Japanese swords: types, shape, steel grain and hamon

Early chokuto are largely straight. Later tachi have curvature and are normally suspended with the edge down. Katana are carried edge-up in the sash, while wakizashi and tanto are shorter forms; a straight, double-edged ken is another type. Some surviving blades were shortened or remounted, changing the relationship between their present form and original use.

Traditional manufacture draws on steel such as tamahagane and materials with differing carbon content. Repeated heating, hammering and folding consolidate the steel and help adjust its carbon content before the blade is shaped. Some constructions combine harder outer steel with a softer core, with methods varying by period, school and maker. The worked material contributes to the grain visible in the polished surface.

Hardening

Hamon is connected with hardening. The Sword Museum’s process account describes a thin clay coating where the edge is to harden and a thicker coating elsewhere, followed by heating and rapid cooling. The differing coverage affects cooling and hardening across the blade.

Polishing and other crafts

Polishing first establishes the blade’s form, then progressively reveals its steel grain and hardened edge. The hamon is not a decorative wave carved into an otherwise finished blade. Scabbards, hilts and metal fittings require other specialists alongside the smith and polisher.

Form, grain and hamon

Sugata concerns the blade’s overall proportions, curvature and point. Jigane and jihada concern its steel and visible grain; hamon follows the hardened edge area. The mounting has its own decoration, separate from the grain and hamon of the blade.

Okanehira’s size and inscription

The Tokyo National Museum’s twelfth-century Okanehira has an imposing blade, 89.2 cm long with 3.5 cm curvature. The catalogue contrasts its long signature with Kanehira’s more usual small two-character signatures.

Changing blade forms

Curved tachi developed after earlier straight blades, with further changes through the Heian and Kamakura periods. Nanbokucho makers produced broad, long tachi, often with thinner blades to reduce weight. In late Muromachi, collective fighting on foot accompanied the wider use of edge-up katana; many were shorter, with stronger curvature towards the point.

Shintō and shinshintō

Edo and Osaka became centres for early modern shinto production. Swords served as weapons, marks of samurai status and objects of craftsmanship. From the late eighteenth century, Suishinshi Masahide and other smiths promoted a return to older blades as models, contributing to the revival associated with shinshinto.

Modern restrictions and preservation

The 1876 prohibition on ordinary public sword-wearing sharply reduced demand; it did not prohibit preserving swords. Gassan Sadakazu and Miyamoto Kanenori became Imperial Household Artists in 1906, while subsequent military demand also sustained prewar production. A manufacturing ban after Japan’s defeat in 1945 interrupted the craft. Its postwar resumption established a different basis: military demand had vanished, and production required approval on grounds of artistic value. The NBTHK, founded in 1948, worked to preserve blades and skills. It established its restored tatara operation in 1976 and resumed smelting in 1977 to supply steel for traditional swordmaking.