Forging a Katana

Japanese swords, or katanas, were frequently manufactured using various sorts of profiles, different blade thicknesses, and changing measures of grind. The shorter swords, Wakizashi, for example, were not just downsized copies of the katana, but they were regularly fashioned in the style of hira-zukuri or other such forms which were exceptionally uncommon on different swords even to this day when looking at the forging of a katana.

What is a daishō ?
The daishō, meaning a complete set of 2 swords – 1 katana and 1 tanto or wakizashi, was not always forged together. It was more the norm that when a samurai could bear the cost of a daishō, the set of swords was normally made up of whichever two swords he could get his hands on, often forged by different swordsmiths and in various styles and forms.

In cases when a daishō contained 2 blades produced by the same swordsmith, they were not always manufactured as a couple or mounted as one with the same fittings and ornaments. Therefore a Daishō made as a couple, mounted as a couple, and worn as a couple, are exceptional and have high value and thought of as very significant, particularly in the event that despite everything they still have their unique mountings and fittings instead of later mountings, regardless of whether the later mountings are made as a couple.

Traditional forging and folding of steel katana

How long does it take to forge a traditional katana?
It was customary for the production of a Japanese blade to take many weeks and even many months to complete, as this was considered a very sacret artform and taken extremely seriously by both the buyer and seller. When you think about it this makes much sense, as you would be trusting your blade with protecting your life.

Just as when you are working on complicated projects, it is important to include expert persons and not do everything yourself. The same went for forging a katana. There was a smith to fashion the crude shape, frequently a second smith (disciple) to bend and fold the metal, a polisher (called a togi) just as the different artists that produced the koshirae (the different fittings used to improve and decorate the completed blade and saya (sheath) including the tsuka (hilt), fuchi (collar), kashira (pommel), and tsuba (hand-guard).

It has often been said that the entire processes of sharpening and polishing a katana is supposed to take just as long as the production of the metal blade itself. So yes the entire process of forging a traditional katana would take from a month but could take almost up to a year or more.

The steel and method used for forging a katana
The genuine Japanese sword is produced using the authentic Japanese steel called “Tamahagane“. Normally the blades of the katana are formed using a lamination strategy of blending two unique types of steel, where the swordsmith would use a harder external coat of steel folded over a softer inner core of steel. This makes a katana blade which has a hard, dangerously sharp edge with the capacity to assimilate stuns and blows in a way which lessens the likelihood of the blade breaking and chipping when crossing swords in battle.

The hadagane, for the external coating of the blade, is made by heating up a square of crude steel, which is then pounded out into a bar of steel, and then cooled down and separated into much smaller squares which are checked for further impurities of the steel and afterward reassembled and reforged. Amid this procedure the block of steel is heated up and pounded, split into smaller squares and folded upon itself many many times to create a katana blade with thousands of layers. Each type of steel is folded differently and sometimes in an unexpected way in order to optimize strength, endurance and flexibility of the specific type of steel used.

Different types of katana lamination methods combining hard, medium and soft steel.

The exact manner by which the steel is folded, pounded and re-welded decides the unique pattern and grain of the finished blade, the pattern is referred to as jihada, an element which gives a strong indication of the time period, location of production and naturally the person who has produced the blade.

Folding and hammering the steel for the katana blade
The act of folding the steel itself, likewise guarantees to some degree, a progressively uniform item, where the carbon contained in the steel is being distributed evenly throughout the metal blade, and the steel having no air-pockets or weaknesses that could result in fractures and breaking of the blade when tested in battle.

The shingane (for the center of the katana-blade) is normally of a moderately softer type of steel with a lower carbon content than the steel used for the hadagane. For this, the square of steel is hammered, folded and then welded just like the hadagane, however with less folds. Now, the hadagane square of steel is indeed heated up, hammered out and folded into a ‘U’ shape, into which the shingane is then embedded to a point just before the tip. The new composite block of steel is then warmed up and again hammered out guaranteeing that no air or impurity is present between the two combined layers of steel.

The bar of steel will get longer and longer and take a curvy shape during this working procedure until it is just about the size and the shape of the completed sword blade. A triangular segment is cut off from the tip of the bar and molded to make what will be the kissaki. Now at this point in the process the blade has a rough shape and is referred to as a sunobe.

Heating and Folding the billet of steel for a katana blade.

