In the meantime I prepared my rheoscopic fluid.
The receipt in that article that Jeremy pointed me to, works great and is so simple. One part shaving cream from a can and 20 parts (by weight) of water.
Even without food coloring it looks great in the bottle!
Another idea what to do with the stuff, is to make a base for endurance tops!
You know it can be very boring to watch those tops: The first two minutes after the start, when there is still something happening (precession, dance...)are fine. Also the last few minutes when you hope it will get past a certain time mark. But those ten (or hopefully soon more) minutes in between are plain boring!If one would have something like that vortex dome to play with while time passes that would be great. I am thinking of two concave glasses inside each other, the sealing as a spacer of about 3mm. The space in between filled with the rheoscopic fluid. Some pieces of ferromagnetic material also inside to allow for "magnetic play".