A samurai's sword was his most sacred and prized possession, and weapon collectors still consider it one of the most important weapons in history. To a samurai, his sword was his primary defense weapon, and he believed his soul lived within the sword. With such significance placed upon the sword, it should be no surprise to learn that the same discipline and respect went into the making of the sword.
Samurai swords were not simply cast in a mould and then sharpened. They were made by an intricate process of heating, hammering, and folding the steel. This cycle of repeated hammering and folding would be done as many as 30 times, or until the maker was satisfied the blade was ready.
This labor-intense annealing-layering process eliminated any air pockets that might have developed during heating of the steel, which would create weak spots in the blade. The process also hardened the carbon in the steel and spread any impurities throughout the sword, strengthening the steel even more.
If steel cools from a high temperature to cold in a short period, the metal becomes very hard, but brittle. Conversely, if it is cooled slowly, it becomes softer and suppler. Samurai swords were used primarily as a slicing weapon, so the blades were subjected to severe shock upon impact. It a blade was brittle, it might shatter on contact. However, if it was made too supple, it would not hold an edge. This created a dilemma for the sword makers.
Japanese samurai sword makers discovered that by painting a thin layer of a clay formula onto the cutting edge, and a thicker layer onto the back the blade, before cooling the blade, the steel would have a hard cutting edge but a supple back. Because of the different speeds at which the two areas of the steel cooled, the blade developed a natural curve that the sword makers then worked to create the famous curved blade of the samurai swords.
Instructors create black belts in much the same way that swords were created
Some black belt makers merely cast their black belts in the same moulds that made them, so any imperfections in them are passed on to their students. This process allows many black belts to be created in a short period. These black belts are only as good as their instructors; they do not hold their edge and, when worked too hard, they tend to break.
Skilled samurai style black belt makers know that there are impurities in the teaching process, so they forge their students over many years, pounding them into hardened steel. Along the way, they teach their students the “way” of the martial arts, so that, even though they can be ruthless when required, they can also be sensitive and caring. Skilled black belt makers work with the natural curve of the students and develop them in ways that complement their natural abilities. These black belts stand the test of time and remain true black belts until they are no longer needed in this life.