production

Year Metric Tonnes
1938 56, 500
1970 41, 000
1980 55, 315
1985 59, 232
1990 69, 120
1992 80, 934
1993 89, 982
1994 95, 498
1995 91, 476
1996 83, 670

Say No to Silk

Silk is used for suits, coats, trousers, jackets, shirts, ties, lingerie, hosiery, gloves, lace, curtains, linings and handbags. Synthetic fibres such as nylon and polyester are stronger than silk and lower in price. In common with western factory farming techniques, the main areas of silk production are labour-intensive, automated and soul-less. The terminology - stifled for killed and crop for pupae - echoes the denial that we are dealing with living creatures which are awe inspiring when one considers their metamorphic life-cycle. Plant fibres are capable of producing some amazing fabrics. Fibres from the pineapple, for example, may be made into fabrics as strong and lustrous as any silk. Synthetic fibres e.g. nylon produced from minerals, polyester from petroleum spirit (Terylene, Dacron) or acrylic from oil and coal (Courtelle, Orlon, Dralon) also have their place.

Glossary
Biotechnology - using living organisms in industrial research
Chrysalis - pupa case
Cocoon - silken sheath spun by insect larvae in passing into the pupa stage
Crop - pupae
Fibroin - silk protein
Filament - fibre
Filature - reeling
Green cocoons - cocoons containing live pupae
Imago - adulthood
Larva - animal in an immature but active state
Moult - shed skin
Mulberry leaves - leaves from the Mulberry tree on which silkworms feed
Pebrine disease - parasitic disease of the silkworm
Polyphagy - a habit of eating many different types of food
Pupa - an insect between the usually passive stage of larva and adulthood or imago
Pupate - to become a pupa
Sericin - gum produced from the silk gland
Sericulture - silkworm breeding
Sericteries - modified salivary glands or silk glands on the mouthpart of the larvae
Silk Road - world's longest road from Eastern China to the Mediterranean
Spinneret - glandular opening on the silkworm where the silk is produced
Stifled - killed


The Story of Thai Silk

I spent the last couple weeks in Thailand and one of the main souvenirs I wanted to bring back was Thai silk. Unfortunately I didn’t get a chance to witness the production of this silk firsthand but I wanted to share the story of this unique fabric to others as well.

Thai silk is produced from the cocoons of Thai silkworms. Thai weavers, mainly from the Khorat Plateau in the northeast region of Thailand, raise the caterpillars on a steady diet of mulberry leaves. Khorat is the center of the silk industry in Thailand and a steady supplier of rose Thai silk for many generations. Since traditional Thai silk is hand woven, each silk fabric is unique and cannot be duplicated through commercial means. This silk has traditionally been reserved for special occasions due to its high cost so its local consumption is relatively low.

To be able to identify genuine Thai silk easily, Thailand's Agriculture Ministry uses a peacock emblem to authenticate Thai silk and protect it from imitations. The peacock emblem serves as a guarantee of quality and it comes in four different colors based on specific silk types and production process. These are the following:

  • Gold peacock: Indicates the premium Royal Thai Silk, a product of native Thai silkworm breeds and traditional hand-made production.
  • Silver peacock: Indicates Classic Thai Silk, developed from specific silkworm breeds and hand-made production.
  • Blue peacock: Indicates Thai Silk, a product of pure silk threads and with no specific production method (allows chemical dyes).
  • Green peacock: Indicates Thai Silk Blend, a product of silk blended with other fabrics and with no specific production method.

Local consumption is relatively low for traditional Thai silk. In the 1950s and 60s, American Jim Thompson recognized that Thai silk could have great appeal in US and UK and created a large company that mimics the traditional Thai silk for international customers. Even his house has become a major tourist attraction especially with his contributions to the industry and subsequent suspicious disappearance.

You can see more contributions to Thai silk in the Queen Sirikit Museum of Textiles in Bangkok. Its founding in 2003 was to create public awareness of Thai identity and culture, and the beauty of Thai traditional textiles, through research, exhibition, and interpretation


Thai Woman Boiling Silk Cocoons - History

What is Thai silk?
Silk is the natural filament produced by the salivary glands of silkworms which are a type of moth that feeds on the mulberry bush. Silkworms are caterpillars, not worms. They spin their cocoons using a complex set of mechanisms within their bodies when they change from larva into pupa. Thai silk is produced by Thai caterpillars raised on Thai mulberry leaves by Thai weavers in Thailand, primarily on the Korat Plateau in the country's northeast region. Chaiyaphum is just north of Korat province.

Raw silk is bumpy and irregular. The completed cocoon is pulled from the mulberry bush and placed in a vat of boiling water, which separates the silk thread of the cocoon from the caterpillar inside.

The silk from Thailand's caterpillars varies in color from light gold to very light green. A cocoon is comprised of one thread that is 500-1,500 meters long. A single filament is too thin to use alone so many threads are combined to make a thicker, more practical fiber.

Our weavers wash these raw silk threads, bleach them, then soak them in vats of hot dyes. Afterwards, they wash the silk thread again, stretch it, and put it through a final dying process. When that is finished, they wind the threads onto spools or drums in preparation for weaving using traditional hand operated looms.

What's the difference between machine woven and hand woven Thai silk?
Every piece of hand woven Thai silk is a timeless, unique work of textile art from the hands of a rural Thai woman. Since it is art work produced by a human, it forever carries an imprint of the character, thoughts, emotions, feelings, spirit and life of the weaver. It's imperfection is the heart of its beauty and the proof of its human creator. Machine woven silk is a wider, monotonously &ldquoperfect&rdquo industrial fabric that can be produced to ISO standards and is more suitable than hand-woven silk for some purposes. We sell both types, wholesale and retail.

What's the difference between Thai silk and that of of other countries?
Thai silk is usually soft but has a relatively coarse texture with uneven, slightly knotty threads. This quality makes it extremely suitable for weaving by hand. Thai silk has a magnificent, rich, exotic beauty and, with proper care, can last a century or more.

Chinese silk tends to be smooth and satiny. Indian silk tends to be softer but more crinkly and uses richer colors. Italian silk tends to strive for a refined and elegant look but this can easily be accomplished anywhere using mechanized weaving.

Why is Thai silk so shiny and lustrous?
Thai Silk has triangular fibers which reflect light like prisms. It also has layers of protein that gives it a natural sheen and makes it lustrous and smooth. Silk is an insect fiber and superior to any animal or plant fiber. Thai silk fiber is strong but lightweight, elastic but supple.

What is smooth Thai silk?
Smooth Thai silk has a shiny, satin-like finish. It's suitable for all purposes, particularly clothing and interior decorating. The &ldquostandard&rdquo width was formerly about 37 inches/94 centimeters and is available in 2-ply and sometimes 4-ply. Starting in 2003, our Thai weavers began producing silk at a standard width of 40 inches. (Click here for sample!)

What is rough Thai silk?
"Rough" Thai silk is beautiful and textured but not really coarse or rough. It is soft. It's also sometimes called &ldquonubby&rdquo Thai silk but as of mid-2006 we begain calling all these weaves Thai dupioni. It's highly suitable for silk drapes and silk curtains -- and silk upholstery fabric if cotton backing is affixed. It's also great for other interior design applications but it's a fantastic fashion fabric currently popular with designers of luxury apparel & bridal gowns! The standard width used to be about 37 inches (94 cm) but starting in 2003, our weavers began producing silk at a standard width of 40 inches. Two-ply dupioni Thai silk is extremely appropriate for scarves. Four-ply dupioni is more commonly woven and excellent for silk drapes and silk curtains. All colors and designs are available. Here's an example.

What is two-tone Thai silk?
Two tone iridescent Thai silk is way cool and extremely pleasant to the eyes. Depending on the angle at which it is viewed, the fabric color changes! We produce this iridescent effect by using two different colors when we weave the cloth. Our 550% enlargements of actual fabric used for our page backgrounds clearly shows the contrasting colors of the warp (vertical thread) and weft (horizontal thread). You can choose the the colors of the weft and warp to produce your own unique two-tone Thai silk. (Click here for sample!)

What is striped Thai silk?
When we talk about &ldquostriped&rdquo we do not mean &ldquostripes" produced by color variations as as in a normal material design (although this is also possible). This is a weaving technique. We produce striped Thai silk by alternating between smooth Thai silk and rough Thai silk during weaving to produce a physical pattern in the material. This can be used in conjunction with a color pattern as well. Many patterns are available and &ldquostriped Thai silk&rdquo may not actually result in &ldquostripes&rdquo at all. An infinite variety of designs are possible and you can commission your own. We are flexible and can weave your own designs. It's very suitable for home decoration, curtains, furniture coverings, interior design applications, wall coverings, and even clothing! (Click here for sample!)

How Thai Silk is Made?
All our silk is made in Thailand using a rather complicated process. Although there are now many enormous, automated factories making silk fabric all over the world, all the material sold by World of Thai Silk is created by individual, independent, women weavers at their homes in Northeast Thailand using traditional methods and their own looms. This is why widths of the cloth varies and each bolt of cloth is a unique work of art.

The process begins by raising silkworms on mulberry leaves. When they are mature, the silkworms spin silk cocoons. The cocoons are then degummed by the weavers using special chemicals.

They boil the degummed silk with various natural or chemical dyes at 90 degrees Celsius, constantly stirring the silk to get uniform color. The dyed silk thread is then dried.

The dried and dyed silk is then spun into yarn on wooden or plastic tubes. The women use this yarn to spin the fabulous Thai silk fabric we sell.

How to Clean Silk? How to Care for Silk?
Dry cleaning is the best way to keep Thai silk in good condition and maintain its original beauty, luster, and texture. You can also hand wash it in lukewarm water using the mildest soap. Add a table spoonful of clear white vinegar added to the final rinse.

Never wring your Thai silk! Dry it in the shade, preferably where there's a mild breeze, and be sure it's well supported.

