Pigskin is one of the strongest leathers, having a hard, resisting surface and a good, tough fibre. In the grain, the holes which were left when bristles were removed are plainly visible, giving the leather a distinctive appearance, which can be imitated successfully, but which is much less often imitated than the grain of morocco. If there be doubt of the genuineness of pig, soak a piece of the leather until it has absorbed a quant.i.ty of water, and then stretch it. If the grain pulls out, it is imitation; if genuine, the bristle holes still show plainly.

Oak bark tanning is the best for this leather, and, since it is more nearly gristle (less fibrous) than other leathers, dyes and chemicals should not be used which will interfere with its quality of resisting friction. It should be used in its natural color whenever possible.

Pigskin frequently comes in skins which are too thick for the binder to work easily, or which are very uneven in thickness. In such cases the paring down of the skin is likely to injure its strength. Because of its thickness pig is generally supposed to be more suitable for large than for small books, but inasmuch as several binders have used it successfully for years on small books, it may be taken for granted that it can be used with good results on all books, large or small, which are to receive hard usage. It needs constant handling, and the absorption of a certain amount of oil from the hands to keep it pliable. Otherwise it dries rapidly and cracks along the joint. This, however, is true of all leathers to a greater or less extent. Pig costs from 40c. to 45c. a square foot.

GOAT

The leather which makes the strongest and most attractive binding comes from the skins of goats and is called morocco, because it originally came from that country. In the course of time goat skins from other countries were tanned with sumac (originally a distinguishing characteristic of a genuine morocco), but the same name was applied so that we now have the paradoxical terms, Turkey morocco, Levant morocco, etc. Moroccos have a beautiful grain, are flexible, soft and pliable to the hand, and resist hard wear; qualities which contribute to their great popularity.

Morocco varies greatly in quality as well as in appearance.

Unfortunately the skins which are best in quality, considering the length of time they will wear, are not always those best in appearance.

The skins of goats with long hair from the colder countries make beautiful bindings; but the skins of goats from the hot countries, such as the interior of Africa, having short hair, while not so attractive in appearance, are tougher and wear longer. In addition to the many grades of genuine morocco there are as many more imitations of it made from sheepskin, cowhide, etc. Only the expert can detect some of them in the skin, and even he may be deceived when the leather is on the back of the book.

In general it should be said that genuine morocco is the most expensive leather that a library can use, and that it can be used to the greatest advantage only occasionally. It makes an excellent binding for large reference books which are constantly handled, for art books which must be attractively bound, and for some periodicals which are much used in reference work. It is not used nearly so much in libraries to-day as it was ten or fifteen years ago, and it is quite safe to say that it will be used less ten years from to-day than it is now.

_Levant morocco_, made from the skins of Angora goats, is the most expensive and most beautiful leather used in binding. It has a large, prominent grain, but is far too expensive for any library to use, especially when it must be conceded that in its wearing quality it does not equal that of some less expensive moroccos. Mr. Chivers' test showed that so far as tensile strength goes, this leather is very much weaker than many leathers much less expensive. When the skin has been subjected to pressure until the surface is smooth it is known as "crushed levant."

_Turkey morocco_, made of skins of goats from Turkey, is a very strong, durable leather which all libraries will find occasion to use from time to time. It is very easily imitated. Under exposure to atmospheric conditions existing in many libraries its life may not extend beyond thirty years. In one library at least, where conditions of light and heat were poor, the best Turkey morocco that the market afforded showed signs of disintegration within twelve years. Good Turkey morocco can be obtained for 35c. a square foot.

_Persian morocco_, which comes from the skin of a Persian sheep (not goat), is not particularly attractive in appearance and is very poor in quality. It is used extensively for commercial work, but is absolutely valueless for library binding.

_Niger morocco_ is a goat skin which comes from the interior of Africa, generally by way of Tripoli, and is by no means a recent discovery, though we knew little about it five years ago. It is tanned by natives according to some method of vegetable tanning not completely known at this time. While in appearance it is not so attractive as some other moroccos, because of blemishes due to carelessness in handling and to the imperfect removal of some of the hairs, it has been proved by the tests made under the direction of Mr. Chivers to be stronger than all other moroccos; the inference is that it is more durable. Until recently it has been very hard to obtain in the United States.

_Bock morocco_ is not a morocco but a split Persian sheep so poor in quality that it is mentioned only to be condemned.

