nty-four hours
often suffices to brighten and clear it; but if, after a long soaking, it
still remains darkened to the point of detracting from the clarity of the
engraving, one will need to use chemicals in order to obtain a suitable
bleaching. Chloride of lime may be used for this purpose. This is a fine,
dry powder which softens when allowed to absorb moisture from the
atmosphere. About fifty grammes of this are placed in a bottle about
two-thirds full of water, and thoroughly shaken. When the solution clears
by the excess of matter depositing on the bottom of the bottle, the clear
liquid is carefully poured off. Another solution, which will be weaker,
may be made by pouring more water into the bottle. The clear solution is
diluted with about twenty times its quantity of pure water, for use. It is
better to dilute too much, and add more of the solution later, if
necessary, than to dilute too little. The solution will not injure the
black ink of an impression, but if too concentrated, it will make the
paper brittle.

After using this solution, the print should be placed in a bath of weak
acid, and then left to soak for several hours in clear water.

CHAPTER III

_REBACKING_

[Illustration: ORIGINAL SHEEP BINDING

(1684 REBACKED)]

It often happens that books are purchased in old sheep, calf, or even
morocco bindings with the hinges so broken that the boards are either
entirely off or held only by weakened cords. Such books may be properly
entrusted to a good binder for rebinding in substantial leather. It is
sometimes preferable, however, merely to reback such books, not only in
order to preserve the old leather sides, which are generally in much
better condition than the back and often possessed of a very attractive
patina, but also to save the wear and slight trimming to which the book
would necessarily be subject in rebinding.

It is inadvisable to reback with calf or any very perishable leather. A
good quality morocco should be used. In rebacking books bound in old calf
or sheep, a smooth-grain brown morocco, such as that known to the trade as
Spanish morocco, will be found satisfactory and a fair match for the old
leather, both in color and surface texture.

The first operation in rebacking is to treat the old leather with a
softening substance, such as vaseline, to prevent the old leather from
breaking while it is being worked on. The vaseline should be rubbed well
into the covers, left on for