In this specific process, referred to as differential hardening or differential quenching, the sword is painted with layers of clay before heating, providing a thin layer or none at all on the edge of the sword, ensuring quick cooling to maximize the hardening for the edge. A thicker layer of clay is applied to the rest of the blade, causing slower cooling. This creates softer, more resilient steel, allowing the blade to absorb shock without breaking.[17][18] This process is sometimes erroneously called differential tempering[16] but this is actually an entirely different form of heat treatment.