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Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the cocoons of the larvae of the
mulberry silkworm The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically im ...
'' Bombyx mori'' reared in captivity ( sericulture). The shimmering appearance of silk is due to the triangular prism-like structure of the silk fibre, which allows silk cloth to refract incoming light at different angles, thus producing different colors. Silk is produced by several insects; but, generally, only the silk of moth caterpillars has been used for textile manufacturing. There has been some research into other types of silk, which differ at the molecular level. Silk is mainly produced by the larvae of insects undergoing complete metamorphosis, but some insects, such as webspinners and raspy crickets, produce silk throughout their lives. Silk production also occurs in
hymenoptera Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...
(
bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...
s, wasps, and ants),
silverfish The silverfish (''Lepisma saccharinum'') is a species of small, primitive, wingless insect in the order Zygentoma (formerly Thysanura). Its common name derives from the insect's silvery light grey colour, combined with the fish-like appearance ...
, mayflies, thrips,
leafhopper A leafhopper is the common name for any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees. Their hind legs are modified for jumping, and a ...
s, beetles,
lacewing The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera can be grouped together with the Megaloptera and Raphidioptera in t ...
s, fleas, flies, and
midge A midge is any small fly, including species in several families of non-mosquito Nematoceran Diptera. Midges are found (seasonally or otherwise) on practically every land area outside permanently arid deserts and the frigid zones. Some mid ...
s. Other types of arthropods produce silk, most notably various arachnids, such as spiders.


Etymology

The word silk comes from ang, sioloc, from grc, σηρικός, translit=sērikós, "silken", ultimately from the Chinese word "sī" and other Asian sources—compare
Mandarin Mandarin or The Mandarin may refer to: Language * Mandarin Chinese, branch of Chinese originally spoken in northern parts of the country ** Standard Chinese or Modern Standard Mandarin, the official language of China ** Taiwanese Mandarin, Stand ...
"silk", Manchurian , Mongolian .


History

The production of silk originated in
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
in the Neolithic period, although it would eventually reach other places of the world ( culture, 4th millennium BC). Silk production remained confined to China until the
Silk Road The Silk Road () was a network of Eurasian trade routes active from the second century BCE until the mid-15th century. Spanning over 6,400 kilometers (4,000 miles), it played a central role in facilitating economic, cultural, political, and reli ...
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
caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...
s other than the
mulberry ''Morus'', a genus of flowering plants in the family Moraceae, consists of diverse species of deciduous trees commonly known as mulberries, growing wild and under cultivation in many temperate world regions. Generally, the genus has 64 identif ...
silkworm, have been known and spun in
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, 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. 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 Carding is a mechanical process that disentangles, cleans and intermixes fibres to produce a continuous web or sliver (textiles), sliver suitable for subsequent processing. This is achieved by passing the fibres between differentially moving su ...
. 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, and as a base for painting from the 16th century. Caterpillar nests were pasted together to make a fabric in the
Aztec Empire The Aztec Empire or the Triple Alliance ( nci, Ēxcān Tlahtōlōyān, Help:IPA/Nahuatl, jéːʃkaːn̥ t͡ɬaʔtoːˈlóːjaːn̥ was an alliance of three Nahua peoples, Nahua altepetl, city-states: , , and . These three city-states ruled ...
. 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. A technique known as demineralizing allows the mineral layer around the cocoon of wild silk moths to be removed, 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. The earliest evidence for silk is the presence of the silk protein fibroin in soil samples from two tombs at the neolithic site
Jiahu Jiahu () was the site of a Neolithic settlement based in the central plain of ancient China, near the Yellow River. It is located between the floodplains of the Ni River to the north, and the Sha River to the south, north of the modern city ...
in Henan, which date back about 8,500 years. 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. Legend gives credit for developing silk to a Chinese empress,
Leizu Leizu (), also known as Xi Ling-shi (, Wade–Giles Hsi Ling-shih), was a legendary Chinese empress and wife of the Yellow Emperor. According to tradition, she discovered sericulture, and invented the silk loom, in the 27th century BC. Myths A ...
(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. 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. 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 Mawangdui () is an archaeological site located in Changsha, China. The site consists of two saddle-shaped hills and contained the tombs of three people from the Changsha Kingdom during the western Han dynasty (206 BC – 9 AD): the Chancellor Li ...
-discovery and other silks dating to the Han dynasty (202 BC – 220 AD). 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. 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. 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 Silk Road () was a network of Eurasian trade routes active from the second century BCE until the mid-15th century. Spanning over 6,400 kilometers (4,000 miles), it played a central role in facilitating economic, cultural, political, and reli ...
. 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, the ancient Kingdom of Khotan by AD 50, and India by AD 140. In the ancient era, silk from China was the most lucrative and sought-after luxury item traded across the Eurasian continent, and many civilizations, such as the ancient Persians, benefited economically from trade. File:Women placing silkworms on trays together with mulberry leaves (Sericulture by Liang Kai, 1200s).jpg , The silkworms and mulberry leaves are placed on trays. File:Men preparing twig frames where silkworms will spin cocoons (Sericulture by Liang Kai, 1200s).jpg, Twig frames for the silkworms are prepared. File:Weighing and sorting the cocoons (Sericulture by Liang Kai, 1200s).jpg, The cocoons are weighed. File:Soaking the cocoons and reeling the silk (Sericulture by Liang Kai, 1200s).jpg, The cocoons are soaked and the silk is wound on spools. File:Weaving the silk (Sericulture by Liang Kai, 1200s).jpg, The silk is woven using a loom.


