There are numerous types of flaws (kizu) which can be found in Japanese sword blades. All detract from the artistic beauty of the blade and many render the blade non-functional and/or valueless. With the exception of broken or cracked kissaki (points), the following types of kizu can be found anywhere on the sword blade. Non-fatal flaws can be corrected by an experienced polisher whereas fatal flaws cannot be corrected and render the blade completely non-functional and generally of little or no value. It should be noted that even fatal flaws may be acceptable in a really old blade (early Kamakura Period) and/or in blades by noted smiths. An experienced collector/student of Nihonto must decide what is acceptable for their collection. While a blade may be seriously flawed and have little monetary value, it may still be a useful study piece to aid in learning the characteristics of particular smiths or schools of swordsmiths.
- BROKEN KISSAKI - This is a fatal flaw if the kissaki has been broken past the boshi (tempered area). If the break does not extend past the boshi, a good polisher may be able to reshape the kissaki.
- CHIPS - in the ha (edge) or kissaki (point) may or may not be fatal depending on whether they extend thru the hamon (tempered edge) or boshi (tempered point). A fatal flaw if chip extends past the hamon.
- FUKURE - Air or carbon pockets or blisters in the steel. Normally due to a bad weld between layers when blade was forged.
- HAGIRE - Cracks in the hamon (tempered edge) perpendicular to the edge. These are commonly VERY difficult to see, especially under poor lighting conditions. Hagire are fatal flaws.
- JI-ARE - Irregular or raised area; may be indicative of underlying blister or core steel being exposed due to excessive polishing.
- KARASUGUCHI - (Crow's Beak Hagire) - Crack in the boshi. These are fatal flaws.
- SHINAE - Ripples or wrinkles in the skin steel generally due to a bent blade having been straightened. These can be anywhere on the blade (shinogi-ji, mune, etc).
- UMEGANE - Region of blade filled with separate piece of steel; generally to fill in a major carbon or air pocket.
- MIZUKAGE - Cloudly line running diagonally from the ha (edge) near the ha-machi. This is commonly a sign that the blade has been retempered. While there were a few smiths that made mizukage deliberately, most often it is considered a flaw and indicator of a retempered blade. On retempered blades the hamon will sometimes stop in front of the ha-machi. Again, some smiths did this deliberately, but most commonly it is a sign of a retempered blade.
- SHINTETSU - Dark areas on the surface of the blade (ji or shinogi-ji) where the outer layer of steel has been removed and core steel shows through. This is normally a result of over polishing and indicates a "tired" blade.
- WARE - Horizontal "lines" (splits) generally due to a poor weld between layers of steel. Ware may occur anywhere on the blade (mune-ware, tate-ware, shinogi-ware, etc). These are very common.
- NIOI GIRE (interrupted hamon) - If the hamon (temperline) is interrupted or runs off the blade at any point, or off the boshi; it is a major, normally fatal flaw.
There are numerous other types of defects/flaws found in Japanese sword blades. Be certain to check CAREFULLY when examining a blade prior to purchase. Many flaws are quite subtle and can be very difficult to see (especially hagire - use a magnifying glass). Also be sure to sight down the back (mune) of the blade from the nakago (tang) to the kissaki (point) to determine if the blade is bent. Take your time when examining a blade as once the blade is purchased it is too late to complain about a newly found flaw.
Be sure to read Clive Sinclaire's article How to Recognize a Good Sword. He discusses some other points to consider in buying a Japanese sword.
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