How to Make a Mold to Pour Cast Iron

Sandcasting is the typical method of making molds for cast metals. Sand is able to withstand the intense temperatures produced by molten iron. Since the sand is washed away once the iron has cooled, there is less worry of undercuts or other structural details locking the mold and the cast together. If you are new to sandcasting, a good first project is to create an open-pour, single piece mold.

Instructions of How to Make a Mold to Pour Cast Iron

1. Screw the wood together to form a frame, like a box with no top or bottom.

2. Set the frame on a table.

3. Set a simple object, such as a toy car, onto the table within a frame. Open-pour molds require an object with a flat bottom, ideally tapered. A wooden pyramid or brick would also work, while a rubber ball would not.

4. Fill the frame with sand. It should be overflowing, with a large mound in the center.

5. Pack the sand down as tight within the frame as you can, then hit it with a block of 2-by-4 wood to further compact it.

6. Scrape any loose sand off of the top with a yardstick, smoothing the surface.

7. Flip the frame over. If the sand is properly compacted it will stay in place, but you still want to be gentle.

8. Pull the object out of the sand. You may have to glue a small stick to it so that you can pull it straight out without having to dig into the sand. It will leave an impression in the sand.

9. Dig a shallow channel leading away from the mold. You can just use your finger.

10. Run a blowtorch over the sand to dry any moisture. If the sand begins to blacken, stop torching it immediately.

Your mold is now ready to have iron poured in. Pour the iron into the channel, allowing it to flow into the mold cavity. That way if the sand divots when the iron hits it, only the channel will be damaged.