Pavel Bolf

I am often asked why traditionally made Japanese swords are so expensive. There are several reasons.

Making a Japanese sword is a demanding discipline. The beginning of a swordsman's career is interspersed with failures. Due to the high costs of material and equipment, this is not easy to overcome. Many aspiring swordsmen give up their careers before making their first katana. The time required to master the basics of the craft and the skills to produce a solid longsword blade is at least two to three years. Even after this period, the ratio of successful and unsuccessful attempts is dramatic. After five years of intensive practice practice, the swordsman is able to produce some blades. However, there is still room for improvement in the next ten years in terms of increasing the technical and aesthetic level of the blades produced.

The cost of making a sword. Traditionally made swords are forged from special tamahagane or oroshigane steel. This is reduced in a tartar oven on charcoal. Buying tamahagane from Japan is very problematic. The price of a kilogram of steel is around 100 USD, excluding postage and taxes. About 3-4 kg of this steel is needed for one long sword. A beginner will use it even once. Of course, this amount is needed even for unsuccessful attempts. The production of traditional steel is expensive. First of all, you need to have a furnace for ore reduction. The fuel is charcoal, the price of which is currently about 1 USD per kg. To reduce 10 kg of usable steel, it is necessary to burn about 120 kg of coal and add 25 kg of special iron ore. It is magnetite in the form of iron sand. It must be chemically very clean. It took me 12 years to find a source in Europe for a sufficiently high-quality raw material. The price of the ore itself is not high, a ton costs about 200 USD. Due to the high weight of magnetite, the costs of transport within Europe are quite high and must be included in the price of the final product.

The technological process of steel production itself is not seemingly complicated. However, mastering it to the level of producing quality usable steel requires considerable experience. The steel melting itself then takes about 12 hours, including the preparation of the furnace. (A modern reusable tartar. This furnace was custom made of refractory steel and cost around $2,000) When building a clay or brick furnace that needs to be opened after melting, the cost of smelting is even higher. Not all reduced steel is usable. It must be sorted and the lower quality steel remelted using the oroshigane method. Again charcoal, skill and time required for smelting.

The steel is subsequently processed in the form of blacksmithing. The steel package is cut in half, folded over and welded together at high temperatures. This process is repeated about 10 times. Charcoal is again used as fuel. About 100 kg of coal is needed to process steel into one long blade. Many problematic moments can occur during this process. From the burning of steel, to the occurrence of undercooking and the appearance of defects and unconnected layers in the packet. Excessive decarburization can also occur, thereby devaluing the entire piece of steel. There are many ways to completely devalue the work at this stage.

The attempt succeeds in going through all the pitfalls of steel preparation, the composition of the final package of steels of different qualities, the drawing of the bar and the forging of the blade, the most important and also the most critical step, hardening, is next. Leaving aside the sheer difficulty of mastering this step, we are left with risks. The biggest one (one of many) is the blade cracking during hardening. The blade bends significantly when it cools down and the hardened edge develops a lot of tension. As a result, the blade sometimes breaks. At the beginning of my fencing career, 80% of my production cracked like this. Excessive caution and lowering the temperature then leads to deficiencies in the hamon line. It may be interrupted, or it may not occur at all.

Undesirable deformations of the blade also occur during hardening. Side bends, too much or too little, or uneven bending. This needs to be corrected afterwards. When straightening the blade, its shortcomings may also become apparent and cracks may appear.

Blades take about a week to make. If it is successful on the first try.

Polishing the blade. If we use traditional polishing methods, the cost is high. It is a separate craft that requires several years of practice to master. The material is grinding stones. Fortunately, there are many synthetic stones to choose from these days that will do the job well. However, the final polishing is done exclusively on natural stones. Due to their scarcity on the market, their price is high. Prices range from $1,000 and up. The stones used to shape and grind the steel surface range in price from $60-$200. The basic set contains 6 types of stones. It takes about a week to polish a katana.

Japanese Sword koshirae. Again, this is a separate craft. Actually, several fields. Production of metal parts, production of wooden sword parts, painting, braiding of the handle. For the sake of interest, I will only mention the prices of some materials for the handle. Price of stingray skin for handle wrapping is $70-$300 depending on size and quality. (I don't use low quality at all). Handle braid , leather braid, costs about $50. A simple, unadorned katana kit takes about 2 weeks to make. In the case of an experienced craftsman. However, high-end sets take several months to create and often involve more than one craftsman.

