Once the blade is cut it is slightly bent, so before tempering it in oil we straighten it to restructure the metal. To achieve this we heat the blades in a basket (200 blades per basket) to more than 1000ºC for an hour, then immediately drop them in oil to cool them down. Once the blades are cold they are then reheated to 200ºC for annealing. The blades are shaped to give them their V-edge angle using a special machine to grind the blade.

Annealing: The metal is heated to a temperature near fusion point then slowly cooled to give the steel a homogenous structure.  

Tempering: Now, the metal is heated to a high temperature then quickly cooled in oil to give a highly resistant, but more brittle steel.

Hardening: Once the steel is tempered we heat it gently to reduce the brittleness, which is how we choose the resistance of the blade.

If it is heated for too long or too quickly, the surface of the steel tends to swell. This has an adverse effect on the cutting quality of the blade.To maintain the surface we have to ensure the line at which the status of the metal changes is only crossed slightly, and for a very short length of time. The difficulty comes when this line changes position (height) depending on the content of the steel. This is why we need to achieve temperatures of around 900º/1000ºC.