What is a Katana (Uchigatana)


The "katana" is a sharp and deadly, but the word katana seems to have a somewhat gentle and calm resonance. Perhaps because this feeling is familiar to the Japanese, even those who have never seen a katana can imagine what it is. However, many will mistake Uchigatana for Katana, katana is actually a general term for all Japanese swords, the specific type of Japanese sword Uchigatana is actually the right name for this famous sword. In the following, I will introduce the history and definition of the katana (Uchigatana), how it is made, the difference between Uchigatana and tachi, the law and regulation, and what to look for when appreciating a katana or even customize a katana.

History and Definition of the Katana (Uchigatana)

The making of swords in Japan is thought to have started around the 6th century, during the late Kofun period. Prior to this, around the 3rd century during the late Yayoi period, bronze swords were brought from mainland China, and the technology to work with iron was also introduced to Japan, leading to the manufacture of swords in Japan.

Eventually, a unique Japanese method was established, and "Japanese swords" began to be made. A Japanese sword is a sword made by a process called "folding and hammering", where a pure metal called "tamahagane" is heated and then folded and hammered many times.

The first swords made in Japan were straight swords, or "chokuto", without curvature. As sword-making technology evolved, by the late Heian period, Japanese swords developed their unique shape, with a curved blade known as "wantou". This wantou became the prototype of the famous Japanese sword we know today.

There are several types of Japanese swords, but the first to appear was the large, single-edged, curved sword, is the "tachi". In contrast, the Heian period dictionary "Wamyou Ruijushou" explains the term "kodachi" to mean "katana". This suggests that in ancient times, a small single-edged sword was called a "katana".

In the late Muromachi period, the "uchigatana" appeared as a type of Japanese sword. Unlike the tachi, which was mainly used to "cut" opponents in mounted warfare, the uchigatana was primarily used to "strike down" opponents in foot combat. While the tachi has a long blade and is made with the blade facing downwards, the uchigatana is characterized by having the blade facing upwards.

The uchigatana is shorter than the tachi, and because it can be conveniently tucked into a waist belt, it became highly popular, replacing the tachi. Over time, the uchigatana, being smaller than the tachi, came to be called "katana," which originally meant a small sword. In other words, the term "katana" refers to the uchigatana.

Why short swords became popular
From the middle of the Heian period to the middle of the Muromachi period, warriors fought on horseback, wielding their swords in one-on-one battles, requiring the long tachi.

However, as close-quarter battles conducted by foot soldiers became the major battle form, the uchigatana, which had less curvature and a shorter blade than the tachi, became popular as it could be quickly drawn from the scabbard. Thus, from the Muromachi period onward, the uchigatana became the mainstay on the battlefield, and it came to be called "katana".

Furthermore, in the Edo period, the Honami family, who made a living appraising swords, defined a katana as something that is between 2 shaku (60.6 cm) and 2 shaku 6 sun (78.8 cm) in their appraisal document, the "origami".

Also, during the Edo period, samurai were obligated to carry "daisho," which means two swords, one large and one small. This refers to carrying both the uchigatana and a shorter sword called the "wakizashi." This further established the term "katana" to refer to the uchigatana.

How to make a katana

The process of making a katana involves a unique manufacturing process that developed in Japan. Let's introduce the materials of the katana and the process until it is completed.

Materials of the Sword "Tamahagane"

The material for a sword is the highest quality steel called "tamahagane", from which impurities have been removed. We are familiar with the metal iron, and both iron and steel are made from iron ore or sand iron, but they have different carbon content. The more carbon in the steel, the harder and stronger it is, so steel is an alloy in which the carbon content of iron has been intentionally increased.

Even within steel, tamahagane, which is the material for swords, is refined through the "tatara ironmaking" method, in which the raw material sand iron is fired in a clay furnace called a "tatara" using charcoal as fuel. By processing in the tatara, which is at a lower temperature compared to modern blast furnaces, high-purity iron, i.e., tamahagane, can be obtained without impurities such as phosphorus and sulfur dissolving in.

The making of a Japanese sword starts with this tamahagane, and removes more impurities and adjusts the proportion of carbon through processes such as "water reduction" (mizuheshi), "bubbling" (wakashi), and folding and forging.