Then there is one important aspect. It takes several years for a beginner to become a good craftsman. Mečiř studies his field all his life. Thanks to practice, he discovers small details that gradually raise the level of his works. When you want to buy a quality blade at a high level of craftsmanship and metallurgy, you don't buy three weeks of work. It is the result of many years of hard work and picking up bits and pieces of skill.

Several types of defects can occur during the folding process. The most common is ware, an unwelded layer in a block of steel. This is most often due to poorly cleaned scaling of the welded surfaces. Scales are formed by oxidation of the heated surface and appear as a thin layer of oxides on it. Some of the scale falls off during forging, pulling out the packet before chopping and folding. Some of the thicker scales then need to be removed mechanically or by water (mizuuchi) when water is sprayed under the packet during forging. This cools and loosens the thin layer from the steel, and the steam generated by the hammer blow between the anvil and the hot packet breaks off the scale. Another option is to use flux (Borax) which melts the scale layer.

The layer is also opened when the packet or the blade rod is pulled out. Especially at lower temperatures and when forging in height, when the impact comes perpendicular to the lay-up.

When the packet is reworked, it can be repaired by filling the spot with flux and re-welding (forging) the spot with the defect. For small defects, it is better to grind off the defect.

Another flaw is Fukure. It is a bubble, air sealed between layers. This shows up first as a darker spot when the packet is forged. When the block is pulled out and the bubble wall is thinned sufficiently, the air expands when heated and can form a bulge, a bubble, on the steel. Either forms similar to a ware when the surface is not sufficiently descaled, where the oxides in the surface prevent the surfaces in the area from welding together and the material fuses in its surroundings. The other possibility is air confinement between the surfaces, where the packet is welded at the edges and air is unable to escape. This can be avoided by thoroughly scanning the packet after chopping and folding the packet before heating it further to welding temperature. Next, when welding the packet, proceed /forge from the fold to the open face of the packet to displace any residual air.

If the fukure occurs during the packet fitting, it is sufficient to cut through the spot with a chisel and thus allow the sealed air to escape. The spot is repaired during the next welding. If the fukure appears during the pulling of the bar and is small, it can be sanded off. However, this means taking material to deeper layers. This may affect the jigane at the repair site and if the blade is shingane, it may break through to the core. In this case, it is better to chop the rod and use it to make smaller blades.

Shinie. They appear as cracks on the edge of the packet or bar. Similar cracks occur when forging high carbon steels or when forging modern and alloy steels at high temperatures (e.g. in the production of welded damascus). When using traditional steels the reasons are the high C content at the beginning of the forging process. Repeated folding of the packet will reduce the C content and the material will stop tearing. When using high C content steel as input material, it is not advisable to encase the packet in ash during welding. This prevents the C from burning out of the steel.

If the tearing of the steel occurs after several folding operations and the grain in the cracks is coarse, similar to sand, this may be due to the presence of undesirable elements (alloys) in the steel. These may already be present on entry (unsuitable ore, contamination by the reducing environment of the furnace) or the chemical composition may be affected by unsuitable coal. For example, oak coal contains sulphur and contaminates the steel during reloading. This becomes completely unusable with more reloading.

With enough reloading, typically 4-5 will homogenize the traditional steel and reduce the C content. The steel becomes more malleable. It is easier to draw and is softer at the fold. However, if the folding is continued more than 10-12 times, the material starts to tear again at the edges. Then the next time it is folded, it degrades very quickly and the cracks get bigger. This unwanted effect is enhanced by wrapping in ash. Basically, this steel is only malleable at lower temperatures. When the bar is pulled out, small cracks form on the edges and edges of the bar. They can be ground off. However, it is questionable whether such steel should be used at all for a sword.

I believe that the ideal number of folding is 8-10 plus the subsequent joining of the steels during the construction of the packet (san mai,kobuse). When chopping and bending the packet, the behaviour of the steel at the chopping point should be carefully observed. Here you can see how the quality of the steel changes. When the packing is smooth and the bend does not tear, there is no separation of layers, the steel is ready for use. With further folding, the bending point is prone to tearing. The viscous elastic material becomes brittle. It is better to stop translating at this stage. (I am not concerned with changes in C content due to overfolding, where excessive overfolding will decarburize the steel and make it unforgeable).

