The Art of Bookbinding/Chapter 11
The word "rounding" applies to the back of the book, and is preliminary to backing. In rounding the back, the book is to be laid on the press before the workman with the foredge towards him; the book is then to be held with the left hand by placing the thumb on the foredge and fingers on the top of the book pointing towards the back, so that by drawing the fingers towards the thumb, or by pressing fingers and thumb together, the back is drawn towards the workman at an angle. In this position the back is struck with the face of the hammer, beginning in the centre, still drawing the back over with the left hand. The book is then to be turned over, and the other side treated in the same way, and continually changed or turned from one side to the other until it has its proper form, which should be a part of a circle. When sufficiently rounded, it should be examined to see if one side be perfectly level with the other, by holding the book up and glancing down its back, and gently tapping the places where uneven, until it is perfectly true or uniform.
The thicker the book the more difficult it will be found to round it; and some papers will be found more obstinate than others, so that great care must be exercised both in rounding and backing, as the foredge when cut will have exactly the same form as the back. Nothing can be more annoying than to see books lop-sided, pig-backed, and with sundry other ailments, inherent to cheap bookbinding.
The back when properly rounded should be about a third of a circle, according to the present mode, but in olden times they were made almost flat. They were not rounded as now done, but the swelling caused by the thread used made quite enough rounding when put in the press for backing.
Flat back books have a certain charm about them, the more so if in other respects they are properly forwarded. The theory is altogether averse to practical binding. I have always been given to understand that we round our books in order to counteract the tendency of a book to sink in and assume a convex back. Any old well-used book bound with a flat back will show at once this defect.
Messrs. Hopkinson and Cope, of Farringdon Road, London, manufacture a rounding machine. They claim that this machine will round 600 books per hour, and that any desired "round" may be given to the book with great uniformity.