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 Harappa (; Urdu/ pnb, ) is an archaeological site in Punjab, Pakistan, about west of Sahiwal. The Bronze Age Harappan civilisation, now more often called the Indus Valley Civilisation, is named after the site, which takes its name from a mode ...
and
Chanhu-daro Chanhu-daro is an archaeological site belonging to the Indus Valley civilization. The site is located south of Mohenjo-daro, in Sindh, Pakistan. The settlement was inhabited between 4000 and 1700 BCE, and is considered to have been a cen ...
suggest that sericulture, employing wild silk threads from native
silkworm The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically imp ...
species, existed in South Asia during the time of the Indus Valley civilisation (now in Pakistan and India) dating between 2450 BC and 2000 BC. Shelagh Vainker, a silk expert at the
Ashmolean Museum The Ashmolean Museum of Art and Archaeology () on Beaumont Street, Oxford, England, is Britain's first public museum. Its first building was erected in 1678–1683 to house the cabinet of curiosities that Elias Ashmole gave to the University of ...
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." 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 Jammu and Kashmir may refer to: * Kashmir, the northernmost geographical region of the Indian subcontinent * Jammu and Kashmir (union territory), a region administered by India as a union territory * Jammu and Kashmir (state), a region administered ...
, Tamil Nadu, Bihar, and West Bengal. North Bangalore, the upcoming site of a $20 million "Silk City" Ramanagara and Mysore, contribute to a majority of silk production in Karnataka. In Tamil Nadu, mulberry cultivation is concentrated in the
Coimbatore Coimbatore, also spelt as Koyamputhur (), sometimes shortened as Kovai (), is one of the major metropolitan cities in the Indian state of Tamil Nadu. It is located on the banks of the Noyyal River and surrounded by the Western Ghats. Coimbato ...
, Erode, Bhagalpuri, Tiruppur,
Salem Salem may refer to: Places Canada Ontario * Bruce County ** Salem, Arran–Elderslie, Ontario, in the municipality of Arran–Elderslie ** Salem, South Bruce, Ontario, in the municipality of South Bruce * Salem, Dufferin County, Ontario, part ...
, and Dharmapuri districts. Hyderabad, Andhra Pradesh, and Gobichettipalayam, Tamil Nadu, were the first locations to have automated silk reeling units in India. In the northeastern state of Assam, three different types of indigenous variety of silk are produced, collectively called
Assam silk Assam silk denotes the three major types of indigenous wild silks produced in Assam—golden muga, white pat and warm eri silk. The Assam silk industry, now centered in Sualkuchi, is a labor-intensive industry. History Assam was well known fo ...
:
Muga silk Muga silk is a variety of wild silk geographically tagged to the state of Assam in India. The silk is known for its extreme durability and has a natural yellowish-golden tint with a shimmering, glossy texture. It was previously reserved for th ...
, Eri silk and
Pat silk Pat silk or White pat silk, Mulberry silk of Assam ( Assamese: পাট ৰেচম) is a variety of domestic silk in Assam, India. It is usually brilliant white or off-white in colour. Its cloth can dry in shadow. The larvae of the '' Pat S ...
. 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.


