It is a well-known fact that the leather of bindings that are much handled lasts very much better than that on books which remain untouched on the shelves. There is little doubt that the reason for this is that the slight amount of grease the leather receives from the hands nourishes it and keeps it flexible. A coating of glair or varnish is found to some extent to protect leather from adverse outside influences, but, unfortunately, both glair and varnish tend rather to harden leather than to keep it flexible, and they fail just where failure is most serious, that is at the joints. In opening and shutting, any coat of glair or varnish that has become hard will crack, and expose the leather of the joint and back. Flexibility is an essential quality in bookbinding leather, for as soon as the leather at the joint of a binding becomes stiff it breaks away when the boards are opened.
It would add immensely to the life of old leather bindings if librarians would have them treated, say once a year, with some preservative. The consequent expense would be saved many times over by the reduction of the cost of rebinding. Such a preservative must not stain, must not evaporate, must not become hard, and must not be sticky. Vaseline has been recommended, and answers fairly well, but will evaporate, although slowly. I have found that a solution of paraffin wax in castor oil answers well. It is cheap and very simple to prepare. To prepare it, some castor oil is put into an earthenware jar, and about half its weight of paraffin wax shredded into it. On warming, the wax will melt, and the preparation is ready for use.
A little of the preparation is well worked into a piece of flannel, and the books rubbed with it, special attention being paid to the back and joints. They may be further rubbed with the hand, and finally gone over with a clean, soft cloth. Very little of the preparation need be used on each book.
If bindings have projecting metal corners or clasps that are likely to scratch the neighbouring books, pieces of mill-board, which may be lined with leather or good paper, should be placed next them, or they may have a cover made of a piece of mill-board bent round as shown at [fig. 120], and strengthened at the folds with linen. This may be slipped into the shelf with the book with the open end outwards, and will then hardly be seen.
Fig. 120.
Bindings which have previously had metal clasps, &c., often have projecting fragments of the old nails. These should be sought for and carefully removed or driven in, as they may seriously damage any bindings with which they come in contact.
To protect valuable old bindings, cases may be made and lettered on the back with the title of the book.
Loose covers that necessitate the bending back of the boards for their removal are not recommended.