Early History of Japanese Metalworking

Metalworking in Japan goes back far. Iron tools and techniques started showing up between the 3rd and 2nd century BCE. That was the beginning of Japan’s metalcraft tradition. One of the most important parts of this history is swordsmithing. The craft of making Japanese swords began before the 1st century BCE and eventually became one of the most respected skills in the country.

Japanese swords weren’t just tools or weapons. They became symbols of power, especially for warlords and samurai. A sword was more than a blade, for it stood for strength, skill, and honor. Over time, sword-making separated itself from regular metalwork. It grew into its own art form, far beyond basic craftsmanship. Even today, Japanese swordsmithing is known for precision, detail, and unmatched quality.

Everyday Metalwork Beyond the Sword

While swords were a big deal, metal wasn’t only used for weapons. Skilled metalworkers in Japan also made tools and items for everyday life. That demand helped push metalworking into new directions. People started using metal for pots, pans, farming tools, and other daily items. This led to the development of many different techniques outside the battlefield.

Traditional Japanese Casting Methods

Japan developed several traditional casting methods over the years. These include rogata, sogata, and komegata. Each one is a unique way to shape molten metal into useful forms. These casting methods were passed down through generations and are still used in some crafts today.

Another method, called smithing, focuses on shaping solid metal by hand. This involves heating up a piece of metal and hammering it into shape. It takes strength, timing, and skill. Japanese smiths used this to make everything from swords to cookware.

Forge Welding: A Core Metalworking Skill

One of the most vital techniques in Japanese metalworking is forge welding. This involves joining two pieces of metal by heating them until they’re red-hot, then hammering or pressing them together. The metal fuses without the need for glue or bolts. Forge welding is usually done with iron and carbon steel and is commonly used to make sturdy tools like chisels and hand planes.

The town of Yoita in Nagaoka City, located in Niigata prefecture, is well known for this method. The local forge welding technique there is called Echigo Yoita Uchihamono. Craftspeople in that area have mastered it and kept the tradition alive.

Metal Decoration and Design Work

Japanese metalwork isn’t just about function. It's also about beauty. To decorate the surface of metal pieces, artists use several methods. These include carving into the surface, inlaying other metals, and embossing designs from the underside. These methods turn simple tools into works of art.

Carving involves cutting patterns directly into the metal. Inlay involves setting different metals into grooves to create contrast and texture. Embossing, on the other hand, raises designs by hammering from behind. These details add personality to every item, whether it’s a sword hilt or a teapot.

Famous Types of Japanese Metalware

Several styles of Japanese metalware are known for their quality and tradition. One of the most well-known is Nambutekki. This type of cast iron comes from Morioka and Oshu in Iwate prefecture. It’s famous for its heavy teapots and sturdy kitchenware. Nambutekki items are made to last and often passed down through families.

Another major style is Takaoka Doki. This copperware comes from Takaoka in Toyama prefecture. The area has been producing copper items for centuries. Takaoka Doki includes everything from pots and pans to statues and incense burners. The craftsmanship is detailed and precise, often mixing both practical use and visual appeal.

 

Early Ironworking in Ancient Japan

The earliest signs of iron use in Japan come from the Yayoi period, which lasted from around 900 BCE to 248 CE. During that time, iron objects like farming tools, arrowheads, and the occasional blade started to appear. Most of the iron used then likely came from Korea or China, rather than being produced locally. It wasn’t until the late Yayoi or the Kofun period that a real ironworking industry began to take shape. As time went on, iron weapons and armor became more common.

But the clearest evidence of actual ironworking methods in Japan doesn’t show up until the Asuka period, which ran from 538 to 710 CE. That’s when the influence of Buddhism reached the Yamato court, and the culture as a whole began to change. Archaeological findings from this era show that iron tools and techniques had become more advanced and widespread by then.

Tatara and the Japanese Bloomery Furnace

Traditional Japanese ironmaking relied on a furnace called a tatara. This furnace worked differently from European and Chinese models. It was made out of clay and built to be used only once. Once it cooled, it had to be broken down and rebuilt before being used again.

The tatara is considered a type of bloomery, but it included bellows like those in European blast furnaces. It was large, and because of its size, the temperature wasn’t the same throughout the whole thing. The heat changed depending on the height inside the furnace. That meant different types of iron formed at different levels. Near the top, where the temperature was lowest, you’d find wrought iron. In the middle was cast iron. At the bottom, where it was hottest, steel formed. Each layer had different amounts of carbon mixed in, which affected the quality and strength of the metal.

Tatara furnaces didn’t get hot enough to fully melt the iron. They topped out at around 1500 degrees Celsius. Instead of liquid metal, they produced a sponge-like mass called a bloom. Inside that bloom were different kinds of metal, and the workers knew exactly where to find what they needed.

How Japanese Smiths Used the Bloom

Metalworkers had a clear idea of how to sort through the bloom. They didn’t know the exact science behind it, but they understood the differences in carbon content and quality. Swordsmiths would pick out specific parts of the bloom depending on what they were making. For katana forging, they chose only the high-carbon and low-carbon pieces. Then they would heat, hammer, and fold the metal again and again. This process was repeated at least ten times.

By folding the metal over itself, the swordsmiths did two things. They spread out the carbon evenly through the steel, and they broke up any impurities. The end result was a strong, flexible blade. The carbon content in these swords was higher than what you’d find in European weapons at the time, but not as high as the carbon levels in Indian steel.

Where Tatara Technology Came From

Tatara smelting is seen by historians as a rare offshoot in the wider story of metalworking. It doesn’t follow the same path as European or Chinese methods. Some researchers think the original idea for the tatara came from Korea. Others point to South or Southeast Asia. The word "tatara" itself doesn’t come from Japanese, which suggests the design wasn’t invented locally.

Still, Japan didn’t just copy the technology. They made it work with the resources they had. While the tatara had some things in common with furnaces found in places like Sri Lanka or Cambodia, the materials available in Japan were very different.

Iron Sand and Local Adaptation

Instead of digging for iron ore in rock, Japan used a resource called iron sand. This sand comes from the breakdown of granite and andesite in the mountains. Rain and erosion carried it down to the rivers and valleys, where it could be collected easily. It didn’t need to be mined from rock, so it saved a lot of labor.

But there was a catch. Iron sand only had about 2 to 5 percent usable iron. In comparison, some rock ores in Sri Lanka contained up to 87 percent ferrous oxide. Because of that, Japanese metalworkers ended up with smaller blooms. That meant they had to get good at combining different blooms to make enough material for their work.

They figured out through trial and error which parts of the bloom gave the best results, especially when it came to swords. The metal at the bottom of the tatara (where the carbon levels were just right) turned out to be the strongest. Swordsmiths focused on collecting and combining those sections to get the quality they needed.

 

Tatara Furnaces and Traditional Japanese Steelmaking

The tatara is a traditional Japanese furnace used to smelt iron and make steel. Over time, the word "tatara" started to refer not just to the furnace itself, but also to the building that housed the whole operation. What makes tatara steel different is the use of ironsand instead of regular iron ore. This ironsand, when processed using the tatara method, became the core material for making traditional Japanese steel.

In the beginning, steel in Japan was made from iron ore. But around the middle of the sixth century, in what used to be Kibi Province, metalworkers started using ironsand. This change helped set the stage for the Bizen school of swordsmithing, one of Japan’s most famous. From Kibi, the ironsand steelmaking method spread across Japan.

In the western regions, metalworkers used a low, box-shaped furnace that was different from Chinese or Korean styles. In eastern Japan, they used both that same low design and a taller, vertical furnace that was uniquely Japanese. These regional variations gave rise to local techniques that kept evolving over time.

Tatara in Japan’s Oldest Writings

The word "tatara" first shows up in Japan’s oldest historical records. In the Kojiki from the year 712, and the Nihon Shoki from 720, it appears in the names of Shinto deities. These names weren’t random. They linked tatara steelmaking with the divine. Different kanji have been used to write the word through history. At first, it was written using characters that meant a "fan," referring to the air-blowing tools used in the furnace. Later, characters meaning "steel works" or "high building" were also used, showing how the meaning shifted from the tools to the whole steelmaking site.

Today, "tatara" refers to the full ironsand steelmaking method that thrived from ancient times through the Edo period.

Improvements During the Middle Ages

As time went on, the process got more advanced. During the medieval period, the furnaces grew larger. Bigger furnaces meant more steel and better quality. Underground parts of the setup became more complex. This helped control temperature and moisture, both important for getting clean, strong steel. A smart new system for collecting ironsand, called kanna nagashi, also came into use. It used flowing water to wash and gather the sand more efficiently, which made the whole process faster and more productive.

