Originally Posted by Brian SD
Are you sure this isn't one of the cases where they got the idea from China, then made it a whole lot better?
From what I've heard (and I definitely don't read up on this) the Japanese were far ahead of their time in terms of weapon design, so I have no doubts that their shit was the dankest. But just wondering who the OG nihonjin was who had a sword, and where he got it from.
Japanese swordmaking was driven by the fact that there is very little decent iron ore indigenous to Japan, so the only way to make steel was by heating the crappy iron, hitting it with flux, then folding it and hammering it down. This allowed carbon to infuse the iron (creating steel) and created the beautiful layered look for which the katana
is famous. The characteristic difference in coloration between the edge and spine of the katana
is caused by the differential hardening of the blade, which is hard at the edge and soft at the spine.
As the story goes, the design of the katana
was driven by necessity because the older chokuto
straight blades were unable to defeat the superior armor of the Mongols. In order to make a blade that was strong enough to maintain an edge, but flexible enough not to shatter on impact, the technique of differential hardening was developed. Before the final heat treat, a blade is coated in a clay mixture, then the clay on the edge is scraped off to leave the steel bare. This allows the edge and spine to cool at different rates when quenched.
Chinese blades are not (at least not widely) made with the foregoing techniques because the Chinese had access to better iron ore. Japanese smithing techniques came about in order to turn crap into a decent blade, and the aesthetically pleasing aspects of the katana are just side effects of those smithing techniques.