Do you know what happens when you don't clear lime and calcium build-up off an aluminum shower stall for more than 8 years? It turns into a living piece of stone that eats the chrome veneer off the frame. You have to attack it with a steam-driven chisel and some - small - amount of C4 plastique. And you end up with an interesting, um, "sculpture". Or perhaps a bas relief map of the darkside of the moon.