mixture tamped around same, to mold this slot for placing ties; these slots should be nearly in the center of the height of block at a point near each end of block, thus making an excellent handle for the mason to grasp in placing the block as well as tying same together; the concrete that enters the slot above wall tie can be easily broken off when removing the block from molds.

These blocks can be molded in a series of sand molds, so as to take the entire contents of mixer at one pouring, and as the sand is not baked it can be used many times for this work.

CHAPTER XIV

MOLDING CONCRETE BRICK WITH SAND MOLDS

THE sand mold process is adaptable to the molding of every style of cement or concrete brick, and is invaluable to the concrete worker where but a few of a certain size of brick are demanded at once; the pattern can be placed in the flask, the mold made and the brick cast, in but a fraction of the time required to construct the wood mold for same.

As applied to all concrete work cast in sand molds, the wet sand around the work enables each brick to be perfectly cured, without the usual trouble in sprinkling them several times to properly assist the final setting of the cement.

The sand mold process permits the molding of the plain style of brick shown at (a) in Fig. 12; the pattern can be made from a block of wood of the right size or from several boards nailed together; these are the easiest used when

a number of patterns are made and attached to the cover board with enough space between each one to permit a wall of sand between each brick, as shown at (d) Fig. 12, the cover board containing your series of patterns is placed upon the bottom of a flask and the sand mixture tamped upon same, in the usual manner, when removing patterns from the sand mold; simply reverse the mold and lift up the cover board, evenly, which draws the series of brick patterns from the sand mold.

The plain brick with one surface concave, as shown at (b) Fig. 12, is easily made from wood patterns, made in the same way as employed for the style at (a), in placing upon the cover board, nail the flat surface to the board, so the concave surface is uppermost and forms the pattern imprint in the sand; the mold is made and filled with the concrete, all in one section of flask as the top edge of bricks can be smoothed with a straight-edge, resting upon each side of flask and drawn across same, thus making the filling and finishing of the concrete in the mold a very rapid operation.

The pattern for hollow brick is shown at (e) Fig. 12; the pattern consists of four strips which are the length and width of the brick, with the thickness of the lumber equal to the thickness of the brick you wish to mold; these four pieces are joined at each corner with a halved joint, made by cutting into the end of each piece half-way at a distance from end equal to the width of the strips; the four pieces are then nailed together in a square form, in the way shown at (e), and a number of these patterns made and nailed at equal distances apart to the surface of a cover board; the sand mold is then made by tamping the sand mixture upon these patterns and then when the flask is reversed, the cover board may be lifted and with it the entire series of patterns nailed to same. Care must be used in lifting the patterns so as not to disturb the core in center; this is not difficult to accomplish if the patterns have been coated several times with shellac or varnish, before making mold. The concrete is placed as for plain brick and the top leveled with a straightedge. This style of brick makes a most excel