Chapter 2. Charcoal and Forging—the Birth of a Katana.
Why is the Japanese sword different to every other traditional craft? Is it because it isa symbol of the Japanese origins of spirituality? In order to answer these questions,first I must give a brief explanation of the Japanese sword production process.
In brief, the Japanese sword’s character derives from being made from steel (hagane),
which is repeatedly forged and folded. Hagane is made from satetsu (sand-iron).
Nowadays, steel made from sand-iron is rare in Japan. In fact, this kind of steel
production process is uncommon in the world. You may have already heard of thetatara steel making process—a rectangular clay furnace in which sand-iron andcharcoal are smelted to produce steel. The main smelting process takes three days andnights with air constantly pumped into the furnace (an essential part of the process).
Extremely high temperatures are not required. A relatively low temperature of about1200 - 1400 degrees is used. In foreign countries where coke instead of charcoal isused, temperatures of 1500 degrees or more are necessary in order to smelt the ironore.
The furnace creates temperatures of about 1400 degrees Celsius. During the three-day
smelting period, the inner part of the clay walls of the furnace become incorporated
into the large block of molten steel. At this point I will cease with the scientificinformation. In short, the sand-iron and charcoal elements transform inside the base of
the furnace to form the kera (large block of steel). This is the raw material from which
Japanese swords are made. This kind of steel is called tamahagane (jewel steel).
Tamahagane, like other steels can be graded: 1st class, 2nd class, etc. As you wouldexpect, this top quality steel is used to make Japanese swords. The word tama is not
only used for steel, it also has a spiritual meaning. It becomes the tama-steel (steel oflife), from which the pride of the swordsmith is born. This can be used with steel
refined by the swordsmith himself called oroshi-gane, to obtain the required amountof carbon.
From here onwards is the job of the swordsmith. Well, you may ask, why is the foldforging method used? You have probably seen photographs of swordsmiths sitting infront of a forge gripping the hot steel with long pliers and assisted by 1-3 apprentices
using large hammers. They are performing the fold forging process. It is a popularsword-making scene. This is called tanren—forging. This word tanren can also refer
to modern young men. If they do not have some kind of spiritual forging, they will
not grow up to be good men. The smith and the apprentice take turns to hammer thesteel. This kind of exchange is where the phrase aizuchi wo utsu—to cooperate
together—comes from.
The tamahagane is heated and crushed into a flat plate. It is then broken into smaller
pieces approximately 2 cm in diameter. Next, the swordsmith makes a tool called ateko. This is an iron bar with a plate (teko-dai) attached used for placing the billet ofsteel into the forge. The small pieces of tamahagane are stacked onto the teko-dai andwrapped in a sheet of Japanese paper to prevent it from falling off. Then, burnt ricestraw is placed on top of the billet followed by an application of clay slurry. Thisapplication of burnt rice straw and clay insulates the steel, preventing oxidization. The
billet is then placed in the fire to be heated (tsumi-wakashi).
When it reaches the correct temperature, the steel is removed from the fire and beaten
using large hammers. An incision is made in the center of the block before it is foldedback on itself. Depending on the school or swordsmith, this process is usually
repeated between 10-15 times. The steel is not only folded horizontally, but is also
folded vertically (lengthwise) whilst repeatedly being heated and hammered. Thismethod is referred to as orikaeshi-tanren (fold-forging). Using this process, if thesteel is folded 15 times it produces 33,000 layers of strong steel. This repeated foldingof the steel helps to remove any impurities—a fact which has been verified by modern
scientific study. Gradually, through the repeated heating and forging, the weight ofthe steel decreases. I am very impressed with the ingenuity of our ancestors.
Once production of the kawagane (outer-steel) has been completed, the blade’s lower
carbon, softer steel inner-core (shingane) is produced by the same folding method.
This time folding only takes place between 7-10 times. The kawagane (outer-steel) isthen fashioned into a U shape, the shingane (core steel) is inserted into it, and they arethen heated and welded together. This process is called tsukuri-komi. This particularmethod of tsukuri-komi is called kobuse. There are other methods such as sanmaigitae in which a harder piece of steel for the cutting edge is placed under the shingane
in addition to kawagane on either side. This combination of hard and soft steels
produces swords that are resistant to bending and breaking.
Note: Do you know the average weight of a Japanese sword? Blades weigh between
750 to 1100 grams. Once they are fully mounted they average around one kilo. This is
why it is good to use a bokuto (wooden practice sword) of over one kilo. It is notgood to always practice with a light bokuto if you intend to use a real sword.
The remaining processes are sunobe, hi-zukuri, tsuchioki and yaki-ire. Followed by
the finishing processes kajitogi, nakago-shiage, mei-kiri, etc. I thought I would able togive a simple explanation in a single article, but it has turned out to be rather long. Ithink I need to take a rest and smoke my pipe. I will continue with the katana making
process next time.
(Preview) Chapter 3: Purification by Fire and Water
Many swords from sword making towns, such as Osafune in Bizen province (presentday Okayama prefecture), are ranked as National Treasure or Important Cultural
Property. There are also many swords made by the same smiths that do not attainthese standards. Why is there such a gap in the workmanship of the same smiths? Thisis because the Japanese sword is baptized by fire (yaki-ire). Our ancestors believedthat although the sword is produced by man from natural resources, the fate of its
completion is decided by the gods.