Japanese swords are masterpieces created through a grueling process of folding and tempering. Over centuries of history—and sometimes the scars of combat—it is perfectly natural for various imperfections to appear. As long as they do not compromise the structural integrity or the functional beauty of the blade, minor flaws do not necessarily diminish a sword’s value. In fact, certain “flaws” are actually defining characteristics of specific prestigious forging schools.
The following are the primary categories of sword imperfections:
1. Ha-gire (Edge Cracks)
Ha-gire are cracks appearing on the cutting edge.
- Critical Risk: If the crack is perpendicular to the blade, it is a fatal flaw as the sword is highly prone to snapping at that point.
- Variations: If the crack is slanted, the risk of breakage is slightly lower.
- Ha-karami: A crack running nearly parallel to the edge.
- Karasu-guchi (Crow’s Beak): A Ha-gire occurring at the Kissaki (tip), resembling the open beak of a crow.
2. Ha-kobore (Nicks and Chips)
These are chips on the edge with a rounded base and no sharp internal angles.
- Note: Because they lack sharp angles, the cracks are unlikely to spread further. While still a defect, a blade that chips without shattering often serves as proof of high-quality steel and proper heat treatment.
3. Ha-shimi (Staining/Dullness)
This occurs when the carbon within the steel is not distributed evenly. Certain sections of the blade may appear particularly dark, dull, or lacking the crystalline luster of the surrounding steel.
4. Fukure (Blisters)
During the folding process (Shita-kitae), if air or impurities are trapped between the layers of steel, they fail to weld completely. This creates an internal air pocket. Over centuries of polishing, these bubbles may become exposed on the surface, affecting the blade’s visual harmony.
5. Umekane (Plugged Metal)
This refers to a small piece of metal that has been “embedded” into the blade. It represents a repair where a craftsman has deliberately filled in a deep flaw or pocket with matching steel to mask its appearance.
6. Ware (Lamination Cracks)
Ware are cracks that occur when layers of steel do not weld perfectly during forging, appearing as lines parallel to the edge.
- Acceptability: If minor, they are generally acceptable. For blades with a prominent straight-grain texture (Masame-hada), these lines are often a natural part of the grain rather than a flaw.
- Mune-ware: A lamination crack occurring on the Mune (the back/spine of the sword).
7. Shina (Wrinkles/Creases)
These are tiny “wrinkles” on the blade’s surface.
- Categorization: They are named based on their location: Ha-shina (on the edge), Ji-shina (on the surface), or Mune-shina (on the spine).
- Mukade-shina: When multiple wrinkles cluster together, they are called “Centipede Wrinkles.”
8. Yaki-otoshi (Tempering Drop)
This is when the Hamon (temper line) stops prematurely above the Nagago (tang), leaving a small section of the blade near the handle untempered.
- Verdict: Since this area of the blade is rarely used for cutting, Yaki-otoshi is not considered a major defect.
- Yaki-dashi: If the Hamon extends slightly into the tang, it is called Yaki-dashi. This is not a flaw, but a prized characteristic of certain schools (like the Osaka Shinto tradition).
9. Mizukage (Water Shadow)
A faint, hazy reflection or shadow found near the start of the tempered edge. It shares a similar cause with Yaki-otoshi—often appearing as a result of the blade not being fully submerged or reacting differently during the quenching process.
Expert Consultation If you are unsure whether your blade has a flaw or a unique school characteristic, please upload high-resolution photos of your blade in the comments section. Our professional master smiths will provide a complimentary evaluation to resolve your doubts.Alternatively, you can contact our experts for assistance at the following email address: Ab Sword Master([email protected])