The quantity of the substitute added varies very much, there being, for instance, many varieties of so-called red lead oil cement, which contain only about 10 per cent. of red lead.
Cement for wash basins. Finely powdered glass (sifted) 2 parts, litharge 2 parts, linseed-oil varnish 1 part.
Wet the powders slightly with the oil, heat and gradually add the rest. Do not use the basin for several days. Finely powdered glass or glass meal may be made by heating glass, throwing it in cold water, grinding the fractured pieces, and washing by stirring up in water, and allowing the finer particles to float off into a second vessel. Collect this fine powder when sufficient has settled in the vessel and sift it through a very fine sieve.
Zinc-white cement is prepared similar to putty or red-lead cement. It may, however, be made as follows: Mastic 2 parts, dammar 4 parts, sandarac 6 parts, Venetian turpentine 8 parts, turpentine 10 parts, benzole 12 parts, zinc white 14 parts.
The resins are powdered, while the Venetian turpentine, ordinary turpentine, and benzole, are put in a bottle, and then the powdered resins put in. The whole is shaken and allowed to stand for the resins to dissolve. The solution is filtered through cotton-wool and rubbed up with sufficient zinc-white to form a cement. Dilute with benzine if necessary.
Mastic cement, mastic or pierres de mastic. Under this name masses are brought into commerce which are well adapted for moulding ornaments, such as figures, columns, etc., to be exposed to the weather. They are comparatively cheap, and it is rather remarkable that they are not more generally known and used for technical purposes.
To prepare large quantities of this cement suitable mills and mixing vessels are required, as the conversion of the materials into a dust-like flour is an indispensable condition of the success of the work. The materials most generally used are fine quartz sand, finely ground calcareous sand, and varying quantities of litharge or zinc oxides, besides as small a quantity of linseed oil as possible.
The linseed oil combines with the litharge or zinc oxide to an insoluble soap, which incloses the other material and forms a mass acquiring the hardness of sandstone in thirty to fifty hours.
After converting the materials into a fine powder, the mixing is accomplished in barrels filled about three-quarters full and revolved by water-power. When a thorough mixture has been effected the pulverulent mass is placed in sheet-iron vessels and saturated with linseed oil, and then moulded at once, as it solidifies in one or two days.
French mastic. Quartz sand 300 parts, pulverized limestone 100, litharge 50, linseed oil 35.