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TORTOISESHELL

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Originally appearing in Volume V27, Page 71 of the 1911 Encyclopedia Britannica.
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TORTOISESHELL . The tortoiseshell of See also:

commerce consists of the epidermic plates covering the bony See also:carapace of the hawksbill turtle, Chelonia imbricala, the smallest of the See also:sea turtles. The plates of the back or carapace, technically called the See also:head, are 13 in number, 5 occupying the centre, flanked by 4 on each See also:side. These overlap each other to the extent of one-third of their whole See also:size, and hence they attain a large size, reaching in the largest to 8 in. by 13 in., and weighing as much as 9 oz. The carapace has also 24 marginal pieces, called hoofs or claws, forming a serrated edge See also:round it; but these, with the plates of the plastron, or belly, are of inferior value. The plates of tortoiseshell consist of horny See also:matter, but they are harder, more brittle, and less fibrous than See also:ordinary See also:horn. Their value depends on the See also:rich mottled See also:colours they display—a warm translucent yellow, dashed and spotted with rich See also:brown tints—and on the high See also:polish they take and retain. The finest tortoiseshell is obtained from the Eastern See also:Archipelago, particularly from the See also:east See also:coast of See also:Celebes to New See also:Guinea; but the creature is found and tortoiseshell obtained from all tropical coasts, large supplies coming from the See also:West See also:Indian Islands and See also:Brazil. Tortoiseshell is worked precisely as horn ; but, owing to the high value of the material, care is taken to prevent any See also:waste in its working. The plates, as separated by See also:heat from the bony See also:skeleton, are keeled, curved, and irregular in See also:form. They are first flattened by heat and pressure, and superficial inequalities are rasped away. Being harder and more brittle than horn, tortoiseshell requires careful treatment in moulding it into any form, and as high heat tends to darken and obscure the material it is treated at as See also:low a heat as practicable.

For many purposes it is necessary to increase the thickness or to add to the superficial size of tortoiseshell, and this is readily done by careful cleaning and rasping of the surfaces to be See also:

united, softening the plates in boiling See also:water or sometimes by dry heat, and then pressing them tightly together by means of heated pincers or a See also:vice. The heat softens and liquefies a superficial film of the horny material, and that with the pressure effects a perfect See also:union of the surfaces brought together. Heat and pressure are also employed to See also:mould the substance into boxes and the numerous artificial forms into which it is made up. Tortoiseshell has been a prized ornamental material from very See also:early times. It was one of the highly esteemed treasures of the Far East brought to See also:ancient See also:Rome by way of See also:Egypt, and it was eagerly sought by wealthy See also:Romans as a See also:veneer for their rich See also:furniture. In See also:modern times it is most characteristically used in the elaborate See also:inlaying of See also:cabinet-See also:work known as Buhl furniture, and in See also:combination with See also:silver for See also:toilet articles. It is also employed as a veneer for small boxes and frames. It is cut into combs, moulded into See also:snuff-boxes and other small boxes, formed into See also:knife-handles, and worked up into many other similar See also:minor articles. The plates from certain other tortoises, known commercially as turtle-See also:shell, possess a certain See also:industrial value, but they are either opaque or soft and leathery, and cannot be mistaken for tortoiseshell. A See also:close See also:imitation of tortoiseshell can be made by staining translucent horn or by varieties of celluloid.

End of Article: TORTOISESHELL

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