Using a wooden spoon to prevent pots from boiling over?
There is an excellent answer to this question on the Physics SE: https://physics.stackexchange.com/questions/31029/how-can-a-wooden-spoon-be-used-to-prevent-water-from-over-boiling

I will summarise what I think is the most cogent part here.

This does work up to a point. The bubbles formed by boiling water are filled with steam, so if anything colder than the steam (ie &lt;100°C) touches a bubble the steam will immediately condense and the bubble will collapse.

Therefore provided the surface of your spoon is cold, it will help to prevent boiling over. If it's a long boil and the spoon heats up to 100°C it will no longer work. This is why a wooden spoon is recommended: metal would heat up too quickly.