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Can You Put Cardboard In The Microwave? Basics On Microwave Safety 


Can You Put Cardboard in the Microwave

Microwaves are some of the most common kitchen electrical appliances. Like any other appliance that involves heat and electricity, you need to be careful about what you put in a microwave to avoid a potential fire hazard.

You could use a microwave to warm anything as long you have a bowl or plate to put it in. You might order takeout, and it gets to you cold; you will use a microwave to warm it.

Most takeout food comes in boxes, and people want to shove the boxes into the microwave and warm the food. Is this safe? Let us look into what is safe to put in a microwave and what you should avoid.

Can you put cardboard in the Microwave?

Most people believe that it is terrible to put cardboard in a microwave since it might catch fire. It is, however, safe to use cardboard in a microwave for relatively short periods without risking a fire. The waves are unlikely to start a fire, but it is better to be safe than sorry.

How Does A Microwave Work?

Food has water molecules inside it; it is these molecules that are used in warming the food. The microwave oven generates microwave radiation, which makes the water molecules in the food vibrate faster.

The increased molecular movement increases friction in the food, which produces heat. This radiation could affect human tissue in the same way, and that is why the microwave ovens are sealed off completely.

If the door is broken or damaged, there would be leakage of the microwaves, and they could have harmful effects on some parts of the human body. This is why you should never use an oven with a broken door or loose paneling. 

The microwave itself does not produce heat, and that is why containers don’t get hot. If the container gets hot, it is because it got heated by the hot food in it.

Other Objects To Keep Out Of Your Microwave

Microwaves have become a kitchen essential, and knowing the correct way to use one will save you a lot of time. 

You should not put some products or objects in microwaves since they will cause a lot of damage. Here are some common foods and objects you should keep out of your microwave;

1. Bread 

This will ruin your bread but not the microwave. Microwaved bread will become moist and chewy to the point that you can’t even eat it. If this happens, you can reverse it by putting the bread in the oven for a few minutes.

2. Eggs

Avoid boiling or frying eggs in a microwave since it will damage both the eggs and microwave. If you want hard-boiled eggs, boil them over a stove. 

High temperatures might at times cause eggs to explode. This will lead to an epic mess in your microwave. If you have to use a microwave, then pierce the egg yolk before putting it in to allow for air to escape.

3. Frozen meat

Frozen meat has bacteria on it that need to be killed before you eat the meat. Heat distribution in a microwave is not even. The bacteria can spread when the heat does not equally get to all the parts of the meat.

Defrost meat in the refrigerator to get all parts of it equally safe. A microwave might warm one side and leave the other completely cold.

4. Broccoli

Most households put broccoli in the oven all the time, and nothing happens to it. This is true since it poses no actual danger to you are the microwave. It is the broccoli that is damaged.

According to a study in 2003 published in the Journal of the Science of Food and Agriculture, you should never microwave broccoli.

Microwaving destroys most of the nutrients that you should get from broccoli as compared to other cooking methods. To get all the nutrients from broccoli, gently steam it and eat it to avoid destroying the nutrients. 

5. Aluminum or Tinfoil

The inside of a microwave has shiny walls that act as mirrors that reflect the microwaves that heat your food. 

When you put tin foil or aluminum into the oven, these microwaves will get reflected onto the object, and it will burst into flames. This will undoubtedly ruin your food, and it might damage your microwave.

6. Paper bags

With the high amount of heat in the microwave, the paper bag will catch fire within a short time. Popcorn bags are made from different materials than brown paper bags. Popcorn bags can withstand the heat, but the brown paper lunch bag will catch fire.  

7. Styrofoam containers

Styrofoam is bad for microwaving since it starts to melt when it gets heated. This melting will cause a lot of chemicals to get released into your food and damage your health.

If the food gets very hot, it could even get through the container and mess up your microwave. For the sake of your health, the taste of your food, and your microwave, keep Styrofoam out.

8. Water

Water needs a way to diffuse the energy produced by the heating. Without the defusing, the water will superheat. 

At this point, the water would not have boiled, and there is a high likelihood of an upward explosion occurring when you add something like a tea bag in it.

9. Popping corn

If you need to make popcorn in the microwave, do so in a sealed container or a popcorn bag. Otherwise, the corn will get scattered all over the oven and make a big mess.

10. Monster Marshmallows

Marshmallows contain water, sugar, and air. Heat pushes out the air bubbles while the sugar caramelizes and burns. This will completely ruin the look and taste of your marshmallows.

Microwave Safety Tips

All electrical appliances need to be used with a lot of precautions to prevent fires and electric shots. You can follow some tips to ensure that you are on the safe side for both your sake and your microwave.

  • Always follow the instructions on operating procedures and usage specifications given by the manufacturer.
  • Never operate a damaged oven, especially if the door does not close correctly or if the sealing surface is damaged.
  • Use the microwave only for defrosting, cooking, and heating food since other uses might lead to a fire.
  • Use microwave-safe utensils such as glass-ceramic, heat-safe glass, china, pottery with no metal, and plastic containers made to be microwave safe. 
  • Use paper only for short heating periods. If the paper stays in the oven for too long, it might catch on fire.
  • Do not overheat liquids such as water, tea, or coffee since they may boil over after taking them out.  
  • Stir liquids halfway through heating and let the container sit in the oven for a few minutes before removing it.
  • Cover the bowl or container you use in microwaving to prevent splatter. You could use a microwave-safe lid to cover food.
  • Do not put any glass that is not microwave safe into the microwave. This might lead to an explosion or damage or the glass.
  • Please do not put metal or foil in the microwave; they will reflect the microwaves and ruin the food, the microwave, or both. They can also lead to a spark of electricity which might damage the microwave or start a fire.
  • Clean any spills as soon as they occur. If the spills dry up in the oven, they will be challenging to clean up.

Can You Put Cardboard In An Oven?

The answer to this topic is a definite no. Cardboard is highly combustible when in high temperatures. Putting it in an oven is potentially one of the riskiest things you can do in a kitchen. 

Ovens are meant to generate a lot more heat as compared to microwaves. The food cooked in ovens also takes a longer time to get ready; there will be more time for the cardboard to get heated.

The chances of a fire starting are a lot higher when an oven is involved. The food and potentially the whole house could end up in flames if the cardboard catches fire. 

It will not ignite immediately, but it will catch fire after some time. To be safe, use only oven-safe utensils for cooking in the oven.


Microwaves can become an essential asset for your kitchen if they are correctly used. A microwave will help quickly cook and warm up food and beverages or water. If you don’t follow the safety precautions, then your microwave becomes a potential fire hazard.

You can use cardboard in a microwave as long as you keep the temperature below 4000C, which is the ignition temperature for cardboard. You can use it for short cooking where the risk of a fire is minimal.

As a precaution, keep all metals, aluminum, or tin foil out of the microwave.  You should keep paper bags and styrofoam out of microwaves. Microwave safety will go a long way in keeping you and your family healthy and safe.

Jacob Lindsey

Jacob is a home remodeling guru having worked over 15 years in construction in Reno, NV, mainly focused on home renovations. He likes taking ideas from his clients and making them a reality.

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