CALFSKIN

Calfskin in all its various characters, such as divinity, kip, marbled, mottled, smooth, tree, or just plain calf is a very beautiful leather much used in the past for binding books for individuals. For this purpose it has, of late years, been crowded out by Levant morocco. It has a soft, smooth surface which disintegrates rapidly under the action of heat and gas and has little strength even for temporary use. For the library it is useless.

RUSSIA LEATHER

This is a brownish-red leather made from the skins of different animals, tanned with willow bark and filled with a preparation of birch oil which gives it its peculiar odor. Neither in its genuine form nor in imitation is it a useful leather for libraries.

SEALSKIN

Although experiments have been made with it in some English libraries sealskin has never been much used in the United States for library binding. It is made from the skins of the hair seal, the supply coming from all parts of the North Atlantic Ocean. According to Mr. Douglas c.o.c.kerell and other binding experts in England, the skin is peculiarly suited for library use. It is reported to be a hard-wearing leather, tough and pliable, even in quality so that no part of the skin must be discarded because too thin or too weak, and possessing a beautiful grain. The price ranges from a point somewhat higher than that of the poorer moroccos to one somewhat lower than the higher prices.

Unfortunately it can be easily imitated.

VELLUM

Probably no discussion of leather is complete without mentioning vellum, a binding material which does not resemble leather, but which nevertheless is made from calfskin or sometimes from goat skin. It is prepared by the use of lime, and as far as the actual wear on flat surface is concerned, is perhaps better than any leather. It is, however, very susceptible to moisture, which makes it warp; and to light, which makes it hard and brittle. Since it is very hard, does not bend easily and is hard to work, its chief use is on the corners of books to protect them and make them less likely to break or rub. Large libraries have used it somewhat for this purpose, but the use is dying out.

In making a study of leathers it is well to obtain samples of all kinds, including those which are unsuitable for library use, and to examine them carefully, noting the appearance of the grain, thickness of skin, flexibility, and softness of surface. Perhaps more money can be wasted through ignorance of the comparative values of different kinds of leather which it is permissible to use in library binding, than in mismanagement of any other part of binding.

CLOTH

Cloth is fully as important as leather in the economy of binding.

Several years ago it was the custom to bind periodicals and other books which were used comparatively seldom in leather, while fiction, juvenile and other books which wore out quickly were bound in cloth.

Recently the opposite course has been more favored. Books which receive unusually hard usage and are in the hands of readers constantly are bound in leather; while those which are used seldom, including periodicals, are bound in some kind of cloth. Without doubt the change is a wise one. Even the best of leather disintegrates in time under the action of heat, gas, light, etc., and to-day many a volume bound in leather ten or fifteen years ago has parted from its sides, necessitating rebinding or recovering. Had it been bound in a good quality of cloth it would to-day be in good condition, and probably would remain in good condition for a hundred years. It requires considerable courage to change the binding of a good set of a standard periodical, such as the Atlantic or Harper's, from an attractive half morocco binding to an unattractive buckram. Unquestionably, if economy is an object, the change should be made, except possibly in the case of a library which uses these periodicals daily. Every librarian must decide each case for himself strictly according to the use the set is to receive, always bearing in mind the fact that leather disintegrates with time, whereas cloth does not unless exposed to excessive moisture.

No cloth which is suitable for library use is perfectly satisfactory because it has not the strength of good leather, cannot be used advantageously on very heavy books, soils easily and with use grows soft and flabby, especially along the joints. But on the other hand even those not suitable for libraries which are used by the publisher on cheap books are much better than poor grades of leathers, such as skiver, bock, buffing, etc.

The requisite qualities of a good cloth are:

(_a_) Endurance when folded back and forth in the same place, so that it may withstand the wear at the joint caused by opening the book.

(_b_) Smoothness, so that there will be a comparatively small amount of friction when withdrawing a book from between two others on the shelf.

(_c_) Ability to withstand constant rubbing back and forth on tables.

(_d_) Color that is fast when exposed to light; if possible it should be fast to water also, though this is less important.

(_e_) Color should be dyed in the piece, not pressed in by machinery.

Many cloths have some of these qualities but few have all of them. So far as is known to the writer only the grade of cloth described on page 77 has the last qualification.

Practically all cloth used in the United States is made of cotton. The best cloths are manufactured by The Holliston Mills, Norwood, Ma.s.s.; The Interlaken Mills, New York City; The Joseph Bancroft & Sons Company, Wilmington, Del., and by the Winterbottom Company and the Manchester Book Cloth Company in England. Since a number of grades are made in several different patterns and a great number of shades for each grade and each pattern, a variety of choice is permitted. As a matter of fact, however, most librarians select a good grade with a regular weave and confine themselves to a few standard shades, such as dark green, brown, red, dark blue, and tan.