Edo Period Advances and the Rise of the Takadono

By the Edo period, the tatara system became more refined. It looked closer to what’s still used today in traditional swordmaking. The whole process took place in a specialized building called a takadono. This structure had two main underground parts: the Hondoko, where charcoal was laid, and the Kobune, a narrow, tunnel-like space underneath. Together, they made up a system called Hondoko zuri, which allowed better airflow and heat control during smelting.

A major invention came in the late 1600s: the tembin fuigo. This was a foot-powered air blower that pushed large amounts of air into the furnace, raising the temperature dramatically. With more heat, workers could produce better steel in larger amounts. This tool changed the game and made tatara steelmaking far more effective.

Tamahagane: Traditional Japanese Steel Smelted in a Tatara

Tamahagane, meaning "precious steel," is the name given to a specific type of high-quality steel used in making Japanese swords. That term wasn’t used until the Meiji Era, but the steel itself has been around much longer. It's still made today using the old tatara furnace method, not in modern factories. Skilled forge masters like Kihara Akira and Gassan Sadatoshi continue this work in places like the Nittoho Tatara, one of the last remaining traditional furnaces still active in Japan.

How Tamahagane Is Made Using the Tatara

The process is completely different from how steel is mass-produced in factories today. It starts with building the tatara itself. A clay box about 1.1 meters tall, 3 meters long, and 1.1 meters wide is built by hand. Once the clay structure dries out, it’s fired to harden it fully. The smelting process begins with a charcoal fire, usually made from soft pine. The smelter waits until the fire reaches the right temperature before adding the raw material: ironsand, called satetsu.

That’s when the hard part begins. Over the next 72 hours, more satetsu and charcoal are added layer by layer. This has to be done constantly, day and night, with a team of four or five people working in shifts to keep the process going. Timing and temperature have to be just right every step of the way. If something goes wrong, the entire batch could be wasted.

It takes about a week to build the furnace and run a full smelting cycle. When it's finished, the clay furnace is broken open to remove the solid steel mass inside. This raw steel bloom is called kera. After three days of smelting and tons of raw material, only a small amount of usable steel is left.

We'll talk more about tamahagane soon...

Raw Material, Yield, and Labor

A single run of the tatara uses up about 9.1 metric tons of ironsand and 11 metric tons of charcoal. That much material results in only around 2.3 metric tons of tamahagane. The yield is low, but the quality is what matters. This type of steel is perfect for forging Japanese swords, or nihonto, which includes the katana. The grain, purity, and carbon content in tamahagane are ideal for blades that need to be both sharp and strong.

The Role of the Nittoho Tatara

In 1977, the Society for Preservation of Japanese Art Swords partnered with Japan’s Agency for Cultural Affairs and a steelmaker called Yasugi Special Steel, a subsidiary of Hitachi. Together, they built the Nittoho Tatara in Shimane Prefecture. The goal was to keep traditional sword steelmaking alive and support the creation of authentic Japanese swords and antique firearms.

Yasugi Works still manages the Nittoho Tatara today. It runs only in the winter months, when the lower humidity helps with temperature control inside the furnace. Every year, it provides a small but important amount of tamahagane to licensed swordsmiths across Japan. Without this process, making swords the traditional way wouldn’t be possible.

 

Origins of Japanese Swordsmithing

Japanese swordsmithing began in the sixth century. It’s a long and detailed process used to make traditional blades, or nihonto. This includes swords like the katana, wakizashi, tantō, tachi, and nodachi, as well as polearms like naginata, yari, and nagamaki. Even Japanese arrows, or ya, were sometimes made using these same methods.

Every sword type has its own look and function. The katana is the most famous, but it’s not the only one that matters. Smaller blades like the wakizashi and tantō were not just smaller versions of katanas. They often had different shapes and no ridge lines at all. One example is the hira-zukuri shape, which is flat and smooth. This was rare on katanas but common on smaller weapons.

Tamahagane: The Steel Behind the Blade

The steel used to make Japanese swords is called tamahagane, which means “jewel steel.” It gets that name because of how pure and valuable it is. Tamahagane comes from satetsu, or iron sand. This material is only found in certain parts of Japan. Tamahagane is mainly used for making samurai swords, but it’s also used in some hand tools.

How Tamahagane is Made: The Tatara Process

The process for making tamahagane is nothing like modern steelmaking. It starts with building a clay furnace called a tatara. This structure is about 3 meters long and just over 1 meter tall and wide. After the clay is fired and dried, a charcoal fire is started inside. Pine charcoal is preferred because it burns at the right temperature.

Once the fire gets hot enough, layers of iron sand and more charcoal are added. This process continues for about 72 hours straight. It takes a small team of four or five people to keep it going. After about a week, the furnace is broken open and the steel bloom inside, called a kera, is removed. This kera contains both high and low carbon steel.

Since the heat never gets high enough to melt the iron completely, the result is a mix of different steels. Once cooled, workers can break apart the kera and sort out the parts they need. Out of about 10 tons of iron sand and 11 tons of charcoal, only around 2.5 tons of kera comes out. And of that, less than one ton becomes usable tamahagane.

A single kera can be worth hundreds of thousands of dollars because of how rare and labor-intensive it is. That makes tamahagane much more expensive than regular steel.

 

The History and Revival of Tatara Steelmaking

Tatara steelmaking using iron sand began in Japan’s Kibi Province in the sixth century. Unlike Chinese or Korean methods, Japanese tatara were low and box-shaped. Over time, furnaces got bigger, and the underground systems became more advanced. By the Edo period, the whole setup, from how the air was blown into the fire to how the building was designed, had been refined.

When Western steelmaking came to Japan in the Meiji period, tatara use started to fade. By the Taisho period, it had mostly stopped. But in 1977, The Society for Preservation of Japanese Art Swords brought it back. Since then, tatara steelmaking has returned, though it’s very limited. Today, tamahagane is made only three or four times a year. It's done during the winter, in a wooden building, and only master swordsmiths can buy it. Hitachi Metals also takes part in this process, helping keep the tradition alive.

The Forging Process: A Team Effort Rooted in Ritual

Making a Japanese sword takes time, usually many days or even weeks. It’s treated like a sacred act. Many parts of the process are tied to Shinto rituals. Forging a blade was once a spiritual duty as much as a craft.

Several people are involved. One smith starts the rough shape. Another may fold the metal. A polisher steps in later to sharpen and smooth the blade. Other experts handle the edge, the sheath, the hilt, and the handguard. Each part of the sword is made by someone who specializes in that one task.

Layering the Blade: High and Low Carbon Steel

The kera pulled from the tatara holds a mix of different carbon levels. Some parts are like soft wrought iron, while others are closer to brittle pig iron. Only about one-third of the kera can actually be used for swordmaking.

Three types of steel go into one blade. The soft, low-carbon steel, known as hocho-tetsu, is used for the core, or shingane. This helps make the sword flexible. The hard, high-carbon tamahagane forms the outer layer, called kawagane. Sometimes, pig iron is melted down again and added as well. That mix of hard and soft steels gives Japanese blades their famous balance - hard enough to hold a sharp edge, but soft enough not to break.

Folding Steel in Traditional Japanese Swordsmithing

One of the most well-known parts of making a Japanese sword is the folding of the steel. This isn't just for show. Folding has a purpose. It helps remove impurities and makes the steel stronger. The idea is simple: heat the steel, hammer it flat, fold it over, and do it again. Over and over.

In old stories and legends, folding is often tied to specific swordsmiths. But this wasn’t just about myth. Folding made real changes to the metal. It spread the carbon more evenly throughout the steel. That mix of hard and soft layers made the finished sword both strong and tough. It wouldn’t snap under pressure, and it could hold a sharp edge.

Purifying the Core, Strengthening the Skin

Swordsmiths usually started with low-carbon iron. This part gets folded many times by itself. The goal is to clean it. That purified metal is used for the core of the blade. It stays soft enough to absorb shock without breaking.

Then comes the outer part. This is made from high-carbon steel and broken-up pieces of cast iron. The cast iron is first quenched in water, then broken into smaller chunks. This helps remove leftover slag. Next, these pieces are piled on top of a plate of high-carbon steel. The entire stack is welded together using heat and pressure. This is called the age-kitae method. The result is a single billet of steel.

