Can You Microwave Cardboard? 

You are often tired after a long day at work, but you need to take warm food. Your food stands in a cardboard container, and you think of microwaving it.

Should you go ahead and microwave your cardboard container?

The answer depends on the type of container your cardboard is. While some cardboard containers are microwave-safe, some are not.

Can you microwave cardboard? Microwaving the latter can damage your microwave and even cause a fire.

If I were you, I’d seek information about what it takes to microwave a cardboard container. 

Please read on to see what you should look for if you want to microwave your cardboard container.

Is Cardboard Microwave-Safe?

Yes, cardboard is microwavable. But that depends on the making of the cardboard.

Not all types of cardboard are microwave-safe. The only safe cardboard in the microwave is the one that’s pure cellulose. 

But that’s not just it. To ensure your cardboard doesn’t get damaged, you must reheat food for short durations of time.

Consider keeping it inside for durations of between 60 and 120 seconds. While doing that, check every 30 seconds to minimize the risk of overheating the cardboard.

It’s equally important to keep your microwave in a low-power setting.

What if you’re planning to reheat food for a longer duration?

If so, please transfer your food to another microwave-safe container. Better keep in mind that cardboard is flammable.

At temperatures exceeding 400°F, your cardboard can catch fire. The same case involves when you reheat it for a prolonged reheating duration at high temperatures, the moisture level on the cardboard declines. This ends up increasing the likelihood of the cardboard catching fire.

What Types of Cardboard are Not Microwave-Safe?

Although it’s safe to microwave cellulose-made cardboard, there are options that shouldn’t go into the microwave. You should never toss your cardboard in the microwave if:

  • It’s waxed
  • It’s printed with inks
  • Contains metal or adhesive

You should never microwave these types of cardboard containers unless they contain a label that expressly states otherwise.

Why You Shouldn’t Microwave Waxed Cardboards

The wax that coats cardboard and paper containers is in most cases polyethylene or PE in short form. When you heat this plastic at high temperatures, it’ll melt and leach chemicals into your foodstuff.

You don’t want to suffer the consequences of that happening. Having such chemicals in your foodstuff makes you vulnerable to severe disorders like cancer.

Luckily for you, you can spot these containers with much ease. They are shinier and smoother than ordinary cardboard.

Why You Must Avoid Microwaving Cardboards with Ink

Like waxed cardboards, cardboards with ink may also contain hazards. But there are some printed cardboard containers that aren’t dangerous.

To be on the safe side, you should read the label carefully and stick to microwaving containers under the “microwave-safe” class.

Why Is it Dangerous to Microwave Cardboard Containers with Adhesive?

Assembling of packaging mainly uses adhesive. Putting cardboard containers with adhesive into the microwave puts you at a hazardous risk.

Such a process can result in releasing of toxic gasses that will go into the foodstuff and cause health problems. 

Why Food Containers with Metal are Unsafe to Microwave

Many take-out establishments use trays that contain metal. Putting metal of any type into the microwave is a big NO!

Apart from damaging your microwave, such cardboard containers may cause fire. 

There will be instances when you’re not sure whether to microwave your container or not.

The golden rule is, if you’re not sure, follow the guidelines on the label. If you’re still not sure, please don’t place your container into the microwave.

Nature and Types of Cardboard Containers You Should Know About

Cardboard is a heavy paper-based container whose production provides various thickness options. You can also refer to it as paperboard, and it is helpful for your packaging and transporting needs.

Besides being useful when on the go, cardboard containers are also useful for several household needs. You may find the following cardboard containers in your home:

  • Kitchen paper rolls
  • Shoe boxes
  • Food packaging

In some instances, you may also have corrugated cardboard at home. These contain two pieces of flat cardboard sandwiching a grooved piece of cardboard in between them.

If you’re looking for a safe-packaging material, this is the right choice for you. It’s not a wonder that shipping boxes and beer six-packs are often made from corrugated cardboard.