The sunobe is again heated up, part by part and hammered again to make a shape which looks almost like a finished katana blade. The swordsmith’s expertise now becomes an decisive factor as the hammering procedure makes the blade curve naturally, the thicker back tending to bend towards the more thin edge, and the master must carefully control the shape to give it the needed upward curve. The sunobe is completed by seemingly endless scraping and filing, ending up showing off all of the finished physical attributes and curve we know from the completed katana.

The surface of the steel blade is left in a generally crude state at this point, prepared for the processes of hardening to come. The sunobe is then completely covered with a unique blend of clay more thickly along the back and sides of the blade than along the edge itself. The blade is left to dry while the master swordsmith prepares the furnace for the last heat treatment of the katana blade, the yaki-rage, the hardening process of the edge of the blade.

This entire procedure traditionally happens in an swordsmith’s workshop at evening or nighttime when there is less light which gives way to shadows and contrasts more easily. In this atmosphere and lighting, the master smith can make decisions by eyeing the color and glow of the steel and thereby the temperature of the blade when it is heated over and over again in the furnace.

When the time feels right in the process of forging a katana, the hot steel blade is plunged into a tank of water with the edge facing downward and the point forward. True to tradition, it is said that the blade should be the color of the moon in February or August which are the two months of the year that are seen most commonly dated in engravings on the tang. The exact time taken to heat the katana, the temperature of the blade and of the water into which it is plunged are altogether extremely individual to each sword-smith and they are well kept secrets.

There is a legend telling tales of a specific smith who brutally removed his disciple’s hand for testing the temperature of the water he used for the hardening procedure. In the different schools of swordmakers there are numerous unique varieties in the materials used in manufacturing a katana. The different procedures and methods mentioned earlier, especially when it comes to the clay used to cover the blade before the yaki-rage, yet all swordsmiths use a similar work method.

The application of the unique clay mixture before the final heat treatment.

The use of the clay in various thicknesses to different parts of the blade enables the steel to cool off faster along the part with a thinner coating of clay when plunged into the tank of water and consequently form into the harder type of steel called martensite, which can be filed to razor-like sharpness. The back covered with a thicker clay coating cools off more gradually gaining the pearlite steel attributes of medium softness and flexibility.

The exact way by which the clay is smeared onto the blade and scratched off at the edge, is a deciding factor of the shape and highlights of the structure known as the hamon. This unmistakable tempering line found close to the sharpened edge is one of the fundamental parts you should examine when determining the quality of a katana blade.

The martensitic steel which can be noticed from the edge of the blade up to the hamon, or temper line, which is basically the naturally occurring transitional line between these two distinct types of steel, and is the place where most of the beautiful colors, patterns and uniqueness of the Japanese sword are to be found. The shape and structure of the hamon reveal what time-period it was produced, the swordsmith himself, and also what school or place the blade was manufactured. But besides the purely beautifying characteristics of the hamon, there are a few truly practical ones.

The harder edge will normally be taking most of the stress and potential harm to the blade in battle. This hardened edge can be filed and sharpened again many times, in spite of the fact that this will change the shape of the blade.

A real Hamon, or temper line, showing unique texture and pattern.

Practically all sword blades are decorated to some extend, as the sword-smith will leave his marks and often engravings, but not all katanas are decorated on the visible parts of the blade. When the blade has cooled off and the clay has been scratched off, grooves and markings (hi or bo-hi) might be added to it. As one of the most vital marks of the katana are the so called file markings, and they are cut into the tang or the handle area of the blade, where they will be covered by the grip later. The tang is NEVER TO BE CLEANED, and doing so can diminish the value of the katana by 50% or even more. This is to ensure and preserve the original steel and to show how well the steel ages.

Other markings on the blade are purely for show and artistic worth. such as writing in Kanji characters and also engravings called horimono portraying divine beings, mythical serpents, or other godly creatures. The hi and bo-hi however are very practical markings, as they lessen the weight of the katana while keeping the structural strength and sturdiness.

After the blade is produced, it is then sent to be cleaned and polished which takes somewhere in the range of one and three weeks. The polisher uses a series of polishing stones with progressively finer and finer grain in a procedure called coating, until the blade has a finish you can see your own reflection in like a mirror, while the dull edge of the katana is normally given a matte complexion to really show off the hamon.

Check out this video about forging a katana the traditional way.

Read about the history of the katana
Read about the parts of the katana
Read about how to hold a katana
Read about training with a katana – The basics
Read about training with a katana – Advanced