erial, and can be had in various thicknesses. It is
impossible to pay too great attention to the selection of sewing
materials, as the permanency of the binding depends on their
durability. The rebinding of valuable books is at best a necessary
evil, and anything that makes frequent rebinding necessary, is not
only objectionable on account of the cost involved, but because it
seriously shortens the life of the book.

Experience is required to judge what thickness of thread to use for
any given book. If the sections are very thin, a thin thread must be
used, or the "swelling" of the back caused by the additional thickness
of the thread in that part will be excessive, and make the book
unmanageable in "backing." On the other hand, if the sections are
large, and a too thin thread is used, there will not be enough
swelling to make a firm "joint." Broadly speaking, when there are a
great many very thin sections, the thinnest thread may be used; and
coarser thread may be used when the sections are thicker, or fewer in
number. In the case of large manuscripts on vellum it is best to use
very thick silk, or even catgut. Vellum is so tough and durable, that
any binding of a vellum book should be made as if it were expected to
last for hundreds of years.

In selecting the thickness of cord for a book, some judgment is
required. On an old book the bands are best made rather prominent by
the use of thick cord, but the exact thickness to be used is a matter
for taste and experience to decide.

A very thick band on a small book is clumsy, while a very thin band on
the back of a heavy book suggests weakness, and is therefore
unsightly.

In bindings of early printed books and manuscripts an appearance of
great strength is better than extreme neatness.

When the sewing is completed, the cords are cut off close to the lay
cords, and then the keys will be loose enough to be easily removed.
The knots remaining on the lay bands are removed, and the keys slung
through one of them.

CHAPTER VIII

Fraying out Slips--Glueing up--Rounding and Backing

FRAYING OUT SLIPS AND GLUEING UP

After sewing, the book should be looked through to see that all sheets
and plates have been caught by the thread, and special attention
should be given to end papers to see that the sewing lies evenly.

The ends of the cords should next be cut off to within about two
inches of the book o