A book that is to be "sawn in" is marked up us for flexible work, but the; back is sawn, both Tor the bauds and "kettle - stitch," with a tenon saw, having the teeth not spread out too ' much, and of suitable width of cutting face. The cut must not enter too deeply, and must in all cases be guided by the thickness of cord to be used. The size of the book determines the thickness of the cord; suitable kinds can be purchased, being known by the size of the book, as 8vo, 4to, etc. Loose cording causes great inconvenience, and necessitates putting a lot of glue into the grooves to keep the cord in place. On the other hand, if the saw-cuts are not deep enough, the cord will stand out from the back, and be seen when the book is finished, if not remedied by extra pieces of paper between the bands when lining up. Double thin cord is better than single thick for large books, because thin cords will imbed themselves in the back, whereas a large one will not, unless very deep and wide saw cuts be made.
Largo folios should be sawn on 6 or 7 bands, but 5 is the right number for an 8vo, from which all other sizes Can be regulated.
The "sewing press," Fig. 182, consists of a bed a, 2 screws b, and a "beam" or cross bare, round which are fastened 5 or more "lay cords " d; 5 pieces of cord cut from the ball, in length measuring about 4 times the thickness of the book, are fastened to the lay cords by slip knots, the other ends being fastened to small pieces of metal called "keys" e, by twisting the ends round twice and then making a "half hitch."
The keys are passed through the slot f in the bed of the "press," and the beam is screwed up loose enough to allow the lay cords to move freely backwards or forwards. The book being on the bed of the press, with the back towards the sewer, a few sheets are laid against the cords, and exactly to the marks made on the back of the sections; when quite true and perpendicular, they are tightened by screwing the beam up. If the cords are a little to the right, the sewer can get his left arm to rest better on the press.
Fig. 183 represents the course of the thread in sewing the sheet to the bands; a being the back of the boos, 6 the thread, and c the cord, an arrow indicating the direction of the thread.
The first and last sections are strengthened by overcasting with cotton. The first sheet is laid against the bands, and the needle is introduced through the kettle-stitch hole on the right (head) of the book; the left hand being inside the centre of the sheet, the needle is taken with it, and thrust out on the left of the mark made for the first band; the needle is taken in the right hand, and again introduced on the right of the same band, thus making a complete circle round the band. This is repeated with each succeeding band, and the needle is finally brought out of the kettle-stitch hole on the left (tail) of the sheet. Another sheet is placed on the top, and similarly treated, by introducing the needle at the left end (tail); and when taken out at the right end (top), the thread is fastened by a knot to the end, hanging from the first sheet, which is left long enough for that purpose. As a thread is used out, another is joined to it, making it continuous; the knots must be made very neatly, and the ends cut off. A third sheet having been sewn like the others, the needle is brought out at the kettle-stitch, thrust between the two sheets first sewn, and drawn round the thread, thus securing each sheet to its neighbour by a kind of chain stitch.
This is the strongest way of sewing, and takes 3 or 4 times as long as ordinary sewing. The thread must be drawn tight each time it passes round the band, and finally properly fastened off at the kettle-stitch, or the sections will work loose in time. The cord for flexible work is called "flexible"; it is twisted tighter and is stronger than any other, Marshall's being the best. The thickness of the cord must be proportioned to the size and thickness of the book, and will partly depend on whether the sheets are halves or wholes. Too thick a thread will make the "swelling" (the rising caused in the back by the thread) too much, and prevent a proper rounding and a right sized "groove" in backing. With thick or few sections, a thick thread must be used to produce a good groove.
In a book of moderate thickness, the sections may be knocked down by occasionally tapping them with a piece of wood loaded at one end with lead, or with a thick folding-stick. In the kettle - stitch, the thread must not be drawn too tight in making the chain, or the thread will break in backing; nor left too slack, or the sheets will wear loose. The last sheet should be fastened with a double knot round the kettle-stitch, 2 or 3 sections down, and that section must be sewn all along.
Ordinary sewing differs in that the thread is not twisted round the cord. The cord fits into the saw cuts; the thread is passed over the cord, not round it, and then along the section, out of the holes made, and into them again, the kettle-stitch being made in the same way. In this style, the back of the book can be better gilt: in flexible work, the leather is pasted to the back, and is bent each time the book is opened, incurring a risk of the gold breaking away from the leather in wear. Books sewn in the ordinary method are made with a hollow back, and when the book is opened, the crease in the back is independent of the leather covering, so that the lining of the back only is creased, and the leather keeps its form because the lining gives it a spring outwards. Morocco leather is always used for flexible work. Ordinary sewing is adapted for books that do not require great strength, such as library bindings; but a book for constant reference or daily use should be sewn flexibly.