What are Japanese knives made of?

The foundations of Japanese chefs knives are the materials used. Besides the unique design, they have specific forging methods, different metals and handles. All this contributes for your knife overall quality and how it adapts to your needs.

Forging methods

The two main forging japanese forging methods area honyaki (one material) or kasumi (two materials). 

Honyaki

Honyaki, or "true-forged", are made entirely from steel. Usually made of blue or white steel, if the first is used it can have wood grain or damascus. The forging temperature avoids most of the grain growth and makes the blade more resistant to hammering. Afterwards, the spine is coated with a thick layer of clay. The process of heating and cooling and the thicker blade avoids cracking. The more resistant material makes it difficult to polish. 

The finished product is a knife with a shock absorbing spine and a hard sharp edge, perfect for slicing raw fish. Sharpness is kept for longer as the blade material is harder. This process of production lead to less consistent and more expensive knives. 

Pros

• Harder blade
• Keeps edge longer, less sharpening
• Good for slicing raw fish

Cons

• More difficult to use and maintain
• Expensive
• Less consistent production

Kasumi

Kasumi are made from steel and softer iron forged together, forming a misty line between the two materials. The edge is steel, giving it the sharpness of a japanese knife, and the top part iron, which makes it less stiff.

This knife is prone to corrosion, but this can be avoided by cleaning and drying the blade right after every use. If stainless is used in the exterior or top part, it makes the knife resistant to corrosion while keeping the traditional cutting edge. This knife is easier to maintain, but softer and in need of more sharpening. Higher grade kasumi are ofter referred as hon-kasumi.

Pros

• Cheaper
• Easier to maintain
• Stainless steel can be used to prevent corrosion
• More consistent product

Cons

• Softer material
• Need to be cleaned and dried after using to avoid corrosion
• Needs frequent sharpening

Blade Material

A big part of what makes a japanese knife is the steel used in its production. The different materials used give some characteristics to the knife, maintained only with a correct production process. Steel can be divided in three main categories: stainless steel, carbon steel and powdered high speed tool steel. It is important to know their features in order to choose an adequate knife to your needs.

Elements in the steel

Carbon and Chromium are the main elements in steel. But other elements can be added in order to make improve the steel characteristics. This information is useful to understand the different types of steel. All increase hardness, strength and toughness.

• Chromium (Cr): rust and wear resistance, tensile strength.
• Carbon (C ): edge retention, tensile strength. 
• Tungsten (W): wear resistance.
• Molybdenum (Mo): rust resistance.
• Cobalt (Co): high temperature resistance, intensifies other elements.
• Vanadium (Va):  wear resistance.

Stainless steel

Stainless steel has over 11% of chromium in it's composition, which makes it rust resistant. Stainless steel was once an unvalued material for its bad cutting performances and quick dull. Today, due to improvements in the materials and techniques, this is no longer true.

This steel became widely used because of its easy maintenance and easy sharpening process. It can hold an edge quite well. High carbon stainless steel even have similar qualities to carbon steel. Beware that even stainless steel can rust if left wet for long periods. To maintain your knife in good condition be sure to dry it after washing.

Pros

• Easy sharpening and care
• Resistant to corrosion and discoloring

Cons

• Can rust if wet for long periods
• Acceptable edge retention

AUS-8: rich in molybdenum, produces a standard stainless steel knife good for beginners. It's easy to sharpen, durable, resistant to corrosion and cheap. 

VG-10: it incorporates 1% carbon, 15% chromium, 1.5% cobalt, making it a great quality knife. The main characteristics are sharpness, durability and edge retention. Some damascus blades are made of this steel.

VG-1: basic stainless steel, with high hardness, rust resistant and good edge. It is particularly rich in carbon and molybdenum.

Gingami No.3: stainless steel with characteristics similar to carbon steel.

Friodur: an old type of stainless steel that was surpassed by newer types, but it is still a reasonable choice. The steel is cooled by freezing in a process called ice-hardening. This makes the steel harder, which makes it flexible, stain resistant and sharp.

Carbon Steel

It's an alloy made of iron and carbon that originates blades with excellent cutting performances due to its sharpness. It holds a good edge and is easy to re-sharpen. On the down side, it can rust and discolor easily, needing some extra care.