Once the billet is ready, it’s stretched out, cut, folded, and welded again. Sometimes the steel is folded from front to back, sometimes from side to side. Many blades use both folding directions to create the right grain. This second stage of folding is called shita-kitae. It's done 8 to 16 times depending on the smith. More than 20 folds aren’t helpful; at that point, the carbon is too evenly spread, and folding stops adding value. Too many folds also make the steel almost uniform, which defeats the purpose.

The carbon levels during folding shape the steel's final use. The hardest steel, hagane, is used for the cutting edge. Slightly softer spring steel, called kawagane, often goes on the sides and back of the blade.

Controlling the Grain and Layering the Steel

Toward the end of the folding process, smiths sometimes create thin steel sheets, stack them like a sandwich, and weld them into a single block. This gives them control over how the steel grain runs through each layer. The direction of the grain is matched to the blade’s structure.

Between each heat cycle, the steel is coated with a mix of clay, water, and straw ash. This mixture protects the metal. It stops too much oxygen from reaching the surface. This helps avoid both oxidation and excess carbon. The clay also creates a reducing environment. At high heat - around 1,650°F - iron oxide forms without oxygen. This is called wustite. The silicon in the clay reacts with the wustite to form fayalite. At around 2,190°F, the fayalite melts. That liquid acts as a flux. It pulls out leftover slag and other junk from the metal. As the layers are hammered together, this sludge gets squeezed out. That leaves a cleaner surface for the next weld.

All this folding burns off a lot of waste. The steel can end up weighing only one-tenth of what it did at the start. This became common because early steel was full of junk. The low heat in old smelting furnaces left lots of impurities. Folding helped fix that.

What Folding Really Does for a Japanese Sword

Folding serves several purposes. It evens out the metal. It burns off impurities. It blends soft and hard steel. The result is a blade that’s strong, flexible, and balanced.

The layers have different carbon levels. When the blade is quenched, the high-carbon layers harden more than the others. That gives the sword a hard edge with a flexible body. The mix of hardness and bendability makes the blade tough and less likely to break.

Folding also closes up tiny gaps or voids inside the metal. That alone improves strength. Plus, it spreads out the elements like carbon evenly, which reduces weak spots. The math behind this blending process is similar to the baker’s map, which is used to model how dough mixes when folded.

Over time, folding can build up tens of thousands of layers. In some swords, there can be over 65,000 layers. That layering not only improves the steel, it also creates the blade’s grain pattern.

Blade Grain Patterns and What They Mean

The grain of the steel, or hada, runs down the blade. This is like the grain in wood. Different patterns show up based on how the steel was folded and cut.

A straight grain is called masame-hada. A more natural, wood-like pattern is itame. If the grain looks like knots or burl wood, it's called mokume. There’s also a rare pattern called ayasugi-hada, which looks like flowing waves. This one is mostly seen in swords from the Gassan school. Each grain tells part of the sword’s story and gives a hint about how it was made.

 

How Japanese Swords Use Multiple Types of Steel

Japanese swords aren’t just folded steel. The best ones are made from several kinds of steel layered and fused together. Each part of the blade uses a different steel type to improve strength, sharpness, and durability. This goes beyond what heat treatment alone can offer.

Modern katanas and wakizashis are usually made using a maru construction. That means the whole blade is formed from a single type of steel. This is the simplest method. In the past, this might have made the sword brittle. But today’s advanced steels are stronger, so even single-steel blades can hold up well.

Another method is kobuse. It uses two kinds of steel: hagane, which forms the cutting edge, and shingane, which makes up the core. Then there’s honsanmai and shihozume, which take it a step further by adding kawagane, a third steel used for the outer layer or skin. These more advanced styles give extra hardness on the outside while keeping a softer, more flexible core inside. Every swordsmith has their own version of how they layer and weld the steels together.

In some methods, the harder edge steel is hammered into a U-shape. Then the softer core steel is placed inside that U. The two pieces are heated and forge welded, then hammered into shape. At the end, both steels are fused into one blade. They stay bonded, but each part keeps its original properties: hard where it needs to be, soft where it needs to flex.

Another way to build a sword is to start with blocks of different steels. The smith forges them together into one solid piece, then stretches it out into the shape of a sword. This allows careful placement of each steel so it ends up where it’s most effective. For example, adding hard steel along the edge and sides helps the blade block attacks without damage. This setup is common in the more complex designs, like honsanmai or shihozume. Swords with even more layers, like soshu or shihozume types with rear support, are rare and mostly seen in antique weapons.

Today, most swords are either made from a single steel or use just two or three layers at most. The more complicated builds are mostly found in older blades or collector pieces.

 

Straight Swords of the Kofun and Nara Periods

Before the familiar curved katana style, Japanese swords looked very different. From the Kofun period through the Nara period, the standard blade was straight and single-edged. This style was called chokuto. These early swords were a mix of Japanese and Chinese influences.

The blade’s cross-section during this time was often shaped like an isosceles triangle. This is known as hira-zukuri. Later, a version called kiriha-zukuri appeared. In this style, only the edge side was ground down at an angle, creating a sharper cutting edge. Blades from this whole early era are called jokoto. These are usually set apart from what we think of today as traditional Japanese swords.

The Warabite Sword and the Birth of the Japanese Blade

Before the Japanese sword took its familiar form, there was the Warabiteto. This was the early ancestor of the katana. Around the middle of the Heian period, between 794 and 1185 CE, samurai began refining this design. That led to the creation of the Kenukigata-tachi.

The Kenukigata-tachi came about in the early 10th century. This blade had a cross-section shaped like a long pentagon or hexagon. It also had a gentle curve and a single sharp edge. These features became standard for Japanese swords going forward. One of its key traits was the ridge line, called the shinogi. When viewed from the side, the shinogi runs between the edge and the spine. It helps reduce the blade’s weight while making it stronger and better at cutting.

Unlike later swords, the Kenukigata-tachi didn’t have a wooden handle. The tang, or nakago, was part of the blade and was held directly. The name kenukigata comes from the hollowed-out part in the center of the tang, which looked like a pair of tweezers once used for pulling hair. That distinct feature gave the sword its name and helped define the early look of Japanese blades.

The Rise of Tachi and the Switch to Katana

After the kenukigata-tachi was developed, swordmakers improved the design by adding a wooden hilt that could be fastened to the tang using a small pin called a mekugi. This change created the basic structure that defines Japanese swords: the curved, single-edged blade with a shinogi-zukuri cross-section, and a tang that locks the blade into the handle. That setup became the new standard for Japanese sword design.

Why Katana Replaced Tachi in the Muromachi Period

During the Muromachi period, warfare changed. Most battles happened on foot, and samurai had to fight against foot soldiers using long spears and even early firearms. The tachi, which was long and meant for mounted combat, became less practical. In its place, the katana became more common. It was lighter, easier to draw, and better suited for close combat.

The katana kept the same basic shape as the tachi (curved, single-edged, with a shinogi-zukuri cross-section) but it was shorter and had a gentler curve. That made it more manageable during fast, ground-based fighting.

The Role of Wakizashi and Tantō

Smaller than both the katana and tachi, the wakizashi and tantō were backup swords. These shorter blades were often crafted with different cross-sections, like hira-zukuri or kiriha-zukuri. These shapes were flatter and simpler but still effective. The single edge of all these swords provided one clear advantage: it allowed the rest of the blade to support and reinforce the cutting edge, boosting durability without losing sharpness.

How Japanese Swordsmiths Used Differential Heat Treatment

The sharpness and toughness of Japanese swords come from more than just the steel. A key part of the process is differential heat treatment. Unlike European swords, which are often heat-treated evenly, Japanese blades are hardened in a way that separates the edge from the spine. This lets the edge stay hard for cutting while the rest of the blade remains flexible.

To do this, the blade is coated in layers of clay before it’s heated. A thin layer or none at all is used on the cutting edge. The rest of the blade is covered in a thicker layer. When the entire sword is heated and quenched, the exposed edge cools fast and becomes martensite, a very hard but brittle form of steel. The covered areas cool slower, turning into pearlite, which is softer and more flexible.

This process is often confused with differential tempering, but they’re not the same thing. Differential hardening is about how fast different parts of the blade cool after being heated. Tempering, on the other hand, happens after hardening and is used to fine-tune the steel’s hardness.

What Happens When a Blade is Quenched

Controlling how the blade cools has more effects than just hardness. It also changes the shape. When quenched, the edge cools first and starts to contract. But since the spine is still hot and expanded, the blade first curves slightly toward the edge. Then, as the spine cools and contracts even more, the sword curves back (this time away from the edge) creating the final arc that defines most Japanese swords.

