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Yakinaoshi (re-temper)

A report by Kurihara Hikosaburo Akihide
Translated material provided by


Preface : This is a fascinating article about Kurihara Akihide's work and research in the field of re-tempering blades that lost their hamon due to fire. This process is called "saiha". From the stand point of those who study Nihonto, a saiha blade has little value because it no longer can be considered representative of the craftsman who originally made it. As collectors, we should certainly stay away from blades that have been re-tempered. However, it is interesting to note that from the stand point of a blade's functional purpose, a sword can be made useful again by this process. It is also enlightening to learn that the work of certain smiths preformed with a high degree of excellence after saiha. I think this speaks highly of both Akihide and the smiths that made these blades.

Translated material provided by

Kunihara Akihide was an influential gendai smith.  He was born in Sano of Tochigi prefecture in 1879 and was also known as Kurihara Hikosaburo. He learned sword making under Inagaki Masanori 稲垣将應 the third and Horii Taneaki 堀井胤明. Akihide’s father established the Nihon-to Tanren Denshusho at Akasaka in Tokyo around Meiji 25th or 26th.  Akihide taught many Gendai smiths including Amada Akitsugu 天田昭次, Akimoto Akitomo 秋元昭友 and Miyairi Akihira 宮入昭平. Akihide also went into politics as a member of the House of Representatives for Tochigi Prefecture. He passed away in 1954 at the age of 76.  Japan started its aggression towards Korea and China in the Meiji era.  Akihide’s older brother was in the Japanese Calvary stationed in Manchuria (northeast China bordering Russia).  He needed a sword that could be used on horseback and that would not break in the cold climate of northeast China.  He wanted the blade to be of narrow mihaba, long and proper sori.  Akihide’s father went through the family collection of fifty to sixty swords but could not find one that would fit the criteria requested by his son.


In the neighboring village lived a sword smith Inagaki Masanori.  He was the third generation on his line.  The shodai was highly appraised in a Shinto book.  This third generation Masanori was working for the Akimoto family until the Bakumatsu period. Then, he joined the volunteer militants of Takeda in Echizen and made swords for the troops.  He survived the battlefields and came back to his home village around Meiji.  He made special order blades, utility knives and other tools as a way of living.  Akihide’s father invited Masanori over to make swords with the Mokusa-den method so that the blades they made would function well in cold climate.  That was February, Meiji 26th when Akihide was around fourteen or fifteen years old.


There were the 3rd Masanori, the 4th generation and the younger brother of the 3rd all working together with Akihide’s father.  The younger brother of the 3rd was pretty skillful in horimono.  The sword price at that time was very low.  (Swords were totally outlawed in Meiji 9th.)  With three silver dollars one could buy a Suishinshi 水心子, Naotane 直胤, Nobuhide 信秀, or a Kiyondo 清人.  Other blades like Osaka Shinto 大坂新刀 Jo saku with mounts, Oei Bizen 応永備前 Jo saku and Shinto Jo Jo saku were all around ten to fifteen silver dollars.  To sell a newly made sword for ten silver dollars or more was a miracle.


Akihide’s father was interested in sword making.  He was afraid it was going to become extinct soon.  In order to preserve this craft for the future of the nation, he established the Denshu Sho.  Akihide also believed the important purpose of the Denshu Sho and worked hard to develop it further.  **The Denshu Sho became a very important institution in producing a new generation of sword smiths active around Showa and contributed greatly to the revival of Nihonto after the Meiji sword abolition laws.  


When the Japanese Army 14th regiment departed for Manchuria, many of the troops carried swords made by Akihide because this regiment consisted of people from Akihide’s electoral areas.  Those blades performed well in Manchuria.  Around Showa 3rd, the Denshu Sho was moved to the old residence of Katsu Kaishyou in Akasaka, Tokyo and the official name of “Nihonto Tanren Denshu Sho” was given.   **Katsu Kaishyou, one of the three Shyou, was another important political figure at that time.


The president of Dai Nihon Butokukai, army general Hongou Fusatarou 本郷房太郎, was another strong supporter of Akihide and the Denshu Sho.  He stressed the importance and necessity of Yakinaoshi to Akihide several times.  Akihide took the order and started working on it.  Yakinaoshi is re-temper also known as sai-ha.  If a blade was in fire it could lose its hamon and render it useless.  The purpose of Yakinaoshi was to give those blades a second chance by giving them a new hamon through re-tempering.  These required experiments of trial and error and not every smith could develop the skills to do it properly. 


