Perfect (Glue) Bindings

Perhaps nothing altered the book industry more than the development of the soft cover perfect bound book. It affected not only the affordability of books by eliminating many production processes of case binding, but opened new doors of cover and graphic design.

What we call perfect binding is simply an adhesive binding where the cover is glued to the spine of the book. Adhesive technology has changed dramatically over the years, evolving from stiff mucilage type glues that cracked and disintegrated to today’s flexible glues the ensure generations of use.

A perfect bound book is generally assembled on a gathering line that drops a signature onto a moving book block traveling toward the binder. If the book has 3 signatures, it will use three gathering “pockets” that will, in order, drop each signature onto the moving line. When books are fully assembled, they are F&Gs for “folded and gathered” signatures.

The spine can be prepared a number of ways to accept the glue. Most common was milling, where the entire book block is turned onto its spine, clamped, and passed over a mill or saw blade that removes 1/8" of the spine, making each sheet of the book exposed for glue where the final fold had been.

To increase page pull strength and allow a book to lay flatter, two newer technologies were developed similar in purpose and procedure. The spines of perfect bound books had traditionally been perforated, one reason being the spine offered less resistance when it was perforated. For burst binding and notch binding, a longer, wider punch or slit is made on the folding machine. Later, when the book is gathered, the mill isn’t used to grind off the spine, and the glue is applied directly to the spine and forced up into the notches or slits.

Most binders also apply a ¼" thin strip of side glue to the first and last pages of the book. It’s a sticky glue that flexes like rubber cement and ties the covers tighter to the book.

Less common today are books for which the signatures are sewn through the spine in a classic manner (generally Smyth sewn) to further improve the book's ability to lay flat and greatly increase its useful life. These books were called “sew-wrap” or “sewn with drawn cover”.

For true lay flat ability in a soft cover book, the most popular methods are Repkover and Otto-bound books. These bindings were perfected in the 1980 and licensed to American binders. They differ be from traditonal perfect binding by gluing the book block to a strip of cloth (muslin), not to the inside of the cover. The cloth overhangs the edges of the book block, and this overhang is glued to the inside covers, leaving the spine free to fully open and lay flat.

repkover and perfect bound books

Repkover is done offline of the binder and favors shortruns in its pricing. Long runs can be Ottobound which is done entirely inline. While there are many manufacturing and material differences in the two processes, they produce very similar books with very similar characteristics.

Neither process is inexpensive, but if the ability to lay perfectly flat is required in a soft cover book, there’s really no better way.