15 Surprising Facts About Your Microwave That You Should Know

Ah, the modern microwave. These nifty devices, which were first invented in the 1940s, have been wielding the power of electromagnetic radiation to heat our food for what feels like forever. Although microwaves didn't become affordable enough for home use until the 1970s, most of us now consider them an integral cooking appliance in our kitchens.

According to the U.S. Bureau of Labor Statistics, over 90% of homes in the U.S. have a microwave. They come in a range of styles and colors, from retro-fashioned looks to contemporary stainless steel designs. Yet how many of us actually understand these seemingly magical devices? It's easy to just plop your favorite frozen dinner inside, hit a few buttons, and enjoy that deliciously easy meal. But what about the machine that made it all possible?

Microwaves are a bit like that coworker you sit beside at work every day — you may think you know everything about them, but you probably don't. These under-appreciated gadgets are fascinating appliances. From tips on maximizing its full potential to capabilities you probably didn't know existed, it's time to get to know your countertop bestie a bit better.

We've all tried to microwave a quick meal in a hurry and kaboom — your food pops and splatters all over the microwave's interior. You say you'll get it later, yet as soon as that microwave door closes and the mess is out of sight, it's also out of mind.

Keeping your microwave clean and food-free isn't just a cosmetic need, it's also a sanitary one. If your microwave is not properly cared for, it can become breeding grounds for bacteria. A 2024 study found over 100 different strains of bacteria in microwave ovens, including those that cause foodborne illness. Considering this, it's best to treat your microwave's interior like any other kitchen surface and clean it regularly.

And this isn't just for sanitary purposes. In addition to bacterial concerns, leaving food in the microwave can cause burning when the spills are reheated in subsequent zappings. Of course, the best thing to do would have been to cover the food before microwaving, but that's a tip for next time.

Ever wonder how your microwave actually works? It's all due to one integral component: the magnetron. The magnetron was invented by Albert Hull, a General Electric worker, although he couldn't find any use for it at the time. It wasn't until after the war that the magnetron found its destiny in the kitchen, when a scientist noticed a magnetron had melted his candy bar. 

Each and every microwave has a magnetron inside that generates microwaves. Not to be confused with the name of the appliance itself, these microwaves are a type of electromagnetic radiation. Just like radio waves, they cannot be seen, but they are quite powerful.

Microwaves are contained within the metal lining of the appliance. They bounce off metal, but go through glass, plastic, paper and a few other items. Foods absorb these high-frequency waves, triggering the water molecules within them to vibrate. These vibrations make friction, and friction makes heat, thereby cooking the item. And it's all thanks to the magnetron.

A popular myth when it comes to microwaves is that they cook items from the inside out. Contrary to what some believe, microwaves actually operate the opposite way: from the outside in. Microwaves only permeate food from a distance of 1 to 1½ inches. In other words, the electromagnetic radiation doesn't extend to the center of chunkier items. Instead, these deeper parts are heated by conduction.

It's easy to see why many people believe that microwaves could cook food from the inside out. An oven heats food solely via convection, using the heated air to cook or warm food. That process is slower, as the food gradually climbs to the temperature of the surrounding air. By contrast, microwaves heat food much faster via electromagnetic radiation. This is the reason why many people tend to think that microwaves pass all the way through the food and heat them from the inside out.

Given their lightning speed cooking times, one might think more nutrients are destroyed by the microwave cooking process than through other means. Yet this is not the case. When you heat or cook food in a microwave, it actually retains more nutrients than if you were to utilize other methods, like boiling or oven-heating, because the cooking time is shorter.

The reality is, the longer something cooks, the more nutrient loss tends to happen. Oven-cooking, which exposes foods to high temperatures for longer periods of time, can eliminate more nutrients than if you had microwaved the same foods for a shorter amount of time. Likewise, boiling can reduce the amount of nutrients because they seep into the surrounding water.

As such, if you want to retain the most amount of vitamins and nutrients, you may want to try quick cooking methods, including grilling, roasting, steaming, sauteing, and yes, microwaving. So don't feel bad the next time you decide to employ your microwave in lieu of the oven. You might actually end up with a more nutrient-rich meal.

Not only is styrofoam terrible for the environment, but it's not great for us either. It's one of the containers that you should never reheat food in. Microwaving foods in styrofoam, also known as expanded polystyrene, can cause chemicals to seep into your food.

Styrofoam is just one trade name for expanded polystyrene or EPS, a type of plastic composed of little beads that are heated and transformed into items. It contains certain chemicals like styrene, a potential human carcinogen per the Centers for Disease Control. Although the chemicals in the container can seep into food no matter what, microwaving intensifies the process. Heat can accelerate the transfer, pushing an extra dose of harmful substances into liquids or foods.

