• Japanese Knife Materials

  • By introducing the materials used in knives, we aim to help customers understand the quality and performance of knives, enabling them to find the perfect knife that meets their needs and preferences.

Iron, in its raw state, is riddled with impurities, making it prone to rust and brittleness—less than ideal for kitchen knives. By removing these impurities and adding carbon, iron is transformed into carbon steel, enhancing its hardness and durability for culinary use.

Carbon Steel:

Characterized by a carbon content of 0.04-2.14%, this material strikes a balance between hardness and edge retention, making it a popular choice for many kitchen knives.

Stainless Steel:

The game changes when over 10.5% chromium is introduced to carbon steel, evolving it into stainless steel, celebrated for its exceptional resistance to rust. This meticulous alloying process crafts knives that are not just high-performing but also durable, able to withstand the rigors of kitchen life.

Discovering the Science Behind Japanese Knives

  • Japanese knives, with a rich history of over 600 years, trace their roots back to the Azuchi-Momoyama period. These knives are celebrated not only for their exquisite craftsmanship but also for their remarkable functionality. Today, advancements in science have taken this traditional craft to molecular levels, offering a deeper understanding of their superior performance.

  • Imagine driving a car daily but not fully grasping how its engine powers motion or its brakes bring you to a halt. This is the case for many professional chefs as well—they wield Japanese knives daily but might not fully comprehend why these blades cut so effortlessly, resist corrosion, or chip under certain conditions.

  • By understanding the science behind knife materials, you can go beyond appreciating their beauty and sharpness. You’ll be able to select a knife tailored to your needs and master its use, unlocking its full potential. Here, we’ll explore two key factors: carbon content and alloy composition, which significantly influence a knife’s performance.

  • 1. The Role of Carbon: A Sharp Edge and Beyond

    Carbon is the heart of steel. Though it constitutes a mere 1% of the material, even a 0.1% difference can create a noticeable variation in sharpness and hardness. Higher carbon content increases the blade's hardness, resulting in superior sharpness and edge retention. However, it also requires more maintenance, as these blades are prone to chipping and demand skillful sharpening.

  • For instance:

    • White Steel (Shirogami) is revered for its unparalleled sharpness but requires meticulous care.
    • Blue Steel (Aogami) incorporates elements like tungsten and chromium, enhancing its toughness and rust resistance, making it easier to handle without sacrificing performance.

  • 2. Alloy Composition: The Key to Craftsmanship

    Steel isn't just about carbon. The additional elements in the alloy, such as chromium, tungsten, or vanadium, significantly affect the knife’s properties and its crafting process. Each type of steel demands precise temperature control during heat treatment, a process known as "quenching."

  • The legendary White Steel knives, especially pure "water-quenched" varieties, require such strict heat management that even master craftsmen risk cracking the blade during cooling. On the other hand, Blue Steel, with its added elements, offers a more forgiving tempering process while still achieving exceptional sharpness and durability.

  • This intricate balance between heat treatment, composition, and craftsmanship explains why Japanese knives are often likened to samurai swords—both require meticulous quenching to unlock their full potential.

  • Empower Your Choice with Knowledge

    Understanding these scientific aspects of Japanese knives allows you to make informed choices. Are you looking for a knife with razor-sharp precision, or do you prioritize durability for daily kitchen tasks? By considering carbon content and alloy composition, you can select the perfect blade that resonates with your cooking style.

  • Owning a Japanese knife isn’t just about having a tool; it’s about embracing a centuries-old tradition refined by modern science. With proper care and understanding, your knife will become an extension of your craft, making every slice, chop, and cut a seamless experience.

Element

japanese_knife_made_in_Sakai

Carbon(C)

Carbon (C) is an essential element for steel, and it is a key element in creating various compounds and elements. It is a representative element for increasing hardness and strength.

Chromium(Cr)

Chromium (Cr) improves hardenability. Stainless steel contains 10.5% or more of Cr.

Manganese (Mn)

Manganese (Mn) is an element that makes quenching easier and increases toughness.