There’s also a visual result of this hardening method: the hamon. This is the visible line that shows where the hard edge meets the softer steel. It’s not just for looks. The hamon tells you where the hardened portion is, and its pattern often reflects the skill and style of the smith. The way the clay is applied affects the shape of the hamon, so it can serve as a kind of signature.

Sometimes, especially in layered or composite swords, you can even see slight color or texture differences near the hamon. This can reveal how the different types of steel were arranged, like where the edge-steel meets the skin-steel.

Quenching, Tempering, and Final Hardness

Quenching in water has its own challenges. It cools the steel fast, but that also strips away carbon from the surface. That can lower the blade’s ability to harden properly. To avoid cracking and to reach the ideal hardness for cutting, smiths usually quench the blade before carving out the final edge. This keeps the surface balanced and avoids pushing the edge past its limits.

If everything is done just right - perfect water temperature and just the right clay thickness- the blade can harden well enough without tempering. But that rarely happens. Most blades end up slightly too hard, which can make them brittle. So after quenching, smiths usually temper the blade to bring the hardness down a bit.

Tempering means heating the entire blade evenly to around 400°F, or about 204°C. This reduces the brittleness of the martensite without affecting the pearlite. The result is a blade that’s tough enough to withstand impact but still holds a sharp edge. The target hardness usually falls between 58 and 60 on the Rockwell scale (HRc).

Shaping and Finishing the Sword

After the sword is heat-treated and tempered, it’s not finished. The next step is rough shaping. The smith uses a drawknife, called a sen, to start forming the edge and to bring the blade closer to its final shape. Then it goes to a specialist (a polisher).

The polisher’s job is critical. They decide the final geometry of the blade, define the curve, sharpen the edge, and bring out the visual features like the hamon. That last stage not only affects how the sword looks, but how it performs. Every step up to this point leads to a finished blade that balances strength, sharpness, and flexibility.

 

How Traditional Japanese Metallurgy Works

Tamahagane is the main metal used for making Japanese swords, but it starts out full of flaws. It’s not clean or uniform. It’s made using a bloomery process that produces a sponge-like chunk of metal called a bloom. That bloom isn’t one single type of metal. It’s a rough mix of wrought iron, various grades of steel, and pig iron.

Pig iron has the highest carbon content, more than 2 percent. High-carbon steel has between 1 and 1.5 percent carbon. Low-carbon iron comes in at around 0.2 percent. Then you’ve got a middle ground known as bu-kera. That has carbon levels between the two and is often re-smelted with pig iron to make saga-hagane, which averages out to about 0.7 percent carbon.

Not all of this metal ends up in swords. The middle-carbon steel, along with most of the wrought iron and reworked steel, usually gets used for tools, knives, or other common items. Only the best bits, the cleanest high-carbon steel, the purest low-carbon iron, and some select pig iron, are set aside for sword making.

Sorting the Good Metal from the Bad

This raw tamahagane isn’t just a mess of metals. It’s also packed with junk like slag, phosphorus, and other impurities. Traditional smiths had to separate all that. The way they did it was simple but effective. They’d smash the bloom apart with small hammers dropped from a height, then look at the way the metal broke. This was a hands-on test, kind of like the Charpy impact test used today.

Each type of steel breaks in a different way. High-carbon steel, for example, contains pearlite. That’s a microstructure that gives the fractured steel a pearly shine. It’s one of the ways smiths could tell what they were working with.

Folding the Steel to Purify It

Once the good metal was picked out, it still had to be refined. That’s where folding came in. The smith would heat the steel, hammer it out, fold it, then do it again. Over and over. Every time the metal was folded, more impurities got squeezed out. This process didn’t just remove slag and junk; it also spread out the carbon, making the structure of the steel more even.

But there’s a limit. Too much heat for too long and the steel starts to lose carbon. That happens when the heat pulls carbon from the metal and releases it as carbon dioxide. Some of the carbon just spreads through the steel, which helps balance things out. By the end, the steel usually ends up close to eutectoid composition. That means it holds between 0.77 and 0.8 percent carbon, which is ideal for getting the right mix of hardness and flexibility.

The edge steel (the metal used on the blade’s cutting edge) usually stays at or just below this range. That gives the sword enough hardness to hold a sharp edge, but still lets it bend without snapping. The outer layer, or skin steel, usually has a bit less carbon, closer to 0.5 percent. The core, buried inside the blade, stays almost pure iron. That’s why it doesn’t respond much to heat treatment, but adds toughness to the sword’s structure.

What Sword Blades Are Made Of

Metallurgist Cyril Stanley Smith from MIT studied four Japanese swords from different centuries. He analyzed the chemical makeup of each blade’s surface to track how things changed over time. The results show a clear variation in carbon, manganese, silicon, phosphorus, and copper.

The sword from the 1940s had the highest edge carbon at 1.02 percent. That’s a very hard blade. The body of the sword had the same carbon content. It also had higher levels of manganese, silicon, and copper compared to older swords.

The 1800s sword showed an edge with 0.62 percent carbon, while the body had more, up to 1 percent. It had very low manganese and copper. Moving back to the 1700s, the edge had about 0.69 percent carbon, with the body holding 0.43 percent. By the 1500s, both edge and body hovered around 0.5 percent carbon, and other elements like manganese and copper were barely present.

This shows that swords got harder over time as smiths refined their techniques and materials.

Cross-Section Study of a Kobuse Blade

In 1993, researcher Jerzy Piaskowski cut a kobuse-style katana in half to see what was inside. His analysis showed that the surface layer of the blade had between 0.6 and 0.8 percent carbon. That’s in the eutectoid range, perfect for edge retention. The core, though, had only 0.2 percent carbon. That matches up with the idea that the center is made of soft iron to give the blade more flexibility and prevent breaking under stress.

This blend of hard and soft metals is what made traditional Japanese swords so strong, sharp, and reliable. It wasn’t just about the shape or polish. The strength came from deep inside the metal itself.

Recycled Steel in Ancient Japanese Swords

Even in ancient times, Japanese swordsmiths didn’t always work with brand-new steel. Pure steel was rare and expensive. So metal was often reused. Broken tools, nails, cookware, and other scrap metal were melted down and turned into new blades. Even steel taken from enemies on the battlefield was saved and reused. If the metal was strong enough, it didn’t matter where it came from.

This recycling wasn’t just practical. It was necessary. There wasn’t a constant supply of fresh tamahagane. Using what was available helped swordsmiths keep making blades without wasting anything.

How Polishing Reveals the Layers

When a sword is polished, the steel layers often become visible. According to metallurgist Cyril Stanley Smith, these patterns show up for one of two reasons. First, they might appear because the steel layers contain different levels of carbon. Second, the differences might come from how much slag (leftover impurities) is in each layer.

If the patterns are from slag alone, they won’t show any big difference in hardness. You also won’t see any major changes around the hamon, which is the hardened edge of the blade. These slag-heavy layers usually look a little rough or pitted compared to the smoother ones around them. Metallurgist Kuni-ichi Tawara believed that layers with more slag weren’t just decorative. He thought they helped reduce shock and recoil when the blade hit something. Even though slag can make the steel weaker, these layers might have made the sword easier to handle without losing much strength.

Carbon-Based Patterns and the Hamon

When patterns come from carbon differences, it’s a different story. The high-carbon layers are more likely to form martensite when hardened, which is a very hard, brittle structure. The lower-carbon layers turn into pearlite, which is softer and tougher. This creates a clear contrast around the hamon.

You can see this as a streak of bright lines or haze, known as nioi. These lines follow the shape of the layers just behind the cutting edge and continue into the main body of the blade. This gives the hamon its misty or smoky look. It’s a reflection of what’s going on deep inside the metal.

Sword polishers could bring out these patterns using a method similar to lapping. They’d stop just before a full polish to let the textures show through. Sometimes polishing compounds caused chemical reactions that slightly etched the steel, helping the layers stand out more.

The polish also revealed differences in hardness. Harder steel doesn’t scratch as easily, so it reflects light differently. Softer steel scratches more, and those deeper marks change how light hits the surface. Depending on the angle, the softer parts might look dark or shiny, while the harder areas look cloudy or matte.

Metallurgy and Ancient Swordsmiths

Metallurgy as a formal science didn’t exist until the early 1900s. Before that, the only way to study metal was through metallography. That meant looking at the patterns in a blade, studying how it broke, and examining the tiny crystals inside. But even metallography came long after the microscope was invented. The ancient swordsmiths didn’t know any of this.

