My coworker had a smaller version of this in his cube. His son had made it in middle school and it had been going for 10+ years. I think his was sealed with wax or something.
It's an easy experiment to reproduce and works great if you have enough time to wait around.
There are a variety of "Instructibles" for these. They're of variable quality and I have no idea how to select the instructible with most chance of sucess.
It's an easy experiment to reproduce and works great if you have enough time to wait around.