Quick Answer: You can microwave cardboard if it has the microwave-safe label.
Some types of cardboard are meant exclusively for packaging and structural support, and you'll find out why below. We'll also be sharing some crucial information about the safety labels, plus some helpful tips for safe microwaving.
Let's get started...
What Is Cardboard?
Cardboard, also called paperboard, is a heavy paper product that's usually on the thick side. It's typically used for packing and shipping, but you'll also find quite a few cardboard items in your home:
- Cereal boxes
- Paper towel rolls
- Shoe boxes
- Frozen food containers
Then there's corrugated cardboard, which is usually two flat cardboard pieces with a grooved piece in the middle. This is often seen in shipping boxes and six-pack beverage containers.
When it comes to cardboard and cooking, things can get a little bit tricky. Some cardboard products, especially those used for purposes not directly related to food, have a chemical layer on them. In this case, you really don't want to be cooking with or microwaving them.
Different Types of Cardboard Containers
Cardboard products used for food packaging purposes come in many forms, many of which you're probably already familiar with.
- Take-out containers
- Pizza boxes
- Recyclable bowls
- Disposable cups
- Sectioned food trays
- Eco-friendly food packages
Microwaves also come with cardboard piece placed inside to cover the waveguide (you're not supposed to take it out).
Read Also: If you cook with your microwave pretty often, check out our Microwave Toaster Oven Combo Options Guide.
How Do You Know If Cardboard Is Microwave Safe or Not?
The only way to know for sure if a piece of cardboard can be heated in the microwave is to check for a label that says "microwave safe."
Even though a lot of frozen and fresh foods are wrapped in cardboard, it's still not a good idea to put the cardboard in the microwave unless you see the label. Chances are, it's just meant for shipping and wrapping, not for heating.
Just like printed paper, printed cardboard shouldn't be microwaved, either. The ink can be absorbed into your food, which is definitely a health hazard.
What about take-out in cardboard containers? If you receive a food order in a cardboard container, it's likely that it's safe for heating (provided it doesn't have metal handles), at least at moderate temperatures. If you're not sure, you can always ask the restaurant.
Labels on Cardboard to Be Aware Of
You know that you can microwave cardboard that has the "microwave safe" seal of approval right on the material. But there's another way to assess whether a cardboard container is microwavable, or rather, not microwavable.
Sometimes you'll see labels indicating that a container is not microwavable. This is just as helpful as a label that shows that a container is microwave-safe as there is no question about it.
But if there's no label either way, follow the above guidelines. When in doubt, transfer food to a container you know is microwavable.
Bonus Safety Tips
If you're going to heat up your food on a piece of cardboard, you might want to follow these safety measures:
- Check to make sure that there are no metals, glues or non-cardboard materials in sight.
- Make sure there are no plastic or other coatings on the cardboard.
- Only do quick reheats with cardboard and paper products. Leave the longer cooking to sturdier microwave-safe materials.