Ivory is much esteemed for its remarkable whiteness, its polish, and beautiful grain. Dioscorides asserts, that if this substance be boiled with the root of mandrago-ras, for six hours, it may be rendered soft and flexible. By steeping small pieces of ivory in vinegar, or any other acid, they become ductile, and may be preserved in that state for a considerable time, by keeping them in common water. This hard substance may also be softened and whitened, by immersing it in a hot decoction made of red sage leaves, in double-distilled white-wine vinegar, with the addition of a little quick-lime. for removing spots, tie ivory shouId be laid in unslacked line, and a small portion of water poured on it, lest the neat be too intense, and the ivory scale, or become brittle.
Others discharge the stains by merely steeping it for some time in strong lime-water.
Ivory may be dyed green, either in a solution of copper or verdi-grease in aqua-fortis ; or by grinding together two parts of verdi-grease and one of sal ammoniac, and dissolving them in strong white-wine vinegar. Farther, by employing four ounces of aqua regia, and one ounce of sal ammoniac, a fine purple colour will be the result.
Ivory, bone, horn, and other solid parts of animals, may be stained yellow, by previously boiling them in a solution of one pound of alum in two quarts of water; then immersing them for half an hour in a liquor prepared by boiling half a pound of turmeric in a gallon of water, till it be reduced to three quarts, and afterwards plunging the coloured substance into alum water.- All bony matters may also be stained blue : they are first to be tinged with green, then dipped in a strong and hot solution of pearl ashes.- See also Bones, Tortoise-shell, and Wood.
Ivory may be prepared as a ground for miniature-painting, by cleansing the leaves or plates, and rubbing them over with the juice of garlic. This method is preferably recommended for removing its greasy quality, which prevents the colours from fixing on the ground, and is said to be more useful than either soap or ox-gall.