◉History◉

Origin of silk, raw silk, and filature

It is said that silk originated from China. The oldest silks confirmed are the silk cloth excavated from the site of Wuxing District, Zhejiang Province (around 2700 B.C.) and the ”cocoon torn in two pieces” (3000 to 2300 B.C.). In addition, silk cloth and ancient Chinese inscriptions on bone and tortoise shells during the Yin Dynasty (1500 to 1000 B.C.), the gold silkworm during the Zhou Dynasty (around 643 B.C.), and others were found. Since untwisted threads were used as warps and woofs for silk textiles at this time, it is considered that the reeling technology was already known by this time.
Extract from the catalogue of the 4th Exhibition of the Nippon Silk Center, “Filature.”

Origin in Japan

Though there is no accepted view of the origin of filature in Japan, there is a description in the ancient times of the Nihonshoki (Chronicles of Japan),” When Uke Mochi No Kami (God of Food) was found dead, a silkworm came out of his eyebrow… The Sun Goddess, Amaterasu O-Mikami taught to put the cocoon (silkworm) in her mouth to reel a thread. This was the beginning of sericulture.” A Chinese historical record ”Gishi-wajinden” describes that Yamato-Nishiki(Japanese silk textile) was presented to Wei from the Yamatai-Koku kingdom in the third century, and it is estimated that a technique to make threads from cocoons was already developed by this time.
Extract from the catalogue of the 4th Exhibition of the Nippon Silk Center, “Filature.”

Origin of filature in Gunma Prefecture

In the Gunma region (Kozuke-no-kuni), people naturalized from abroad often visited the Kanra region from old times, and a roll of Ki-Ashiginu (yellow thick silk fabric), which was contributed to the Court from Nitta-gun during the Nara Period, is stored carefully at the Shosoin.
Hence, it is considered that classical filature was already performed at this time. The Engi-Shiki, which was edited in the tenth century, records that silk was produced in 48 out of 61 provinces, and they were classified into Joshi-koku (producer of high-quality silk-yarn), Chushi-koku (producer of medium quality silk-yarn), and Soshi-koku (producer of rough silk-yarn) according to the quality. At this time, Kozuke-no-kuni was ranked as a Soshi-koku, and a tributary of Ashiginu. Soshi is a general name of thick threads (unevenly spun silk thread is the original meaning) and Ashiginu means thick silk fabric. It seems that the spread of sericulture was delayed in Kozuke-no-kuni in the ancient time and the technical level was rather backward compared to western parts of Japan.
Extract from the catalogue of the 4th Exhibition of the Nippon Silk Center, “Filature.”

Opening of the Yokohama Port and expansion of silk-reeling industry

Triggered by the arrival of Admiral Perry (Matthew Calbraith Perry) from the United States, Japan’s isolation policy, which had continued for about 215 years, marked the end in 1859. After that, Japanese silk-reeling industry changed dramatically, and its silkworm eggs and raw silk started to be sold significantly as global products.
Right after the opening of the port, silkworm eggs were exported most largely at first. This is because a pebrine of silkworms spread in France and Italy. After Pasteur established a method to control pebrine later, the export of silkworm eggs decreased rapidly.
During this period, Yahei Tajima living in Gunma Prefecture established Japan’s first company of silkworm eggs, ”Shimamura Kangyo Kaisha” in Year 5 of the Meiji Period (1872). He visited Italy in Year 12 of the Meiji Period (1879) to export silkworm eggs directly, and deployed energetic activities globally.
The end of a long period of isolation by the conclusion of a treaty of amity and commerce with Western countries also sparked off the virtual dawn of Japanese export industry. More and more people gathered to Yokohama from around Japan borrowing premises allocated by the feudal government, dreaming of making a fortune. It is thought to be just like the gold rush in the United States.
Jube Nakaiya was the first to venture into Yokohama from Gunma Prefecture. He opened a shop called Akagane Goten (copper palace) and acquired immense wealth as a raw silk trader. Zentaro Shimomura, who became the first mayor of Maebashi City, also worked very hard to sell raw silk.
The name of ”Maebashi” in Gunma Prefecture, which exported good-quality raw silk, became well known to London, the capital of the United Kingdom, and Lyon, a region producing silk textiles in France, as a production center of excellent raw silk. It is said that the best quality raw silk in Japan at this time was called”Maibashi” or” Mybash .”

●Technical innovations and significant advancement of silk reeling

As raw silk became a prominent export, the silk-reeling industry developed remarkably. At that time, improved manual silk reeling method called “Kairyo Zaguri” was developed in Gunma Prefecture. Trough this method, raw silk reeled by each farmer was assorted to standardize and re-reeled onto bigger reel (re-reeling reel) in cooperation. Union organizations were formed by silk-raising farmers who did not have much capital to implement this method. Those organizations improved quality of silk and expanded the production volume dramatically.
Meanwhile, technical innovations by the introduction of western-style machines were also promoted. Maebashi-han( a feudal clan) introduced Italian-style reeling machines for the first time in Japan, and a clan-operated silk mill was established in Year 3 of the Meiji Period (1870). In Year 5 of the Meiji Period (1872), Tomioka Silk Mill built as a government-operated model factory started its operation. It was a large factory equipped with French-style silk reeling machines.
Chotaro Hoshino who started silk business for the first time as a private citizen sent his younger brother Ryoichiro Arai to New York to export raw silk directly. Ryoichiro continued to live in the United States and worked energetically as a trader. (Haru, wife of Mr. Reischauer who was an ambassador to Japan, was a granddaughter of Royoichiro.)