Iron Thai silk on the inside of the garment while it is still slightly damp. If already dry, apply a damp cloth on the outside and iron through the cloth. Properly cared for Thai silk can easily last a century and be passed on to your children and grandchildren. For more info see this page.

How can I recognize 100% pure silk and imitation silk made from polyester? How can I test silk?
The four basic methods for determining true silk are by 1) considering the price looking carefully at the 2) weave and 3) luster and 4) by burning a piece!

1) Pure real silk costs 6-10 times as much as imitation silk made from polyester.

2) Our real pure Thai silk weave is completely hand made and the filament is a natural fiber with clearly visible small flaws and joins in the thread along the warp and the weft. Imitation silk made from polyester is a machine-made fabric and has a perfect surface with no flaws or bumps.

3) Luster also shows whether a fabric is real or imitation. Our pure Thai silk is made with one color for the warp and another color for the weft. This produces the sheen and luster of our silk and creates the unique two tones and blends which change depending on the angle of light. Imitation polyester silk shines white regardless of the angle of the light.

4) If you burn Thai silk (a thread or two is enough) with a flame, it leaves fine ash and smells like burning hair. When you take the flame away it stops burning. If you burn imitation polyester silk with a flame, it drips, burns with a black smoke, and continues to burn after the flame is taken away . The three different sizes of digital images for each silk swatch on the World of Thai Silk web site make it easy for you to see the unique qualities of real Thai silk so you probably won't need to resort to the burn test.

Who discovered silk? History of Thai Silk .
Empress Si Ling Chi of China is credited with discovering silk. While sitting under a mulberry tree in a palace garden having tea, a silkworm's cocoon reportedly fell out of the tree into her cup. While removing it from her tea, she discovered the fine silk filament of the cocoon beginning to unravel.

The Chinese guarded the secret of silk for millenniums by putting to death anyone found guilty of smuggling silkworm eggs, cocoons, or mulberry seeds. Silk became the cloth of emperors and royalty and a great source of wealth. However, about 1900 years ago a Chinese princess who married an Indian prince is reported to have succesfully smuggled silkworm eggs out of China in her headdress and then fed them with the leaves of Indian mulberry trees.

Since then, silk production has spread to other Asian countries and archaeologist have found silk 3,000 years old in the ruins of Baan Chiang, Thailand, which many of them consider the earliest civilization in Southeast Asia. Thais have developed a type of silk that is considered one of the finest fabrics in the world. They use a unique manufacturing process and have unique patterns and colors.

What is hand woven ikat silk fabric (mudmee)?
Hand woven Mudmee Thai silk (also know as &ldquoikat") comes from the northeast of Thailand which is called &ldquoIsan&rdquo and comprised of 17 provinces and situated on the Khorat plateau. The Mekong River borders the whole region on its eastern and northern frontiers with Laos. Its western and southern frontiers are mountain ranges that form the rim of the plateau.

The intricate traditional geometric and zoomorphic motifs of mudmee Thai silk have been handed down for centuries. The designs and patterns in mudmee are created primarily by using various colors in the weft (left to right threads) of the fabric. The people who migrated into the central and Mekhong River Basin area of northeast Thailand from Pakse and Savankhet Laos brought their weaving skills with them. In the 19th century, Thailand's King Rama V introduced advanced technology which created the foundation of the country's large silk industry.

Mudmee fabric is usually half a solid or two-tone color and the other half the mudmee pattern.

Thailand's northeast was not always the arid area that it is today. As recently as 1960, forests were lush and abundant and natural resources for dyes were plentiful. Jim Thomson introduced the permanent chemical dyes that are now so common.

Traditionally, everyday dress was practical and usually quite plain. However, a great deal of time and expense was spent to weave the fabric for weddings, temple ceremonies, funerals, meeting high ranking officials, and spirit appeasing ceremonies, resulting in spectacular quality as well as complex techniques and designs.

What is taffetta?
Taffetta is a silk fabric made from white silk cocoons. It varies from country to country. Here's more information.

What is dupion silk?
Dupion is an interesting textured Thai silk fabric made using a mixture of silk from both long, smooth, white cocoons and short, rough, yellow cocoons. Many other terms are used to refer to this silk fabric and more detailed information is found on our page &ldquoDupioni Thai Silk Fabric&rdquo.

What is the difference between white and yellow cocoons?
White cocoons are smooth, white and about 60-100 meters long. A yellow cocoon is short, rough, yellow and about 20-30 meters long. However, every cocoon of both types also has three parts which vary in quality and character. The silk threads of the outer part are large, short and more textured filaments. In the next part of the cocoon, the filaments are smoother and longer than the first type but not as fine or expensive as the third type which is best.

Is the "Silk Road" or "Silk Route" in Thailand?
German academic Ferdinand von Richthofen is credited with inventing the term "Silk Road" or "Silk Route" which was actually neither a road nor a route but rather a trade network. It started in China and stretched across South Asia to Middle East Asia and the eastern Mediterranean Sea. It probably bypassed Thailand. Few merchants or travellers went from one end of the complex network of passages and routes to the other. Silk, spices and other low-weight, low-volume, high-value luxury items were traded in relay-fashion along the Silk Road from one trader to the next.


Silk day when cotton was king and silk was queen

FEATURE — When it came to the early days of Southern Utah’s Dixie, silk production – or sericulture – seemed a natural fit. Mulberry trees grew well and the cost was minimal. As an added advantage, production did not take up additional land or extra hands that would be better suited for hard labor it could be assigned to one of the world’s oldest female service organizations, the Relief Society of The Church of Jesus Christ of Latter-day Saints.

Statue of Samuel J. Adair, leader of first settlers, Washington City Museum, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Southerners were first called to Dixie to grow cotton. The first 10 families arrived in 1857, led by Samuel Adair. They called the place “Adair Springs” but later changed it to “Washington City” after former President George Washington.

While cotton may have been the draw to the southern part of the territory, silk was a subject close to the heart of Brigham Young, then president of the LDS church. Even though he was born a poor American in Vermont, Young served a 20-month mission in Manchester, England, from 1840-1841. There he was exposed to the many silk-weaving looms and silk weavers the Huguenots who emigrated from Lyons, France, to England in order to escape religious persecution in the 16 th and 17 th centuries continued silk production.

According to silk legend, Greek Emperor Justinian encouraged two monks to steal some silkworm eggs out of China in the 6th century. The monks also pinched a few seeds of the mulberry tree.

Prior to that, the Chinese had carefully guarded the secret of silk for ages. According to Chinese records, the technique was discovered by Si-ling-chi, wife of the “Yellow Emperor” Huang-ti, in about 2700 B.C. By some accounts, she discovered the secret after a silkworm cocoon fell into her cup of tea, and as she pulled it out, she realized she could unravel its exquisite thread.

Silkworm and cocoon, Oct. 17, 2011, location not specified | Photo by Srithern via Wikimedia Commons, St. George News

A moth hatching from a cocoon destroys the thread. Therefore, to harvest silk, at about six weeks and 3 inches long, the worm in the cocoon has spun its own coffin. The process of placing the cocoon in boiling water not only kills the pupae but softens the binding agent sericin so that the filaments may be unwound.

From there, raw silk strands are twisted together until a fiber of sufficient strength for knitting or weaving is produced. Different twisting methods produce a different type of thread crinkly fabrics are made with crepe, while sheer cloth is made with single thread. Spun silk is comprised of broken filaments that have been processed into a yarn.

In the mid-1850s, Young imported 100,000 mulberry trees from France. He planted them up and down the streets of Salt Lake and brought them to St. George in the 1860s. He dispersed trees all along the way and also planted them at his winter home.

Utah women wearing silk, including Zina Young, circa late-19th century, location not specified | Photo courtesy of Utah State Historic Society, St. George News

Young sent one of his wives, Zina Diantha H. Young, also an advocate for women’s suffrage and president of the Deseret Silk Association, to travel throughout the territory. She would speak, organize and teach classes in sericulture. Even though Zina Young often had nightmares about squirmy silkworms, she stayed faithful to her assignment, Andrew Karl Larson wrote in his book “I was Called to Dixie.”

As she traveled and spoke, Zina Young handed out small mulberry leaves about an inch in diameter covered with tiny worms. The women took them home and began feeding them. The caterpillars molted and cast their skins in about 10 days. They grew by leaps and bounds. With insatiable appetites, they devoured such quantities of leaves that women and children could scarcely supply.

Many people began growing silkworms more out of curiosity than desiring to make cloth. Those who didn’t have mulberry trees had to gather from neighbors, and some fed silkworms lettuce, although lesser-quality silks are made from silkworms that might be fed Osage orange and lettuce, Larson said.

Mulberry trees in bloom in the Bloomington area of St. George, Utah, March 21, 2017 | Photo by Joyce Kuzmanic, St. George News

In 1869, John D. Lee, a busy and enterprising pioneer planted a grove of several hundred mulberry trees enclosed with a stone fence around a half-acre at his Washington home. He figured he could produce four or five crops of cocoons because of the long warm season. He kept the trees hedged so women and children could pick the leaves without having to climb the trees.

In an address to the Cotton Mission community in 1872, Brigham Young said, “If we profess to know how to use silk dresses, we should first learn how to produce them.”

Many of the women to whom Young spoke were members of the Relief Society, a group which began in 1842 in Nauvoo, Illinois, but which experienced a hiatus following the exodus of the Nauvoo pioneers. In 1868, the group began to re-establish societies in the Cotton Mission. The women remembered Emma Smith, the first Relief Society president, declaring “We are going to do something extraordinary!”

Western European immigrants reel silk, Washington City, Utah, circa late-18th century | Photo courtesy of Utah State Historical Society, St. George News

As they are today, priorities of the Relief Society were relief of the poor and destitute and care of widows and orphans. The women conducted business and taught classes, in addition to making clothing, rugs and quilts.

