What does it mean when a blade is “differentially hardened” or “through hardened”?
Differential Hardening is the process where the blade is heat treated so that the edge is harder than the spine and body of the blade. The spine and body of the blade are coated with a clay mixture, then heated and quenched. Please note that the term “clay tempered” is a misnomer. Tempering doesn’t use clay, it’s the hardening process that does. Tempering is a heat treatment process that softens the steel after it’s been hardened to prevent it from being too brittle.