Sometimes tortoiseshell is inlaid with mother-of-pearl, gold, or silver, as may be seen on occasions in brooches, earrings, and hair ornaments. This is carried out by arranging the ornamental pieces on the shell and then pressing them in with the aid of boiling water. The article is then suddenly submerged in cold water and pressure again applied.
Tortoiseshell was regarded as a valuable ornamental material in very early days, and it was then probably more highly esteemed than now since today we have such a wide choice of both natural and artificial substances. The shell was brought to ancient Rome from the East via Egypt, and the Romans used it largely as a veneer on their furniture. According to Pliny, Carvillius Pollio was the first to apply tortoiseshell to ornamental purposes. Strabo, Diodorus, and Pliny all write of boats made from shells of the tortoise, but how these boats were constructed is not described.
Besides being used in the manufacture of toilet articles and jewelry, its most common function, tortoiseshell has been extensively used in the making of Buhl furniture. It was formerly much used as an inlay in cabinets, picture frames, and clock cases. Boule (1642-1732), a cabinet maker in the service of Louis XIV, used this shell largely as a veneer with wood in the making of furniture, and hence the term buhl has since been applied to all similar work.
In general, tortoiseshell is worked in much the same way as is horn. The plates are separated from the bony skeleton of the animal by heat, but care is needed as an excessive heat tends to darken the color. Again, although boiling will soften the shell, prolonged boiling spoils the color. For this reason, salt is often added to the water, but this has the disadvantage of rendering the shell brittle if too strong a solution is used.
A factor which makes the working of tortoiseshell much easier is the facility with which it may be joined together and shaped. Two’pieces may be united by simple pressure alone, but more often a gentle heat is used. In the latter instance, edges are first beveled, scraped clean, and then compressed in a press which is placed in boiling water. The press is tightened from time to time, and in a few hours the joint is complete without injury to color or to texture.
Tortoiseshell may also be molded, and by this means cigarette cases, boxes, beads, and larger articles are produced. In molding, the shell is first cut roughly to size in the flat and then placed in a mold which is lowered in boiling water. In about half an hour, the block may be pressed into the mold, carrying the shell with it. The article is subsequently finished on a lathe. As the shell is fairly expensive, chips and dust are collected and used later; they are softened, pressed together, and molded, but the resulting material is almost opaque and therefore of inferior appearance and value. Coloring matter is also often used in this process.
Tortoiseshell is not obtained from the tortoise, as the name may lead one to believe, but from the hawk’s-bill turtle. The turtle is a group of animals which lives in the sea, or they spend most of their time in the water since their food consists almost wholly of fish and molluscs. Many varieties of turtle are very useful as food and they are regarded by some as great delicacies, but the hawk’s-bill does not come within this class. Its chief value lies in its shell, which consists of thick, horny, overlapping shields or plates. This is the source of the material which we know as tortoiseshell.
There are 13 such plates on the back of the animal (known in the trade as blades); five occupy the center, and four may be found on each side. All overlap each other, the largest sometimes reaching the size of 14 inches by 8 inches, and the weight of about nine ounces. The marginal plates, 24 in number, are commercially of inferior value, but all consist of a horny material which cannot be considered as true shell, although they are distinctly harder, more brittle, and less fibrous than ordinary horn, which they closely resemble.
The thirteen larger plates are called the heart, and the back plates are known as hoofs or claws. The 24 marginal pieces, which have rounded edges, are called feet, or noses. As a rule, these are one-eighth to one-quarter of an inch in thickness, and the shell from an average sized turtle weighs from five to six pounds. The value of this material depends on the richness of the mottled colors and the capacity for a high polish which it takes and rein ins. The most sought after color is the warm, translucent yellow, spotted with rich, brown tints.
The hawk’s-bill turtle may be found in most tropical and subtropical seas, but the brown and light colored shells are imported chiefly from India and China. The finest comes from the Eastern Archipelago, especially from the east coast of the Celebes and New Guinea. The West Indies, Australia, Africa, and the Brazilian coasts are also well known homes of the turtle.
Some mention must also be made of vegetable ivory. This is a kind of palm, known to botanists as phytelephas, but usually called the tagua palm. It is a native of tropical South America, growing wild along the west coast from Panama through Colombia and Ecuador. It is found in damp localities and usually grows apart from other shrubs.
The plant is a palm fern, 10 to 20 feet high, with a short trunk, crowned with large, bright green, feathery leaves. The head is filled with seeds, these being enclosed in a hard covering. The fruit is somewhat similar to a coconut, growing in drupes about the size of a man’s head. The seeds are hard, white, and finely grained, very much like real ivory, and as they ripen, they get harder.
