Antiquarian book formats

Format in which the printed sheet is used whole, without folding, forming a single leaf, that is, two pages. This format, rare for books, is found notably in posters, maps, or very large printed documents.

A format obtained by folding a printed sheet once, forming two leaves, or four pages. Often of large dimensions, the folio was particularly used for monumental, scholarly, liturgical or richly illustrated works.

Format obtained when a printed sheet is folded into four leaves, or eight pages. Generally larger than the octavo, the quarto was frequently used for scholarly, illustrated, or presentation works.

A format in which one printed sheet is folded to form eight leaves, or sixteen pages. Very common throughout the history of the book, the octavo generally corresponds to a volume of intermediate, easily handled dimensions.

Format in which a printed sheet is folded and arranged to form twelve leaves, or twenty-four pages. Widely used from the 17th to the 19th century, it was particularly favoured for works of a convenient, handy size.

Format obtained when a printed sheet is folded to form sixteen leaves, or thirty-two pages. Generally of small dimensions, the sextodecimo (or sixteenmo) was notably used for portable works and small-format editions.

The octodecimo (in-18) emerged in the eighteenth century but reigned supreme over the nineteenth: it is the format of Charpentier's small novels, of the one-franc "libraries", and of the first editions of Balzac, Flaubert and Baudelaire published by Poulet-Malassis. Its sheet, folded into eighteen leaves, yields gatherings of thirty-six pages; the height of copies ranges between 17 and 19 centimetres.

For the collector of French literature, the octodecimo is the format par excellence of the modern first edition: it was in this modest, paperback form that most of the century's major texts first appeared. An untrimmed copy retains its margins and deckle edges; a copy in a contemporary binding is judged on the preservation of its wrappers. The format should not be confused with the duodecimo, slightly taller, nor with the sextodecimo, more squat: it is the number of leaves in the gathering that is decisive.

The 24mo is among the smallest formats of the early printed book: the sheet is folded into twenty-four leaves, and the gathering comprises forty-eight pages. Copies rarely measure more than thirteen centimetres. This format suited texts meant to be carried on one's person — books of hours, small classics, almanacs — and eighteenth-century publishers, Cazin foremost among them, issued entire series in it, bound in calf or morocco with small-tool decoration.

The bibliographer recognises it by the smallness of the page combined with the imposition: the gatherings are sometimes made up of two half-sheets, as the signatures reveal. It is distinguished from the 32mo, smaller still, and from the 16mo, which is taller. The 'Cazins', highly sought after, are judged on the freshness of their contemporary binding and on the presence of all their gatherings, which so diminutive a format makes easy to lose.

The duodecimo-trigesimo, or thirty-two-mo, is the last of the common formats: the sheet is folded five times, and each gathering comprises thirty-two leaves, that is sixty-four pages some ten centimetres high. Lyons and Parisian printers of the sixteenth century already employed it for books of hours and Latin classics; nineteenth-century publishers made it the format of choice for 'jewel' books and microscopic editions whose printing amounted to a feat of virtuosity.

An early thirty-two-mo is judged above all on its condition: pages so small crease, tear and go missing, and a complete copy, in its contemporary binding, is rarer than it might appear. The format is sometimes confused with the twenty-four-mo or with the still smaller sixty-four-mo; only a reading of the signatures and a count of the leaves per gathering allow it to be identified without error. In our notices, the dimensions in millimetres always complete the description.