Sulphur, 1 part; yellow wax, 1 part; rosin, 1 part; the sulphur and rosin are melted, and the wax is then added. It is necessary to heat the surfaces to be united; the cement is applied while still hot, and pressure is exerted till it is cold.
Powdered gum arabic, 2 parts; finely ground white lead, 2 parts; pulverised sugar-candy, 1 part; the three substances are placed in a small bottle with a wide mouth, a little hot water is poured on them, and the whole is stirred by a stick into a homogeneous paste. The cement must be kept in a closed vessel, and a little water may be added if it becomes dry. Before use, it must be well stirred, to prevent the white lead collecting at the bottom. It is employed for joining fragments of minerals, fossils, etc.
The following metallic cement for repairing broken stone was, according to Professor Brune, of the School of Fine Arts, used in the restoration of the colonnade of the Louvre, of the Pont Neuf, and of the Conservatoire des Arts et Metiers. It consists of a powder and a liquid. The powder: 2 parts by weight of oxide of zinc, 2 of crushed limestone and 1 of crushed grit, the whole intimately mixed and ground. Ochre in suitable proportions is added as a colouring matter. The liquid: A saturated solution of zinc in commercial hydrochloric acid, to which is added a quantity by weight, of hydrochlorate of ammonia equal to one-sixth that of the dissolved zinc. This liquid is diluted with two-thirds of its bulk of water. To use the cement, 1 lb. of the powder is to be mixed with 2½ pints of the liquid. The cement hardens very quickly and is very strong.
Another cement is made by boiling slices of skim-milk cheese or curd into a gluey consistence in water, and then incorporating it with quicklime on a slab with a muller, or in a marble mortar. When this compound is applied warm to broken edges of stoneware, it unites them very firmly after it is cold.