Mechanical 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.

Hot metal typesetting was developed in the late nineteenth century as a development of conventional cast metal type. The technology had several advantages: it reduced labour since type sorts did not need to be slotted into position manually, and cast crisp new type for each printing job. In the case of Linotype machines, each line was cast as a robust continuous block (hence "line o'type") which was useful for rapid newspaper printing. It was the standard technology used for mass-market printing from the late nineteenth century, finally declining with the arrival of phototypesetting and then electronic processes in the 1950s to 1980s.

Two different approaches to mechanising typesetting were independently developed in the late 19th century. One, known as the Monotype composition caster system, produced texts with the aid of perforated paper-ribbons, all characters are cast separate. These machines could produce texts also in "large-composition" up to 24 point.

The Super-caster, another machine produced by Monotype, was similar in function to the Thompson, Bath, pivotal and others casters but designed to produce single type (including even larger sizes) for hand setting.

The other approach was to cast complete lines as one slug, usually comprising a whole line of text.

Of this system there have been at least 5 different enterprises:

The Linotype and similar Intertype machines came out with paper tape and electronic automation near the end of their life cycles that allowed for the news wire services to send breaking news to remote newspaper offices for prompt setting into late editions.

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