Japan is known for producing some of the world's highest quality swords. From the tanto and tachi to the katana and wakizashi, they are characterized by a superior strength, durability and overall quality. Granted, other regions produce swords -- including Korea, China and many European countries -- but Japan has a history of perfecting the swordmaking craft.
One of the reasons Japanese swords are superior is because of their use of carbon. In feudal Japan, swordsmiths discovered that mixing carbon with steel created a stronger blade. Too much carbon, however, made the blade susceptible to rust and corrosion. Therefore, Japanese swordsmiths experimented through trial and error to find the precise ratio that yielded the best results.
Thanks to research conducted by Cyril Stanley Smith, we now have a better understanding of the exact metal composition of traditional Japanese swords.
MIT Professor Analyzes Metal Composition of Japanese Swords
In "The Sword and the Crucible," Cyril Stanley Smith, professor of metallurgical history at the Massachusetts Institute of Technology (MIT) analyzed metal samples taken from Japanese swords throughout the region's history.
So, what did Smith discover? Smith found that Japanese swords produced during the 1500s featured a carbon content of roughly 0.5% at the surface and 0.5% at the body. Japanese swords produced during the 1700s, however, featured a carbon content of 0.69% at the surface and 0.43% body. Japanese swords produced during the 1800s featured a carbon content of 0.62% at the edge and 1% at the body. Finally, Smith found that Japanese swords produced during the 1940s had a carbon content of 1.02% at the edge and 1.02% at the body.
In addition to carbon and iron, the traditional Japanese swords analyzed by Smith also contained trace amounts of manganese, silicon, phosphorus and copper, all of which were lower than 0.5%. These findings reveal a high percentage of carbon content in traditional Japanese swords.
This isn't the only report revealing the metal composition of traditional Japanese swords. In the early 1990s, Jerzy Piaskowski performed a similar analysis on a katana featuring a kobuse-style blade. His findings revealed the katana's blade had a carbon content of 0.6% to 0.8% at the surface and 0.2% at the core.
Today, high-quality swords almost always have at least some carbon content, especially in the edge. A higher carbon content in the edge allows for a stronger blade while still giving the spine some flexibility. This is why the katana is able to flex without breaking or otherwise sustaining damage.