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 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 (bees, wasps, and ants), silverfish, mayflies, thrips, leafhoppers, beetles, lacewings, fleas, flies, and midges. Other types of arthropods produce silk, most notably various arachnids, such as spiders.
"Silk" in seal script (top), Traditional (middle), and Simplified (bottom) Chinese
The word silk comes from Old English: sioloc, from Ancient Greek: σηρικός, romanized: sērikós, "silken", ultimately from an Asian source — compare Mandarin sī "silk", Manchurian sirghe, Mongolian sirkek.
Several kinds of wild silk, which are produced by caterpillars other than the mulberry silkworm, have been known and used in China, South Asia, and Europe since ancient times. 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.
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.
The earliest example of silk has been found in tombs at the neolithic site Jiahu in Henan, and dates back 8,500 years. Silk fabric from 3630 BC was used as wrapping for the body of a child from a Yangshao culture site in Qingtaicun at Xingyang, Henan.
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. 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-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 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.
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) dating between 2450 BC and 2000 BC, while "hard and fast evidence" for silk production in China dates back to around 2570 BC. 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."
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. 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, 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.
India is also the largest consumer of silk in the world. The tradition of wearing silk sarees for marriages and other auspicious ceremonies is a custom in Assam and southern parts of India. Silk is considered to be a symbol of royalty, and, historically, silk was used primarily by the upper classes. Silk garments and sarees produced in Kanchipuram, Pochampally, Dharmavaram, Mysore, Arani in the south, Banaras in the north, Bhagalpur and Murshidabad in the east are well recognized. In the northeastern state of Assam, three different types 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.
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.
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.
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, 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 laws were passed that forbade men from wearing silk garments, but these proved ineffectual. 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. Despite the popularity of silk, the secret of silk-making only reached Europe around AD 550, via the Byzantine Empire. Legend has it that monks working for the emperor Justinian I smuggled silkworm eggs to Constantinople in hollow canes from China. 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.
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. 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.
Despite injunctions against silk for men, silk has retained its popularity in the Islamic world because of its permissibility for women, and due to the presence of non-Muslim communities. The Muslim Moors brought silk with them to Spain during their conquest of the Iberian Peninsula.
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.
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.
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. 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.
Wild silk taken from the nests of native caterpillars was used by the Aztecs 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.
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 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. 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, 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, 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. 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).
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.
In Vietnamese legend, silk appeared in the first millennia AD and is still being woven today.
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.:104 The major silk producers are China (54%) and India (14%). Other statistics:
|Top Ten Cocoons (Reelable) Producers — 2005|
|Country||Production (Int $1000)||Footnote||Production (1000 kg)||Footnote|
|People's Republic of China||978,013||C||290,003||F|
|No symbol = official figure, F = FAO estimate,*= Unofficial figure, C = Calculated figure;|
Production in Int $1000 have been calculated based on 1999–2001 international prices
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.
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. 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.
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.'
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.
|Comparison of silk fibers||Linear density (dtex)||Diameter (μm)||Coeff. variation|
|Moth: Bombyx mori||1.17||12.9||24.8%|
|Spider: Argiope aurentia||0.14||3.57||14.8%|
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.
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.
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.
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.
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. New uses and manufacturing techniques have been found for silk for making everything from disposable cups to drug delivery systems and holograms.
