Can You Microwave Cardboard? Can you Microwave Pizza Boxes?

Putting your food along with cardboard in the Microwave is a very appealing option when you want to reheat your food without washing your dishes and doing extra clean up work! But, is it safe to Microwave Cardboard?

There are several things which you should never put in your Microwaves such as Plastic bags and Bottles, Styrofoam, Thermocol, Aluminium Foil and many more. If mistakenly you put these things in your Oven it can damage not only your food but also your Microwave!

So, to avoid damaging your stuff you should always know what all things you can and cannot put in Microwave. Also, take into consideration putting the wrong things in the Microwave can lead to some serious consequences.

The rise in usage of cardboard has increased crazily since the decline of disposable plastic bags and many people are confused about whether it is safe to Microwave cardboard or not?

So, the quick answer to this is that Basically it is safe to put cardboard in the Microwave but you need to take some necessary precautions. You can Microwave pure cardboard material that contains food or drinks but you need to make sure that there is no glue, ink, metal, or plastic on it.

Mostly all the food containers don’t have these types of materials along with them so it is safe to say that you can Microwave food containers. Also, make sure that there is no plastic label on that container and many have damaged their machines due to plastic labels!

Never put an empty cardboard box or container in the Microwave without any food or liquid. Cardboard is a highly flammable paper product that can catch fire if it is heated to sufficient temperature!

As I previously said that you should avoid putting materials like Plastic, Aluminium foil, and Styrofoam in your Microwave which is also quite understandable. But, when it comes to cardboard many people have different opinions and experiences.

So, after detailed research and going through many blogs I have written a detailed science-based answer to this question as I myself was very confused should I Microwave Cardboard?


Microwave Mechanism


If we want to know whether it is safe to Microwave Cardboard or not then at first we need to know the mechanism of the Microwave. Basically, a Microwave oven heats the food by generating Microwaves.

I wouldn’t bore you by telling you the scientific definition of a Microwave. You can say Microwaves are electromagnetic waves and the micro word indicates that the waves are shorter than the typical radio waves.

Microwaves heat your food by getting absorbed in it and the molecules of food start moving eventually generating heat. The food molecules themselves move and also moves the surrounding molecules. There is a built-in tube known as Magnetron in a Microwave that generates these microwaves.

Microwaves are absorbed by Plastic bags and bottles, Styrofoam, and Aluminium Foil so avoid putting these things in your Microwave oven. These microwaves will lead to the generation of heat which can cause steam explosions and damage your food as well as the Microwave.

What Happens when you Microwave Cardboard?


The decline of disposable bags and many more plastic substances has resulted in more use of cardboard. Cardboard is made up of paper and is used by several manufacturers.

Majorly, all the food and drinks delivered to your home are in cardboard boxes and containers. May it be Pizza Boxes, Coffee Cups, or Soft Drinks all are delivered in cardboard boxes.

Cardboards themselves can be of several types. Single corrugated paper, single wall corrugated, and double or triple wall corrugated. However, they are made up of the same material that is Wood Fibre.

When it comes to Microwaving cardboard never Microwave Cardboard on its own. Cardboard has a moisture content of 10-16% which is quite low. When you put the cardboard in the oven it’s moisture content starts decreasing.

If the moisture content drops pretty low it may lead to steam explosions. Depending on the surface area and time of the heating if you leave the oven on for a longer time there is a chance that the cardboard may catch fire! But, if the cardboard contains any food or drink in it the chances of it catching fire are pretty low as the moisture content in the oven is high.

So, you should never Microwave cardboard on its own. Some people are recommending putting cardboard in the Microwave for drying purpose but if you choose to do so it will require a lot of precautions as it is really dangerous!

Also Read- Does Dryer Kills Germs and Bacteria?

Can you Microwave Pizza Boxes?

Pizza box

Now, when we know that cardboards should not be Microwaved on their own let’s see if it is safe to Microwave when there’s food inside. Every time I order food online or from a restaurant it tends to become cold and there’s a need to warm it up. Usually, I warm my food in a frying pan but let’s see whether we can use a Microwave oven instead.

Using a Microwave to warm up your food has many advantages. You don’t need to wash your pan, dishes, and it is a comparatively far more fast and reliable option.

Heating your delicious food having a cardboard container in an oven is safe. This is because the microwaves generated in the oven are absorbed by food and the moisture content in the oven doesn’t get too low.

However, you should check if the cardboard is pure and doesn’t contain any kind of plastic covering or labels, or metal objects. When you put food along with cardboard in the microwave most of the microwaves are absorbed by food molecules.

Hence, we can say that it is safe to put food and drinks in a microwave for warming it up a bit. You cannot obviously cook in these cardboard containers but reheating is okay under supervision. But, you need to set the temperature and time perfectly as heating for too long at a high temperature can damage your food and oven as well.

When you shouldn’t Microwave Cardboard?

Before putting any type of cardboard in the microwave you should always check that it shouldn’t have any substance which can be hazardous. Always remove any plastic coverings and labels from the cardboards and pizza boxes. Some cardboard food containers also have wax and plastic coating on them which can be really dangerous if not removed before microwaving!

Not only that if their is any plastic or wax coating on your food container it can melt and even mix with your food. Plastic and wax melts at higher temperatures and can easily leach into your food without you noticing it. If you eat such food containing wax or plastic it can be really unhealthy and may lead to some serious problems.

You can differentiate between normal pure cardboard and wax-coated cardboard easily by just looking at its surface. The wax-coated or plastic-wrapped cardboard is more smooth and shiner than the normal cardboard. Sometimes, the plastic labels are also a big concern so I would suggest microwave only those containers which have Microwavable written on them.

Ink and glue can also sometimes be an issue. Never put cardboard having ink and glue into the Microwave as it can emit harmful fumes and can also leach into your food. Also, look for metal pins or any kind of metal substances before putting them into the microwave then can also be very hazardous.

Never put brown paper bags into the microwave as it has less moisture content and can easily catch fire. Even for cardboards, I would suggest only microwave those food containers which have written safe for the microwave!

Wrapping it all Up!

Most often you Microwave cardboard only for heating your food and drinks and very rarely anyone puts cardboard in the microwave for any other reason. You shouldn’t put Plastic bags and bottles, Styrofoam, and Aluminium Foil in the Microwave in any situation.

Cardboard on itself should never be Microwaved as it has very low moisture content and can easily catch fire. This can lead to many worse cases such as your food can catch fire and also your Microwave!

Put only those food containers and cardboards in the Microwave which have written safe for Microwave and avoid putting any other kind of cardboard. Also, check whether the cardboard doesn’t have any plastic or wax coating as it can easily mix into your food which is really unhealthy and dangerous.

You can always ask your food delivery partner whether the container is safe to Microwave or not!



I spend each darn end of the week taking a shot at home tasks and trimming down the “nectar do” list. This is where I share the majority of the undertakings I’ve done and things I’m learning.

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