Ferrofluid is a wonderous substance. It’s a liquid goop that responds to magnetic fields in exciting and interesting ways. It’s actually possible to make it yourself, and it’s cheap, too! The key is to get yourself some old VHS tapes.
The trick is to separate the ferric oxide from the plastic tape inside the VHS cassette. Step one is naturally to smash open a cassette, and pull out the plastic tape from inside. The tape can then be dunked in acetone to dissolve the plastic, leaving behind the ferric oxide that once stored your cherished copy of Heat. A magnet is an easy way to collect the ferric oxide, which should then be left to dry. The powdery substance can then be blended in a ratio of 1 mL of ferric oxide to 0.333 mL of cooking oil. Poor mixing can be improved by adding a droplet of water mixed with dish detergent. You should end up with a brownish sludge that acts as a rudimentary ferrofluid.
It’s a neat bit of home science. As with most such activities, it bears noting the safety risks. Don’t leave your acetone uncovered to form a nasty flammable vapor, and keep yourself keenly aware of any fire or ignition risks. Overall though, it’s a fairly straightforward process. While the resulting material isn’t necessarily lab grade, you could potentially use it to build your own ferrofluid display!