Introduction
Jihada (地肌) refers to the visible surface grain pattern found on a Japanese sword (nihontō, 日本刀), created during the forging and folding of steel. This pattern is a result of multiple layers of steel being repeatedly folded, forged, and polished, revealing unique textures on the surface of the blade.
The appearance of the jihada is a key indicator of the swordsmith’s skill, the quality of the steel, and the tradition of the sword’s forging school (den, 伝). Different schools developed distinctive jihada patterns, which help historians and collectors identify the origins of a blade.
This guide explores the formation, types, and significance of jihada, along with how it is used to classify Japanese swords.
1. Formation of Jihada
Jihada is created during the folding process (orikaeshi tanren, 折り返し鍛錬) of steel. Traditional Japanese swords are forged from tamahagane (玉鋼, “jewel steel”), which consists of high-carbon and low-carbon steel sections.
Key Steps in Jihada Formation:
- Folding the steel multiple times (usually between 10–15 folds) to remove impurities and homogenize the carbon content.
- Forging the steel layers together, forming a composite structure.
- Polishing (togishi, 研師) to reveal the unique surface patterns.
The number of folds and the forging technique determine whether the jihada appears fine, rough, straight, or swirling.
2. Types of Jihada (地肌の種類, Jihada no Shurui)
Jihada patterns are classified based on the grain formation and texture visible on the blade’s surface. Different swordsmithing schools developed distinct styles of jihada.
A. Masame-hada (柾目肌) – “Straight Grain”
- Masame-hada has a tight, straight-grain pattern running parallel along the blade.
- Often found in Yamato-den (大和伝) swords.
- Provides superior durability, making it ideal for cutting through armor.
B. Itame-hada (板目肌) – “Wood Grain Pattern”
- Itame-hada resembles natural wood grain with wavy or irregular swirls.
- Common in Bizen-den (備前伝) and Mino-den (美濃伝) swords.
- Aesthetic appeal: Highly regarded for its natural, organic appearance.
C. Mokume-hada (杢目肌) – “Burl Grain”
- Mokume-hada forms circular, swirling patterns similar to burl wood.
- Found in Sōshū-den (相州伝) and high-quality Bizen blades.
- Extremely difficult to forge, requiring exceptional skill.
D. Ayasugi-hada (綾杉肌) – “Wavy Grain”
- A highly distinctive, undulating wave pattern.
- Characteristic of the Gassan School (月山派), especially from the Edo period onward.
- Recognized for its dramatic, rippling beauty.
E. O-Itame-hada (大板目肌) – “Large Wood Grain”
- A coarser, more pronounced version of itame-hada.
- Common in older swords, particularly from the Kamakura and Nanbokuchō periods.
- Shows bold, open steel patterns with larger textures.
F. Nashiji-hada (梨地肌) – “Pear Skin Grain”
- Very fine, almost invisible grain, resembling the surface of a pear’s skin.
- Found in highly refined blades from the Shintō (新刀) period.
- Indicates a superior forging technique with an extremely fine steel structure.
G. Hada-tsumi (肌積み) – “Dense Forging”
- Describes extremely tight, fine jihada, often found in Hizen swords (Hizen-to, 肥前刀).
- Almost resembles a polished surface with minimal visible texture.
H. Matsukawa-hada (松皮肌) – “Pine Bark Grain”
- Appears as irregular, dark patches mixed within the grain, resembling pine tree bark.
- Seen in Sōshū-den and some experimental koto blades.
- Considered an exotic and rare jihada pattern.