Molybdenum

Molybdenum is used to make V1 to V10. (It is originally contained in V1 as well.) Adding a small amount makes it more tenacious. It also increases strength and hardness. Molybdenum steel is often referred to as molybdenum steel, but molybdenum steel is a general term for steel materials that contain molybdenum. It is not the name of a specific steel material, such as white steel, but a steel material that contains molybdenum is widely referred to as "molybdenum steel.

Phosphorus (P)

Phosphorus (P) is a harmful element in steel, which causes cold brittleness, making steel brittle in cold conditions. Therefore, it is necessary to limit its content as much as possible.

Silicon(Si)

Silicon (Si) is an element that increases hardness and strength.

Sulfur(S)

Sulfur (S) is a harmful element for steel as it causes hot-shortness, meaning it makes the steel brittle when in a red-hot state. The content of sulfur should be as low as possible.

Tungsten(W) 

Tungsten (W) is an element that improves heat treatment characteristics and increases hardenability. It also improves wear resistance.

1. Carbon Steel

  • Carbon steel, a renowned material used in kitchen knives, is created by combining iron with carbon to enhance hardness, sharpness, and edge retention. Among these, Yasugi Steel (Yasuki Hagane) stands out, manufactured by Hitachi Metals, Ltd. at their factory in Yasugi City, Tottori Prefecture. Yasugi Steel is widely used as the raw material for various iron products, including knives, scissors, and agricultural tools.

  • For traditional Japanese knives, the primary types of Yasugi Steel used are “Yellow Paper,” “White Paper,” and “Blue Paper” steel. These names originate from the colored paper labels that Hitachi Metals applied to the steel for identification purposes.

  • Knives made from carbon steel, particularly Yasugi Steel, excel in cutting performance, surpassing stainless steel and offering easier sharpening. However, they require meticulous maintenance to prevent rust and are more prone to chipping due to their higher hardness. Knives crafted from Yasugi Steel are ideal for experienced cooks who value exceptional sharpness and are committed to diligent care of their tools.

  • When choosing a knife, the type of steel used plays a major role in its performance and ease of use. Especially for professional chefs or those who are particular about their knives, selecting the right steel is a crucial factor. The sharpness retention, ease of sharpening, and durability—each type of steel has its unique characteristics, and the best choice depends on the user's skills and intended use.

  • SK Steel:

    • A common carbon steel used for tools like knives.
    • Often found in affordable household knives.
    • The carbon content is typically around 0.55% to 1.5%.

  • Yellow Steel (Kigami Steel):

    • Based on SK steel, with around 50% high-purity iron sand added.
    • It offers better quality than SK steel but still contains more impurities compred to white or blue steel.
    • It is relatively affordable and easy to sharpen.

  • White Steel (Shirogami Steel):

    • A highly pure steel made by further removing impurities from yellow steel.
    • It is known for being easy to sharpen and having an exceptionally sharp edge.
    • However, it is difficult to heat treat, requiring the skill of a master craftsman.

  • Blue Steel (Aogami Steel):

    •  is highly wear-resistant and retains its sharpness for a long time.
    • While it is tougher and more resistant to chipping than white steel, it can be more difficult to sharpen.

  • Relationship:

    As you progress fromSK steel → Yellow steel → White steel → Blue steel, thepurity, quality, and performanceimprove.
    At the same time, theprice increases, and thedifficulty in handlingalso rises. Each type of steel is chosen based on its purpose and the user's skill level.
Yasuki Steel

White Steel vs Blue Steel

  • White Steel (Carbon Steel): Choose for Ease of Sharpening

    Features: White steel is favored for its ease of sharpening and excellent cutting performance. It can be sharpened to a sharp edge quickly, although the sharpness may decrease with frequent use. The quick resharpening process allows for easy maintenance of optimal sharpness.

