- The sand, known as green sand, is very fine, but other types of sand can be used if you have a design that doesn't have fine lines. Mix the sand with enough bentonite to help it keep its shape. Bentonite is a type of powdered clay and can be purchased from well drillers. Always keep your casting sand moist, and store it in a sealed container. When you are ready to use it, place it in a heat-resistant box and level the top of the sand with a trowel.
- Choose an item that you want to copy in your mold, for instance decorative plaques, masks or other flat items work well to start. Dust the item with baby powder so it won't stick to the sand. Place the item face up in the container that is half filled with sand pressing it down firmly. Pour more sand on top of the item, and tap lightly with the end of a 2-by-2 from left to right covering the entire area. Repeat the tapping, going forward and back this time. Turn the 2-by-2 on its side and scrape it across the top of the sand leveling it. Place a top on the container and flip it over so that the bottom of the item is now on the top. Carefully remove the container from the sand and smooth the area around the item. Remove the item taking care not to disturb the sand around it.
- If you don't have a dedicated area for sand casting, it is safest to do it outside. Place the mold on the ground away from any flammable objects. Melt the aluminum in a crucible that fits into a smelting furnace. Wearing heat-resistant gloves and protective eye wear, carefully pour the molten aluminum into the sand mold. When the metal cools, remove it from the sand and place the moist sand back in the container. Smooth out any rough areas of the new sand casting with a grinder and polish with a rag and polishing compound until you have the finish you want.