Water Reduction 水減し
Water reduction is the process of dividing the tamahagane obtained from tatara ironmaking according to its carbon content. When the heated tamahagane is hammered out to a thickness of about 3 to 6 mm and then quenched in water, the parts with a high carbon content break.

While tamahagane becomes harder the more carbon it contains, if it is too hard, it becomes difficult to shape, and even if it is made into a sword, it becomes easy to breaking. Therefore, tamahagane with a suitable carbon content for sword-making is separated out in this way.

Furthermore, when the unbroken parts from the water reduction are hammered and split, the parts with a high carbon content and are hard will break cleanly, while the soft parts with a low carbon content will not break. The hard steel is used as the material for the "skin steel" (kawagane) that is used on the surface of the sword blade, while the soft steel is used as the material for the "core steel" (shingane) that forms the core of the blade.

Bubbling 沸かし
Bubbling is the process of piling up the steel that was split during water reduction without any gaps, then heating it again and hammering it into a mass.
During this process, the impurities that were hammered out scatter as sparks, but the high-carbon, high-quality steel also tends to scatter, so to prevent this, it is piled up in the center.

The reason for splitting the steel and then performing the bubbling process is to prevent this, and the swordsmith carefully examines the impurities in the steel and stacks them accordingly. The process of heating the stacked steel and letting the heat thoroughly penetrate is called "stacking bubbling".

Then the steel is hammered further to drive out impurities and is hammered solidly into a mass in the "main bubbling" process. During this process, the swordsmith checks the state of the steel by observing the sparks flying off and the sound of the hammer, and adjusts the heat accordingly.

The process known as "folding and forging" involves further hammering the steel after tempering to remove impurities and eliminate carbon inconsistencies. The steel is extended by hammering, then folded in half, and the process is repeated. The hard skin steel used on the surface of the blade goes through this process about 15 times, while the softer core steel is processed 5-6 times. Through folding and forging, different types of steel are combined to create the "ground iron" (Jigane) that adds to the beauty of the sword.

The phrase "striking in unison", which describes multiple swordsmiths hammering alternately, originated from this process and has come to mean responding in harmony with another person's speech.

In the "assembly" phase, the hard skin steel and soft core steel, which were forged separately during folding and forging, are combined. The soft core steel is wrapped with the hard skin steel and heated, creating a sword that is hard at the cutting edge and tough at the body, resisting breakage. This assembly process varies, but the method involving these two types of steel is known as "Kobuse".
Further methods include "Hon Sanmai", which involves three types of steel including one called "blade steel", and "Shihozume", which adds a fourth type of steel known as "ridge steel".

During the "shaping" phase, the steel is slowly hammered into the shape of a sword in a process known as "sunobe". The tip of the sword is cut at an angle to form the point. The "Yaki-ire" or "hardening" process follows sunobe. This involves the careful sculpting of features like the ridge line and lateral line. The swordsmith meticulously hammers the steel to form the envisioned shape of the sword. The process determines the type of sword, such as "Shinogi-zukuri" (ridge construction), "Hira-zukuri" (flat construction), or "Shobu-zukuri" (iris leaf construction).

Next comes "clay tempering". Here, the sword is heated to 726-800 degrees Celsius and then quickly cooled in water, causing the distinctive curvature and temper line (hamon) of the Japanese sword to emerge. Before tempering, a clay compound mixed with charcoal and grinding stone powder is applied to the sword and left to dry.

This compound is applied thinly to the cutting edge and thickly to the back edge of the sword, so that when it's quenched in water, the thinly coated edge cools rapidly while the thickly coated edge cools slowly, giving rise to the characteristic curve of the sword. At this time, the rapidly cooled edge steel transforms into a hard structure called "martensite". The temper line is the pattern that appears on the blade due to this transformation, and is one of the key points of sword appreciation.

In the final "finishing" stage, the blade is polished, a process called "Kaji-oshi", and the tang (the grip part of the sword) is filed down, a process called "Nakago-jitate". When the swordsmith is satisfied with the result, they carve their signature or "mei" on the tang, marking the completion of the sword.

