262 IVORY AND THE ELEPHANT 



the painting will not be marred by the contact of the finger- 

 tips. When mounted, the ivory sheet should never be 

 glued to a backing, but left free so that it may contract or 

 expand, for this material is exceedingly sensitive to atmos- 

 pheric changes. For this reason also the miniature should 

 be provided with a crystal securely attached to the backing 

 of pasteboard or metal so that the air be excluded. Should 

 the ivory sheet come up it may be flattened by exposure 

 to a tiny stream of steam and subsequent pressure under a 

 heavy press, the steam being applied to the back of the 

 miniature and never allowed to come in contact with the 

 painting. If this curling up occurs before painting, im- 

 mersion in water and compression in a press will be suffi- 

 cient, the ivory surface being protected by tissue paper.* 



A cheap and effective treatment by which ivory or bone that 

 has become yellow can be restored to its original whiteness 

 is to place the material requiring treatment for several days 

 in a solution of one part of chloride of lime and four parts 

 water. Ivory needs more time to whiten than does bone. 

 At the expiration of the required period the ivory or bone 

 is to be washed and allowed to dry off in a current of air.f 



Another bleaching process of ivory is to lay one pound 

 weight of ivory plates in a flat vessel and pour over them 

 five ounces of crystallized salt mixed with two pounds 

 weight of soft, river water. The ivory should remain in 

 the sodium solution for from 36 to 48 hours; this is then to 

 be decanted and the ivory washed several times with cold, 

 soft water. A solution composed of f of a pound of sodium 

 sulphate to 2 pounds of water is now to be poured over the 

 plates, which are to remain therein for five or six hours; 

 then an ounce of sodium acid diluted with 4 parts of water 



•Communication of Miss Elsie W. Southwick Clark, of Orange, N. J. 

 fH. Angerstein, "Ueber das Bleichen der Knochen und des Elfenbeins," in Mittheil. des 

 hannov. Gewerbsvereins, 1855, Heft III. 



