How Are Books Bound? Holding Pages Together for Five Hundred Years
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A book has to open flat enough to read, stay shut when shelved, survive being opened thousands of times, and not tear itself apart at the joint where the covers hinge. Those requirements pull against each other, and every binding method ever devised is a particular compromise between them, with cost being the variable that decides which compromise a given book gets.
The structure of a traditional book
A sewn book is not made of individual pages. Large sheets are printed with several pages to a side, folded into groups called sections or gatherings, and those sections are sewn through the fold, which is the crucial detail: the thread passes through the paper at the strongest point rather than near an edge. The sections are sewn to each other and frequently onto tapes or cords running across the spine, which are then attached to the boards, so the pull of a cover is transferred into the sewing structure rather than into the paper. The spine is rounded and backed, hammered into a slight curve with a shoulder on each side, which makes room for the swell created by the thread and gives the boards something to hinge against. Endpapers attach the block to the boards, a headband is added at top and bottom, and a covering of leather, cloth or paper goes over the boards and spine. Done this way a book opens flat, distributes stress properly and can last centuries.
The methods in use
Commercial binding offers a range of structures whose durability tracks their cost closely:
- •Sewn case binding, the traditional hardback, where the sewn block is made separately from the case and the two are joined by the endpapers, which is why a hardback's cover can be replaced without rebuilding the book
- •Perfect binding, where the folds are milled off, leaving loose leaves whose edges are roughened and glued to the spine, which is cheap, works at any thickness and fails when the glue embrittles, releasing pages
- •Notch or burst binding, a middle option in which slots are cut in the fold and glue is forced through, keeping the fold intact and improving strength considerably over plain perfect binding
- •Saddle stitching, where folded sheets are nested and stapled through the fold, used for thin publications and unsuitable beyond a certain thickness
- •Spiral and comb binding, which open perfectly flat and are used where that matters more than appearance, as in manuals and cookbooks
- •Coptic and other exposed sewing structures, among the oldest known, which open completely flat and leave the sewing visible, now used mainly by hand binders and artists
The materials problem
Books fail through their materials at least as often as through their structure. Paper made with acidic rosin sizing from the mid nineteenth century onwards hydrolyses over decades, turning brown and brittle, and the mass deterioration of library collections printed between roughly 1850 and 1990 has prompted enormous deacidification programmes. Leather bindings suffer red rot, a powdery decay caused by the sulphur dioxide of industrial air reacting with the tannins used in nineteenth-century tanning, which is why so many Victorian leather books crumble while much older vegetable-tanned bindings survive. Adhesives matter greatly: animal glue is flexible and reversible with moisture, which conservators value, while many twentieth-century synthetic adhesives grow brittle and yellow and cannot be removed without damage. Modern hot-melt adhesives have largely been replaced by polyurethane reactive adhesives in better perfect binding, which stay flexible far longer. Iron gall ink, standard for manuscripts for a thousand years, can eat through the paper it is written on, which is a separate and serious conservation problem.
From scroll to codex and back
The codex, meaning a book of folded leaves bound at one edge, replaced the scroll in the Mediterranean world over the first few centuries CE, and the reasons are instructive because they are the same reasons formats change now. A codex holds far more text in a given volume by using both sides of the sheet, it can be opened at any point without unrolling, it can be referenced and cross-referenced, it is easier to carry and to conceal, and it is cheaper. Early Christian communities adopted it early and decisively, which accelerated the shift. Bookbinding then remained recognisably similar for well over a millennium, with the major disruption being industrialisation in the nineteenth century, when cloth case binding done by machine replaced hand-bound leather and made books cheap enough for an ordinary household. Electronic reading has not removed the physical book and has changed what it is for, pushing printed books towards either cheap disposable formats or well-made objects worth owning, which is why binding quality has become a selling point again after a century of being invisible.
The takeaway
A traditional book is built from folded sections sewn through the fold and attached to tapes that carry the covers' pull into the sewing rather than into the paper, with a rounded backed spine giving the boards a hinge. Perfect binding mills the folds off and glues loose leaves, which is cheap and fails as the adhesive embrittles. Books deteriorate through acidic paper, red rot in Victorian leather and iron gall ink eating its own page. The codex replaced the scroll because it held more and could be opened anywhere.