Katana

Trivia  

• A Katana is actually a Bi-metallic blade. Its edge is made with a hard steel, so as to stay sharp, and its core is a softer iron, to give it flexibility. 
• Traditional Katana are produced using a special steel called Tamahagane. Tamahagane takes three days to produce in a special furnace known as a tatara.     
• In ancient Japan, Katana were tested using criminals and prisoners of war. Depending on the crime, the prisoner could be sentenced to lose an arm, a leg or to be executed using the new blade. 
• A well made Katana would be capable of slicing clean through a human body in a single strike. If a sword could cut through a single person it was referred to as a "One Body Blade". However there are Katana in existence that are marked as two and even three body blades.  
• In 16th century Japan there were 5 sword-smithing schools that thought the skills to make a Katana. Those 5 schools still exist today.  
• The Katana's iconic shape is a result of the hardening process. Before hardening, the sword maker coats the blade in a layer of clay and charcoal powder. This clay layer is known as the Hamon.  A thin layer on the cutting edge and a thick layer on the back edge. The sword is heated to red hot ( the sword-smith determines the temperature by the color of the metal) and then quenched in water. The area covered in a thin layer of clay cools rapidly followed by the thicker covered layer. The slower cooling back edge then pulls the Katana into its famous curved shape.
• Using traditional methods, it takes 6 months to produce a single Katana, three months to forge and roughly polish the sword and a further three months for the sword to be finely polished by a master polisher. After the fine polishing the sword it then returned to the sword-smith to be finished with its handle and scabbard.
• Through repeated folding and hammering, the carbon content of the steel is driven down. As a result the final sword weighs roughly 50% less than the raw materials used to make it.