HOW IT'S MADE: HONSANMAI TAMAHAGANE
Tamahagane is known as the rarest and most legendary steel ever created. Let us walk you through the process of making our Tamahagane.
Step 1: Collecting iron sand.
As springs flow from the iron mines down the Longquan Mountains they bring iron sand into the Ou River. After digging silt from the river, the mud and sand are washed away, leaving behind pure iron sand. Over 100 kilos of silt needs to be washed to produce enough iron sand for one sword.
Step 2: Smelting
The iron sand is put in a clay tub furnace heated by charcoal fire. When the fire reaches the correct temperature, the iron sand is mixed with charcoal to add carbon to increase the hardness. The steel of 0.6-1.5% carbon content is called tamahagane. Low carbon content tamahagane is used for core steel and high carbon content tamahagane for the jacket steel (outer surface of the blade).
Step 3: Forging
The swordsmith takes a look at the chunks of tamahagane that have formed in the smelting process and chooses the best ones fit for the blade. The chunks are then heated and flattened into thin sheets which are later broken into small pieces. The pieces are stacked together, heated and hammered until they form a bar. The bar is heated and hammered to double the length, then folded and hammered again. This step is repeated multiple times. The folding improves the strength, removes impurities and helps to even out the carbon content. Next the jacket steel is folded into a U-shape, in which the core steel is then inserted. The entirety is heated and hammered to weld the steels together and to lengthen them until a rough outline of a blade is formed.
Step 4: Shaping the blade
Heating the rough blade to high temperatures as well as uniform and even hammering are essential when producing a smooth surface and good blade shape.
Step 5: Rough grinding and filing
To shave off any irregularities or unevenness in the surface of the blade, the swordsmith uses a two-handed drawknife along the sides of the blade. Files are used along the back and the edge of the blade, followed by a rough grinding using a coarse polish stone over the entire blade surface. At this stage the shape of a blade is well defined
Step 6: Making the hamon
The swordsmith mixes clay and water to coat the edge of the blade with thin clay and the back and kissaki with thick clay. The pattern formed by the dry edge of clay is similar to what the hamon will look like after hardening. The blade is heated until it is red hot and then plunged into water. By carefully controlling the heating and cooling speeds of different parts of the blade, the blade gets a soft body and a hard edge. It produces a visible line between the hard and soft steel, the hamon. During the clay tempering process the curve of the blade increases and the smith needs to adjust the curve.
Step 7: Rough polish
Using grinding wheels and series of polishing stones, all the lines (the ridge line, the back and the sides) are cleaned and contoured. The edge of the blade is also ground down and sharpened.
Step 8: Foundation polish
Both foundation polish and finish polish take long time as different type of polish stones are used. The polisher works on the blade section by section. He polishes the body of the blade at a different angle for each grade of the stone he is using. This brings out the hamon and the texture of the steel.
Step 9: Finish polish
In the final polishing stage, finer abrasive materials are used; wafer-thin slices cut from the main stones. The polisher holds the stone between his thumb and the blade, moving the stone lengthwise along the blade in tiny back-and-forth motions. He polishes one section of the sword at a time, beginning at the ridgeline and moving down to the edge, working from the tang towards the point. The hazuya removes all the marks left in foundation polish and the blade takes on a whitish, cloudy appearance. Jizuya stone is used in the same way as the hazuya, although it is harder and finer. After jizuya polish the blade becomes darker and clearer making the jihada stand out. The final step in polishing the surface of the blade is an application of nugui, an iron-oxide suspension used as a very fine abrasive. Nugui is rubbed over the surface of the blade with a piece of cotton. With the surface darkened, the blade’s details become more visible. Hodori is used to enhance the appearance of the hamon. The area between the yokote and the tip are polished separately to make it stand out from the rest of the blade. After burnishing the mune and shinogiji, and polishing the inner surfaces of grooves, the whole blade is done.