WORKING OF IVORY 263 



must be added gradually, the mixture stirred well and the 

 vessel covered with a tight-fitting cover, and left undis- 

 turbed for 36 hours. The liquid is then to be poured off, 

 and the plates are to be rinsed in water and left to dry in the 

 air. Should the desired result not be obtained the first time, 

 the operation can be once or twice repeated.* 



A process of rendering ivory semi-transparenl and so 

 modifying its structure that when placed in hot water or 

 milk it becomes as pliant as leather, was in use in Paris in 

 the forties of the last century for certain manufactures of 

 ivory, such as artificial nipples, etc. This same, or a sim- 

 ilar process is thus described: "The articles made from 

 ordinary ivory are to be placed in a solution of phosphoric 

 acid, having a specific gravity of 1.130, and kept in this 

 solution until the ivory becomes transparent. They are 

 then to be taken out, washed with water, and dried with a 

 soft, linen cloth. They will have become soft as leather, 

 but will harden on exposure to the air; however, when placed 

 in warm water they will again become soft and pliant. "f 



Because of its greater density of structure, African ivory 

 is more resistant to the tools used in working it than is 

 Asiatic ivory, at the same time and for the same reason 

 it possesses the advantage of receiving a finer polish. A 

 slight disadvantage as compared with the softer Asiatic 

 ivory is that its density renders it less freely absorptive 

 of oil, or of the colouring matters Used in staining ivory. | 



Although it might seem that the natural hue of ivory was 

 the most beautiful from an artistic point of view, more or 

 less successful attempts have been made in the past, and 



*Prof. Dr. Artus, "Verfahren zum Bleichen des Elfenbeins," in Vierteljahrschrift fiir 

 technische Chemie, IX Jahrgang, p. 264. 



fElsner, "Mittel um Elfenbein weich und durchsichtig zu machen"; in Berliner Gew. — 

 Indust— u. Handelsblatt, Vol. XXVIII, No. 6, 1848. 



JFrancis Campin "Das Drechseln in Hols, Elfenbein, Perlmutter, etc.," Weimar, 1862, 

 p. 303. 



