New Post: Silk Production

Silk Production

Silk Production by Silkworms

 The Invention of Silk

Silk is a type of fabric that has been used since around 3000 BC and was discovered in Neolithic China. According to legend, during that time, the wife of the Yellow Emperor, Emperor Huangdi, named Empress Hsi-Ling-Shih, was walking in her garden when a silkworm cocoon fell into her tea. As the cocoon began to dissolve in the tea, a thread known as silk was formed. Realizing that the thread was made from the cocoon, Empress Hsi-Ling-Shih started to examine the silkworm and its cocoons, thus discovering how silk was obtained. According to the same legend, it is believed that Empress Hsi-Ling-Shih was the one who built the first silk loom after discovering silk. Hsi-Ling-Shih is referred to as the Goddess of Silk in some Chinese texts.

What is Silk? How Do Silkworms Produce Silk?

Silk, scientifically known as Bombyx mori, is a type of protein fiber produced by silkworms. It can also be produced by different insect and spider species. However, silkworms are the main source of silk production worldwide. The cocoons they spin around their larvae are made up of silk fibers. The silk we use in our daily lives is obtained from these cocoons.

Silk fibers primarily consist of two proteins, with fibroin being the main component. Fibroin is a water-insoluble protein with high density. Approximately 75% of untreated silk is composed of fibroin. Sericin, on the other hand, acts as an adhesive, holding the fibroin proteins together, and is mostly found on the outer surface of silk fibers. Sericin is a non-flexible, brittle substance with antibacterial properties. It is resistant to ultraviolet radiation and has the ability to absorb and release moisture. However, during the process of obtaining silk from silkworm cocoons, sericin is removed to give silk its shine.

When secreted, fibroin proteins are in a liquid crystal structure, which hardens upon contact with air. Sericin, on the other hand, holds the silk fibers together. The silkworm then rotates the cocoon approximately 300,000 times over a period of 3-8 days to form the cocoon. This process affects the structure of silk fibers.

Silk fibers are very thin, long, lightweight, and soft. They are also twice as flexible as nylon and eight times stronger than steel. Due to its insulation properties, ability to be dyed, shiny appearance, and insulating characteristics, silk is used in various fields such as textiles, healthcare, and industrial applications.

Silk production involves the cultivation of silkworms and the harvesting of their silk. Here is a step-by-step explanation of the process:

SILKWORM CULTIVATION: The process begins with the cultivation of silkworms, which are actually the larvae of silk moths (Bombyx mori). Silkworm eggs are placed on specially prepared paper or cloth, and they hatch into larvae within a week.

FEEDING THE SILKWORMS: The silkworm larvae are fed a diet of fresh mulberry leaves. Mulberry leaves are the primary food source for silkworms, as they provide the necessary nutrients for the larvae to grow and spin silk.

GROWTH AND MOLTING: The silkworms go through several stages of growth, called instars, during which they shed their skin (molting) to accommodate their increasing size. After each molt, they continue to feed on mulberry leaves until they reach their maximum size.

SILK PRODUCTION: Once the silkworms reach the final instar, they stop eating and begin to spin cocoons. They produce silk by extruding a liquid protein called fibroin through spinnerets, special glands in their heads. The liquid silk protein comes into contact with the air and solidifies, forming a single continuous thread.

SPINNING COCOONS: The silkworms create the cocoons by moving their heads in a figure-eight pattern, secreting the silk thread around themselves. The thread forms a protective covering for the pupa that will later transform into a moth. It takes about 2-3 days for the silkworms to complete the spinning of the cocoons.

HARVESTING THE COCOONS: Once the cocoons are fully formed, they are carefully harvested. This is usually done before the pupa inside undergoes metamorphosis and breaks the silk thread. The cocoons are collected and sorted for further processing.

SILK REELING: The harvested cocoons are subjected to a process called silk reeling. The cocoons are placed in hot water or exposed to steam, which softens the sericin, a gummy substance that holds the silk threads together. This allows the silk to be unraveled. Multiple silk filaments are reeled together to form a single, stronger strand.

SILK PROCESSING: The silk thread is then washed, dried, and sometimes dyed before being spun onto reels or bobbins. The silk can be further processed through various methods like twisting, plying, and weaving to create different types of silk fabrics with distinct textures and properties.

It's worth noting that in commercial silk production, the majority of silkworms do not survive the process, as the cocoons are typically boiled before the pupae can break the silk threads. However, there are also methods that allow the pupae to emerge as moths, but the silk obtained from these cocoons is less uniform and more suitable for specialty applications.