5. Red dye may be given by imbuing the ivory first with the tin mordant, then plunging it in a bath of Brazil wood, cochineal, or a mixture of the two. Lac dye may be used with still more advan tage, to produce a scarlet tint. If the scarlet ivory be plunged for a little in a solution of potash, it will become cherry red.
6. Violet dye is given in the logwood bath to ivory previously mordanted for a short time with solution of tin. When the bath becomes exhausted, it imparts a lilach hue. Violet ivory is changed to purple-red by steeping it a little while in water containing a few drops of nitro muriatic acid.
With regard to dyeing ivory, it may in general be observed, that the colors pene trate better before the surface is polished. than afterwards. Should any dark spots appear, they may be cleared up by rub bing them with chalk ; after which the ivory should be dyed once more to pro duce perfect uniformity of shade. On taking it out of the boiling hot dye bath, it ought to be immediately plunged into cold water, to prevent the chance of fis sures being caused by the heat.
Madame Bouvier(of Paris) adopts the following process (patented) for working in plastic ivory. Take the waste turnings of ivory, bone, horn, &c., and steep them in a waste acid solution. Nearly all the acids will serve for this purpose, but the following are preferable : muriatic, nitric, tartaric, acetic, citric, and oxalic, also Phosphate of lime. The solution is
placed in a water bath at a temperatne of 35° to C., to 105° Fahr.,) in order to obtain complete liquefaction. It is then passed through fine muslin, and about one fourth the quantity of ivory gelatine is next added to absorb the sol vent. When the paste is well prepared, the excess of liquid, and any foreign gases, are removed by means of the air pump : it thus become homogeneous, membranous, and very close. In this state it would be difficult to run it for use ; for which purpose it must be dis solved in copal or lac varnish, and in this state it may be run into moulds. When the paste is in the moulds, it may be made to undergo pressure, to expel the air, and prevent the formation of air bubbles in the interior. Coloring matters may be added to the paste.
M. Charriere of Paris renders the ivory which be works into shapes, flexible by steeping it in hydrochloric acid. Either strong or diluted with water, the ivory becomes flexible, elastic, and yellow. As it dries it becomes hard again. The flexibility is however restored by wetting the ivory with a piece of linen.
Ivory Black is made by exposing ivory and bone-shavings in an iron cylinder, at a red heat, allowing the effluvia to rise through a pipe. It does not differ from bone Mack, being carbon in a very fine state.