William Morris, when he founded the Kelmscott Press, did more than revive fine book-printing; he established a tradition for books that were eminently bindable, and the presses that followed his lead kept up the tradition; so that we have in England a large number of beautifully printed books that are worthy of the best binding, and that impose no unnecessary difficulties on the binder.
Mr. Cobden-Sanderson did much to revive the use of the tight or flexible back. In this style the leather is attached directly to the back of the sections, and so helps to hold them firmly together. All leather-bound books had tight backs until about a hundred years ago, when the hollow back came into general use. A tight back should throw up when the book is opened; that is to say the back, convex when the book is shut, should become concave on the book being opened. This causes a certain amount of creasing in the leather, and this creasing is not good for gold tooling; but with a well-bound book the damage is not serious, and important constructional features must not be sacrificed for the sake of the decoration.
The hollow back does not crease the leather, and so is preferred by finishers, and besides it is easier to cover a hollow back neatly than a tight one; but the strain of opening and shutting, which should be distributed evenly across the back, is in the hollow back thrown on the joints, with the result that the leather is apt to break at these places unless specially strengthened, as is the case with well-bound account books.
While "flexible" backs that are truly flexible are undoubtedly the best, some binders line up their backs so stiffly under the leather as to allow little or no movement when the book is opened. This avoids the creasing of the leather and leaves the decoration uninjured, but the book will not open freely, and there is no virtue in such a tight back. Leather is chosen for binding because of its toughness and flexibility, yet binders deliberately sacrifice this last quality in order to obtain extreme neatness or to hide faults in the forwarding.
It is the fashion in some quarters to admire as the perfection of craftsmanship an exact and hard square edge to the boards of a book. This can only be got by paring the leather down till it is as thin as paper and has consequently very little strength. A softer, rounder edge is natural to a leather-covered article, and it is unreasonable to expect the qualities of a newly planed board in a material so wholly different in character. The edges of the leather-covered board should have a distinctly flat face, and clumsiness will be avoided by any good craftsman. It is only the extreme sharpness, so much admired by unknowing people, that is objectionable.