I want to make a sealed box with two immiscible fluids inside of it that can stay immiscible for a decent length of time - (months/years). The fluids will be periodically tipped back and forwards relatively slowly.
I also want the two fluids to be nice to look at and clearly distinguishable, i.e. clear and blue, red and yellow, or something more spectacular that hasn't occurred to me...
I'm wondering what the best materials would be to use. I suspect that if I just use oil and coloured water, then the colouring might slowly mix into the oil, or vice versa.
Any thoughts welcome. Thanks!