Unsewn Binding

the joining together of signatures or individual leaves of a pamphlet or book without sewing with thread or wire.

Unsewn bindings include mechanical and perfect bindings. Mechanical binding entails the use of metal or plastic clasps, pins, springs, or rings. It is a laborious operation and has substantial drawbacks, for example, complexity of design, increased spine areas, and unwieldy opening. As a result, mechanical binding is only used for the production of albums, prospectuses, catalogs, and similar types of publications. The binding does, however, make possible the replacement of individual pages with others.

Perfect binding has been known for a long time; the first patent was obtained in Austria in 1811. Its use became widespread in the 1950’s, when special synthetic adhesives were developed. Perfect binding is employed quite extensively: in 1974, more than 50 percent of all books and magazines published in the USA, Japan, and Great Britain had perfect bindings. Perfect binding has several advantages over all other binding methods. It imparts uniform strength, and the binding operation does not depend on the size of a unit. The production cycle is short, and there is a comparatively small expenditure of labor. Automation also is possible. Perfect binding involves the application of a layer of the adhesive to the spine and the production of an elastic film that holds the connected parts securely together. Most often used is an aqueous dispersion of polyvinyl acetate, to which are added a plasticizer (dibutyl phthalate), alcoholic solutions of polyamide resins, and thermoplastic adhesives that make it possible to minimize the drying time of the units after gluing.

There are several well-known methods of perfect binding, each differing in the preliminary treatment of the spine. The most highly developed and common method involves completely cutting off the spine folds, roughening the cut surface, and applying an adhesive solution or a melted adhesive to the spine. Almost all the equipment produced in Switzerland, the USA, the USSR, Japan, and Great Britain operates according to this technology. The binding machinery (line, rotary, or conveyor types) performs a set of operations, starting with the gathering of signatures and ending with the application of a cover to the pamphlet. The productivity ranges from 3,000 to 8,000 units per hour.

Sometimes the method of “single-fold sections” is used: an adhesive layer is applied to the spine of a unit composed of printed sheets folded in two (the binding of maps in geographical atlases). Another method, which was developed in the German Democratic Republic, involves sewing the sheets in each signature with thermoplastic thread when the signatures are being folded. The unit made up of such signatures is glued and subsequently backed with some sort of material.