This blade should never be left wet and may require wiping and drying even during cooking to prevent discoloring when cutting foods such as onions. Even with proper care it can suffer a little corrosion, but this does not affect the cutting performance.

When stored, it should be coated with proper oil and kept in the original paper cover to protect it from rusting. This is the right blade for professionals who spend long hours in the kitchen and don't mind the extra effort spent in caring for the knife.

People who look for excellent cutting performances but can't handle the exhaustive maintenance of carbon steel should buy Cladding blades. These are made from a carbon steel core coated with soft stainless steel. Only the core is prone to corrosion, which facilitates maintenance.

Pros

• Excellent cutting performance
• Great edge and sharpness
• Easy sharpening
• Great for long hours of cooking

Cons

• Difficult maintenance
• Rusting and discoloring can happen even with proper care
• Needs to be cleaned and dried during cooking
• Need to be oiled and stored properly

White steel #2 (Shirogami #2 / Shiroko #2): pure carbon steel gives a great sharp edge and easy sharpening.

White steel #1 (Shirogami #1 / Shiroko #1): pure carbon steel made with a high carbon composition, has a high cutting performance and is easy to sharpen, but can chip due to the high hardness.

Blue steel #2 (Aogami #2 / Aoko #2): similar to White Steel #2 but with added elements (tungsten, chromium) that makes it more durable and with higher edge retention.

Blue steel #1 (Aogami #1 / Aoko #1): higher quantity of carbon, chromium and tungsten than Blue steel #2 makes it harder, sharper and with better edge retention.

Aogami Super (Blue super steel): produced by a difficult technique the incorporates high quantities of elements (carbon, chromium, tungsten) in the steel. Makes great blades, with great hardness and durability.

Powdered High Speed Tool Steel

Powdered Tool Steel is made by a different process called powder metallurgy. This originates element rich steel with singular characteristics. This is used in ultra hard cutting tools and tolerates higher temperatures. Has you can imagine, this makes a great blade, with ultra cutting performance and edge retention. Easy to maintain and resistant to corrosion.

Pros

• Rust resistant
• Easy maintenance
• Great cutting performance

Cons

• Expensive

SG-2: the most commonly used in knives. 

Cowry X / ZDP-189: premium steel made by a difficult process which makes it very expensive.

Miscellaneous 

Cladded knife: made from a core of carbon steel covered in soft stainless steel, making it easier to maintain than pure carbon but harder than pure stainless. Excellent cutting performance with medium maintenance.

Mirror Polishing: originated by polishing the entire blade with fine abrasives that erase all marks and makes the surface mirror-like. Some professionals defend this finish makes the knife more resistant to patina and cut more smoothly.

Damascus / Suminagashi: originally made by folding the blank repeatedly, now-a-days made by etched cladding that produces a swirly appearance. This treatment is purely futile, with no improvement in performance. To keep the ink-swirl appearance, the sharpening process must be careful in order to prevent scratching. This can be mitigated by involving the top part of the blade in protective tape.

Japanese Handle Types

Japanese knives can come with different types of handles: wa-handles (japanese), yo-handles (western) and custom handles. Tang refers to the extension in which the blade goes through the handle. Western knives have full tang, meaning the blade goes all through the handle. Japanese handles are half tang, with makes them lighter but still resistant.

Japanese handles have ferrules between the blade and handle. Traditionally, and in good quality knives, it is made of water buffalo horn. Even though the standard color is black it can have other colors. A plastic ferrule is an indicator of a cheap knife.

Wa-handles (japanese): made of magnolia wood (ho wood) and with a very simple design resembling a wooden rod. This handle require little maintenance and doesn't become slippery when wet. The design may seem uncomfortable and fragile but it is not. The light weight of the wood and the half tang allow an easy used of the knife. "Wa-" can be used as a prefix to the knife's name to refer to this type of handle. 

Yo-handles (western): handles usually shaped to improve the grip and have full tang, even though this doesn't provide an advantage. The use of the prefix "yo-" can be a mention to this type of handle or as a reference for the double-beveled blade (western) like in yo-deba.

Custom handles: handles made by artisans to improve aesthetics, that can include elaborated details and rare woods, being the most frequent oak and ebony. This type of handle can provide extra weight to the handle that is preferred by some people, but not necessarily required in light knifes. Custom handles can have some problems, like low durability or being uncomfortable in the hand.