Silk has been considered as a luxurious textile since 3630 BC. However, it started to serve also as a biomedical material for suture in surgeries decades ago. In the past 30 years, it has been widely studied and used as a biomaterial, which refers to materials used for medical applications in organisms, due to its excellent properties, including remarkable mechanical properties, comparative biocompatibility, tunable degradation rates in vitro and in vivo, the ease to load cellular growth factors (for example, BMP-2), and the 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 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 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, 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,
|Source Organisms||Tensile strength
|Philosamia cynthia ricini||1.9–3.5||29–31||28.0–24.0|
|Coscinocera hercules||5 ± 1||87 ± 17||12 ± 5|
|Hyalophora euryalus||2.7 ± 0.9||59 ± 18||11 ± 6|
|Rothschildia hesperis||3.3 ± 0.8||71 ± 16||10 ± 4|
|Eupackardia calleta||2.8 ± 0.7||58 ± 18||12 ± 6|
|Rothschildia lebeau||3.1 ± 0.8||54 ± 14||16 ± 7|
|Antheraea oculea||3.1 ± 0.8||57 ± 15||15 ± 7|
|Hyalophora gloveri||2.8 ± 0.4||48 ± 13||19 ± 7|
|Copaxa multifenestrata||0.9 ± 0.2||39 ± 6||4 ± 3|
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 cells (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 (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. 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 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.
Silk moths lay eggs on specially prepared paper. The eggs hatch and the caterpillars (silkworms) are fed fresh mulberry 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 1 mile 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.
As the process of harvesting the silk from the cocoon kills the larvae by boiling them, sericulture has been criticized by animal welfare and rights activists. Mohandas Gandhi was critical of silk production based on the Ahimsa 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.
Silk swaths gathered from the large hammock-net cocoons of Gloveria psidii (= Sagana sapotoza) and pasted together to form a kind of hard cloth, or paper, were an important trade item in Mexico at the time of Moctezuma II
[silkworms] have the capacity to feel and the right to live free from pain and suffering.
Silk Production Causes Painful Death for Insects
Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body that arises from abnormal breathing. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can induce asphyxia, all of which are characterized by an inability of an individual to acquire sufficient oxygen through breathing for an extended period of time. Asphyxia can cause coma or death.
In 2015 about 9.8 million cases of unintentional suffocation occurred which resulted in 35,600 deaths. The word asphyxia is from Ancient Greek α- "without" and σφύξις sphyxis, "squeeze" (throb of heart).Belt and Road Initiative
The Belt and Road Initiative (BRI), is a global development strategy adopted by the Chinese government involving infrastructure development and investments in 152 countries and international organizations in Asia, Europe, Africa, the Middle East, and the Americas.
"Belt" refers to the overland routes for road and rail transportation, called "the Silk Road Economic Belt"; whereas "road" refers to the sea routes, or the 21st Century Maritime Silk Road.It was known as the One Belt One Road (OBOR) (Chinese: 一带一路) and the Silk Road Economic Belt and the 21st-century Maritime Silk Road (Chinese: 丝绸之路经济带和21世纪海上丝绸之路) until 2016 when the Chinese government considered the emphasis on the word "one" was prone to misinterpretation.The Chinese government calls the initiative "a bid to enhance regional connectivity and embrace a brighter future". Some observers see it as a push for Chinese dominance in global affairs with a China-centered trading network. The project has a targeted completion date of 2049, which coincides with the 100th anniversary of the People's Republic of China.Bombyx mori
Bombyx mori, the domestic silkmoth, is an insect from the moth family Bombycidae. It is the closest relative of Bombyx mandarina, the wild silkmoth. The silkworm is the larva or caterpillar of a silkmoth. It is an economically important insect, being a primary producer of silk. A silkworm's preferred food is white mulberry leaves, though they may eat other mulberry species and even osage orange. Domestic silkmoths are closely dependent on humans for reproduction, as a result of millennia of selective breeding. Wild silkmoths are different from their domestic cousins as they have not been selectively bred; they are not as commercially viable in the production of silk.