On 9/08/22 I finished an interesting blade. I worked in Soshu style. Hon san mai packet, hardening without clay. Resulting in a choji with a wide nioi and muneyaki at about 70% of the length of the mune. Some would classify this as a hitatsura hamon. 

There are some interesting hitatsura blades among historical swords. Personally, I love the ko wakizashi from Hiromitsu. Massive, generous and confident choji with lots of tobiyaki and muneyaki and utsuri. Some interesting hitatsura are Bizen Osafune, by Sukesada and others. Also well known is a blade by Muramasa with hitatsura in monouchi. Or Hasebe. 

Customers sometimes ask me to create a blade with hitatsura hamon. How to create it?

You can use clay for coding. I don't like this. You have to heat the blade all the way through. In my opinion, such a blade will be hard and brittle. It may be a great work of art, but not a good blade for practice. Coded tobiyaki looks unnatural. They're sharply defined. It's like kitsch. I would try to avoid this way of creating hitatsura or distinctive muneyaki. If you want to use clay, code only ashi. A little denser over the middle of the blade towards the spine. Then heat the blade to an orange color. Let the temperature drop until the color disappears and then reheat as for Ichimonji. It will probably produce a Hitatsura. 

The second possibility is the natural formation of such hataraki. Yakiba. When using clay, it sometimes falls off. That may be the case with Muramasa's blade. I don't think that was the intention.

Without the use of clay, under optimal conditions, a beautiful hitatsura hamon will emerge. The optimum carbon content of the steel, the optimum heating, the temperature of the blade and its distribution at the moment of hardening must meet. Then it is very natural and beautiful. The tobiyaki border is softer to the eye. It's like many things in nature. Natural, beautiful, breathtaking. But we have to rely on chance. We can try and create optimal conditions. Sometimes the reward comes.

Yesterday (12/08/2022) I finished the hardening part of the forging of the Gassan school sword. It's a bit of a different job from other styles of swords. I used shingane steel almost identical to kawagane (blade sides) to compose the final Hon san mai package. But with a marginal carbon content for hardening (about 0.5%) The bar is about 3mm wider at the kassane (11mm) when drawn to the required length compared to the commonly produced blades (8-9mm). The reason for the two differences is the formation of the ayasugi hada. In this case, I used the wave forming forging method.  By pushing two round surfaces against each other, a dent about 1.5mm deep is formed in the rod on both sides. This, after flattening the surface of the bar by grinding it flat to a final 8mm thickness, forms the structure of the steel into a pattern of waves or circles. This process results in a change in the density of the steel in the extruded areas. This may be reflected in the final hamon line shape when hardened.

A typical hamon for the Gassan school is the suguha. My intention was to create a suguha with a broader line of nioi and with moderate activities that would distort the suguha hamon a little. I used a paste of clay (kaolin) and water glass to create the suguha pattern. I noticed that the technique of applying clay is considered very important in Japan. I'm not sure about this sometimes exaggerated approach. Perhaps I am influenced by my favourite and often used Ichimonji style, in which clay is hardly used or only used as a supporting technique. I suspect that some Sōshu style swords were forged in a similar way, with a certain routine and common craftsmanship. The clay only served to support a certain natural pattern, and the hamon was not precisely defined by precise paste coding.