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 The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety of thread-like structures, including: Astronomy * Galaxy filament, the largest known cosmic structures in the universe * Solar 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.


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.


Central Asia

The 7th century CE murals of Afrasiyab in
Samarkand fa, سمرقند , native_name_lang = , settlement_type = City , image_skyline = , image_caption = Clockwise from the top:Registan square, Shah-i-Zinda necropolis, Bibi-Khanym Mosque, view inside Shah-i-Zinda, ...
, Sogdiana, show a Chinese Embassy carrying silk and a string of silkworm cocoons to the local Sogdian ruler.


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 Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God (or '' Allah'') as it was revealed to Muhammad, the mai ...
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. 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
necktie A necktie, or simply a tie, is a piece of cloth worn for decorative purposes around the neck, resting under the shirt collar and knotted at the throat, and often draped down the chest. Variants include the ascot, bow, bolo, zipper tie, cra ...
s, 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) which could refer to the lustrous quality of silk fabric. Aristotle wrote of ''
Coa vestis Coa vestis is an ancient type of fabric named after its point of origin, the Greek island Kos. ''Coa vestis'' was made by the wild silk of '' Pachypasa otus'', a Mediterranean moth.
'', 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. During the reign of emperor Tiberius,
sumptuary law Sumptuary laws (from Latin ''sūmptuāriae lēgēs'') are laws that try to regulate consumption. '' Black's Law Dictionary'' defines them as "Laws made for the purpose of restraining luxury or extravagance, particularly against inordinate expendi ...
s were passed that forbade men from wearing silk garments, but these proved ineffectual. The
Historia Augusta The ''Historia Augusta'' (English: ''Augustan History'') is a late Roman collection of biographies, written in Latin, of the Roman emperors, their junior colleagues, designated heirs and usurpers from 117 to 284. Supposedly modeled on the sim ...
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. 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 from China inside hollow canes. 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 , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = , demographics1_footnotes = , demographics1_title1 = , demographics1_info1 = , demographics1_title2 ...
. The silk of Catanzaro supplied almost all of Europe and was sold in a large market fair in the port of
Reggio Calabria Reggio di Calabria ( scn, label= Southern Calabrian, Riggiu; el, label= Calabrian Greek, Ρήγι, Rìji), usually referred to as Reggio Calabria, or simply Reggio by its inhabitants, is the largest city in Calabria. It has an estimated popul ...
, 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. 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 Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto Regions of Italy, region. It is built on a group of 118 small islands that are separated by canals and linked by over 400  ...
, and Florence. The Piedmont area of Northern Italy became a major silk producing area when water-powered silk throwing machines were developed. 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. Silk was produced in and exported from the province of
Granada Granada (,, DIN 31635, DIN: ; grc, Ἐλιβύργη, Elibýrgē; la, Illiberis or . ) is the capital city of the province of Granada, in the autonomous communities of Spain, autonomous community of Andalusia, Spain. Granada is located at the fo ...
, Spain, especially the Alpujarras region, until the Moriscos, whose industry it was, were expelled from Granada in 1571. 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 Hampton Court Palace is a Grade I listed royal palace in the London Borough of Richmond upon Thames, southwest and upstream of central London on the River Thames. The building of the palace began in 1514 for Cardinal Thomas Wolsey, the chie ...
, 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 Macclesfield is a market town and civil parish in the unitary authority of Cheshire East in Cheshire, England. It is located on the River Bollin in the east of the county, on the edge of the Cheshire Plain, with Macclesfield Forest to its east ...
; and in 1753 Old Mill was built in
Congleton Congleton is a town and civil parish in the unitary authority of Cheshire East in Cheshire, England. The town is by the River Dane, south of Manchester and north of Stoke on Trent. At the 2011 Census, it had a population of 26,482. Top ...
. 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. During World War II, supplies of silk for UK parachute manufacture were secured from the Middle East by
Peter Gaddum Peter William Gaddum (1902–1986) from Bowdon, Greater Manchester, in England was the sole provider of raw silk to the UK during much of World War II. Career After Japan entered the war in 1941, supplies from all usual sources (in China, Jap ...
. File:Vestido Javiera Carrera.jpg, Dress made from silk File:WLA vanda Bed lit a la polonaise.jpg, Bed covered with silk File:"Almgrensrosen"- ett 100 år gammalt mönster 2013.JPG, A hundred-year-old pattern of silk called "Almgrensrosen" File:Necktie knot.jpg, The
necktie A necktie, or simply a tie, is a piece of cloth worn for decorative purposes around the neck, resting under the shirt collar and knotted at the throat, and often draped down the chest. Variants include the ascot, bow, bolo, zipper tie, cra ...
originates from the cravat, a neckband made from silk