A single plant may have six to eight heads, each weighing about 20 to 25 lbs. Natives gather the matured nuts after they have fallen to the ground and sell them to traders. The American Indians use these nuts or seeds for making small, ornamental articles, but we import them under the name of “corozo nuts,” and use them in the making of buttons, umbrella handles, chess men, counters for card games, and other small articles.
Vegetable ivory may be distinguished from genuine ivory by touching it with concentrated sulphuric acid. The former will show a pink coloring in about ten minutes’ time (which may be removed by washing in water). Real ivory is unaffected. Good imitations of real ivory are made from many of the modern plastics, while a German product is the result of chemically treating coral. This latter largely possesses the properties which render natural ivory so easily workable.
Although ivory carving flourished during the Renaissance, the Nineteenth Century saw its greatest development. All kinds of beautiful articles were produced, and these were enhanced by the addition of suitable gem stones. In a far earlier age, ivory had been used for decorative purposes and numerous references to it occur in the Bible, thus showing that it was regarded as being of great value in those days. It seems to have been used in the deed ration of the Temple. The Ninevah ivories in the British Museum are of very great antiquity, yet they are still in a good state of preservation.
In Europe, Germany, France, and Belgium are now the chief centers of ivory carving and working, but the larger and more intricate pieces which demand unlimited time, patience, and ingenious skill for their execution come from the East. China, Japan, India, and the East Indian Islands all export quantities of carved ivory goods and a wide range of their work, both good and bad, may be seen in many countries. Chinese ivories of outstanding beauty are rare, and the older pieces were never signed by the artist, which makes it difficult to assign a date to them.
In addition to ornamental and decorative articles, ivory is also used in the making of billiard balls, handles of knives and forks and toilet articles, but since the material is affected by extremes of temperature, its practical uses in these directions are limited. Only the best quality may be used in the making of billiard balls, and these are far superior to those made from an artificial material for the latter lack the elasticity of the natural substance. The making of billiard balls requires great accuracy of workmanship. When first cut, ivory is semi-transparent, and as it dries, it becomes much lighter in color and more opaque. Shrinkage also takes place, so tusks are usually first seasoned, as is wood, before being cut.
Hippopotamus ivory is beautifully white arid hard; it is generally covered with a white enamel, and when dried, the tusks often split into two perfectly equal longitudinal halves. The enamel is, as a rule, first removed by acid or by other means before working on the material. Since no large pieces are obtained from this type, it is used in the making of smaller objects, such as umbrella and stick handles.
Walrus ivory is coarser than hippopotamus ivory, and it is fairly rare. It has a nodular appearance when cut and polished, being very dense and uniform in consistency. Tusks are about three feet in length, and weigh from 7 to 15 lbs. Narwhal ivory comes from the single horn of an Artie whale. It is thick, perfectly straight, but it often contains fissures and cracks. The point of the tusk is always very sharp, and the whole tusk, as well as that of the cachalot whale, is very small.
On account of its characteristic properties, ivory lends itself to the art of carving, and many beautiful specimens and collections exist. Jean Coujou, Albrecht Diirer, Michaelangelo and other artists found expression in ivory carvings. Bowls and tankards were once especially favored, but today, all kinds of articles, both useful and ornamental, are made. Figures of animal and human life, if well carved, are greatly admired as are also miniature paintings on ivory, for the natural color of the material resembles that of the human skin. In articles of utility, however, the use of ivory has, in recent years, been largely replaced by many of the synthetic plastics.
Taken in a wide sense, ivory is the term used in connection with the large teeth, or tusks as they are more usually called, of the elephant, rhinoceros, hippopotamus, walrus, narwhal, and the sperm whales. In a restricted sense, the term is applied only to the tusks of the male elephant.
In young elephants, these tusks are almost hollow throughout and do not fill up until the animal ages. For this reason, the tusks of the adult elephant are the most valuable. The organic substance of which ivory is composed is permeated by an immense number of minute canals, and their regularity and small size are the reasons for the fineness of grain which is so characteristic. The effect of these curved canals, something similar to “engine turning” on metal, may be seen if a section transverse to the tusk be examined. In this respect, it differs from bone, apart from its having a finer structure and greater elasticity. Bone also shows specks or stripes if a transverse longitudinal section be examined.
Although very dense, ivory is porous, and the pores are filled with a gelatinous solution which contributes to the beautiful polish which it takes. It also facilitates easy working, and simple tools may be used with success. One has only to note the many specimens of intricate ivory work done by the Chinese, Japanese, and Indians to realize that skill and patience are the most necessary tools in carving ivory.
