Many of the works in tortoiseshell are made, partly by cutting them out of the shell, and partly by joining or adhesion, called by the French souder. Thus in the Manuel du Tourneur,* the artist is directed to form the ring of tortoiseshell for the rebate of a box, by cutting out a long narrow slip of the shell; the ends are then to be filed with a clean rough file to thin feather edges, to the extent of three quarters of an inch of their length, the one on the upper and the other on the lower surface, to constitute the lap or joint; the slip is dipped into boiling water, and when softened it is bent into an oval form with the intended joint on the flat side, the ends are held in firm and accurate contact with the finger and thumb, and the piece is dipped into cold water to make it retain the form.

Fig. 33.

Tortoiseshell Part 2 10025

A pair of tongs is required, such as those in fig. 33, with flat ends measuring about one inch wide and three or four long, and that spring open when left to themselves, but fit perfectly close and even, when compressed; these are made warm. In the mean time the ends of the ring arc sprung asunder sideways, to bring the scarfs or parts to be joined to the inner and outer surfaces respectively, that they may be retouched with the file to remove any small portion of grease which may have been accidentally picked up, and the joint is restored to its proper position. A piece of clean linen is then soaked in clean water, squeezed dry with the fingers, folded in ten to twenty thicknesses, to a about the size of one and a half inch wide, and three or four long; the ends are now folded together, placed on each side the joint, the whole is inserted between the tongs, and fixed moderately tight in the jaws of an ordinary vice. The softening, and consequent adhesion of the shell, will be known by the flexibility of the ring when the loose part is wriggled about with the fingers; the work is cither allowed to cool in the vice, or after a time is dipped into cold water.

* Manuel du Tourneur, 1816. Vol. I., p. 454.

The success of the process will depend on three different cir-cuinstances; the parts to be joined must be entirely free from grease and dirt, on which account the surfaces should nut be touched after being filed; the temperature of the tongs should be just sufficient to colour writing-paper, of a pale orange tint; and moisture or vapour must be present, apparently to liquefy the gelatine of the tortoiseshell at the surfaces of union.

The ring when cold, is pressed with the fiugers into the circular form, or even into an oval in the opposite direction, which would cause the ends of the joints to start, if the soldering were imperfectly performed; should this happen, the application of the moistened rag and heated tongs must be repeated until the result is perfect; the ring is made circular by warming it in boiling water, and gently forcing it on a wooden cone of small angle.* Another mode, the invention of an amateur, is also described; the strip of shell is chamfered off at the ends and bent round a piece of wood, a compress of linen in six or eight folds is put upon the joint, and the whole is tightly bound round with string, and immersed in boiling water for ten minutes. The contraction of the string, and the expansion of the wood, from being wetted, supply the needful pressure, and the process is said to be quite successful.†

Moulding and soldering tortoiseshell are also performed under water in various other ways; for example in attaching the back of a large comb to that piece which is formed into the teeth; the two parts are filed to correspond; they are surrounded by pieces of linen and inserted between metal moulds, connected at their extremities by metal screws and nuts; the interval between the halves of the mould being occasionally curved to the sweep required in the comb. Sometimes also the outer faces of the mould are curved to the particular form of those combs in which the back is curled round, so as to form an angle with the teeth; the joint when properly done cannot be detected either by the want of transparency or polish at the part.

* Manuel da Tourneur, 1816. Vol. I, p. 454. † Idem, p. 455.

Considerable ingenuity is shown in turning to economical account the flexibility of tortoiseshell in its heated state; for example, the teeth of the larger descriptions of combs are parted, or cut one out of the other with a thin frame-saw, when the shell, equal in size to two combs with their teeth interlaced as in fig. 34, is bent like an arch in the direction of the length of the teeth as in fig. 35. The shell is then flattened, the points are separated with a narrow chisel or pricker, and the two combs are finished whilst flat, with coarse single-cut files, and triangular scrapers; and lastly they are warmed, and bent on the knee over a wooden mould, by means of a strap passed round the foot, in the manner a shoemaker fixes the shoe last. Smaller combs of horn and tortoiseshell are parted whilst flat, by an ingenious machine with two chisel-formed cutters placed obliquely, so that every cut produces one tooth, the repetition of which completes the formation of the comb.* Ivory and boxwood combs cannot be thus parted; they are cut in the old way, one tooth at a time, by various contrivances of double saws, as will be explained.

Figs. 34.

Tortoiseshell Part 2 10026

35.

Tortoiseshell Part 2 10027

Figs. 36.

Tortoiseshell Part 2 10028

37.

Tortoiseshell Part 2 10029

38.

Tortoiseshell Part 2 10030

In making the frames for eye-glasses and spectacles, the apertures for the glasses were formerly cut out to the circular from, with a tool something like a carpenter's center-bit, or with a crown taw in the lathe; the disks were in either case preserved, to be used for inlaying in the tops of boxes, and the outside of the frame was then shaped with saws and files. This required a piece of tortoiscshell of the entire size of the front of the spectacles, but a piece of a third that width is made to answer for inferior spectacles, as the eyes are strained, or pulled. A long narrow piece of the material is cut out, and two slits are made in it with a thin saw; the shell is then warmed, the apertures are pulled open, and fashioned upon a taper triblet of the appro-priate shape: figs. 30, 37, and 38, explain this method: the groove for the edge of the glass is cut with a small circular cutter, or sharp-edged saw, about three-eighths or half an inch diameter, and the glass is sprung in when the frame is expanded by heat. Tortoiscshell is also manufactured into boxes and a variety of moulded works, but the process calls for extensive preparations, and is not often followed by the amateur.