Are you aware of all the subtle steps taken by a master blacksmith to create a sharp, cutting, yet sturdy katana? Probably not, but you should know that crafting a traditional katana is an almost sacred art. In fact, the master blacksmiths followed a meticulous ritual. A Shinto altar was set up in the forge, and prayers, baths, and purifications were part of the process before the actual work began. So, if you want to discover all the secrets of traditional katana craftsmanship, follow the guide.
Forging a Katana
First and foremost, let's focus on the metal used. In Japan, the iron ore is of poor quality, with less than 1% iron content. This is why the artisan blacksmiths engage in a lengthy process to obtain both resilient and sharp swords.
The master blacksmith must extract the iron by smelting the ferruginous black sand, the ore, at a very high temperature of about 1400 degrees Celsius. It takes around 8 tons of sand to yield approximately 500 kg of usable steel. The resulting iron from this operation is called tamahagane or 玉鋼. To be of high quality, the tamahagane must have been extracted under proper conditions. The addition of carbon, its quantity, and the right moment to add it will determine the tamahagane's characteristics. Each blacksmith has their unique expertise, which they carefully guard.
Next, the artisan compresses the tamahagane pieces, flattening them into galette-like forms, which are then heated until they turn red and cooled in very cold water. The process helps to remove impurities from the metal and sort the pieces based on their carbon content. Highly carburized pieces appear gray and will result in a hard steel that improves the sword's cutting ability. This type of steel is called hadagane.
The shingane, or soft steel, shows a whiter grain and provides flexibility to the sword, making it less brittle. From the obtained plaquettes, at least two minimum bricks will be made: one of shingane and the other of hadagane. These bricks will be individually layered. The metal block is hammered, elongated, and folded upon itself at least fifteen times. Traditionally, it used to be folded 23 times. The final step of this stage is to assemble these bricks to create the blade and give it its shape. Once again, each blacksmith has their own method, resulting in a unique sword compared to those of their colleagues.
This art and expertise make a traditional Japanese sword a highly valuable weapon. Finding the right material balance is crucial for creating a sharp blade that is also resistant to impact. The subsequent quenching process will contribute to the sharpness of the blade while maintaining enough flexibility to prevent it from breaking.
Quenching the Blade
To achieve these specific characteristics, a partial quenching, also known as selective quenching, is applied. The blade is heated to about 800 degrees Celsius before being quenched in water while partially covered with a type of coating. This operation involves covering parts of the blade with a mixture of clay, silica, charcoal, and other specific ingredients unique to each blacksmith.
The covered area of the blade corresponds to its back and sides. By applying this coating, the areas where flexibility is desired are insulated from the heat. Consequently, when the blade is immersed in water, the parts protected by the clay mixture cool more slowly, retaining more flexibility in the steel. As a result, the sword's blade is better equipped to withstand impacts and torsions. In contrast, the unprotected part, the cutting edge, cools rapidly, acquiring maximum hardness. This technique enables the blacksmith to balance these two contrasting properties of the steel, aiming to achieve the best of both worlds.
Furthermore, during the cooling process, a thermal shock occurs, creating the famous quench line, or hamon. This hamon pattern varies from one blacksmith to another, from one school to another. There are 53 types of hamon patterns documented. The hamon contributes to the signature of a sword and helps identify the blacksmith who crafted the blade.
Before entrusting the sword to the master polisher, the blacksmith performs a preliminary polish to check if the blade meets expectations. It allows the blacksmith to verify if the quench line is well-defined and if the steel is strong and homogenous. If satisfied, the sword is handed over to the togishi or 研ぎ師, the artisan in charge of the polishing process.
Polishing the Blade
The polishing of a katana blade is an art in itself. This is why the togishi, the artisan responsible for this task, was considered a master, just like the blacksmith. The togishi's work goes beyond merely sharpening the blade; it involves a meticulous process that reveals all the blade's characteristics. Additionally, the togishi has learned the art of reading blades. By observing a blade, they can assess its overall quality, and only then does the mechanical work begin.
The first part of the process is called ji-togi or 地磨ぎ. It involves removing rust traces and reworking the blade's shape based on the blacksmith's craftsmanship. It is a delicate and crucial task, as any error at this stage could severely damage the blade. To accomplish this, the polisher uses a series of abrasive stones, starting with the most aggressive one. Each stone serves a specific purpose. The first one gives the blade its specific shape, while the subsequent stones help remove the marks left by the previous ones. The final stone mainly highlights the blade's grain.
The following operations collectively form the shiage or 仕上げ. This work focuses on aesthetics and precision. It consists of several stages, each with its own purpose. Small stones, measuring 3 to 5 mm, are used to polish the edge and tip. A mixture, applied with oil, enhances the blade's darker side and reinforces the grain's strength. Using a pen-like tool with a rounded metal tip, the artisan creates a mirror-like finish on the steel. Small oval-shaped stones give a white appearance to the upper part of the hamon. The quench line on the tip, known as bōshi in the kissaki (the tip), is also whitened, while the yokote (the ridge separating the tip from the rest of the blade) undergoes a finishing touch to enhance its appearance.
All these different stages compose the shiage. Only when this stage is completed can a sword be considered finished. A cutting test, known as tameshi giri, will verify if the katana lives up to expectations.
All these artisans, even masters, have endeavored to pass on their expertise and create genuine works of art. While some of these steps have been simplified with modern methods and technological advancements, the crafting of a katana remains a remarkable feat that reflects a long tradition and the true culture of the samurai, the soul of the warrior.