North America

Wild silk taken from the nests of native caterpillars was used by the
Aztecs The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different Indigenous peoples of Mexico, ethnic groups of central Mexico, particularly those g ...
to make containers and as paper. 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. King James I introduced silk-growing to the British colonies in America around 1619, ostensibly to discourage tobacco planting. The
Shakers The United Society of Believers in Christ's Second Appearing, more commonly known as the Shakers, are a Millenarianism, millenarian Restorationism, restorationist Christianity, Christian sect founded in England and then organized in the Unit ...
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. 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 The city of Northampton is the county seat of Hampshire County, Massachusetts, United States. As of the 2020 census, the population of Northampton (including its outer villages, Florence and Leeds) was 29,571. Northampton is known as an acade ...
and its neighboring
Williamsburg Williamsburg may refer to: Places *Colonial Williamsburg, a living-history museum and private foundation in Virginia *Williamsburg, Brooklyn, neighborhood in New York City *Williamsburg, former name of Kernville (former town), California *Williams ...
, 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 Sojourner Truth (; born Isabella Baumfree; November 26, 1883) was an American abolitionist of New York Dutch heritage and a women's rights activist. Truth was born into slavery in Swartekill, New York, but escaped with her infant daughter to f ...
was a member. Following the destructive Mill River Flood of 1874, one manufacturer, William Skinner, relocated his mill from Williamsburg to the then-new city of
Holyoke Holyoke is a city in Hampden County, Massachusetts, United States, that lies between the western bank of the Connecticut River and the Mount Tom Range. As of the 2020 census, the city had a population of 38,238. Located north of Springfield, ...
. Over the next 50 years he and his sons would maintain relations between the American silk industry and its counterparts in Japan, 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. Other efforts later in the 19th century would also bring the new silk industry to
Paterson, New Jersey Paterson ( ) is the largest City (New Jersey), city in and the county seat of Passaic County, New Jersey, Passaic County, in the U.S. state of New Jersey.World War II interrupted the silk trade from Asia, and silk prices increased dramatically. 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. 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.


Production process

The process of silk production is known as sericulture. The entire production process of silk can be divided into several steps which are typically handled by different entities. 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. 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. The major silk producers are
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
(54%) and India (14%). Other statistics: The environmental impact of silk production is potentially large when compared with other natural fibers. A
life-cycle assessment Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for assessing environmental impacts associated with all the stages of the Product lifecycle, life cycle of a commercial product, Process lifecycle, process, or ...
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.


