Sori-The radian of the blade

What is Sori on a Japanese sword?

For enthusiasts who are just beginning to learn how to appreciate Japanese swords, the easiest thing to understand is the 'sori'.

Sori refers to the radian characteristics of the blade, and the blade with different radians can be customized to the forging cutter according to user preferences. Different factions of forging cutters also have their own characteristics in making blade radians, and with the passage of time, there is a trend of moving from the back of the blade to the front.

How was sori formed?

A previous article mentioned that before the 10th century, Japanese swords had no curve. In ancient times, Japanese swords were generally straight and double-edged, used for chopping and stabbing on the battlefield. With the improvement and development of combat, the curved blade was easier to draw and swing. At that time, swordsmen spent a lot of time thinking about how to make their swords cut better, which led to the creation of "sori". Without sori, straight-edged swords gradually became a symbolic weapon, such as ancient scholars who also carried swords as a symbol of identity. The swords may not have been sheathed from the time of purchase until the time of death.

What types of sori are there?

Muzori: It is called a sword with no or less curve and a tanto without curve. Commonly seen during the Kamakura period. Around the middle of the Edo period, swordsmanship based primarily on thorns also became popular, resulting in the production of many less curved tanto.



Sakizori: sakizori is a sori located closer to the tip of the blade than the center of the blade, often seen on katana during the Muromachi and Warring States periods. Compared to the koshizori-shaped tachi, which is advantageous for horseback combat, it is an appropriate sori for drawing and operating swords in foot combat.


Koshizori:Koshizori has the greatest curvature at the waist of the blade, with the curvature near the tip being smaller than the side near the blade shaft, and closer to an elliptical arc. It is common on tachi from the late Heian to early Muromachi period, such as Mikadukimunechika, which is a clear example.



Toriizori: The center of the toriziori is in the center of the blade, and the sori has almost the same positive arc from the blade tip to the blade shaft. Because it resembles the torii in front of the Japanese shrine, it is called a toriizori. It can be seen in the Yamashiro cave and the Yamato cave during the Kamakura period.

The so-called torii is a kind of pagoda-like structure in front of a Japanese shrine. It is usually two pillars holding up two crossbeams, the upper one often curving up at the ends and having a slightly rounded shape.
In addition, there is also Uchiizori, which curves slightly downward and is mostly found in tanto, so I won't go into that here.
When the actual Japanese sword is forged, the curve of the blade is not large, and the shape is close to that of a straight sword, but the blade is covered with clay and quenched in water, so that the temperature difference between each part of the blade in contact with water is different. The principle of heat expansion and cold contraction causes the blade to turn upward at the head and tail, thus deepening its curvature and giving rise to various types of sori, which are natural.


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