Silk

Silk is a natural protein fiber that can be woven or knitted into beautiful textiles. It is made mostly of a substance called fibroin, with a smaller coating of sericin. The shine and smooth feel of silk come from the special shape of its fibers, which bend light in interesting ways.

The most famous kind of silk comes from the cocoons of mulberry silkworm larvae, which are carefully raised for this purpose. But many other insects also produce silk, including moths, spiders, and even some beetles and flies. Scientists study these different silks to learn more about their unique properties.

Silk has been treasured for thousands of years because of its soft, shiny texture and durability. It is used to make clothing, home decorations, and many other useful items. The way silk is made and used has evolved, but its special qualities continue to make it highly valued around the world.

Etymology

The word silk has an interesting history. It comes from old languages like Old English, Latin, Ancient Greek, and even from Chinese. In Chinese, the word for silk is sī, which helped spread the word to other languages around the world.

History

Main article: History of silk

The making of silk began in central China during ancient times, and later spread to other parts of the world. For a long time, China kept the secret of silk making to itself, but eventually, the knowledge traveled along trade routes.

Wild silk

Main article: Wild silk

Different kinds of wild silk have been used in China, South Asia, and Europe since old times. These silks were often harder to work with because they came in shorter pieces or had a natural coating that made them tricky to spin into long threads. Sometimes, people used spider webs as a bandage in ancient Greece and Rome, or made fabric from butterfly nests in the Aztec Empire.

China

Silk was first made into fabric in ancient China. The oldest bits of silk found so far are from about 8,500 years ago. Legends say an empress named Leizu helped develop silk. At first, silk was very special and only for emperors, but later it became more common and was traded widely. Silk was also used for writing because it was smooth and held ink well.

Japan

Main article: Japanese silk

Evidence shows that making silk has been done in Japan since very old times. Japan became a big silk producer in the early 1900s, but after World War II, synthetic materials like nylon became popular, and Japan’s silk industry grew smaller.

India

Silk has a long history in India, where it is known by different names in different places. Archaeologists have found signs that people in ancient India made silk from wild silkworms. Today, India is one of the biggest silk producers in the world, especially in states like Andhra Pradesh and Karnataka.

Thailand

Main article: Thai silk

Thailand makes silk all year round using two kinds of silkworms. Women in Thailand have traditionally woven silk by hand and taught their daughters this skill. Thai silk often has beautiful, detailed patterns and comes in many colors.

Bangladesh

Main article: Rajshahi silk

The northern part of Bangladesh, called Rajshahi, is known for its silk industry. There are three main types of silk made there, and Bengali silk was once traded internationally for many centuries.

Central Asia

The old wall paintings in Samarkand show Chinese emissaries bringing silk and silkworm cocoons to local rulers.

Middle East

In old Jewish writings, a special red cloth called “sheni tola’at” was used in important ceremonies. In some Islamic teachings, men are not allowed to wear silk, though there are discussions about small decorative pieces.

Ancient Mediterranean

In old stories, Odysseus described wearing a shirt that shone like an onion skin, which might have been silk. The Roman Empire traded for Chinese silk, even though laws tried to limit its use. Silk making finally reached Europe around the year 550 AD when monks brought silkworm eggs hidden in hollow sticks.

Medieval and modern Europe

Italy became a major silk producer in the Middle Ages, especially in cities like Catanzaro and Lucca. Other places like Genoa, Venice, and Florence also made silk. In France, Lyon became a center for silk production, and in England, attempts to grow silk were made but faced challenges.

North America

Native people in Mexico used wild silk from caterpillars. Later, silkworms were brought to America, and places like Manchester, Connecticut, and Paterson, New Jersey, became important for silk production. During World War II, when silk from Asia became hard to get, people in the U.S. started looking for other materials like nylon.

Production process

The process of making silk is called sericulture. It starts with growing silkworms on mulberry leaves. When the silkworms make their cocoons, they are gently dissolved in boiling water. This helps to separate the long fibers of silk, which can then be spun into thread.

To make just 1 kilogram of silk, silkworms need to eat 104 kilograms of mulberry leaves. About 3,000 silkworms are needed to make one kilogram of silk, and around 5,000 silkworms are needed for a pure silk kimono. The biggest producers of silk are China and India.

Making silk can use a lot of water and resources, which can affect the environment. This is because silk comes from animals, and it needs more care and inputs compared to some plant-based fibers.

Top Ten Cocoons (Reelable) Producers – 2005
Country	Production (Int $1000)	Footnote	Production (1000 kg)	Footnote
China	978,013	C	290,003	F
India	259,679	C	77,000	F
Uzbekistan	57,332	C	17,000	F
Brazil	37,097	C	11,000	F
Iran	20,235	C	6,088	F
Thailand	16,862	C	5,000	F
Vietnam	10,117	C	3,000	F
Democratic People's Republic of Korea	5,059	C	1,500	F
Romania	3,372	C	1,000	F
Japan	2,023	C	600	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 Source: Food And Agricultural Organization of United Nations: Economic And Social Department: The Statistical Division

Properties

Silk fibers from silkworms have a special shape that looks like a triangle with rounded corners. They are very thin, about 5 to 10 micrometers wide. Silk has a smooth and soft feel that is not slippery. It is one of the strongest natural fibers, but it can lose some strength when it gets wet.

Silk is made from two main proteins. The most important one is called fibroin, which gives silk its structure. The other protein, sericin, acts like glue to hold the fibers together. Silk can be damaged by strong acids and certain cleaning products, but it is strong and resistant because of the way its molecules are arranged.

Variants

Regenerated silk fiber

RSF is made by dissolving silkworm cocoons with chemicals, but it keeps the same tiny thread-like parts called microfibrils. These parts are then pushed through a small opening, where they come together to form a new fiber. This new material is said to be twice as strong as regular silk.

Applications

Silk is a natural fiber that is very useful for many things. It is good for clothing because it can keep you cool in the summer and warm in the winter. It is used to make shirts, ties, dresses, and many other kinds of clothes.

Silk is also used to make things for our homes, like furniture covers and decorations. In the past, it was used for important things like parachutes and medical stitches. Scientists study silk because it is strong and safe for the body, and it can be made into many shapes for use in medicine and other areas.

Cultivation

Silk moths lay eggs on special paper. When the eggs hatch, the tiny caterpillars, called silkworms, eat fresh mulberry leaves. After about 35 days, the silkworms get much bigger and start making a cocoon. They spin the cocoon by moving their heads in a special way. Two glands in their heads make liquid silk that comes out through small holes called spinnerets. The liquid silk is coated in a protective substance that hardens when it touches air. In just a few days, the silkworm makes a cocoon around itself.

After the cocoons are made, silk farmers carefully heat them. Some cocoons are left to metamorphose into moths so new silkworms can be raised. The cocoons are then soaked in hot water to soften the coating on the silk. The silk threads are then unwound and combined to make stronger threads that can be used to make fabric.

Animal rights

When people collect silk from cocoons, the young insects inside usually cannot survive. Because of this, some groups, like People for the Ethical Treatment of Animals, ask people to think carefully before buying silk.

A famous leader named Mahatma Gandhi did not like silk because he believed in being kind to all living things. Because of his ideas, some people now look for a special kind of silk called Ahimsa silk that comes from wild silk moths.