Hot metal typesetting
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Hot metal typesetting (also called hot lead typesetting or simply hot metal) is a term used to encompass a range of different 19th century technologies to create or compose text for use in the letterpress method of printing.
Generally speaking, this method injects molten type metal into a mould that has the shape of one or more letters, which are later used to press ink onto paper.
[edit] Types of typesetting
Two quite different approaches to mechanising typesetting were independently developed in the late 19th century. One produced characters on individual type bodies, known as the Monotype system; the other, Linotype, created slugs, usually comprising a whole line of text.
Both systems met with success in different fields: the Monotype caster was more popular for bookwork and the Linotype system found success in newspaper production. A manual linecasting solution known as the Ludlow Typograph also met with success because it was able to cast display body sizes that other mechanical composition systems were unable to produce.
The nature of text printed via the hot-metal method is notably different than that produced by the phototypesetting processes that followed it. As the lead type used to print (letterpress)a page had been directly formed from the type matrix a good fidelity to the original was achieved. Phototypesetting suffered (at least in its early days) from many problems relating to optical distortion and misalignment. These disappointing results were a thorn in the sides of many authors and readers (especially of complex or mathematical texts that had many small sub and superscripts). A desire to recreate the aesthetic qualities of hot-lead spurred Donald Knuth to create one of the first general purpose digital typesetting programs, TEX.
Although strictly speaking not typesetting, stereotyping (electrotype or nickeltype) could be used to cast a reproduction of an entire typeset page (or pages imposed in a forme) using a mould made with an impression using flong (similar to papier-mâché). The ensuing casting could be made curved for use on a rotary press or flat for the slower flat bed presses. This technique was often used in newspaper production.