Visit Nirayama Iron Furnaces as a World Heritage

Japanese first challenge of modern iron making♣

♣  For the beginning

NRF- Illust x01.JPG        Recently, I visited the Reverberatory Furnaces in Nirayama, Izu, Shizuoka area. This historic site is one of the Western style iron melting furnaces which NRF- Furnace x04.JPGhave built for producing iron cannon in the end of the Edo period. This type of furnaces was constructed in the many places such as Saga, Kagoshima, Yamaguchi for the strengthening naval capacity under the threat of foreign fleet at that time. But the remaining observable sites were only in Hagi, Yamaguchi and this Nirayama furnace only today among them.

NRF- Guide C illust x02.JPG     Particularly, Nirayama’s furnace is unique because it has shown the real figure of practically operated iron making process at the time of construction. For this reason, it was designated as the historic treasure of the country and registered as a Unesco’s “World Cultural Heritage” in 2015.

Meantime, the “Guidance Center” of the NRF- Illust x05.JPGNirayama Reverberatory Furnaces (NRF) was opened at the end of 2016. The facility is purpose to show up its historic site by exhibiting memorial goods and materials, information panels on the furnaces and many others. Now many visitors became visiting there to appreciate NRF now as a tourism target.

  See: Home page NRF:

The furnaces is said to be constructed by the limited knowledge about Western iron NRF- Internal structure x02.JPGmaking system under the isolation policy of Edo Shogunate in 19c. So the work of Japanese engineers at that time had to work relying only on the Dutch engineering books. The challenges had been NRF- Cannon x02.JPGexceedingly severe, but after the laboratory work it led to attain the goal by genuinely Japanese engineers’ initiatives only even though accompanying many shortages in the operation. After the Meiji era, the reverberatory furnace technology itself had become an old one. But, the experience and knowledge which engineers cultivated in the construction has applied much in the subsequent advancement of the Japanese steel industry. These must have been a precious and seldom experience for Japanese in this meaning.

The following is an impression of the visits of the NRF and some additional info on it.


 ♣  NRF as a historical monument

NRF is located Narutaki District of Izunokuni City, about a 20 minute walk from Izu NRF- Illust x04.JPGNagaoka Station. The site is about 3000 square meters in size, with two tower-like buildings about 16 meter’s height. As the NRF- Illust x03.JPGfoundation of the NRF the furnace’s combustion port and iron melting stand were installed. The furnaces are consisted of four twin melting units linking each other by L-shape. The interior parts were covered by heat-resisted brick arch, and it is said that the furnace was covered by the white plaster in the beginning. Today the exterior wall was hardened by the steel latticed frame for the protection of the building.

NRF- CG x04.JPG        At the high time of operation, it is said that the NRF had many workshops in compound, such as casting shop of gun barrel, drilling cabin of barrel with water wheel, blacksmith NRF- CG x05.JPGhuts, and coke piling warehouses beside the furnace facility itself. Then the entire site was believed to be something looking like a huge factory.

The most of the barrels produced there had been moved to the Odaiba (tiny fort land of harbor) off Shinagawa area in Edo bay in order to ward off the foreign naval fleets. This situation is well illustrated in the exhibits in the “Guidance Center.”

♣  Exhibitions of NRF

NRF- Illust x02.JPG       This “NRF Guidance Center” was set up to introduce the structure of furnace, its historical significance and technical background of the NRF just after receiving the designation of ” World Cultural Heritage”  So NRF- Guide Center look x02.JPGIt is quite effective to visit first this center for learning about NRF and before actually visit the furnace.

The center has a video hall and an exhibition room. In the former space, the large screen is showing the
NRF- material x03.JPGconstruction process of the NRF and the iron melting and casting scenes by CG pictures, and in the latter
exhibition room, the chronologies, photographs and illustrations, memorial goods leading construction of the NRF are displayed, besides many bricks, molten iron blocks used for the construction and so on.

