IVORINE. —Imitation ivory, a compound of caoutchouc, sulphur, and some white ingredi ents, such as gypsum, sulphate of baryta, oxide of zinc or pipeclay.
A good formula for making artificial ivory is as follows : White shellac zo ounces Acetate of lead 4% ounces Ivory dust 8 ounces Camphor 5 ounces These ingredients are reduced to a powder, heated and mixed, then pressed in heated moulds, of made into sheets.
Pinson's process of manufacturing ivory is one much used on the Continent. Sheets of gelatine are immersed in alumina, dissolved in acetic acid. The two combine, and when the geletine has absorbed sufficient of the alumina, the sheets are hung up to dry, and when dry, are polished.
IVORY.—Specifically, the material constituting the tusk of an elephant, but the term also includes the tusks and teeth of the hippopotamus, walrus, norwhal, wild boar, and other animals. The African ivory is preferred to any other.
Ivory can be make flexible by steeping in a solution of pure phosphoric acid, specific gravity r i3o, and leaving it in this solution until it loses their opacity. It is then washed and partially dried. It will become hard again, however, when perfectly dry, but may be softened by placing in hot water.
Photographic positives made upon ivory or upon ivorine have a very delicate appearance. These are best made by coating the ivory with a gelatine or collodio-chloride of silver printing out emulsion, and printing, toning, and fixing in the ordinary way.
In the earlier days collodion positives were made upon ivory, dyed black by boiling first in a decoction of logwood, and then in a solution of red acetate of iron ; or violet, by first boiling it for a little while with proto-chloride of tin, and then in logwood.