A very slight infusion of Naples yellow, to which a suspicion of brown, reduced in Chinese white, has been added, gives to the paste an old-ivory colour. The corners and outlines may be shaded in Vandyke brown.
Before attempting to glue or mastic fractured ivories, they should always be washed in the alum solution, else they will often refuse to adhere.
When there is a little addition of whiting and a little oil, very well worked into the ivory paste, and it is allowed to dry thoroughly, it may be cut or carved into any shape.
Ivory or bone when very old becomes brittle or crumbling and falls to powder, because certain organic substances dry out of it, leaving chiefly lime as their residue. When the ivories from Nineveh were brought to the British Museum the celebrated Sir Joseph Hooker suggested that they should be steeped in gelatine. This effected a perfect restoration. When a case occurs in which an ivory article, a bone, or skull is so fragile that it will not bear the slightest touch without falling to dust, it may often be saved by gently spraying on it water in which gelatine or glue has been dissolved. As the glue may be made by boiling old gloves, and as a spray can be easily improvised, it will be seen that excavators and openers of ancient tombs might by this means save thousands of curious relics which are allowed to perish. As it is certainly a species of mending or of restoration, it is in place in this work. This is especially to be desired as to skulls of the earliest ages, which are of inestimable value, of which we have so very few, and of which thousands have perished which might have been preserved in the manner which I have indicated.
Sprays for spreading perfume or medicated liquids, which can be adapted to thin liquid glue, may be had of all chemists. But we can effect the purpose better by taking a tooth-brush, or any brush of the kind, wetting, and then drawing it over a dull edge of a knife or a strip of tin. According to J. C. Wiegleb, a Frenchman in his time received a very large pension for this invention, which was applied to spraying pastels. The Romans made a spray, very imperfectly, by suddenly squeezing or throwing liquids from a sponge.
Ivory handles to knives and forks, when loose, can be best reset by first pouring in a little strong vinegar. When dry use acidulated glue. A common recipe for this purpose is the following:—
| Resin (colophonium) | 20 | parts |
| Sulphur | 5 | ” |
| Iron filings | 8 | ” |
Heat, and use while soft.
In repairing ivory it is often necessary to stain it of different colours. Most of the old works on recipes contain directions for this. In that of Ris Paquot they are given as follows:—
First prepare a mixture of copper filings, rock-alum, and Roman vitriol. Boil it, let it be for six days, then add a little rock-alum. The piece of ivory to be dyed is kept in this solution for half an-hour. To dye Red.—Boil logwood chips or cochineal in water; when hot add lead dross (cendre gravelée) about 25 grammes, keep it in the fire till the colour has taken, then add rock-alum. This is strained through linen, and the ivory to be dyed is put into this liquor. Green.—Take one quart of lye made from vine-ashes (cendre de sarment), 7 grammes of powdered verdigris, a handful of common salt, with a little alum. Boil it to one-half; as soon as it is taken from the fire place the ivory in it, and leave it till properly coloured. Blue.—Dissolve indigo and potash in water, and then mix this with a quart of vine-ash lye. Black.—Boil the ivory in the following composition:—Vinegar, 500 grammes; gall-nuts pulverised, 12 grammes; nut-shells, 12 grammes. Boil down to one-half. These are all very strong dyes, which may be used for other substances.