The women’s service projects required more space than a room in a church building could offer therefore, the women built their own buildings, raising money sometimes by bake sales and dinners. However, in the settlement of Washington city, the women of Relief Society also engaged in commercial, agricultural and even industrial projects, Larson wrote.

The completion of the Washington Relief Society Hall in 1875 provided a meeting house, as well as a co-op store – Zions Co-op Rio Virgin Manufacturing Company – post office and a place where the women laid out the dead, since there were no undertakers at that time.

The Washington community continued to grow silkworms, and before long the silk association had thousands of silk cocoons and didn’t know exactly what to do with them. Armand Hof, an expert in reeling, spinning and weaving silk, came to Washington during the 1880s to take charge of weaving at the Washington Cotton Factory.

Crepe silk hand-loomed and hand-stitched dress on display at the Washington City Museum, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

The factory made a place for silk looming and eventually became part of the Zion Co-op Mercantile Institute – or ZCMI – system, which served more than 150 communities in Utah with retail commodities.

Many pioneer women made beautiful silk dresses from homegrown silkworm thread, and an American flag made of Utah silk was flown at the 1893 Chicago World’s Fair.

However, silk production came to an end in 1905, largely as a result of the massive quantity of cocoon necessary – approximately 2,500 – to make just one pound of silk. This, combined with the price the state Legislature authorized the newly formed Utah Silk Commission to pay for the silk, conspired to keep Southern Utah sericulture from being profitable.

But beyond the potential profits, the most significant yield of the silk home industry was the spirit of adventure, cooperation, obedience, perseverance and accomplishment of the thousands of participating Relief Society sisters.

Visiting the Washington City historical sites

Washington Relief Society Hall, Washington City, Utah, March 16, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

The Washington Relief Society Hall is the only remaining late 19th century building in Washington City and the church’s oldest standing Relief Society building. Located at the corner of 100 West and Telegraph Street, this small building represents Greek revival architecture, the first allusion to high style used in early Utah. It was made of Utah adobe, an economical and available building material. The changing tastes in building style favored Victorian, causing most other early buildings to be lost.

From 1972-75 the Relief Society women ran an official outlet of Zion’s Co-operative Mercantile Institution. Today, the building and grounds may be rented and used for social events. For scheduling and rental of this facility, contact Don or Rebecca Young at telephone 435-656-1590.

Washington City Museum is located on the northeast corner of Telegraph Road and Main Street. It is open from 9 a.m. to 5 p.m. Monday, Tuesday, Wednesday and Friday, and from 10 a.m. to 3 p.m. Thursday and Saturday.

Adair Spring Monument is located at 120 N. 200 East and commemorates the original settlers who founded Washington City.

The Cotton Factory and Mill – now Star Nursery – is located at 385 W. Telegraph Rd.

Photo gallery follows below. Click on photos to enlarge, use left-right arrow keys to cycle through the gallery.

Adair Spring monument, the birthplace of Utah's Dixie, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Cotton Factory, Washington City, Utah, March 16, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Crepe silk hand-loomed and hand-stitched dress on display at the Washington City Museum, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Early photo of workers in the Cotton Factory ca. 1870-90, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Early school desks in Washington City's first elementary school, now the Washington City Museum, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Western European immigrants reel silk ca. late-18th century, Washington City, Utah | Photo courtesy of Utah State Historical Society, St. George News

Santa Clara Relief Sociey Building, Santa Clara, Utah, March 16, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Statue of John D. Lee, Washington City Museum, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Statue of Samuel J. Adair, leader of first settlers, Washington City Museum, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Pioneer woman statue at Washington Relief Society Hall, Washington City, Utah, March 16, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Utah women wearing silk, including Zina Young, ca. late-19th century, location not specified | Photo courtesy of Utah State Historic Society, St. George News

Washington City Museum, Washington City, Utah, March 22, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Washington Relief Society Hall, Washington City, Utah, March 16, 2017 | Photo by and courtesy of Jim Lillywhite, St. George News

Western European immigrants harvesting silk cocoons ca. late-18th century, Washington City, Utah | Photo courtesy of BYU library, St. George News

Silkworm on mulberry leaf, date and location not specified | Stock image, St. George News

Silkworm and cocoon, Oct. 17, 2011, location not specified | Photo by Srithern via Wikimedia Commons, St. George News

About the series “Days”

“Days” is a series with St. George News contributor, feature writer and photographer Kathleen Lillywhite. She said:

I write my stories for people who say, ‘What is there to do around St. George?’ and for new folks just moving into this area.


Contents

The word silk comes from Old English: sioloc, from Ancient Greek: σηρικός , romanized: sērikós, "silken", ultimately from the Chinese word "sī" and other Asian sources—compare Mandarin "silk", Manchurian sirghe, Mongolian sirkek. [4]

The production of silk originated in China in the Neolithic period although, it would eventually reach other places of the world ( Yangshao culture, 4th millennium BC). Silk production remained confined to China until the Silk Road opened at some point during the latter part of the 1st millennium BC, though China maintained its virtual monopoly over silk production for another thousand years.

Wild silk

Several kinds of wild silk, produced by caterpillars other than the mulberry silkworm, have been known and spun in China, South Asia, and Europe since ancient times, e.g. the production of Eri silk in Assam, India. However, the scale of production was always far smaller than for cultivated silks. There are several reasons for this: first, they differ from the domesticated varieties in colour and texture and are therefore less uniform second, cocoons gathered in the wild have usually had the pupa emerge from them before being discovered so the silk thread that makes up the cocoon has been torn into shorter lengths and third, many wild cocoons are covered in a mineral layer that prevents attempts to reel from them long strands of silk. [5] Thus, the only way to obtain silk suitable for spinning into textiles in areas where commercial silks are not cultivated was by tedious and labor-intensive carding.

Some natural silk structures have been used without being unwound or spun. Spider webs were used as a wound dressing in ancient Greece and Rome, [6] and as a base for painting from the 16th century. [7] Caterpillar nests were pasted together to make a fabric in the Aztec Empire. [8]

Commercial silks originate from reared silkworm pupae, which are bred to produce a white-colored silk thread with no mineral on the surface. The pupae are killed by either dipping them in boiling water before the adult moths emerge or by piercing them with a needle. These factors all contribute to the ability of the whole cocoon to be unravelled as one continuous thread, permitting a much stronger cloth to be woven from the silk. Wild silks also tend to be more difficult to dye than silk from the cultivated silkworm. [9] [10] A technique known as demineralizing allows the mineral layer around the cocoon of wild silk moths to be removed, [11] leaving only variability in color as a barrier to creating a commercial silk industry based on wild silks in the parts of the world where wild silk moths thrive, such as in Africa and South America.

China

Silk use in fabric was first developed in ancient China. [12] [13] The earliest evidence for silk is the presence of the silk protein fibroin in soil samples from two tombs at the neolithic site Jiahu in Henan, which date back about 8,500 years. [14] [15] The earliest surviving example of silk fabric dates from about 3630 BC, and was used as the wrapping for the body of a child at a Yangshao culture site in Qingtaicun near Xingyang, Henan. [12] [16]

Legend gives credit for developing silk to a Chinese empress, Leizu (Hsi-Ling-Shih, Lei-Tzu). Silks were originally reserved for the Emperors of China for their own use and gifts to others, but spread gradually through Chinese culture and trade both geographically and socially, and then to many regions of Asia. Because of its texture and lustre, silk rapidly became a popular luxury fabric in the many areas accessible to Chinese merchants. Silk was in great demand, and became a staple of pre-industrial international trade. Silk was also used as a surface for writing, especially during the Warring States period (475-221 BCE). The fabric was light, it survived the damp climate of the Yangtze region, absorbed ink well, and provided a white background for the text. [17] In July 2007, archaeologists discovered intricately woven and dyed silk textiles in a tomb in Jiangxi province, dated to the Eastern Zhou dynasty roughly 2,500 years ago. [18] Although historians have suspected a long history of a formative textile industry in ancient China, this find of silk textiles employing "complicated techniques" of weaving and dyeing provides direct evidence for silks dating before the Mawangdui-discovery and other silks dating to the Han dynasty (202 BC – 220 AD). [18]

Silk is described in a chapter of the Fan Shengzhi shu from the Western Han (202 BC – 9 AD). There is a surviving calendar for silk production in an Eastern Han (25–220 AD) document. The two other known works on silk from the Han period are lost. [12] The first evidence of the long distance silk trade is the finding of silk in the hair of an Egyptian mummy of the 21st dynasty, c.1070 BC. [19] The silk trade reached as far as the Indian subcontinent, the Middle East, Europe, and North Africa. This trade was so extensive that the major set of trade routes between Europe and Asia came to be known as the Silk Road.

The Emperors of China strove to keep knowledge of sericulture secret to maintain the Chinese monopoly. Nonetheless sericulture reached Korea with technological aid from China around 200 BC, [20] the ancient Kingdom of Khotan by AD 50, [21] and India by AD 140. [22]

In the ancient era, silk from China was the most lucrative and sought-after luxury item traded across the Eurasian continent, [23] and many civilizations, such as the ancient Persians, benefited economically from trade. [23]

The silkworms and mulberry leaves are placed on trays.

Twig frames for the silkworms are prepared.

The cocoons are soaked and the silk is wound on spools.

The silk is woven using a loom.

Northeastern India

In the northeastern state of Assam, three different types of indigenous variety of silk are produced, collectively called Assam silk: Muga, Eri and Pat silk. Muga, the golden silk, and Eri are produced by silkworms that are native only to Assam. They have been reared since ancient times similar to other East and South-East Asian countries.