They didn’t have a scientific understanding of carbon or how it changed steel. Everything they knew came from practice, training, and trial-and-error. Knowledge passed down through apprenticeships. Sometimes sword-making techniques were even stolen from other workshops.

Before the 1300s, Japanese swordsmiths didn’t really focus on the look of the blade’s patterns. They cared more about how the steel worked, not how it looked. But they did pay close attention to how the metal was layered and shaped inside. They understood how to mix steels with different hardness, how to build up strength through structure, and how to create a blade that was strong, sharp, and flexible. They may not have had the science, but they had the skill.

How Japanese Steelmaking Evolved

In the early days, Japan didn’t make its own metal. Nearly all metal objects, including swords and tools, were brought in from mainland Asia. That continued until around the 5th or 6th century, when steelmaking techniques from China started making their way into Japan, most likely through Korea.

One key method Japan tried to replicate came from Chinese crucible steel. This type of steel, known as chi-kang or combined steel, had layers and patterns similar to what we now call pattern welding. In those Chinese blades, a hard steel edge would often be forge welded onto a softer iron back, called jou thieh. That mix of hard and soft gave the blade a good balance of cutting power and flexibility.

When Japanese smiths began studying these swords, they worked hard to reverse engineer them. They didn’t just copy the look of the steel. They studied its behavior. They paid close attention to how different kinds of metal responded to stress and how they could be layered to improve the blade. The goal was always the same: make a better sword than the last one. Many tried to outdo their own previous work, constantly adjusting their methods to get more strength, better sharpness, or improved flexibility.

The hard metal acted like the bones of the sword, giving it strength and structure. The softer metal worked like muscles or joints, letting the blade bend without snapping. This careful blend of metals became one of the core ideas behind Japanese swordsmithing.

When Structure Became Style

In the early days, the differences between the metals inside the sword were often left visible, especially on fittings like the hand guard or the pommel. Smiths would let those parts rust naturally or treat them with acid to highlight the structure inside. The raw surface told a story about how the sword was made. It wasn’t hidden or polished away. It became part of the weapon’s look.

Later on, this visible structure became something smiths tried to recreate on purpose, even when it wasn’t part of the core material. They started using blended metals like copper and steel to make mokume patterns, named for the swirling, grainy look that resembled wood grain. These patterns looked great, but they weren’t strong enough to be used on the blade itself, so they stayed on decorative parts.

The Move Toward Aesthetic Craftsmanship

By the 14th century, Japanese smiths had pushed the limits of blade strength. The mechanical side of the craft had hit its peak. Not much more could be done to make swords harder or more flexible using traditional methods. So from that point forward, swordsmiths began to focus more on beauty.

The change moved toward surface patterns and visible traits. That’s when hamons (the decorative temper lines) started showing up. These were made by shaping the clay coating applied during the hardening process. The heat would hit different parts of the blade unevenly, leaving behind a visible line. At first, these lines were simple waves or small teeth. But over time, they got more complex.

After hamons became popular, smiths began adding other artistic touches. They would hammer small dents into certain areas or stretch out parts of the steel to create textured zones. When the blade was polished, these effects showed up as patterns in the metal. Sometimes, they’d work with high-slag steel on purpose to create visible layers and contrasts.

Swords as Art by the 17th and 19th Centuries

By the 17th century, hamons had turned into real artwork. They weren’t just lines anymore. Some had shapes like flowers, trees, or even pillboxes. Each sword started to reflect the taste and skill of the smith in a more personal way.

By the 19th century, the art form reached a new level. Decorative hamons and folding techniques were combined to show full landscapes in the steel. Some blades showed crashing waves, distant mountain peaks, or islands floating in mist. The sword was still a weapon, but it had become just as much a piece of art. The details told a story, and no two blades were the same.

 

Sword Decorations and Blade Markings

Almost every Japanese sword has some form of decoration, even if it’s not visible right away. After the forging process is done and the mud used for tempering is cleaned off, the swordsmith adds specific cuts and grooves to the blade. These markings aren’t just for looks. Many serve practical purposes, and some are critical for how the sword is judged, especially in terms of value and authenticity.

One of the most important markings is the file pattern on the tang, called the nakago. This is the part of the blade that goes inside the hilt, known as the tsuka. These file marks are added while shaping the sword and are completely hidden once the hilt is in place. Still, they carry a lot of weight when it comes to evaluating the sword.

You’re never supposed to clean the tang. Doing that can destroy proof of the blade’s age and craftsmanship. It can cut the value of the sword in half or worse. The condition of the tang tells you how well the steel has aged over time. It's one of the most trusted signs of a blade’s history.

Types of File Marks and Their Role

File markings come in different patterns. Each has a name and a purpose. You’ll see horizontal, diagonal, and crosshatched styles. Some of the main types include ichi-monji, ko-sujikai, sujikai, ō-sujikai, katte-agari, shinogi-kiri-sujikai, taka-no-ha, and gyaku-taka-no-ha. A crisscross pattern made by dragging the file diagonally in both directions is called higaki. A more decorative version, used for display-grade swords, is called kesho-yasuri.

If the sword is very old, it might not have file marks at all. Instead, the maker may have shaved the tang using a drawknife. This method is known as sensuki. It leaves a smooth, curved surface instead of the usual rough file pattern.

These marks aren’t only for appearance. They create a textured grip for the hilt to slide onto. That uneven surface helps the hilt hold tight to the tang. In fact, most of the hilt's grip strength comes from this pressure fit. The small bamboo pin that goes through the handle, called the mekugi, is really just a backup that adds extra safety.

Other Blade Markings and Groove Designs

Some blades also feature additional engravings or markings. These can include signatures, personal dedications, or decorative carvings of dragons, gods, or religious symbols. These carved images are known as horimono. Some are spiritual. Others simply reflect the tastes or beliefs of the sword’s owner or maker.

One of the most misunderstood features is the blood groove, also called a fuller. Despite the name, it has nothing to do with letting blood flow out faster. Its real purpose is to reduce the overall weight of the blade while keeping it strong and balanced. It helps lighten the blade without making it weaker.

Grooves come in many shapes and styles. A single wide groove is called bo-hi. Twin narrow grooves are futasuji-hi. If there’s a wide groove paired with a thin one, it’s called bo-hi ni tsure-hi. A short groove that ends near the base is a koshi-hi. Twin short grooves are called gomabushi. Long grooves with pointed ends joined together are known as shobu-hi. If the twin grooves run long but break unevenly, that’s kuichigai-hi. And a groove shaped like what you’d find on a halberd blade is called naginata-hi.

Each of these cuts can change how the blade moves and feels. They’re added with care, not just for show, but to make the sword better in function and balance. Whether it’s a groove to lighten the blade or a carved image for personal meaning, these finishing touches are the final steps in turning a sword from raw metal into a complete and refined weapon.

 

Japanese Sword Polishing: What Really Goes Into It

Once a swordsmith finishes forging the blade, the work isn’t over. The sword gets handed to a polisher, known as a togishi. This person’s job is to refine the shape and highlight the blade’s visual features. Polishing a Japanese sword isn’t just surface work. It’s a deep, careful process that can take several weeks, especially with higher-grade swords.

Back in the early days, polishers worked with three types of stones. Today, that number has grown to seven, each one finer than the last. The detailed polishing methods we now see didn’t really exist before the 1600s. Back then, form took a backseat to function. But now, the final look matters just as much as the blade's performance.

The Polisher's Role in Blade Quality

Polishing a sword usually takes more time than forging it. When done right, it brings out the blade’s features and adds real beauty. When done wrong, it can destroy everything. A poor polish can mess up the geometry or grind off too much steel. In those cases, the sword loses its value; historically, artistically, and practically. Some of these swords are one-of-a-kind, and once the surface is damaged or reshaped badly, that loss is permanent.

Polishing Techniques and Surface Texture

With top-level blades, not every part gets the same finish. The back and the flat sides near the spine, called the shinogi-ji, get polished to a mirror-like shine. But the center part, or hira, along with the cutting edge, the ha, is left with a matte surface. This contrast isn’t random. It’s meant to bring out the blade’s natural grain and hamon, the temper line that shows the steel’s internal structure.

These surfaces aren’t smooth in the way a casual observer might expect. There are microscopic scratches left behind from each polishing stone. These vary based on the steel’s hardness. Softer steel ends up with fewer, deeper scratches that reflect light differently than the smaller, more frequent ones left on harder areas. This mix of textures affects how the blade scatters light. The harder areas tend to look more matte and don’t change appearance much under different lighting.

