The Engineer's and Mechanics Encyclopædia: Ivory.

The Engineer's and Mechanics Encyclopædia,
comprehending practical illustrations of the machinery and processes employed in every description of manufacture of the British Empire.
With nearly Two Thousand Engravings.
By Luke Hebert, civil engineer, edifor of the History and Progress of the Steam Engines, Register of Arts and Journal of Patent Inventions, etc.
In two volumes.
London: Thomas Kelly, 17, Paternoster Row.
The tusk of the male elephant. It is an intermediate substance between bone and horn — hard, solid, white, and capable of taking a good polish. The finest, whitest, and most compact ivory comes from Ceylon, which, it is observed, keeps its colour better, and therefore bears a higher value than the ivory of Guinea. The article is chiefly consumed for the handles of knives, for ornamental utensils, instruments, cases, boxes, balls, combs, dice, slabs for miniature paintings, and an infinity of toys. The coal of ivory is also used in the arts under the denomination of ivory black. The tooth of the sea horse is aho called ivory, but from its extreme hardness it is rarely worked but for making artificial teeth, for which purpose it is admirably adapted, on account of the extremely hard steel-like white enamel which covers it. The shavings of ivory procured from the ivory turners, for domestic use, are boiled in water, in the same manner as hartshorn shavings, and form a jelly inferior to none. Any piece of ivory, scraped into shavings, will answer equally well to sending to the turners, which is not always practicable. In the manufac turing of various articles of ivory and bone, a difficulty is experienced on account of their brittleness; they are therefore softened by submitting them to the action of aquafortis for twelve hours, and subsequently, it is said, to the "juice of berries," to preserve the colour. They are. thus rendered so soft and pliant, as to take an impression from a dye. They are hardened again by immersing them in strong vinegar for four or five hours. When ivory is discoloured, it may be whitened or bleached by steeping it in a strong solution of alum. The ivory should then be covered with cloth, to prevent it from drying too quickly, which renders it liable to split.

Ivory is stained of various colours in the following manner:

Red. — Take a quarter of a pound of the cuttings of scarlet cloth, half a pound of soft soap; let the soap be well rubbed into the cloth; then put them into an earthen vessel, and pour upon them two quarts of water; afterwards, boil them for a considerable time, which will extract all the colouring matter. The cloth may then be taken from the vessel, and the coloured liquor pressed out. The ivory to be stained is now to be dipped in aquafortis, then in cold water, and from thence into the dye, whilst it is warm, which will stain it of a beautiful red.

Yellow. — Boil the ivory in a solution of one pound of alum in two quarts of water, then immerse them for half an hour in a liquid prepared by boiling half a pound of turmeric in a gallon of water, until it be reduced to three quarts, and afterwards plunge the coloured substance into alum water.

Green. — The dye hath for this colour is best made of a solution of verdigris in aqua fortis; the process, in other respects, may be the same as that described for yellow.

Blue. — Dip the ivory that has been made green into a hot and strong solution of pearl ashes, which will turn it to a fine blue.

Purple. — Dissolve one ounce of sal-ammoniac in four ounces of aqua regia, to form the dye: prepare the ivory, as in the yellow, by boiling it in a solution of alum. Ivory may be silvered by immersing a slip of ivory in a weak solution of nitrate of silver, and letting it remain till the solution has given to it a deep yellow colour; then take it out, and immerse it in a glass vessel of clear water, and thus expose it, in water, to the rays of the sun: in about three hours the ivory acquires a black colour, but the black surface, on being rubbed, soon becomes changed to a brilliant silver.

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