Very little is known by the mechanic, of the real process of transforming a rough and apparently worthless-looking pebble into a stone of the greatest brilliancy and lustre. The change wrought in the stone as it passes through the cutter's and the polisher's hands is the result of a tedious, difficult, and dirty process. It is remarkable that the purest diamond, though perfectly colourless, when reduced to powder, is always of a black or black-gray colour. In all the operations through which a diamond passes the utmost skill and judgment are required, every detail, even from the preparation of the tools to the finishing whirl of the polishing wheel, demanding a thorough acquaintance with the nature of the stone. As scarcely two stones are alike in shape, it necessarily follows that a different treatment, more or less varied according to circumstances, is required in polishing each stone. Thus, the excellence of workmanship depends entirely upon the good judgment and skill of the polisher. It is in some cases years before a man can be entrusted with valuable stones, and the difficulties which an apprentice experiences in learning his trade are so many that it is not surprising that, unlike other mechanical pursuits, the supply of labour is scarcely ever above that of the demand.
The slightest error on the part of the operator may utterly destroy the value of a stone, hence men of known experience and skill are always in request. The wages of a diamond polisher are far above those of any other mechanical pursuit, ordinary polishers and cutters earning when in full work from 8/. to 10/. a week. But as each workman is paid per carat and not a weekly wage (except the apprentices or lads), a man's income generally depends upon his industry and energy.
The art of diamond cutting was almost a secret, or very little understood till the year 1476, when one Bergheim, a resident of Bruges, introduced the practice of using diamond powder for forming and polishing the facets. Holland for many years enjoyed the entire monopoly of the trade, and to this day Amsterdam is the great centre of the industry. And although this monopoly has for some years been broken by the establishment in London and elsewhere of workshops, yet Holland still continues to supply both the workmen and their tools. The latter are somewhat roughly made, and might be largely improved upon, although there can be no question of their adaptability to the work. It is owing no doubt to the small demand in England for the machinery and implements for this special industry which has caused the total neglect in their manufacture by English mechanicians. At present the demand would certainly not pay for their manufacture, but the attention of practical men might well be turned to the improvement of the appliances used by diamond cutters and polishers. While Holland and the Dutch have kept the trade in their own hands, it. is the Dutch Jews that Holland has to thank for this exclusive industry. The trade is almost entirely in the hands of this industrious people.
It is owing to their characteristic energy and perseverance that the trade has so largely developed. To be a good workman one must be steady, doggedly persevering, temperate, industrious, and painstaking, and these qualifications are generally found among the descendants of the ancient race. They are therefore well adapted by nature for the tedious process of diamond polishing, and they have contrived to keep it in their hands for centuries. Hatton Garden appears to be not only the centre of the London trade, but also the mart for the sale and purchase of the finished gems.
The first process is what is called " cutting " the stone - albeit this cutting is really rubbing. When in its rough state, the stone presents a rugged appearance, shapeless, and full of sharp angularities. It is the cutter's work to reduce the indefinable pebble to something like shape and form, and thus render the work of polishing easier and more expeditious. Should the diamond possess flaws - that is, spots which militate against its commercial value - recourse is had to cleaving, in which operation these flaws are removed without decreasing to any considerable extent the size or value of the stone. Cleaving is effected by means of a small knife tapped lightly with a hammer. To successfully cleave a diamond the utmost care is necessary, and the cleaver must be thoroughly acquainted with the fibre of the stone. To an outsider there is no such thing as a fibre to a diamond; to the cleaver there is, and unless the knife is placed in one certain position the whole stone is likely to be spoilt.
The diamond is, by means of a certain kind of cement, which rapidly hardens when cooling, fixed to the end of a stick termed the "snyder's " or cutter's stock (Fig. 1). This stock is fastened in a sort of vice, and the cleaver, placing his knife on the edge containing the flaw, gives it a gentle tap with a hammer, and the piece is at once divided in a similar way to the cleaving of slate. But it is only when a stone contains these flaws that cleaving is resorted to, so that practically the first operation is that of cutting. This is effected by placing two stones to be cut each in a snyder's stock, as before described, with the rough edges of the stone to be cut so fixed that the edge of the one may easily be rubbed against the edge of the other. This is a very laborious and tiring work, and the cutter is compelled to wear thick leather gloves. Even this precaution does not prevent the rapid growth of corns on the hands and fingers. The rubbing is done over a small brass box A (Fig. 2), which has a double bottom, the one above being pierced with numberless minute holes, through which the powder as deposited from the rubbing falls into the lower box.
