Making a Masterpiece
Coating the katana
While the katana's body is now complete, the swordsmith's work is
far from over. Just prior to firing the sword a final time, he
paints a thick, insulating mixture of clay and charcoal powder onto
the blade's upper sides and dull back edge, leaving the sword's
sharp front edge only lightly coated. This serves both to protect
the blade and to give it its signature wavy design called the
hamon, which later polishing will reveal. The swordsmith then
places the katana back into the fire to be heated to just below
1,500°F; any hotter and the sword might crack during the next
step.