7 Kamakura timeline

As a part of the sword study, it is necessary to describe the process of making a sword.  This chapter explains only a very basic procedure of sword making, the outlines of the procedure of sword making, since I don’t know much about it.  When I was small, I used to see the process of metal being heated up in the furnace in my father’s factory.  He used to own a machine tool company and forging factory.  It was fascinating to see the metal being heated up, taken out of the furnace, pounded by two men then put it back and pounded again and again.  To this day, I still can remember the exact color of the metal when it should be taken out of the fire.  Strange thing to learn for a small girl.  Not only that it is dangerous for a child to look into the furnace when the metal is being heated.  But those days people’s idea of safeties was different.  I think factory guys were enjoying seeing my brother and I were so impressed, so amazed and looked them up as  heroes.  We kept watching until father moved the factory to a bigger place.  Today, I would never allow my grandchildren to be near a furnace.

The sword-making process is a very involved process and each swordsmith has his own secrets.  Anybody interested in a more detailed explanation, please refer to the book written by a famous swordsmith, Mr. Yoshihara Yoshindo, and the DVD made by his son. Their information is below.  You should be able to buy Mr. Yoshihara’s book from Amazon.  DVD is sold on Japan Amazon.  It may be necessary to go through the proxy service; Zen Market since the DVD is sold on Japan Amazon.

Book: The Art of the Japanese Sword ————-The Craft of Sword making and its Appreciation by  Yoshihara Yoshindo, Leon and Hiroko Capp      Published by Saviolo Edizioni

DVD:  Katana/On Ko So Shin—–Katana project by Yoshihara Yoshikazu (吉原義一)         (Use proxy service-Zen Market, since only Japan amazon sells it)

Tamahagane (玉鋼  )

In the old days, an early sword making time, swordsmiths created steel from iron sand and refined it himself for a sword material.   By the Kamakura period (refer to the timeline above), steelmaking was done by a separate entity.  Swordsmiths buy steel called “Tama-Habane” from a steelmaker.  “Tama-Hagane” is the most important part of the sword making.  “Tama-Hagane” is the steel made with the Tatara process, which is a unique Japanese smelter.

32 Tamahagane 2

Tama-Hagane from Mr. Yoshihara

Kawa-Gane(側金) and Shin-Gane(芯金 )

The Japanese sword is made from two different hardness of steel.  Kawa-Gane is for outer steel.  Shin-Gane for inner steel.  Kawa-Gane is harder steel which contains about 0.6% carbon contents.  Shin-Gane is a softer steel that contains about 0.25% carbon contents.  Japanese swords are made with the harder steel wraps around softer steel, therefore, hard to bend, hard to break

Kawa-Gane (outer steel 側金) —– Shita Gitae (Base forging 下鍛)

Heat up a piece of Tama-Hagane —– Hit with a hammer and make a flat piece—– While Tama-Hagane is still hot, quench in water quickly —– Break into small pieces —– Separately forge a rectangle plate from Tama-Hagane —– Connect this plate with a handle (or a lever called Teko) —– Stack up the previously broken metal pieces on the Teko (handle or lever) carefully and closely.

32 Pile up drawing

—– Cover the stacked up Tama-Hagane with ashes and clay for protection purpose —– Heat this up in the furnace —– Take it out from the furnace, hit with a hammer —– Repeat this process many times to stretch out Tama-Hgane about twice as long —— While Tama-Hagane is still hot, make a notch in the center and fold back into half —– Continue the same process of heat up, hammer to stretch out, fold back (half in sideways and half in lengthwise alternatively approximately 6 or 7 times depends on the original carbon contents in Tama-Hagane).  This process reduces the carbon contents to the desired level.

32 folding drawing

Kawa-Gane (outer steel側金) —–Age Kitae (Finish forging上鍛 )

At the end of Shita Gitae, the block of Tama-Hagane is chiseled to divide into two or three sections —– quench in water —– Cool down —– break into pieces where marked before   —- Combine this and repeat heating, folding, hammering.  This process is for Kawa-Gane (側鉄).  Usually the folding process is done 6,7 time for Shita Gitae (base forging) and 6,7 times for Age Kitae (finish forging), total 12times or so depends on the original carbon contents in Tama-Hagane.  This process is for Kawa-Gane ( 側鉄 )

Purpose of heating hammering and folding

  • Each time the heating and folding process is done, Tama-Hagane loses carbon contents. For outer steel, ideal carbon contents should be approximately 0.6%. If the carbon contents are too high, steel is hard and as a result, the sword can crack.   If it is too low, the sword will be too soft and can bend. A swordsmith judge by his eye to determine the right amount of carbon contents. This is the professionalism and the art of the swordsmith.
  • Removing the slag and impurity from Tama-Hagane.
  • Each heating and folding processes create many layers of thin steel that create the Ji-hada pattern (surface patterns like wood grain, burl look, straight grain or mixture of those)

Shin-Gane (inner steel 芯金 )

Shin-Gane is the inner metal that is softer steel with lower carbon .  By having the softer inside, the sword has flexibility.  Having hard outer steel with higher carbon, it prevents to crack or break.  To make the Shin-gane steel, mix softer steel with Tama-Hagane.  Repeat the same process as Kawa-Gane.

Tsukuri  Komi (造り込み) Sunobe (素延 )

Wrap the Shin-Gane with the Kawa-Gane then weld two pieces together by heating, hammering, and stretch out to make a steel bar like.  There are several ways to wrap the Shin-Gane, but the most common way is called Kobuse (甲伏). The illustration below is the cross-section.

32 Kobuse drawing

Sword Micro (3)

The above photo is the cross-section of a sword that was taken by my husband.  Many years ago, our sword club member gave us a very rusty sword.  My husband cut the sword and took the micro photo of the cross-section.  This sword has a more complicated construction than the usual Kobuse method.  Looks like 3 (4?) different hardness of steel.  It shows this sword was one of the top swords made by the top sword-maker.

Hizukuri (火造 )

Hizukuri is to make the final shape from Sunobe by heating and hammering.  At this point, Ha (cutting edge ) gets thinner, Shinogi side gets higher, and starts to form the shape of a sword.

Arashiage (荒仕上げ  )

This process is rough finishing.

Tuchitori (土取)

Mix clay, pine tree ash, ground stone, and water. Paint this muddy mixture on the sword.  Around the Hamon area, scrape off a thin layer of the muddy mixture a little, then dry out.  By doing Tuchitori process, Hamon is created and cutting-edge hardens at the same time.

Yaki-Ire (焼入れ)

After the muddy paste is dried, heat up the sword evenly in the furnace.  Judging by the color of the heated sword, pull out the sword from the furnace then quench into the water.  Usually, this process is done after the sun goes down so that the swordsmith can see the color of the metal and can judge the temperature of the heated sword better.  This is the most important process since all the work done up to this point may be ruined if he fails to judge the precise color of the heated sword,  water temperature, and the timing of quenching.

The final process is to send the sword to a polisher.  A polisher called Togishi polishes and sharpens the blade.   He brings out the beauty of the surface and sharpness of the sword, that completes the process.  Every step of sword-making is important but this final process is a very important part.




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