How to Mix Sand for Casting Aluminum

By Karren Doll Tolliver
Metal scraps, sand casting
vieux métaux 02 image by Hubert Isselée from

In casting aluminum objects, molten aluminum is poured into a mold. One of the techniques for making an aluminum mold is called sand casting. It involves mixing fine sand, some clay, and a small amount of water to make the mixture cohesive. This mixture is called green sand because it is moist, not because it is actually green. The green sand is tamped into a box with a hollow mold shape embedded into it. Molten aluminum is poured into the hollow and allowed to cool. After cooling, the sand is dislodged and the molded aluminum piece is removed.

Step 1

Sift the sand through the wire mesh into the plastic pan.

Step 2

Add the water gradually to the sand. Mix the sand and water thoroughly with your hands and the trowel until the water is distributed evenly throughout.

Step 3

Mix in bentonite powder gradually using your hands and the trowel.

Step 4

Mull the green sand at least three times. Mulling is stomping on the mixture then fluffing it with the trowel. It is very important that the bentonite is evenly distributed throughout the sand. The consistency should be such that, when you grasp a handful firmly in your fist, it makes a solid clump. If you break the clump, there should be a clean break. If it crumbles, add more clay.

Step 5

Experiment with different percentages of the ingredients to find out which works best for your purposes.