Hot metal typesetting

In printing and typography, hot metal typesetting (also called mechanical typesetting, hot lead typesetting, hot metal, and hot type) is a technology for typesetting text in letterpress printing. This method injects molten type metal into a mold that has the shape of one or more glyphs. The resulting sorts or slugs are later used to press ink onto paper. Normally the typecasting machine would be controlled by a keyboard or by a paper tape.

Row of Linotype operators at the Chicago Defender newspaper, 1941

It was the standard technology used for mass-market printing from the late nineteenth century until the arrival of phototypesetting and then electronic processes in the 1950s to 1980s.[1][2][3]