This powder is carefully preserved, ami, mixed with the finest Lucca oil in the proportion of 30 drops of oil to the carat of powder, is afterwards used to polish the stones. In order to facilitate the work, the cutter rests the two stocks against two pins B, "which act as a sort of fulcrum. When all the rugged irregularities of form have been removed by the cutter, the stone is handed to another workman, who proceeds to fix it by means of molten lead in an instrument called the "dop," which is in form similar to the acorn. To the cup is attached a length of thick but remarkably pliable copper wire, specially prepared in Holland for this purpose (Fig. 3). The cup being filled with lead, the diamond is inserted at the apex of the little mound of lead in the position required by the polisher. The height and size of the mould depends upon the nature of the stone, some requiring a high and well-defined apex, others almost a globe. The dop is handed to the polisher, who proceeds to place it in the tongue (Fig. 4). The wheel upon which the stones are polished or ground is the ordinary lapidary's wheel, but much more care is required in its preparation.
There is a class of workmen who do nothing else but prepare the wheels for the polisher.
A large variety of stones are required to reduce the surface of the wheel to the requisite fineness, and all these stones are imported, as well as everything else connected with the trade, from Holland. In fixing the wheels, the most perfect balance is required, as the slightest vibration may destroy a diamond. the wheel is turned very rapidly. The tongue is fixed by means of two iron uprights in its proper position, and the surface of the diamond to be polished is kept pressing against the rotary wheel by means of a leaden weight placed on the broad surface of the tongue (Fig. 4). Before setting the stone on the wheel, the polisher applies to the diamond a small drop of the powder and oil well mixed. The dust procured by the catting is never sufficient for the polisher's use; consequently stones of a very inferior quality, and of no commercial value as gems, are first ground to powder in the "meteer " or grinder (Fig. 6). This consists of a metal mortar A and a ramrod-like pestle B, which, when worked up and down in the same way as a churn, gradually reduces the stones to powder. The powder is thoroughly incorporated with the oil, and presents a thick black sticky appearance.
But the powder, owing to its heavy weight, sinks rapidly, and it is only by constant stirring that the mixture is kept ready for use. The dop is so placed on the wheel that the part to be polished comes directly in contact with its surface. The revolving wheel gradually - very gradually indeed - wears away the surface in contact with it, and the polisher must use his judgment as to the size and form of the facet he wishes to produce, which, of course, depends upon the size of the stone. In all, the stone has to be polished on 62 surfaces - that is, there are on the largest as well as on the smallest diamond 62 facets. The facets are known as the table or top, the cutlet or bottom, hooks or corners, sides, ends, end facets, and verstelletje or stars. The wheel, or, as it is termed in Dutch, the "skyf," has to be continually re polished and ground, for although the wheel grinds the diamond, the diamond en revanche grinds the stone, consequently in time the surface of the plate is reduced to uneven rings. As a rule, a polisher has four stones in hand at once, and great care is taken in keeping the stones perfectly cool. The period of completion varies with the size of the diamond, some large stones taking weeks to polish. But the same care must be taken with small as with large stones.
As no two stones are precisely of the same dimensions, it follows that the sizes of the facets also vary. It will be seen what care and judgment is required in polishing each surface to its requisite shape, size, and angle. The utmost care and skill are also required in placing the dop to its exact angle, so that the skyf produces the proper facet. In fact, in each branch of the trade every workman must be, and is, well up in his work. Thus the lads who fill in the dops with lead, handle with their naked fingers, with the utmost sang froid, the hot liquid while even in a molten condition. The dust produced by the action of the wheel closely resembles soot - in fact, it is nothing but carbon. When the stone leaves the polisher's hands it is a bright, glowing, sparkling gem, and only requires setting in the article it is intended for.