Using a wooden spoon to prevent pots from boiling over?

Question

Someone recently told me that placing a wooden spoon across the top of a pot will prevent boilovers.

Could somebody explain to me why this is the case?

Answer 1

There is an excellent answer to this question on the Physics SE: http://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 <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.

Answer 2

Could be the explanation is related to the chemist's trick of adding rough ceramic chips (boiling stones) to water to induce even boiling. The chips provide a high surface area and release absorbed air bubbles, which helps to nucleate the formation of bubbles of steam. A wooden spoon, being porous, might work the same way.