Folio (printing) - Format

Format

A folio (from Latin foliō, abl. of folium, leaf ) is a book or pamphlet made up of one or more full sheets of paper, on each sheet of which four pages of text are printed, two on each side; each sheet is then folded one time to produce two leaves. Each leaf of a folio book thus is one half the size of the original sheet. This contrasts with a quarto, folding each sheet twice, and octavo, folding each sheet three times. Unlike the folio, these last, and further types involving more folds, require the pages of the book to be cut open after binding, which might be done mechanically by the printer, but in historic books was often left for the reader to do with a paper-knife.

There are variations in how folios are produced. For example, bibliographers call a book printed as a folio (two leaves per full sheet), but bound in gatherings of 8 leaves each, a "folio in 8s."

The Gutenberg Bible was printed in about 1455 as a folio, in which four pages of text were printed on each sheet of paper, which were then folded once. The page size is 12 x 17.5 inches (307 x 445 mm), a "double folio" size. Several such folded conjugate pairs of leaves were inserted inside one another to produce the sections or gatherings, which were then sewn together to form the final book. Shakespeare's First Folio edition is printed as a folio and has a page height of 12.5 inches (320 mm), making it a rather small folio size.

Folios were a common format of books printed in the incunabula period (books printed before 1501), although the earliest printed book, surviving only as a fragment of a leaf, is a quarto. The British Library Incunabula Short Title Catalogue currently lists about 28,100 different editions of surviving books, pamphlets and broadsides (some fragmentary only) printed before 1501, of which about 8,600 are folios, representing just over 30 percent of all works in the catalogue.