Sericulture, the practice of breeding silkworms for the production of raw silk, has been under way for at least 5,000 years in China, whence it spread to India, Korea, Japan, and the West. The silkworm was domesticated from the wild silkmoth Bombyx mandarina, which has a range from northern India to northern China, Korea, Japan, and the far eastern regions of Russia. The domesticated silkworm derives from Chinese rather than Japanese or Korean stock.Silkworms were unlikely to have been domestically bred before the Neolithic age. Before then, the tools to manufacture quantities of silk thread had not been developed. The domesticated B. mori and the wild B. mandarina can still breed and sometimes produce hybrids.Domestic silkmoths are very different from most members in the genus Bombyx; not only have they lost the ability to fly, but their color pigments are also lost.History of silk
The production of silk originates in China in the Neolithic (Yangshao culture, 4th millennium BC). Silk remained confined to China until the Silk Road opened at some point during the later half of the 1st millennium BC. China maintained its virtual monopoly over silk production for another thousand years. Not confined to clothing, silk was also used for a number of other applications, including writing, and the color of silk worn was an important guide of social class during the Tang dynasty.
Silk cultivation spread to Japan around 300 AD, and, by 552 AD, the Byzantines managed to obtain silkworm eggs and were able to begin silkworm cultivation. The Arabs also began to manufacture silk at the same time. As a result of the spread of sericulture, Chinese silk exports became less important, although they still maintained dominance over the luxury silk market. The Crusades brought silk production to Western Europe, in particular to many Italian states, which saw an economic boom exporting silk to the rest of Europe. Changes in manufacturing techniques also began to take place during the Middle Ages, with devices such as the spinning wheel first appearing. During the 16th century, France joined Italy in developing a successful silk trade, though the efforts of most other nations to develop a silk industry of their own were unsuccessful.
The Industrial Revolution changed much of Europe's silk industry. Due to innovations on spinning cotton, cotton became much cheaper to manufacture and therefore caused more expensive silk production to become less mainstream. New weaving technologies, however, increased the efficiency of production. Among these was the Jacquard loom, developed for silk embroidery. An epidemic of several silkworm diseases caused production to fall, especially in France, where the industry never recovered. In the 20th century Japan and China regained their earlier role in silk production, and China is now once again the world's largest producer of silk. The rise of new fabrics such as nylon reduced the prevalence of silk throughout the world, and silk is now once again a rare luxury good, much less important than in its heyday.Lingerie
Lingerie (UK: , US: ) is a category of women's clothing including at least undergarments (mainly brassieres), sleepwear and lightweight robes. The specific choice of the word often is motivated by an intention to imply the garments are alluring, fashionable or both.
Lingerie is made of lightweight, stretchy, smooth, sheer or decorative fabrics such as silk, satin, Lycra, charmeuse, chiffon or (especially and traditionally) lace. These fabrics can be made of natural fibres like silk or cotton or of synthetic fibres like polyester or nylon.Moth
Moths comprise a group of insects related to butterflies, belonging to the order Lepidoptera. Most lepidopterans are moths, and there are thought to be approximately 160,000 species of moth, many of which have yet to be described. Most species of moth are nocturnal, but there are also crepuscular and diurnal species.Pupa
A pupa (Latin: pūpa, "doll"; plural: pūpae) is the life stage of some insects undergoing transformation between immature and mature stages. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, with four life stages: egg, larva, pupa, and imago. The processes of entering and completing the pupal stage are controlled by the insect's hormones, especially juvenile hormone, prothoracicotropic hormone, and ecdysone.
The pupae of different groups of insects have different names such as chrysalis for the pupae of butterflies and tumbler for those of the mosquito family. Pupae may further be enclosed in other structures such as cocoons, nests, or shells.Queen's Counsel
A Queen's Counsel (post-nominal QC), or King's Counsel (post-nominal KC) during the reign of a king, is a lawyer (usually a barrister or advocate) who is appointed by the monarch to be one of "Her Majesty's Counsel learned in the law." The term is recognised as an honorific. The position exists in some Commonwealth jurisdictions around the world, but other Commonwealth countries have either abolished the position, or re-named it to eliminate monarchical connotations, such as "Senior Counsel" or "Senior Advocate". Queen's Counsel is an office, conferred by the Crown, that is recognised by courts. Members have the privilege of sitting within the bar of court.
