The weekend is just around the corner, and for all those looking to spend their time on a different project or to distract their minds from the tedium of routine, we have something special: How to make a ferrofluid. The ingredients are quite safe, relatively easy to obtain, and easy to combine, although I'm sure more than one mom will want to chase us with a broom when the little ones have a giant ball of slime mixed with magnets on the dining room table…
We've seen them as artistic expression, as alternatives for cleaning up oil spills, and even as advertising tools, but one thing is certain: Ferrofluids are part of a very simple group of experiments that can be carried out at home, ideal for attracting the little ones to science, or at least for demonstrating something more complex than improvised lemon batteries (Cave Johnson sends greetings). So… how do we make a ferrofluid? Fortunately, YouTube has that covered, but the enormous flexibility in recipes is a bit intimidating. Still, the DaveHax channel published one of the simplest and probably safest combinations:
The Simple Recipe
The story begins with PVA glue. Yes, the same one we used in elementary school. In the video it's white, though personally I don't think there's any restriction on using glue of a different color. In another container, we create a borax solution. The video doesn't give specific ratios, but it's enough to dissolve a full tablespoon of this salt in water. Borax can be purchased separately; however, if that step gets complicated, you might find it as one of the main ingredients in a wide range of detergents and laundry additives. We mix the borax with the PVA glue slowly, adding a little at a time, and stirring with a spoon. This way, we'll reach a point where the glue transforms into a ball of slime, which we can knead and squish without it sticking (completely) to our hands.
I imagine that for more than one child, seeing that giant slime made of glue would be enough, but the last step is to add iron filings (if it were more liquid, they wouldn't work; in that case, ferrite powder is a good option), and make sure they're well mixed. A simple magnet will make our brand-new ferrofluid react, but the experience will be much better with a neodymium magnet. In summary: Glue, water, borax, iron filings, plenty of willingness to stir, and why not an old hard drive to take apart (!) is all you need. Last suggestion: Don't store it for long. The iron will oxidize sooner than you think..