Akihide did not want to report his results when the test was not completed.  The first critical thing for Yakinaoshi was to select the right blade for the job.  The blade should not have any ha-giri and be in healthy condition.  The main reason to do Yakinaoshi was to make the blade useable not for re-sale therefore, it should be stated accordingly to prevent the blade being sold as having genuine hamon.  


There was a big earthquake and fire in Taisho 12th.  Uchida Ryouhei 内田良平 and Akihide each had a couple of dozens blades that got ruined in the fire at the Tokyo Arts Club.  Itou san 伊藤恒策, a friend of Akihide, also had lost about thirty to forty blades at the same club.  Those were hard-to-find top quality Saijo-saku blades.  It would be pitiful to just toss them away. Therefore Akihide bought more than a thousand ruined blades from this fire and used them to practice his Yakinaoshi skills.  There were very good blades within those and it was important to give them new life through Yakinaoshi.


In the fall of Taisho 13th, Akihide felt confident that he could do Yakinaoshi successfully.  He called the first meeting to evaluate blades re-tempered by him.  Among the people invited were General Hongou Fusatarou 本郷房太郎, General Nakamura 中村雄次郎, Toyama Mitsuru 頭山満, Uchida Ryouhei 内田良平, Osaki Masayoshi 大崎正吉, swordsman Honma Saburo 本間三郎, swordsman Moue 毛柄柳太郎, Akasaka area politicians and people who were interested in this.  The main person performing the test cuts was the swordsman Moue san.


There were eight swords tested. 

1)   Fuyuhiro saku, 冬廣作 Nagasa 2 shaku 3 sun 5 bu, very narrow mihaba, bo-bi, tachi sugata,

2)   Nanki Shigekuni saku, 南紀重国作 Nagasa 2 shaku 5 sun 5 bu, wide mihaba,

3)   Sashu Mondo no Sho Masakiyo saku, 薩州主水正正清作Nagasa 2 shaku 3 sun 5 bu, wide mihaba,

4)   Bishu Osafune ju, Oei 23 year ura mei, 応永長船刀 2 shaku 2 sun 8 bu, narrow mihaba, it didn’t retain the smith’s name,

5)   Shodai Kanemoto, 初代兼元 2 shaku 3 sun 3 bu, relatively narrow mihaba,

6)   Hosogawa Masayoshi, 細川正義 2 shaku 7 sun 5 bu, wide mihaba magnificent sword,

7)   Mumei, Yamato-mono 2 shaku 3 sun 2 bu, 大和物inheritance of the Mito family with an old origami attributed it to Kaneuji,

8)   Inoue Shinkai, 井上真改 Nagasa 2 shaku 3 sun 8 bu, Soshu den style, great Saijo saku, it’s said that this sword was the Shinkai among all the Shinkai blades. 


The test results are in the following.

1) Fuyuhiro katana

Akihide and Moue both tested this sword to on straw wrapped bamboo but they could not make a single complete cut.  Akihide then, used it to cut dry wood on the cutting block with all his power.  The blade broke into three pieces.  The kissaki and monouchi part flew over the heads of people standing by.  The mid-section of the blade felt in front of the cutting block.  Akihide was holding the remaining part about one shaku in his hands.  When examining the broken ends of the sword, it was like solid iron. One could not see the shintetsu, not enough toughness.


2) Nanki Shigekuni

This was the best cutter after retemper, there was a sword dealer Kikuji also brought a Shigekuni to compare and he was pleased to see this one came out so well after its retempering.


Bamboo sticks with a circumference of 7 sun were placed into the ground vertically with 7 to 8 shaku above ground.  Akihide used the Shigekuni to cut the bamboo at an angle three times and Moue did it twice, all complete cuts.  Straw was used to wrap two flagpoles together as the next object to cut.  Moue san cut it four times and Akihide cut it twice and all cuts went through completely.  Kikuji’s Shigekuni was also used to test cut.  There was no difference in the performance of these two blades even one was retempered.


Uchida sensei also expressed the same opinion about the importance of Yakinaoshi and Akihide felt pleased that his study and test of this topic had successful results.


3) Mondo no Sho Masakiyo

This was similar to Shigekuni, Uchida sensei felt comfortable about its performance.  Straw wrapped bamboo was the first test object.  Moue san demonstrated the supreme cutting ability of the blade without much effort.  The sword was then used to hit a plum wood ken hanging in the mid-air.  It was proven to have excellent flexibility.  **Like it was made of spring steel, so to speak.