India

Silk has a long history in India. It is known as Resham in eastern and north India, and Pattu in southern parts of India. Recent archaeological discoveries in Harappa and Chanhu-daro suggest that sericulture, employing wild silk threads from native silkworm species, existed in South Asia during the time of the Indus Valley Civilization (now in Pakistan and India) dating between 2450 BC and 2000 BC, while "hard and fast evidence" for silk production in China dates back to around 2570 BC. [24] [25] Shelagh Vainker, a silk expert at the Ashmolean Museum in Oxford, who sees evidence for silk production in China "significantly earlier" than 2500–2000 BC, suggests, "people of the Indus civilization either harvested silkworm cocoons or traded with people who did, and that they knew a considerable amount about silk." [24]

India is the second largest producer of silk in the world after China. About 97% of the raw mulberry silk comes from six Indian states, namely, Andhra Pradesh, Karnataka, Jammu and Kashmir, Tamil Nadu, Bihar and West Bengal. [26] North Bangalore, the upcoming site of a $20 million "Silk City" Ramanagara and Mysore, contribute to a majority of silk production in Karnataka. [27]

In Tamil Nadu, mulberry cultivation is concentrated in the Coimbatore, Erode, Bhagalpuri, Tiruppur, Salem and Dharmapuri districts. Hyderabad, Andhra Pradesh, and Gobichettipalayam, Tamil Nadu, were the first locations to have automated silk reeling units in India. [28]

Thailand

Silk is produced year-round in Thailand by two types of silkworms, the cultured Bombycidae and wild Saturniidae. Most production is after the rice harvest in the southern and northeastern parts of the country. Women traditionally weave silk on hand looms and pass the skill on to their daughters, as weaving is considered to be a sign of maturity and eligibility for marriage. Thai silk textiles often use complicated patterns in various colours and styles. Most regions of Thailand have their own typical silks. A single thread filament is too thin to use on its own so women combine many threads to produce a thicker, usable fiber. They do this by hand-reeling the threads onto a wooden spindle to produce a uniform strand of raw silk. The process takes around 40 hours to produce a half kilogram of silk. Many local operations use a reeling machine for this task, but some silk threads are still hand-reeled. The difference is that hand-reeled threads produce three grades of silk: two fine grades that are ideal for lightweight fabrics, and a thick grade for heavier material.

The silk fabric is soaked in extremely cold water and bleached before dyeing to remove the natural yellow coloring of Thai silk yarn. To do this, skeins of silk thread are immersed in large tubs of hydrogen peroxide. Once washed and dried, the silk is woven on a traditional hand-operated loom. [29]

Bangladesh

The Rajshahi Division of northern Bangladesh is the hub of the country's silk industry. There are three types of silk produced in the region: mulberry, endi and tassar. Bengali silk was a major item of international trade for centuries. It was known as Ganges silk in medieval Europe. Bengal was the leading exporter of silk between the 16th and 19th centuries. [30]

Central Asia

The 7th century CE murals of Afrasiyab in Samarkand, Sogdiana, show a Chinese Embassy carrying silk and a string of silkworm cocoons to the local Sogdian ruler. [31]

Middle East

In the Torah, a scarlet cloth item called in Hebrew "sheni tola'at" שני תולעת – literally "crimson of the worm" – is described as being used in purification ceremonies, such as those following a leprosy outbreak (Leviticus 14), alongside cedar wood and hyssop (za'atar). Eminent scholar and leading medieval translator of Jewish sources and books of the Bible into Arabic, Rabbi Saadia Gaon, translates this phrase explicitly as "crimson silk" – חריר קרמז حرير قرمز.

In Islamic teachings, Muslim men are forbidden to wear silk. Many religious jurists believe the reasoning behind the prohibition lies in avoiding clothing for men that can be considered feminine or extravagant. [32] There are disputes regarding the amount of silk a fabric can consist of (e.g., whether a small decorative silk piece on a cotton caftan is permissible or not) for it to be lawful for men to wear, but the dominant opinion of most Muslim scholars is that the wearing of silk by men is forbidden. Modern attire has raised a number of issues, including, for instance, the permissibility of wearing silk neckties, which are masculine articles of clothing.

Ancient Mediterranean

In the Odyssey, 19.233, when Odysseus, while pretending to be someone else, is questioned by Penelope about her husband's clothing, he says that he wore a shirt "gleaming like the skin of a dried onion" (varies with translations, literal translation here) [33] which could refer to the lustrous quality of silk fabric. Aristotle wrote of Coa vestis, a wild silk textile from Kos. Sea silk from certain large sea shells was also valued. The Roman Empire knew of and traded in silk, and Chinese silk was the most highly priced luxury good imported by them. [23] During the reign of emperor Tiberius, sumptuary laws were passed that forbade men from wearing silk garments, but these proved ineffectual. [34] The Historia Augusta mentions that the third-century emperor Elagabalus was the first Roman to wear garments of pure silk, whereas it had been customary to wear fabrics of silk/cotton or silk/linen blends. [35] Despite the popularity of silk, the secret of silk-making only reached Europe around AD 550, via the Byzantine Empire. Contemporary accounts state that monks working for the emperor Justinian I smuggled silkworm eggs to Constantinople in hollow canes from China. [36] All top-quality looms and weavers were located inside the Great Palace complex in Constantinople, and the cloth produced was used in imperial robes or in diplomacy, as gifts to foreign dignitaries. The remainder was sold at very high prices.

Medieval and modern Europe

Italy was the most important producer of silk during the Medieval age. The first center to introduce silk production to Italy was the city of Catanzaro during the 11th century in the region of Calabria. The silk of Catanzaro supplied almost all of Europe and was sold in a large market fair in the port of Reggio Calabria, to Spanish, Venetian, Genovese and Dutch merchants. Catanzaro became the lace capital of the world with a large silkworm breeding facility that produced all the laces and linens used in the Vatican. The city was world-famous for its fine fabrication of silks, velvets, damasks and brocades. [37]

Another notable center was the Italian city-state of Lucca which largely financed itself through silk-production and silk-trading, beginning in the 12th century. Other Italian cities involved in silk production were Genoa, Venice and Florence.

The Silk Exchange in Valencia from the 15th century—where previously in 1348 also perxal (percale) was traded as some kind of silk—illustrates the power and wealth of one of the great Mediterranean mercantile cities. [38] [39]

Silk was produced in and exported from the province of Granada, Spain, especially the Alpujarras region, until the Moriscos, whose industry it was, were expelled from Granada in 1571. [40] [41]

Since the 15th century, silk production in France has been centered around the city of Lyon where many mechanic tools for mass production were first introduced in the 17th century.

James I attempted to establish silk production in England, purchasing and planting 100,000 mulberry trees, some on land adjacent to Hampton Court Palace, but they were of a species unsuited to the silk worms, and the attempt failed. In 1732 John Guardivaglio set up a silk throwing enterprise at Logwood mill in Stockport in 1744, Burton Mill was erected in Macclesfield and in 1753 Old Mill was built in Congleton. [42] These three towns remained the centre of the English silk throwing industry until silk throwing was replaced by silk waste spinning. British enterprise also established silk filature in Cyprus in 1928. In England in the mid-20th century, raw silk was produced at Lullingstone Castle in Kent. Silkworms were raised and reeled under the direction of Zoe Lady Hart Dyke, later moving to Ayot St Lawrence in Hertfordshire in 1956. [43]

During World War II, supplies of silk for UK parachute manufacture were secured from the Middle East by Peter Gaddum. [44]

A hundred-year-old pattern of silk called "Almgrensrosen"

The necktie originates from the cravat, a neckband made from silk [45] [46] [47]

North America

Wild silk taken from the nests of native caterpillars was used by the Aztecs to make containers and as paper. [48] [8] Silkworms were introduced to Oaxaca from Spain in the 1530s and the region profited from silk production until the early 17th century, when the king of Spain banned export to protect Spain's silk industry. Silk production for local consumption has continued until the present day, sometimes spinning wild silk. [49]

King James I introduced silk-growing to the British colonies in America around 1619, ostensibly to discourage tobacco planting. The Shakers in Kentucky adopted the practice.

The history of industrial silk in the United States is largely tied to several smaller urban centers in the Northeast region. Beginning in the 1830s, Manchester, Connecticut emerged as the early center of the silk industry in America, when the Cheney Brothers became the first in the United States to properly raise silkworms on an industrial scale today the Cheney Brothers Historic District showcases their former mills. [51] With the mulberry tree craze of that decade, other smaller producers began raising silkworms. This economy particularly gained traction in the vicinity of Northampton, Massachusetts and its neighboring Williamsburg, where a number of small firms and cooperatives emerged. Among the most prominent of these was the cooperative utopian Northampton Association for Education and Industry, of which Sojourner Truth was a member. [52] Following the destructive Mill River Flood of 1874, one manufacturer, William Skinner, relocated his mill from Williamsburg to the then-new city of Holyoke. Over the next 50 years he and his sons would maintain relations between the American silk industry and its counterparts in Japan, [53] and expanded their business to the point that by 1911, the Skinner Mill complex contained the largest silk mill under one roof in the world, and the brand Skinner Fabrics had become the largest manufacturer of silk satins internationally. [50] [54] Other efforts later in the 19th century would also bring the new silk industry to Paterson, New Jersey, with several firms hiring European-born textile workers and granting it the nickname "Silk City" as another major center of production in the United States.

World War II interrupted the silk trade from Asia, and silk prices increased dramatically. [55] U.S. industry began to look for substitutes, which led to the use of synthetics such as nylon. Synthetic silks have also been made from lyocell, a type of cellulose fiber, and are often difficult to distinguish from real silk (see spider silk for more on synthetic silks).

Malaysia

In Terengganu, which is now part of Malaysia, a second generation of silkworm was being imported as early as 1764 for the country's silk textile industry, especially songket. [56] However, since the 1980s, Malaysia is no longer engaged in sericulture but does plant mulberry trees.

Vietnam

In Vietnamese legend, silk appeared in the first millennium AD and is still being woven today.

