Can You Put Cardboard In The Microwave Is It Safe
Kitchen Gadgets, Microwave

Can You Put Cardboard In The Microwave: Is It Safe

Here comes the question: can you put cardboard in the microwave? You can microwave pure cardboard containers with meals or drink beneath supervision. However, it is now not protected to microwave cardboard containing plastic, wax, ink (unless the label says otherwise), glue, or metal. Do now not put cardboard in the microwave barring any meals or drink and keep away from overheating.

Facts About Microwaves & Cardboard

Not every cardboard box is microwaveable. Here are some considerations to make while microwaving cardboard if the container is microwave-safe.

Examining The Label Of Cardboard & Microwave

If it’s a cardboard pizza box, there’s a chance the label will include information about whether microwaving it is harmful. A little three-wave indicator signifying microwave safety should always be looked for. If the microwave icon is not present, you might want to look for textual instructions.

On each food-safe cardboard container, there is a section with instructions that will explain how to heat your meal in the oven, stove, and microwave.

Inspect The Cardboard For Metal Of Cardboard & Microwave

Some cardboard contains traces of metal, which make it unsuitable for microwave use. Verify the package to ensure that dangerous elements like aluminum foil are not present.

Chemicals  Of Cardboard & Microwave

It is best to stay away from soup bowls, mugs, and containers that have plastic or waxy coatings. Any type of styrofoam insulation and cardboard boxes with printed ink must adhere to this principle. The extra parts could melt or create hazardous vapors, contaminating your food with potentially toxic substances.

When heating food in a cardboard box, check the settings on your microwave and set them to the lowest possible setting. When using cardboard to reheat food, generally set your microwave’s temperature to the low power option.

Avoid heating foods with a lot of water since heat is produced and radiated relatively more slowly when the box is closed. An explosion will result from a lot of pressure trying to escape from a closed container. Additionally, warm liquid can endanger the strength of the cardboard material, causing it to get soggy and possibly degrade.

Microwave Warm Up Cardboard

If we desire to be aware of how microwaves have an effect on cardboard, first we have to apprehend what precisely occurs internal the device. A microwave oven works by means of producing microwaves. Sure. But what are microwaves?

Microwaves are electromagnetic waves with a wavelength between infrared radiation and radio waves. Every microwave oven has a built-in vacuum tube referred to as magnetron that’s accountable for producing microwaves at a frequency of 2450 Mhz.

How do microwaves warmness your food? They are absorbed via water, fat, and sugar molecules and as a result, these molecules begin to rotate and have interaction with different molecules as well. This molecular dance generates warmness and warms up your food, drink, and… cardboard.

Microwaves can additionally be absorbed by means of positive kinds of plastic, that’s why you need to solely put licensed plastic containers in your microwave oven.

Cardboard Interact With Microwaves

Cardboard is used in many industries and an extraordinarily vast range of merchandise are made from it: pizza boxes, espresso cups, transport boxes, take-out meals containers, pen cases, and laptop computer stands, simply to point out a few.

There are many present kinds of cardboard, such as corrugated or triple wall cardboard. However, they have one element in common: they’re all made from wooden fiber (cellulose), like paper.

Read about: Can You Put Aluminum Foil In The Microwave: What Happens – Most Nutritious Foods

Cardboard normally has a moisture content material of 9-12%. If you put it in the microwave, the moisture content material will begin to reduce and can drop to 1% relying on the time the cardboard spends in the microwave oven and its floor area.

This method once in a while can show up exceptionally fast, and if you depart the microwave on, possibilities are the cardboard receives definitely dry and catches fire. Note that this situation applies solely to these instances when you put cardboard in the microwave on its personal with no different stuff (such as meals or drink).

Therefore, do now not microwave cardboard on its personal because, beneath sure conditions, it may also lead to a fire. Anything made of cardboard is probably flammable.

How About Cardboard Boxes & Containers with Food or Drink?