Firstly, we shall consider ivory, for it is a material with which most of us must be familiar on account of the wide range of uses^ to which it has been put. That it is a suitable medium for displaying expert craftmanship is proved by the constant use which artists have made of it throughout the ages. The study of carved ivories in itself would be the work of a lifetime, for even such widely different objects as caskets, pocket books, combs, and crucifixes would have to be considered. At Copenhagen, for instance, is the ivory crucifix which belonged to Gunhilde, the niece of Canute the Great. At South Kensington is the marvelous cup made in the year 1691 by Senger, ivory craftsman and turner to Cosimo III, Grand Duke of Tuscany.
Of an earlier date are the old shaped carved rests to prevent the hands of scribes from soiling the crabbed characters of the Fifteenth Century. Then there are horns of Byzantine workmanship, chess men, pyxes, pen cases and ink-horns from Turkey, pastoral staffs, wands of office, dice, sun dials, scent bottles and powder flasks. Of the Seventeenth Century are French tobacco graters elaborately ornamented with classical themes; of the Eighteenth Century are seals, walking stick handles, and powder puff boxes from Germany, while with the date of 1780 are charming ivory buttons from Normandy. But of all the achievements of the artist in sculptured figures and medallions in ivory, perhaps the most enchanting are the six Italian Seventeenth Century plaques of little fauns and satyrs by Francis Duquesnoy, called II Fiammingo.
Thus, apart from the modern articles of utility and ornament which one sees made from this attractive material, it will be readily recognized that there are many outstanding works of art in ivory which date back to very early days, so proving that it has always been considered as a suitable artistic medium. Art museums throughout the world invariably contain specimens of the artist’s skill in ivory carving, and these are of every period through which civilization has passed.
Certain organic products, pearl, coral, amber, and jet have already been discussed since they are generally considered as being closely connected with gem stones. But there are other similar products which are widely used in jewelry and ornament, and which are quite often used in combination with gem stones. These substances really have no scientific relation to jewel stones since they are not the result of a natural inorganic process; they are not minerals, but the products of some organism which has once lived.
The material is in demand in almost every country in the world, and new sources of supply are continually being searched for since good ivory realizes an appreciable price. Most of the raw ivory that comes on the market originates from elephant graveyards, and not from animals which have been killed recently. Elephants seem to have a natural instinct which tells them when their death is approaching, and in their old age, they make their way to a common burial ground. Such graveyards are often hidden in the depths of the forest, and discovery is difficult. But such deposits of ivory are found, and the greatest difficulty then is to transport the material to the coast.
As a rule, the dealer has to purchase his ivory from natives, and this usually involves much bartering. From the coast, it is shipped either to Antwerp or to London, where the tusks are sold by auction. London is the greatest market, but the Congo trade has made Antwerp an important center also. Liverpool and Hamburg are other ports to which ivory has been shipped.
Africa produces most of the commercial tusk ivory since both the male and female elephants of that continent possess tusks. These animals were common over almost the whole of that vast area until comparatively recent times, and they are still abundant in the central parts. The Indian elephants of the female species have either small tusks or none at all.
Tusks are really the upper incisor teeth of the elephant, and they are built up in layers, the inside layer being the last to be formed. On account of their peculiar development, tusks are always curved; in length, they often reach over four feet and weigh up to 150 lbs. Tusks of the female animal are always smaller, and a larger proportion is embedded in the bone sockets of the skull. They are hollow for some distance up in a conical form.
African ivory is very resilient and possesses remarkable plastic qualities. Although of a warm, mellow tint, it becomes yellow in the course of time, and when dry, it tends to shrink and crack, which is detrimental to its use in articles of utility. However, it is easily worked and colored; it bleaches without difficulty and takes a fine polish. Qualities vary with the country of origin; Indian ivory is finer and tougher, and the tusks from Bengal, Burma, Malacca and Sumatra are smaller than the African tusks. These smaller tusks are usually regular and tapering in shape, seldom weighing more than 50 lbs. The hardness of ivory on Mohs’ scale ranges from 2 to 3; the specific gravity varies from 1.70 to 1.9.3, and the refractive index is about 1.54.
Mammoth ivory is found ,in the U.S.S.R. (Northern Russia and Siberia), embedded in ice or in caves. This type of ivory is harder and more brittle than the more recently produced ivory, but it is often spoiled by the presence of cracks, which reduce its value considerably. The Siberian deposits have been worked for about two hundred years, yet they still appear to be inexhaustible. The Lena and other great rivers flowing into the Arctic Ocean, as well as the Liakhoff Islands, are the chief sources of supply. Ivory workers do not favor this kind of ivory as it is dry and brittle, and it is also liable to change to a yellow color very quickly.