Mediæval books were usually sewn on double cords or strips of leather, and the headband was often sewn at the same time, as shown at [fig. 32], A. This is an excellent method for very large books with heavy sections, and is specially suitable for large vellum manuscripts, in many of which the sections are very thick. An advantage of this method is, that the twist round the double cord virtually makes a knot at every band, and should a thread at any place break, there is no danger of the rest of the thread coming loose. This is the only mode of sewing by which a thread runs absolutely from end to end of the sections. The headband sewn at the same time, and so tied down in every section, is firmer and stronger than if worked on in the way now usual. In the fifteenth century it was the custom to lace the ends of the headbands into the boards in the same way as the other bands. This method, while giving additional strength at the head and tail, and avoiding the somewhat unfinished look of the cut-off ends of the modern headband, is, on the whole, of doubtful advantage, as it is necessary to cut the “turn in” at the point where strength in the leather is much wanted.
At [fig. 32] is shown in section the three methods of sewing mentioned. A is the old sewing round double bands; with the headbands worked at the same time with the same thread; B is the modern flexible sewing, and C the common sawn-in method.
Books that are very thin or are to be bound in vellum, are best sewn on tapes or vellum slips. The easiest way to set up the sewing-frame for such sewing is to sling a piece of wood through two of the lay cords, and to pin one end of the vellum or tape band round this, pull the other end tight, and secure it with a drawing-pin underneath the frame. The sewing, in the case of such flat bands, would not go round, but only across them. To avoid undue looseness, every three or four threads may be caught up at the back of the band, as shown in [fig. 33].
MATERIALS FOR SEWING
The cord used should be of the best hemp, specially made with only two strands of very long fibres to facilitate fraying out. For very large books where a double cord is to be used, the best water line will be found to answer, care being taken to select that which can be frayed out. If tape is used it should be unbleached, such as the sailmakers use. Thread should also be unbleached, as the unnecessary bleaching of most bookbinder’s sewing-thread seems to cause it to rot in a comparatively short time. Silk of the best quality is better than any thread. The ligature silk, undyed, as used by surgeons, is perhaps the strongest material, and can be had in various thicknesses. It is impossible to pay too great attention to the selection of sewing materials, as the permanency of the binding depends on their durability. The rebinding of valuable books is at best a necessary evil, and anything that makes frequent rebinding necessary, is not only objectionable on account of the cost involved, but because it seriously shortens the life of the book.
Experience is required to judge what thickness of thread to use for any given book. If the sections are very thin, a thin thread must be used, or the “swelling” of the back caused by the additional thickness of the thread in that part will be excessive, and make the book unmanageable in “backing.” On the other hand, if the sections are large, and a too thin thread is used, there will not be enough swelling to make a firm “joint.” Broadly speaking, when there are a great many very thin sections, the thinnest thread may be used; and coarser thread may be used when the sections are thicker, or fewer in number. In the case of large manuscripts on vellum it is best to use very thick silk, or even catgut. Vellum is so tough and durable, that any binding of a vellum book should be made as if it were expected to last for hundreds of years.
In selecting the thickness of cord for a book, some judgment is required. On an old book the bands are best made rather prominent by the use of thick cord, but the exact thickness to be used is a matter for taste and experience to decide.
A very thick band on a small book is clumsy, while a very thin band on the back of a heavy book suggests weakness, and is therefore unsightly.
In bindings of early printed books and manuscripts an appearance of great strength is better than extreme neatness.
When the sewing is completed, the cords are cut off close to the lay cords, and then the keys will be loose enough to be easily removed. The knots remaining on the lay bands are removed, and the keys slung through one of them.