Forging
The forging of a traditional sword is a subtle and careful process, an art that has developed over the centuries in response to stylistic and aesthetic considerations and also to technical improvements. The sword-smith must not only possess physical strength, but also patience, dexterity, and a refined eye for the limits of the material and the beauty of a finished sword.
The forging of a blade typically takes days, and is considered a sacred art. Several craftsmen are involved, including the sword-smith to forge the rough shape, often a second smith (apprentice) to fold the metal, a specialist polisher and finally a fittings expert.
Since the dawn of time Sword smiths have been tasked with producing a weapon that was both flexible enough to survive impacts during combat, but at the same time hard enough to retain a cutting edge. The solution to this problem was the creation of layered steels. This process involves layering alternating plates of Iron rich Raw Steel and Steel. The layers are then forged and folded together in a process known as pattern welding. Pattern welded steel is commonly known today as “Damascus steel”, though it appears that the original Damascus steel was not created with that technique.
In the forging process of a folded blade, we aim to create and item both of beauty and extreme strength. We use two kinds of material for forging a sword, one is Carbon Steel another is Raw Steel produced from Iron rich sand. Iron rich steel being flexible, bends easily, but is too soft to hold an edge. Carbon steel, can be made rigid and hard enough to stay razor sharp, it is also very brittle, to the point that any sudden impact will shatter it. A blade folded 12 times will have more than 4,000 ‘layers’. Further folding increases the flexibility of the blade. Folding burns off impurities and creates a very even and clean composition.
Quenching and Tempering
Differential hardening will be used for most blades giving the blade its ability to take and retain sharpness, one of the most important aspects of a blade. A blades flexibility and strength vary dramatically with heat variations. Depending on how hot and how fast it cools, the steel has vastly different properties. If a sword cools quickly, from a hot temperature, it becomes ‘martensite’, which is very hard but brittle. Cooling slowly it becomes ‘pearlite’, which has significantly more flexibility but doesn’t hold an edge. To control the cooling process, the sword is heated and painted with layers of clay.
A thin layer on the edge of the sword ensures quick cooling. A thicker layer of clay on the rest of the blade causes slower cooling, giving the blade the flexibility it needs (this makes the rear and inside of the sword into pearlite). When the application is finished, the sword is quenched and hardens correctly.
Polishing
When the sword blade has been forged, the swordsmith turns the blade over to the polisher, who polishes the steel of the blade to a shinand sharpens the edge for cutting practice. This takes hours for every inch of blade, and is painstaking work using different kinds of very fine stone. Polishing takes longer than actually forging the blade.
There are two general styles of polishing: modern (invented in the last 100 years) and involves a whitened hamon roughly following the actual hamon, and a darkened body to make the whitened hamon stand out. Traditional is closer to the old styles of polish, and does not attempt to outline the hamon. It more readily reveals details of the actual hamon and crystalline structure compared to modern method.
A blade can be judged by what the polishing reveals: the crystalline structure of the blade becomes quite visible, and the hamon shows the unique nature of the sword. Each blade is distinct in its hamon and the grain of its steel. The hamon, which is determined primarily by how the clay is applied, is often used as a signature of the smith, and each tradition of swordsmiths often have a particular style of hamon it prefers over all others. Hamon vary from straight to wavy to shaped like crabs or zigzags, and they reveal important facts about the blade itself. A good polishing reveals what speed the edge was cooled at, from what temperature, and what the carbon content of the steel is. It does this by displaying either predominately a mix of extremely fine martensite with troostite (another type of tempered steel), or the larger martensite crystals, which look like individual dot-like mirrors.