Shitaji Togi: Foundation Polishing

The polishing process has two big phases. The first is called shitaji togi, or foundation polishing. This stage sets the blade’s shape and structure. The polisher uses large waterstones in a series, starting coarse and moving to finer grit. The first step is to check the blade’s straightness. If it’s off even slightly, the polisher has to fix it. That usually involves wooden jigs used to slowly correct bends without causing stress fractures or cracks.

Once the blade is straight, the togishi focuses on shaping the geometry and smoothing out imperfections. Any damage or warping from the forging process gets handled here. Each surface is carefully ground down to prepare it for final touches. The point of the blade, called the kissaki, is its own challenge. It’s small, but it’s critical. The polisher has to divide it into zones and work on them one by one, often switching between tools and techniques.

If the blade has a hi, or groove, that part is polished too, but not with the large stones. Instead, the togishi may use smaller tools, burnishing needles made of hardened steel, or even ultra-fine sandpaper. These areas are too tight and detailed for the big stones and require special care to avoid slipping or scratching beyond the groove lines.

Shiage Togi: The Finish Work

After the structure and shape are set, the final phase begins: shiage togi. This is the finishing polish. It’s where the togishi focuses on visual details, not just function. Every part of the blade is gone over again, but with tools that bring out the contrast between textures, highlight the hamon, and reveal the full beauty of the steel’s grain.

Each movement in this stage is slow and exact. Even the lighting matters. The togishi positions the blade and tools based on how light hits the surface. The final result should bring out every feature clearly and evenly, without glare or distortion. It’s not just about making the sword shine. It’s about making the blade speak, showing the balance, flow, and craftsmanship locked inside the steel.

How Final Polishing Brings Out a Japanese Sword’s True Character

During foundation polishing, modern polishers often use artificial waterstones. These synthetic stones help shape the blade’s geometry. But when it comes to the finishing stage, called shiage togi, that’s where things change. Natural stones are still the only real option here. Artificial stones just don’t cut it at this point; they can’t match the detail or depth that natural ones bring out.

In shiage togi, the polisher shifts focus from structure to appearance. This is where the mirror finish starts to take shape. Unlike the earlier stage, the blade stays still during finishing. Instead, the abrasive tools and stones are moved gently across its surface. The stones are much smaller now, and the polisher slices wafer-thin layers off the main stones for precision.

Each section of the blade is worked on carefully, one part at a time. When the polishing is done, the blade might still look slightly uneven. That’s when the nugui comes in. This is a darkening mixture that evens out the visual balance and adjusts contrast across the surface. One of the final steps here is bringing out the yokote line, the clear border between the tip and the body of the blade. Sometimes it’s restored based on the original line, but often it has to be recreated because earlier polishing erased it.

The last major step is burnishing. This involves fully smoothing and shining the back of the blade and the flat areas near the spine. It’s what gives the final surface its clean, flawless finish. Any visible imperfection ruins the result, so this step is done with extreme care.

What Gets Polished; and What Doesn’t

Not every part of the sword is treated the same. The nakago, which is the tang that fits into the handle, is left unfinished. It keeps the original file marks and is allowed to oxidize over time. This isn’t neglect; it’s tradition. Those file marks help grip the tsuka, or handle, so the blade doesn’t slip out. Where the polished blade meets the rough tang, you’ll see two ledges: the ha machi along the edge, and the mune machi on the spine. These act as anchors for the habaki, the metal collar that holds the blade in the scabbard.

Two Styles of Hamon Polishing

The hamon, or temper line, is one of the most important visual elements of a Japanese sword. There are two main ways to polish it: hadori and sashikomi nugui.

The hadori method is newer. It uses a hadori stone that’s slightly coarser than the stones used in other parts of the polish. This stone brightens the hamon so it stands out more against the blade. But there’s a tradeoff. Hadori doesn’t reproduce the exact shape of the hamon. It traces it loosely, so the final look depends on how distinct the original line is, the quality of the stone, and the skill of the polisher. It works well when the polisher wants a strong contrast, but it’s more of a representation than an exact replica.

Sashikomi nugui, on the other hand, is older and more exact. It keeps the real hamon intact. First, the polisher uses a hazuya stone across both the hamon and the blade’s body, called the jihada. Then a jizuya stone is used to bring out the hada, or grain pattern. After that, the nugui mixture is applied to the whole blade. Nugui is made of powdered materials like magnetite or tsushima and may include other compounds depending on what tone is desired in the steel. Done right, sashikomi nugui makes the hamon glow white while the surrounding areas darken, bringing out clear contrast without changing the original design. This method is only used on blades with strong hamons and well-formed grain patterns.

Why Polishing Matters for Blade Analysis

Polishing is not just about making a sword look better. It’s essential for studying and understanding the blade. The polish reveals every line, curve, and texture. It shows the sword’s shape, its proportions, and all the internal patterns in the steel. These details tell a lot about where and when the blade was made. In fact, a sword’s structure and steel pattern can be a more reliable way to identify the smith than even the signature carved into the tang.

A good polish also shows how the blade was hardened. You can learn how fast the edge was cooled, how hot it was before that, and even how much carbon is in the steel. This is visible in the form of nioi or nie. Nioi is a fine mist of tempered steel, made from small martensite and troostite structures. Nie is made of larger martensite crystals that reflect light like tiny mirrors. Each tells its own story about how the blade was forged and cooled, and both are important for experts trying to trace the sword’s history and quality.

 

Japanese Sword Mountings: Parts and Purpose

Japanese swords aren’t just known for their blades. The way they’re mounted and carried is just as important. Every part of the mounting system has a function, and each one adds to the overall form and feel of the sword. These fittings, called tosogu, aren’t just decorative; they help protect the blade, support the wielder, and reflect tradition.

When the sword is worn, the full decorative mounting is called a koshirae. This includes everything from the handle wrap to the scabbard fittings. It's meant for display, battle, or formal wear. When the blade is not in use, it’s usually kept in a plain wooden mount called a shirasaya. That version has no decorations, just a simple wood scabbard and handle to protect the blade while stored.

Fittings That Secure and Support the Sword

A few key pieces keep the blade locked in and well-balanced. The fuchi sits between the handle and the guard, acting as a collar. The habaki is a wedge-shaped metal piece at the base of the blade. It keeps the sword from slipping out of the saya and helps everything below it stay tight. The mekugi is a small wooden or bamboo peg. It locks the handle, or tsuka, onto the tang of the blade. The holes for this peg are called mekugi-ana.

Then there’s the seppa. These are small washers that sit above and below the tsuba (the handguard), keeping it snug and balanced. Together, these parts help make sure the sword stays in one solid piece while in use.

Handle Design and Details

The handle, or tsuka, is made of wood, usually covered in same-kawa, which is ray or shark skin. This gives texture and grip. That surface is then wrapped in cord, known as tsuka-ito. Traditionally, silk was used, but today cotton or even leather is common. The way it’s wrapped is called tsuka-maki. Common methods include hineri-maki, which is the standard criss-cross pattern, and katate-maki, a style often used for battle. Some handles use more complex patterns like jabara-maki, which is more decorative.

Ornaments called menuki sit under the handle wrap. Originally, they helped hold the peg in place. Later, they became decorative. On some swords like the tachi, they are placed where the palm meets the grip. On katana, they sit under the fingertips. This subtle change helps the user orient the blade correctly by feel alone.

At the bottom of the handle, there’s a fitting called the kashira. It’s like a cap that seals the end and helps keep the wrap in place.

Scabbard and Carrying Features

The wooden scabbard is known as the saya. It’s usually lacquered and sometimes decorated, but the main goal is to protect the blade. The top of the saya, where the sword goes in, is called the koiguchi. This part is often made of buffalo horn for extra strength. The very end of the saya is called the kojiri, also made of horn. It guards the bottom of the scabbard from wear.

On the side of the saya, there’s a small knob called the kurigata. This is where the sageo ties through. The sageo is the cord that secures the saya to the belt or obi while the sword is worn. Some kurigata fittings have a metal accent called the shitodome, which adds a touch of detail, often in gold or brass on modern versions.

A fitting called the kaeshizuno is shaped like a small hook and is sometimes used to lock the saya in place at the belt, making it easier to draw the sword quickly.