The process of silk production is known as sericulture. [57] The entire production process of silk can be divided into several steps which are typically handled by different entities. [ clarification needed ] Extracting raw silk starts by cultivating the silkworms on mulberry leaves. Once the worms start pupating in their cocoons, these are dissolved in boiling water in order for individual long fibres to be extracted and fed into the spinning reel. [58]

To produce 1 kg of silk, 104 kg of mulberry leaves must be eaten by 3000 silkworms. It takes about 5000 silkworms to make a pure silk kimono. [59] : 104 The major silk producers are China (54%) and India (14%). [60] Other statistics: [61]

The environmental impact of silk production is potentially large when compared with other natural fibers. A life-cycle assessment of Indian silk production shows that the production process has a large carbon and water footprint, mainly due to the fact that it is an animal-derived fiber and more inputs such as fertilizer and water are needed per unit of fiber produced. [62]

Physical properties

Silk fibers from the Bombyx mori silkworm have a triangular cross section with rounded corners, 5–10 μm wide. The fibroin-heavy chain is composed mostly of beta-sheets, due to a 59-mer amino acid repeat sequence with some variations. [63] The flat surfaces of the fibrils reflect light at many angles, giving silk a natural sheen. The cross-section from other silkworms can vary in shape and diameter: crescent-like for Anaphe and elongated wedge for tussah. Silkworm fibers are naturally extruded from two silkworm glands as a pair of primary filaments (brin), which are stuck together, with sericin proteins that act like glue, to form a bave. Bave diameters for tussah silk can reach 65 μm. See cited reference for cross-sectional SEM photographs. [64]

Silk has a smooth, soft texture that is not slippery, unlike many synthetic fibers.

Silk is one of the strongest natural fibers, but it loses up to 20% of its strength when wet. It has a good moisture regain of 11%. Its elasticity is moderate to poor: if elongated even a small amount, it remains stretched. It can be weakened if exposed to too much sunlight. It may also be attacked by insects, especially if left dirty.

One example of the durable nature of silk over other fabrics is demonstrated by the recovery in 1840 of silk garments from a wreck of 1782: 'The most durable article found has been silk for besides pieces of cloaks and lace, a pair of black satin breeches, and a large satin waistcoat with flaps, were got up, of which the silk was perfect, but the lining entirely gone . from the thread giving way . No articles of dress of woollen cloth have yet been found.' [65]

Silk is a poor conductor of electricity and thus susceptible to static cling. Silk has a high emissivity for infrared light, making it feel cool to the touch. [66]

Unwashed silk chiffon may shrink up to 8% due to a relaxation of the fiber macrostructure, so silk should either be washed prior to garment construction, or dry cleaned. Dry cleaning may still shrink the chiffon up to 4%. Occasionally, this shrinkage can be reversed by a gentle steaming with a press cloth. There is almost no gradual shrinkage nor shrinkage due to molecular-level deformation.

Natural and synthetic silk is known to manifest piezoelectric properties in proteins, probably due to its molecular structure. [67]

Silkworm silk was used as the standard for the denier, a measurement of linear density in fibers. Silkworm silk therefore has a linear density of approximately 1 den, or 1.1 dtex.

Comparison of silk fibers [68] Linear density (dtex) Diameter (μm) Coeff. variation
Moth: Bombyx mori 1.17 12.9 24.8%
Spider: Argiope aurantia 0.14 3.57 14.8%

Chemical properties

Silk emitted by the silkworm consists of two main proteins, sericin and fibroin, fibroin being the structural center of the silk, and serecin being the sticky material surrounding it. Fibroin is made up of the amino acids Gly-Ser-Gly-Ala-Gly-Ala and forms beta pleated sheets. Hydrogen bonds form between chains, and side chains form above and below the plane of the hydrogen bond network.

The high proportion (50%) of glycine allows tight packing. This is because glycine's R group is only a hydrogen and so is not as sterically constrained. The addition of alanine and serine makes the fibres strong and resistant to breaking. This tensile strength is due to the many interceded hydrogen bonds, and when stretched the force is applied to these numerous bonds and they do not break.

Silk is resistant to most mineral acids, except for sulfuric acid, which dissolves it. It is yellowed by perspiration. Chlorine bleach will also destroy silk fabrics.

Regenerated silk fiber

RSF is produced by chemically dissolving silkworm cocoons, leaving their molecular structure intact. The silk fibers dissolve into tiny thread-like structures known as microfibrils. The resulting solution is extruded through a small opening, causing the microfibrils to reassemble into a single fiber. The resulting material is reportedly twice as stiff as silk. [69]

Clothing

Silk's absorbency makes it comfortable to wear in warm weather and while active. Its low conductivity keeps warm air close to the skin during cold weather. It is often used for clothing such as shirts, ties, blouses, formal dresses, high fashion clothes, lining, lingerie, pajamas, robes, dress suits, sun dresses and Eastern folk costumes. For practical use, silk is excellent as clothing that protects from many biting insects that would ordinarily pierce clothing, such as mosquitoes and horseflies.

Fabrics that are often made from silk include charmeuse, habutai, chiffon, taffeta, crepe de chine, dupioni, noil, tussah, and shantung, among others.

Furniture

Silk's attractive lustre and drape makes it suitable for many furnishing applications. It is used for upholstery, wall coverings, window treatments (if blended with another fiber), rugs, bedding and wall hangings. [70]

Industry

Silk had many industrial and commercial uses, such as in parachutes, bicycle tires, comforter filling and artillery gunpowder bags. [71]

Medicine

A special manufacturing process removes the outer sericin coating of the silk, which makes it suitable as non-absorbable surgical sutures. This process has also recently led to the introduction of specialist silk underclothing, which has been used for skin conditions including eczema. [72] [73] New uses and manufacturing techniques have been found for silk for making everything from disposable cups to drug delivery systems and holograms. [74]

Biomaterial

Silk began to serve as a biomedical material for sutures in surgeries as early as the second century CE. [75] In the past 30 years, it has been widely studied and used as a biomaterial due to its mechanical strength, biocompatibility, tunable degradation rate, ease to load cellular growth factors (for example, BMP-2), and its ability to be processed into several other formats such as films, gels, particles, and scaffolds. [76] Silks from Bombyx mori, a kind of cultivated silkworm, are the most widely investigated silks. [77]

Silks derived from Bombyx mori are generally made of two parts: the silk fibroin fiber which contains a light chain of 25kDa and a heavy chain of 350kDa (or 390kDa [78] ) linked by a single disulfide bond [79] and a glue-like protein, sericin, comprising 25 to 30 percentage by weight. Silk fibroin contains hydrophobic beta sheet blocks, interrupted by small hydrophilic groups. And the beta-sheets contribute much to the high mechanical strength of silk fibers, which achieves 740 MPa, tens of times that of poly(lactic acid) and hundreds of times that of collagen. This impressive mechanical strength has made silk fibroin very competitive for applications in biomaterials. Indeed, silk fibers have found their way into tendon tissue engineering, [80] where mechanical properties matter greatly. In addition, mechanical properties of silks from various kinds of silkworms vary widely, which provides more choices for their use in tissue engineering.

Most products fabricated from regenerated silk are weak and brittle, with only ≈1–2% of the mechanical strength of native silk fibers due to the absence of appropriate secondary and hierarchical structure,

Biocompatibility

Biocompatibility, i.e., to what level the silk will cause an immune response, is a critical issue for biomaterials. The issue arose during its increasing clinical use. Wax or silicone is usually used as a coating to avoid fraying and potential immune responses [76] when silk fibers serve as suture materials. Although the lack of detailed characterization of silk fibers, such as the extent of the removal of sericin, the surface chemical properties of coating material, and the process used, make it difficult to determine the real immune response of silk fibers in literature, it is generally believed that sericin is the major cause of immune response. Thus, the removal of sericin is an essential step to assure biocompatibility in biomaterial applications of silk. However, further research fails to prove clearly the contribution of sericin to inflammatory responses based on isolated sericin and sericin based biomaterials. [82] In addition, silk fibroin exhibits an inflammatory response similar to that of tissue culture plastic in vitro [83] [84] when assessed with human mesenchymal stem cells (hMSCs) or lower than collagen and PLA when implant rat MSCs with silk fibroin films in vivo. [84] Thus, appropriate degumming and sterilization will assure the biocompatibility of silk fibroin, which is further validated by in vivo experiments on rats and pigs. [85] There are still concerns about the long-term safety of silk-based biomaterials in the human body in contrast to these promising results. Even though silk sutures serve well, they exist and interact within a limited period depending on the recovery of wounds (several weeks), much shorter than that in tissue engineering. Another concern arises from biodegradation because the biocompatibility of silk fibroin does not necessarily assure the biocompatibility of the decomposed products. In fact, different levels of immune responses [86] [87] and diseases [88] have been triggered by the degraded products of silk fibroin.

Biodegradability

Biodegradability (also known as biodegradation)—the ability to be disintegrated by biological approaches, including bacteria, fungi, and cells—is another significant property of biomaterials today. Biodegradable materials can minimize the pain of patients from surgeries, especially in tissue engineering, there is no need of surgery in order to remove the scaffold implanted. Wang et al. [89] showed the in vivo degradation of silk via aqueous 3-D scaffolds implanted into Lewis rats. Enzymes are the means used to achieve degradation of silk in vitro. Protease XIV from Streptomyces griseus and α-chymotrypsin from bovine pancreases are the two popular enzymes for silk degradation. In addition, gamma-radiation, as well as cell metabolism, can also regulate the degradation of silk.

Compared with synthetic biomaterials such as polyglycolides and polylactides, silk is obviously advantageous in some aspects in biodegradation. The acidic degraded products of polyglycolides and polylactides will decrease the pH of the ambient environment and thus adversely influence the metabolism of cells, which is not an issue for silk. In addition, silk materials can retain strength over a desired period from weeks to months as needed by mediating the content of beta sheets.

