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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?

Adam Eberlin
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  • I have never heard of this and it kind of sound like BS to me :) but I can think of one reason it might work (maybe not significantly). A well-used wooden spoon could have salts in it which would help break-up bubbles formed during boiling. Again, I can't imagine this being effective. – Usagi Oct 24 '12 at 07:15
  • Regardless... It seems to work almost immediately every time. –  Oct 06 '14 at 21:25

2 Answers2

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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 <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.

Community
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ElendilTheTall
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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.

Alan
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