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About the buildings

Method of construction of the main buildings
The buildings of Tomioka Silk Mill built at the beginning of its establishment were designed by Auguste Bastien, a French man who also participated in the construction of Yokosuka Ironworks, and were constructed by Japanese carpenters and craftsmen. The main buildings were constructed by integrating Japanese and European technologies, using a European technique of timber-frame and brick construction that piles a wall of bricks against wooden frames and incorporating Japanese tiles on the roofs. Timber-frame and brick construction was originally introduced at Yokosuka Ironworks and was applied to Tomioka Silk Mill.  The major materials of the buildings are stones, wood, bricks, and tiles, and iron-framed windows, and the iron door hinges were imported from France. The main timber were mostly sourced from government forests, with cedar wood from Mt. Myogi and pine wood from Agatsuma, and other smaller timber were collected from local mountain forests. Stones for the foundation were quarried from Mt. Renseki (present Kanra town).  French technicians taught Japanese tile craftsmen how to create bricks, and it was baked along with tiles in the kiln built to the east of Sasamori Inari Shrine in the town of Fukushima (present Kanra, Fukushima). Main people in the construction were tile craftsmen of Fukaya in Saitama, including Naojiro Nirazuka. The bricks were laid with plasters instead of mortar. The plaster was made with lime from Aokura and Kuriyama in the town of Shimonita. It is laid in French bond, or Flemish bond, a style mainly used in Flanders, northern France.
People involved in the construction of the Tomioka Silk Mill
Junchu Odaka
He was a government official committed in the establishment of Tomioka Silk Mill along with Paul Brunat (French director). He saw from the selection of construction site to arrangement of construction material. He became the first head manager of Tomioka Silk Mill and employed his daughter Yuu as the first mill hand.
Naojiro Nirazuka
He was in charge of material procurement for the building of Tomioka Silk Mill. He collected tile craftsmen from present Fukaya city since there were no brick craftsmen around Tomioka, and committed himself to brick construction under the direction of Brunat.
Francois Paul Brunat
Brunat was a silk inspector in a trading firm at Yokohama, but he was commissioned to direct the building of Tomioka Silk Mill by the Meiji government who saw the potential in his knowledge in the silk industry. He submitted an Expectation Document (mill construction and management plans) to the government in 1870 and tied a temporary contract. He also participated in the selection of construction site, and he signed an official employment contract in November of that year. He employed French technicians necessary to the mill, and ordered European machinery that was altered to suit the smaller frames of the Japanese.
Edmond Auguste Bastien
He was a French technician that designed the main buildings. He completed the blueprints in December 1870 (said to be just 50 days after the request from Brunat). It is said to have been possible since he referred to the design of Yokohama Ironworks where Bastien had worked as a ship mechanic and a designer before becoming involved with the Tomioka Silk Mill.
Designation as Cultural Properties
After ending operation in 1987, the site of Tomioka Silk Mill became a National Historical Site in July 2005, and its original buildings became National Important Cultural Properties in July 2006. Silk-Reeling Plant, East Cocoon Warehouse, and West Cocoon Warehouse were designated as National Treasures in December 2014 out of the National Important Cultural Properties. Tomioka City currently owns and maintains the mill complex.
Historic Site
Designated area : 55,391.42 square meters
Tomioka Silk Mill main buildings
①Silk-reeling plant (National Treasure)
This was the building where silk was reeled off of cocoons. It is an enormous factory with a length of about 140 meters that housed 300 metal silk-reeling machines introduced from France at its establishment. It was the world’s largest machinery silk-reeling factory. A large space without pillars at the center of the building was made possible through the truss structure in the roof framework.

②East Cocoon Warehouse (National Treasure)
This was the building that mainly stored cocoons. Dried cocoons were stored in the second floor, and the first floor was used as an office and workspace. It is an enormous cocoon warehouse approximately 104 meters.

③West Cocoon Warehouse (National Treasure)
Like the East Cocoon Warehouse, it stored cocoons in the second floor. The size and structure is basically identical to the East Cocoon Warehouse, but there is no wall on the eastern side because the eastern side of the northern half of the first floor was used to store coal for the steam engine during operation under government management. The brick wall seen today was built around 1981.

④Director's house (Important Cultural Property)
This was the house where Paul Brunat, a Frenchman employed as the director, lived with his family. It has a colonial style for good ventilation with high floors, veranda around the building, and shutters on the windows. After Brunat had left, it was used as a dormitory for female workers and a space for education and leisure.

⑤Steam boilet plant (Important Cultural Property)
This was where the boiler and the steam engine were placed. Later, it was renovated and extended and was used as a steam boiler plant and for cocoon selection.

⑥Inspector's house (Important Cultural Property)
This was the house of a Frenchman who had been in charge of inspecting the silk. Like the Director’s House, it has a colonial style with good ventilation. Later it was repaired and is currently used as an office. In the second floor, there is the VIP room where government officials and members of the Imperial Family stayed on their visit.

⑦Dormitory for French female instructors (Important Cultural Property)
This was the house of French female instructors employed to teach Silk-reeling technique for machinery silk-reeling to Japanese female workers. Like the Director’s House, it has a colonial style with good ventilation. Later, it was repaired and used as a cafeteria and conference rooms.

⑧Iron water tank (Important Cultural Property)
This was an enormous water tank built around 1875 that stored the water necessary for production of silk. Rivet, a shipbuilding technique used for warships, was utilized to build this iron water tank, and it can hold around 400 tons of water.

⑨Brick drain (Important Cultural Property)
This was a drain built at the time of establishment and carried drainage from the Silk-reeling Plant and rainwater from the buildings’ roofs to the Kabura River that flows to the south of Tomioka Silk Mill. It remains in almost perfect condition today and is still used as a rainwater drainage.