If that thought isn't disconcerting enough, there's also logistical problems with these food containers. These containers can break down or melt, which can make them unstable for carrying foods and even pose a safety hazard for burns or other food mishaps. Be it foam-lined cups, takeout containers, or old-fashioned Cup Noodles, heating food inside these vessels should be avoided whenever possible.

Every so often, you just want to indulge in the occasional sweet treat. But baking a whole tray of cupcakes in the oven just because you want one? That seems like more work than it's worth. Here's where a curious notion comes into play: Have you considered utilizing your microwave? Baking in the microwave may sound strange, but it can be done.

You can make small desserts like mug cakes, individual-sized banana bread, or even single-serve brownies and muffins in this time-saving countertop appliance. Just find yourself a recipe for a personal-sized dessert, like our lemon mug cake or Oreo mug cake, and a microwave-safe mug. Most recipes follow a similar format. You'll mix the wet ingredients first, then stir in the dry ones, microwave for a minute or two, and let it cool. In less than five minutes, you'll have dessert waiting for you! 

Ever read the back of your microwave dinner and seen those words "let stand X minutes?" That's due to something known as carryover cooking time. This is the extra cook time, also called standing time or resting time, occurs after the microwave has ceased. And it's crucial to adhere to these recommended wait times no matter how hungry you may be.

When you microwave food, the fat, sugar, and water molecules vibrate and generates heat. Once the cook time is over, the microwave may stop, but the molecules keep producing heat, since they're still moving. Resting or standing time is important after cooking since foods can increase in temperature after the appliance stops. This phenomenon is more likely to happen in denser items like meat than it is with other items like vegetables or bread. 

Nonetheless, standing time will allow the heat to distribute to the rest of your food safely. If you're ever unsure of how long standing time should be, aim for about 20% of the whole cooking time. 

Seeing sparks? This is usually due to microwaves responding to metal materials, such as gold paint on your dinnerware. Other common culprits can include metal twist ties or a utensil that you forgot to remove from the food. If you see these tiny fireworks happening in your microwave, turn it off immediately. If stopped straight away, the microwave should be fine. When not stopped in time, arcing can burn the microwave and make it unusable. If the arcing results in holes in any of the interior walls, you will need to have the microwave replaced.

Oddly enough, metal objects and metallic paint aren't the only items that can cause arcing in the microwave. Arcing can even happen when microwaving carrots and other veggies if they were grown in soil high in iron or other metallic micronutrients. Bell peppers, kale, and green beans have also been known to provoke sparking in this countertop appliance. Hot dogs can also be a cause of arcing, resulting from additives and salt that are distributed unevenly.

While you can oftentimes simply pull out the metallic criminal that caused the arcing, like that forgotten fork or gold-lined plate, this doesn't work for food items. If arcing happens in veggies or hot dogs, or you cannot determine the source of the sparks, immediately press cancel and opt for a different cooking method. These metallic components can create a short circuit, melt plates, or even cause food to catch fire.

There are a variety of items you should never microwave, but the strangest one is nothing at all. When you run this machine with no food or liquid inside, the appliances have no water molecules to play with. This can result in the appliance overheating or create burns on the inside walls. If you run a microwave empty and catch it quickly, it shouldn't be an issue. But if the microwave operates on empty for more than five minutes, you may be in trouble.

Although microwave fires most frequently occur due to overheated food or packaging, an empty microwave can also potentially set itself aflame. Reports in the past have seen microwaves turn themselves on, usually due to power surges, and become incredibly hot. And while the Food and Drug Administration states that only some microwaves are not to be run on empty, it's better to be safe than scorch your kitchen.

Microwave preset buttons may seem like a shortcut to the perfect baked potato or buttery bowl of popcorn, but they tend to be less reliable than the instructions on the box or time given in a recipe. Tests comparing the recommended time and preset button for microwave popcorn have shown that inputting the time results in more popped kernels across several different microwave brands. Likewise, it was also found that using the baked potato preset ultimately resulted in an undercooked or overcooked spud across multiple microwave models.

Why are these buttons so unreliable? Well when it comes to items like potatoes, the microwave isn't taking into account any additional factors like the size of the item. This can result in the cook time being too long for small items, and not long enough for bigger ones. Additionally, different product manufacturers often have different recommended cook times. For example, Jolly Time Popcorn recommends a cook time between one minute and 45 seconds and three minutes, while Orville Microwave Popcorn calls for two to four minutes. And those individual-sized bags? They'll call for an even shorter time.