●Silk railroad

The development of the silk-reeling industry had great impacts on the lifestyles of people living in Gunma Prefecture and the creation of cities.
Since raw silk was the most important export item to acquire foreign currency, to transport it rapidly and inexpensively in large volume, many railroads that could be called “silk railroad” connecting each area in Gunma Prefecture with Yokohama was developed and those are still used as major railroads (e.g. Takasaki-Line, Hachiko Line.
The Kozuke Railway invested by many silk-raising farmers was used to transport silkworm eggs and cocoons.

●Improvements in sericulture technology

Chogoro Takayama in Takayama Village, Midono-gun (present Fujioka City) started to teach sericulture technology at the beginning of the Meiji Period. In Year 16 of the Meiji Period (1883), he completed ”Seioniku,” which is a silkworm-rearing method featured both heating and ventilation, fusing ”Ondaniku (temperature-maintained rearing)” derived from the Tohoku region and ”Seiryoiku (ventilation-maintained rearing)” invented by Yahei Tajima in Shimamura (present Isesaki City).
Additionally, the Ondaniku-based”Ibushi-gai (smoking rearing)” invented by Konshuro and Ito Nagai in Hariyama Village, Tone Gun (present Katashina Village) was also accepted widely by people.
In particular, the Seioniku invented by Chogoro Takayama was supported in various places during the Meiji Period when the silk-reeling industry was promoted across Japan to support the increased demands for export, aiming for the reliable production of cocoons, and became the standard sericulture method of Japan.

●Promotion measures in Gunma Prefecture

Gunma Prefecture also offered exhibitions of excellent mulberry breeds, delivered mulberry plants to support improvements in mulberry farms, and established the Silkworm Disease Prevention Office.
Later, this office was renamed the Sericulture Regulation Office and controlled the distribution of cocoons etc. mainly for prevention of diseases of silkworm.

Heyday of cocoon production and raw silk export

In the Taisho Period, the economy in the United States developed further after World War I, and the demands for silk increased, which led Japanese silk-reeling industry to the golden age never seen before.
In Year 5 of the Showa Period (1930), the production volume of cocoons recorded 399,000 t, and the export volume of raw silk 581,000 bales, which was the largest production volume in Japanese history. This was the heyday of raw silk, and about 40% of Japanese farmers were involved in sericulture on the national average.
Particularly in Gunma, Nagano, and Yamanashi, 70% of the farmers were silk-raising farmers. The greatest event for sericulture at this time was the beginning of the practical use of “heterosis (hybrid vigor)” expressed by F1 (the first filial generation), which was achieved by the research of Dr. Kametaro Toyama, in 1914. This was a highly important finding among agricultural technologies in the world, ahead of the commercialization of F1 hybrid of corns in the United States.

Shrinking silk-reeling industry

Due to a severe aftermath of the Great Depression in 1929(Year 4 of the Showa Period), prices of raw silk and cocoons collapsed severely. Later, a remarkable development of rayon and other rayon silk industry in the United States and the invention of nylon by DuPont in the same country in 1938(Year 13 of the Showa Period) eroded the demands for raw silk in the field of socks.
In Year 16 of the Showa Period (1941), a silk-reeling industry control act was established to discontinue the export of raw silk and convert it into domestic consumption. Later, the United States froze its assets to Japan and broke off the economic exchanges, and Japan finally rushed into World War II. Sericulture in Gunma Prefecture at this time decreased greatly in eight years during and after the war (between Year 14 and 22 of the Showa Period), to 60% for mulberry farms and to 26% for cocoon production.

Postwar reconstruction and modern age

For the reconstruction of Japanese economy after defeated in Year 20 of the Showa Period (1945), it was necessary to import food. As a result, sericulture was encouraged again for the national task to acquire foreign currency. The Japanese government strived to improve and disseminate the technologies by establishing sericulture technology training centers in each county in Japan (12 places in Gunma Prefecture). The Korean War which broken out in the summer of 1950 (Year 25 of the Showa Period) stimulated a economic boom triggered by special procurements.
This increased the demands for raw silk as well as the prices of cocoons, and caused their deficiency. In Year 29 of the Showa Period (1954) when the production was continuing to increase, Gunma Prefecture produced 16,759-ton cocoons (about 17% of the production in Japan) and became the largest production center in Japan, and has kept the position to date.
With economic growth starting from the late 30’s of the Showa Period, domestic demands for silk increased further. Since raw silk was a liberalized item in foreign trade from the first, it started to be imported from China and Korea.
In addition, with the decline in demands for Kimonos in the Showa 40’s and the increase in the import of secondary silk products in the Showa 60’s, Japanese sericultural industry decreased rapidly, and now it is on the verge of extinction.

