Making a Masterpiece
Forging the sword
After the smith hammers all slag from the tamahagane, he heats the
hard, high-carbon steel and shapes it into a long, U-shaped channel.
He then hammers the tough, low-carbon steel, which he has shaped so
it will make a snug fit into the channel and forges the two metals
together. Both types of tamahagane are now exactly where they need
to be: the hard steel forms the sword's outer shell and deadly
blade, while the tough steel serves as the katana's core. This
perfect balance of properties is what made the katana the samurai's
most durable and prized weapon.