Pummel a block of clay to prepare it for sculpting. Roll the clay in your hands until it is soft and easy to work with. Keep it moist while working and cover the material when not working with it to prevent drying.
Sculpt the clay into a design you want to cast in aluminum. Start with a basic shape, such as the body, head and limbs of a person, to create the general size and proportion of the art. Later, add details to the design and smooth out any rough edges. Ensure that the clay is balanced and can stand on its own.
Allow the clay to dry completely. This will take at least two days; larger pieces will take longer. Fire your piece in a kiln following the manufacturer's directions for your type of clay. This will turn it into a sturdy ceramic sculpture.
Create a rubber skin mold of the sculpture's exterior. Paint the rubber skin liquid on the surface of the sculpture, or seek a foundry worker to do this for you. When it dries, this material will pick up each detail of the art piece. Remove the rubber mold from the ceramic sculpture.
Coat the inside of the rubber mold with melted wax. Create a 1/4-inch thick layer around the inside of the mold. Allow the wax to dry and remove the rubber mold. You will now have a hollow replica of your ceramic sculpture.
Pour an investment plaster inside the wax replica and apply it to the outside of the piece as well. This plaster, which is mixed with sand and other refractory aggregates, creates a shell around the wax mold and holds the aluminum as it takes the shape of the wax.
Put on protective gear, including leather boots and gloves, and safety goggles or a full-face shield. Wear thick cotton clothing, including a long-sleeve shirt and pants, which won't melt under the high heat.
Pour melted aluminum into the plaster mold. The hot aluminum will melt and replace the wax inside the mold.
To reveal your cast aluminum sculpture, shatter the outside of the mold with a hammer once the metal begins to harden. When the metal is completely dry, polish the aluminum to whatever texture you desire.