Katana

A sword has two jobs that pull against each other. It must keep a sharp edge, and that needs hard steel. It must also not snap, and that needs soft steel. Japanese smiths solved the problem by using both. The steel, tamahagane, comes from iron sand that workers smelt in a clay furnace for several days. The smith folds and hammers it again and again to spread the carbon evenly. Then the smith wraps a hard outer layer around a softer core. Before the hot blade goes into water, the smith coats it in clay. The clay is thin along the edge and thick along the back, so the two parts cool at different speeds. The edge turns hard, the back stays flexible, and the blade curves by itself as it cools. The clay leaves a wavy line where it ended. This line is the hamon, and no two are alike.

A samurai wore two swords, the long katana and a shorter companion blade. The pair marked his rank, and by law no one else could carry it. Smiths signed their swords. Families handed them down, and some blades even had names. In 1876, the new government banned people from wearing swords in public. After 1945, the occupying Allied forces seized and destroyed many more. Today sword-making survives as a licensed craft, not an industry. A smith may legally make only a small number of blades each year. Owners treat the best of them as works of art, not weapons.