Lumptop
Colin sent in this how-to on making your own Ferrofluid – “Ferrofluids are a stable (meaning inseparable) suspension of nanometer sized solid magnetic particles in a carrier fluid. The particles are coated with a surfactant; a chemical which prevents the particles from clumping together and forming a solid mass. The most common type of ferrofluid, presented here, is an oil based fluid consisting of magnetite as the magnetic solid, and oleic acid as the surfactant. The final component is a carrier fluid, which suspends the particles; in this experiment the carrier will be kerosene.
– [via] Link.

Related:
Sci-Spot (lots of goodness) – Link.