Can You Microwave Cardboard Safely?

When it comes to convenience, microwaving leftovers in their cardboard takeout containers, using paper plates instead of regular plates, or reheating your pizza in its box all simplify the process. But can you microwave cardboard safely? 

Since cardboard and paper are often used as fire starters, it might seem counter-intuitive to use them as the base for heating your food in the microwave.

However, since microwaves work by vibrating the water molecules of food and drinks to cook/heat the contents, it’s generally safe.

So, can you microwave cardboard safely? In general, cardboard has a low moisture level, which makes it safe to microwave. However, you never want to microwave any cardboard that has wax or plastic coatings, metal handles or attachments, or lots of dyes and glues. 

Read on to discover why it is safe to microwave some types of cardboard, what types of cardboard shouldn’t go in the microwave, and how to microwave cardboard safely.

Can You Microwave Cardboard Safely? 

When we think of starting fires and things that are good to use to get them going, we often think of paper and cardboard, since they light up quickly and burn easily.

With that in mind, you might be wondering whether it is safe to microwave cardboard, given its flammability.

However, when comparing how microwaves warm things up to how fires are started, they are two completely different methods. To heat food in a microwave, it actually uses the water content of whatever food or liquid you are warming to create that heat. 

As the microwave heats foods up, it causes the water molecules in the food to vibrate faster and faster, which creates friction and heat that actually causes it to cook.

Since cardboard has very little moisture, there aren’t many molecules to move around, so it doesn’t get as hot as your food as quickly. That makes it safe to microwave cardboard in most instances. However, there are always exceptions to this rule. 

Always check the label. Many cardboard takeout containers or coffee cups will often say directly on them whether or not they are microwave safe. If they say “Do Not Microwave,” then that is the rule you should follow for that specific item. 

You will also want to make sure that you aren’t microwaving your cardboard on its own, since the food is required to absorb some of those microwaves and prevent combustion.

You also don’t want to leave cardboard in the microwave for ages: the shorter the time, the better. 

What Types Of Cardboard Can’t Be Microwaved?

While many types of cardboard are safe to put in the microwave, there are some coatings that can melt on your food or cause other issues in the microwave.

If you have a cardboard that has a wax or plastic coating, then you won’t want to microwave it to stay on the safe side. 

You may also not want to microwave cardboards that have a lot of dyes or glues on them, since they can leach chemicals into the food that you are heating up.

These chemicals can have adverse effects on your health. And, the whole purpose of microwaving your food in cardboard is convenience; you don’t want it to taste so bad you have to throw it away. 

If you have a cardboard container that has any metal in it, say as a handle, then you definitely do not want to put it in the microwave.

Metal and microwaves do not mix and can almost certainly result in a broken microwave at best, or a fire at worst. So always double check that there is no metal in your cardboard. 

Can You Microwave Cardboard Takeout Boxes?

One of our favorite things about going out to eat is definitely the leftovers that we get to enjoy when we get home (sometimes even that very same night). But can you microwave the cardboard takeout boxes that your food comes in? 

In general, you can microwave cardboard takeout boxes, so long as there are no metal handles, and they aren’t lined with plastic or wax, which can melt into your food. 

Most cardboard has a very low amount of moisture, so it doesn’t heat up as quickly as your food.

That low moisture level makes it safe to microwave, so long as it isn’t coated or doesn’t have any metal attachments. We never want to put anything with metal in the microwave!

Can You Microwave Cardboard Pizza Boxes? 

Leftover pizza is one of life’s most delicious pleasures. Now obviously you can’t put the entire 18-inch pizza box in the microwave, unless you have the world’s biggest microwave on hand.

But what if you have a small leftover box or you just want to use a piece of the box as a plate?

In that case, you can absolutely microwave your cardboard pizza box since they generally don’t have any plastic or wax coatings, and they don’t have any metal attachments. 

As a bonus, cardboard is porous and often doesn’t get as hot as your regular plates and bowls, so you won’t end up with a piping hot plate and cold pizza. 

Can You Microwave Cardboard Paper Plates? 

Paper plates are super convenient whether you’re having guests over or you just don’t want to do dishes after dinner. But can you microwave cardboard paper plates? 

If you have a regular cardboard paper plate without any plastic or wax coatings, then you can throw that plate right in the microwave with no worries whatsoever.

Since cardboard has a low moisture content, it doesn’t warm up nearly as quickly as the food that you are heating.

This low moisture level helps prevent it from overheating or bursting into flames in the microwave. 

Can You Microwave McDonald’s Burger Boxes?

If you weren’t able to finish your McDonald’s burger and you want to reheat it before diving back in, you might be wondering whether you can microwave the burger box it came in. 

Since McDonald’s burger boxes are made of cardboard without any metal attachments or plastic or wax coatings, they are safe for the microwave. 

Remember, double check in case the boxes change over time, but generally, a McDonald’s burger box is going to be safe to microwave. Try not to heat it for too long to be on the safe side. 

Related Questions

If you’re wondering whether you can microwave cardboard safely, then you might have a few other similar questions. We’ll answer them for you below. 

Can You Cook Pizza On Cardboard In The Oven?

When it comes to cooking or reheating pizza, you are going to want to take it out of or off of the cardboard before putting it in the oven. Even though cardboard has a fire point of around 500°F, it is still better to be safe and keep it out of the oven. 

If you want to reheat or cook your pizza in the oven, we recommend purchasing a pizza stone or a circular baking tray that has small holes in it to let the air flow through. These types of pans are going to give you the crispy, crunchy pizza crust that you’re looking for. 

Can You Microwave Tinfoil?

You should absolutely never put any tinfoil in the microwave.

The electric fields in the microwave cause currents to flow through the tinfoil (and other metals), which can make them heat up so quickly they spark and can catch on fire. Thin pieces of metal like tinfoil are especially susceptible.

You can, however, put tin foil in an air fryer, if you do so properly.

Can You Put Aluminum Takeout Containers In The Oven?

Yes, you can absolutely place your aluminum takeout containers in the oven to reheat your leftovers.

Aluminum is a great conductor and distributes heat quite evenly, so your food cooks or reheats really well when placed in aluminum containers. 

Final Thoughts

As you have learned, thanks to its low moisture levels, microwaving cardboard is generally considered safe so long as you follow a few key rules. 

Make sure that the cardboard does not have any plastic or wax coatings or too much glue or dye in the packaging.

These can melt and leach into your food, not only causing gross flavors but potentially leading to some nasty effects on your health.

You also want to microwave your cardboard for as short an amount of time as possible to be on the safe side.

If you’ve received a cardboard takeout container or coffee cup, check to see if it says whether it is microwave safe or not. If it says not to put it in the microwave, then transfer the contents to a microwave friendly plate or cup. 

You also want to make sure that your cardboard container doesn’t have any metal handles or attachments. They can heat up super quickly and spark, causing your food or the microwave to catch on fire.

This is especially true of tinfoil, since the little wrinkles in the foil reflect microwaves back and forth, creating high heat and friction, leading to sparking.

Remember not to put your cardboard in the oven unless you’re simply keeping something warm, since that dry heat is more likely to cause it to ignite.

Move any contents from your cardboard container to an oven safe baking sheet or aluminum container to reheat your food safely and evenly. 

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