STEEL INFORMATION AND TERMINOLOGY

There are many different types of steels used for blade making. Each type of steel has its unique characteristics, and the same steel in different craftsmen’s hands can yield various results, much like chefs cooking with similar ingredients.

There are three general types of steel common in Japanese cutlery:

• Carbon
• Stainless
• Clad (Carbon & Stainless)

Each type of steel has many varieties depending on the blade smith’s preferences and the customer’s performance desires.

CARBON STEELS

Named for the colored paper attached to the steel at the HITACHI factory in Japan, carbon steels are not rust-resistant. Like a cast iron pan, these blades must be kept clean and dry when not in use. A light layer of blade (Tsubaki) oil will help protect the blade from rust, especially in humid climates. Carbon steel is easy to sharpen and forms a terrific edge. If properly cared for, carbon steel will form a beautiful patina over time but can rust if neglected.

White Paper (Shirogami) Steels

This very pure form of carbon steel oxidizes faster than blue steel but is easier to sharpen and creates a terrific edge. There are three grades of Shirogami steel:

• Shirogami #1: The hardest white paper steel. It stays sharp the longest but can be brittle under aggressive use.
• Shirogami #2: The most commonly used type of white steel. Good edge retention and very easy to sharpen.
• Shirogami #3: The most durable of the three types but dulls more quickly.

Blue Paper (Aogami) Steels

Blue steel is essentially white paper steel with added Chromium (Cr) and Tungsten (W). These alloys make blue steel harder than white steel and less reactive. Designed for knives and tools, this steel has supreme edge retention while remaining easy to sharpen. Blue paper steel also has three grades:

• Aogami Super: Vanadium (V) is added for super strength and hardness. Top-notch edge retention for carbon steel with great wear resistance.
• Aogami #1: Less common than #2 and Super, but forms a terrific edge that stays sharper longer.
• Aogami #2: The most durable of the blue steels. A tough steel that sharpens easily.

Yellow Paper (Kigami) Steels

Much less common in high-grade cutlery but often used for tool making and agricultural products like sickles, hatchets, and axes.

STAINLESS STEELS

These steels have a much lower carbon content and contain at least 10.5% Chromium (Cr). Although generally harder to sharpen than high carbon knives, stainless steel knives are much more rust-resistant and very easy to maintain. They contain many alloys such as Molybdenum (Mo), Vanadium (V), Nickel (Ni), and Cobalt (Co) to form a wide variety of steels suitable for both beginners and professionals.

Molybdenum Vanadium Steel

A common type of stainless steel that is of good quality. Very durable, great for beginners and people who are rough with their knives. Easy to re-sharpen but needs to be re-sharpened more quickly than other varieties.

VG-10 Steel

The most common type of stainless steel found in Japanese cutlery due to its good edge retention and moderate ease of sharpening. Cobalt (Co) adds toughness and durability. A high Vanadium (V) content gives this steel high rust resistance. Often used in Damascus and Migaki style blades.

AUS-8 & AUS-10 Steel

Less Chromium (Cr) makes these steels less rust-resistant than VG-10, but Nickel (Ni) adds toughness and durability. A great middle ground between edge formation and edge retention.

High-Speed Powdered Steels - R2, SG2, SRS-15

Called “powdered” steel because of its very fine grain structure, allowing for excellent edge formation. Also used for the rails of high-speed trains and drill bits; these extremely hard steels have the longest edge retention of any stainless steel. Although harder to sharpen, the edge durability of these steels makes them ideal for demanding professionals.

Gin-san Steel - Gingami #3

A special HITACHI steel functioning similarly to semi-stainless steel. It has more rust resistance than high carbon steels but less than most stainless steels. This steel forms a terrific edge with the durability of stainless steel and the ease of sharpening similar to harder high-carbon steels.

CLAD STEEL

These blades contain both high carbon and stainless steels, typically featuring a core of Shirogami or Aogami steel with outer layers of stainless or low-carbon steel. These blades are popular because they offer the advantage of a carbon edge that is easy to sharpen and forms a terrific edge while avoiding oxidation issues across the entire blade. These blades are great for professionals in busy kitchens or home cooks who want to experiment with carbon steel but are worried about extra maintenance.

There are two techniques for achieving Clad Steel:

• San-mai: Like a sandwich, a hard carbon core is forge laminated with two thin layers of stainless steel throughout the blade.
• Warikomi: Like a pita, one piece of stainless steel is heated and folded around the carbon core, leaving the carbon exposed on the edge side but disguised on the spine side.

KNIFE CARE

• Wash and dry the blade by hand immediately after use. They are not dishwasher safe.
• Use a soft sponge to wash the blade. Avoid abrasive dish scrubbers that may damage the blade's finish.
• Apply a layer of tsubaki/camellia oil to the surface of carbon blades to prevent oxidation and rust.
• Do not cut through bones, as this can chip the blade.
• Never use the knife to cut frozen food.
• Never twist, cleave, or pry the blade. This can chip the blade.
• Always use a wooden or plastic cutting board. Avoid cutting on glass, marble, slate, plates, china, or anything harder than steel. Avoid bamboo as it is very hard and dulls knives quickly.
• Store knives so that the blades do not knock into each other (saya covers, magnetic strips).
• Use a ceramic honing rod or leather strop for edge maintenance.
• Always sharpen by hand on water stones.