Streeter mentions a very interesting incident in regard to a genuine black pearl. This pearl, set with diamonds, was shown in a jeweler’s window; but after exposure in this way for some time to the sun’s rays, the brilliant black luster disappeared and gave place to a dull, grayish hue. When the pearl was removed from its setting, it was seen that the part which had not been exposed to the light was of as good color as when first removed from the shell. It was finally determined to skin off the outer layer, an operation which was performed with so much success that the original brilliant black hue was fully restored, proving that the action of the sunlight had only changed the color of the surface. We may add that the pearl, although it was shown in the sun, may never have had a good “skin” or layer exposed; or the layer which was not perfect may have been affected by an exudation of the wearer produced by illness or medicine.

When pearls are of a poor yellow or dull brown tint, unscrupulous dealers sometimes intrust them to an operator who drills them almost entirely through, cracks the skin slightly and impregnates them with a solution of nitrate of silver; this affects the outer layers of the pearls, and, after its decomposition, the metallic silver is deposited, and they become absolutely black. The effect is sometimes hastened by exposing them to the fumes of nitrate of silver. These pearls are then rubbed up or slightly polished and may retain a good appearance for a number of years. The upper layers, however, which have been injured by the chemicals used in the coloring, often scale off, and the poor and unattractive color beneath appears. This is sometimes not detected until years after and when the dealer from whom they were purchased has been forgotten. The breaks or cracks which have been made can readily be detected by means of a pocket lens, if the observer is at all experienced. In many cases the outer layer of the pearl has been colored a good black, although scarcely any crack is visible.

Frequently, when a small knob or protuberance appears in the pearl, or when it has adhered to another pearl or to the shell itself, this protuberance is polished off, and the pearl is drilled at this point. This portion of the surface, however carefully polished, will never have the true orient, but it is placed in the necklace in such a way that it is completely hidden. Often pearls become scratched through rough usage, or by the knife used in opening the shells. These are occasionally polished by means of pearl-powder, or else the entire outer layer is removed, the new skin beneath appearing absolutely bright and perfect. It sometimes happens that a pearl will have a good luster, but a slightly roughened skin. This is at times polished down; but an experienced eye easily detects that it has been tampered with. Yellowish pearls are sometimes bleached by means of strong bleaching substances such as chlorine or other powerful reagents, which, although they may whiten the pearl, cause it to become very friable, as the animal substance becomes more brittle. Pearls treated in this way frequently wear off, layer by layer, until fully one half of the pearl is worn out of the setting. When pearls are stained yellowish from the exudations of the skin, grease, or other impurities, they can be cleaned by putting them in moist caustic magnesia and allowing it to dry on them. When this is removed, the pearls will often be found much purer in color than before.

In various parts of the world certain dubious methods have been used for restoring the beauty of pearls which have grown dim. In India they are rubbed in boiled rice. Some persons have even fed them to a chicken fastened in a coop; after the lapse of an hour or two the chicken is killed, and the pearls rescued from their temporary lodging-place, where they have been somewhat restored by the digestive juices of the fowl.

Some curious tests applied to pearls are given us in a Hindu treatise on gems by Buddhabhatta. For instance, we read: “If the purchaser conceives a doubt as to the genuineness of a pearl, let him place it during one night in a mixture of water and oil with salt, and heat it. Or let him wrap it in a dry cloth and rub it with grains of rice; if it do not become discolored, it should be regarded as genuine.”^[416] It is needless to state that these tests would be either useless or injurious.

If the reader is the owner of a pearl or of a pearl necklace and feels that the pearls need treatment, any attempt to follow the directions given by many ancient writers would infallibly result in their injury or destruction.

Pearl drilling is a most delicate operation. It is necessary that the drill points should have the proper shape,—that is, should not be too tapering, but slightly blunt at the end, and turning somewhat in a V-shape,—it is also important that the drill should be revolved with perfect regularity, so as not to jar or jolt the pearl, as this is likely to lead to the cracking of the pearl or to the breaking of the drill. This latter happens not infrequently, and is due either to the structure of the pearl, the clogging of the drill, or to encountering a hard grain of sand inclosed in the pearl. Should the drill break in the pearl, it can best be removed by drilling from a point directly opposite, and slowly forcing the broken drill outward. This process requires great care in the regulation of the speed, and great exactness of direction in order to meet the broken drill accurately.

Pearl drilling was formerly a laborious process, and it was scarcely possible for a driller to perforate more than from forty to fifty pearls per day by means of the bow-drill operated by hand. Now, by the use of a modern machine, 1500 pearls of average size can be drilled without any difficulty in the same time.