Extra Tools and Decorative Pieces

Some swords include small tools or extra fittings built into the saya. A kozuka is a small decorative handle that holds a small utility knife called a kogatana. Another item sometimes found is the kōgai, which is a spike that was once used for hair arranging. Both of these slide into side pockets in the saya and match the overall look of the mountings.

 

What Is a Shirasaya and Why It Matters

A shirasaya, meaning "white scabbard," is a plain wooden mounting used to store Japanese sword blades when they're not being used. It includes a simple wooden saya (scabbard) and tsuka (handle), both usually made from honoki wood, which comes from the bigleaf magnolia tree. This type of wood is chosen because it's soft, breathable, and doesn’t trap moisture like lacquered wood does.

There’s no decoration or external design on a traditional shirasaya, except for the small hole (mekugi-ana) that holds the tang (nakago) in place. Sometimes, people write the blade’s details on the outside of the saya. That’s called sayagaki. But beyond that, the surface is blank and clean. The point of a shirasaya is to keep the blade safe. Long-term storage in a decorated koshirae can actually damage the blade, since lacquer and tight fittings hold in moisture and can lead to rust.

Why Shirasaya Are Not Used in Battle

A shirasaya isn’t meant for combat or wearing. It has no tsuba (guard), no wrapped grip, and no fittings for a secure hold. That makes it unsafe for use in any real fight. You won’t see one on a battlefield. They were never designed for that. But there are some similar types of “hidden” mountings, like the shikomizue, which is a walking stick with a blade hidden inside. While some modern versions of shirasaya include real blades, most are just decorative. A few do have functional steel, but they’re not made for actual use.

Understanding Koshirae and the Parts of a Sword Mounting

The word koshirae comes from the old verb koshiraeru, which means “to make.” That word isn’t used much today. Now, the common term is tsukuru, which also means “to make or create.” But when we’re talking about sword parts, a more accurate term is tōsō, which means sword furniture or mounting. The parts of a sword’s mounting are called tōsōgu, and the metal pieces specifically are called kanagu. The gaisō refers to the outer fittings of the sword, while tōshin is the blade itself.

Each part of the mounting has a job. Together, they protect the blade and help the user control it. While a shirasaya is meant purely for storage, a koshirae is made for wear, function, and even display.

How Koshirae Were Displayed and Worn

There were specific rules about how a sword in koshirae should be shown, especially during peaceful times. The handle (tsuka) should face left. That way, the sword can’t be drawn quickly. It’s a sign that the owner has no intent to fight. But in times of war, the rules flipped. The handle faced right, so the blade could be drawn immediately if needed. This rule became standard during the Edo period, when many sword customs became formalized.

A koshirae wasn’t just functional. It was also a way to show personal taste, social status, or family pride. Many included a family mon or crest worked into the design. These symbols helped identify the owner and added a layer of history to each blade.

 

Tachi Koshirae: Traditional Mounting for Edge-Down Carry

The tachi koshirae was made for the tachi, a sword worn edge-down. It hung from the waist using two hangers called ashi, which were attached to the samurai’s belt or obi. This mounting style came before the katana's rise and shows how early samurai carried their swords. The grip or hilt of a tachi often had more curve than the blade, matching the sword’s shape, which curved more near the hilt than the tip. Tachi hilts were usually held in place with two mekugi pegs. That’s different from shorter swords, like the katana, which usually used just one peg.

Katana Koshirae: The Iconic Samurai Sword Mounting

Katana koshirae is the style most people think of when they picture a samurai sword. In this setup, the sword is worn edge-up, tucked through the belt. This is the opposite of how a tachi was carried. The katana’s edge-up position made it easier to draw the sword quickly, which suited the needs of samurai during the Edo period. This mounting style became the standard for swords used in daily life and combat.

Han-Dachi Koshirae: A Blend of Tachi and Katana Styles

The han-dachi koshirae mixes parts of both the tachi and katana. The sword is worn like a katana, edge-up at the waist, but it includes fittings from the older tachi style. For example, it might have a kabuto-gane, a type of pommel cap, instead of a kashira, which is more common on katana. This mixed style shows how samurai gear evolved over time, sometimes blending past and present designs.

Aikuchi: Close-Fitting Mounting Without a Guard

The aikuchi style is different from most. It has no crossguard between the hilt and scabbard. The name itself means "meeting mouth," because the hilt and sheath meet flush. This design was first used on koshigatana, an early form of the wakizashi. The close fit made it easier to wear under armor. Later on, this style became a status symbol, often seen on tantō blades carried by the upper class, especially from the Kamakura period onward. It gave the blade a clean, sleek look, while staying practical for indoor use or tight spaces.

 

Shikomizue: The Hidden Blade Inside a Walking Cane

The shikomizue, also called jotō, is a hidden sword disguised as a walking stick. The sword is concealed inside a cane-like mount. While best known from films featuring Zatoichi, the concept was real. Shikomizue weren’t meant for open combat. Instead, they offered a way to carry a blade without drawing attention. They should not be confused with the shirasaya, which were plain wooden housings used for storage, not for carrying in public.

Some versions of the shikomizue also hid other items. According to Hatsumi Masaaki, some had chains, hooks, blinding powders like metsubushi, or other hidden tools. These features made them ideal for shinobi, who needed weapons that didn’t stand out. Still, not everyone agrees on how widely they were used. Among traditional martial arts schools, the topic is often debated.

Kaiken: The Samurai Dagger for Self-Defense

The kaiken is a small, plain dagger about 8 to 10 inches long. It could be single-edged or double-edged and was housed in a basic wooden mount with no decoration. Samurai men and women carried it, especially indoors where long swords were hard to use. Women often kept one tucked into a fold of their kimono or hidden in their sleeve.

This dagger was mainly used for personal defense or, in tragic cases, for ritual suicide. In those moments, the user would slash the left side of the neck to cut the carotid artery and jugular vein. The kaiken was simple, but it had a serious purpose.

Saya: The Lacquered Scabbard

The saya is the scabbard. It's made specifically for Japanese swords and knives. Most are carved from lightweight wood and then finished with a coat of lacquer on the outside. This keeps the saya both light and strong.

When drawing or sheathing the blade, the back of the sword (called the mune) should touch the inside of the saya, not the cutting edge (ha). That protects the edge from dulling or damage. On one side of the saya, there’s a small horn knob called the kurigata. A braided cord known as a sageo threads through this.

You’ll often see a decorative metal ring called a shitodome around the kurigata. At the bottom of the saya, there’s an end cap called a kojiri, usually made from metal. Both the mouth (koiguchi) and tip (kojiri) of the saya were often made from buffalo horn for extra durability.

Sageo: The Cord That Binds

The sageo is a silk, cotton, or leather cord that passes through the kurigata. Samurai used it to tie the sword to their belt, or obi. The cord also had other uses, including some in traditional martial arts like hojojutsu, which involved rope-tying techniques.

Beyond function, the sageo held meaning. Many samurai believed it formed a spiritual link between them and their sword. Because of that, they paid close attention to how it was tied and displayed, especially when the sword was at rest.

Kurigata: The Cord Holder

The kurigata is the knob on the scabbard. It holds the sageo in place. The cord goes through a hole in the kurigata and keeps the saya attached to the belt. Though it looks simple, it's a key part of how the sword is worn and carried.

Kojiri: The Scabbard’s End Cap

The kojiri is the metal fitting at the end of the saya. It protects the bottom of the scabbard from wear and adds weight to help balance the sword when sheathed.

Kogatana and Kozuka: The Small Knife and Its Handle

A kogatana is a small utility blade that fits into a hidden pocket on the scabbard. Its handle is called a kozuka. These were often decorated and made to match the rest of the sword’s fittings. Though the kogatana wasn’t used for fighting, it was useful for day-to-day tasks.

Kōgai: The Hair Tool in the Scabbard

The kōgai is a spike that fits into a slot on the saya. Originally, it was used for arranging hair, but it could also be used for small practical tasks. Like the kozuka, it was often decorative and part of the full sword set.

Umabari: Another Hidden Knife

The umabari is a small knife that’s similar to the kogatana. It also fits into a pocket on the scabbard. Though its shape is slightly different, its function was about the same - meant for small tasks, not combat.

Tsuka: The Sword’s Handle

The tsuka is the handle or grip of the sword. It’s built for control and comfort and often includes several layers of materials and fittings. Each part of the tsuka has its role.

Menuki: Hidden Grip Ornaments

Menuki are small metal ornaments placed under the handle wrap (tsuka-ito). Their main purpose is to improve grip by giving the user something to feel with the palm. They also served as subtle decoration.

