However, in most cases, the edge will end up being too hard, so tempering the entire blade evenly for a short time is usually required to bring the hardness down to a more suitable point. The ideal hardness is usually between HRc58–60 on the Rockwell hardness scale. Tempering is performed by heating the entire blade evenly to around 400 °F (204 °C), reducing the hardness in the martensite and turning it into a form of tempered martensite.