#TECH_Sword_Crafting
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^The sword has been called the soul of the Samurai. Japanese legend says that the art of Japanese sword crafting was developed by a smith named Amakuni around AD 700. Many of the early blades from this period are long and straight in the Chinese style so it is probably more likely that the folded steel techniques of sword making as well as early sword patterns were imported from China.
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^Japanese swords and other edged weapons are manufactured by the Chinese method of repeatedly heating, folding and hammering the metal flat. This practice became popular and necessary because of the use of low quality Japanese iron ore in the smelting process. In order to counter this, and to homogenize the carbon content of the blades (giving some blades characteristic folding patterns) and to eliminate bubbles and impurities, the folding was developed and found to be quite effective, though labor intensive.
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#DESC_Sword_Crafting
^Traditional Japanese steel is popularly considered to be one of the best for creating swords, but the true reasons for this are artistic and not functional - contemporary western steels were and most modern steels are actually superior in strength and purity. The total composition varied from smith to smith and lode of ore to lode of ore. The high percentage of carbon gave the blade strength while the silicon increased the flexibility of the blade as well as its ability to withstand stress.
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^One of the core philosophies of the Japanese sword is that it has a single edge. This means that the rear of the sword can be used to reinforce the edge, and the Japanese took full advantage of this fact. When finished, the steel is not quenched or tempered in the conventional European fashion. Steels exact flex and strength vary dramatically with heat variation, and depending on how hot it gets and how fast it cools, the steel has vastly different properties. If steel cools quickly, from a hot temperature, it becomes martensite, which is very hard but brittle. Slower, from a lower temperature, and it becomes pearlite, which has significantly more flex but doesnt hold an edge. To control the cooling, the sword is heated and painted with layers of sticky clay. A thin layer on the edge of the sword ensures quick cooling, but not so fast as to crack the sword steel (this makes the actual edge of the sword extremely hard martensite). A thicker layer of mud on the rest of the blade causes slower cooling, and softer steel, giving the blade the flex it needs (this makes the rear and inside of the sword into pearlite). When the application is finished, the sword is quenched and hardens correctly
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^The forging of a Japanese blade typically took days and was considered a sacred art. As with many complex endeavors, several artists rather than a single craftsman were involved. There was a smith to forge the rough shape, often a second smith (apprentice) to fold the metal, a specialist polisher, and even a specialist for the edge itself. Often, there were sheath, hilt, and tsuba (handguard) specialists as well.