Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

spring-back

1. A device or technique invented by the Englishmen John and Joseph Williams, in about 1799 and used ever since in the binding of large blankbooks. The spring-back consists of a strip of millboard, or other hard binder's board, the length of the boards of the book and of a width that, when curved, will fit around the spine and onto the sides of the text block at least one fourth of an inch on both sides. The board is first soaked in water and a strip of kraft paper four times its width is then glued around it. The purpose of the paper is to stiffen the board further so that it will maintain its form after it is curved to the proper shape. The assembly is curved around a core (the thickness of the book), or by means of a BACK-MOLDING IRON . A cloth liner is then glued to the interior of the curve, overlapping the edges by inches on either side. These overlaps are glued to the LEVERS . After the spring-back is attached, both ends are softened, paste is applied, and the ends of the spring-back are bent over to form the headcaps.

The purpose of the spring-back is to cause the book to lie flat so as to facilitate its being written in. It acts as a spring, and its pressure on the sides of the book near the spine causes the book to snap open and shut. The levers assist in this snapping effect, which is enhanced by the fact that the machine direction of the lever boards is at right angles to the length of the spine.

2. The degree to which a sheet of paper will assume its original flat condition after being folded and then released. (241 , 264 , 339 , 343 )