Some of the most successful drilling of fine pearls is done by means of the bow- or fiddle-drill. The arm of this is made either of steel or of wood, with a strong cord stretched across it in the style of an archer’s bow. The drill is inserted in the end of a brass circular disk with a V-shaped groove on its edge, to admit of the string being passed entirely around it like a pulley, so that when the drill is placed on anything and held at the other side, and the bow is moved up and down, the wheel with the drill-end rotates rapidly.

If the pearl is not properly secured, if the drill point is too irregular, if it is not properly centered, or if it is too rapidly rotated at the start, one or more layers of the pearl are likely to be broken, giving an irregular, ragged appearance. If, again, the drill is rotated too rapidly as it is leaving the other side of the pearl, one or more layers are occasionally forced off, and this in turn will produce a break on the pearl. It happens not infrequently that pearls are broken away on the surfaces at both drill holes if the workman is careless.

As pearls have become more valuable, only the most efficient workmen are employed in drilling them. Whereas formerly a drill hole would be half a millimeter in diameter, at present it is much smaller, and such drilling requires the greatest skill in manipulation. The use of these very fine drill holes is due principally to the fact that pearls have become so valuable that the slightest loss, even the fraction of a grain, would amount to a considerable sum in a necklace of large pearls.

When a pearl has been perforated with a very fine drill hole, the hole may be enlarged somewhat by using a slender copper wire, the fineness of the drill hole itself, charged with either diamond-dust, emery, or sand. When the wire thus charged is drawn in and out, the drill hole can be enlarged to any desired size.

A large pearl is held in the hand or secured in a wooden block, or else it is held in a small pair of forceps with a rounded, cup-shaped receptacle at the end, which is usually lined with chamois leather and is pierced with a hole through the center. This hole serves as a guide for the drill, directing it while the pearl is being perforated. Adjustable cups or forceps with cup-like ends of every size are necessary, according to the size of the pearl; and in order that it may be properly seen, it is requisite that the pearl should always be larger than the cup in which it is placed.

The poorest part or spot is selected to form the beginning of the drill hole. The pearl is placed in a pair of calipers with a circular disk, one end of the caliper being placed on the spot to be pierced, the other end naturally touching exactly opposite, the pearl absolutely centering it. As these caliper ends have been rubbed with either rouge, lampblack, or some colored substance that will readily rub off, these two spots of color remain on the pearl and serve as a guide for the driller. The drill end is then placed on the pearl, and the bow moved up and down; and so rapid is this work that five pearls weighing fifteen grains each can be drilled with the greatest care in less than one hour’s time. Of small pearls, weighing about one grain, as many as fifty have been drilled in less than one hour by the hand-drill method.

Many of the thinnest and best drills are made out of thin steel needles. These are ground flat by means of a small carborundum wheel, so as to have two flat sides. They are then thin pointed, and with a V-shaped edge. These prevent the drill from clogging up, allowing the fine dust to pass upward and outward readily, and the hard steel almost invariably penetrates the central core of the pearl, no matter how hard or tough this may be. The needle-drill is then secured in a small chuck attached to the brass revolving wheel. Some recommend lubricating a drill with milk when it is employed for piercing a pearl, but a well-made drill, that allows the dust to escape as it is formed, does not require this treatment. The drill should always be made to revolve quite slowly so that no unnecessary heat may be generated by friction to injure the color of the pearl and also to avoid the possibility of the drill becoming clogged by the pearl-dust.

By means of centering calipers or markers, the driller, especially in the drilling of a large pearl, will generally drill first from one end, and then reverse the pearl and drill from the other end, meeting absolutely in the center. This prevents the breaking of the outer layer of the pearl. A skilful workman can, by turning the pearl, so operate the calipers that the true center can be obtained, even if the pearl is not absolutely round, and the drill holes so centered that the irregularity of the pearl is less apparent.

When the pearl has been half drilled through from one side, considerable caution is necessary in drilling from the other, that when the two drill holes are about meeting the drill be not revolved too rapidly, as the clogging is likely to crack the pearl or break the drill. If the pearl is only to be drilled one fourth or one half through, the depth can always be gaged by watching the drill-end, first, by measuring the drill-end itself, and, secondly, by noting to what part of it pearl-powder adheres.

Pearls are more easily manipulated than any other gems. They are also more easily damaged. Still, when properly treated by the workman, there is no material that offers him more satisfactory results than the pearl, if good judgment be used.