CG Image is available by:

♣  What’s Reverberatory Furnace and its Technology

My initial interest was “what is all aboutNRF- Furnace x01.JPG“Reverberatory Furnace” (NR) and where it has come originally. The NRF- Internal structure x01.JPGGuidance Center has explained it in detail. According NRF- Furnace x02.JPGto the
explanation, the iron making using a NR method had originally developed in England in the 18th century and mainly used for the cannon manufacturing. And it is said that the technology was adopted in Europe in the 19th century as a quite common iron making method.
NRF- Book x01.JPG  In Japan, it was introduced through the Ran Kagaku (Dutch engineering books).  And under the military threats, such as visiting Admiral Perry’s fleets in the Edo bay in the isolation NRF- Perry x01.JPGpolicy, the Edo government was obsessed to explore the new method of building iron arms like cannons to avoid the serious foreign threat. The construction of furnace was made based on the text book of “Casting method of the Royal iron cannon NRF- Rangaku x01.JPGmanufacturing place” written by Hugenenin, a Dutch engineer. And Japanese engineers translated this book and applied it in the field with some Japanese modification.
In Japan, since the ancient times, people had been manufacturing iron by so called “Tatara J Sword 18 Tatara 01steel making.” This method was exclusively used for iron making for long time until the middle of the Edo period. However, this manufacturing technology was suitable only for small iron products such as swords and agricultural tools, but it couldn’t apply well to the large casting production like cannon.

In the meantime, the structure of this RF basically formed NRF- Furnace x05.JPGof the combustion chamber and the iron melting chamber in the separate way. So this production system generates, high temperature by combustion of fuels in the chamber, creates a rising thermal air by high chimney, reflects it on the inner wall, and could melt a large amount of iron lump subsequently. This is said to be the best technique for casting of iron cannons at that time.

But after that, this technology gradually became an old fashioned, and large blast NRF- Illust x10.JPGfurnace using coke, converter method, hearth furnace method were continuously invented, then the main iron-making NRF- Illust x07.JPGtechnology have been shifting to the new manufacturing systems. But in the end of the Tokugawa Edo period, this RF was believed to be the latest technology; so the Japanese engineers had to rely on this method.
For that reason, the acquisition of the technology of the latest Western furnace and the actual operation had to inevitably face exceeding difficulties at that time of engineering capacity. Additionally, it was necessary to drill a hole to the molten cast to make real gun barrels. It was a great technical challenge to make hole in the hard iron lump in the Edo period because a strong power source wasn’t available beside water power. The evidence of these struggles is well left in the ruins of the NRF there.

Anyway, with the exhibits and related documents, we could see how the RF has been NRF- Illust x11.JPGNRF- Saga x01.JPGconstructed in history. It was Saga’s Nabeshima clan that built the “RF” for the first time in Japan and succeed in casting iron. It is said that Nabeshima Naomasa, a lord of the Saga, intended to build a RF reflector in Tsukuji for building the sea defense forts in the late Edo period by mobilizing Rangaku (Dutch Study) engineers and started the cannon manufacturing project there. With the successful prospect of this project, the construction of the Satsuma clan’s “Shuseikan” project, the Choshu-Hagi, also began construction of the RF too, and the construction movements of similar furnace started in many places in Japan.

♣   The Construction of NRF and Egawa Hidetasu

NRF- Egawa x02Amid such circumstances, the Egawa Hidetatsu, who had many colleagues of Rangaku people, made technology proposal to the Shogunate on the defense policy of the Edo bay to build of “Odaiba” (small fort land) and NRF- Odaiba x01.JPGthe construction of the NRF, after the time of harboring arrival of the Perry
fleet, even it was somewhat delayed from the aggressive initiatives of the other southwestern Japan’s major clans.

       Egawa Hidetatsu, who was familiar with Takashima Shuhan who was an artillery advisor to Shogunate at that time, had referred to Rangaku book
NRF- Shimoda x02.JPGand dispatched the trusted subordinate Hatta Heisuke to Saga area where had been advancing the furnace operation. Hatta was believed to learn much about furnace technology in Saga, and returned to Nirayama to bring the results. Then Egawa first started building of the NRF by his initiatives based on his information after the Edo’s permissions.

Initially, he planned to construct it at the Shimoda area, which was close to the production of heat-resistant bricks, but the location was suddenly changed to the Izu Nirayama area, because a peculiar incident touching to the military confidentiality had occurred in the site. So it took five months to complete this first reactor there

However, there happened another tragedy to Hidetatsu, who was a leading figure in construction, died suddenly just before the completion. But the building project itself was NRF- Cannon x01.JPGhanded over to his son, and finally could success to build a small 18 pound iron cannon by this furnace after the painfully hard work. NRF- Guide C illust x01.JPGEven that, the quality of molten iron was said to be quite poor and experienced many failures in the process. Additionally,  the Ansei large earthquake struck the area in 1855, and the furnace was severely damaged.

