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Can You Microwave Cardboard? (And What to Watch for When You Do)

Can You Microwave Cardboard? (And What to Watch for When You Do)

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Just down the street from us, we have a Chinese restaurant that has really good takeout food. If your local place is anything like ours, they give you about three times as much food as you need for a meal. As a result, we always have leftovers (well, almost always…).

We typically reheat our leftovers by putting them on a microwave safe plate or paper plate. But, it sure would be nice if we could simply reheat our food right in the containers that they came in, especially when taking it with us to work the next day.

When it comes to reheating leftovers, or even warming up takeout food that’s gotten to be a bit too cold by the time you got it home, does it make sense to put in in the microwave right in its container?

In this article, you’ll find out whether or not it’s safe to microwave food in cardboard containers, as well as the potential issues you might run into when doing so.

Can You Put Cardboard in the Microwave?

Pizza on Paper Plate

While it might not seem like a good idea on the surface, just like it’s generally safe to microwave paper plates, you can typically microwave cardboard without any issues.

Considering that paper and cardboard are typically used as a quick and easy way to start fires, you might think this isn’t safe. However, due to the nature of how a microwave operates, it’s not as big of an issue as it seems.

When foods or liquids are heated in the microwave, the water molecules inside of them begin to move at a high frequency. This is what causes them to heat up. Since cardboard doesn’t contain high amounts of moisture, it doesn’t warm up as quickly as food does.

Even if your cardboard takes on some of the moisture from the food on top of it in the microwave, it is still unlikely to reach temperatures high enough to cause combustion, assuming you’re using your microwave in a typical manner.

That’s not to say that all cardboard is safe in the microwave or that it can’t catch fire. As you’ll see below, there are several points to consider before microwaving cardboard.

When Isn’t It Safe to Microwave Cardboard?

While cardboard in general is safe in the microwave, you still need to be aware of some instances where it’s not recommended.

First, always check the labeling on your container to make sure it’s safe to microwave. That will check the boxes on most of the rest of the points I’m going to list. If something isn’t specifically labeled as being microwave safe, don’t put it in the microwave.

Next, only use cardboard in the microwave for relatively short periods of time, and never on its own. You need food in the microwave with the cardboard to absorb the waves, and although your cardboard is unlikely to catch fire, the shorter the duration, the better.

Cardboard is often made of recycled materials. As a result, your cardboard might contain small amounts of materials, such as metal, that aren’t safe to microwave. This is why it’s always important to check the label on your container.

Chinese Takeout Box

Speaking of materials that aren’t safe, you definitely don’t want to put containers that contain metal into your microwave. The most common type of container in this category would be the ones that you typically get from a Chinese takeout restaurant where the handles are made of metal.

Even if your container doesn’t contain metal, there are other materials to watch for as well. Many cardboard containers have a waxy coating that may leach chemicals when heated. Others contain glue to hold them together. Some even have ink printed on them, that again could leach into your food when heated.

I’m not trying to scare you with all of these reasons that it sometimes doesn’t make sense to microwave cardboard, but I want you to be aware of them so you proceed with caution. Again, the best thing to do is to check the packaging to see if it specifically says that it’s microwave safe. If it does, you’re good to go.

Final Thoughts

While not all cardboard containers are microwave safe, plenty of them are. As long as you’re using a container made with microwave-safe cardboard, feel free to use it to reheat your food.

Just be aware that there are times where it doesn’t make sense to put cardboard in the microwave, and certain precautions should be taken when you do. Microwaving food on cardboard provides a cheap and easy alternative to reusable plates when your food comes in containers, so why not take advantage of it?

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