the mold and tamped into place as the mold is filling. 

 A block made in this way sets quickly and may be 

 removed from the mold in a short time, so that fewer 

 duplicate molds are required than when a mixture 

 containing more moisture is used. 



When blocks are made by "pressing," a medium 

 mixture is used, wet enough so that the water flushes 

 to the surface when slight pressure is applied. This 

 is poured into the molds and pressure applied over 

 the entire surface, all portions of the block being com- 

 pressed equally at the same time. The advocates of 

 this method claim for it the advantage of producing 

 blocks of more uniform density than by other methods. 



When blocks are made by the "pouring method," 

 the cement is reduced to a fluid state, poured into the 

 molds, and allowed to set. As the setting requires 

 some little time there is a gradual settling to the bot- 

 tom of the heavier particles of the mixture, so that the 

 block will not be of uniform density throughout. 

 Another, and more serious objection to this method 

 from the manufacturer's point of view, is the fact that 

 so many more molds are required, owing to the slow 

 process of setting. At the same time the great flexi- 

 bility of the wet medium makes it a favorite one for 

 certain purposes, while the fact that an excess of water 

 has been used makes it unnecessary to pass the blocks 

 through the subsequent "curing" process, to which 

 blocks made by the dry process must be subjected if 

 they are to be of first-class quality. For strength and 

 durability can only be secured by the presence of suffi- 

 cient water to produce the chemical reactions resulting 



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