The pink flushing – restroom cistern bubbles
Harmless home, school or workplace prank involving the restroom, some colorful bubble bath and a very, very surprised prank victim.
Lock yourself in at the restroom at a poorly frequented time. Lift the cistern lid (you know, the flushing box) and fill in a cup of bubble bath plus pink or red food coloring.
Why food color? Because even the most colorful bubble bath only produces transparent or pale bubbles. You can dramatically improve the coloring effect by adding food color.
Why red or pink? Because the red chromophores (the color molecules) are the smallest and thus disperse in greater intensity, thus: deep, bright colors in your bubbles.
Put the lid back on (duh!) and occupy the cubicle next door. Setting up a camera might bring you in jail, so stay away from that one (on second thought: what the heck, the fun should give it!).
It should be great fun to hear the prank victim mumble and to guess what the repair crew will try to solve the mystery.
Share your observations here. Maybe they vary in colors?