Can You Microwave Cardboard?

Card board is probably the most common material used for packaging and shipping things in the Western World. Whether it’s food, clothing, electronics, shoes, or toys, you can almost guarantee that it’ll come in a cardboard box.

Can You Microwave Cardboard?

When it comes to food, if you are a fan of take-out, not to mention pizza, then you’ll end up with meals that are served in cardboard containers or boxes. Cardboard boxes are not only convenient for serving food; they can be conveniently tucked away in your refrigerator if you have left overs. Which brings us to the question; can you safely microwave your left-over food in a cardboard box? Surely it would save you the hassle of having to wash yet another dish, but is it something that’s recommended? Continue reading for answers to this perplexing question.

Before We Get into It, What Is Cardboard Really?

The general term cardboard is applied to a variety of hard materials of wooden origins, that’s used for making boxes, and other types of packaging. So technically, cardboard, like paper, is made from the pulp of certain trees.

Cardboard usually has a natural brown hue and is made up of corrugated material. Its structure differs from that of paper because it has many layers; usually two flat layers that are separated by a thicker wavy piece in between them.

The material has grown in popularity for packaging because of its durability and strength. While these are not necessarily key qualities looked out for in food packaging, cardboard is relatively cheap and easy to recycle which makes it popular in the food industry.

So now we know exactly what cardboard is, we can get to the meat of the matter.

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Should You Be Microwaving Cardboard and What Happens When You Do This?

Unfortunately, cardboard is a combustible material, which means that any heat applied to it, could result in a fire being started. This fact, however, does not immediately discount cardboard from being microwaved, as the material generally requires a temperature above 400°F to ignite. At the same time, given that most take-out food such as Chinese and pizza contain a lot of oil, this could further increase the likelihood of the cardboard becoming combustible.

Still, whether or not your cardboard food packaging will ignite, depends on the temperature of your microwave oven! How hot does it get? Can you control the temperature? These are crucial questions to answer before you attempt reheating food in cardboard. If your oven heats up to less than 200 degrees Celsius then it should not be a problem using a cardboard package for reheating.

Another lesser known fact about microwaving is that chemicals can leach into the foods being reheated from the packaging. This is however, more likely with recycled cardboard which sometimes contains diisobutyl Phthalate. In this case, reheating food in a recycled box could expose it to any volatile chemicals in the cardboard such as plasticizers.

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So What’s The Verdict?

It’s technically safe to put cardboard in the microwave up to 200 degrees Celsius, but, there are precautions that must be taken to ensure safety.

One important thing to note is to avoid placing foods that are highly saturated in oil in the microwave. If the box itself is saturated with oil, then avoid exposing it to heat as it could ignite easily.

Another key point is to ensure that the cardboard container does not contain metal parts. Many manufacturers use metal pins and handles to strengthen the packaging. Cardboard take-out containers from Chinese restaurants are known to contain metal parts at the edges. If your container has any metal element, no matter how small, it’s unsafe for a microwave oven. Metal in a microwave can spark easily starting a fire that can damage or destroy the appliance. Pizza boxes are usually free of this hazard.

The final thing to look out for before popping your cardboard container in the oven is whether or not it has a plastic coating on the inside. Wax or plastic coatings are used on the inside of some cardboard boxes to prevent drainage or soaking. Microwaving a container with this inner coating might not be smart as it could emit toxic fumes harmful to human health. To be safe, use your fingers to check for a slick or smooth feeling on the inside of the container.

If you’ve made your checks, and none of the aforementioned hazards are found then you’re good to go. Happy heating!