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Black Cement (Well sifted sul- year or more)

Well sifted sul- year or more to hold water. Boards nailed phide of antimony, mixed with soluble glass together, and washed with it, make good hotand chalk (see No. 2182), gives a black mass, water tanks. Its water-resisting properties which, after solidifying, can be polished or make it useful for a variety of purposes. burnished with agate, and then possesses a 2196. Mastic Cements, or Pierre Arfine metallic lustre. tificielle. Boettger says that these cements are mixtures of 100 parts each of sand, lime- | 2202. Durable Composition for Orstone, and litharge, with 7 parts linseed oil. naments. This is frequently used, instead These ingredients, carefully mixed and well of plaster of Paris, for the ornamental parts of worked together, will have the consistency of buildings, as it is more durable, and becomes moist sand, and at first but little coherence. in time as hard as stone itself. It is of great When pressed, however, the mixture gradual- use in the execution of the decorative parts ly acquires the hardness of ordinary sand- of architecture, and also in the finishings of stone, and in six months time will emit sparks when struck with steel. The binding agents in such cements are the litharge and oil, the sand giving the body, and limestone or chalk filling up the interstices. picture frames, being a cheaper method than carving, by nearly 80 per cent. It is made as follows: 2 pounds best whitening, 1 pound glue, and 1/2 pound linseed oil are heated tegether, the composition being continually stirred until