the process of taking a soft <#die>, <#tranroll=transfer roll>, or <#plate> and making it metallurgically hard. In the process of producing <#engraving=engraved> <#stamp=stamps>, the <#design> can only be worked into soft steel, but is generally only transferred from hard steel. The hardening process can be reversed. That is, a hardened die, roll or plate can be made metallurgically soft again.