twenty-fours

A twenty-four is a folded sheet of paper that yields 48 printed pages, 24 on each side. In letterpress and offset printing, it represents a single printing unit, or signature, that comes off the press ready for folding and collation into a bound book. The term comes from its historical construction: a single large sheet of paper printed on both sides and folded multiple times to create 24 leaves (48 pages total).

The term is measured in leaves rather than pages because printers historically thought in terms of the physical stock they handled. A twenty-four contains exactly 24 leaves when folded; each leaf has two sides, giving 48 pageable surfaces. This is larger than the more common sixteen-page signature (or sixteen) but smaller than the thirty-two-page signature (or thirty-two). The format depends on the parent sheet size, the number of folds, and the desired final page dimensions.

Imposition and Press Work

Before a twenty-four reaches the folder, the compositor or paste-up artist must impose the pages in the correct order on the printing plate. Pages do not appear in sequential order on the plate; instead, they are positioned so that when the sheet folds, pages 1 through 48 align properly. This imposition is critical: an error means 48 pages of scrap per sheet printed. With large press runs, even a single botched signature can waste thousands of dollars in paper and ink.

Twenty-fours were especially common in book and journal printing where consistent page counts made binding efficient. The signature size determined the rhythm of the entire production schedule: each signature had to be printed, dried, folded, and stacked before the next run began. In modern offset printing, twenty-fours appear less frequently than sixteens or thirty-twos, largely because smaller signatures reduce the risk of press setup errors and allow faster job changeovers on smaller presses.

The physical properties of the stock matter greatly. A twenty-four made from lightweight book paper (say 40 lb. text) folds and collates smoothly; the same signature in heavier cover stock may not fold cleanly or may resist binding. Grain direction of the paper also affects folding quality. For this reason, the printer and paper supplier must coordinate on stock choice before the job is imposed and plated.