Genetic modification

Genetic modification of domesticated silkworms has been used to alter the composition of the silk. [90] As well as possibly facilitating the production of more useful types of silk, this may allow other industrially or therapeutically useful proteins to be made by silkworms. [91]


The Science of Silk

The sericulturists wait till the cocoon is complete and then collect them in thousands to boil them or steam them to extract the filament unruptured. The filament is then spun with others to make silk thread which is then ready for the loom. The cultivated silk is far better due to the continuous filament and also yields better to the dyeing process. The process of collecting and grading the cocoons prior to boiling them happens in a filature.

The silk filament is made of strong central protein called fibroin that is surrounded by a gummy sericin that hardens as soon as it is in contact with air.

During the initial stages the soaking of the cocoon helps to lose some of the sticky sericin but most of is it retained to help with the process of reeling, throwing and forming skeins of silk thread. Throughout the process the sericin is gradually removed by soaking in warm soapy water at various stages to deliver a superior, distinctive, shiny fabric.

The fibre has very high tensile strength due to the tight packing of the amino acids in the protein fibroin. The fabric itself has tight bonds and is resistant to many acids but does go weaker when wet.

The specially bred silk worm Bombyx Mori produces filaments that have a triangular cross section with flat sides. This gives the fibre a prismatic ability to reflect light.


Thai Silk

In 2012, there were about 94,000 mulberry farmers. This was an increase from the 80,000 farmers in 2011. Some 20 years ago, the number of farmers used to be much higher, but many farmers have since switched to the industrial sector or started growing alternative crops. Thailand produces about 600 tonnes of silk each year, 500 of which are used locally. Thailand isn’t the only country making silk, however. It competes with some of its Asian neighbors, including Vietnam and China.


Thai Silk From The Khorat Plateau Of Thailand

Thai silk is created from the Thai silkworms’ cocoons. Thai weavers primarily from the Khorat Plateau in Thailand’s northeast region nurture the caterpillars on a steady diet, feeding them mulberry leaves alone. Khorat is the heart of the silk industry in Thailand and a regular supplier of rose silk for several generations now.

At present, this silk is deemed as one of the most excellent and finest fabrics in the world. It is an output of a distinct manufacturing procedure, presenting distinct colors and patterns.

History
After silk was produced in ancient China as well as India where the silk weaving practice began around 2,640 BCE, most merchants widen the use of silk to several different regions throughout Asia via trading. Some accounts connote that archaeologists came across with the first silk fibers in Thailand of more than 3,000 years old in the Baan Chiang ruins. This site is acknowledged by many people as the Southeast Asia’s oldest civilization.

Weaving
The creation of silk starts with the Bombyx mori, which is a small worm generated from the eggs of a silk moth. During the first year, the worms feed on leaves of mulberry trees prior to building a cocoon with the use of their spittle.

In its unique cocoon form, raw silk is irregular and bumpy. Thus, Thai weavers break up the completed cocoons coming from the mulberry bush and bathe them in a vat of boiling water to divide the silk thread from the caterpillar from the interior of the cocoon.

The Bombyx mori normally creates silk thread of different colors, ranging from gold, light gold, and to very light green, with lengths from 500 to 1,500 yards every cocoon.

Because a single Thai silk thread filament is very thin to utilize on its own, Thai women mix several thread to build a thicker and usable fiber. This process is carried out by hand-reeling the threads placed in a wooden spindle to produce a standard strand of raw silk. It is a tiresome procedure since it takes about 40 hours to manufacture even half kilogram of silk.

Most of the local operations employ a reeling machine, though majority stick with hand-reeling. The main distinction is that hand-reeled silk produces three silk grades: a thick grade that complements heavier material and two fine grades that suit lightweight fabrics.

The silk is then immersed in hot water and then bleached. Dyeing is also done to eliminate the natural yellow coloring of Thai yarn. To perform this step, skeins of silk thread are soaked in huge tubs of hydrogen peroxide. After washing and drying, the silk is then woven through the conventional hand operated loom.

Colorful Thai silk fabric

Distinction
To determine a genuine silk, Thailand’s Agriculture Ministry makes use of a peacock emblem to validate and authenticate their products and protect them from imitations. The colors include:

– Gold Peacock
– Silver Peacock
– Blue Peacock
– Green Peacock

Because this silk is hand woven, every silk bag and fabric is distinct and can’t be copied through commercial approaches. It also furnishes a unique luster, with a gleam that has two distinctive combinations: one color for the weft and another for the warp. In addition the Thai silk fabric changes its color at different angles when positioned against the light.
NANGFA Manufacturing Co., Ltd. is providing silk textile bags and home decor since 2006.

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Contents

The word silk comes from Old English: sioloc, from Ancient Greek: σηρικός , romanized: sērikós, "silken", ultimately from the Chinese word "sī" and other Asian sources—compare Mandarin "silk", Manchurian sirghe, Mongolian sirkek. [4]

The production of silk originated in China in the Neolithic period although, it would eventually reach other places of the world ( Yangshao culture, 4th millennium BC). Silk production remained confined to China until the Silk Road opened at some point during the latter part of the 1st millennium BC, though China maintained its virtual monopoly over silk production for another thousand years.

Wild silk

Several kinds of wild silk, produced by caterpillars other than the mulberry silkworm, have been known and spun in China, South Asia, and Europe since ancient times, e.g. the production of Eri silk in Assam, India. However, the scale of production was always far smaller than for cultivated silks. There are several reasons for this: first, they differ from the domesticated varieties in colour and texture and are therefore less uniform second, cocoons gathered in the wild have usually had the pupa emerge from them before being discovered so the silk thread that makes up the cocoon has been torn into shorter lengths and third, many wild cocoons are covered in a mineral layer that prevents attempts to reel from them long strands of silk. [5] Thus, the only way to obtain silk suitable for spinning into textiles in areas where commercial silks are not cultivated was by tedious and labor-intensive carding.

Some natural silk structures have been used without being unwound or spun. Spider webs were used as a wound dressing in ancient Greece and Rome, [6] and as a base for painting from the 16th century. [7] Caterpillar nests were pasted together to make a fabric in the Aztec Empire. [8]

Commercial silks originate from reared silkworm pupae, which are bred to produce a white-colored silk thread with no mineral on the surface. The pupae are killed by either dipping them in boiling water before the adult moths emerge or by piercing them with a needle. These factors all contribute to the ability of the whole cocoon to be unravelled as one continuous thread, permitting a much stronger cloth to be woven from the silk. Wild silks also tend to be more difficult to dye than silk from the cultivated silkworm. [9] [10] A technique known as demineralizing allows the mineral layer around the cocoon of wild silk moths to be removed, [11] leaving only variability in color as a barrier to creating a commercial silk industry based on wild silks in the parts of the world where wild silk moths thrive, such as in Africa and South America.

China

Silk use in fabric was first developed in ancient China. [12] [13] The earliest evidence for silk is the presence of the silk protein fibroin in soil samples from two tombs at the neolithic site Jiahu in Henan, which date back about 8,500 years. [14] [15] The earliest surviving example of silk fabric dates from about 3630 BC, and was used as the wrapping for the body of a child at a Yangshao culture site in Qingtaicun near Xingyang, Henan. [12] [16]

Legend gives credit for developing silk to a Chinese empress, Leizu (Hsi-Ling-Shih, Lei-Tzu). Silks were originally reserved for the Emperors of China for their own use and gifts to others, but spread gradually through Chinese culture and trade both geographically and socially, and then to many regions of Asia. Because of its texture and lustre, silk rapidly became a popular luxury fabric in the many areas accessible to Chinese merchants. Silk was in great demand, and became a staple of pre-industrial international trade. Silk was also used as a surface for writing, especially during the Warring States period (475-221 BCE). The fabric was light, it survived the damp climate of the Yangtze region, absorbed ink well, and provided a white background for the text. [17] In July 2007, archaeologists discovered intricately woven and dyed silk textiles in a tomb in Jiangxi province, dated to the Eastern Zhou dynasty roughly 2,500 years ago. [18] Although historians have suspected a long history of a formative textile industry in ancient China, this find of silk textiles employing "complicated techniques" of weaving and dyeing provides direct evidence for silks dating before the Mawangdui-discovery and other silks dating to the Han dynasty (202 BC – 220 AD). [18]

Silk is described in a chapter of the Fan Shengzhi shu from the Western Han (202 BC – 9 AD). There is a surviving calendar for silk production in an Eastern Han (25–220 AD) document. The two other known works on silk from the Han period are lost. [12] The first evidence of the long distance silk trade is the finding of silk in the hair of an Egyptian mummy of the 21st dynasty, c.1070 BC. [19] The silk trade reached as far as the Indian subcontinent, the Middle East, Europe, and North Africa. This trade was so extensive that the major set of trade routes between Europe and Asia came to be known as the Silk Road.

The Emperors of China strove to keep knowledge of sericulture secret to maintain the Chinese monopoly. Nonetheless sericulture reached Korea with technological aid from China around 200 BC, [20] the ancient Kingdom of Khotan by AD 50, [21] and India by AD 140. [22]

In the ancient era, silk from China was the most lucrative and sought-after luxury item traded across the Eurasian continent, [23] and many civilizations, such as the ancient Persians, benefited economically from trade. [23]

The silkworms and mulberry leaves are placed on trays.

Twig frames for the silkworms are prepared.

The cocoons are soaked and the silk is wound on spools.

The silk is woven using a loom.

Northeastern India

In the northeastern state of Assam, three different types of indigenous variety of silk are produced, collectively called Assam silk: Muga, Eri and Pat silk. Muga, the golden silk, and Eri are produced by silkworms that are native only to Assam. They have been reared since ancient times similar to other East and South-East Asian countries.

