The samurai katana is one of the true swords of legends. The Katana was produced using forging techniques that were far ahead of it's time. When katana were being produced they were made from very dirty and impure sand iron, known as tamahagne. In order for the sword to be strong they needed a way to purify the steel and the folding method was born. Aside from its aesthetic beauty, the purpose of folding the steel was to bring the impurities to the surface and removed. This was done during blade forging and set the foundation for some of the toughest swords ever to be wielded by the Japanese samurai.