4) Oei Osafune katana

Akihide spent a lot time and effort to study its sugata and construction before doing the Yakinaoshi because the cutting ability could be influenced greatly by these factors.  The sugata of the blade was not strong.  Akihide did not have high expectations.  Straw wrapped bamboo was used as the test object.  Moue san made two cuts on the object and the blade bent towards ha upon the first try.  The blade was then used to hit a hanging plum wood ken and it was bent like a lobster tail.  The sides of the blade were broken exposing the shintetsu that was almost homogeneous and the kawa-gane was paper-thin. 


**Thin layer of kawa-gane alone was not a problem.  Hizento was made with that but they were almost all superior cutters.  It’s the quality of the shintetsu and kawa-gane made the difference here.    


5) Shodai Kanemoto

This blade was in a very healthy condition and should produce good results.  Shodai’s irregular sanbonsuji hamon was reproduced through Yakinaoshi.  Akihide believed it would have good results from the tests.  


The results indicated it was the best.  Test objects were two straw wrapped bamboo objects placed on a wood cutting block made of Chinese juniper.  The blade went through the objects and into the wood block 7 bu deep.  The mid-section of a pig’s bone was also used and it was cut into two in one stroke.  All the people there were excited by the scene and applauding at the great performance.


At that time, the Count Senda family also provided two Kanemoto blades and asked them to be tested.  These were a shodai Kanemoto wakizashi of 1 shaku 6 sun and a ni-dai Kanemoto daito of wide mihaba and 2 shaku 4 sun 8 bu nagasa.  Moue san tested these two and the results were excellent.  The re-tempered blade was then tested with the hanging plum wood ken method. This caused a slight bend in the blade.      


6) Hosogawa Masayoshi

Akihide expected this blade to be performed well.  Moue san tested it and the results were excellent.


7) Mumei Yamato-mono (attributed to Kaneuji)

Akihide purchased this blade from the Mito family with a record breaking high price for mumei blades.  He liked it very much and stored it at the Tokyo Arts Club but got ruined by the fire.  Heii Chiba gave it an excellent polishing after Yakinaoshi.  Because the cutting test most likely would spoil the polish Uchida sensei was commenting whether it was correct or not to have it polished.  The blade’s superior cutting ability was demonstrated clearly in the cutting tests.  


Honma Saburo sensei, a trained swordsman, used it to make a complete cut of the straw wrapped bamboo without much effort.  The swordsman Nakajima from the Black Dragon Society was the next tester.  He and Akihide both performed cuts on the straw wrapped bamboo with excellent results.  Uchida sensei then requested to test the blade with a telephone book of 1 sun 5 bu thick.  Artillery captain Omura performed the test with excellent results.    


8) Inoue Shinkai

Itou san paid a very high price in purchasing this sword.  Akihide liked it very much and used thirteen hundred silver dollars and two other blades as payment to get it from Itou san.  This blade had horimono of dragon inside the hi and bonji.  It was a very famous sword among collectors at that time.  When it was damaged in the fire, Uchida sensei mentioned to Akihide that it should be Yakinaoshi.  Akihide spent a lot effort doing it.

Honma Saburo sensei and Nakajima san both tested the Shinkai on straw wrapped bamboo with excellent results.  Akihide also tested it by cutting 7 sun thick bamboo placed into the ground with about 3-4 shaku above.  Five cuts were performed and they were all complete cuts.  Hitting the hanging plum wood ken was the final test and it resulted in a slight bend. 


Above was the result of the first test.  Since then, there had been ten tests with five to seven blades at each time.  Honma Saburo sensei, Nakayama Hakudo sensei 中山博道, Uchida Ryouhei sensei, Moue san and other experts were all involved with these tests and the results were excellent.  Akihide believed Yakinaoshi was an important topic for the nation and the different approaches towards koto and shinto should be studied further.  Akihide also made a pledge to continue the test for the next ten years and to provide more information to share with people interested.                 


**Dai Nihon Butokukai was established in Meiji 28th, 1895 AD in Kyoto.  The main purpose was to promote the practice of martial arts and the spirit of martial arts.  Prince Komatsu no Miya 小松宮 was the first president.



Rekishi Kouron, January, Showa 10th, 1935