Back in the early times of sword manufacture, the production of super strong high-grade carbon steel wasn’t even a vague dream. But we know, as history has taught us, that sword makers of ancient times still managed to produce superb quality, strong weapons.
So just how was this possible all those hundreds of years ago? How did these ancient swordmakers manage to craft weapons of such high-quality? What was the secret to this skill of taking poor quality ore and turning it into the finest quality steel blades? Well, it seems the process of Japanese samurai swords making was an highly advanced artform. It wasn’t as simple as casting a sword shape with molten steel and sharpening an edge. What the swords makers would do was to hammer the heated and softened steel flat, and fold it over and hammer it flat again, and repeat this process over and over, maybe by upto as much as thirty times.
This was a very long and labor-intensive process, but in the constant folding and hammering of the steel, it would create internally something comparable to layers. Take a book and fold it parallel to the spine, roll it up and you’ll see what a swords structure inside would look like, and also see how strength increases. This gave the sword a superior strength. As in much of Japanese culture, like Martial Arts for example, many advancements and ways are attributed to emulating natures ways and by observing natures patterns.
It is sometimes thought by some that the idea for this ‘folding’ to create the ‘rings/layers’ inside the samurai sword came about by looking at the cross section of the inside of a tree trunk and observing the way these almost layer like rings of wood gave the tree the strength to stand upto natures forces without breaking very easily, but merely bending with the wind. This is thought by some to be the idea which gave birth to the folded steel concept of Japans samurai swords.