lent wall as it gives a strong bond to the mortar, used in laying up the wall, which enters the hollow in center of brick, and can be made to bond or tie to that in the course below, by filling the hollow with mortar; this requires more mortar than the other style of brick but this is gained by the mortar or concrete saved in the construction of the brick.

The same idea for wood patterns, for the hollow brick, can also be applied in making the patterns for a chimney block mold as well as for small building blocks or large brick:

The ornamentation of the one face of brick with rock faced effects is easily secured by making your pattern 1⁄2" to 4" wider than the brick is to be made, when finished, the pattern has a channel or groove cut into its face the depth of this extra projection as explained in Chapter X; this molds the brick with a projecing panel upon one side, which is broken off with the aid of a pitching tool or chisel. Another way is to place the brick pattern upon the cover board resting upon its side, thus bringing the face to be decorated with rock

effect uppermost; this is thickly coated with. glue and into this spalls or small stone are imbedded to produce the effect you wish, the sand then makes a mold of these patterns to reproduce fac-similes in concrete. Where the end of brick is to have a rock face the pattern may be made 1⁄2" longer and this broken off with chisel, thus making the bearing surface of brick all the same size with the rock face projection beyond that, so that they will lay easier for the mason in the wall.

A series of patterns is shown at (f) Fig. 12; the patterns are connected to a strip of lumber to reach from one side of the large flask to the other, and these strips are held in position while making mold by resting in notches cut into the side boards of flask. The sand is tamped into mold until it is the thickness of the brick from the top and then the strips, with the patterns attached, are placed into the notches in the side boards to reach from one side of flask to the other; the sand mixture is then tamped around these patterns, thus completing the mold, when patterns are lifted. In this way a large number

of molds for brick can be made in a very short time as the flask containing molds does not have to be reversed and by having a number of molds together the entire contents of the mixer can be used in one set of molds.

This method of making the molds for concrete brick is practically as rapid as many concrete brick machines that require tamping a semi-moist mixture of concrete by hand, as the time spent in emptying the brick machine and carrying the brick away is nearly equal to the making of the sand molds, with the advantage in favor of the sand molds from the fact that the brick require no further attention in hardening or curing, and that the placing of a wet mixture of concrete is quicker and makes a stronger brick than the semi-moist concrete tamped into the hand machine.

CHAPTER XV

FACING MOLDS WITH WHITE SAND, CRUSHED GRANITE, ETC. MIXING AND PLACING CONCRETE IN SAND MOLDS

THE use of a very wet mixture of concrete permits the easy bonding of any facing mixture you may wish to use; this is placed in a different manner than for the usual style of molds. The white sand, crushed granite, marble dust, or flour, or any other facing mixture you may wish to employ, is sifted into the mold before pouring the concrete, the surface of mold being composed of wet sand the dry mixture will adhere to the surface sufficiently to hold a thin coating of it entirely over the surface of mold; the sections of flask are then placed together and the concrete poured into same.

With the sand mold made in one section of flask only, and employed as a face plate or to mold bas-relief designs the facing course may

be mixed with cement and water, if a thick coating is demanded, and plastered over the molding surface of sand mold and the balance of ordinary concrete added to same, thus insuring a perfect bond.

The dry facing mixture sifted into molds is usually ample, as it will cover the surface completely with a thin facing of the higher grade aggregate and as the wet concrete is placed behind same it bonds this dry material firmly into the work, with the added advantage that if handled with care the outside surface of the facing material will not be coated with cement, thus avoiding the labor of washing with an acid, to expose this surface, and giving the work a beautiful appearance, with all the brilliancy and effect of natural stone.

The mixing of the concrete for use in sand molds should be thoroughly done, as it is not practical to add additional moisture after the concrete is placed, which is not a practice to be recommended with any mold but often employed; if for oramental work, the sand should be well screened so as to remove all large pebbles,