Japanese Knifemaking Process
1. File Polishing The soft iron is heated so it can be bonded with the steel. While the soft iron is hot, it is hammered and combined with the steel using iron oxide, salt peter, and nitrate as adhesives.
2. Attaching Core Molding During hammering, the basic shape of the knife is formed. The soft iron and steel is stretched and fused. It then goes back into the fire.
3. Shaping The handle of the knife is also made by hammering and stretching. Once the shape of the handle is complete, the whole knife is hammered into shape.
4. Annealing It is slowly cooled in straw ash then heated again in the furnace. By doing so, the steel becomes soft and eliminates internal strain.
5. Quenching After heating in the furnace, it is rapidly cooled in water. This increases the hardness in the steel.
6. Tempering By heating the knife in low temperature for the last time, it gives the steel strength and resilience.
7. Rough Grinding Grinding the edge of the knife forms the blade. By hand, the knife is pressed onto a fine grinding stone. The edge is sharpened and made smooth by using back and forth movements.
8. Handle Attachment The polished handle and knife are combined.