Most microwaves come with adjustable power settings, but few users even take advantage of this feature. But, modifying these settings can be helpful in many instances. Adjusting the power levels on your microwave can help stop certain foods from becoming too dry on their exterior as you warm the center. Because microwaves only make it into those top inch or so of food, they can overcook these outer sections and leave the center chilly.

If you lower the power level, you can allow the exterior heat to spread to the middle of the item without over-drying the outer portion. Try lowering the power setting to 50% when heating bulkier items that can't be stirred, like ultra-thick lasagna. A low setting can also prevent sauces from splattering and dairy-based liquids from curdling. Trying to soften butter? Lower the power setting to avoid flecks and splashes. As a general rule, the more delicate the item, the lower the power setting should be. 

Erupting might sound like something that only happens to volcanoes, but the event can occur in microwaves as well. Microwaved liquids, like water, can occasionally become super-heated when their temperature exceeds the boiling point. These super-heated liquids may appear still, but if an item as innocuous as a spoon is inserted, they can begin boiling rapidly. The fluid will then "erupt" and spill out of the container. Oftentimes, eruptions occur when powders like hot cocoa or instant coffee are added to the water.

Still, in theory, all you need is motion to initiate this boiling over, so removing a mug of water too soon from a microwave might result in this safety hazard. Super-heating happens more commonly if the water was microwaved in an ultra clean container, like one just removed from a dishwasher, or when heating water that was room temperature. In other instances it may occur due to super-heated hot spots developing a few inches below the water's surface.

Fortunately, there are safeguards you can take to avoid this rare occurrence. First, never heat a cup of liquid for longer than two minutes, and once finished heating, leave it for 30 seconds before combining with additions or touching the container. Stirring periodically while microwaving water, or using a container with sloped walls will also help prevent eruptions. If you're planning on adding powders or gelatin to your hot water, the easiest method of all may be simply tossing a tiny amount in before or at the halfway point.

Home appliances making weird sounds are rarely a good sign. While sizzling or popping sounds are normal, loud buzzing or high-pitched noises might mean something is wrong. When in use, it's normal for a microwave to emit a low humming noise. This simply indicates the cooling fan is in operation. A harsher buzzing, however, could indicate a clogged cooling fan, especially if this sound is louder at the back of the microwave. Meanwhile, a rattling sound could signify the fan is loose.

By contrast, a noisy humming could point to a bad or broken diode. If this is the case, the microwave won't heat items. A screeching sound might mean there's a problem with the magnetron. If your microwave is newer, this might mean the magnetron is defective. If the microwave is older, it could just signify that it's worn-out due to persistent usage.

Think you can fix these issues yourself? Don't. Several people who attempted to administer DIY repairs to their microwaves have been electrocuted, resulting in death. According to the U.S. Consumer Product Safety Commission, unplugging a microwave doesn't make it shock-proof. If the internal mechanisms malfunction, electrical shock can still occur.

If you think you can get a few more uses out of that malfunctioning microwave before replacing it with a new one, you may want to think again. When you keep using a microwave that is damaged, electromagnetic radiation might escape without you knowing. While a properly sealed microwave contains all that electromagnetic radiation within its magnetic walls, if there are cracks or gaps in the lining, they might leak out.

The FDA advises consumers not to use a microwave if the door is broken, misshapen, or doesn't close correctly, or if the microwave keeps running with the door open. In cases such as these, you'll want to opt for different cooking methods until you get yourself a new microwave. And whenever you do get that next microwave, be sure to close the door gently. Slamming the microwave door can break the safety interlock switches that prevent the appliance from running while the door is open.

They say that nothing lasts forever, and sadly, home appliances are no exception to this rule. An average microwave usually lasts around 10 years. This means the time will someday come when you need to purchase a new one. When you need a new model, consider where you want to place it before buying it, and keep both cabinet height and counter space in mind. Built-in units are more costly than countertop models and will require professional installation.

Another factor to be mindful of is wattage. Microwave wattages can range from the meager 600 watts to a hefty 1,700 watts. The more wattage, the more powerful it is. Correspondingly, prices will increase with power. Those with lower wattages will be more budget-friendly, but mean longer cooking times. They can also sometimes heat food more unevenly.

Regardless of what size or wattage you choose, be sure to care for your microwave properly to ensure it has a long life. Show your appliance some love by keeping that magical machine clean, devoid of metal, and gently closing its door after it's done its job. This way, you'll only ever need to replace your beloved microwave every decade or so.