Katana making and marking
How a katana sword is made?
Making katana sword is a sacred art in Japan history. It is a long and a ritualistic process that would take days to weeks and could only create one sword at a time.
Traditionally, before starting to make a katana sword, the smiths would undergo a purification process and wash themselves in water. They would pray to gods for the success in the undertaking.
Katana making involves different stages and several swordsmiths. Each smith is an expert to a specific stage – one in the forging and heating of the raw metal, another in folding the steel, another one in polishing and furnishing the blade. There are also craftsmen who specialize in making the scabbard (saya), handle (tsuka), and hand guard (tsuba).
How a katana is made?
1. Forging the Katana Blade
Type of Steel
Chunks of traditional Japanese steel called tamahagane (made from black sand) are sorted according to carbon content. Higher carbon steel (kawagane) is the hard steel while the lower carbon steel (shingane) is the more malleable steel.
Heating and Forging the blade
The chunks of steel are hammered into flat sheets then placed on a steel scoop. The steel sheets are covered with clay water and drawing paper before it is put inside the forge for heating. Covering the steel would prevent it from reaching the melting point. If the sheets of metal are completely dissolved, the metal will lose their distinct quality of hardness (for the high carbon steel) and flexibility (for the low carbon steel).
When the right temperature is reached, the pieces of steel are put out from the forge and hammered. This is to flatten the softened steel and to remove impurities and air pockets (the bubbles created from heating).
Note: The different types of steel are heated separately.
2. Folding the blade katana blade (Orikaeshi Tanren)
Folding is a famous stage in katana making. This draws out more impurities that can weaken the blade.
The steel is folded vertically until it forms a stick. In every folding made, the steel is heated, hammered, and quenched in water to cool. The harder steel should be folded for at least a dozen times or not more than sixteen times while the softer steel is folded for seven to ten times. Too much folding will make the blade brittle.
Gradually, with the repeated folding, heating, and hammering, the weight of the katana blade will decrease.
3. Combining the steel (Kumi-awase)
A layer of lower carbon (softer) metal is placed between two layers of high-carbon metal. Higher carbon steel (kawagane) is hard so it will be made as the cutting edge part of the katana blade. Lower carbon steel (shingane) is tough and flexible making it best for the back section and the body of the blade. The combination and balance of the qualities of Japanese steel tamahagane gives the extraordinary cutting ability of the sword.
The layers of steel are hammered on a long stick which will serve as guide in forming the exact shape of the katana blade.
Chiseling brings out the details of the blade like the tang (nakago), the tip (kissaki), and back edge (mune).
4. Clay Coating and Heat Tempering
A rapid heating-quenching method is done to completely harden the cutting edge of the katana. Before doing that, a mixture of clay, rust, and ash is coated on the blade. The clay mixture is high temperature resistant. The thickness of the coating will control the effect of heat to the blade. A thicker coating is applied on the back edge and body while a thinner coating is applied on the cutting edge.
The blade is then placed in the forge and heated up to 720-780°C. Once the right temperature is achieved, the blade is taken out from the forge and is immediately quenched in water. The thinly coated part will cool faster and will result to a very strong edge.
The part of the katana blade with lower carbon (the back edge) contracts more freely after the heat-quench method. This reaction will create the natural curve of the sword. The smith must adjust the curvature once he notices the sword makes deeper curve.
Apart from its quality, a katana sword is known for its beauty. Almost all Samurai sword blades are decorated with different marks. The design and types of engravings on the blade would help determine the age, the swordsmith, or era the sword was made.
a) File markings
Katana file marks are etched on the tang of the blade before it is signed by the smith. Patterns would differ in depth, thickness, and spacing. Tools used in marking (e.g. a hammer or a plane used for shaving iron) and style would also vary with period, sword making schools, and sword makers.
Signed katanas would bear the name of the sword smith or the owner of the sword. The signature is generally engraved on the tang together with the province and colony where the sword is made. First recorded signed Japanese sword is a tachi (an ancient long sword) from the Heian Period.
c) Blood groove (Bo-hi)
A blood groove (also known as fuller) is a narrow path found at the back edge of a katana blade. It is made by removing or scraping off steel from a section of the sword. On the contrary, some believe that fullers were created by hammering it in to the blade to make a hallow part rather than removing the steel.
The purpose of a blood groove is to reduce the weight of the sword and improve its cutting ability.
d) Artistic Carvings (Horimono)
Horimono are artistic carvings on katana blades. These carvings are religious and mythical figures like cherry blossom, dragons, and deities. Generally, katanas with horimono are ceremonial swords because carved swords often do not have good quality to be used as weapons.
6. Sharpening katana blade and polishing (Togi)
The process of maintaining, restoring, and sharpening katana blade is summed up in Togi – the art of Japanese sword polishing.
As mentioned earlier, several artists are experts at different stages in making a katana. A togishi is a craftsman who specializes in polishing, refining, and improving the katana sword’s aesthetic and artistic value. He has to be trained for at least ten arduous years to master this craft. Improperly polished swords can be considered worthless and of no spiritual value. In studying the Togi or art of polishing, the craftsman would also learn to be skillful in sword judgment, appraisal, and identification.
The two stages of polishing are the foundation polishing (shitaji togi) and finish polishing (shiage togi). Foundation polishing is where the polisher perfects the basic shape of the blade.
The details of a katana blade are enhanced during the finish polishing. It is also at this point that the beauty of wavy patterns from heat tempering (hamon) will become more visible. This final refining is a very intricate process that only a master could fully comprehend.
When the blade is complete, it is time to assemble the sword by installing the different katana parts.
The sword hilt (tsuka) is wrapped with a silk cloth (tsuka-ito). Wrapping the handle is itself an art called Tsukamaki. With the help of bamboo screws (mekugi), the tang is secured within the katana handle. The hand guard (tsuba), metal washers (seppa), hilt collars (fuchi-kashira), and the square metal (habaki) are fittings that will keep the sword parts stable. The finished sword will be fitted into a lacquered and ornamented wooden sheath (saya).