Then, in the subsequent years, the seven times of melting works had been tried, but it NRF- Illust x09.JPGresulted in the end to complete only two units of iron cannons.       We could imagine how difficult it was to introduce new technology at that time with lack of comprehensive scientific knowledge on the modern iron-making. Many trial and error and technical modifications had been made in this manufacturing process, but the main cause was said to be due to the poor NRF- Egawa x03.JPGquality of material iron (sand iron pig), irregularity of melting process, skill of works, furnace architecture, and basically the short of experience.

However, technological challenges, ingenuity, trial application to the new methods, and other efforts in the process, all these endeavors of are evaluated as being embodied in this NRF’ site. When looking around throughout of Japan, the RF was tried to build in the around eleven locations at the late Edo period. Among them, it is the NRF only in the Izu region where the appearance of furnace completely remains as it was. So its historical value is quite high. Because of his Yahata- Furnas x01.JPGcontribution to the NRF, a statue of Egawa was built by the local people in the premises now.

Yahata- Noro x01.JPG       It is no doubt that the challenging spirit and experience of trial and error of iron
making have become the foundation of the Japanese steel making industry in the Meiji industrial modernization afterwards. Especially, we could admire the wisdom of the Japanese engineers that they tried to follow the new technology only upon the Dutch technical books, and made up real RF without direct guidance or contribution of Western technicians. This was strongly felt when observing the reflector in the field. It seems reasonable to be designated as “World Cultural Heritage”.

NRF- Egawa x06.JPG    (The Egawa’s old residence remains at the “Egawa memorial museum” in Nirayama. The museum holds a lot of records and memorials when he had lived, such as records of the time of NRF building and, traces of his activities as an engineer, a doctor, and architect. They were well kept until now. I’d like introduce this museum exhibition later on the other scripts.)

♣  My impression after the visit NRF

NRF- Illust x06.JPG       It was a great experience that we could observe the NRF site, and acknowledged about the background history of it and glimpsed the NRF- Egawa x01.JPGrecord of technical challenge at the end of the Edo period. After the defense function of Edo government was over, the NRF was transferred to the Ministry of Army of Meiji Japan (1873), but it was left being neglected for long time. But in 1908, the restoration of NRF movement began by the local people on the 50th anniversary of the fall of Egawa who had greatly contributed to the building of NRF.

And it was designated as a national historic site in 1922. However, the preservation crisis of NRF had occurred in 1930 by the Izu great Earthquake and the
NRF- Volunteer guide x01upper part of the NR had become collapsed. After the Pacific War, the demand to the restoration of NRF emerged again and strengthened further by the movement among the local people and government. With that initiative the major recovery project NRF- Fuji x01.JPGstarted in 1957 which was included the architectural works putting steel frame for reinforcement, clearing the premises, and so on. The current outlook of NRF was basically formed at this time.       Many volunteers are participating in the guide actively at the NRF site now for visitors.
That made us felt a sincere proud of local people and NRF- Sakura x02.JPGtheir hot enthusiasm to the historical monument of NRF. Local people sometimes boast that NRF visitors could look over two major World Heritage sites at once there. They say the one is NRF and another is Mt. Fuji. Certainly, as looking over from the hill side of the compound, Mt. Fuji, which is showing beautiful slope wearing snow at its top, can be clearly observed over the furnace tower surrounded by fertile greens.  I have ended my visit NRF while imaging the scenery NRF in the time of full bloom Sakura in the spring season with the good combination of Mt. Fuji over the hill.



  • 「韮山反射炉」構造と歴史
  • 韮山反射炉案内パンフレット Japanese & English)
  • 「韮山反射炉の解説」 堀内永人 (文盛堂)
  • 「たたらから近代製鉄へ」岡田康吉編 (平凡社)
  • 「金属の文化史」 黑岩俊郎編 (アグネ)
カテゴリー: Museum, Uncategorized タグ: パーマリンク