These blades are not forged traditionally but are forged just as tough. Unlike differential tempered katana these blades are tempered to an optimal hardness all the way through the spine to the cutting edge. Many are forged with modern "super steels" and "tool steels" that lack the impurities of the traditional sand irons creating true swords worthy of the Japanese samurai. The knowledge acquired by modern sword smiths merged with the smelting ability of today's refineries give us a few hundred years advantage over the swordsman that inspired us. Taking advantage of everything learned from the past with modern technology enables us to produce even stronger and resilient swords for today's martial artist.