How to Read Chikei (地景) and Its Types—The Beauty of Forging Workings Appearing in the Jigane (地鉄) of Nihonto and Judgment Criteria in Authentication

When observing the jigane of a Japanese sword, one can sometimes see fine linear patterns within the silvery luster visible to the naked eye. This is a phenomenon called chikei. Chikei is one of the important observation points in sword appreciation and serves as a clue in authentication to discern the technique, school, and place of origin of the swordsmith. This article systematically explains the definition, types, generation mechanism, and application in authentication of chikei.

What is Chikei——Definition and Visual Features

Chikei refers to "linear patterns (hataraki) of dark coloration (dark, subdued luster) that appear within the jigane." It is a phenomenon observed as fine striped patterns like dark, subdued lines on the surface of the jigane (the steel of the flat portion of the blade). Note that bright, white-shining linear hataraki such as kinkizu and inazuma (hataraki within the edge) are separate from chikei.

Chikei is one of the important patterns of jigane, alongside utsurimono and jinie, and constitutes a core element in the evaluation of jigane in Japanese sword authentication.

Visually, it appears as fine lines with a dark to dark gray, subdued luster, and its direction, length, distribution, and density determine the quality of chikei. Chikei becomes clearly visible only when a polisher (togishi) uses appropriate whetstones and polishing technique, so the quality of polishing greatly affects the visibility of chikei.

The Generation Mechanism of Chikei——The Relationship Between Metal Structure and Light

Chikei is the visualization through polishing of metallic structural characteristics formed during the sword-forging process.

The jigane of a Japanese sword develops layered structure through repeated folding and forging. The boundary surfaces of these layered structures, accumulation lines of impurities (mainly carbides and slag microparticles), or anisotropy in structure created by thermal stress during hardening appear as differences in light reflection after polishing. This is what is perceived as chikei.

Specifically, the following mechanisms are involved.

• Difference in reflection due to structural differences in forged layers. The boundaries of layers formed by repeated folding and forging sometimes have slightly different carbon concentration and particle density compared to adjacent structure. This difference appears as a subtle variation in light reflectivity, forming chikei.
• Structure following the "flow" of forged skin. In many cases, the direction of chikei tends to align with the direction of the "flow (forge flow)" of the iron during forging. Chikei flowing along the long axis and diagonal directions of the blade indicates the directionality of forging.
• The relationship between chikei, nie, and nioi. Chikei sometimes appears independently, but often appears in combination with jinie. While jinie is "point-like luster," chikei is "linear luster," and their coexistence creates a richer appearance in the jigane.

Types and Shape Classifications of Chikei

Chikei can be classified into multiple types based on differences in shape, direction, and distribution.

• Straight chikei: Chikei that appears linearly along the long axis of the blade or following the direction of forging. It tends to be frequently seen in Soshu-den swords and indicates traces of powerful forging.
• Curved chikei: Chikei that appears somewhat bowed or curved. In Bizen-den swords, chikei often appears curved along the wood-grain-like flow of itame jihada.
• Branching chikei: Chikei with complex shapes that split into two or three branches partway. It tends to appear in swords where complex layered structures have been formed through advanced repeated folding and forging, and is sometimes regarded as evidence of sophisticated forging technique.
• Net-like chikei: A phenomenon where multiple chikei intersect and appear in a net-like pattern. Chikei combined with the Yamato-den mokume jihada resembles this shape.

Characteristics of Chikei by the Five Great Schools

There are differences in trends in how chikei appears among the five great centers (Go-kaaden) of Japanese sword production.

• Bizen-den: In Bizen-den jigane, which is based on itame jihada, fine straight-line chikei tend to appear in the masame portions. Chikei often runs parallel to the hamon direction, giving an overall orderly impression. The moisture (urushi) of the jigane and the fineness of the chikei are important indicators in evaluating Bizen-den.
• Soshu-den: Soshu-den swords tend to display coarser chikei. In the jigane of works by Masamune and Sadamune and others, which shows "nie rising abundantly," chikei can also appear powerfully and large. Soshu-den chikei is praised as "rich in hataraki."
• Yamashiro-den: In Yamashiro-den, where fine itame jihada is beautifully compact, chikei tends to appear relatively fine and uniform. The chikei of Awatataguchi-lineage jigane is considered precise and elegant, with high evaluation in authentication.
• Yamato-den: In Yamato-den swords based on masame jihada, long straight-line chikei tend to appear along the direction of forge flow. The chikei seen in Tekaki-ha and Senjuin-ha swords gives a bold and rustic impression.
• Mino-den: In Mino-den, where itame and masame are mixed, chikei tends to appear more irregularly than in other schools. While Mino-den is sometimes praised as "rough work," there are masterpieces where the boldness of chikei is considered attractive.

Polisher Technique and Bringing Out Chikei

Chikei "exists" in the sword from the start, but it is the polisher's technique that makes it clearly visible. The choice of whetstone, the angle of polishing, and the finishing method can greatly change how chikei appears even on the same sword.

There is a process called "hadatate" as a technique for polishers to bring out chikei. It is a method that applies special polishing operations after the finish stone to make the jihada (itame, masame, etc.) and chikei of the jigane stand out clearly.

Attempting to polish out chikei excessively risks making the blade too thin. Polishers are required to make sophisticated judgments to bring out the beauty of chikei to the maximum while maintaining a balance that does not damage the blade's original thickness and shape.

Evaluation of Chikei in Authentication

In sword authentication, chikei is used as a material for the following judgments.

• School and place of origin identification. Since the shape, density, and directionality of chikei show tendencies specific to each school, when combined with other observation points (hamon, jihada, nakago), it becomes a clue to narrow down the place of origin and school of the sword.
• Evaluation of forging quality. Uniform and orderly chikei indicates skill in experienced repeated folding and forging. Conversely, chaotic or uneven chikei may indicate rough forging or material issues. However, since some schools characterize "rough chikei," interpretation within the school's context is necessary.
• Assistance in authentication. Even sophisticated counterfeit swords have chikei that is structurally different from that formed by genuine repeated folding and forging, so when combined with X-ray and high-magnification microscope observation, it becomes supplementary material for authentication.

Conclusion——The Story of Sword Forging Told by Chikei

Chikei is where "the memory of forging" is inscribed on the surface of the sword. Dozens of folds in repeated forging, temperature management of the furnace, the touch of the craftsman's hands——all of this is recorded in the metal structure and appears as patterns of light through the polisher's technique. The skill of reading chikei deepens appreciation from simply enjoying the beauty of the sword as a visual impression to the stage of "reading" the process of its creation. In the appreciation of Japanese swords, attention to chikei is an important step toward approaching the essence of sword culture.