India

Silk has a long history in India. It is known as Resham in eastern and north India, and Pattu in southern parts of India. Recent archaeological discoveries in Harappa and Chanhu-daro suggest that sericulture, employing wild silk threads from native silkworm species, existed in South Asia during the time of the Indus Valley Civilization (now in Pakistan and India) dating between 2450 BC and 2000 BC, while "hard and fast evidence" for silk production in China dates back to around 2570 BC. [24] [25] Shelagh Vainker, a silk expert at the Ashmolean Museum in Oxford, who sees evidence for silk production in China "significantly earlier" than 2500–2000 BC, suggests, "people of the Indus civilization either harvested silkworm cocoons or traded with people who did, and that they knew a considerable amount about silk." [24]

India is the second largest producer of silk in the world after China. About 97% of the raw mulberry silk comes from six Indian states, namely, Andhra Pradesh, Karnataka, Jammu and Kashmir, Tamil Nadu, Bihar and West Bengal. [26] North Bangalore, the upcoming site of a $20 million "Silk City" Ramanagara and Mysore, contribute to a majority of silk production in Karnataka. [27]

In Tamil Nadu, mulberry cultivation is concentrated in the Coimbatore, Erode, Bhagalpuri, Tiruppur, Salem and Dharmapuri districts. Hyderabad, Andhra Pradesh, and Gobichettipalayam, Tamil Nadu, were the first locations to have automated silk reeling units in India. [28]

Thailand

Silk is produced year-round in Thailand by two types of silkworms, the cultured Bombycidae and wild Saturniidae. Most production is after the rice harvest in the southern and northeastern parts of the country. Women traditionally weave silk on hand looms and pass the skill on to their daughters, as weaving is considered to be a sign of maturity and eligibility for marriage. Thai silk textiles often use complicated patterns in various colours and styles. Most regions of Thailand have their own typical silks. A single thread filament is too thin to use on its own so women combine many threads to produce a thicker, usable fiber. They do this by hand-reeling the threads onto a wooden spindle to produce a uniform strand of raw silk. The process takes around 40 hours to produce a half kilogram of silk. Many local operations use a reeling machine for this task, but some silk threads are still hand-reeled. The difference is that hand-reeled threads produce three grades of silk: two fine grades that are ideal for lightweight fabrics, and a thick grade for heavier material.

The silk fabric is soaked in extremely cold water and bleached before dyeing to remove the natural yellow coloring of Thai silk yarn. To do this, skeins of silk thread are immersed in large tubs of hydrogen peroxide. Once washed and dried, the silk is woven on a traditional hand-operated loom. [29]

Bangladesh

The Rajshahi Division of northern Bangladesh is the hub of the country's silk industry. There are three types of silk produced in the region: mulberry, endi and tassar. Bengali silk was a major item of international trade for centuries. It was known as Ganges silk in medieval Europe. Bengal was the leading exporter of silk between the 16th and 19th centuries. [30]

Central Asia

The 7th century CE murals of Afrasiyab in Samarkand, Sogdiana, show a Chinese Embassy carrying silk and a string of silkworm cocoons to the local Sogdian ruler. [31]

Middle East

In the Torah, a scarlet cloth item called in Hebrew "sheni tola'at" שני תולעת – literally "crimson of the worm" – is described as being used in purification ceremonies, such as those following a leprosy outbreak (Leviticus 14), alongside cedar wood and hyssop (za'atar). Eminent scholar and leading medieval translator of Jewish sources and books of the Bible into Arabic, Rabbi Saadia Gaon, translates this phrase explicitly as "crimson silk" – חריר קרמז حرير قرمز.

In Islamic teachings, Muslim men are forbidden to wear silk. Many religious jurists believe the reasoning behind the prohibition lies in avoiding clothing for men that can be considered feminine or extravagant. [32] There are disputes regarding the amount of silk a fabric can consist of (e.g., whether a small decorative silk piece on a cotton caftan is permissible or not) for it to be lawful for men to wear, but the dominant opinion of most Muslim scholars is that the wearing of silk by men is forbidden. Modern attire has raised a number of issues, including, for instance, the permissibility of wearing silk neckties, which are masculine articles of clothing.

Ancient Mediterranean

In the Odyssey, 19.233, when Odysseus, while pretending to be someone else, is questioned by Penelope about her husband's clothing, he says that he wore a shirt "gleaming like the skin of a dried onion" (varies with translations, literal translation here) [33] which could refer to the lustrous quality of silk fabric. Aristotle wrote of Coa vestis, a wild silk textile from Kos. Sea silk from certain large sea shells was also valued. The Roman Empire knew of and traded in silk, and Chinese silk was the most highly priced luxury good imported by them. [23] During the reign of emperor Tiberius, sumptuary laws were passed that forbade men from wearing silk garments, but these proved ineffectual. [34] The Historia Augusta mentions that the third-century emperor Elagabalus was the first Roman to wear garments of pure silk, whereas it had been customary to wear fabrics of silk/cotton or silk/linen blends. [35] Despite the popularity of silk, the secret of silk-making only reached Europe around AD 550, via the Byzantine Empire. Contemporary accounts state that monks working for the emperor Justinian I smuggled silkworm eggs to Constantinople in hollow canes from China. [36] All top-quality looms and weavers were located inside the Great Palace complex in Constantinople, and the cloth produced was used in imperial robes or in diplomacy, as gifts to foreign dignitaries. The remainder was sold at very high prices.

Medieval and modern Europe

Italy was the most important producer of silk during the Medieval age. The first center to introduce silk production to Italy was the city of Catanzaro during the 11th century in the region of Calabria. The silk of Catanzaro supplied almost all of Europe and was sold in a large market fair in the port of Reggio Calabria, to Spanish, Venetian, Genovese and Dutch merchants. Catanzaro became the lace capital of the world with a large silkworm breeding facility that produced all the laces and linens used in the Vatican. The city was world-famous for its fine fabrication of silks, velvets, damasks and brocades. [37]

Another notable center was the Italian city-state of Lucca which largely financed itself through silk-production and silk-trading, beginning in the 12th century. Other Italian cities involved in silk production were Genoa, Venice and Florence.

The Silk Exchange in Valencia from the 15th century—where previously in 1348 also perxal (percale) was traded as some kind of silk—illustrates the power and wealth of one of the great Mediterranean mercantile cities. [38] [39]

Silk was produced in and exported from the province of Granada, Spain, especially the Alpujarras region, until the Moriscos, whose industry it was, were expelled from Granada in 1571. [40] [41]

Since the 15th century, silk production in France has been centered around the city of Lyon where many mechanic tools for mass production were first introduced in the 17th century.

James I attempted to establish silk production in England, purchasing and planting 100,000 mulberry trees, some on land adjacent to Hampton Court Palace, but they were of a species unsuited to the silk worms, and the attempt failed. In 1732 John Guardivaglio set up a silk throwing enterprise at Logwood mill in Stockport in 1744, Burton Mill was erected in Macclesfield and in 1753 Old Mill was built in Congleton. [42] These three towns remained the centre of the English silk throwing industry until silk throwing was replaced by silk waste spinning. British enterprise also established silk filature in Cyprus in 1928. In England in the mid-20th century, raw silk was produced at Lullingstone Castle in Kent. Silkworms were raised and reeled under the direction of Zoe Lady Hart Dyke, later moving to Ayot St Lawrence in Hertfordshire in 1956. [43]

During World War II, supplies of silk for UK parachute manufacture were secured from the Middle East by Peter Gaddum. [44]

A hundred-year-old pattern of silk called "Almgrensrosen"

The necktie originates from the cravat, a neckband made from silk [45] [46] [47]

North America

Wild silk taken from the nests of native caterpillars was used by the Aztecs to make containers and as paper. [48] [8] Silkworms were introduced to Oaxaca from Spain in the 1530s and the region profited from silk production until the early 17th century, when the king of Spain banned export to protect Spain's silk industry. Silk production for local consumption has continued until the present day, sometimes spinning wild silk. [49]

King James I introduced silk-growing to the British colonies in America around 1619, ostensibly to discourage tobacco planting. The Shakers in Kentucky adopted the practice.

The history of industrial silk in the United States is largely tied to several smaller urban centers in the Northeast region. Beginning in the 1830s, Manchester, Connecticut emerged as the early center of the silk industry in America, when the Cheney Brothers became the first in the United States to properly raise silkworms on an industrial scale today the Cheney Brothers Historic District showcases their former mills. [51] With the mulberry tree craze of that decade, other smaller producers began raising silkworms. This economy particularly gained traction in the vicinity of Northampton, Massachusetts and its neighboring Williamsburg, where a number of small firms and cooperatives emerged. Among the most prominent of these was the cooperative utopian Northampton Association for Education and Industry, of which Sojourner Truth was a member. [52] Following the destructive Mill River Flood of 1874, one manufacturer, William Skinner, relocated his mill from Williamsburg to the then-new city of Holyoke. Over the next 50 years he and his sons would maintain relations between the American silk industry and its counterparts in Japan, [53] and expanded their business to the point that by 1911, the Skinner Mill complex contained the largest silk mill under one roof in the world, and the brand Skinner Fabrics had become the largest manufacturer of silk satins internationally. [50] [54] Other efforts later in the 19th century would also bring the new silk industry to Paterson, New Jersey, with several firms hiring European-born textile workers and granting it the nickname "Silk City" as another major center of production in the United States.

World War II interrupted the silk trade from Asia, and silk prices increased dramatically. [55] U.S. industry began to look for substitutes, which led to the use of synthetics such as nylon. Synthetic silks have also been made from lyocell, a type of cellulose fiber, and are often difficult to distinguish from real silk (see spider silk for more on synthetic silks).

Malaysia

In Terengganu, which is now part of Malaysia, a second generation of silkworm was being imported as early as 1764 for the country's silk textile industry, especially songket. [56] However, since the 1980s, Malaysia is no longer engaged in sericulture but does plant mulberry trees.

Vietnam

In Vietnamese legend, silk appeared in the first millennium AD and is still being woven today.

