Single/ Double-edged knife structure

"KIREAJI's guide to single and double-edged knife structures offers insights into their unique characteristics and impact on cutting techniques.

Single-edged knife structure

Single-edged knife structure

Japanese kitchen knives are renowned for their exquisite craftsmanship and exceptional quality. These culinary tools are characterized by their single-edged design, which features a slightly indented back and a meticulously crafted blade surface.

Types of Japanese Kitchen Knives

Japanese kitchen knives can primarily be categorized into two types, each with its own unique manufacturing process and characteristics:

  • Kasumi (Awase) Knives: These knives are a fusion of soft iron and steel, with soft iron being iron that contains less carbon content than steel. Traditionally, Kasumi knives were named for the soft iron part of the blade, which had a misty or hazy appearance (Kasumi in Japanese means "mist"). However, modern Kasumi knives often boast a polished, mirror-like finish. Known for their affordability, ease of handling, and sharpening convenience, Kasumi knives are a popular choice among culinary professionals and enthusiasts alike. Yet, it's worth noting that over years of use, the softer steel might warp or distort due to the tension exerted by the harder steel.

  • Honyaki Knives: The production of Honyaki knives is akin to the crafting of traditional Japanese swords, employing a method that uses steel exclusively, without the incorporation of soft iron. Honyaki knives are celebrated not only for the stunning sword-like patterns they exhibit but also for the high level of skill and precision required in their creation. Comprising entirely of hard steel, Honyaki knives demand patience and expertise to sharpen effectively.

Honyaki Japanese knife made in Sakai

Honyaki

Honyaki knives, crafted from a single metal piece through a forging process similar to Japanese swords, are distinguished by their resilience against distortion and lasting sharpness. Their unique manufacturing method, which creates varying hardness within the same steel piece, makes them particularly suitable for professional chefs seeking precision and durability in their culinary tools.

Honyaki
Awase Japanese knife made in Sakai

Kasumi (Awase)

It is a forged knife. This is the most common type. The back is steel and the front is base metal, joined together front and back. For this reason, you can see a line on the blade (cutting edge) part. This line is the boundary between steel and base metal. The pattern of this line also changes depending on the forging method and the type of steel.

Double-edged knife structure

Double-edged knife structure

Traditionally, Western and Chinese knives have been characterized by their double-edged design, featuring symmetrical angles on both sides of the blade—a stark contrast to the single-edged nature of Japanese knives. However, the unique Japanese technique of Kasumi Hari Awase, a method that combines soft iron with hard steel, has gradually been incorporated into the manufacturing of Western-style kitchen knives in Japan.

Kasumi Hari Awase: A Blend of Durability and Precision

The integration of Kasumi Hari Awase in Western-style knives brings several distinct advantages:

  • Enhanced Resistance: Kasumi Hari Awase knives exhibit greater resilience against cracking compared to full steel (Zenkou) knives. This attribute makes them a durable choice for various culinary tasks.

  • Flexibility: While these knives are less prone to cracking, they do tend to bend more easily. This characteristic requires careful handling and maintenance to preserve the knife's integrity.

  • Sharpening Considerations: Sharpening Kasumi Hari Awase knives demands attention to detail. It's crucial to sharpen not just the cutting edge but to ensure that the steel part of the blade maintains contact with the food. Failure to do so may result in a knife that is technically sharp but fails to cut effectively.

When sharpening a double-edged Kasumi Hari Awase knife, it's essential to visualize the cross-sectional structure of the blade. This approach ensures that both the soft iron and the hard steel components are honed properly, maintaining the knife's balance of sharpness and durability.

 

Zenkou(All steel)

In contrast to knives made by combining a hard metal core with a soft metal overlay, this term refers to knives made using only one piece of hard metal to construct the blade. Generally, when a knife is forged from a single piece of metal, it is often referred to as "Honyaki"
Therefore, this section specifically addresses knives made through die-cutting with a press. In an all-steel knife, the entire blade is composed of a hard, sharp material, eliminating the need to sharpen both sides equally, as is the case with a double-edged matching knife. This allows for a versatile sharpening method such as the "single-edged style."

Kasumi Hari Awase

This term refers to knives made by layering multiple metals together, as opposed to knives constructed from a single piece of metal. The soft metal in the layered construction absorbs the impact the knife receives, consequently enhancing overall durability. Many of these knives feature a three-layered structure with a hard metal core sandwiched between soft metal layers. Such knives are sharpened to ensure that only the hard metal forms the cutting edge. The hard metal forming the cutting edge is called the "Hagane," while the layered soft metal portion is referred to as the "Jigane."

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The Art of Forging: Crafting the Finest Japanese Knives

The article highlights the superior sharpness of traditional Japanese forged knives, attributing their quality to techniques derived from sword-making. These knives, including types like "Honyaki" and "Kasumi," benefit from a handcrafted process that ensures a denser structure and a finely tapered edge, outperforming many Western knives in sharpness

Forged knives are sharp!
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The Art of Honyaki Knives: Mastery in Steel

The article discusses the allure and cost of Honyaki knives, highlighting their rarity, exceptional sharpness, and the labor-intensive process required to make them, which justifies their high price, ranging from 100,000 to 300,000 yen. Despite the cost, their quality makes them sought-after by culinary professionals.

The Art of Honyaki Knives: Mastery in Steel