1: Forging — The Art of Bringing Steel to Life

Forging is a traditional technique of shaping metal by hammering it.
In this process, the base materials—soft iron and steel—are heated until they glow red and become malleable, making them easier to work with.

By hammering the heated metal, the blade’s shape is extended while its internal structure becomes denser, significantly enhancing its strength and toughness.
This method produces a blade that combines exceptional sharpness, durability, and remarkable beauty.

Forging is more than just shaping metal—it is a delicate and precise craft that breathes life into the steel.
Each knife carries the spirit and experience of the artisan who painstakingly brings it to life.

1-1.Wakashitsuke — Forge Welding of Steel and Soft Iron, Inheriting the Spirit of the Samurai Sword

The first step in traditional Japanese knife forging is Wakashitsuke, a forge welding technique where steel and soft iron are joined at high temperatures through hammering. This process, rooted in the art of Japanese swordsmithing, remains a central element in the knife-making traditions of Sakai City.

The method involves heating soft iron to around 1,000°C (1,832°F), placing steel on top, returning it to the furnace, and then hammering the two metals together while they are red hot. The intense heat softens the materials just enough so that when struck, they fuse seamlessly into a single, durable blade that offers both strength and sharpness.

In the Wakashitsuke process, temperature control is the most critical factor in determining the final sharpness of the blade. If the temperature is too low, the metals will not bond properly. If it is too high, the steel can overheat and degrade. Even a slight miscalculation in heat can severely compromise the quality of the knife.

To master this process, artisans learn to read the color, glow, and texture of the metal by eye, and time their strikes with precision. Fine adjustments in temperature help preserve a tight grain structure within the steel, unlocking the blade’s full sharpness potential.

Japanese knives are often crafted with a laminated structure, combining hard steel with softer iron. This fusion mirrors the philosophy behind traditional Japanese swords: the steel provides exceptional sharpness, while the soft iron adds flexibility and shock absorption.

In Sakai, craftsmen take immense care in material selection, believing that “a great knife starts with great materials.” Among the most prized is Yasuki steel, renowned for its high purity and minimal impurities, allowing for outstanding sharpness and edge retention.

Sakai knives are more than tools — they are celebrated for their ability to slice through food without damaging cellular structure, preserving aroma, flavor, and texture. This remarkable performance is the result of over 600 years of expertise passed down through generations of artisans. Their craft blends fire, metal, and the human touch into a single, seamless process.

In this technique, a piece of soft iron is heated until it glows, and a strip of steel is placed on top. The two are reheated together, with a borax-based flux sprinkled in between, and just before the steel begins to melt, the smith rapidly hammers them into one. This timing is crucial — forging right before the melting point creates a fine, uniform structure in the steel, enhancing both durability and sharpness.

The blade is then slowly cooled in straw to prevent warping, and later hardened by quenching it from around 800°C (1,472°F) — producing a perfect balance of toughness and hardness. Every blow of the hammer and every temperature shift plays a vital role in creating a blade that transcends simple utility.

1-2.Sakizuke (Preliminary Forging) — Building the “Skeleton” of the Blade

After the previous stage of forge welding (wakashitsuke), where soft iron and high-carbon steel are bonded together, the material moves into the preliminary forging phase, known in Japanese as Sakizuke. In this stage, the craftsman begins shaping the blade’s fundamental structure—what can be called the "skeleton" of the knife—while further refining the steel’s internal properties to enhance both its strength and sharpness.

Using a combination of a mechanical spring hammer and hand hammer, the blacksmith carefully hammers the glowing-hot billet. When the temperature drops, the blade is returned to the furnace for reheating, and the hammering resumes. This repeated cycle of heating and forging not only shapes the knife but also compresses the metal’s grain structure, making it finer and denser—a key factor in achieving long-lasting sharpness and durability.

For example, forging a 300mm Yanagiba knife with White Steel (Shirogami) takes about 20 minutes of hammering before the blade begins to take shape. However, for Blue Steel (Aogami), which is significantly harder, the same task requires nearly twice as much time. While White Steel stretches visibly under the hammer, Blue Steel resists at first, requiring much more patient and precise forging. Each type of steel demands a unique approach, and a skilled craftsman must understand these differences to draw out the full potential of the material.

This stage is not simply about shaping the blade—it’s about infusing it with strength and character. A well-executed Sakizuke lays the groundwork for later steps such as quenching and sharpening. The quality of this forging phase directly determines the final performance of the knife.

Facing fire and steel, the craftsman reads subtle changes in heat, color, and resistance, gradually guiding the metal into its ideal form. Preliminary forging is the moment when a lump of bonded iron and steel begins to reveal its destiny as a refined, precision cutting tool.

1-3. Shaping and Core Adjustment – Where the Beautiful Form Begins

After the forging process has established the “skeleton” of the blade, it moves into the crucial stage of shaping the knife’s elegant outline. This process starts with cutting out the knife’s basic profile, known as the han-gata, from the forged steel. This step is fundamental as it forms the base for later sharpening and handle attachment.

Next comes core making (tang formation), where the part of the blade that fits inside the handle is created. Since cutting performance is not required for this part, it is typically made from a base metal, such as soft iron. Though seemingly modest, this component plays a vital role in the knife’s stability and durability during use.

Following core formation, the blade tip is shaped through a process called “shaping.” Here, the base of the blade near the handle is kept thick while gradually tapering down towards a thinner edge—this is called a taper structure. This design not only sharpens the cutting edge but also optimizes the overall weight balance, resulting in a knife that is less tiring and more comfortable to use.

The usability of the knife—its comfort in hand and stability during cutting—is largely determined in this stage. Skilled artisans pay meticulous attention to thickness and angles down to millimeters, crafting a knife that naturally follows the movements of the chef’s hand.

This stage can be regarded as the “design” phase that balances functionality and aesthetics. It marks the beginning of the transformation of a piece of metal into a truly usable and beautiful culinary tool.

1-4. Yakinamashi (Annealing) – Giving the Metal a Moment of Rest

After forging, metal retains invisible internal stress. If this stress is left untreated, it can lead to warping, cracks, or inconsistencies in performance during later stages of production. To prevent these issues, artisans perform a critical process called annealing.

Annealing is a traditional heat treatment technique in which the forged steel is heated and then cooled very slowly. This gradual cooling process removes internal stress and softens the metal’s structure, making it easier to work with in the next steps. More importantly, it refines the internal grain, resulting in improved sharpness, durability, and overall performance of the finished knife.

In the production of Sakai knives, annealing is done using a time-honored method: the steel is allowed to cool slowly over a full 24-hour period. This extended “rest” period not only relaxes the metal but also serves as a kind of fine-tuning process, preparing the steel for precise shaping and finishing.

Today, many craftsmen use mechanical furnaces to stabilize temperatures during annealing. However, some traditional workshops still employ the old method of burying the steel in ash after burning straw. This technique prevents carbon from evaporating from the surface of the steel, leading to a tighter and more resilient grain structure.

The choice of method and the careful control of temperature and time make all the difference. Annealing is not just a technical step—it is a reflection of the artisan’s sensitivity and experience.

By taking the time to anneal the metal properly, the steel regains its true strength and beauty, ready to reveal its full potential in the hands of a skilled blacksmith. The outstanding reputation of Sakai knives is built, in part, on this quiet but essential moment of rest.