In suguha, the height of the hamon is of course determined by the application of the paste. By raising the temperature a little and staying on it while heating the blade before plunging it into the water, the hamon height under the clay can increase slightly, due to the formation of a coarser and wider crystalline structure of the Nioi line. However, care must be taken. If there is about 0.7%C or more in the steel, then it is highly susceptible to cracking (hagire). This is also due to the tendency of blades with higher C content to bend more when hardened.  At a C content of 0.6%, it is considerably more resistant. My blade had a C content somewhere between 0.6-0.7%C. Therefore, bending it to a higher temperature and heating it longer was a risk. After plunging into water, the blade was significantly bent to about 3.5mm at the axis. I did not hear any cracking though. I immediately removed any residual clay and loosened the blade repeatedly. Tempering is necessary in such a case and as important for the blade properties as hardening. Hardening in water puts a lot of stress on the steel (even for the blacksmith :-))Before tempering, a lot of stress is built up in the blade. Hamon is very hard (62-64). If you don't loosen the blade, it can crack for no apparent reason. It's like a bow permanently stretched to the limit. In use, all it takes is a little contact with an obstacle and the tension exceeds the limit that the steel can bear. Then the blade cracks or breaks. Heating to a temperature of about 250°C will reduce the tension. The bending of the blade after hardening was large, therefore the shudder in the steel was large. Therefore, I repeated the tempering to about 250°C 4 times. The blade deflection decreased by about 0.5 cm during this process. It also reduced the hardness of the hamon. This is important. A hamon hardness of 60-62 is quite sufficient. Very hard hamon is blue in colour. After polishing, it looks like ice or glass. It's very susceptible to breakage. If the blade is heated for a long time during hardening and is not tempered enough, the blade crumbles. Small particles of steel break out. Proper and sufficient tempering of the blade will change the blade properties from critical to optimum. Experience must be used.

The Gassan-style blade I clouded showed a different density of steel on the blade in an interesting way. This was caused by the formation of the ayasugi hada. The hamon edge sometimes tends to follow a wave pattern. In this case it is negligible, occasional and very slight suguha fluctuations. I have made tanto in the past where these changes have completely changed the hamon from suguha to something in the gunome style. It was very pronounced. Combined with Ayasugi, probably attractive as well. 

You can see the whole process of making the blade , including the hardening process described, on my YouTube channel (katana making) after processing the video.

Polishing, adjustments of the final appearance of the structure and steel particles of Japanese sword blades.

The polishing of Japanese sword blades is divided into two parts. The first part is SHITAJI shaping, the second part is SHIAGE polishing.

The main tool for polishing is grinding stones. Natural or synthetic stones are used.  At present, there are synthetic stones replacing all grades for shaping and polishing, except for the final stone UCHIGUMORI and the finger stones HAZUYA chipped from it.

Stones for shaping are ARATO (approx. 180), BINSUI (approx. 220), KAISEI (800-1200),

Stones for polishing are CHU-NAGURA (2000) KOMA-NAGURA (5000) AND UCHIGUMORI (12000)

Also used are the finger stones HAZUYA , which are thin slices chipped from the UCHIGUMORI stone, and JIZUYA, which is chipped from the NARUTAKI stone. JIZUYA is now also available in a synthetic version.

Raw materials for making a Japanese sword blade.

The steel used for traditionally made Japanese swords is one of the factors that make the Japanese sword unique. It is typically made by reducing iron ore on charcoal in a tatara furnace. Another typical characteristic is the chemical purity of the steel thus reduced. In fact, it is an almost pure compound of iron and carbon. Other elements are present in very low levels. Due to the extremely low levels of chemical elements in the steel, these do not significantly affect the properties of the steel.

There are two types of steel used to make Japanese swords. Tamahagane, steel made by reducing iron ore to charcoal in a Tatara furnace. The second type of steel is Oroshigane. This steel is created by remelting unprocessed tamahagane steel of substandard quality or processed traditional steel (products made from it). For example, old nails, fittings, cast iron teapots and so on. Charcoal is used to remelt the steel and is done in a kiln.

