The Art of Bookbinding/Chapter 10
The book mast now be glued up; that is, glue must be applied to the back to hold the sections together, and make the back firm during the rounding and backing. Knock the book perfectly true at its back and head, and put it into the lying press between two pieces of old mill-board; expose the back and let it project from the boards a little, the object being to hold the book firm and to keep the slips close to the sides, so that no glue shall get on them; then with glue, not too thick, but hot, glue the back, rubbing it in with the brush, and take the overplus off again with the brush. In some shops, a handful of shavings is used to rub the glue in, and to take the refuse away, but I consider this to be a bad plan, as a great quantity of glue is wasted.
The Germans rub the glue into the back with the back of a hammer, and take away the overplus with the brush; this is certainly better than using shavings. The back must not be allowed to get too dry before it is rounded, or it will have to be damped with a sponge, to give to the glue the elasticity required, but it should not be wet, this being worse than letting it get too dry. The book should be left for about an hour, or till it no longer feels tacky to the touch, but still retains its flexibility. A flexible bound book should first be rounded, a backing board being used to bring the sheets round instead of a hammer, then the back glued, and a piece of tape tied round the book to prevent its going back flat.
But all books are not glued up in the press; some workmen knock up a number of books, and, allowing them to project a little over their press, glue the lot up at once; others again, by holding the book in the left hand and drawing the brush up and down the back. These last methods are, however, only practised in cloth shops, where books are bound or cased at very low prices. The proper way, as I have explained, is to put the book in the lying press. The book is then laid on its side to dry, and if more than one, they should be laid alternately back and foredge, with the back projecting about half an inch, and allowed to dry spontanenusly, and on no account to be dried by the heat of a fire. All artificial heat in drying in any process of bookbinding is injurious to the work.