Here we hold a magnet beneath the glass, close to the ferrofluid. We can see how the spikes form and how the spikes follow the magnetic field lines of the magnet. The stronger the magnetic field the denser and more pointy these spikes become.
Normally, fluids are not ferromagnetic, which means a magnet won’t attract them. But, when you manage to get tiny iron particles to float in a fluid without clumping together or sinking to the bottom, then you have a ferromagnetic fluid that reacts to a magnetic field, a so-called "ferrofluid". If you then place a super magnet near the ferrofluid, you can watch all sorts of weird behaviours. Ferrofluid is typically only used industrially, for example during the production of loudspeakers. However, from our online shop, you can get ferrofluid in small bottles, including a pipette so you can return it to the bottle. Now you too can conduct experiments with this fascinating fluid.