Knife making wiki
Heat treatment
Heat treatment turns a shaped piece of steel into a working blade. The steel is heated and quenched to make it hard, then tempered at a lower heat to make it tough enough to use. It matters as much as the choice of steel.
These pages are background reading. Hardening and quenching involve very hot steel and hot oil, so learn them hands-on with a smith on a course.
Temper colours chartTemper colours are thin oxide films that form on clean, bright steel as it is heated: pale straw at about 220 °C, darkening through bronze and purple to blue at about 290–300 °C.Hardening and quenchingA knife blade is hardened by heating it until its structure changes, then cooling it very quickly in oil or water, called quenching.