As a building material, concrete isn’t limited to only slabs. If you slightly alter the mixing ratio, you can use the same substance that created your patio or driveway to create detailed statuary, decorative pavers or beautiful multistaged fountains. Through the use of concrete molds, your stone can go far beyond the limitations placed upon working the material using traditional concrete forming tools. Successfully pouring a mold, however, requires the proper preparation, both of the mold and concrete mix. With that proper preparation, it’s just a matter of filling the mold with the concrete and then awaiting the results.
Spray the inside surface of the mold with a layer of mold release agent. The agent will prevent the concrete from sticking to the mold. It will also keep the concrete from drawing moisture from any rubber molds, which could make it grow brittle.
Lay the mold onto a flat surface strong enough to hold the weight of the poured concrete. The opening to the mold should point upwards. Secure the sides of larger molds with plywood sheets cut with a table saw to the dimensions of the mold. Brace the plywood sheets in place with rows of 2 x 4 planks joined with nails at the corners. The weight of the concrete can bow out larger molds if unsupported, distorting the shape of the molded object.
Mix the concrete in a large bucket or wheelbarrow. Use an electric drill with a paddle bit attachment to mix the concrete in the bucket, and a spade to mix larger batches of concrete in a wheelbarrow. Add water to the mix until you have achieved the consistency of pancake batter, adding concrete coloring.
Pour the concrete into the mold from a single cornet. Fill the bottom of the mold to a half-inch, then hit the sides of the mold softly to settle the concrete in the mold and release any air bubbles on the bottom. Finish filling the mold, occasionally tapping around the perimeter as you continue releasing air bubbles, preventing any voids in the concrete.
Wait 48 hours for the concrete to set. Place a board onto the top of the mold and upend it carefully so it sits with the board at the bottom. Leave larger molds as is. Remove the mold from the concrete and allow it to cure for another seven days before using.