KINDS OF LEATHER[3]
The leathers that have been used in binding books have come from all sorts of animals, but so far as the librarian is concerned the skins of four animals only need be taken into consideration—the sheep, the cow, the pig and the goat. In England some experiments have been made with sealskin, but it has not been used long enough to give any definite idea of its resistance to the encroachments of time.
[3] The prices of leathers given in the text are those which prevailed during the summer of 1915.
Sheepskin
Sheepskin is a soft, flexible leather with weak fibres, and with a surface easily abraded. It has been used for bindings practically ever since books were put into leathers; and, under the old methods of tanning and manufacturing, proved satisfactory. In many libraries it is possible to see leather books bound in sheep in the 17th century which are in a good state of preservation. Even the sheep of the beginning of the 19th century is frequently well preserved. Since 1860, however, the quality of sheep has greatly deteriorated. This is bad enough, but unfortunately sheep likes to masquerade under the name of morocco and other leathers of a better grade, so that its use is much more extensive than appears at first sight. In the process of imitation the grain of the leather imitated is stamped on the skin. When this is done it generally takes an expert to detect the fact that the leather is not what it pretends to be, and even experts are sometimes deceived after the leather is on a book.
The strongest sheepskins are made when tanned with oak bark. Sumac, which is such a valuable tanning material with other leathers, is here inferior to oak.
There are two kinds of sheepskin, the wool sheep which is known to all, and the hair sheep which is not found in the United States, and which in reality is a cross between a sheep and a goat. The hair sheep comes from India, China, South America and Africa, generally from mountainous districts. It has a much tougher fibre and is a better wearing skin than that of the wool sheep. Unfortunately most of these skins, which are all imported, are made into shoe leather. When properly tanned they are very suitable for library binding, and their use for that purpose is increasing.
The wool sheepskin in its natural color has been used for many years for binding law books. It is seldom used for anything except government documents and law books, and for this reason is known as "law-sheep."
Roan. Roans, the term used for sheepskins after they are dyed, can be used advantageously on books which will be handled a great deal, and which in any event will not stay on the shelves indefinitely. Properly tanned and dyed, they make a satisfactory leather for a time, but their life under the best of conditions seldom exceeds ten or twelve years. While this is true of good roans, it unfortunately remains true that in the United States, at least, it is difficult to get roans that are properly tanned and dyed. Therefore, unless one is sure that the quality of the skin is the best, he should use no sheep under any conditions.
Skiver. Skiver is the outside of a sheepskin which has been split, the inner side being known as the flesher. It is a leather much used for commercial binding, but since the splitting process takes away a great part of the strength of the skin, leaving it not much stronger than strong paper, skiver is wholly unfitted for library use.