As members wear silk gowns of a particular design (see court dress), appointment as Queen's Counsel is known informally as taking silk, and hence QCs are often colloquially called silks. Appointments are made from within the legal profession on the basis of merit rather than a particular level of experience. However, successful applicants tend to be barristers, or (in Scotland) advocates with 15 years of experience or more.Rayon
Rayon is a manufactured fiber made from regenerated cellulose fiber. The many types and grades of rayon can imitate the feel and texture of natural fibers such as silk, wool, cotton, and linen. The types that resemble silk are often called artificial silk.
Since rayon is manufactured from naturally occurring polymers, it is not considered to be synthetic. Technically, the term synthetic fiber is reserved for fully synthetic fibers. In manufacturing terms, rayon is classified as "a fiber formed by regenerating natural materials into a usable form". Specific types of rayon include viscose, modal and lyocell, each of which differs in manufacturing process and properties of the finished product.
Rayon is made from purified cellulose, harvested primarily from wood pulp, which is chemically converted into a soluble compound. It is then dissolved and forced through a spinneret to produce filaments which are chemically solidified, resulting in fibers of nearly pure cellulose. Unless the chemicals are handled carefully, workers can be seriously harmed by the carbon disulfide used to manufacture most rayon.Sari
A sari, saree or shari is a women's garment from the Indian subcontinent that consists of a drape varying from five to nine yards (4.5 metres to 8 metres) in length and two to four feet (60 cm to 1.20 m) in breadth that is typically wrapped around the waist, with one end draped over the shoulder, baring the midriff. There are various styles sari manufacture and draping, the most common being the Nivi style, which originated in Deccan region of India. The sari is worn with fitted bodice commonly called a choli (ravike in southern India, and cholo in Nepal) and petticoat called parkar or ul-pavadai. In the modern Indian subcontinent, the sari is considered a cultural icon.Screen printing
Screen printing is a printing technique whereby a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed. One color is printed at a time, so several screens can be used to produce a multicoloured image or design.
There are various terms used for what is essentially the same technique. Traditionally the process was called screen printing or silkscreen printing because silk was used in the process. It is also known as serigraphy, and serigraph printing. Currently, synthetic threads are commonly used in the screen printing process. The most popular mesh in general use is made of polyester. There are special-use mesh materials of nylon and stainless steel available to the screen printer. There are also different types of mesh size which will determine the outcome and look of the finished design on the material.Sericulture
Sericulture, or silk farming, is the cultivation of silkworms to produce silk. Although there are several commercial species of silkworms, Bombyx moth (the caterpillar of the domesticated silk moth) is the most widely used and intensively studied silkworm. Silk was believed to have first
been produced in China as early as the Neolithic period. Sericulture has become an important cottage industry in countries such as Brazil, China, France, India, Italy, Japan, Korea, and Russia. Today, China and India are the two main producers, with more than 60% of the world's annual production.Silk Road
The Silk Road was a network of trade routes which connected the East and West, and was central to the economic, cultural, political, and religious interactions between these regions from the 2nd century BCE to the 18th century. The Silk Road primarily refers to the terrestrial routes connecting East Asia and Southeast Asia with South Asia, Persia, the Arabian Peninsula, East Africa and Southern Europe.
