Edo Shinto Blade Morphology: From Keicho Robust Forms to Horeki Restrained Elegance

Three Phases of Edo Shinto Morphology

Shinto (New Sword period, c. 1596 onward) blade morphology evolves through three distinct phases. Keicho-Kan'ei (1596–1643): robust, motohaba 3.0–3.4 cm, sakihaba/motohaba ~70–76%, moderate sori 0.8–1.5 cm. Joo-Hoei (1652–1710): the Genroku-era "swagger" — motohaba expanding to 3.2–3.6 cm, tip ratios 72–80%, fuller cross-section ("nikubuto"), chu-to-ya-ō-kissaki. Shotoku-Meiwa (1711–1771): "shimari-sugata" — motohaba contracting to 2.8–3.1 cm, tip ratios falling to 65–72%, ko-to-chu kissaki, thinner kasane at 0.65–0.75 cm.

Regional Variation: Edo, Osaka, Kyoto

Edo-Musashi smiths favor balanced, practical proportions with moderate sori and chu-kissaki. Osaka shinto — most prominently Sukehiro and Shinkai — epitomizes Genroku robustness: broad-bodied, full-cheeked blades with distinctive sudareba hamon. Kyoto-Yamashiro smiths tend toward the more refined, slender traditions inherited from koto Yamashiro-den: elegant narrow forms with refined ko-itame hada.

Hamachikado as a Dating Indicator

The geometry of the hamachi (blade notch at blade/nakago junction) shifts between koto and shinto: koto hamachi tends toward a gently rounded angle, while shinto shows increasingly sharp right-angle geometry. This subtle morphological indicator, linked to changes in quenching and clay-application technique, helps experts distinguish old-sword from new-sword attribution even in unsigned pieces where stylistic evidence is ambiguous.