Japanese swordsmith achieved early technical mastery of steel-making and swords of excellent quality were made during the 8th century. Even the earliest examples featured a densely forged laminated structure of as many as 10,000 layers alternating in higher and lower carbon content hammered to exceptional toughness. The cutting edge of the Japanese sword has a crystalline structure, and since this is locked into a tough yet somewhat softer body, the sword has considerable flexibility.
Early Japanese furnaces were small and did not allow the total removal of slag as did the larger, more powerful tatara furnaces of the mid-18th century. But the existence of traces of slag, along with the intensive process of hammering and repeated folding and welding of the steel gave Japanese swords one of their unique qualities-a texture like wood grain, resulting from the small extrusions of slag beaten down to extremely fine layers.
The final stage in sword making was tempering and polishing, both done with techniques unique to Japan, and resulting in an accentuation of wave-like patterns known as hamon (temper patterns) on the sword's surface. One of the most beautiful features of a Japanese sword, the hamon also allow connoisseurs to identify a sword's origin. Each of the 200 or so schools of swordsmith-artists in Japan had identifiable blade characteristics. File marks (yasurime) on the tang (nakago) of the blade, the shape, and style of finishing, texture, tempering and colour of steel are all taken into consideration in establishing the provenance of a sword. The signature of the smith is also often chiselled onto the tang.
While high-quality sword-making goes back to the 8th century, the golden age of the swordsmith in Japan was from 1050 to 1400. The history of sword making can be roughly divided into the Koto (Old Sword) period, from the 10th to the end of the 16th century and Shinto (New Sword) period (17th century onwards), when provincial lords (daimyo) encouraged a revival of the sword art. Blades of the new period are generally regarded to lack the grace of earlier swords, but many had exquisite temper patterns. In addition to the katana and tachi swords used by warriors, sword connoisseurship also encompasses wakizashi blades, spears (yari), and halberds (naginata), as well as the sword guards (tsuba) and metal fittings for swords.
Japanese armour was flamboyant as well as functional. The o-yoroi style of armour employed from the 9th to 14th centuries was designed for combat on horseback and consisted of numerous flexible segments joined by richly coloured cords. An iron helmet topped the armour, with tall stylised horns (kuwagata). Lavishly decorated saddles, bows and arrows, and miscellaneous weapons and colourful banners completed the warriors's inventory. The style and colours of the warrior's accouterments were designed to proclaim to the enemy the proud identity of his clan. By the 14th century, lighter types of armour (domaru) gradually replaced the o-yoroi. The introductions of firearms in the 16th century necessitated the development of a new style of armour (tosei gusoku).
The uniqueness of the Japanese sword lies in the technical innovations devised by the Japanese in an effort to resolve the three conflicting practical requirements of a sword: unbreakability, rigidity, and cutting power. Unbreakability implies a soft but tough metal, such as iron, which will not snap with a sudden blow, while rigidity and cutting power are best achieved by the use of hard steel. The Japanese have combined these features in a number of ways which have given their swords a very distinctive character.
First of all, most Japanese blades are made up of two different metals: a soft and durable iron core is enveloped in a hard outer skin of steel which has been forged and reforged many times in order to produce a complex and close-knit crystalline structure. Seconds, the cross-section, widening from the back to a ridge on both sides, then narrowing to a very acute angle at the edge, combines the virtues of thickness for strength and thinness for cutting power.
Third and most important of all, a highly tempered edge is formed by covering the rest of the blade with a special heat-resistant clay and heating and quenching only the part left exposed. The result is a steel which is even harder then the rest of the outer skin and can take a razor-sharp edge. A fourth feature, the distinctive curve away from the edge, owes its origin to another practical demand: the need to draw the sword and strike as quickly as possible and in a continuous motion. Where the sword itself forms part of the approximate circumference of a circle with its centre at the wearer's right shoulder and its radius the length of his arm, drawing from a narrow scabbard will naturally be easier and faster than with a straight weapon.
But to the Japanese specialist the beauty of a sword lies in more than just its fulfillment of practical requirements or its almost mechanical perfection of finish and cleanness of profile. The Japanese swordsmith has given his product a number of features which, although they may have a strictly practical origin, have been elaborated far beyond the simple requirement of hard-wearing efficiency in slaughter. One example of this is the forging of the outer skin, a process necessary to produce steel of adequate purity and hardness: this has been done in a multitude of different ways so as to obtain a wide variety of distinct grains in the surface of the blade.
But it is the tempering process which has received the most careful attention. The heat-resistant clay is wholly or practically scraped away from the area of the edge in a seemingly inexhaustible range of outlines resulting in an enormous number of patterns of hard crystalline steel which guarantee that no two swords will ever be the same: and yet these outlines have no practical function beyond the simple requirement that the edge must be tempered in one way or another.This site contains information about Japanese Swords, signatures, military, history, care and cleaning, polishing and sword making.
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