As much as cooking and cardboard are concerned, you must be a little careful. The make-up of several cardboard products could contain harmful chemicals.

These are mostly cardboard products that are hardly associated with foods. For your health’s sake, please avoid placing such materials into your microwave.

The trend to minimize the amount of waste that gets to the environment triggers the usage of cardboard containers repetitively.

Types of Cardboard Containers and Their Uses

Cardboard containers in the food industry come in a variety of sizes and shapes. Each size and shape is meant for various needs in the household and outside when journeying.

Here are a couple of cardboard containers and their uses:

  • Cardboard containers for take-out foods
  • Pizza box containers
  • Cardboard disposable cups
  • Cardboard compartmentalized food trays
  • Eco-friendly food packaging cardboard containers

Types of Cardboard Containers You Can Microwave

The first thing you should note is that microwaving cardboard containers by itself can spark a fire under some instances. 

Any cardboard product has the potential to generate fire if you heat it for a prolonged duration of time. 

Although some publications may recommend heating a cardboard container on its own for drying reasons, I want to draw your attention to the fact that it would be quite dangerous. 

That requires the highest level of carefulness, but I suggest you don’t try it.

If you must dry food in your microwave, please go for another microwave-safe container like glass or ceramic container.

To know if the cardboard container can go in the microwave, always look for a label eat Food in the Cardboard Container?

Yes, you can reheat food in a cardboard container. But you must do it for a limited time to avoid generating a fire.

If you reheat your cardboard container for long or at high temperatures, it’ll possibly light on a fire because it’s relatively a good conductor of fire. 

Being a combustible material makes cardboard capable of initiating fire on exposure to an open flame or sparks.

While cardboard containers may ignite in some situations, they are made to work perfectly in lower heat levels. This means that cardboard burning when reheating food isn’t a high risk if you follow the right guidelines.

Additionally, crafting cardboard boxes includes using pure pulp and wood fiber. This makes the containers ideal for microwaving food.

Some cardboard containers could also contain metal pieces to hold the pieces of the container intact and avoid water leakage. 

If your cardboard box contains metal pieces, it can be dangerous to place it in the microwave.

The golden rule is to avoid reheating cardboard boxes for a prolonged duration of time. 

With only a 12% moisture level, reheating them for a long time will certainly lead to the dropping of this moisture and an increase in the generation of fire.

Important Notes to Take Before Microwaving Cardboard

You should be keen on the type of cardboard you’re placing in the microwave. Not all cardboard containers are safe to reheat in the microwave.

Before microwaving your cardboard container, here are some critical considerations to make:

Start by checking the label – Some may contain instructions about the safety of microwaving them. Always check for a small three-wave icon indicating microwave safety. If that’s not there, look for written instructions.

Check for metal – check for traces of aluminum in the packaging. Avoid placing it in the microwave in case you find metal substances.

Microwave temperature – Check the temperature setting in your appliance and set the lowest level when microwaving a cardboard box. 

Type of food – Heating food with high water content is highly dangerous because that generates heat and causes it to radiate relatively slower if the box is closed. 

When closed, a lot of pressure will build up and try to escape, causing an explosion. Heated liquid could also jeopardize the integrity of cardboard matter causing it to get soggy and potentially break down.


How do you know if a cardboard container is microwave safe?

Checking the label to see instructions stating that it’s microwave-safe is the surest way to verify your container’s safety in the microwave.

You may also go through the instructions in the packaging if the label is missing.

What does microwave-safe mean?

Microwave-safe means the container can go into the microwave. 

This is mostly a sign showing a microwave with some wavy lines on it. Alternatively, a microwave-safe container could have a #5 on it. 

Bottom Line

Whether your cardboard is safe to reheat in the microwave depends on its material constituents.

Pure cellulose cardboard containers are absolutely safe in the microwave. But those with metals, adhesive, and ink cannot go in the microwave.

Please reread the guidelines in this article to avoid messing your microwave or causing an explosion when reheating food in the cardboard container.

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