Jihada and jigane-"folded steel katana"

What is jihada and jigane？

The steel (jigane) on the surface of a Japanese sword has a definite color and texture, and since the steel has a very dark appearance, it requires a good grind to bring out the details. Examining a well-made and ground Japanese sword usually reveals a clear color and fine texture. In addition, it is common to observe the distinctive surface pattern created by repeated folding during the forging process, called jihada, which varies from sword to sword depending on the method of steel making and the steel used by the sword maker for a particular sword. In addition, the folding method varies from one school to another, so the jihada is an important feature for identifying the schools of swordsmiths. while the jihada of koto period swords varies from region to region, the jihada of shinto period and onward swords does not vary from region to region, but rather from one swordsmith to the next. In addition, the jihada pattern of a sword can be easily distinguished only if it is very well polished. Therefore, when evaluating Japanese swords, the surface texture, color, and jihada are all characteristics that need to be carefully observed. The following are jihada patterns of Japanese swords forged by various swordsmiths at different times in history.

Itame-Hada

This is the most common type of hada pattern. A pattern of annual rings with an irregular and incomplete oval shape. A particularly large pattern is called o-itame. This type of hada pattern can be seen in the Soshu-den
Soshu-den works of the famous blacksmith Masamune and the works of the
Hoki province (Tottori and Shimane prefectures). A tightly forged itame or ko-itame hada is often seen on the works of the Yamashiro (Kyoto) smiths of the Kamakura period; particularly fine, well-forged works are referred to as nashiji-hada (Japanese pear skin).

Masame-Hada

Masame-Hada is similar to a straight wood grain pattern.

It can be seen in the works of the Yamato schools from the mid-Heian period onward, especially in the blades of the Hosho school, and their disciples, influenced by the Takumi style, may also have such jihada on Shinogi ji.

Mokume-Hada

Mokume-hada looks like the rings of a tree and is often mixed with itame-hada, but it is smaller, more circular in shape and arranged more regularly than itame-hada. Often seen in Bizen Den's works. Works with particularly prominent mokume-hada include the Aoe school of Bitch Province (Western Okayama Prefecture), whose hada is said to resemble the texture of chirimen silk crepe, so it is called chirimen-hada.

Nashi-ji Hada

The jihada consists of a large number of nie crystals, which are often blackened by grinding, making the crystals stand out even more and giving them a fine dotted pattern similar to that of the skin of a pear. This type of jihada is not easy to see by observation and must be examined carefully, otherwise it can be easily misjudged as a mechanical product without jihada, and nashi-ji Hada is a symbol of yamashiro-den.

Ayasugi-Hada

Ayasugi-Hada is formed by artificially bending masame-hada. It is shaped like parallel waves. This forging method is used only by the gassan school, so it is also called gassan-hada.

No-ji style

In addition to hamon, the texture of the forging is not visible. Although the texture is not visible, the workmanship is still folded and kneaded, but the folding method is different from that of other genres, resulting in the disappearance of the texture, which is known as the no-ji style. This forging method was created by Kazuhide Ikeda, a disciple of Suishinshimasahide, the originator of shin-shinto (at the beginning of the 19th century), and because no jihada can be seen, it can easily be misinterpreted as a mass-produced model decorative sword made in a factory. The ji-less style of blade can be easily confused with an ancient handmade sword or a modern mechanized sword by considering the hamon, the shape of the blade, the stem, and other parts of the blade.

Nioi and Nie

Due to the Japanese sword's selective hardening of the blade to maintain relative softness, the blade The emergence of literature. This shows a typical Japanese sword containing two types of steel: the blade area "ha" the hard steel and the soft steel of the blade body "ji". At the intersection of the two types of steel, a line is formed, a clear and visible boundary. This boundary is usually composed of very small crystalline particles (nioi), some of which are too small to be visible to the naked eye, so this line is visually a continuous and uninterrupted line. The line is usually white and clearly separates the blade text from the ji. Sometimes this line is composed of larger particles that are the same as nioi, but the individual boiling particles are large enough to be clearly visible to the naked eye. Many blade texts are composed of nioi, but there are also some nioi. The nie that appears above the blade text is called (jinie). The appearance and composition of the particles and lines of ni depend on the swordsman's approach, the steel used, and the execution details of the firing process.

This hamon has a very complex nioi line, which is a clear white line that divides the hamon zone and is composed of extremely small nioi particles.

Hamon contains hooks and many nie particles. Many individual nie particles can be seen in the white area of Hamon, as well as in the area where they have just entered the Hamon area. Sometimes, nie particles also appear on the main body of the blade, as shown in the figure. These large and clear nie (jinie) appear above the Hamon area, directly above the shinogi and shinogi lines.

Above Hamon, the blade appears white in appearance, and this effect is called "utsuri".

How many times is steel folded to make a katana?

The process is very complicated, there are fifteen folding processes, in fact, each folding requires a thousand hammers to give it a long length, and also in the charcoal fire to remove impurities. After fifteen folds, a katana, at the very least, has 30,000 layers of steel in it, which should be called a thousand hammers. That is why katana first of all does not break easily, it is very hard, it does not bend easily, it cuts sharp, and it is only in the process of folding that the beautiful jihada is presented （Also known as composite steel with structure）.

Jihada and jigane-Folded steel katana