Samegawa: Ray Skin Wrap

Samegawa is the ray skin used on the handle. Sometimes it wraps the entire grip, and other times just a panel is used. It adds texture and helps the wrapping material stay in place. It also adds to the grip.

Tsuka-ito: The Handle Wrap

The tsuka-ito is the woven cord that wraps around the handle. Traditionally, it was silk. Today, cotton is more common, and sometimes leather is used. It’s wrapped in a crisscross pattern for strength and grip.

Fuchi: The Handle Collar

The fuchi is a metal collar at the base of the tsuka. It’s where the tang of the blade enters the handle. The fuchi helps hold everything together and also gives the handle a finished look.

Kashira: The End Cap

The kashira is the pommel or end cap at the bottom of the tsuka. Along with the fuchi, it helps keep the tsuka secure. It’s often decorated and may match the design of the menuki and tsuba.

Tsuba: The Guard That Balances and Protects

The tsuba is the handguard between the handle and the blade. It’s usually round, sometimes squarish, and comes in many designs. It protects the hand by stopping it from sliding onto the blade during a thrust. It also balances the sword and defines how it feels when held.

The size of a tsuba depends on the blade. A katana’s tsuba is usually about 7.5 to 8 centimeters wide. A wakizashi tsuba is a bit smaller, around 6.2 to 6.6 centimeters. A tantō tsuba is the smallest, ranging from 4.5 to 6 centimeters.

During the Muromachi period (1333 to 1573) and the Momoyama period (1573 to 1603), tsuba were made for strength and use in combat. They were often made of tough metals with simple designs. In the Edo period (1603 to 1868), Japan entered a long stretch of peace. During that time, tsuba became more decorative. They were made from softer, less practical metals like gold, and crafted more for display than battle.

Tsuba: More Than Just a Sword Guard

The tsuba isn’t just a handguard. It’s one of the most personal parts of a Japanese sword. While it helps protect the user's hand and balance the weapon, it also reflects the sword owner's taste, status, and heritage. Most tsuba are carefully made with fine detail. They were often crafted by specialists who focused only on making tsuba. These artisans belonged to entire families or schools that passed down the skill through generations.

Because of that, tsuba became more than just parts of a weapon. They were art. Many were passed down as family heirlooms. Samurai families would sometimes have their family crest, or mon, engraved on the tsuba. That made the guard both personal and symbolic. Today, many of these tsuba are collector’s items. Some are displayed in museums. Others are kept in private collections.

Tsuba were made from a variety of metals. These include iron, steel, brass, copper, and shakudō, which is a copper-gold alloy that darkens with age. Each metal offered a different look and feel, and the choice often depended on function, status, or the time period.

Tsubazeriai: When Tsuba Clash in Combat

In actual combat or duels, swords could lock together at the tsuba. This moment of contact, where both fighters press their guards together and try to overpower one another, is called tsubazeriai. It’s a critical part of fighting, where each swordsman tries to gain the better angle or break the other’s balance.

Tsubazeriai is still seen today in kendo, where fighters often clash guards in tight moments. Outside of martial arts, the word has taken on a second meaning in modern Japanese. It’s now used to describe any intense face-off or tight competition between two sides.

Seppa: The Small Washers That Secure the Guard

The seppa are small washers placed on both sides of the tsuba. They help keep the fittings tight and prevent the parts from moving around during use. Some seppa are plain, made just for function. Others are decorative and match the sword’s overall design.

Even though they’re small, seppa are important for the overall fit of the koshirae. If they’re too thin or too thick, the sword can feel loose or tight in the hand, which can throw off handling and balance.

Habaki: The Metal Collar That Holds It All Together

The habaki is the metal piece that wraps around the base of the blade. It has two jobs. First, it keeps the tsuba locked in place. Second, it secures the sword when it's sheathed in the saya. Without the habaki, the blade would slide around or fall out of the scabbard.

When drawing a katana, the thumb presses against the tsuba while the hand holds the top of the saya. This motion breaks the seal between the habaki and the inside of the scabbard. That process is called koiguchi no kirikata, which means “cutting the mouth of the scabbard.” It frees the blade just enough to draw it fast. That quick draw has different names depending on the context: koiguchi o kiru, nukitsuke, or tanka o kiru.

Over time, tanka o kiru became a common expression in Japanese. It means to get ready to act or speak, usually in a bold or confrontational way.

Maintaining the Habaki and the Scabbard Fit

The habaki rubs against the inside of the saya every time the sword is drawn or sheathed. That creates normal wear. After a while, the fit may loosen. When that happens, you may need to add a shim or even replace the saya entirely to restore the tight fit.

It’s also smart to remove the habaki every few months to clean and oil it. If the sword is used for cutting practice, it should be done even more often. Keeping it clean helps prevent rust and keeps the fittings working smoothly.

 

Modern Japanese Swordsmithing Today

Japan still produces traditional swords today. These swords, called shinsakuto or shinken (which means "true sword"), are crafted using the same traditional materials and techniques that have been passed down for centuries. These are not knockoffs or replicas. They are real, high-end swords. Because of the time and effort involved, they often come with a steep price tag.

To legally make swords in Japan, a smith needs to be licensed. Getting that license is not easy. It takes years of hard training under a master. Outside Japan, there are only a few smiths who follow similar methods. Some offer short classes in traditional Japanese sword-making, but those are rare and usually don’t cover everything.

Cheap Replica Swords and Mass-Produced Blades

You can find tons of cheap replica swords online or at stores. They might look like katana or wakizashi, but most are poor-quality imitations. Prices usually fall between $10 and $200. These are not real swords. They're made by machines, often sharpened by machines too, and they aren’t properly hardened or treated.

The "hamon" line that you see on these blades is often just cosmetic. It’s added by scratching, acid etching, or stamping, not by actual tempering. That means the edge isn't any harder than the rest of the blade. The material used is usually cheap stainless steel. It looks shiny but performs terribly. It’s too hard and brittle, which makes it likely to crack or break if used.

Decorative swords in this range often come with flashy designs and extras. But again, they’re for display only. You should never use them for cutting or martial arts. They’re not safe.

Mid-Range and High-End Reproduction Swords

If you're looking for a functional replica, you’re entering a different price range. Decent quality reproduction katana usually cost between $200 and $1000. Some go over $2000 if they’re folded, properly heat-treated, and polished the right way. These are built for real use. They’re made to handle cutting and movement.

High-end reproductions can cost $15,000 or more, especially if they're custom-made. These blades are often crafted from carbon steel. They’re hardened at the edge while keeping the spine softer, just like traditional katana. This process makes them tough and flexible at the same time. The visible hamon is real, not faked. However, most of these blades won’t show hada, the grain pattern, since they’re usually not folded like tamahagane blades.

Types of Steel Used in Modern Reproduction Swords

Many different types of steel are used for modern swords. You’ll see carbon steels like 1020, 1040, 1060, 1070, 1095, and 5160. Stainless steels like 400, 420, and 440 are also common. Some of the best blades use high-end steels like L6 or S7, which are known for strength and durability.

Most cheap replica swords are made from 440A stainless steel. It’s often just labeled “440.” It has a high Rockwell hardness, usually 56 to 60, which sounds good on paper. But it makes the sword more brittle. The back of a real katana is softer, around HR50, and the edge is harder, over HR60. That balance helps the blade flex without breaking. Stainless steel doesn’t have that balance.

Wall-hanger swords are especially dangerous. They’re not built to take impact. Many of them have a rat-tail tang, which is just a skinny metal rod welded to the blade under the handle. That weak spot can snap under pressure, making the sword useless and dangerous.

Where Modern Swords Are Made

Some modern smiths outside Japan have figured out how to make real swords using traditional methods. One Japanese smith even started making swords in Thailand, following the same steps used in Japan. American and Chinese manufacturers have also produced high-quality reproductions.

That said, swords made outside Japan will always be different. Japan doesn’t allow raw tamahagane steel to be exported. It has to be turned into a finished product before it leaves the country. Because of that, overseas blades can’t match Japanese swords exactly, but they can still come close.

Some swordmakers offer differentially tempered blades folded in the traditional way for between $1000 and $3000. Others sell strong, well-tempered swords that aren't folded, usually for several hundred dollars. These are practical options for people who practice martial arts.

In fact, some martial artists prefer modern blades. These are often designed to be lighter, so they’re easier to swing for long periods. Some are built with thinner profiles and razor-sharp or hollow-ground edges for clean cuts through practice targets. These aren't display swords. They're built for use.