Why Does Food Explode in the Microwave?

The Real Reason Food Explodes in the Microwave

Microwaves don’t heat food from the outside in like an oven does. They excite water molecules throughout the food more or less all at once, which means the inside can get just as hot as the outside — sometimes hotter.

Water turns to steam well below the temperature most foods reach in a microwave, and steam takes up roughly 1,700 times more space than liquid water.

If that steam has nowhere to go, pressure builds inside whatever is holding it in — a skin, a shell, a thick sauce, or a sealed container. Eventually the pressure wins, and you get a pop, a splatter, or a full-on explosion.

I’ve learned this the hard way with everything from how to microwave tomatoes to leftover mac and cheese, and the pattern is always the same: something sealed the steam in.

The Foods Most Likely to Explode

Some foods are genuinely riskier than others in the microwave, and it comes down to structure. Anything with a tight outer layer and moisture inside is a candidate.

Whole eggs in the shell are the classic example — the shell and membrane trap steam with nowhere to escape until it bursts, sometimes violently enough to damage the microwave itself.

Potatoes, tomatoes, and other thick-skinned produce work the same way on a smaller scale, which is one reason I always pierce the skin before microwaving anything round and waterlogged.

Even foods you wouldn’t expect can misbehave. Dense, moisture-heavy vegetables like how to microwave beetroot can build up surprising internal pressure if left whole and uncovered too long.

Sealed Skins, Casings, and Membranes

Sausages, hot dogs, and anything with a natural or synthetic casing are prime candidates for a microwave pop. The casing holds moisture in almost exactly the way an eggshell does.

Dumplings and dough-wrapped foods have the same issue from the inside out — the filling steams, the wrapper stretches, and if it’s sealed too tightly it can burst mid-cook. If you reheat these often, it helps to know how to microwave dumplings without the wrapper splitting.

Grapes and cherry tomatoes are smaller versions of the same problem — thin skin, high water content, fast heating.

The fix across all of these is mechanical, not magical: cut a slit, poke a few holes, or slice the food in half before it goes in.

Eggs Deserve Their Own Warning

I’ll say this plainly because it trips people up constantly: never microwave a whole egg in its shell. The shell traps steam so effectively that eggs have been known to explode with enough force to crack the microwave’s glass turntable.

Even peeled, cooked eggs aren’t fully off the hook — a hard-boiled egg yolk can develop internal steam pockets and pop when you bite into it, not just while cooking, according to food safety guidance from the U.S. Department of Agriculture.

If you want scrambled or poached eggs from the microwave, whisk the yolk first so there’s no intact pocket for steam to hide in, and never reheat a whole boiled egg without slicing it first.

Thick Sauces, Purees, and Leftovers

Explosions aren’t only about skins. Thick, starchy, or dense foods heat unevenly, and steam bubbles can get trapped below a skin that forms on top of the sauce as it heats.

Chili, tomato sauce, refried beans, and gravy are notorious for this — the surface looks calm right up until a bubble breaks through and splatters the inside of the microwave.

Dense casseroles have the same issue. If you reheat leftovers often, it’s worth learning how to reheat pasta bake and other layered dishes with a stir partway through, which lets steam escape gradually instead of all at once.

Canned foods like how to microwave baked beans can do the same thing if reheated in a sealed container rather than a loosely covered bowl.

Superheated Water Is a Separate Hazard

This one surprises people because it doesn’t look dangerous at all. Water heated in a very clean, smooth container can become superheated — hotter than its boiling point — without actually bubbling.

The U.S. Food and Drug Administration has documented cases where superheated water erupted violently the moment it was disturbed, spraying scalding water and causing burns.

Adding instant coffee, a wooden stir stick, or even bumping the cup can trigger the eruption. Letting the water sit for a minute after heating, or placing a wooden stick in the cup before microwaving, helps prevent it.

How to Prevent Microwave Explosions

Almost every microwave explosion is preventable once you understand what’s actually happening.

Pierce or score the skins of eggs (never whole in the shell), potatoes, sausages, and tomatoes before microwaving.

Cover food loosely with a microwave-safe lid or vented wrap rather than sealing it airtight — steam needs somewhere to go.

Stir sauces, soups, and dense leftovers halfway through cooking to redistribute heat and release trapped steam pockets.

Use shorter bursts at lower power for dense or high-moisture foods instead of one long blast on high.

This matters even for foods people don’t think of as risky, like how to microwave mushrooms or how to microwave broccoli — both release a surprising amount of steam if microwaved covered without a vent.

What to Do If Something Explodes

Turn off and unplug the microwave before touching anything inside — hot liquid and steam can still cause burns.

Let everything cool for a few minutes before cleaning, especially if superheated water was involved.

Wipe down the interior with warm soapy water, and check the door seal and vents for stuck-on food, which can affect how evenly the microwave heats next time.

If food debris got into the vents or the turntable motor, it’s worth having the appliance checked rather than risking arcing or a fire hazard on the next use.

Foods That Splatter but Rarely Explode

Not every messy microwave moment is a true explosion — some foods just splatter as they heat, which is annoying but far less dramatic.

Starchy foods like how to microwave mac and cheese and dishes like how to microwave lentils tend to bubble and spit rather than build the kind of pressure that causes a real pop.

A loose paper towel or vented lid handles this category easily, and it protects the interior of the microwave without trapping the steam that leads to actual bursts.