The Mysterious Art Of Crafting Samurai Swords

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Crafting Samurai Swords

Regular swords are nothing. A piece of cheap metal, punched out of a machine-produced sheet, given an edge that won’t last and sold to rubes. Meh.

But samurai steel is not a sword. It is a unique thing, nearly a living thing, brought out of fire and metal by hand, judged at each step, with inferior efforts thrown away in contempt. Only the very best examples of the swordsmith’s art would find their way into the hands of history’s finest edged-weapon warriors.

Only a few men in Japanese history could be called master swordsmiths, though many others produced decent enough weapons for lesser fighters. The masters were people who could tell by looking and feeling and smelling exactly what was happening inside the steel.

The process for each maker, from the most casual to those designated as National Treasures of Japan, is similar. But as in all things of great beauty, it is the smallest detail worked in the most elegant way that make the difference. You want to understand Japanese craftsmanship that blends science, art and magic? See how a samurai sword is created.

Making Steel

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Long ago, Japanese swords were made mainly of steel scraps, old nails, used tools and the like. It made for a poor weapon, even in the hands of a skilled craftsman.

The key quality breakthrough came with the refinement of tamahagane (jewel steel). Over three days and three nights, workers shovel tons of iron-bearing river sand and charcoal into the mouth of a tatara, a rectangular clay furnace blessed by Shinto priests and built specifically to produce a single batch of tamahagane.

The charcoal is a key ingredient in steel as a fuel source for the furnace, with the carbon released hardening the steel. The tatara will reach temperatures of up to 2,500 degrees Fahrenheit, reducing the iron ore to tamahagane.

The best charcoal comes from pine wood, but chestnut is also used. The different size of charcoal coals used control the forging temperature in the hearth and provide just the right amount of carbon for the steel. There is an old saying that the trainee had to spend three years just to learn this first step.

Dissolving the Carbon

While fired at high temperatures, the tamahagane is never allowed to reach a molten state. This is to ensure that just the right amount of carbon will dissolve into the tamahagane.

Swordsmiths use two types of tamahagane: high-carbon, which is very hard and allows for a razor-sharp edge, and low-carbon, which is very tough and allows for blocking the opponent’s blows. A sword simply composed of one kind of steel or the other would either dull too quickly or be too brittle to sharpen.

On the third night of smelting, the clay furnace is shattered to expose the tamahagane. The smith will then break apart chunks of raw steel with his hammer and chisel to discern their carbon content simple by feel.

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Removing the Impurities 

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The best pieces of tamahagane are then reheated, hammered, and folded (orikaeshi) repeatedly in order to further combine the iron and carbon, and to draw out any remaining undissolved impurities, known as slag. This step is as vital as it is tedious, because if other elements besides iron and carbon remain in the resulting sword, they will weaken it.

Hammering is a step for the apprentice. To train his student, the master swordsmith leads the hammering process with his kozuchi (small hammer), tapping precisely where the apprentice should bring down his heavier hammer. The steel is folded 12-15 times over on itself. It may later be given another seven or eight folds if the smith is unhappy with the carbon distribution.

Once the skilled smith and his apprentice have removed all the slag, the master can make a final judgment of the carbon concentration of the tamahagane by the degree to which it yields to his constant pounding. One expert has likened eliminating slag from steel to squeezing liquid from a very hard sponge.

Forging the Blade

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After the swordsmith hammers all slag from the tamahagane, he heats the hardest steel and shapes it into a long, U-shape. He then hammers the low-carbon steel snuggly into the channel and forges the two metals together.

Both types of tamahagane are now exactly where they need to be: the hard steel forms the sword’s outer shell and deadly blade, while the even tougher steel serves as the katana’s core. This perfect balance of properties is what makes the katana the finest sword ever created.

The sword also serves as that sought-after nexus of art and science. The smith must first understand the requirements of the samurai for his weapon.

Understanding that the cutting edge of the blade must have a certain sort of characteristic, the next task is to develop, over literally centuries with knowledge passed on in a chain of masters and apprentices, the voodoo of how to achieve these properties through the right materials and the right craft.

Coating the Blade

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The katana’s basic body is now complete. Yet despite the weeks of work necessary to reach this step, the real work is just beginning. Prior to firing the sword a final time in the furnace, the smith paints a thick, insulating mixture of clay and charcoal powder (Yakiba-tsuchi) onto the blade’s upper sides and dull back edge, leaving the sword’s sharp front edge only lightly coated. This serves both to protect the blade and to give it its signature wavy design called the hamon, which later polishing will reveal.

Each master will have his own secret blend of materials used to create the hamon, and his own signature style of applying that mixture. Experts can date a katana, and often recognize an individual master’s work, simply by the hamon. For those who acquire a true samurai sword, the hamon forms a significant part of its aesthetic.

With the hamon work completed, the swordsmith places the katana back into the fire to be heated to just below 1,500 degrees. Too cold and the sword will not bend in the next step. Too hot and the sword will crack, and all the work to date will be lost. Other than that, no pressure, right?

Curving the Steel Of A Samurai Sword

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Up until this time, the katana is a straight piece of steel. It is now time for the smith to create the sword’s distinct curved blade.

The curve is created by the dissimilar carbon levels in the types of steel used to make the blade. The smith pulls the katana from the fire and plunges it into a trough of cold water in a rapid cool-down process called quenching (Yakiire).

Because the sword’s back edge and inner core contain very little carbon, they contract more than the high-carbon steel at the front edge of the blade. The difference in both the degree and speed of contraction between the two forms of tamahagane causes the sword to bend in real time in the smith’s hand.

In many minds, quenching is the stage requiring the most judgment by the smith. Even among masters, it is said that as many as one in three swords is ruined.

Polishing A Samurai Sword 

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Having seen the katana go from iron ore to curved blade, the swordsmith’s primary work is done. He may mark his initials on the tang of the sword, or he may not, choosing to remain humble, knowing some part of his work was guided by the Shinto gods and was outside of his control. Either way, the smith hands the sword over to a skilled polisher, and turns to his next piece.

A polisher then begins a two week or more process of hand-honing the sword to a razor-sharp edge. He does this with a series of grinding stones, often passed down through families for generations. Called “water stones,” these are typically composed of hard silicate particles suspended in clay.

As the clay slowly wears away during use, more silicate particles are revealed, guaranteeing an equal degree of resistance throughout the life of the stone. It is perhaps apocryphal, but still within the bounds of reality, that the final lick of polishing is provided via the artisan’s own breath against the cold steel.

Final Touches

Once the polisher finishes his work, metalworkers add a hand guard to the sword’s hilt. Carpenters will create a lacquered wooden scabbard, and other tradesman will use leather to wrap the handle.

We mentioned that the swordsmith’s work is mostly done once he hands the blade to the polisher. But there is one more, final, step: the katana is returned to the swordsmith, who examines the weapon one last time.

Despite the process taking six months or more to this point, the smith is free to reject the piece. It is his name and reputation that will follow the sword for hundreds of years or more, an obligation to history that is not taken lightly.

Much of what is known about the sword-making process comes from historical literature and drawings, and also from the national treasure swordsmith, Miyairi Akihira (1913-1977), whose work was documented photographically before his death.

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Samurai Swordmaking

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