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Are You Able To Microwave Cardboard?

Have you just ordered yourself some takeaway or a tasty pizza and wondering whether you can reheat your food in the cardboard box it came in?

After all, the best thing about takeaway is not having to do any dishes, isn’t it?

Are You Able To Microwave Cardboard

If you’re anything like me, your eyes might be bigger than your stomach when you get the craving for your favorite take out joint and you’ll almost always be left with a substantial amount of food leftover for the next day (or let’s be honest, later on, that evening).

Typically, we’ll reheat our takeaway food in a microwavable plate or bowl, but it would be great to know you could simply pack up your goodies in the cardboard box it came in and pop it straight in the microwave- that way, no mess is necessary. 

If you want to heat your food in the microwave directly in the container your food comes in, you should be sure to check that it’s safe to do so. 

Can I Microwave Cardboard?

Short answer, yes you can! The cardboard that is used for food containers is usually corrugated and pure cardboard has an ignition temperature of around 425 degrees Fahrenheit.

Because of the way microwaves work, it’s incredibly unlikely that pure cardboard would catch fire in your microwave. Microwaves distribute heat throughout your food by heating the water molecules in your food.

However, you don’t know for a fact that the cardboard container you’ve received with your takeaway is pure cardboard. A lot of the time, these cardboard packages are lined with a thin plastic lining.

This lining is there to prevent the cardboard container from getting soggy when transporting your food from the restaurant to your house. 

Considering cardboard and paper products are usually used to start fires and as kindling, your first instinct would probably be that microwaving cardboard isn’t safe. However, due to the nature of how a microwave operates, it’s not really much of an issue at all. 

When food or liquid is heated up in the microwave, the water molecules inside of it begin to move at a high frequency due to the waves provided by the microwave (hence the name itself).

This energy that the vibrating water molecules provide thanks to the microwaves, heats up your food. Since cardboard doesn’t contain a high level of moisture, it’s not going to heat up as quickly as your food would. 

When Is It Ok to Microwave Cardboard?

If your cardboard clearly states on the base that it is ‘microwave safe’ or suitable for microwaves, then you can be sure that it is safe to do so. This means that the container has been explicitly tested by the manufacturer to be suitable for microwave use.

In this instance, you can be certain that you won’t cause any damage to yourself, your food, or your microwave by heating up your package with it. 

This is not to say however that all cardboard is appropriate to put in the microwave. Read on to find out what to look out for before you decide to microwave your takeaway container or other cardboard sources. 

When is it Not Safe to Put Cardboard in the Microwave?

Whilst it is usually fine to put cardboard in the microwave, you still need to be aware of a few instances when it is not recommended. 

First things first- be sure to check if your container is microwave safe.

If something does not specifically say that it is microwave safe, and has therefore been tested by the manufacturer, don’t put it in the microwave- simply transfer your food you a labeled microwave-safe plate or microwave-safe Tupperware.

Once you have checked your container is microwave safe, move onto the next steps. 

Next, try to make sure you only put your microwave on for short bursts of time. Also, be sure to not put cardboard in the microwave on its own.

It is dangerous to put it in without something to absorb the waves- something with moisture such as food. The shorter duration you use your microwave for the better. 

Cardboard containers can often come with other small amounts of plastic or metal that will not be suitable for a microwave such as a handle for a Chinese food container.

Putting metal in the microwave is a recipe for disaster and is not recommended. It can be seriously dangerous and causes sparks which can start fires very easily. So be sure to check your container thoroughly.

Also, make sure you are not leaving any metal cutlery n the container that you have forgotten about from the night before. 

Some containers are held together with glues which can leach into your food whilst being heated up, leaving not only a nasty taste but also potentially harmful chemicals too. This can also be said for any plastic coatings on the inside of your container. 

Make sure that the container you are using in your microwave is a suitable size. If your cardboard plate or box cannot spin on the central microwave plate without touching the walls or without catching and standing still, it is not suitable to be used.

If your container cannot move freely, you risk your food being cooked unevenly which can lead to unpleasant tasting food and even can lead to food poisoning, which if you’ve never had, I do not recommend to anyone.

This isn’t meant to scare you however just be aware of potential things to look out for when using the microwave!

Frequently Asked Questions

Here is a list of FAQs related to microwaving cardboard. 

Is it ok to put cardboard in the Oven?

Unlike a microwave, it’s probably not a good idea to put cardboard in the oven, even at a low temperature, a small crumb or bit of grease can cause your cardboard box to spontaneously combust, resulting in a big fire hazard at worst, or just horrible burnt food at best.

Cardboard has a combustible temperature of around 450 degrees Fahrenheit, which is higher than what you’d need to cook or warm up your cold pizza, however, the cardboard can still catch on fire regardless and is best kept away from your oven.

Your best bet is to pop your food on some oven-safe dishware or a baking tray, it might be a little bit more washing up, but will ultimately be better than having to deal with cleaning out your whole oven!

Can you microwave a Pizza Box?

As a pizza box is usually made from pure cardboard, it is safe to put in the microwave. However, pizza boxes often come with annoying stickers and leaflets attached to them to show you the latest deals and discounts. Be sure to take these off your pizza boxes.

Pizza boxes are also usually very large! If you are putting anything into the microwave, be sure it is the correct size. You want to be able to spin the plate in the microwave fully without anything getting stuck on the carousel.

If anything large does get stuck, this means your food will not be cooked evenly, resulting in both cold and burnt food at the same time- the ultimate microwave nightmare.

This still however wouldn’t lead to your cardboard box catching on fire, but it’s best to be safe and make sure whatever container you put in your microwave is a suitable size. 

Can you microwave McDonald’s Burger Boxes?

Yes, you can! From burgers to chicken nuggets and most things in between, Mcdonald’s comes in cardboard boxes for its containers. With so much choice, what do you do when you over-order and want to reheat your burger later?

As McDonald’s packaging is not lined with plastics, and simply slots together rather than using any glues, it is safe to handle food. This also makes it easier for McDonald’s staff to put together the packaging without having to mass about with any sticky bit, especially when handling food.

Because of this, it is safe to put Mcdonalds’ cardboard packaging in the microwave. However, sometimes, Mcdonald’s holds special deals such as their Monopoly scratch card deals in which case make sure to remove any stickers you find on your containers.

These stickers can leave horrible smells in your microwave and may even catch fire, though rare it’s best to check your packaging before you put it in the microwave to make sure there are no stickers or glue residue. 

Final Thoughts

Whilst not all cardboard containers are suitable for use in the microwave there are lots that are. A good rule of thumb is to simply check your container for a clear ‘microwave safe’ inscription and be sure it is free from contaminants that might interfere with your microwaves such as plastic and metal.

As long as you are careful and follow those simple guidelines there’s no reason to not take advantage of your handy cardboard containers when reheating your food, especially if you’d rather avoid any unnecessary washing up.

Jess Smith