The use of the so-called "hard plaster," for the finishing of business and public buildings, is to be advised wherever the slight increase in expense can be borne. For business blocks, the saving in time will usually more than cover the extra cost, and for schools or hospitals the harder and cleaner surface is to be desired. These plasters are made, some of natural cement, and others by chemical preparation, and when dry they form a clean hard surface. The natural cement plaster is slower of setting, but of greater adhe siveness, but the chemical or patented plasters set very quickly and give good results when properly used. The cement plasters are sold as a cement only and the sand is applied when the mortar is mixed.

Fig. 241. Expanded Metal Lathing.

Fig. 241. Expanded Metal Lathing.

Fig 242. Bostwick Lath.

Fig 242. Bostwick Lath.

For use on lathing, "fibered cement" should be obtained, but for plastering on brickwork or terra cotta, cement without fiber may be used. These cements are known as Acme, Agatite, or Royal cement.

The best known of the chemically prepared plasters are King's Windsor, Adamant, and Rock plaster. These are sold with the fiber and sand all combined and ready to use, by mixing with water in the prescribed proportion. Full instructions for use are furnished by the manufacturers, and these directions should be absolutely followed, as they are the result of careful preparation and long experience. These plasters can be finished with a white coat as upon lime mortar, and this will be necessary if a white finish is desired upon the natural cement plasters, as they are gray in color, Keene's Cement, For a very hard finish for bases, dadoes, columns, etc., or for any plaster work where a polish is required, Keene's cement, an English preparation, is generally used; but some of the best grades of American manufacture are said to be as hard and of less expense than the imported cement. Keene's cement is sold in two grades, coarse and superfine, either of which will make a hard finish, but superfine should be used where a polish is to be desired.