Page counts, creep and the spine

Why the page count is a multiple of four

A book is not printed page by page. Sheets are printed with several pages on each side, folded, and trimmed. Fold one sheet once and you get four pages: two on each side. So every folded job has a page count that is a multiple of four.

Larger presses print 8, 16 or 32 pages per sheet, and a 16-page folded sheet is called a signature or a section. A perfect-bound book is a stack of signatures glued at the spine.

The practical consequences:

• A 62-page manuscript becomes a 64-page book, with two blank pages, or it becomes 60 by cutting content.
• If the press runs 16-page signatures, going from 64 to 68 pages may cost a whole extra signature, not four pages’ worth of paper. Ask what the signature size is before promising a page count.
• Blank pages at the back are normal and are not a mistake. They can carry “Notes” if that suits the book.

Imposition is not your job

Imposition is arranging the pages on the sheet so they come out in order after folding. For a simple saddle-stitched 16-page booklet, page 1 sits beside page 16 on one side of a sheet.

Do not do this yourself. Supply single pages, at trim size, in reading order, with bleed and crop marks. The press imposes for their sheet size, their folding machine and their binding, and a pre-imposed file has to be taken apart again before it can be used.

The only exception is if the printer explicitly asks for printer’s spreads, which small shops occasionally do. Ask; do not assume either way.

Creep, and the booklet that loses its margins

On a saddle-stitched booklet, the inner sheets are wrapped around by the outer ones. Each sheet’s fold sits slightly further out, so the inner pages project further and are trimmed more at the fore-edge.

That shift is creep (or push-out). On a 64-page saddle-stitched booklet on normal paper it can be 3 to 5 mm at the centre spread.

Two consequences:

• Keep important content well inside the fore-edge margin on a thick saddle-stitched job, page numbers especially.
• The press usually compensates by shifting pages inward progressively during imposition. Ask whether they do. If they do, you do nothing. If they do not, you widen the margins.

Creep is why thick booklets are usually perfect-bound instead: beyond about 64 pages of normal stock, saddle stitching stops working well.

Spine width

For a perfect-bound book, the cover is one piece: back cover, spine, front cover. You need the spine width before you can lay out the cover, and it depends on the paper’s bulk, not only its weight.

spine (mm) = (pages ÷ 2) × caliper (mm per sheet)

Caliper depends on the stock. A rough guide: 80 gsm uncoated bond is about 0.10 mm per sheet, 100 gsm art paper about 0.09 mm, and a bulky cream book paper can be 0.15 mm at the same weight, which is why novels are thicker than their page count suggests.

Get the number from the printer, on the actual paper. They will measure it or quote the mill’s figure. A cover laid out to a guessed spine width will have the fold falling in the wrong place, and a fold 2 mm out is visible on every copy.

Allow for the cover’s own thickness and the hinge on a hardback, which the binder will specify.

The binding methods, and what each demands of you

• Saddle stitch: stapled through the fold. Multiples of 4, up to about 64 pages, cheap, lies reasonably flat, subject to creep.
• Perfect binding: glued spine. Multiples of 4 (or of the signature), from about 40 pages, needs 3 to 6 mm extra inner margin, does not lie flat.
• Wire-o and spiral: punched and coiled. Any page count, lies completely flat, needs 8 to 12 mm clear at the binding edge and the holes destroy any artwork crossing it.
• Section sewn / case bound: hardback. Expensive, durable, needs endpapers and a case specification from the binder.

The conversation to have before you start

Four questions, one email:

Binding method? Signature size? Spine caliper for this stock at this page count? Do you compensate for creep during imposition?

Everything in this lesson is in those four answers, and they take a printer under a minute to give.