Properties


Physical properties

Silk fibers from the ''Bombyx mori'' silkworm have a triangular cross section with rounded corners, 5–10
μm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...
wide. The fibroin-heavy chain is composed mostly of beta-sheets, due to a 59-mer amino acid repeat sequence with some variations. 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 Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
, to form a bave. Bave diameters for tussah silk can reach 65 μm. See cited reference for cross-sectional SEM photographs. Silk has a smooth, soft texture that is not slippery, unlike many
synthetic fiber Synthetic fibers or synthetic fibres (in British English; see spelling differences) are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants (like cotton) ...
s. 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 In chemistry, absorption is a physical or chemical phenomenon or a process in which atoms, molecules or ions enter some bulk phase – liquid or solid material. This is a different process from adsorption, since molecules undergoing absorption ...
of 11%. Its
elasticity Elasticity often refers to: *Elasticity (physics), continuum mechanics of bodies that deform reversibly under stress Elasticity may also refer to: Information technology * Elasticity (data store), the flexibility of the data model and the cl ...
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.' 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. Unwashed silk chiffon may
shrink Shrink may refer to: Common meanings *Miniaturization *Shrink, a slang term for: ** a psychiatrist ** a psychoanalyst ** a psychologist Arts, entertainment, and media * ''Shrink'' (album), album by German indie rock/electronica group The Notwist ...
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. 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 Textile fibers, threads, yarns and fabrics are measured in a multiplicity of units. * A fiber, a single filament of natural material, such as cotton, linen or wool, or artificial material such as nylon, polyester, metal or mineral fiber, or man-m ...
.


Chemical properties

Silk emitted by the silkworm consists of two main proteins, sericin and fibroin, fibroin being the structural center of the silk, and sericin being the sticky material surrounding it. Fibroin is made up of the amino acids Gly- Ser-Gly- Ala-Gly-Ala and forms
beta pleated sheet The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a gen ...
s.
Hydrogen bond In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a ...
s 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 resists most mineral acids, except for
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
, which dissolves it. It is yellowed by perspiration. Chlorine bleach will also destroy silk fabrics.


Variants


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.


Applications


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
shirt A shirt is a cloth garment for the upper body (from the neck to the waist). Originally an undergarment worn exclusively by men, it has become, in American English, a catch-all term for a broad variety of upper-body garments and undergarments. I ...
s, ties,
blouse A blouse (blau̇s, 'blau̇z, ) is a loose-fitting upper garment that was worn by workmen, peasants, artists, women, and children.The Concise Oxford English Dictionary It is typically gathered at the waist or hips (by tight hem, pleats, parter ...
s, formal dresses, high-fashion clothes, lining, lingerie, pajamas, robes, dress suits, sun dresses, and traditional Asian clothing. Silk is also excellent for insect-proof clothing, protecting the wearer from mosquitoes and
horseflies Horse-flies or horseflies are true flies in the family Tabanidae in the insect order Diptera. They are often large and agile in flight, and only the female horseflies bite animals, including humans, to obtain blood. They prefer to fly in sun ...
. Fabrics that are often made from silk include satin, charmeuse, habutai, chiffon, taffeta,
crêpe de chine A crêpe or crepe ( or , , Quebec French: ) is a very thin type of pancake. Crêpes are usually one of two varieties: ''sweet crêpes'' () or ''savoury galettes'' (). They are often served with a wide variety of fillings such as cheese, f ...
,
dupioni Dupioni (also referred to as douppioni or dupion) is a plain weave silk fabric, produced using fine yarn in the warp and uneven yarn reeled from two or more entangled cocoons in the weft. This creates tightly woven yardage with a highly-lustrous ...
, noil,
tussah Tussar silk (alternatively spelled as tussah, tushar, tassar, tussore, tasar, tussur, or tusser, and also known as (Sanskrit) ''kosa'' silk) is produced from larvae of several species of silkworms belonging to the moth genus ''Antheraea'', inclu ...
, and shantung, among others.