Drillers occasionally find that when the drill reaches the center of the pearl, there is a sharp click, the pearl often breaking at this point. This is evidently due to the fact that a harder kernel may exist in the center, such as a tiny grain of sand, which can turn the drill point; or else the resistance may cause the tiny drill to break.

When a pearl is cracked by a blow or by some accident, it is customary to drill it at the end of the largest crack; this method prevents the crack from extending in that direction. These fissures are sometimes partly filled by means of a solution, and may not be visible at the time when the pearl is bought, but they are liable to appear later.

To illustrate the difference in the care used in drilling, we have selected eight pearls from a paper of poor ones, and reproduce two views of them, one to show the irregularity of the pearls, and the other to show the varying size of the drill holes. Those on the left were drilled by an artist, while those on the right show the work of an inexperienced driller.

At present pendant pearls are never drilled entirely through, and rarely more than half way. But in the Orient, and even in Europe from the fourteenth to the sixteenth century, they were often entirely pierced; even pear-shaped pearls were entirely drilled through, with a metal edge projected below for safety. Frequently old pearls, and more especially oriental pearls, have been entirely drilled through, as are often large oriental rubies, diamonds, and sapphires. When these are set, the holes are either plugged with pearl shell and polished smooth, or a tiny ruby or diamond is set in a metal rim fitting entirely into the drill hole or only slightly projecting. This is well instanced in the portrait of Marguerite of France (1553–1615), in which the artist Delpech shows all the pear-shaped pearls worn by the French queen entirely pierced.

Frequently, where pearls have been drilled by oriental workmen, the drill holes are exceedingly large, five or six times the width of the silk string; in fact often from one to two millimeters in diameter. In the search to supply the great demand, many oriental pearls have been secured which formerly were strung to an oriental jewel by means of a thick wire; it is necessary to close this aperture, as the pearl would lie unevenly on the string. This is done by introducing a mother-of-pearl plug, through which a new drill hole is made. Unless the pearls are unstrung, this is rarely visible; but not infrequently the plug drops out. In other cases the pearl has been drilled not only from end to end, but also from the side, and this third hole is filled with a plug of mother-of-pearl and polished over so as to hide the blemish from the buyer. It is also no uncommon thing for a purchaser to find, after a year, that cracks begin to develop where none apparently existed at the time of his purchase, or they were so minute as to be considered of no consequence.

One of the earliest references to drilling pearls was made by Rugerus, a monk who lived in the eleventh century. He says:

Pearls are found in the sea-shell and shells of other waters; these are perforated with a fine steeled instrument which is fixed in wood, having a small wheel of lead, also another wood in which it may be turned, to which a strap must be placed by which it may be revolved. But should it be necessary that the aperture of any pearl be made larger, a wire may be placed in the opening with a little fine sand, one end of which may be held in the teeth, the other in the left hand, and by the right the pearl is conducted upwards and downwards, and in the meantime sand is applied, that the apertures may become wider. Sea-shells are also cut into pieces and are filed as pearls, sufficiently useful upon gold, and they are polished as above.^[417]

In “The Toy Cart,” a Hindu drama by Sudrake, who lived about the beginning of the Christian era, there is a description of a jeweler’s workshop attached to the house of a courtezan. He says: “Some set rubies in gold, some string gold beads on colored thread, some string pearls, some grind lapis lazuli, some cut shells and some grind and pierce coral.”^[418]

The Chinese and Korean method of drilling pearls differs materially from that of the Occident. A pear-shaped pearl is frequently drilled horizontally and secured by wire or silk, and not drilled perpendicularly, as with us, to have a metal wire or peg fastened into it. If the orientals drill a pearl perpendicularly, the hole is generally carried entirely through it, and a gold knot, which is used as a bead, is placed at the lower end, and sometimes a tiny gem is set in this peg, or else the pearl is secured either by some projection below, or by means of a bit of enamel, or some other object may be attached to the gold or wire below it. Button pearls, especially those of the abalone, are drilled horizontally through the base and secured to the ornament, or to the silk or other material on which they are sewed, by means of a thread or wire; or else they may be drilled from below by means of two sloping holes forming a V, the thread or wire being passed upward until it strikes the angle, and then passed outward again through the other branch of the hole. Many fine, round, and pear-shaped pearls of oriental origin may be seen with this end closed either with a speck of pearl, a diamond, or a ruby.

A most interesting and careful description of the methods of drilling pearls was given by James Cordiner in his valuable volume, “A Description of Ceylon,” published in London in 1807, pages 64–66.