The simple wooden spoon trick that can stop your pan boiling over—but there’s a catch

Many people remember it from their mother or grandmother: a wooden spoon laid across a pan of potatoes, pasta or porridge, supposedly stopping it from boiling over.

It always seemed a little too simple to be true.

After all, how could one wooden spoon possibly hold back a pan full of bubbling, starchy water? Yet the old trick isn't just something passed down from one kitchen to the next. There is some real science behind it.

The trick is surprisingly reliable, but it may not work quite the way you think it does. So what's actually happening inside that bubbling pan? Let's take a closer look at the simple bit of kitchen science behind a trick that has been passed down for generations.

Why some pans foam up

If you've ever boiled plain water, you've probably noticed that it can bubble away without climbing over the rim.

Add pasta, potatoes, rice, porridge or milk, however, and things can get messy very quickly.

The reason is largely down to what's in the pan. Starches from foods such as wheat, rice, potatoes and corn can get into the cooking water. Milk contains casein, a protein that can also help stabilize bubbles.

As the liquid boils, these starches and proteins can coat the bubbles, making them stronger. Instead of popping quickly, the bubbles start piling up into foam and rising towards the edge of the pan, as The Conversation explains in its look at the science.

That's why a pan of pasta water can suddenly threaten your clean stove while plain boiling water usually doesn't.

So why does the wooden spoon help?

This is where the old trick starts to make sense.

Lay a dry wooden spoon across the top of the pan, and the rising foam eventually reaches it.

Wood is porous and, at least initially, cooler than the boiling liquid. When the bubbles come into contact with the spoon, that cooler, rough surface helps disrupt them and release the steam inside.

Food scientist Michelle Dickinson explained the process to Mental Floss: when the bubbles hit the colder, dry wood, the starch structure holding them together is disrupted and the bubble bursts.

The foam can then collapse instead of continuing over the rim.

Jessica Gavin, a certified food scientist, gave Parade a similar explanation, noting that steam inside the bubbles condenses when it meets the cooler spoon, causing the bubble walls to collapse.

It doesn't stop the liquid from boiling. It simply interferes with the layer of bubbles that is trying to escape.

Why the trick doesn't last forever

There's a small detail that explains why the trick can seem more effective at some moments than others.

As the pan continues to boil, the wooden spoon heats up and becomes damp from the steam and liquid. Eventually, it is no longer the cool, dry surface that helped break the bubbles in the first place.

The Conversation's explanation notes that the spoon loses its effectiveness as it heats up and absorbs moisture.

So the spoon is better thought of as a useful buffer than something that lets you leave a pan unattended.

What works better?

The wooden spoon can buy you some breathing room, but there are simpler ways to reduce the chances of a boil-over.

Turn the heat down once the pan has reached a strong boil. You don't need the stove/induction running at full power to keep pasta or potatoes cooking.

A larger pan also gives the foam more room before it reaches the rim. Food writer and recipe developer Amelia Rampe told Parade that she uses a large pot for pasta and lowers the heat as needed.

The same basic advice appears in The Takeout's explanation of the wooden-spoon trick: controlling the heat and giving the liquid more room are more reliable ways to prevent a boil-over.

So your grandmother wasn't imagining things. The wooden spoon trick really does have some science behind it.

Just don't mistake the spoon for magic. It works because of what's happening to the bubbles.