Can You Put Cardboard in a Microwave?


You’ve probably seen videos of people microwaving cardboard and starting fires. Is it safe? Can you heat the cardboard in the microwave? In this article, we’ll answer these questions by providing safety tips for microwaving cardboard and explaining why you should avoid using it whenever possible.

While some cardboard is safe to microwave, care is needed. Cardboard may contain wax, glue, and chemicals that may pose a safety hazard when heated. Some packages also contain metal spikes or handles that can start fires. Only microwave cardboard is declared to be microwave safe.

Can Cardboard Go in the Microwave?

The science about cardboard safety in microwaves can be confusing, and depending on the type of cardboard and the materials added, the chemicals in a cardboard can cause a fire when heated but are sometimes perfectly safe.

If you think cardboard boxes and paper are usually used as a direct and fast ignition method, you would generally think that microwaving them is unsafe. Still, because of how microwaves work, the problem isn’t as big as it might be.

Normally, food contains water molecules, and when you heat it up with microwaves, those water molecules start moving at a relatively high frequency. This concept creates friction, and friction is what heats food.

There is no need to worry when using cardboard boxes as disposable products do not contain much water. Therefore, it will not heat up faster than the rice.

Worried about the moisture absorbed by the cardboard? Steam from the top of the food is absorbed by the cardboard; Unfortunately, it couldn’t get hot enough to start the combustion.

That doesn’t mean all cardboard is safe to microwave. Consider aspects such as checking microwave safety signs and using cardboard for short periods of time before microwave heating.

Also, avoid heating the cardboard multiple times.

How Long Can You Microwave Cardboard?

Microwave the cardboard for no more than a few seconds.

Chemicals in the cardboard can heat up and cause a fire. If you see smoke or flames coming out of the cardboard, remove it from the microwave immediately.

What Types Of Cardboard Can’t Be Microwaved?

While many types of cardboard can be safely put in the microwave, there are some coatings that can melt on food or cause other problems in the microwave.

If you have a piece of cardboard with a wax or plastic coating, you don’t want to microwave it, just to be safe.

You probably don’t want to microwave cardboard that has a lot of dye or glue on it, either, because it leaches chemicals into the food you’re heating.

These chemicals will have a bad effect on your health. And the whole point of microwaving food with cardboard is convenience; You don’t want it to taste so bad, that you have to throw it away.

If you have a cardboard container with any metal in it, like a handle, then you don’t want to put it in the microwave.

Metal and microwave do not mix, at best can only lead to microwave fragmentation, and at worst may lead to a fire. So, be sure to check the cardboard carefully for metal.

What Happens if You Microwave Cardboard?

If you microwave your cardboard and it catches fire, remove it quickly from the microwave and extinguish it.

Do not put water on the fire as it may deteriorate. Instead, use a dry powder fire extinguisher or baking soda. Once the fire is out, dispose of the cardboard safely.

If you microwave the cardboard but it doesn’t catch fire, the food may not be safe.

Chemicals in cardboard are released into food when heated, which can be harmful to your health.

Things to Know about Microwaving Cardboard

Not all cartons can be heated in the microwave. If the container is microwave-safe, you must keep the following points in mind when microwaving the cardboard.

  • Check the label: If it’s a cardboard pizza box, you’ll likely find detailed instructions on the label about whether microwave heating is risky. Always check for small three-wave ICONS indicating microwave safety. The icon is a microwave symbol, please consider checking the written instructions if not available. The directions section will detail how to heat food in ovens, stoves, and microwaves on each food-safe cardboard container.
  • Check for metal: Some of the cardboard has metal marks, which are definitely not safe for microwaves. Check to make sure there are no harmful traces of aluminum foil on the package.
  • Chemicals: Soup containers, cups, and bowls with plastic layers or wax coatings should be avoided. This concept must be applied to cartons with printing ink and polystyrene foam insulation of any type. These extra ingredients can release dangerous fumes or meltdowns, which can mix potentially harmful chemicals with the food.
  • Microwave temperature: Check the Settings on the device and set the level that may be lost when heating food in a cardboard box. In general, when using cardboard to heat food, please set the microwave temperature to low power.
  • Type of food: Avoid heating foods with high water content, as heat generation and radiation are relatively slow when the box is closed. A closed box means a lot of pressure will try to escape, causing an explosion. In addition, the heated liquid may damage the integrity of the cardboard, causing it to become soggy and possibly decompose.
  • Use short pulses: If you must microwave cardboard, do so only for a short time. The longer the heating time, the greater the risk of fire.
  • 4. Monitor closely: Always keep close and monitor closely when using microwaves to heat cardboard. If you see smoke or flames coming out of the cardboard, remove it from the microwave and extinguish it immediately. Do not leave the microwave unattended while heating the cardboard.
  •  Avoid wet cardboard: Make sure the cardboard is completely dry before microwave heating. If moisture is present, it can cause a fire. Wet cardboard catches fire easily in the microwave oven. Never put wet cardboard in the microwave oven.
  •  Safe recycling: Once you’ve microwaved the cardboard, put it in the right bin for safe recycling. Be sure to follow recycling guidelines in your area.

Final Thoughts

While not all cardboard containers are microwave safe, many are. As long as you’re using a container made of microwave-safe cardboard, feel free to use it to heat up your food. Please note that sometimes it does not make sense to put cardboard in the microwave and certain precautions should be taken when doing so.

Make sure the cardboard does not have any plastic or wax coating, or that there is not much glue or dye in the packaging.

These substances can melt and leach into your food, not only causing an unpleasant taste but also potentially causing some bad effects on your health.

To be on the safe side, you also need to microwave the cardboard in the shortest possible time.

Related: Things That You Can Or Should Never Put in A Microwave

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