Tempering was the process of treating a metal with heat in order to strengthen it. In 2268, while observing several axes in a cave on Sigma Draconis III, James T. Kirk noted that the metal it was made of was forged and tempered, and therefore not of Morg origin. (TOS: "Spock's Brain" ) In 2369, Mullibok expressed his wish to finish building his kiln and temper his baking pots. (DS9: "Progress") In 2370, while rehearsing a discussion with his son Alexander, Worf compared a warrior to a sword tempered by experience. (TNG: "Firstborn" )