A great merit and peculiarity of ivory, as of horn, is that it is tough and elastic, as well as of a beautiful transparent or diaphanous quality. These characteristics have, with the exception of its graining or texture, been well imitated thus far only in celluloid, which is unfortunately too expensive for very general use, and, what is worse, too liable to destruction. I, however, confidently anticipate that ere long some substance will be discovered much superior to celluloid as a substitute, and probably much cheaper and less perishable. To celluloid I may, however, add the sulphuretted preparations of caoutchouc and gutta-percha, known as vulcanite or ebonite. These are indeed hard, tough, and elastic to perfection, but very dark and opaque.
Lehner, in his work Die Imitationen, observes that imitations of ivory must be varied to suit the colour and quality of originals. This requires a study, firstly, of the adhesive or glue which is to be used. This, when colourless, is known as French gelatine, and is very expensive. In lieu thereof the experimenter may take best white Salisbury glue or gum-arabic prepared with alum-water. Secondly, the body, which may be of carbonate of magnesia, carbonate of lime, such as powdered marble, sulphuretted lime, or powdered gypsum, chalk, starch, or flour, white oxide of tin, zinc, sulphate of barytes or Chinese white, white oxide of lead. In combining, e.g., magnesia with the glue, an addition of ten per cent. of glycerine gives elasticity and a horn-like clearness. To harden artificial ivory made with glue, the objects are dipped into strong solution of alum or tannin for about four minutes. The tannin is best made from gall-apples. Objects thus made have an antique ivory, yellowish hue. Red chrome alkali may be used in solution with water instead of tannin, but it gives a stronger yellow.
According to Hyatt’s patent, artificial ivory is made by combining a syrup made of eight parts shellac and three parts of ammoniac with forty of the oxide of zinc. This is heated and subjected to pressure.
Celluloid is the best material for making artificial ivory. It is made by the combination of cellulose or vegetable fibre in the form of cotton-wool treated with acid; that is to say, gun-cotton and camphor. It is sold in thin leaves, &c., which can be softened at from 100° to 125° centigrade, so as to be moulded to any form. By infusion of colouring matter, such as oxide of zinc, cinnabar, &c., celluloid is made to resemble ivory, coral, or tortoise-shell. It has often been applied to making a perfect imitation of Florentine mosaic, and of course serves admirably to repair such work when broken.
A very strong cement for ivory, bone, or fine wood is made by boiling transparent gelatine in water to a thick mass. Add to this gum-mastic dissolved in alcohol, this solution being one-fourth, and stir into it pure white oxide of zinc till it forms a fluid like honey. This is also of itself an artificial ivory, when prepared and dried in the mass. Another can be made by combining diamond cement (vide Glass) with powdered ivory and a little glycerine. Also with the same, or very strong white glue and powdered egg-shells, which latter should have been boiled. Also white of egg, gum-arabic, a very little strong vinegar, and levigated egg-shells.
Another recipe for such mending or making of ivory and similar substances is to take soft and very white paper in pulp, combined with cotton-wool, treated with very dilute acid or strong vinegar. To this add powdered egg-shells, made into paste with a little glycerine; amalgamate this with the paper and cotton mixture as thoroughly as possible, and submit to strong pressure or rolling.
Cellulose in any form, whether made from cotton, linen, wood, or other vegetable fibrous substance, affords a basis which can be treated with dilute acid to produce a horny or parchment-like substance. A modification of this is seen in making celluloid with camphor. These modified forms of organic creation can be combined with other organic substances or minerals in great variety. Thus glycerine, and at times oil of different kinds, in such admixtures confers elasticity, or a diaphanous appearance; ivory-dust has an affinity for oil and glue; and these all combine with parchment, boiled ivory-dust, and fibrine or cellulose.
Certain marine plants, such as kelp, yield a fibrous substance which has very peculiar qualities, and which admits of ingenious combination. Certain experiments and observations convince me that there is here a vast field, as yet unexplored, in which science will yet make discoveries and afford valuable contributions to technology.
The reader who is specially interested in this subject may consult to advantage Die Verarbeitung des Hornes, Elfenbeines, Schildpatts und der Perlenmutter, &c., von Louis Edgar Andés; Vienna, A. Hartleben, price 3s.