Now we’ve concluded that microwaving cardboard alone is not a good idea, and let’s take a look at these situations when you just want to heat food or drink water in a cardboard container.

As I already mentioned, there are many types of cardboard containers. In general, cartons containing wood fibers and without any additional materials can usually be safely microwave heated until there is food or liquid inside.

When you reheat food or drink in a container made of cardboard, the microwaves are mainly absorbed by the water, sugar and oil molecules in the food, so the cardboard’s water content does not drop to dangerous levels.

Therefore, it is generally safe to heat food and drinks under supervision in containers made of pure cardboard (unless otherwise stated on the label). Of course, you shouldn’t cook or boil in these containers, but in most cases, reheating food is fine. Microwaving food in a cardboard box for too long does damage containers and food.

Microwaves Should Not Be Used To Heat Cardboard

Keep in mind that some cardboard food containers are coated with plastic or wax or contain these materials. They are not safe for microwaves unless otherwise labeled.

In most cases, the wax used to coat paper and cardboard containers can only be polyethylene (PE) plastic. As you know, plastics can melt or warp at higher temperatures and can seep into your food. Needless to say, it’s not healthy at all. Waxed food containers are often easy to spot: they are shinier and smoother than plain cardboard.

Ink on containers can also be a problem. While not all cardboard containers that have ink on them are dangerous, I recommend that you only put those with microwave safety labels in the microwave.

Glue is another substance that is very common in packaging. Be sure not to put any carton in the microwave with glue in it: it gives off toxic fumes that may melt and migrate to food.

Cardboard takeaway containers also sometimes contain some metal (for example, some Chinese takeaway boxes). As you probably know, you shouldn’t put anything made of metal in the microwave: it could seriously damage the equipment and even cause a fire.

Can You Put Cardboard In The Microwave: Is It Safe
Can You Put Cardboard In The Microwave: Is It Safe

In some cases, you may not be able to decide if you can microwave an item made of cardboard. If you are unsure, always use a container labeled for microwave use.

Note: Heating food in a brown paper bag in the microwave is not recommended. The heat can cause them to ignite, and the glue and ink can emit toxic fumes.

What Time Isn’t It Safe To Microwave Cardboard?

Although cardboard is generally safe in microwave ovens, you still need to pay attention to some situations that are not recommended.

First of all, be sure to check the label on the container to ensure that it is safe to heat it in a microwave oven. This will allow me to review most of the points I have listed next. If something is not specifically marked that it can be heated in a microwave oven, do not put it in the microwave oven.

Secondly, only use cardboard in the microwave oven for a relatively short time, and never use it alone. You need to put the food in the microwave oven and absorb the waves with cardboard. Although your cardboard is unlikely to catch fire, the shorter the duration, the better.

Cardboard is usually made of recycled materials. Therefore, your cardboard may contain a small amount of materials, such as metal, and microwave heating is not safe. This is why it is always important to check the label on the container.

Speaking of unsafe materials, you certainly don’t want to put containers containing metal into the microwave oven. Among these containers, the most common ones are those you usually get from Chinese takeout restaurants, and their handles are metal.

Even if there is no metal in your container, pay attention to other materials. Many cardboard containers have a waxy coating that may filter out chemicals when heated. Others stick them together with glue. Some even have ink on it, which will penetrate into food after heating.

I’m not trying to scare you with these reasons. Sometimes it’s meaningless to heat cardboard in a microwave oven, but I hope you can realize them, so you should be careful. Again, the best way is to check the package to see if it specifically says that it can be heated in a microwave oven. If so, you can go.


Determining if it is safe to microwave leftover food in a cardboard can be challenging. Cardboard containers are safe for the environment and can hold hot, fresh meals like pizza and spaghetti for a short while.

But the boundary between safe and unsafe can be hazy. Because there aren’t enough water molecules in cardboard boxes, it could take longer to cook up the food.

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