Rheoscopic Fluid Fidget Toy From Shaving Foam

'Rheoscopic' fluid shows the flow, thanks to shiny particles or flakes that reflect light differently as they change orientation. In this instructable I'll show you how to make some of this fliud and package it up as a mesmerizing fidget toy.

You'll need:

1. A petri dish or sealable container
2. Shaving foam
3. Food coloring
4. A hot glue gun to seal things up
5. A small magnet to embed inside as an easy way to stir things up
6. Paper towels for the inevitable mess :)

You have several options to make the rheoscopic fluid. I like the recipe outlined in this paper:

1. Add some shaving foam to a jar or beaker
2. Add water and mix
3. Let it settle out, then decant the fluid from the bottom

You can also add mica powder to water, or make this version, which I discovered, using hydrogen peroxide and paper towels. Whichever way you make it, you can also add color to taste at this stage. If you're doing the shaving foam method, take time to scoop off any last remnants of the foam from the top as any small bubbles will spoil the look of the final thing a little.

I use an exacto knife, spun between my fingers, to slowly carve a small hole near the edge of one side of a polystyrene petri dish. Then I run a bead of hot glue around the edge of the wider of the two halves, press in the smaller half, and then run a second bead around the interface as a redundant seal. If you're buying a snow globe container or just making this in a jar, you can obviously skip this step :)

Carefully add the fluid and optionally a small magnet, tapping and tilting to get any last bubbles out. I gently press on one surface to get the fliud right up to the hole before adding a dab of hot glue to seal it up.

You're done! A second magnet on the outside lets you stir up currents, although spinning it around also works. The motion and velvety appearance is soooo satisfying and trippy - better video here. Once you make one I bet you'll be hooked - especially since even a $2 can of shaving foam and a cheap pack of disposable petri dishes gets you enough materials to make loads! Let me know if you come up with any fun variations :)