Blade construction: BLADE FINISH

Blade finishes are the final touches made to the surface of the blade that give the knife its character and good looks. These looks are the fruit of a creative mix of materials, imprints, light reflections and geometric shapes, as well as a testament to the mastery of blacksmiths and sharpeners. It’s the personal mark and signature style of a blacksmith. Knife buffs can usually tell only by the blade finish to which blacksmith’s collection the knife belongs.

The differences in these finishes are mostly aesthetic and have small bearing on the performance of knives. Certain kinds of finishes, however, give better performance or allow food to easily brush off the blade.

Kuro-uchi

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➨ Black / blacksmith’s finish

In Japanese, kurouchi means “first black” and this finish is also referred to as the “blacksmith’s finish”. The knife will retain the black scaly residue from the forging process which gives it a traditional look with a rustic charm. During the forging process, the knives are exposed to tremendous heat and flames so that the iron on the surface oxidizes and turns black. This look is somewhat robust and organic but it has a purpose – it will minimize the reactivity of a carbon steel knife and reduce the risk of corrosion. Another practical feature is also that it helps prevent food sticking to the blade. A kuro-uchi knife will continue developing a character or patina over several years of use, thereby increasing it unique quality and resilience.

👉 Neo-Kurouchi: this dark “patina” is applied to knives made of stainless less and its sole function is style and aesthetics.

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Tsuchime

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➨ Hammered prints

Tsuchime entails hammering the knife during the forging process and even incorporating some marks and dimples in the pattern that is visible on the top part of the blade. Air bubbles form in the dimples and help prevent food sticking to the blade. Because there is less surface that is in contact with food, there is also less friction and, consequently, less force is needed for cutting. To attain this textured finish that varies from make to make, blacksmiths use different hammerheads that are adjusted to the desired final effect.

 To etch cool patterns on the knives, they might even vary the frequency of applying the hammering marks. These can range in style and patterning from a light smattering of round circular indentations, to deep slashes in the blade, to a haze of triangular marks. One of the most stunning and eye catching are certainly Yu Kurosaki’s knives with distinctive hand-hammered finish that resembles water droplets, wind and other similar elements from nature. Nature has forever been the main source of inspiration for Japanese artisans. 

Tsuchime look is often combined with other finishes, such as kuro-uchi and damask, as well as kasumi.

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Migaki

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➨ Polished / mirror finish

Migaki is the polished finish on Japanese knives that gives them a minimalist and elegant look. The surface is thinned and polished to bring out the reflective and shiny nature of the blade. Polished finish causes the least damage to food cells during cutting and is best for the most delicate of tasks.

When the blade is forged in the san-mai style, a silver hair line finish is also created during the polishing process. It runs along the length of the blade just above its edge and marks the separation between the softer and the harder, core steel. 

👉 Some manufacturers opt for a cloudy polished finish, while others achieve an almost mirror-like polish which requires a little more maintenance. Polishing a katana until a mirror-like reflectiveness was achieved was of great importance for the samurai. The sword master Isao Machii says that a blade with a perfect mirror-like finish creates an optical illusion. If you hold it under just the right angle, the blade seems to disappear and prevents the opponent to see the actual length of the blade.  

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Suminagashi

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Damascus

Suminagashi or damascus finish looks like marbled layers of steel. With this technique, blacksmiths can really let their inner child out to play and create true works of art to feast our eyes on.

The term damascus is used for stunning water-like patterning that emerges when the central core of the blade (cutting edge) is made with a harder steel and wedged between more than two layers of milder, more pliable steel. The technique of suminagashi translates to “ink floating” and originates from the practice of paper marbling. Drops of oil paint were applied to water surface, creating swirling and multi-layered patterns that were then imprinted on paper.

Damascus in itself has no practical value but definitely adds aesthetic as well as actual value to the knife. It is undoubtedly the most known and appreciated look in Japanese kitchen knives.

Depending on the number of layers, the manner in which they are intertwined and, above all, the association with the elements of nature that the pattern inspires in us, many manufacturers give these patterns unique names, such as “amatsubu” or rain drops.

This look varies from one smithy to the next and includes everything from waves, spirals, circles, drops and similar eye-catching motives. When blacksmiths also throw into the mix layers with different materials, they can create true works of art, like the Rainbow Damascus collection by master Takeshi Saji.

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Nashiji

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➨ Matt finish

Nashiji in Japanese means “pear skin pattern” because it imitates the skin of the Asian pear. The top of the blade has a gently textured surface that is lightly dappled and slightly coarse. This doesn’t only give it striking looks but also has a practical function because it helps prevent food sticking to the blade. It also allows for a steady pinch grip.

The nashiji look is achieved with textured rollers. This look can be beautifully subtle and designed to look like winter snow, like in Yuki knives from Kato smithy, or it can be combined with more pronounced dimples, like in the Ginsanko series from Harukaze smithy

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Kasumi

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➨ Matt surface above the transition between the harder and softer steel

 

Kasumi roughly translates to “mist”, “cloud” or “haze” and refers to the hazy appearance of the soft steel/iron cladding, in contrast to the fine polished cutting edge. 
Even though kasumi is often used also in double bevel knives, it is especially characteristic of single bevel knives, mostly Yanagibas. 

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All in all, a knife is a very simple tool. Japanese blades with their distinctive looks, however, tell a unique story that weaves together many historical, cultural and anthropological threads. The look alone can tell us a lot about the culture and history of Japan, the approach of its people to craft, the fusion of craft with art and, first and foremost, the dedication of Japanese blacksmiths. The looks are therefore indicative not only of aesthetics, but also of dedication to tradition, quality, uniqueness and constant progress.

A knife is not only a tool but also a piece of art that combines many aspects of cultural and historical heritage. Isn’t it nice to know the rich and intricate story of our faithful kitchen assistant? After all, we hold it in our hands every single day.

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