Page Last Updated: Wednesday, 04 November 2015 13:35 EDT, 1964, 2003, 2007, 2008, 2010

Retempering a Blade

by Dean S. Hartley, Jr.


On 15 July I was invited by Mr. Fujimura to witness the retempering of a tanto which had lost its boshi through extensive repolishing. The invitation grew out of his knowledge of my desire to learn as much as possible concerning every aspect of the making, tempering, and general understanding of the Japanese sword. The immediate trigger was a conversation concerning two blades which had been badly burned in the firestorm at Hiroshima, and were of such historical value as to justify their retempering. Of these two, which he showed me, one was a famous Muramasa blade, and the other by a very famous smith whose name I do not now recall.

With Frank Ikeda acting as interpreter, Mr. Fujimura explained the general condition of the blades prior to their retempering, and showed us the results. Although not finally polished, it was obvious that the style and technique of Muramasa, as well as the shape of the hamon, had been closely followed and duplicated in that particular blade. The same was true of the other blade. I expressed a great interest in the procedures followed, and at that time (9th or 10th July) he extended his invitation to see the retempering of a Sukesada tanto which we had previously examined. He assured me that barring the first step, which I will describe later, the entire procedure was completely analogous to the initial tempering of a newly forged blade.

During this whole lengthy conversation, Frank Ikeda was a most deeply appreciated participant, since my Japanese is still limited to greetings and simple requests and my understanding (while growing daily) is only of a general nature. I also met his brother, Motonari, who has volunteered to assist me in various relations with officials here in Iwakuni. Motonari-San is the number three man in the large Iwakuni Post Office.

On 15 July, surprisingly accompanied by the First Marine Air Wing Chief of Staff (who was a metallurgist by training), we boarded my Toyopet automobile and headed for West Iwakuni (called the Kintai area after the famous multiple-arched Kintai bridge).

Mr. Fujimura was waiting, with his forge and tools all set up, and after a short Kirin beer, we got on with it. First he examined the blade carefully, determining the shape of the remaining hamon, checking photographs of Sukesada tanto of the same period, and pointing out that faulty polishing had also modified the blade from its proper shape:


dotted lines for original shape

the takinoku-zori shape is exaggerated, but was actually present. He repolished the tip sufficiently to assure himself that the boshi was in fact gone, and proceeded to the next step, which was a light grinding to remove all evidence of rust, pitting, etc. which was present on the blade -- and to commence the reshaping of the blade. I noticed that he still left some of the negative curvature on the mune, a fact I will cover later.

Having thoroughly cleaned and shaped the blade to his satisfaction, he then laid the blade aside and devoted himself to the careful creation of a bed of hot coals in his forge, using pine charcoal. When he had the desired heat and amount of coals, he adjusted the blower to provide a constant temperature, and using his tongs, placed the entire blade in the coals, leaving it until it was cherry red. He then let it cool in the air (not laying it down until the color had disappeared), and then left it in the dying coals.

While this process of annealing the blade and washing out the previous tempering was going on, the Chief and I were showed some of Mr. Fujimura's personal collection, and had another small beer. After about thirty minutes, Mr. Fujimura re-cleaned the blade, again removing all foreign matter and reshaping slightly. He then cut out a soft aluminum template in the basic shape of the desired hamon, and we took all of these to his upper floor open-air workshop.

There he uncovered a small crock of his tempering compound, kept in a moist condition of the consistency and color of black clay, with a significant inclusion of particles the size and consistency of medium fine sand. His first step here was to remove a small portion, about the size of the first joint of the thumb, place it on a glass mixing "board," and thin it to the consistency of "slip" with water. This he then spread evenly over the entire portion of the blade proper, leaving the blade in a special rack (into which the nakago was inserted) to dry. Drying was quite rapid, resulting in a dark gray-black coating. The template, which was in the shape of a suguha hamon, was laid along the edge and a coating of the compound in its original consistency was then applied over the entire portion of the blade which was not covered by the template (except the mune, which I will describe later). The thickness was about one-quarter to three-eighths of an inch. Again the drying was fairly rapid, and the templates were of course removed.

When nearly dry, using a bamboo sliver, Mr. Fujimura picked up droplets of the thinned "slip" and applied them against the thicker coating to form "ashi":

He then used the same slip and coated the mune, in a somewhat uneven layer, and then removed a small portion of the thicker coat to provide a togare kaeri on the boshi.

We then returned to the forge, where he laid aside the blade to continue drying while he very carefully built a bed of coals without any unwanted contaminants. Having set this up to his satisfaction, he then closed off the open front of his blacksmith shop by placing in the sliding wooden doors, making the interior quite dark. He picked up the blade in his tongs, stepped down into the pit about two feet deep, which allowed him to stand up and work both the forge and the anvil which were at near floor level, and briskly inserted the blade into the bed of coals. To my surprise, at no time did the coating show signs of flaking off despite quite positive movement back and forth on top of and within the bed of coals. He continued heating until the blade was a clear cherry red all over, and without prior warning, the blade having apparently reached the exact color he desired, he plunged it into the tempering vat which was also immediately at hand. Upon its removal, the blade was still covered with the coating which, however, was easily scraped off. He then slightly reheated the blade (at no time approaching red heat), and sprinkled droplets of water in a sort of pattern over the ji of the blade, resulting in "reflections" of tempering -- or more accurately -- "suggestions" of tobi-yaki (this he stated would show on polishing).

I then observed the blade to be slightly warped, but the negative curvature he had left in the blade was gone, as a result of the tempering process. He then used his hammer to straighten the slight warping, used his files to remove one or two minor irregularities in the mune, and polished the blade sufficiently on a coarse stone to make the new tempering visible. It was as he had planned, so the blade was now ready to be turned over to the polisher for final refinishing.

The entire process took about two and a half hours, every minute of which was most interesting to me. I am now looking forward with great anticipation to witnessing -- and assisting in -- the forging of a sword from the raw iron to the finished blade. I have been invited to do this by Mr. Fujimura if my duties permit. Such an experience should be very rewarding, and I will do my best to describe it in detail, if I am so fortunate.

Dean Hartley


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