Furniture

Silk's attractive lustre and drape makes it suitable for many
furnishing ] The decorative arts are arts or crafts whose object is the design and manufacture of objects that are both beautiful and functional. It includes most of the arts making objects for the interiors of buildings, and interior design, but not usual ...
applications. It is used for upholstery, wall coverings, window treatments (if blended with another fiber), rugs, bedding, and wall hangings.


Industry

Silk had many industrial and commercial uses, such as in
parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who ...
s, bicycle tires, comforter filling, and artillery gunpowder bags.


Medicine

A special manufacturing process removes the outer sericin coating of the silk, which makes it suitable as non-absorbable
surgical suture A surgical suture, also known as a stitch or stitches, is a medical device used to hold body tissues together and approximate wound edges after an injury or surgery. Application generally involves using a needle with an attached length of threa ...
s. This process has also recently led to the introduction of specialist silk underclothing, which has been used for skin conditions including eczema. New uses and manufacturing techniques have been found for silk for making everything from disposable cups to drug delivery systems and holograms.


Biomaterial

Silk began to serve as a
biomedical Biomedicine (also referred to as Western medicine, mainstream medicine or conventional medicine)
material for sutures in surgeries as early as the second century CE. 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. Silks from ''Bombyx mori'', a kind of cultivated silkworm, are the most widely investigated silks. Silks derived from ''Bombyx mori'' are generally made of two parts: the
silk fibroin Fibroin is an insoluble protein present in silk produced by numerous insects, such as the larvae of ''Bombyx mori'', and other moth genera such as ''Antheraea'', '' Cricula'', '' Samia'' and '' Gonometa''. Silk in its raw state consists of two ...
fiber which contains a light chain of 25kDa and a heavy chain of 350kDa (or 390kDa) linked by a single disulfide bond and a glue-like protein, sericin, comprising 25 to 30 percentage by weight. Silk fibroin contains hydrophobic
beta sheet The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a g ...
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) Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula or , formally obtained by condensation of lactic acid with loss of water (hence its name). It can also be prepared by rin ...
and hundreds of times that of
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
. 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, 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 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. In addition, silk fibroin exhibits an inflammatory response similar to that of tissue culture plastic in vitro when assessed with human mesenchymal
stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...
s (hMSCs) or lower than collagen and PLA when implant rat MSCs with silk fibroin films in vivo. Thus, appropriate degumming and sterilization will assure the biocompatibility of silk fibroin, which is further validated by in vivo experiments on rats and pigs. 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 and diseases 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. Biodegradable materials can minimize the pain of patients from surgeries, especially in tissue engineering, since there is no need for surgery in order to remove the implanted scaffold.. Wang et al. 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 two popular enzymes for silk degradation. In addition,
gamma radiation A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically s ...
, as well as cell metabolism, can also regulate the degradation of silk. Compared with synthetic biomaterials such as polyglycolides and polylactides, silk is advantageous in some aspects of 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 on an as-needed basis, by mediating the content of beta sheets.


Genetic modification

Genetic modification of domesticated silkworms has been used to alter the composition of the silk. 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.


Cultivation

Silk moths lay eggs on specially prepared paper. The eggs hatch and the caterpillars (silkworms) are fed fresh
mulberry ''Morus'', a genus of flowering plants in the family Moraceae, consists of diverse species of deciduous trees commonly known as mulberries, growing wild and under cultivation in many temperate world regions. Generally, the genus has 64 identif ...
leaves. After about 35 days and 4 moltings, the caterpillars are 10,000 times heavier than when hatched and are ready to begin spinning a cocoon. A straw frame is placed over the tray of caterpillars, and each caterpillar begins spinning a cocoon by moving its head in a pattern. Two glands produce liquid silk and force it through openings in the head called spinnerets. Liquid silk is coated in sericin, a water-soluble protective gum, and solidifies on contact with the air. Within 2–3 days, the caterpillar spins about of filament and is completely encased in a cocoon. The silk farmers then heat the cocoons to kill them, leaving some to metamorphose into moths to breed the next generation of caterpillars. Harvested cocoons are then soaked in boiling water to soften the sericin holding the silk fibers together in a cocoon shape. The fibers are then unwound to produce a continuous thread. Since a single thread is too fine and fragile for commercial use, anywhere from three to ten strands are spun together to form a single thread of silk.


