By Asuka Kaji / Yomiuri Shimbun Staff Writer KUMAGAYA, Saitama — A building that used to be a warehouse for silkworm cocoons at the Kumagaya plant of Katakura Industries Co., previously one of Japan’s largest yarn-making companies, is now the Katakura Silk Commemorative Museum in Kumagaya, Saitama Prefecture. The Tokyo-based company operated the plant until 1994.
Entering the warehouse at the south end of the grounds, I noticed a number of square-shaped spaces overhead. The cavities, with their base plates removed, used to be storage spaces for silkworm cocoons and were called “hachinosu soko,” meaning beehive warehouse.
About 12 days after silkworms become pupae in their cocoons, they emerge to become moths.
To prevent the worms from making holes in the cocoons or tainting the insides if they died, the cocoons were dried with heat produced by steam immediately after being shipped in from producers.
To equalize moisture levels inside the cocoons after they had been dried, a total of 1,200 kilograms of cocoons were poured from the ceiling into one of the square spaces, and stored there for about a month.
This storage method had the advantage of cocoons being able to be stored separately according to when they arrived at the plant. It also gave protection from damage by mice or harmful insects because the storage spaces do not touch the floor.
Katakura Industries began making silk yarn using a device called a zaguri to reel silk by hand in Okaya, Nagano Prefecture, in 1873. Five years later, the company introduced Western-style machines and established Japan’s first yarn-making factory.
To promote streamlining through technological innovation, the company provided a financial subsidy to inventor Naosaburo Minorikawa to develop a silk-reeling machine.
Minorikawa knew through his own studies that if the thread is reeled too fast, the fibers break off or other problems occur, and thus the quality of the raw silk deteriorates.
He made repeated improvements to a model and thus developed the Minorikawa multi-row reeling machine. Though the machine ran at a slow speed, an individual worker became able to reel 20 rows of raw silk at once with the machine, compared with about four using the conventional method.
The quality of products improved remarkably and were highly praised in the United States, an export destination for raw silk products.
The company continued to develop and improve its factory machines and eventually realized fully automated operations at its factories. Thus mass production became possible.
In 1939, the company merged with the Tomioka Silk Mill in Gunma Prefecture. Up to 62 factories were in operation in the peak years to deliver raw silk all over the world.
However, Japan’s silk industry gradually waned. The Tomioka Silk Mill discontinued operations in 1987.
Management at the time preserved the buildings and machines of the Tomioka mill to protect this plant that symbolized Japan’s modernization. They vowed not to sell, lend or demolish it.
Later, the company donated the silk mill to the city government of Tomioka, which led to its designation as a World Heritage site in 2014.
Isao Suzuki, 63, director of the museum, said: “When the [Tomioka] plant closed, I heard that all the workers polished the machines. This museum is full of the pride of manufacturers in the silk industry.”