The process of silk production is known as sericulture. [57] The entire production process of silk can be divided into several steps which are typically handled by different entities. [ clarification needed ] Extracting raw silk starts by cultivating the silkworms on mulberry leaves. Once the worms start pupating in their cocoons, these are dissolved in boiling water in order for individual long fibres to be extracted and fed into the spinning reel. [58]

To produce 1 kg of silk, 104 kg of mulberry leaves must be eaten by 3000 silkworms. It takes about 5000 silkworms to make a pure silk kimono. [59] : 104 The major silk producers are China (54%) and India (14%). [60] Other statistics: [61]

The environmental impact of silk production is potentially large when compared with other natural fibers. A life-cycle assessment of Indian silk production shows that the production process has a large carbon and water footprint, mainly due to the fact that it is an animal-derived fiber and more inputs such as fertilizer and water are needed per unit of fiber produced. [62]

Physical properties

Silk fibers from the Bombyx mori silkworm have a triangular cross section with rounded corners, 5–10 μm wide. The fibroin-heavy chain is composed mostly of beta-sheets, due to a 59-mer amino acid repeat sequence with some variations. [63] The flat surfaces of the fibrils reflect light at many angles, giving silk a natural sheen. The cross-section from other silkworms can vary in shape and diameter: crescent-like for Anaphe and elongated wedge for tussah. Silkworm fibers are naturally extruded from two silkworm glands as a pair of primary filaments (brin), which are stuck together, with sericin proteins that act like glue, to form a bave. Bave diameters for tussah silk can reach 65 μm. See cited reference for cross-sectional SEM photographs. [64]

Silk has a smooth, soft texture that is not slippery, unlike many synthetic fibers.

Silk is one of the strongest natural fibers, but it loses up to 20% of its strength when wet. It has a good moisture regain of 11%. Its elasticity is moderate to poor: if elongated even a small amount, it remains stretched. It can be weakened if exposed to too much sunlight. It may also be attacked by insects, especially if left dirty.

One example of the durable nature of silk over other fabrics is demonstrated by the recovery in 1840 of silk garments from a wreck of 1782: 'The most durable article found has been silk for besides pieces of cloaks and lace, a pair of black satin breeches, and a large satin waistcoat with flaps, were got up, of which the silk was perfect, but the lining entirely gone . from the thread giving way . No articles of dress of woollen cloth have yet been found.' [65]

Silk is a poor conductor of electricity and thus susceptible to static cling. Silk has a high emissivity for infrared light, making it feel cool to the touch. [66]

Unwashed silk chiffon may shrink up to 8% due to a relaxation of the fiber macrostructure, so silk should either be washed prior to garment construction, or dry cleaned. Dry cleaning may still shrink the chiffon up to 4%. Occasionally, this shrinkage can be reversed by a gentle steaming with a press cloth. There is almost no gradual shrinkage nor shrinkage due to molecular-level deformation.

Natural and synthetic silk is known to manifest piezoelectric properties in proteins, probably due to its molecular structure. [67]

Silkworm silk was used as the standard for the denier, a measurement of linear density in fibers. Silkworm silk therefore has a linear density of approximately 1 den, or 1.1 dtex.

Comparison of silk fibers [68] Linear density (dtex) Diameter (μm) Coeff. variation
Moth: Bombyx mori 1.17 12.9 24.8%
Spider: Argiope aurantia 0.14 3.57 14.8%

Chemical properties

Silk emitted by the silkworm consists of two main proteins, sericin and fibroin, fibroin being the structural center of the silk, and serecin being the sticky material surrounding it. Fibroin is made up of the amino acids Gly-Ser-Gly-Ala-Gly-Ala and forms beta pleated sheets. Hydrogen bonds form between chains, and side chains form above and below the plane of the hydrogen bond network.

The high proportion (50%) of glycine allows tight packing. This is because glycine's R group is only a hydrogen and so is not as sterically constrained. The addition of alanine and serine makes the fibres strong and resistant to breaking. This tensile strength is due to the many interceded hydrogen bonds, and when stretched the force is applied to these numerous bonds and they do not break.

Silk is resistant to most mineral acids, except for sulfuric acid, which dissolves it. It is yellowed by perspiration. Chlorine bleach will also destroy silk fabrics.

Regenerated silk fiber

RSF is produced by chemically dissolving silkworm cocoons, leaving their molecular structure intact. The silk fibers dissolve into tiny thread-like structures known as microfibrils. The resulting solution is extruded through a small opening, causing the microfibrils to reassemble into a single fiber. The resulting material is reportedly twice as stiff as silk. [69]

Clothing

Silk's absorbency makes it comfortable to wear in warm weather and while active. Its low conductivity keeps warm air close to the skin during cold weather. It is often used for clothing such as shirts, ties, blouses, formal dresses, high fashion clothes, lining, lingerie, pajamas, robes, dress suits, sun dresses and Eastern folk costumes. For practical use, silk is excellent as clothing that protects from many biting insects that would ordinarily pierce clothing, such as mosquitoes and horseflies.

Fabrics that are often made from silk include charmeuse, habutai, chiffon, taffeta, crepe de chine, dupioni, noil, tussah, and shantung, among others.

Furniture

Silk's attractive lustre and drape makes it suitable for many furnishing applications. It is used for upholstery, wall coverings, window treatments (if blended with another fiber), rugs, bedding and wall hangings. [70]

Industry

Silk had many industrial and commercial uses, such as in parachutes, bicycle tires, comforter filling and artillery gunpowder bags. [71]

Medicine

A special manufacturing process removes the outer sericin coating of the silk, which makes it suitable as non-absorbable surgical sutures. This process has also recently led to the introduction of specialist silk underclothing, which has been used for skin conditions including eczema. [72] [73] New uses and manufacturing techniques have been found for silk for making everything from disposable cups to drug delivery systems and holograms. [74]

Biomaterial

Silk began to serve as a biomedical material for sutures in surgeries as early as the second century CE. [75] In the past 30 years, it has been widely studied and used as a biomaterial due to its mechanical strength, biocompatibility, tunable degradation rate, ease to load cellular growth factors (for example, BMP-2), and its ability to be processed into several other formats such as films, gels, particles, and scaffolds. [76] Silks from Bombyx mori, a kind of cultivated silkworm, are the most widely investigated silks. [77]

Silks derived from Bombyx mori are generally made of two parts: the silk fibroin fiber which contains a light chain of 25kDa and a heavy chain of 350kDa (or 390kDa [78] ) linked by a single disulfide bond [79] and a glue-like protein, sericin, comprising 25 to 30 percentage by weight. Silk fibroin contains hydrophobic beta sheet blocks, interrupted by small hydrophilic groups. And the beta-sheets contribute much to the high mechanical strength of silk fibers, which achieves 740 MPa, tens of times that of poly(lactic acid) and hundreds of times that of collagen. This impressive mechanical strength has made silk fibroin very competitive for applications in biomaterials. Indeed, silk fibers have found their way into tendon tissue engineering, [80] where mechanical properties matter greatly. In addition, mechanical properties of silks from various kinds of silkworms vary widely, which provides more choices for their use in tissue engineering.

Most products fabricated from regenerated silk are weak and brittle, with only ≈1–2% of the mechanical strength of native silk fibers due to the absence of appropriate secondary and hierarchical structure,

Biocompatibility

Biocompatibility, i.e., to what level the silk will cause an immune response, is a critical issue for biomaterials. The issue arose during its increasing clinical use. Wax or silicone is usually used as a coating to avoid fraying and potential immune responses [76] when silk fibers serve as suture materials. Although the lack of detailed characterization of silk fibers, such as the extent of the removal of sericin, the surface chemical properties of coating material, and the process used, make it difficult to determine the real immune response of silk fibers in literature, it is generally believed that sericin is the major cause of immune response. Thus, the removal of sericin is an essential step to assure biocompatibility in biomaterial applications of silk. However, further research fails to prove clearly the contribution of sericin to inflammatory responses based on isolated sericin and sericin based biomaterials. [82] In addition, silk fibroin exhibits an inflammatory response similar to that of tissue culture plastic in vitro [83] [84] when assessed with human mesenchymal stem cells (hMSCs) or lower than collagen and PLA when implant rat MSCs with silk fibroin films in vivo. [84] Thus, appropriate degumming and sterilization will assure the biocompatibility of silk fibroin, which is further validated by in vivo experiments on rats and pigs. [85] There are still concerns about the long-term safety of silk-based biomaterials in the human body in contrast to these promising results. Even though silk sutures serve well, they exist and interact within a limited period depending on the recovery of wounds (several weeks), much shorter than that in tissue engineering. Another concern arises from biodegradation because the biocompatibility of silk fibroin does not necessarily assure the biocompatibility of the decomposed products. In fact, different levels of immune responses [86] [87] and diseases [88] have been triggered by the degraded products of silk fibroin.

Biodegradability

Biodegradability (also known as biodegradation)—the ability to be disintegrated by biological approaches, including bacteria, fungi, and cells—is another significant property of biomaterials today. Biodegradable materials can minimize the pain of patients from surgeries, especially in tissue engineering, there is no need of surgery in order to remove the scaffold implanted. Wang et al. [89] showed the in vivo degradation of silk via aqueous 3-D scaffolds implanted into Lewis rats. Enzymes are the means used to achieve degradation of silk in vitro. Protease XIV from Streptomyces griseus and α-chymotrypsin from bovine pancreases are the two popular enzymes for silk degradation. In addition, gamma-radiation, as well as cell metabolism, can also regulate the degradation of silk.

Compared with synthetic biomaterials such as polyglycolides and polylactides, silk is obviously advantageous in some aspects in biodegradation. The acidic degraded products of polyglycolides and polylactides will decrease the pH of the ambient environment and thus adversely influence the metabolism of cells, which is not an issue for silk. In addition, silk materials can retain strength over a desired period from weeks to months as needed by mediating the content of beta sheets.

Genetic modification

Genetic modification of domesticated silkworms has been used to alter the composition of the silk. [90] As well as possibly facilitating the production of more useful types of silk, this may allow other industrially or therapeutically useful proteins to be made by silkworms. [91]


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