Page:The Art of Bookbinding, Zaehnsdorf, 1890.djvu/209

Rh three drops of oil are sufficient to prevent it, all causes of destruction are thus guarded against. This paste exposed to the air hardens without decomposition. If it is kept in an air-tight pot or jar, it will be always ready, without any other preparation. Books placed in a library should be thoroughly dusted two or three times a year, not only to keep them in all their freshness, but also to prevent any development of insects and to examine for signs of dampness. The interior of a book also asks that care, which unfortunately is neglected very often. After having taken a book from the shelves it should not be opened before ascertaining if the top edge be dusty. If it is a book that has had the edge cut, the dust should be removed with a soft duster, or simply blown off. If it is a book which has uncut edges it should be brushed with rather a hard brush. By this method in opening the volume one need not be afraid that the dirt will enter between the leaves and soil them.

Glue.—The best glue may be known by its paleness, but French glue is now manufactured of inferior quality, made pale by the use of acid, but which on boiling turns almost black. Good glue immersed in water for a day will not dissolve, but swell, while inferior will partly or wholly do so, according to quality.

In preparing glue, a few cakes should be broken into pieces and placed in water for twelve hours, then boiled and turned out into a pan to get cold; when cold, pieces may be cut out and placed in the glue-pot as wanted. This naturally refers to when large quantities are used, but small portions may be boiled in the glue-pot after soaking in water. Glue loses a great deal of its strength by frequent remelting. It should always be used as hot as possible. Rice glue or paste.—By mixing rice flour intimately with