To help homebuilders, concrete contractors, and cement finishers see how attractive these finishes can be and exactly how they are produced , the Portland Cement Association recently built a series of demonstration slabs and made a movie of the process. The finishes selected were exposed aggregate, a new flagstone method, dry-shake color, redwood divider strips, circle patterns, leaf impressions, and brush and float techniques. When using the exposed aggregate technique, care must be given to the selection of the aggregate. Any aggregate will do as long as it is hard, sound, and of the proper shape. To use this method: spray the stones with water as soon as the concrete arrives so that they will be damp when placed. As soon as a small area has been darbied the stones should be spread uniformly over the surface. As soon as an area has been covered evenly, the stones should be embedded completely in the surface. A patting action of rapid light taps with the darby will do best because this will start a flow a paste to the surface as the stones go down. A few light passes with a float will then return the surface to the same appearance it had following the first darbying. The time for exposing the aggregate is critical. It should be done as soon as the concrete has set sufficiently to hold the aggregate firmly and while the past can still be removed by light brushing and flooding with water. Brushing and washing should continue until the desired degree of exposure has been attained. To create a realistic flagstone finish, make the joints by troweling in prepared wooden joints which are then removed after the slab has hardened. After the slab has been screeded and darbied, it is allowed to set until ready for finishing. In this case it is necessary to begin finishing somewhat sooner than normal. The wooden joints are laid out on the slab in the desired pattern. The strips can readily be adjusted to improve the pattern by simplifying complex shapes or eliminating flags that are too small. As soon as the pattern is adjusted the wooden strips are pressed into the concrete and the surface is floated. The concrete can then be troweled for a normal gray color, or a dry-shake color can be added. The next day the curing cover can be taken off and the wooden strips removed by lifting with a patching trowel. The slab can be left with depressed joints, or the joints can be filled with a contrasting mortar. A natural gray slab with white mortar joints is very attractive. Natural gray joints look well with a colored slab.