Social and cultural impacts

Japanese silk-reeling industry that was thriving from the end of the Edo Period until the Showa 40’s had great impacts on the lifestyles of people in terms of society and culture. As Roka Tokutomi, one of the greatest Japanese litterateurs, wrote a poem about the impression of Gunma Prefecture during the Meiji Period as ”sound of loom, smoke of silk reeling, sea of mulberry…,” silk-reeling industry was integrated into modern literature, too. When silkworm eggs were sold in Europe, knowledge of microscope as well as Christianity was brought into Japan, and the spirits of people of that time has been passed to present people.
Festivals, Kogai Jinja (sericulture shrine), and various events to pray for a good harvest of sericulture, such as”Harukoma” (Kawaba Village) and”Kaio No Mai (dance of silkworms)” (Maebashi City), still remain in various places in Gunma Prefecture.


◉Silk industry today◉
Sericulture

To play the video, browser that supports the video tag is required.The industry in which farmers raise silkworms (larvae of silkworm-moth) to make cocoons is called “sericultural industry.”

Related to this industry, there are also ”silkworm egg producers” who supply silkworm eggs, called Sanshu(Seeds of Silkworms), to silk-raising farmers and “mulberry plant suppliers” who supply young mulberry plants to create mulberry fields.
During the Meiji Period, farmers were able to raise silkworms only once a year in spring under natural conditions, but now they can raise them six times or more a year; in spring, summer, early fall, and late fall (end of fall, early winter).

Life cycle and morphology of silkworms

Silkworms are holometabolous insects which have four growth stages during their lifetime; egg, larva, pupa, and adult. A larva hatched from egg undergoes four moulting cycles in about 25 days and transforms into a Jukusan or a mature larva. It makes a cocoon by emitting filament for 2 to 3 days and transforms into a pupa in another 2 to 3 days, and then emerges as a moth in about 10 days.

  1. Egg laying of silkworm moths
    A silkworm moth lays about 500 silkworm eggs.
  2. Gisan , Kego (Newly hatched larvae)
    Newly hatched larvae, which have not eaten any food yet, are called Gisan(ant worms) or Kego (hairy worms) because they look like ants from their black body hair.
  3. Larva (5th instar)
    The body weight of the 5th-instar larva after has undergone four moults increases by about 10,000 times compared with a newly hatched larvae.
  4. Eiken (Cocooning)
    Silkworm’s spinning to make cocoons is called”cocooning.” They continue to emit a cocoon filament about 1,300-1,500 m long for 2 to 3 days. The thickness of a cocoon filament they emit is about one fourth of a human hair.
  5. Cocoons
    The weight of a cocoon of a silkworm which is raised in present-day is about 2.0 g.
Silk reeling

The industry which makes raw silk from cocoons and sell it is called ”silk-reeling industry.”
The”machine-reeling industry” which purchases good-quality cocoons to make high-quality raw silk used to manufacture raw silk mainly for export from the Meiji Period until the beginning of the Showa Period.

At present, the”Usui raw silk Agricultural Cooperative” organized by silk-raising farmers still runs a silk mill in Gunma Prefecture.

Major processes until raw silk is made from cocoons
  1. Cocoon drying
    Dry the cocoons and kill pupas by heating to keep them for a long time.
  2. Cocoon assorting
    Remove dirty cocoons not appropriate for the reeling of raw silk.
  3. Cocoon boiling
    Boil cocoons to make cocoon filaments easily disentangled.
  4. Reeling
    Twist cocoon filaments disentangled from several cocoons into a strand of raw silk and reel it onto a reel.
  5. Re-reeling
    Re-Reel the raw silk from a reel onto a bigger reel (re-reeling reel).
  6. Bundling
    A bundle of raw silk released from the re-reeling reel is called ”Kase (skein).” About 24 skeins are bundled and packed for shipment.
Textile

Raw silk is a stiff thread with a gluey substance called sericin remaining on the surface. Soft and glossy silk yarns are produced after removing this substance from the surface. 

This work is called”degumming.” The weaving method of silk textile differs depending on whether it is woven up after degumming or degummed after woven up.

Major processes until raw silk is made from cocoons
Process of degummed silk fabric (fiber or yarn dyed fabric)
【Raw silk】
Twining
Degumming/Dyeing
(Yarn scouring/dyeing)
Scoured yarn/Colored thread
Weaving
Finish
【Textile】
(plain/woven pattern)
Process of raw silk fabric
(piece-dyed fabric)
【Raw silk】
Twining
Weaving
Weaving
【white texture】
(cloth scouring)
Dyeing/Finish
【Textile】
(plain, printed pattern)

Twisted yarn
Threads made by aligning and twisting several filaments of raw silk.
Degummed yarn
Twisted yarn with sericin removed
Weaving
Makes textiles from threads using a weaving machine.
Degummed silk fabric
Textiles woven with threads degummed before woven (scoured yarns) are called ”degummed silk fabric.”