THE MANUFACTURE OF BUILDING BRICK. 227 



In hand molding, the clay is tempered quite soft. A lump more 

 than sufficient to fill the mold is taken and forced into the wooden 

 mold by the molder, who then, by means of a wire, cuts off the 

 excess of clay from the top of the mold box. The latter is then 

 turned over on the drying floor and the brick dumped out (PI. 

 XXVI, Fig. 1). With such an outfit one man is able to mold 

 about 2,500 bricks in ten hours. Hand molding is in most cases 

 confined to> small yards, where the production is small and the 

 capital invested of corresponding size. The hand-molded bricks 

 are usually more porous than the machine-molded variety. 



The soft-mud machine consists usually of an upright box of 

 wood or iron, in which there revolves a vertical shaft, bearing 

 several blades or arms. Attached to* the bottom of the shaft is 

 a curved arm, which forces the clay into the press box. The 

 molds, after being sanded, are shoved underneath the press box 

 from the rear side of the machine. Each mold has six divisions, 

 and as it comes under the press box the plunger descends and 

 forces the soft clay into* it. The filled mold is then pushed for- 

 ward automatically upon the delivery table, while an empty one 

 moves into its place. As soon as the mold is delivered its upper 

 surface is "struck" off by means of an iron scraper. Under 

 favorable conditions soft-mud machines have a capacity of about 

 40,000 brick per day of ten hours, although they rarely attain 

 this. Four men are commonly required to. tend a machine which 

 is operated by steam or horsepower. 



The molds are sometimes sanded by hand, but more frequently 

 by a machine consisting of a barrel on which the molds are 

 fastened to form the sides. Sand is then put inside and as the 

 barrel revolves on its horizontal axis, the sand falls into the 

 compartments of the molds. As soon as one mold is removed, 

 another requiring sanding is put into its place. 



The soft-mud process was the first method of molding em- 

 ployed, and is still largely used at many localities. It is adapt- 

 able to a wider range of clays than any of the others, and possesses 

 the advantage of not only producing a brick of very homo- 

 geneous structure, but one that is rarely affected by frost action. 

 Its cost is small, but the capacity is limited, as compared with a 

 good stiff-mud machine, and a large number of men are also 



