This mass sufficiently diluted with hot oil of turpentine furnishes an excellent cement for fractured glass and gems. Being colorless, the joint can scarcely be detected, provided the cementing has been skilfully done.
To attach gems to glass of the same color, the cement is colored with aniline colors dissolved in spirit of wine, care being had to give it the same shade as the gem and the glass.
Stick mastic cement. Melt together, at as low a temperature as possible, 10 parts of mastic and one of turpentine, and pour the mass into suitable moulds.
For use, heat the fractured surfaces of the article strongly, so that the cement on being rubbed over them melts, then press the surfaces together and continue the pressure until the cement solidifies.
Sulphur cement for porcelain. White pitch 18 parts, sulphur 28, bleached shellac 4, gum mastic 8, elemi 8, glass meal 28. Melt all together, except the glass meal and stir the latter into the melted mass.
Insoluble cement for wooden vessels. Melt together 60 parts of rosin, 20 of asphalt, and 40 of brick dust. Pour the hot mixture into the joints. This cement resists the action of lye, quick lime, sulphuric and hydrochloric acids.
RUBBER CEMENTS.
These cements are very useful, but owing to the inflammable nature of the components, great care should be taken to guard against fire while preparing them. They should never be made near a naked fire, as the benzine, carbon disulphide or chloroform used to dissolve the rubber is very volatile, and the vapor given off permeates the air until, coming near a source of light, the whole air becomes one vivid sheet of flame. Vessels which are used should be closed, and if possible put out of doors. If heat is required to assist the solvent action, use a sand or hot-water bath, but on no account bring near a fire.
Cements for glass. I. Rubber 1 part, gum mastic 12, dammar 4, chloroform 50, benzine 10.
II. Rubber 12 parts, chloroform 500, gum mastic 120.