  • Blue Steel (Alloy Steel ): Choose for Lasting Sharpness

    Features: By adding chromium (Cr) and tungsten (W) to carbon steel, blue steel's sharpness durability significantly improves. It can maintain good sharpness with infrequent sharpening, even with high volume cutting. However, while blue steel maintains sharpness longer due to its components, it is harder to sharpen. Additionally, the enlargement of the metal's structure can slightly decrease sharpness.

  • Differences between Steel #1, Steel #2, and Steel #3

  • While knives have a silver appearance, when sharpened, the slurry produced turns black. This is because the slurry contains carbon, a key component that provides the knife with hardness.

  • The hardness of steel is classified as #1, #2, and #3, with lower numbers indicating greater hardness. For example, Steel #1 offers the highest level of hardness and provides the sharpest edge. Steel #2 and Steel #3 follow in order, with progressively lower hardness and sharpness, though they still maintain sufficient sharpness for most purposes.

  • It is often said that the more carbon steel contains, the better the sharpness. This is because the carbides formed in the steel provide more grip when cutting, which contributes to a sharper edge. Additionally, harder steel has better edge retention, allowing the blade to stay sharp for longer periods.

  • One of the advantages of harder steel is that it requires less force to cut. For example, when knives with different hardness levels are sharpened at the same angle and used with the same force, the harder steel will generally cut more effectively. However, as steel becomes harder, it also becomes more prone to chipping and is more difficult to sharpen.

  • Steel #1: Focused on Sharpness

    #1 is recommended for knives that require exceptional sharpness, such as those used for slicing delicate dishes like fugu sashimi or thin slices of sea bream, due to its excellent cutting ability.

  • Steel #2: Focused on Balance

    #2 offers a good balance between sharpness and ease of sharpening, making it suitable for cutting a variety of ingredients, from vegetables to meats.

  • Steel #3: Focused on Ease of Sharpening

    #3 is easy to sharpen, making it ideal for knives that may chip, such as those used for filleting fish, since it can be quickly resharpened.

 Features of Blue Steel #1

  • Blue_Steel_2_Mukimono_190mm

    Extremely High Hardness and Sharpness

    Blue Steel #1 is a material known for its high carbon content, which contributes to its exceptional hardness. When properly sharpened, it can achieve an impressively sharp edge.

  • Blue_Steel_2_Yanagiba_Kiritsuke_330mm-Mirror_Polished_one_side

    Excellent Wear Resistance

    Due to its high hardness, knives made from Blue Steel #1 maintain their sharpness for extended periods, holding their edge better compared to regular knives.

  • Sharpening_a_knife

    Challenging to Handle

    Blue Steel #1 is extremely hard, which makes it difficult to sharpen and may not be suitable for beginners. Due to its hardness, the sharpening stone can slip, requiring a skilled technique to sharpen effectively.
Blue Steel #1

Features of Blue Steel #2

  • Blue_Steel_2_Mukimono_190mm

    Stable Sharpness

    Blue Steel #2, known for its high carbon content, is extremely hard. This quality allows it to maintain a sharp edge for an extended period once sharpened.

  • Blue_Steel_2_Yanagiba_Kiritsuke_330mm-Mirror_Polished_one_side

    Wear Resistance

    Due to its high hardness, knives crafted from Blue Steel #2 retain their sharpness longer than regular knives, offering superior wear resistance.

  • Sharpening_a_knife

    Hard to Sharpen

    Blue Steel #2 is hard, making it challenging to sharpen and requiring skilled maintenance or extra effort. Compared to Blue Steel #1, it has better abrasion resistance on sharpening stones, making sharpening easier.
Blue Steel #2

Features of White Steel #1

  • Exceptional Sharpness and Hardness

    With an increased carbon content, White Steel #1 achieves exceptional sharpness and boasts a high hardness rating of HRC66, making it an ideal material for Japanese knives, particularly those used in traditional cuisine.

  • Ease of Sharpening

    Due to its low levels of additives and impurities, White Steel #1 is surprisingly easy to sharpen with a whetstone, a rare quality for such a high-hardness knife steel.

