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Microwaves

Is A Microwave Still Safe To Use After Microwaving Metal?

Antonio Forde
Updated: January 26, 2024
6 min read

Metals are bad for microwaves, so you have been told. If you have accidentally microwaved an errant spoon or two alongside your food, you are probably wondering if your appliance will still function as it should.

What happens if you microwaved metal? Is your microwave still safe to use?

Here’s if It’s Still Safe to Use Your Microwave After Microwaving Metal:

Damage is always possible if you leave metal in the microwave during cooking, but it is not an inevitable occurrence. Your microwave is still safe to use unless it shorted out or caught fire. At the very least, you may have to deal with a few burnt spots inside the oven compartment due to arcing.

Metals in the microwave are generally unsafe. You have to understand how microwaves work to figure out why.

A microwave has a magnetron, a powerful vacuum that produces short, high-frequency radio waves from electric current. 

This frequency is just enough to get absorbed by the molecules (for example, water and fat) within organic matter. 

When you cook or reheat food in the microwave, the waves penetrate the water molecules of the food and cause them to vibrate at very high speeds. 

The vibration creates waste heat from the outer layers of the food. Since meats and plants have conductive properties, the heat is transferred all the way through, cooking the inside. 

With inorganic materials like ceramic, glass, and plastics, radio waves are not absorbed in that frequency. Since they do not heat up in the microwave, they are the recommended cookware to use for your dishes.

In contrast, metal reflects microwave energy. This is the reason why microwave frames are made up of metal. 

As an ultra-secure metal box, your oven compartment keeps microwaves from spreading out of the appliance. These waves bounce off the walls before getting absorbed by the food.

There are actually metals that you can place in the microwave. In fact, some microwave units come with a metal rack that slides into the center. It all depends on the metal type and shape.

Flat metal sheets can be used safely in your appliance. The thicker the sheets are, the better. Since they are even and smooth, they can reflect microwaves, just like the metal oven walls can.

You can also get away with microwaving a metal spoon by accident. Spoons have round edges. As long as they do not touch the sides of the microwave, it should be okay.

However, do not make a habit of putting spoons in your appliance. You may not be as lucky the next time you do this.

During cooking, metals in the microwave will only cause trouble if they have sharp points or are very thin.

Microwaves cannot fully break through metals. What they do is cause electric charges and surface current to accumulate.

When a metal is not uniform in shape, the electromagnetic fields are concentrated on the bends or perimeters. The sharper the curves, the denser the electromagnetic field is.

This is the reason why crumpled aluminum foils are dangerous when microwaved. Cutleries with pointed edges are the same.

Compared to spoons, their edges will gather charges, which turn into sparks when leaped into space.

Meanwhile, if the metal is too thin, the microwaves pushing charges to and fro will heat it up. If it becomes too hot, it may cause a fire.

As long as the metal is flat, thick, and does not cover as much space, your microwave oven is likely safe.

In the event of arcing or sparking inside the microwave, you should carefully observe your appliance.

Sparks are voltages jumping over gaps. If metal touches the sides of the oven, it can lead to scorches in the walls. 

This should not cause significant damage to your microwave. You can easily scrub off the marks using a sponge, dry it, and it will be as good as new.

The problem is when sparks come in contact with paper towels or popcorn bags. If these materials ignite, there will be fire. 

Another possible snag is a carbon trail deep inside the appliance. If it is conductive, it may cause sparks occurring at a lower voltage. 

You should not worry so much if this happens. Microwaves approved and certified by testing bodies like UL or CSA have been tested for such errors.

As long as the magnetron works, your microwave will still function properly. It remains safe for use. 

If the appliance starts acting up or shorted out, you will know right away. You should call a technician to have it fixed.

Is It Safe to Eat Food That Was Microwaved With Metal?

Yes. Accidentally microwaving metal with your food should not hurt in any way. Your dish should be fine to consume.

Whether a spoon or cookware, the presence of metal should not cause any noticeable changes in how your food was cooked.

While the metal inside the oven compartment may have redirected the microwaves somehow, it should have no effect as far as your food is concerned.

You do not have to worry about residual radiation. The food cooked with metal is no more likely to cause your body harm than when it is cooked without the metal around.

When microwaves excite the electrical currents in metal, they only cause two problems. First, the metal will get extremely hot. Second, it can cause arcs from the metal’s pointed edges.

Arcing can actually happen even if there is no metal microwaving in your appliance. 

Compact vegetables such as carrots, spinach, and green beans contain high amounts of iron and magnesium. These minerals act like mini metals and cause sparks in the microwave.

If there is arcing, you will immediately notice it because there will be a buzzing noise and blue light dancing inside your oven cavity.

There should be enough food in your microwave to absorb all these waves, so you should be good.

As for metals releasing toxic chemicals when microwaved, you should not worry. This is a misconception.

Granted, your fears about metal toxicity on food are justified. Authorities have warned the public about cookware and utensils that may leak metal into food in the past.

For instance, some aluminum cooking pots made from scrap materials have been found to pose a health risk to people as they release significant levels of lead, arsenic, and cadmium.

Exposure to these chemicals for a long time has dire consequences, like kidney damage and a range of health effects.

However, you should know that microwaves have no effect on metals. Because the molecules present in metal items are too tightly bound, they do not get an electric charge.

Unlike with food, microwaves will not cause metals to vibrate. 

If you are unfortunate enough to leave a stainless fork, there will be pops and crackles due to arcing, but no toxins released.

Stainless steels are also incredibly hard-wearing. Even with wear and tear, they are unlikely to leak metal into your food.  

If you somehow left iron in your microwave, you are in luck. Several studies have revealed that the traces of metals you get from iron cookware or utensils are beneficial for you.

Irons are also the best possible metal for cooking as they can endure high heat for long periods. 

In the rare event of a possible metal leak, a one-time exposure should not cause irreparable damage. 

You just have to ensure that you will not microwave metal with your pre-packaged food again.

Sources:

Gizmodo

MIT

Live Strong

Written by
Antonio Forde
I'm the head-writer @ Ask The Home Geek (or, in plain English, I'm the guy writing & editing the majority of the content here). Current learning project: Korean.
Have any questions? Write us a message.
Antonio Forde
I'm the head-writer @ Ask The Home Geek (or, in plain English, I'm the guy writing & editing the majority of the content here). Current learning project: Korean.