Preparation Of Ivory Etc Part 3 10039

Fig. 55 explains the mode of preparing such an object as a snuff-box out of a solid block; that is, with the ordinary parting tool entered from the front, and the inside parting tool entered from within; the incisions of which meet and remove a series of rings. The dotted lines represent the paths of the respective tools, the shaded parts the ring obtained, and the black lines the tools themselves. An aperture must necessarily be made in the center, of a diameter equal to the extreme width of the tool; but after the removal of the first or central ring, a tool of considerably larger size may be used to extract a much wider ring; and a little tallow or oil applied to the parting tools will, in a great measure, prevent the shavings of the ivory from sticking to them and impeding their progress.

* Solid pieces of ivory about 4 to 6 inches long, and 1 1/2 to 2 inches diameter, cut out in this manner, are often imported from India.

Before quitting the subject of the preparation of ivory for the lathe, let me advise those amateurs, who may be desirous to produce either one large specimen of ivory work, or several pieces forming a set, as of draftsmen or chessmen, to endeavour if possible to make the whole of the work from one tooth; as although the colour of ivory may be considered as yellowish white, and therefore, like writing-paper pretty much alike, such is not the case, and it is often extremely difficult or almost impossible, to match pieces from two different teeth, so that the colour, transparency, and fibre, shall exactly agree.

Ivory requires a similar drying, or seasoning, to that recommended for wood; as when the pieces cut out of the tooth are too suddenly exposed to hot dry air, they crack and warp nearly after the same manner as wood, and the risk is the greater the larger the pieces; and on this account ornaments turned out of ivory or wood, especially those composed of many parts, should not be placed upon those chimney-pieces which, from their size, are so close to the fire as to become heated thereby in any sensible manner.

Notwithstanding the difference between the component parts of wood and ivory, and that the latter does not absorb water in any material degree, it is subject to all the changes of size and figure experienced by the woods, and in one respect it exceeds them, as ivory alters in length as well as width, whereas from the former change wood is comparatively free.*

The change however is very much less in the direction of the length than the width; this is particularly experienced in billiard-balls, which soon exhibit a difference in the two diameters, if the air of the apartment in which they are used, differ materially from that in which the ivory had been previously kept. The balls are usually roughly turned to the sphere, for some months before they are used, to allow the material to become thoroughly dry before being turned truly spherical; and in some of the clubs they even take the precaution of keeping the rough balls in their own billiard-room for a period, to expose them to the identical atmosphere in which they will be used.

* See foot note, p. 4 7. The Tithe Commissioners there referred to, refuse to sanction ivory drawing scales at all, as although they may appear to be correct;it the time of observation, they find them subject to a considerable variation from atmospheric influence. See their Tapers.

Ivory agrees likewise with wood, in shrinking unequally upon the radius and tangent when cutout of quartering, as explained by the fig. 14, p. 49: on this account, billiard balls arc always made out of teeth scarcely larger than themselves, which sized teeth are called "ball teeth," and procure an advanced price.

It may be asked what means there arc of bleaching ivory which has become discoloured; the author regrets to add that he is unacquainted with any of value. It is recommended in various popular works to scrub the ivory with Trent sand and water, and similar gritty materials; but these would only produce a sensible effect, by the removal of the external surface of the material, which would be fatal to objects delicately carved by hand or with revolving cutting instruments applied to the lathe.

Perhaps it may be truly advanced that ivory suffers the least change of colour when it is exposed to the light, and closely covered with a glass shade. It assumes its most nearly white-condition when the oil with which it is naturally combined is recently evaporated; and it is the custom in some thin works, such as the keys of piano-fortes, to hasten this period, by placing them for a few hours in an oven heated in a very moderate degree, although the more immediate object is to cause the pieces to shrink before they are glued upon the wooden bodies of the keys. Some persons boil the transparent ivory in pearl-ash and water to whiten it; this appears to act by the superficial extraction of the oily matter as in bone, although it is very much betterr not to resort to the practice, which is principally employed to render that ivory which is partly opaque and partly transparent, of more nearly uniform appearance.

It is imagined by some that ivory may be softened so as to admit of being moulded like horn or tortoiseshell, its different analysis contradicts this expectation; thick pieces sutler no change in boiling water, thin pieces become a little more flexible, and thin shavings give off their jelly, which substance is siderably larger size may be used to extract a much wider ring; and a little tallow or oil applied to the parting tools will, in a great measure, prevent the shavings of the ivory from sticking to them and impeding their progress.

Before quitting the subject of the preparation of ivory for the lathe, let me advise those amateurs, who may be desirous to produce either one large specimen of ivory work, or several pieces forming a set, as of draftsmen or chessmen, to endeavour if possible to make the whole of the work from one tooth; as although the colour of ivory may be considered as yellowish white, and therefore, like writing-paper pretty much alike, such is not the case, and it is often extremely difficult or almost impossible, to match pieces from two different teeth, so that the colour, transparency, and fibre, shall exactly agree.