A katana is a Japanese sword of a single-sided blade with a curved, one-sided tip. The name comes from the word kata (one-sided) and na (blade). The katana’s distinctive curve is based on the fact that the steel used to make it is a combination of high-carbon, which allows for a razor sharp edge, and low-carbon, which provides strength and shock absorption. Sword smiths heated the steel to very high temperatures, but did not allow it to reach a molten state, and then plunged the blade into water in a rapid cool-down process known as quenching. This allowed the two components of the steel to contract at different rates, creating a unique wavy pattern called hamon.
This special forging method also allows a katana to have a very thin edge and be light enough to swing with precision and speed. The katana’s tip can be long (okissaki), short (chukissaki) or hooked backwards (ikuri-okissaki). The exact shape of the blade is an important artistic quality that sword connoisseurs analyze and admire.
Once the blade is complete, a professional polisher, known as a togishi, rubs it with a series of progressively finer stones to create a brilliant mirror finish. This brings out the beauty of the hamon, as well as the unique grain patterns created by the folding process.
Other specialized craftsmen, known as tsuba and koshira, work to create the hilt, guard and scabbard. These elements are often elaborately decorated with gold inlay, intricate carvings and other details that add to the beauty and status of the finished katana. click on this page