How are Authentic Samurai Swords Made?

How Japanese Swords are forged

 Authentic Japanese swords are made from specialized Japanese steel which consist of combinations of hard, high carbon content steel and tough low carbon content steel. There are qualities in both types of steel, both good and bad. High-carbon content steel is harder and able to hold a much sharper edge than low-carbon steel, but it is brittle and can break in combat. Low carbon content steel will allow the blade to be more malleable, making it possible to absorb impacts without breaking but this lower carbon content steel will become blunt in the process.

The blacksmiths who forge authentic samurai swords take advantage of the best attributes of both of these kinds of steel. The blacksmith begins by folding and welding pieces of both types of steel several times in order to work out most of the impurities. The high carbon content steel is then formed into a U-shape and a piece of low carbon soft steel is placed in its center. The resulting block of steel is then hammered, or “drawn out” to form a rough blank that will soon be a samurai sword.

At this point it may have only a slight curvature or none at all. The curvature of a samurai sword is attained by a process of heating and quenching the sword in water or oil. In this process the sword maker coats the blade with several layers of moist clay slurry which is a recipe that is unique to each sword maker, but in general this this composition can include: clay, water, (sometimes) ash, grinding stone powder and/or rust. The blacksmith will coat the edge of the blade with a thinner clay layer than the sides and spine. After this the sword is heated and then quenched in water, or oil. The clay functions as heat insulation so that only the edge of the blade will be hardened with quenching. This also causes the blade to form a slight curve due to the reduced strain along the spine.

 The quenching process also creates the distinct wavy line down the center of the blade. This is called the “hamon” which can only be seen after the sword has been polished. The hamon is where most say the beauty is to be found in samurai swords. Each hamon is unique to the sword’s maker and serves as the forger's signature.

After the sword blade is forged it will then sent to be polished. The polishing of samurai swords can take anywhere between one and three weeks. The sword polisher will use finer and finer grain polishing stones until the sword blade has a mirror finish. This process is called glazing. This will make the blade razor sharp and reduce drag, making it much easier to cut with. The curvature of a samurai swords blade also adds to its cutting force.

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