Animal rights

As the process of harvesting the silk from the cocoon kills the larvae by boiling, sericulture has been criticized by animal welfare activists, including People for the Ethical Treatment of Animals (PETA), who urge people not to buy silk items. Mahatma Gandhi was critical of silk production because of his
Ahimsa Ahimsa (, IAST: ''ahiṃsā'', ) is the ancient Indian principle of nonviolence which applies to all living beings. It is a key virtue in most Indian religions: Jainism, Buddhism, and Hinduism.Bajpai, Shiva (2011). The History of India ...
(non-violent) philosophy, which led to the promotion of cotton and Ahimsa silk, a type of wild silk made from the cocoons of wild and semi-wild silk moths.


See also

* Art silk *
Bulletproofing Bulletproofing is the process of making an object capable of stopping a bullet or similar high velocity projectiles (e.g. shrapnel). The term bullet resistance is often preferred because few, if any, practical materials provide complete protectio ...
* International Year of Natural Fibres *
Mommes Textile fibers, threads, yarns and fabrics are measured in a multiplicity of units. * A fiber, a single filament of natural material, such as cotton, linen or wool, or artificial material such as nylon, polyester, metal or mineral fiber, or man-m ...
*
Rayon Rayon is a semi-synthetic fiber, made from natural sources of regenerated cellulose, such as wood and related agricultural products. It has the same molecular structure as cellulose. It is also called viscose. Many types and grades of viscose f ...
* Sea silk * Silk waste *
Sinchaw Sinchaw, or Synchaw, was a silk type described in an early 19th century list of prices as “a firm thick even Kind of Goods”. Sinchaw was among the varieties of Chinese silk imported into the United States The United States of America ( ...
* Spider silk


References


Citations


Bibliography

* * Hill, John E. (2004)
''The Peoples of the West from the Weilüe''
魏略 ''by Yu Huan'' 魚豢'': A Third Century Chinese Account Composed between 239 and 265 AD.'' Draft annotated English translation. Appendix E. * Hill, John E. (2009) ''Through the Jade Gate to Rome: A Study of the Silk Routes during the Later Han Dynasty, 1st to 2nd centuries CE''. BookSurge, Charleston, South Carolina. . * Magie, David (1924). ''Historia Augusta Life of Heliogabalus''. Loeb Classical Texts No. 140: Harvard University Press..


Further reading

* Feltwell, John (1990). ''The Story of Silk''. Alan Sutton Publishing. . * Good, Irene (December 1995). "On the Question of Silk in Pre-Han Eurasia". ''Antiquity''. Vol. 69, Number 266. pp. 959–968. * Kadolph, Sara J. (2007). ''Textiles'' (10th ed.). Upper Saddle River: Pearson Prentice Hall. pp. 76–81. * Kuhn, Dieter (1995). "Silk Weaving in Ancient China: From Geometric Figures to Patterns of Pictorial Likeness". ''Chinese Science''. 12. pp. 77–114. * * Ricci, G.; et al. (2004). "Clinical Effectiveness of a Silk Fabric in the Treatment of Atopic Dermatitis". ''British Journal of Dermatology''. Issue 150. pp. 127–131. * Sung, Ying-Hsing. 1637. "Chapter 2. Clothing materials". ''Chinese Technology in the Seventeenth Century – T'ien-kung K'ai-wu''. Translated and annotated by E-tu Zen Sun and Shiou-chuan Sun. Pennsylvania State University Press, 1966. Reprint: Dover, 1997. * Liu, Xinru (1996). ''Silk and Religion: An Exploration of Material Life and the Thought of People, AD 600–1200''. Oxford University Press. * Liu, Xinru (2010). ''The Silk Road in World History''. Oxford University Press. ; (pbk).


External links


References to silk by Roman and Byzantine writersHistory of traditional silk in martial arts uniforms
*
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