When water boils over the fire, it is often said that you should put a wooden spoon on it to stop the excess boiling. But why exactly does it work? To explain this grandmother’s tip, the professor of physics chemistry Physigeeks answered Vismaviedepodo’s questions on Instagram.
When you boil water, “small bubbles form, a mixture of air and water vapor,” he continues. When you cook pasta or rice, starch is added. The latter causes a “film of foam” in the broth, which is opaque enough to cause pressure underneath. When this boiling pressure is too strong, it is this foam that rises and overflows.
The role of the wooden spoon
By placing the spoon on the broth, we break the film, which kept the gas blocked belows. It can therefore escape freely, the pressure drops and it stops overflowing. Wood doesn’t do much in this operation, but we choose it for a good reason: a metal spoon would be too hot to retrieve afterwardsbecause the material conducts heat.
Little tip for you at home: this method does not work with milk which overflows because the film which forms on the top of the broth is significantly thicker, and contact with the spoon is not enough to break it, specifies the professor. The other option, to prevent the cooking water from overflowing, is to first rinse your rice, which will eliminate excess starch and limit this risk. Of course, staying next to the pan and controlling the intensity of the heat helps prevent boiling over… Like stirring continuously, preventing a layer from forming.
Source: Instagram