  • Pure Steel Composition

    Free from tungsten (W) and chromium (Cr), which are commonly found in blue steel, White Steel #1 is praised for its purity and ease of maintenance, offering a balance between sharpness and usability despite being less wear-resistant than blue steel.
White Steel #1

Features of White Steel #2

  • White-Steel-2-Kamausuba-210mm-Mirror-Polished-both-sides

    Sufficiently Sharp Edge

    White Steel #2 is a material with a high carbon content, making it extremely hard. When sharpened, it exhibits a sharp edge.

  • Sharpening_a_knife

    Not Highly Difficult to Sharpen

    White Steel #2 is not as hard as blue steel, so it is not highly difficult to sharpen. It can be considered relatively easy to handle even for beginners.

  • White-Steel-2-Yanagiba-300mm-Mirror-Polished-one-side

    Good Cost Performance

    White Steel #2 is not as expensive as the top-grade White Steel #1, making it a good choice in terms of cost performance.
White Steel #2

Comprehensive Guide to White Steel #2 and Blue Steel #2

Explore the essential differences between White Steel #2 and Blue Steel #2 in our guide, focusing on their cutting performance, durability, and ease of sharpening. This article provides practical insights for chefs and cooking enthusiasts to make an informed choice between these two popular steel types for kitchen knives.

White Steel #2 vs Blue Steel #2

Comprehensive Guide to Blue Steel #1 and Blue Steel #2

Explore the key differences between Blue Steel #1 and #2 knives, focusing on sharpness, durability, and user needs, to help you choose the right one for your cooking tasks.

Blue Steel #1 vs Blue Steel #2

Comprehensive Guide to White Steel #1 and White Steel #2

White Steel #1 and White Steel #2 are among the most popular materials used in Japanese knives. This guide compares their unique characteristics and performance to help you choose the best option for your cooking style and needs. Whether you’re a beginner or a professional chef, find valuable insights for selecting the perfect Japanese knife.

White Steel #1 vs White Steel #2

  • 2. Stainless Steel

  • Stainless steel, true to its name meaning "stain less," is celebrated worldwide for its exceptional resistance to rust and corrosion. This remarkable material has transformed modern knife-making, earning its place in kitchens and workshops across the globe. But did you know stainless steel is actually a type of steel? Many assume it’s a completely different material, but its unique properties come from a higher chromium content in the alloy.

  • The story of stainless steel begins in 1904, when French scientist Léon Guillet discovered that adding 13% chromium to iron created a material significantly less prone to rust. This innovation, called "13-chromium stainless steel," laid the foundation for the development of countless tools and instruments. A decade later, in 1913, British scientist Harry Brearley revolutionized knife-making by inventing martensitic stainless steel. By adding carbon to chromium steel, he created a hardenable stainless steel perfect for blades.

  • The ability to combine durability, rust resistance, and sharpness made stainless steel a game-changer. However, challenges emerged: increasing carbon content for sharpness also made the steel more susceptible to rust. Enter molybdenum and vanadium. These elements enhanced the steel's toughness and minimized brittleness, giving birth to molybdenum-vanadium stainless steel—a staple in premium knives.

  • Whether you’re a professional chef or a home cook, stainless steel knives offer a perfect blend of innovation and tradition. The legacy of pioneers like Guillet and Brearley lives on, ensuring these blades remain indispensable tools in the art of cooking and craftsmanship.
Stainless Steel

Recent advancements in technology have brought stainless steel's sharpness closer to that of carbon steel, while its durability and low maintenance make it a popular choice for both home and professional use. Additionally, the wide variety of grades available ensures versatility across different applications.

Just like blue, white, and yellow steels, these stainless steels shown in the diagram on the left are also manufactured by Hitachi Metals. This highlights the company’s technological expertise, which plays a vital role in maintaining the diversity and high quality of Japanese knives.

  • ZDP189

    Hitachi Metals' strongest powder steel, ZDP-189, boasts a hardness of 67 or higher, the highest of any known steel for cutting tools. It offers the ultimate combination of hardness, toughness, wear resistance, and corrosion resistance. However, due to its extreme hardness, ZDP-189 is difficult to sharpen with regular sharpening stones and is quite expensive.

