Silk

How is Silk Made?

Usually, you choose to wear the most expensive fabric like silk to a wedding and function. Do you know how and where silk is obtained from? The most lustrous fabric of all times, silk, is a natural fibre like cotton and wool. Silk is obtained from Bombyx mori’s cocoon, a type of silkworm. The larvae of the mulberry silkworms produce the most popular mulberry silk.  Silk is produced by rearing silkworms in captivity. Thus, the fabric is a natural animal fibre. The process by which silk is produced is called sericulture. Here you will learn in-depth about how  is silk obtained from silkworm, and different types of silk.

 

How is Silk Obtained from Cocoon of Silkworms?

Let us find out how is silk obtained from cocoon of silkworms in detail.  Here is a step by step process of silk production. 

  1. At the larva stage, the silkworms produce fibres of silk.  The larva weaves a cocoon in two or three days to protect itself for the development of pupa. 

  2. Silk is obtained from the silkworm before it matures into an adult silk moth.  Furthermore, the farmer extracts silk fibre in its pupa stage. 

  3. Then, he submerges the cocoons in boiling water to soften the layers of the cocoons.

  4.  The silk workers brush the cocoons to untangle the silk strands. 

  5. Subsequently, they reel the silk strands into a continuous string. Reeling is the process of exposing the cocoons to extreme heat to separate the silk fibres.  These fibres are twisted to become silk yarn.

  6. Thereafter, the silk workers roll the silk yarn under the roller to make it uniform.

  7. Henceforth, the manufacturers dye the yarns to produce colourful silk fabric.

  8. Finally, the producers can construct a garment from the silk yarn.

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      submerged collected cocoons in boiling water


What is the Silk Structure?

Silk is made up of protein fibre, namely, 70% of fibroin (the filament) and 30% of sericin.  The mulberry silkworms produce these two proteins in its cocoon. Fibroin consists of the sequence of long-chain amino acids Gly-Ser-Gly-Ala-Gly-Ala.  Furthermore, it forms beta-keratin.  Fibroin is protected with a sticky layer of sericin.   The coating of sericin results in intramolecular and intermolecular hydrogen bonding between the amino acid groups which provides large forces of attraction. Thus, sericin makes the silk strand of high-tensile strength and holds the silk structure together.

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Position of sericin and fibroin in silk structure

 

Types of Silk Fibres

Different varieties of silkworms produce different types of silk.  However, the quality differs based on the chemical composition of silk.  Furthermore, silk formations are of two types – natural and artificial silk.  Basically, natural silk is obtained from the cocoons of silkworms.  Such silk is made up of protein. On the other hand, artificial silk is made up of wood pulp, such as rayon.  Here are some examples of silk.

  1. Mulberry Silk – It is the most substantial textile.  Mulberry silk is the softest and the most durable fabric.

  2. Eri Silk – Another name for eri silk is peace silk because its production does not include the killing of silkworms.  It is heavier and more durable in comparison to mulberry silk.

  3. Tasar Silk – India and Japan produce this variety of silk.  Green silkworms are the producer of Tasar silk.

  4. Spider Silk – It is the most expensive variety of silk.  Manufacturers use spider silk to produce microscopes, bulletproof vests, etc.

  5. Muga Silk – The natives of Assam produce this variety of fabric using semi-domesticated muga silkworms.

  6. Sea Silk – Another name for sea silk is mussel silk since species of mussel of the Mediterranean Sea produce it.

  7. Coan Silk – Silkworms, which feed on oak, pine, and juniper trees produce coan silk.  You will find this variety in Greece, Turkey, and Italy. 


 Fun Facts on Silk

  1. As much as 1.5 km of silk filament can be drawn from a single cocoon of a silkworm.

  2. Apart from silkworms, other insects like raspy crickets and web spinners can also produce silk.

  3. The emperors kept the production of silk as a guarded secret for more than two thousand years.

  4. In ancient times, ordinary people were prohibited from wearing silk garments.

FAQ (Frequently Asked Questions)

1. How Is Silk Obtained From The Rearing Of Silkworms In The Process Of Sericulture?

A farmer produces silk through the process of sericulture.  The silk fibre is obtained from the rearing of silkworms.  A female silk moth lays multiple eggs at one time.  The harvester keeps these eggs at a warm temperature of 75 to 85 degrees Fahrenheit up to fourteen days.  The farmer needs to take good care of these delicate larvae and feed them mulberry leaves.  When they are four weeks old, they begin to spin cocoons of silk fibres by their skin gland.  The farmer does not disturb them during their two weeks of metamorphosis phase. Otherwise, development may not occur.  The cocoons are exposed to high heat so that the upper layers of the cocoons soften.  The high-temperature enables the farmer to separate the silk fibres from the cocoon.  The process of extracting silk threads from the cocoon is known as reeling of silk.

2. How Would You Explain The Chemical Composition Of Silk?

In the process of weaving a cocoon, the silkworm secrets Silk which is made up of two significant natural proteins, namely, sericin and fibroin.  Silk structure mainly consists of fibroin, which is an insoluble protein.  Sericin and Fibroin are in the ratio of 30:70 by mass. During the formation of silk, the secreted Fibroin is covered with a layer of Sericin. Fibroin protein structure has layers of anti-parallel long-chain amino acids with its repeating unit as (Gly-Ser-Gly-Ala-Gly-Ala)n. Sericin structure has various types of amino acids with serine having the maximum percentage. The coating of sericin results in intramolecular and intermolecular hydrogen bonding between the amino acid groups, which provides large forces of attraction. It results in high tensile strength and glue-like structure of the silk fibre.