For cloth or half cloth binding a hollow back is frequently glued on. To make the covering material of the back more lasting, a back is made up of strong wrappers or some other tough material, which extends over the back underneath the cover. This backing material must be cut 4 to 5 cm wider than the: width of the back and about 1 cm longer each way than the book. This strip is pared very narrowly along both sides with a sharp knife on the so called paring stone. A second strip the backing of the same material is cut the same length but exactly the width of the back of the book and is glued on to the middle of the wider strip. The overlapping parts at the sides are broken in towards the middle, close by the inner packing, and the crease well pressed down with the folder. These overlapping edges are then turned back again and a rule is laid on the packing parallel with the edge but drawn back to the middle about 2 to 3 mm. according to the thickness of the cover. If the movable flaps are now again laid over towards the centre and narrowly creased near the first fold over the rule, a second parallel fold is obtained which allows the book to open much better. The back in section appears as illustrated in Fig. 55 after the middle part of the packing has undergone the necessary rounding.

Rounding can be done either by rubbing the middle part round with a proper wooden tool in a rounding board having several hollows of various degrees of convexity, or by drawing the back with a rocking motion under a broad folder. Such a made up back must fit perfectly true to the groove and on the back. This is the hollow back. Before fastening it to the book, the latter must have a piece of stout paper pasted over the back; good packing-paper is the best. Newspapers and loose advertisements out of magazines are not at all satisfactory and must not be used. The book is glued and the paper lay on and glued. In doing a large batch the books may be pasted in the press and the paper pasted on.

Many experts glue the hollow backs on and use paste for the board. Very frequently the glue comes through and spoils the end papers. It. is better to raise the flaps of the back, paste the tear off of the end paper, paste the bands on to it and the loose flaps as well, and then paste this on the outside and set the board on it. The latter must be set back a little further in this case so that the book moves freely in the joint. The back, therefore, is a hollow arch stretching over the book from groove to groove, the loose flaps of the packing adhering between book and board. The book is pressed until thoroughly dry best between zinc plates.

For shaping boarded books an edge rule is used. This is a thin iron rule not much longer than the width of the book. On the long edge an iron pin about the width of the edge is soldered. This tool is inserted between book and board so that the iron pin lies close to the edge of the book; if the board is trimmed along this it will leave the board exactly as much larger than the book as is the width of the rule.

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