One of the oldest and also very interesting sword schools is the Gassan school. It is named after Mount Gassan, near which it is located. This school started producing swords in the Kamakura period and its direct descendants are still producing swords today. A distinctive feature is the typical Ayasugi-style steel (hada) structure. This consists of layers of steel formed into distinctive waves. I have had the opportunity to study in detail more than 20 original swords of this school. In the oldest swords (Koto period) the hada is formed with less precision. The waves or circular formations in the steel structure are irregular. This is due to the forming process, which is the extrusion of layers by forging. In contrast, swords of the younger periods and contemporary swords of this school usually have waves formed with precision. The technique of forming the structure in this case is filing, or grinding out the pattern and then interlacing. In Koto swords there is often a marked difference in the texture and colour of the steel in the blade area. The latter tends to be much darker and finer, with a greater density of layers. The colour and texture give a more homogeneous impression. The steel used for the sides of the blade is more pronounced, with a seemingly lower density of translations and a high transparency of layers. This effect is caused by combining steels of different types. In Europe, this technique is used in the production of laminated damascus steel (false damascus).
The aim of the experiment was to create two Gassan-style blades using both snake-forming techniques. The blade with the pierced wave texture is in the gyaku kobuse design. A sheet of layered high carbon oroshigane steel, which is dark in color, is forge welded to a sheet of combined folded tamahagane ( lighter silver color) and oroshigane (dark color) steel, and then bent inward with the more homogeneous oroshigane steel and welded similar to the kobuse style. The back of the packet, which alternates between the transparent combined steel of the sheath and the darker, less distinctive steel of the center, then forms the cutting edge of the blade.
The blade with its forged wave texture is san mai. It is therefore made up of three parts. The sides of transparent, distinctive steel, the centre of darker steel with a less distinctive folding structure.
The hardening, the hamon line, is usually lower suguha in the Gassan school. Utsuri is sometimes found on koto swords. However, it is not the rule. Sometimes the transition between the darker cutting steel and the sheath is considered utsuri. It is possible that utsuri is present on koto blades, but it is only on the cutting steel and the steel of the sheath covers it. This effect is evident on the second blade I made. Here the utsuri only appears about 3 cm from the hamachi in the dark hagane, then it runs under the kawagane and is no longer noticeable. On the first blade, it appears quite prominently as a light shadow in the first half of the blade. However, it is not nearly as pronounced as in the Ichimonji style blades I make.
For both blades, I used clay paste in the hardening process and chose the suguha style of straight hardening line.
I consider the result of the work to be successful. Using different techniques to form the Ayasugi pattern resulted in different hada forms, typical of different periods. It was possible to create two beautiful tanto blades without welding defects, which is not entirely easy in the Gassan style. It is interesting to observe the manifestations of utsuri and the influence of the blade construction or the steel used on it.
The complete production process is documented and will be available in film form.
Both blades are Yoroi doshi style, without the bends. Blade length 29 cm for regular waves, 30.5 cm for forged pattern.
Polishing is done on one side only as a preview to the steel. It is not finished in full quality.
Blades are available if required. The price of the blade in its current condition is 20 000 CZK. In polished condition 30 000 CZK. In a set, depending on the type of set and accessories, specific price by agreement.
Tanto, nagasa cca 20cm, uchi sori, yoroi doshi, uno kubi zukuri sugata, tamahagane steel, itame, ayasugi hada, suguha hamon. Aikuchi dashi zame koshirae, same saya.
Tanto, yoroi doshi hira zukuri. Masame hada, hamon midare, suguha, long kaeri.Nagasa 18cm, kassane 9mm.
Koshirae tanto, dashi zame buke zukuri. Fuchi antique original (Mino ?), tsuba antique, original. Menuki with cricket motif.
Sunobi tanto, hira zukuri, nagasa 32cm. Mino school style blade. San mai construction, itame mokume hada. Hamon gunome. Tanto set, tensho style. Kogatana. Polished sashikomi style.
Tanto, hira zukuri, nagasa approx 26cm, hamon ko-choji, no utsuri. Itame mokume hada. Mix of tamahagane/oroshigane steels. Koshirae dashizame aikuchi. Set includes integrated kogatana ( chóji hamon, masame hada).
Tanto in Ichimonji style, Yoroi doshi kanmuri otoshi zukuri (sugata). Nagasa approx. 27cm. Hamon zubu yaki choji/midare, sunagashi, kinsuji. Hada masame/itame. Polishing in traditional Sashikomi style.
Koshirae dashi zame aikuchi, kogatana (masame hada, ito suguha hamon), copper kozuka. Menuki mikan (oranges).
Blade of O-kogatana, length approx. 18 cm. Material tamahagane own production. Hon san mai construction. Hada itame, ko mokume. Hardening without clay. Hamon choji with very distinctive utsuri choji.
Shira saya set, walnut wood. Simple copper habaki.
Usually the blade of the Kogatana is much smaller and serves as the blade of a knife inserted in a pocket on the ura side of the sword scabbard. This type of kogatana is classified more as a tanto due to its size.
It is a fine example of the sensitivity of steel combined with the skill of the swordsman and their ability to create rich metallurgical effects on the blade. Tempering small and thin blades is very difficult, due to the temperature control in heating the blade before tempering. There is also a high risk of breakage due to the stresses generated during hardening acting more strongly on a thin blade. Polishing is only the omote side, the ura side of the blade is machined with a file. The blade construction of the kogatana is usually kiri-ha, a single-sided ground blade.
The price of a similar blade o-kogatana in shira saya (alder, walnut according to current possibilities) is 15 000 CZK.