The "mei" is a set of characters engraved on the tang of the sword. There are two types: the "Omote-mei", carved on the outer side of the tang visible when the sword is worn, and the "Ura-mei", on the reverse side. The swordsmith's name is usually engraved on the Omote-mei, and the date of sword making is typically engraved on the Ura-mei.

In the case of a tachi (long, curved sword), when hung at the waist with the blade facing down, the outside-facing side is where the front inscription, or "tachi-mei", is engraved. On the other hand, for a katana (sword), when it's worn with the blade facing upward on the left waist, the front inscription, or "katana-mei", is engraved on the outside-facing side.

This terminology itself clarifies that the katana is indeed a sword. Even though the use of tachi ceased during the Muromachi period and katanas became mainstream, the tachi's hilt was cut down and refinished as a katana, a process known as "suriage" (shortening). Suriage tachi may lose their engraved inscriptions on the hilt, but the swordsmith and the year of production can be guessed from the characteristic temper patterns on the blade, and the "jigane" (ground steel) that appears on the surface of the blade.

The Law and Swords:
Legally Defined Swords:
In the legal context, a "sword" is a type of Japanese sword and is clearly defined and regulated under the Firearms and Swords Possession Control Law of the Penal Code.
Article 2 of the Firearms and Swords Law states, "The term 'sword-type' refers to swords, spears and naginata with a blade length of 15 centimeters or more, and swords, daggers, and switchblades (excluding switchblades with a blade length of less than 5.5 centimeters that do not have a device to fix the blade body in a straight line with the scabbard when the blade is opened, and whose blade tip is straight, the tip of the spine is rounded, and the line connecting the point 1 centimeter from the cutting edge on the spine and the cutting edge intersects with the line of the blade tip at an angle of 60 degrees or more) with a blade length of 5.5 centimeters or more."
Additionally, Article 3 of the Firearms and Swords Law clearly states, "No person shall possess firearms or swords unless they fall under any of the following items."

Points of interest when appreciating swords

A Katana is not only a weapon but also a work of art. Knowing several points of interest when appreciating a sword should make the experience more enjoyable. Here we introduce key points that highlight the beauty and charm of swords.

Shape: This refers to all parts of the sword except the handle(Tsuka). Starting from the tip of the sword (kissaki), the curvature, ridge line and many other features each carry information about the era in which the sword was made and the swordsmith who made it. As the shape of the sword has evolved with changes in combat styles, it can also serve as a clue to understand the battles of the time it was made.

Hamon Line: This is the white, wave-like pattern that appears on the blade due to the differential hardening process in sword making. The hamon line can be varied by adjusting the temperature and timing of tempering, and the way the clay slurry is applied to the blade before tempering, reflecting the individuality of the swordsmith.

The hamon is diverse and can be broadly divided into linear "straight hamon" and non-linear "wild hamon". In the case of straight hamon, there are four types: "thread straight blade", "narrow straight blade", "medium straight blade", and "wide straight blade", in order of the width of the blade pattern.
When it comes to wild hamon, there are over 28 different names, but let's introduce some representative ones here.
Cloves: This blade pattern resembles a string of cloves, a tree whose flowers are used as a spice.
Checkered: This blade pattern features a continuous pattern of concave and convex shapes. Varieties of this pattern include "fallen checkered", which is sharp like the blade of a saw, and "three cedar checkered", where the concave and convex patterns are disordered every three lines.
Wavy blade: This blade pattern appears as if it is significantly undulating.
Martensite and pearlite: The blade pattern contains "martensite", which appears as white grains like sand due to the tempering process, and "pearlite", which appears as if covered with a white haze. Martensite particles are coarse and can be seen with the naked eye, but pearlite particles are fine and therefore difficult to confirm with the naked eye.
Steel texture: The steel texture refers to the skin pattern that emerges on the blade as a result of repeated forging, and there are said to be over 20 types. Representative steel textures include "straight grain skin", "aligned grain skin", "burl grain skin" that resemble the cross-sections of wood, "pear ground skin" that has a grainy pattern like the flesh of a pear, "herringbone skin" that resembles a herringbone pattern in woven fabric, and "plain skin" that is as smooth as a mirror.

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