Use casting concrete molds by applying a small amount of mold release, filling the mold with concrete, tapping it to release any air bubbles and allowing time for drying the cast. Remove the mold, and allow the cast to cure for several days.
Mold release prevents the concrete from sticking to the mold. Molds require very little of this spray product to separate from the concrete. After spraying the mold, use a clean cotton cloth to remove any excess. Mold release spray should not form runs or drips with proper application.
Use sandless concrete mix for flat molds, such as stepping stones or sundials, and concrete mix for larger items, such as the legs of a bench. Measure the water for the mix according to the label directions. The resulting mixture should be the thickness of thick pancake batter without being too runny. Add more mix if it seems too wet.
Fill the mold with mix, and use a rubber mallet to tap it and release the air bubbles. If they are left in place, these bubbles form voids in the molded concrete. Tap around any fine details or protrusions from the main body of the mold so they are full of the mix. Allow extra drying time if temperatures are below 70 degrees Fahrenheit.