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Is it safe to microwave food in cardboard?

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Do you have leftover pizza or takeout lunch from yesterday that you are looking to heat up? To freshen up day old food, the microwave is everyone’s go-to solution for convenience and speed. 

If you don’t have access to microwave-safe dishes, you may wonder if it is ok to microwave food in the original package. 

Is it safe to microwave food in cardboard? Yes and no, without precaution it can be dangerous to microwave food in cardboard. It can spark a fire or trap moisture inside that makes your food go bad. 

Always check for a microwave-safe symbol on the box before using it in moderation.

Generally speaking, reheating food demands microwave-safe dish ware. However, the experience could be expedited if we reheat the meal using the packaging container. 

Just imagine reheating food right in its package and take it with you the following day. It would be great, right? Well, there are several types of items you can employ when microwaving food. 

In this article, we will be focusing on whether it is safe to microwave cardboard and how safe it is to have food on cardboard while heating. Answered below are frequently asked questions about microwaving food on cardboard and the risks associated with the procedure.

Can cardboard go in the microwave?

The science about the safety of cardboard in the microwave can be confusing. This is because many experts see it as both a good and bad idea. 

The basis for the good idea stands that since paper plates are safe to microwave, cardboard can be microwaved without any problem. After all, they are both paper based goods.

If you consider that cardboard boxes and paper are normally employed as straightforward and quick ways to initiate fire, you typically must think microwaving them is unsafe. Notwithstanding, due to the operational concept of the microwave, the problem is not as serious as perceived.

Usually, food contains water molecules and when you microwave, these water molecules start moving at a relatively high frequency. This concept generates friction which is what makes the food heat up. 

No need to worry when using cardboard boxes because the disposable product does not possess high water amount. Thus, it will not warm up faster than the meal.

Worried about the moisture content absorbed by the cardboard? The steam on top of the food is absorbed by the cardboard; unfortunately, it will not achieve high enough temperatures to initiate combustion.

This does not mean all cardboard is safe to go into the microwave. Consider some aspects prior to microwaving cardboard, such as checking for the microwave-safe symbol and using cardboard for a short time. 

In addition, avoid heating the cardboard more than once.

Can you reheat food in a cardboard box?

Yes, you can reheat food in a cardboard box, however you must do it in moderation. This means that reheating has to be done for a limited time. 

Prolonged heating can lead to the cardboard box lighting on fire because it is a relatively fast conductor of fire, hence it can catch fire easily. Normally, cardboard or corrugated board is a combustible material and will initiate fire when open flame and/or spark are exposed.

Despite that, the microwave appliance is accustomed to working at lower heat levels that the ignition point of cardboard, therefore the issue of cardboard burning while reheated food isn’t a major threat. 

Additionally, pure pulp and wood fiber are employed to make cardboard boxes, adding to the ideal nature for microwaving food.

Alternatively, cardboard can possess little metal compounds to ensure the pieces are intact to avoid water leakage. In such scenarios, heating cardboard boxes can be harmful. 

The rule of thumb is to avoid prolonged heating of food in the cardboard box. Note that cardboard boxes contain up to 12% moisture level, therefore when heated the water level will start dropping. 

In this case, the level drops to 1% and below. If the pulp or fiber dries too much, the result makes it easy to catch fire.

Can you put a cardboard pizza box in the microwave?

Corrugated board or cardboard is a sensitive combustible material that ought to be monitored when exposed to open flames and sparks. Moreover, the cardboard can ignite at 427 degrees Celsius. 

For this reason, you might be wondering if it is safe to put a cardboard pizza box in the microwave or it will just burn your house down.

Cardboard pizza boxes are designed for delivery purposes, however some traits make them convenient for putting into the microwave to reheat. Such characteristics include durability for stacking, retain warmth, resisting up to 80 degrees Celsius, and preventing pizza crust from drying out.

Keep in mind that different materials have unique functions and will always respond depending on scientific principles. By now, you have learned that cardboard pizza box is basically heat resistant and tailored with a special purpose. 

Despite these traits, not all cardboard pizza boxes are ideal for microwaving.

The main issue with some cardboard pizza boxes is that they have extra built-in functionality. The coating inside is aluminum foil, hardened wax or leak resistant plastic, which is unsafe for microwaving. 

The best idea is to read the manufacturer’s information and note the options that can withstand temperature associated with heating food in a microwave.

Things to know about microwaving cardboard

Not all cardboard boxes can be microwaved. If the container is microwave-safe, here are several things you must keep in mind when microwaving cardboard.

  • Checking the label: If it is a cardboard pizza box, there is a chance that you will find the label with instruction details about if it is risky microwaving it. Always check for a small three wave icon indicating microwave safety. The icon is a microwave symbol and if it is not available, consider checking for written instructions.
    The direction section will give you details about heating your meal in the oven, stove, and microwave on each food safe cardboard container.
  • Check for metal: Some cardboard comes with traces of metal, which are definitely unsafe for microwaving. Check to confirm that harmful traces like aluminum foil are absent from the packaging.
  • Chemicals: Soup containers, cups, and bowls containing plastic layers or waxy coating should be avoided. This notion must be applied to cardboard boxes with printed ink and styrofoam insulation of any kind. The extra components can release dangerous fumes or melt, which could mix potentially harmful chemicals with your food.
  • Microwave temperature: Check the settings on your appliance and set the lost possible level when heating a meal in a cardboard box. In general, set the temperature to low power setting on your microwave when using cardboard to reheat food.
  • Type of food: Avoid heating meals with high water content because heat is generated and radiates relatively slower in case the box is closed. A closed box means a lot of pressure will try to escape, leading to an explosion. Furthermore, heated liquid could jeopardize the integrity of the cardboard mater causing it to get soggy and potentially break down.
Is it safe to microwave food in cardboard

Microwaving Food on Cardboard: Final Thoughts

It can be tricky to determine if it is safe to microwave leftover food in cardboard. From pizza to pasta, cardboard containers are environmentally friendly and also retain hot fresh food for short periods of time.

However, whether it is safe or not can be a vague grey line. Cardboard boxes do not consist of a high amount of water molecules, therefore it may take extra time to heat up the meal.

If you are worried about food getting soggy, due to less water elements, cardboard absorbs the steam to avoid catching fire thereby preventing food from getting soggy. 

When using microwave-safe cardboard boxes, moderation under lower temperature and short timing helps avoid potential fire hazard. 

Always check to see if the box consist of metal or hazardous components such as aluminum foil or plastic and wax coating. These dangers will determine whether it is safe or not to microwave the cardboard with food.

Lastly, do not close the box lid if the food has high water content. Closing the lid while reheating may trap steam pressure which may lead to an explosion. 

From the explanation derived above, the right thing to do before microwaving cardboard boxes is to consider reading the instructions and look for microwave-safe symbol. Ensuring the cup, cardboard box, bowl, or plate is microwave-safe will help prevent a potential microwave danger and maintain your good health. 

If you are using a cardboard box made of pure cellulose or fiber material, then you should rest easy knowing there are little risk involved. Make a habit of reviewing the cardboard box before microwaving your food. 

The exterior of the box will be labeled with instructions clarifying the issue to help you avoid any potential mishaps. If at all uncertain, simply reheat the leftovers on a microwave-safe container to enjoy risk free.

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