  • Ginsan

    Ginsan is a type of stainless steel known for its excellent balance between corrosion resistance and cutting performance. Manufactured by Hitachi Metals, this steel is widely recognized under the name "Ginsan." It features a high chromium content of 13-16%, which significantly enhances its resistance to corrosion. Additionally, the carbon content ranges from 0.8 to 1.3%, providing a good balance between hardness and toughness, ensuring stability during use.

    Due to its superior sharpness and resistance to rust, Ginsan is extensively used in various types of blades, including kitchen knives. Trusted in both professional kitchens and homes, Ginsan steel makes daily culinary tasks more efficient and enjoyable.

Advice from a Master Craftsman on Stainless Steel

  • "Stainless steel, once considered lacking in sharpness compared to traditional carbon steel, has come a long way due to advancements in modern technology. Today, high-quality stainless steel can offer sharpness and edge retention that rivals the finest traditional materials.

  • The key advantage of stainless steel is its rust resistance, which makes it an excellent choice for everyday use, especially for those in humid or salty environments. However, even with its durability, proper care and regular maintenance are essential to keep the blade performing at its best.

  • For those who appreciate both convenience and performance, stainless steel knives provide an outstanding balance, allowing you to enjoy the precision of a sharp blade while minimizing the maintenance required."

  • From the perspective of a traditional craftsman

  • The Science Behind Stainless Steel: Chromium’s Protective Bond with Oxygen

    Stainless steel owes its renowned resistance to rust to the unique behavior of chromium. Before the steel can develop the dreaded red rust, the chromium in its composition reacts with oxygen in the air to form a thin, invisible layer of chromium oxide. This layer acts as a shield, preventing further corrosion and maintaining the steel’s integrity. It’s a brilliant interplay of elements—chromium and oxygen working together to preserve and protect. This natural barrier is what makes stainless steel such a trusted material in both everyday life and critical industries.

Understanding Stainless Steel: The Rust-Resistant Alloy

Stainless steel, enriched with elements like chromium, nickel, and vanadium, is celebrated for its corrosion resistance, a breakthrough in metallurgy achieved in 1913 by Harry Brearley. This advancement has led to widespread adoption in kitchen knives, particularly appreciated in settings like sushi restaurants for their ease of maintenance and hygiene. Recent innovations in high-carbon stainless steel have further enhanced these knives' sharpness, rivaling traditional carbon steel.

Stainless Steel

Japanese Knife Materials 4 Points

Knife material quality is defined by hardness, wear resistance, toughness, and corrosion resistance. These factors intricately determine sharpness, durability, and maintenance needs. Understanding their interplay unveils the essence of blade quality and its price range.

Japanese Knife Materials 4 Points

The Origin of Craftsmanship

  • The Harmony of Iron and Carbon: The Secret Behind Strong Blades

    Iron, as a material, reveals its true potential when paired with carbon. The more carbon iron contains, the harder and sharper the blade becomes. This principle forms the foundation of Japan's centuries-old forging techniques.

  • However, as iron becomes harder, it also becomes more brittle. This delicate balance demands that we, as traditional artisans, approach the process with the utmost precision. We listen to the voice of the material, adjusting the composition and heat treatment with care, seeking the perfect equilibrium.

  • The story of iron and carbon is intricately woven into every blade. If you can feel the strength and finesse that resides in its edge, it brings us, as craftsmen, immense fulfillment.
Sakai Traditional Craftsmen Collection

KIREAJI's Three Promises to You

  • japanese_knife_made_in_Sakai

    1. High-quality Japanese Knive

    We offer knives crafted by craftsmen from Sakai City.

  • Honbazuke

    2. Genuine Sharpness

    To ensure you experience sharpness, we provide a free Honbazuke by our skilled craftsmen.

  • 3. Lifetime Knife Use

    Every knife comes with a free Saya(Sheath) for durability. We also provide paid after-sales services with Sakai City Japanese knife workshop.