darXide

http://http://www.youtube.com/watch?v=trUfqGW5EHQ Have a look at the video. To his left of the guy, there's this small liquid tank. It's blue, and upon tilting, one of the immiscible liquid moves like a slow wave inside. Could you tell me what is it made of? And how could I create one myself? I just need the liquid ingredients, the mechanism isn't a problem. How is it possible to keep only one of the two liquids blue? The other seems like it's water or clear vegetable oil or something. Thanks a lot guys! <3 PS: I'd try mixing water and oil, but then either of the liquids can't be a different color. Plus, the oil would stay on top and water definitely doesn't move slowly.