Compositor (typesetting)

Typesetting is the composition of text by means of arranging physical types or the digital equivalents. Stored letters and other symbols (called sorts in mechanical systems and glyphs in digital systems) are retrieved and ordered according to a language's orthography for visual display. Typesetting requires the prior process of designing a font (which is widely but erroneously confused with and substituted for typeface). One significant effect of typesetting was that authorship of works could be spotted more easily, making it difficult for copiers who have not gained permission.

During much of the letterpress era, movable type was composed by hand for each page. Cast metal sorts were composed into words, then lines, then paragraphs, then pages of text and tightly bound together to make up a form, with all letter faces exactly the same “height to paper”, creating an even surface of type. The form was placed in a press, inked, and an impression made on paper.

During typesetting, individual sorts are picked from a type case with the right hand, and set into a composing stick held in the left hand from left to right, and as viewed by the setter upside down. As seen in the photo of the composing stick, a lower case 'q' looks like a 'd', a lower case 'b' looks like a 'p', a lower case 'p' looks like a 'b' and a lower case 'd' looks like a 'q'. This is reputed to be the origin of the expression "mind your p's and q's". It might just as easily have been “mind your b's and d's”.

The diagram at right illustrates a cast metal sort: a face, b body or shank, c point size, 1 shoulder, 2 nick, 3 groove, 4 foot. Wooden printing sorts were in use for centuries in combination with metal type. Not shown, and more the concern of the casterman, is the “set”, or width of each sort. Set width, like body size, is measured in points.

In order to extend the working life of type, and to account for the finite sorts in a case of type, copies of forms were cast when anticipating subsequent printings of a text, freeing the costly type for other work. This was particularly prevalent in book and newspaper work where rotary presses required type forms to wrap an impression cylinder rather than set in the bed of a press. In this process, called stereotyping, the entire form is pressed into a fine matrix such as plaster of Paris or papier mâché called a flong to create a positive, from which the stereotype form was electrotyped, cast of type metal.

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