The breaks between signatures are repaired and the old glue at these points softened by means of bookbinders’ paste. For this, a solid, satisfactory and fairly elastic substitute can be made by mixing about equal parts of good liquid glue and ordinary white library paste of the kind which comes in tubes. With a long pin, slightly bent on the point, this mixture is laid in the open crack between the signatures, care being taken to distribute it evenly the whole length of the book and to thoroughly cover the exposed inside of the back lining. An excess of paste must be avoided, as it would spread out on the inside margins of the leaves when the book is closed to dry. When all the broken places are mended, the book is closed and placed under a slight pressure for a few hours.
Where the book is bound with a “spring back,” that is to say, with a back which springs apart when the book is opened, leaving a space between the outside back and the actual back of the signatures where they are stitched, a further strengthening of the back may be desirable. This strengthening can be obtained by “lining up” the inside back with a new strip of paper.
To do this, cut a strip of medium weight Japan vellum—which is the best paper for the purpose—a few inches more than twice the height of the book and in width equal to the inside back. One end of this, with the corners clipped so it will not catch, is inserted between the outside and inside backs of the book and slipped through until it projects about an inch at the bottom of the book. (Fig. A.) The part of the strip left exposed at the top is then well coated on the inside face with the paste mentioned above and pulled into the book, against the inside back or lining, by means of the end projecting at the bottom. The surplus of the strip at top and bottom is then cut off, two short slips of paper temporarily inserted at top and bottom to prevent the new lining adhering to the outside back, and a firm hand pressure applied all over the back to force the new lining into close union with the old on the backs of the signatures. The book is then set aside to dry, under a light pressure, after which the two slips of paper inserted at top and bottom are pulled out.
Any slight necessary exterior repairs should then be made—loose bits of cloth or paper at worn corners or along the edges of the boards pasted down, and any tears at the top of back above the head-band reenforced from the inside with strips of cloth or paper.
The outside of a soiled cloth binding often may be cleaned by means of a soft pencil-eraser. If this is done, the cloth should afterward be freshened by a thin coat of sizing.
If these operations are carefully and thoroughly carried out, the book should then be in a solid and satisfactory condition and capable of standing any reasonable amount of wear.