Japanese Knife Finishes

Kurouchi (黒打ち, “black forged”)

The black forge scale is left on the blade. Rustic, honest, less work.

When the smith forges and heat treats the blade, a black oxide layer grows on the surface. On a kurouchi knife the smith only grinds the bevel and leaves the rest black. You can see the hammer and forging texture under it. The black layer protects the upper part of the blade a little against rust, and it hides small scratches.

Good to know: the black wears off slowly with use and washing. That is normal and part of the look. Don’t scrub it with abrasive pads. The polished bevel under it is still carbon or iron, so dry it after use.

At JNS: Munetoshi (the best example of kurouchi I carry) · Shigefusa

Nashiji (梨地, “pear skin”)

A matte, grainy surface like the skin of a Japanese nashi pear.

Between kurouchi and polished. The forge scale is mostly taken off and the surface is left rough and matte, often dark grey. Sometimes you see it together with kurouchi at the spine (kurouchi nashiji). The grainy surface hides scratches very well.

Good to know: very easy to live with. It gets a nice patina over time. When you thin the knife on the stone, the area you grind becomes shiny, so the nashiji slowly moves up from the edge over the years.

At JNS: Tadafusa (the best example of nashiji I carry) · Tanuki

Kasumi (霞, “mist”)

The classic Japanese finish. Soft iron goes misty, the hard steel shines.

The soft iron cladding turns cloudy and grey like mist, and the hard steel core at the edge stays brighter. Between them you see the kasumi line, the place where the two are forge welded. A good kasumi shows you how the knife is made.

There are two ways to get it. A kasumi can be sandblasted, which is fast and gives an even matte look. It also hides unevenness and scratches on the blade. The best is a hand finish on natural stones, ending with Uchigumori finger stones. That gives the iron a deep, soft mist and makes the kasumi line clear. This is how I finish my own JNS Kokorozashi knives in the workshop.

Good to know: scratches from cutting boards and sharpening show more than on kurouchi. The good news: you can bring kasumi back yourself with a natural stone and Uchigumori finger stones, but only if the knife is not sandblasted.

At JNS: JNS Kokorozashi (Uchigumori finish by me) · Shigefusa · Toyama

Migaki and mirror polish (磨き, “polished”)

A bright, clean polish. Satin or all the way to mirror.

Migaki means the whole blade is polished bright. It can be a satin shine or a full mirror. It looks clean and elegant and is easy to wipe clean. You don’t see the kasumi line as much as on a stone polish. Full mirror is mostly seen on high end single bevel knives and honyaki.

Good to know: every small scratch shows on a bright polish. It will not stay perfect when you use it, and that is fine. A mirror is very hard to bring back at home. Most people let it turn into a soft satin with time.

At JNS: Yoshikazu Tanaka

Tsuchime (槌目, “hammer marks”)

Hammer dimples on the upper part of the blade.

After forging, the smith hammers a pattern of dimples into the side of the blade with a round hammer. It is for the look. It shows the knife is hand forged. Many people think the dimples stop food from sticking. They don’t. Food release comes from the geometry of the grind. You see tsuchime on kurouchi, nashiji and polished knives.

Good to know: easy care, hides scratches well. Like nashiji, the dimples slowly disappear from the edge up when you thin the knife over many years.

At JNS: Tadafusa · Tanuki

Kitaeji, Damascus, Tamamoku, Suminagashi

One finish, many names. Folded layers in the cladding that show a pattern.

The cladding is forged from layers that are folded many times. When the blade is polished, the layers come out as a pattern, often like wood grain or flowing water. It is the same idea whatever the name on the listing:

• Kitaeji (鍛え地): what Shigefusa calls it.
• Tamamoku (杢目, wood grain): what I call it on my JNS Kokorozashi knives.
• Suminagashi (墨流し, floating ink) or Damascus: what many other makers and shops call it.

On a clad damascus knife the core steel at the edge is the same as on a plain clad knife, so it cuts the same. The pattern is about the look and the work behind it.

Damascus without cladding. Damascus can also be made with no cladding at all. The whole blade is folded steel and it is hardened like a honyaki, with clay and a hamon. These are rare and a bit special. My JNS x Wakui Dama Honyaki are made like this: damascus steel by Achim Wirtz from 125SC and C80 with 180 layers, forged and water quenched with a hamon by Wakui, then sharpened, polished and etched by me.

Good to know: when you sharpen and thin, the pattern gets lighter where you grind. Treat it like kasumi: polish on natural stones and finger stones and the pattern comes back, often even nicer. Never sand the sides. You will only make it grey.

At JNS: Shigefusa · JNS Kokorozashi · Toyama · Yoshikazu Tanaka · JNS x Wakui Dama Honyaki

Honyaki (本焼) and hamon (刃文)

One steel, quenched with clay like a Japanese sword.

A honyaki has no cladding. The whole knife is forged from one piece of high carbon steel, often White 1 or White 2. Before the heat treatment the smith paints a clay mix on the blade: thick on the spine, very thin at the edge. Then the blade is heated and quenched, in water (mizu honyaki) or oil (abura honyaki). This is the same way Japanese swords are made.

Under the thin clay the edge cools very fast and gets very hard. Under the thick clay the spine cools slower and stays softer and tougher. The line between the two is the hamon, and every one is different. The water quench is very risky, blades can crack or warp, and even master smiths lose some. That is why honyaki is rare and expensive.

How much of the hamon you see depends on the polish:

• Mirror polish: shiny and impressive, but the hamon is often only visible at an angle.
• Stone polish (like a sword): done with natural stones and finger stones. Hazuya (刃艶) makes the hard edge area white and misty, jizuya (地艶) makes the body darker. Now the hamon and its activity really come out.

Good to know: the whole blade is hard steel, so sharpening and polishing take more time than on a clad knife. Be careful with twisting and hard food. A honyaki edge is hard but not forgiving.

At JNS: Ikeda White 1 honyaki · Toyama · Munetoshi