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Even when you pick a pot that's big enough to hold the pasta water, it can still spill over. As Gizmodo describes, starch molecules from the pasta seep into the water, reinforcing the bubbles. These bubbles form a thick foam layer on top, trapping steam and eventually causing a small overflow onto your stove.
One popular trick to avoid this mess is to lay a wooden spoon across the pot. Somehow, the slender handle prevents the froth from rising too high. Of course, there’s a scientific reason behind this.
According to Simplemost, it all comes down to two of wood’s key properties: its ability to absorb water and its poor heat conductivity.
"When the bubbles come into contact with the cooler, drier wood, the starch molecules break their bond, causing the bubble to burst and release the steam inside," said Michelle Dickinson, a biomedical and materials engineer, and author of The Kitchen Science Cookbook, in an interview with Simplemost.
In simpler terms, the surface tension holding the bubbles together cannot withstand the wood’s effect; when the bubbles touching the spoon pop, they trigger others to burst as well. Since a wooden spoon is far more absorbent and heat-resistant than a metal one, it can prevent foam buildup longer than a metal utensil would.
However, even a wooden spoon can eventually become too warm and waterlogged, losing its ability to control the foam. Other strategies to prevent a boil-over include lowering the heat to just above boiling or opting for a much larger pot. Alternatively, instead of using a wooden spoon, you could always try a two-by-four across the pot.
