Forging is one of the most recognizable parts of traditional Japanese knife making. But the real skill lies not simply in striking hot steel, but in knowing how to shape it with heat, experience, and careful judgment.

When we imagine a Japanese blacksmith at work, we often picture glowing steel, a hammer, and sparks rising from the forge.

It is a powerful image.

But what is actually happening when a blacksmith heats and hammers steel?

Does forging automatically make a knife sharper? Is a hand-forged knife always better than one made using modern manufacturing methods?

And why has forging remained important in places such as Sakai, Japan?

To understand the value of traditional Japanese knife making, we need to look beyond the familiar image of hammer and fire.

The most important part of forging is not how dramatic the process looks.

It is the knowledge required to control it.

Forging, known as tanzō (鍛造) in Japanese, is a metalworking process in which heated steel is shaped through controlled deformation, often using hammers or presses.

In traditional Japanese knife making, a blacksmith heats the material and works it into the approximate form of a blade.

Depending on the knife's construction, the process may involve a single type of blade steel or a combination of different metals.

For example, an Awase knife commonly uses a hard cutting steel joined to softer cladding material.

The blacksmith must understand how these materials behave during heating and shaping.

Temperature is particularly important.

Steel becomes easier to deform when heated, but excessive temperatures or inappropriate handling can damage its properties.

The blacksmith therefore works within a suitable temperature range, repeatedly checking the shape and condition of the material.

Forging is not simply about applying force.

It is about shaping metal while managing the conditions that influence the finished blade.

One of the most common claims about forged knives is that hammering makes the steel denser and automatically produces a sharper blade.

The reality is more complex.

Modern knife steels are generally produced through controlled industrial processes before reaching the blacksmith.

They are not usually full of impurities that must be hammered out by hand.

During hot forging, deformation and temperature can influence the steel's internal microstructure.

Processes such as recrystallization and grain growth may occur depending on the material and working conditions.

Careful temperature control and subsequent heat treatment are essential to achieving the desired properties.

Simply striking steel more times does not guarantee a better knife.

Excessive heat or improper forging can even harm the material.

Likewise, forging alone does not determine sharpness.

A knife's cutting performance depends on its steel, heat treatment, blade geometry, sharpening, and intended use.

The blacksmith's skill lies in understanding how these factors work together, rather than relying on hammering as a guarantee of quality.

Japanese kitchen knives can be produced using different manufacturing methods.

Two commonly discussed approaches are forging and stamping.

Forging: Steel is shaped through deformation, usually with heat and the application of force. Traditional blacksmiths may use hand hammers, power hammers, or other equipment to control the blade's form.

Stamping: A blade blank is cut from a sheet or plate of steel, often using industrial cutting or pressing equipment. It then undergoes further processes such as heat treatment, grinding, sharpening, and finishing.

These approaches differ in how the initial blade shape is produced.

However, neither method automatically guarantees superior cutting performance.

A carefully designed and properly heat-treated stamped knife can perform very well.

Similarly, a forged knife may perform poorly if its heat treatment, blade geometry, or sharpening is inadequate.

Forging can offer makers considerable flexibility in shaping a blade and working with certain traditional constructions.

Stamping can offer consistency and efficiency in production.

The quality of the finished knife depends on the entire manufacturing process, not simply whether a hammer or cutting press was used.

Traditional Japanese knives are made using different blade constructions.

Two important examples are Honyaki and Awase.

Honyaki: Traditionally made from a single type of blade steel. Its properties are established through carefully controlled heat treatment, sometimes including differential hardening. Producing a well-made Honyaki blade can be particularly demanding because of the risk of distortion and cracking.

Awase: Made by joining a hard cutting steel with softer cladding material. The combination allows different materials to serve different purposes within the blade.

A traditional Kasumi knife is commonly an Awase knife with a contrasting finish that reveals the relationship between the cutting steel and softer cladding.

The terms therefore describe different aspects of knife construction and appearance: Awase refers to a combined-steel construction, while Kasumi commonly refers to a characteristic mist-like finish associated with that construction.

Both Honyaki and Awase knives can require considerable skill to forge and finish.

Neither is automatically sharper or more useful than the other.

Their differences are better understood through their construction, production methods, maintenance requirements, and intended use.

One important contribution of forging is the ability to establish the blade's basic form.

The blacksmith can influence the distribution of material along the blade, including its thickness and overall profile.

For example, some knives are thicker near the heel or spine and become thinner toward the tip or cutting edge.

A gradual change in thickness along the length of the blade is commonly called a distal taper.

These geometric features can influence the knife's weight, balance, strength, and cutting behaviour.

However, forging does not establish the final geometry by itself.

Grinding and sharpening are essential stages in creating the finished blade.

In Sakai's traditional production system, specialist sharpeners often refine the surfaces and cutting bevels after the blacksmith has completed the forging and heat treatment.

The finished knife is therefore the result of coordinated work.

The blacksmith establishes the foundation, and the sharpener develops the geometry needed for precise cutting.

Forging gives the steel its initial blade shape, but heat treatment plays a critical role in determining how the finished knife behaves.

After shaping, the steel may undergo carefully controlled heating and cooling processes.

Hardening changes the steel's microstructure to achieve the desired hardness and other mechanical properties.

Tempering, where appropriate, helps adjust the balance between hardness and toughness.

These processes require an understanding of the specific steel being used.

Different steels respond differently to heat, cooling rates, and treatment conditions.

If heat treatment is poorly controlled, a blade may become too brittle, insufficiently hard, distorted, or otherwise unsuitable for its intended use.

This is why the value of a forged Japanese knife cannot be explained by hammering alone.

The blacksmith must make informed decisions throughout the process, from initial shaping to final heat treatment.

The quality of those decisions can have a lasting influence on the knife.

One of the distinctive features of traditional Sakai knife making is the division of work among specialized craftspeople.

The blacksmith is responsible for forging and heat treatment.

The sharpener develops the blade's cutting geometry, refines its surfaces, and establishes the cutting edge.

These roles require different forms of knowledge.

A blacksmith must understand the behaviour of steel under heat and deformation.

A sharpener must understand how blade thickness, bevel geometry, surface finish, and edge preparation affect cutting performance.

The handle also contributes to the finished knife's balance and comfort, with handle making and fitting forming another important part of production.

A beautifully forged blade is not necessarily a beautifully finished knife.

Its final quality depends on the work carried out after forging as well.

At KIREAJI, we believe recognizing these different skills is essential to understanding the craftsmanship behind Sakai Japanese knives.

The finished tool reflects the contributions of more than one specialist.

A well-forged knife is not defined only by visible hammer marks or the fact that it was made by hand.

Some forged knives have polished surfaces that reveal little about their production.

Others retain marks that reflect aspects of the forging and finishing process.

Neither appearance alone establishes quality.

What matters is whether the maker has successfully controlled the material and produced a blade suited to its intended purpose.

Material selection: The steel must be appropriate for the knife's intended use and construction.

Forging control: Temperature and deformation must be managed to establish the desired form without unnecessary damage to the material.

Heat treatment: The steel must be hardened and, where appropriate, tempered to achieve suitable properties.

Blade geometry: The finished shape and cutting edge must support the intended cutting tasks.

Finishing and assembly: Grinding, sharpening, surface finishing, and handle fitting must come together in a practical, well-balanced tool.

These qualities are not always immediately visible.

They are revealed through the knife's construction, the information provided by its maker, and how it performs in use.