The production of Tamahagane steel is quite demanding. It is made in a traditional Tatara furnace, built of clay. It is a shaft furnace with air intake at the bottom. The furnace is filled from the top with a charge of iron ore and charcoal. After the smelting is completed, the furnace must be demolished to remove the molten steel. The size of the furnace is proportional to the amount of steel required. In Japan, steel is currently produced at Shimane in Great Tatara. It produces about 2 tons of steel per plant. Such smelting is very demanding in terms of raw materials and time. The smelting process takes about three days, and a charge consists of about 20-30 tonnes of iron sands and charcoal. The resulting molten Kera steel ingot fills the bottom of the furnace and is about 2m long, 1m wide and 0.5m high. This huge piece of steel has an uneven carbon content. At the edges is high carbon steel with a carbon content of more than 1%. Towards the centre, the content decreases. The core of Kera is made up of low carbon steel with a carbon content of less than 0.5%. For this reason, it is necessary to break Kera into smaller pieces and sort the pieces according to quality. Steel with a carbon content of between 1-1.5% is suitable for sword making. Steel with a lower carbon content can be treated using the Oroshigane method or used for Shingane core steel. Steels with a carbon content higher than 1.5% are very difficult to forge, and as the carbon content increases, forging becomes impossible. Steel that is too carburized will tear during forging and be incoherent. It can be used in small quantities in the construction of the basic steel package for the sword hull. Small particles of such steel create a more distinctive structure in the folding structure of the Serpent. Overly carburized steel can again be modified by the Oroshigane method. Smaller furnaces can be used to increase efficiency in producing quality Tamahagane steel with ideal carbon content. A furnace with an internal shaft diameter of about 40cm and a charge of 30kg of quality iron ore and about 100kg of charcoal, will produce a Keru of 10-15kg after 4 hours of smelting. The quantity and quality of the steel is greatly influenced by the amount of air blown in and of course the quality and purity of the iron ore. Ideally, all Kera is made up of high carbon steel directly usable for processing into Hagane sword blade and sheath steel. Kera weighing more than 15 kg usually already contain steel with a lower carbon content in the core.

Tamahagane weekend 25-26 March 2022.

At the end of February I met with my friends Bitner and Loki and the guys from Knife Z vostra at our place in Pálovice to test the new kiln for tamahagane production. For the reduction we used iron sand, a magnetite of extremely high chemical purity, as the raw material. We smelted in two furnaces. The first one, already tested several times in the past, is made of refractory steel with a fireclay lining with an inner circular diameter of about 40 cm. The air is blown in by one pump.  Load approx. 30 kg of satetsu and 110 kg of charcoal. Reduction time approx. 3 hours without preheating the kiln. The furnace was operated by Bitner. Two melts were carried out. Result of kera approx. 13 kg in the first melt, two compact kera with a total weight of approx. 12 kg in the second melt. In the second smelting, the charge was a combination of satetsu and partially reduced ore from the previous smelting in a large tare. Basically it is magnetite reduced to hematite, which was crushed into small segments of 3 - 1 mm. This material is easier to reduce. This was very noticeable when the slag was repeatedly tapped, which was completely liquid and flowed out of the tapping hole at the bottom of the tartar in a strong stream. When pure magnetite was used, the slag was much denser and flowed out lazily and in smaller quantities.

 The second oven was brick, square base, wall length approx. 60 cm. During the first melting the air was blown in by two air pumps, during the second melting by one air pump. The charge was approx. 40 kg of satetsu and 150 kg of charcoal. Reduction time approx. 4 hours. The furnace was operated by Loki. The first smelting resulted in 4 kera, one high carbon, almost cast iron and three smaller compact kera of high quality high carbon tamahagane weighing 3-5 kg each. The second one-pot smelting was carried out very carefully with minor changes based on the results and experience of the first, test smelting. The result was a huge kera of approx. 20kg and one smaller compact kera of approx. 3kg. The large brick is compact, made up of high carbon steel. There is a smaller protrusion at the top which has not been fully reduced by the ferrous sand. This part of the bark shows the process of reduction, the conversion of iron oxide into steel.

In the second bet, the steel was reduced in almost 70% of the weight of the satetsu used. I consider a reduction with a 30% yield to be successful and usually the results are around 40 - 50% yield due to the extremely high quality of the ore. 

Thanks to smelters Bitner and Loki and the boys from Knife z vostra for their assistance and help. This time I enjoyed the positions of observer, picker, tonger and advisor and served only the grill. Special thanks also to Pavel Holub, who recorded the event and will produce a documentary on it. And of course thanks to Zuzana for her service, background and tolerance of the excesses of the boys playing. And to the assistants Morgana and Sheno.

Tatara and tamahagane.

The use of traditionally made tamahagane steel in the blade is one of the essential features of the Japanese sword. In the last few years, this steel has been referred to as "jewel steel". This designation probably originated outside Japan. This may be due both to the beautiful appearance of the broken pieces of traditional steel and its stunning silver crystalline structure with cavities coloured in shades of blue, purple and gold, but also to the legendary reputation created in Japan. Many sources present tamahagane as a steel with exceptional properties that make it a true Japanese sword. So what is Tamahagane ?