The Silk Road derives its name from the lucrative trade in silk carried out along its length, beginning in the Han dynasty in China (207 BCE–220 CE). The Han dynasty expanded the Central Asian section of the trade routes around 114 BCE through the missions and explorations of the Chinese imperial envoy Zhang Qian, as well as several war victories. The Chinese took great interest in the safety of their trade products, and extended the Great Wall of China to ensure the protection of the trade route.The Silk Road trade played a significant role in the development of the civilizations of China, Korea, Japan, the Indian subcontinent, Iran, Europe, the Horn of Africa and Arabia, opening long-distance political and economic relations between the civilizations. Though silk was the major trade item exported from China, many other goods and ideas were exchanged, including religions (especially Buddhism), syncretic philosophies, sciences, and technologies like paper and gunpowder. So in addition to economic trade, the Silk Road was a route for cultural trade among the civilizations along its network. Diseases, most notably plague, also spread along the Silk Road.In June 2014, UNESCO designated the Chang'an-Tianshan corridor of the Silk Road as a World Heritage Site. The Indian portion is on the tentative site list.Silk Road (marketplace)
Silk Road was an online black market and the first modern darknet market, best known as a platform for selling illegal drugs. As part of the dark web, it was operated as a Tor hidden service, such that online users were able to browse it anonymously and securely without potential traffic monitoring. The website was launched in February 2011; development had begun six months prior. Initially there were a limited number of new seller accounts available; new sellers had to purchase an account in an auction. Later, a fixed fee was charged for each new seller account.In October 2013, the Federal Bureau of Investigation (FBI) shut down the website and arrested Ross Ulbricht under charges of being the site's pseudonymous founder "Dread Pirate Roberts". On 6 November 2013, Silk Road 2.0 came online, run by former administrators of Silk Road. It too was shut down, and the alleged operator was arrested on 6 November 2014 as part of the so-called "Operation Onymous". Ulbricht was convicted of eight charges related to Silk Road in the U.S. Federal Court in Manhattan and was sentenced to life in prison without possibility of parole.Silk in the Indian subcontinent
Silk in the Indian subcontinent is a luxury good. In India, about 97% of the raw mulberry silk is produced in the five Indian states of Karnataka, Andhra Pradesh, Tamil Nadu, West Bengal and Jammu and Kashmir. Mysore and North Bangalore, the upcoming site of a US$20 million "Silk City", contribute to a majority of silk production. Another emerging silk producer is Tamil Nadu where mulberry cultivation is concentrated in Salem, Erode and Dharmapuri districts. Hyderabad, Andhra Pradesh and Gobichettipalayam, Tamil Nadu were the first locations to have automated silk reeling units.Spider
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs able to inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 113 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.
Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.
The species Bagheera kiplingi was described as herbivorous in 2008, but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. It is estimated that the world's 25 million tons of spiders kill 400–800 million tons of prey per year. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, so they liquefy their food by flooding it with digestive enzymes. They also grind food with the bases of their pedipalps, as arachnids do not have the mandibles that crustaceans and insects have.
To avoid being eaten by the females, which are typically much larger, male spiders identify themselves to potential mates by a variety of complex courtship rituals. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.
While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.Spider silk
Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey. They can also use their silk to suspend themselves, to float through the air, or to glide away from predators. Most spiders vary the thickness and stickiness of their silk for different uses.
In some cases, spiders may even use silk as a source of food. While methods have been developed to collect silk from a spider by force, it is difficult to gather silk from many spiders in a small space, in contrast to silkworm "farms".Surgical suture
Surgical suture is a medical device used to hold body tissues together after an injury or surgery. Application generally involves using a needle with an attached length of thread. A number of different shapes, sizes, and thread materials have been developed over its millennia of history. Surgeons, physicians, dentists, podiatrists, eye doctors, registered nurses and other trained nursing personnel, medics, and clinical pharmacists typically engage in suturing. Surgical knots are used to secure the sutures.Textile
A textile is a flexible material consisting of a network of natural or artificial fibers (yarn or thread). Yarn is produced by spinning raw fibres of wool, flax, cotton, hemp, or other materials to produce long strands. Textiles are formed by weaving, knitting, crocheting, knotting or tatting, felting, or braiding.
The related words "fabric" and "cloth" and "material" are often used in textile assembly trades (such as tailoring and dressmaking) as synonyms for textile. However, there are subtle differences in these terms in specialized usage. A textile is any material made of interlacing fibres, including carpeting and geotextiles. A fabric is a material made through weaving, knitting, spreading, crocheting, or bonding that may be used in production of further goods (garments, etc.). Cloth may be used synonymously with fabric but is often a piece of fabric that has been processed.
Clothing materials and parts
|Animal hides / Leather|