How to Use Magnets to Make Fluids Into Solids

Find iron ore filings. Try a number of methods of acquiring ore, including purchasing them at a toy store or hardware store. You may also empty the iron filings out of a magnetic sketch pad. Iron filings can also be found in sand at the beach or in a sand box; retrieve iron ore samples from the sand by putting magnets in a clear plastic bag and dragging the bag through the sand. The iron ore in the sand will stick to the magnets. If necessary, crush too-large iron ore filings with a spoon.

Mix about 25 parts by weight corn oil with about 100 parts iron ore in a small, clear container. With the proper-sized container, the ore should appear to fill about one-third of the container. Stir with a plastic or wooden stirring stick (iron filings will stick to a magnetic stirring stick). Stir until the substance turns into a thin, black paste similar in consistency to maple syrup.

Use the most powerful magnet at your disposal; refrigerator magnets will often be too weak for this experiment. Place the magnet on one side. The magnetorheological fluid will be attracted to the magnet-side of the container. Pour the excess fluid into a separate cup. Only the magnetorheological fluid should remain in the original container.

Remove the magnet. Stir the fluid with the stirring stick and notice how the consistency of the substance has changed to resemble wet sand. Place the magnet against the side and notice how the fluid hardens again.