150

METHODS OF CHUCKING TO AVOID WASTE.

supported by the center, is turned for a short distance slightly conical; ready for fixing in a plain boxwood chuck, or a brass chuck lined with wood, for the completion of the process, unless indeed it is entirely performed upon the prong chuck.

With the decrease in length less attention is requisite, on account of the interference of the curvature of the tooth; and the pieces may be at once rasped to the circular form, and then chucked either in a hollow chuck, or else by cement or glue, against a plain flat surface; the full particulars of which processes will be found in the second volume in the chapters devoted to the various methods of chucking, which should have been rendered familiar to the amateur on less costly materials, before he largely employs ivory, at any rate in the unprepared

state.

When the blocks of ivory are long and much curved, a thin wedge-form plate may be sometimes sawn from the end, in preference to turning the whole into shavings; the end is turned cylindrically for a short distance, just avoiding to encroach on the lower angle of the block, and as soon as practicable, a parting tool is used for cutting a radial notch for the admission of the saw, which may be then employed in removing a thin slice. The process is at any rate scarcely attended with more trouble than turning the material into shavings, and a thin piece is retained for a future purpose, such in fact as those beyond the dotted lines at the ends of the figures.

The hollow pieces of ivory are treated much in the same manner as those which are solid, and into which latter condition they are sometimes temporarily changed, by rasping a piece of common wood such as beech to fit into the hollow, driving it in pretty securely, but so as not to endanger splitting the ivory; the work is then centered as recently explained, the chuck and center being in this case received in the wood.

With the hollow pieces, the process of turning must be repeated on their inner surfaces, for which purpose a side cutting tool with a long handle for a secure grasp should be used; the tool should be held very firmly so as to withstand the jerking intermittent nature of the cut, until the irregularities are reduced.

For this purpose the sliding rest is very desirable, as the tool is then held perfectly fast without effort on the part of the individual, and if the chucking be correctly done, the greatest possible

CUTTING OUT IVORY RINGS.

151

economy of the material is attained; the hand tools succeed better on the outer surface, as the rest or support upon which they are then placed is so close to every point of the exterior of the work, that they may be held securely with less effort, although the sliding-rest is nevertheless desirable there also.

When the ivory hollows are thin, and far from circular, the material would be turned entirely into shavings, in attempting to produce a circular ring; the circular dotted lines, in figs. 43 and 44, are intended to explain this. Fig. 43 might be turned into an oval ring; but it is more usual to cut such irregular hollows into small square and round pieces, &c., as explained.

When thin rings or tubes are required, they are frequently cut one out of the other in the lathe, in preference to wasting the material in shavings; this is done with the parting tool, (fig. 54;) an incision being made of uniform diameter from each end,

and continued parallel with the axis, until the two cuts meet in the center short pieces may be thus divided from the one end only*. When the rings are large and thin, it is desirable to plug them at one or both ends, with a thin piece of dry wood, turned to the diameter, to prevent the ivory from becoming oval in the course of drying.

A similar mode is pursued in 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; 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 piece, a tool of considerably larger size may be used to extract a much wider ring. A little tallow or oil applied to the parting tools will, in a great measure, pre

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

152

SEASONING AND SHRINKING OF IVORY.

vent the shavings of the ivory from sticking to them and impeding their progress. The dotted lines represent the paths of the respective tools, the shaded part the ring obtained, the black lines the tools themselves.

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 chessmen, &c., 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 after the same manner, 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 degree.

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 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 billiardballs, 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 circle for some months

See foot note, p. 47. The Tithe Commissioners there referred to, refuse to sanction ivory drawing scales at all, as although they may appear to be correct at the time of observation, they find them subject to a variation from atmospheric influence. See their Papers

IVORY CANNOT BE BLEACHED OR SOFTENED.

153

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.

Ivory agrees likewise with wood, in shrinking unequally upon the radius and tangent when cut out of quarterings, as explained by the fig. 14, p. 49: on this account, billiard balls are always made out of teeth only so much larger than themselves, as the thickness of the coat or bark, and which sized teeth procure an advanced price.

It may be asked what means there are of bleaching ivory which has become discoloured, I regret to add that I am 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, or those worked with the 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, as the keys of piano-fortes, &c., 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 pearlash 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 better not to resort to the practice, which is only employed to render that ivory which is partly opaque and partly transparent, of more 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; in thick pieces it suffers no change in boiling water, although thin shavings give off their jelly, which substance is occasionally prepared from them;

154

IVORY VENEERS.- -DIAMOND CEMENT.

truly the caustic alkali will act upon ivory as well as upon most animal substances, yet it only does so by decomposing it; ivory, exposed to the alkalies, first becomes unctuous or saponaceous on its outer surface, then soft if in thin plates, and it may be ultimately dissolved provided the alkali be concentrated; but it cannot in either case be made to resume its first condition.

Ivory is not in all cases used in solid pieces, to which the foregoing remarks principally apply; but it is frequently cut into thin leaves and glued upon fabrics of wood, for the manufacture of small ornamental boxes, and works of various kinds, after the manner of the veneers of wood, or the plates of tortoiseshell; it is also used in buhl works, combined with ebony, &c.

Such thin plates are usually cut out of the solid block, with a fine feather-edge veneer saw, parallel with the axis of the tooth, as at c, d, in fig. 50; but the mode introduced in Russia for cutting veneers spirally from a cylindrical block of wood, with a knife of equal length, (as if the veneer were uncoiled like a piece of silk or cloth from a roller,) has been latterly applied to the preparation of ivory into similar veneers, converting the cylinder of ivory into one ribbon, probably by the action of a reciprocating saw*.

The ivory thus divided must be necessarily very thin to be sufficiently pliant; and as ivory is admitted to be more transparent than writing-paper of equal thickness, this introduction promises to be of more use for the artist in water-colours than for veneering, as from their transparency such thin leaves are apt to show the colours of the wood or glue; on this account the ivory for veneering should not be extremely thin; and the woods and glue should be selected of very light colours.

The modes pursued in these works are analogous to those already described in the fifth chapter in reference to the woods; it is therefore, only necessary to add a few words on the whitefish glue, or " Diamond cement," as it is sometimes called, which very often used for ivory-work, both in attaching ivory to ivory, and ivory to wood.

is

* Monsieur H. Pape, of Paris, piano-forte manufacturer, has taken out patents for this method of cutting ivory spirally into sheets. A specimen, 17 inches by 38 inches, and about one thirtieth of an inch thick, glued upon a board, may be seen at the Polytechnic Exhibition in Regent-street, and M. Pape advertises to supply sheets as large as 30 by 150 inches. He has veneered a pianoforte entirely with ivory.