Ferrofluid is a great invention. It is made from small ferromagnetic particles encased in oil. A magnetic liquid! When in the presence of a magnetic field it produces some great looking and sometimes unexpected effects.
The only downside is that is is somewhat expensive, and stains EVERYTHING permanently if not cleaned up quickly. If you think keeping iron filings off your magnets when playing around is tough, this stuff is far harder. It is almost alive, in that if you have a magnet near a container it can send a pseudopod OVER the top and flow all over the magnet and your fingers like an amoeba. Kind of creepy! :-)
The brown tint to the glass is due to the staining of the oil.
If you place the bottle on a STRONG magnet it will eventually pull the
stain mostly off the glass, but often some spots will stay and you always
have a faint stain left.
Another is that if you get ANY ferrofluid on the surface of the levitation device or the graphite it will interfere and you will need to replace those parts. Here I used plastic wrap to coat the expensive bit of graphite.
The final problem is I just can't float a magnet high enough to get enough fluid around it to show anything interesting. Have to wait for the next generation of supermagnets.
The other tray has some small ring magnets in a 2x3 array.
Each field below is produced by a pair of 1/2" magnets.
&nsbp; They are stuck together in three diffrent ways.
Can you tell which is which?