Since the strength of the warp is much greater than that of the weft, it is advisable when possible to cover books with the warp running across the cover. This, however, may entail some hardship on the binder for it may frequently happen that in order to cut his cover economically he must make the warp run lengthwise of the book. If a strong cloth is used the advantage is not great enough to be insisted upon.

Each of the American firms mentioned makes three distinct grades, all of which libraries may use. Each firm uses a different name for each grade.

In other words, there are no general names which can be used for the corresponding grade in all makes. Therefore for the purposes of this chapter these cloths will be considered under the heads of Grades 1, 2 and 3, but it must be remembered that this is an arbitrary designation not known to the trade. Under each grade will be given the specific names used by the three manufacturers.

GRADE 1

Grade one of cloth, the cheapest that a librarian may use, is not made of the best quality of cotton thread and should never be used under any circ.u.mstances for full binding. It may be used on the sides of books bound in leather; if this be done the corners should be covered with vellum, for this cloth does not withstand hard usage and is likely to fray at the corners. It is a cloth commonly used by publishers, but should be used sparingly by the librarian. "Art vellum" made by the Interlaken Mills, "Aldine vellum" made by the Holliston Mills, and "Linen finish" made by the Joseph Bancroft & Sons Company, come within this grade.

GRADE 2

(_a_) Grade two is made of a better grade of cotton and with a closer weave than the preceding, but is not sufficiently strong to be used for full binding. It can be used more satisfactorily than the preceding on the sides of books bound in leather or duck. In common with all cloths, except the buckram made according to the government specifications (which will be discussed later), the different colors are not made, as one might suppose, by dyeing the cloth after it is woven, but by mixing the color with the sizing or starch which is used in finishing the cloth, and pressing it into the cloth by machinery. As a natural result the color rubs off with wear and the natural gray of the original cloth as first woven appears. "Art canvas" made by the Interlaken Mills, "Cla.s.sic buckram" made by the Holliston Mills, and "Polished buckram,"

by the Joseph Bancroft & Sons Company come within this grade.

(_b_) _Buckram._ Under the name of buckram various grades of cloth are manufactured which resemble to a greater or less degree those mentioned under Grade 2 (_a_). Generally it is a coa.r.s.ely woven cloth stiffened with glue or sizing, and the term originally indicated that the cloth was made of linen. At the present time linen buckram made in England can be obtained, but all that is manufactured in the United States is made of cotton. Linen buckram costs much more than cotton and it is doubtful if it is any more serviceable. All of the three manufacturers mentioned make buckrams.

GRADE 3

Prior to 1907 the Congressional set of government doc.u.ments distributed to the depository libraries had been bound in sheepskin and the leather on the volumes had disintegrated so much as to make the set a hard one to care for. In 1907 the Congressional Printing Investigation Commission asked librarians of depository libraries to suggest, without considering cost, suitable binding materials for Government Doc.u.ments. The number of replies received was 124, embodying suggestions as follows: full sheep, 11; half-russia, 78; cloth, 25; buckram, 70; linen duck, 20; canvas, 19.

Some librarians expressed more than one preference, so that the total number of preferences was greater than the total of those replying. Most of those who favored sheep did so because of their desire for uniformity. Those who favored half-russia undoubtedly desired half American russia, or cowhide. 134 expressed preference for some form of cloth.

After receiving the replies from librarians the Printing Investigation Commission obtained samples of cloth from various cloth manufacturers in the United States and the Bureau of Standards made a series of chemical and physical tests to determine the durability of these cloths. Chemical tests were made to discover whether the colors were fast when exposed to light. It is to be regretted perhaps that no tests were made to determine whether the cloths were fast to water and that this qualification was not included in the final specifications. Admitting, however, that a cloth which is fast to sun and water both is a valuable cloth for bookbinding, it is evident that the quality of fastness to water is not a vitally important one for cloth used in the United States. The total number of books injured by water is so small as to make insistence upon this quality entirely unnecessary. If books become so soiled that they need to be washed they should be bound in waterproof cloth.

Because many volumes of Government Doc.u.ments are sent to Porto Rico and the Philippines where insects eat almost anything of an animal or vegetable character, the desirability of the cloth as an article of diet for insects, was also tested.

The physical tests indicated:

_a._ Number of threads per inch of warp and weft.

_b._ Absorption of moisture.