There are lots of materials you can microwave and lots of materials you can’t. Ceramic, porcelain, glassware, and chinaware are safe for microwaving, especially if it’s labeled as such. The thicker they are the safer they are to microwave (or take on high temperatures in general).
Any plastic container that’s undamaged and labeled as microwave-safe. Some Styrofoam variants can also be microwaved. Otherwise, most plastic and Styrofoam should not be microwaved. However, what about paper?
Can You Microwave Paper?
It depends. Paper can be microwaved as long as it’s the right paper type. You should also limit the power and minutes used to microwave with paper things like the paper plate because the paper is flammable and the glass plate below could char it up when superheated.
Paper Plates, Bowls, and Towels as well as Wax or Parchment Paper
It’s safe to microwave paper plates and bowls parchment paper, wax paper, and paper towels. Don’t microwave paper plates with foil or plastic coating though. The foil can reflect the microwave radiation and can cause arcing or sparks. The plastic can leach toxic contaminants into your food.
Don’t microwave something covered in newspapers as well. This is because its ink can leach right into your food as you microwave it, which isn’t sanitary. It’s just like with non-microwave-safe plastic containers. Instead of microwaving newspaper, use parchment or wax paper.
How about Brown Paper Bags and Cardboard?
Don’t microwave brown paper bags either. If you’re microwaving your leftover McDonald’s meal, it’s better to do so with all the wrapping paper and bags removed, with the burgers and fries placed on a ceramic plate or something.
Cheap brown paper bags can’t withstand heat and can catch fire, unlike the more heat-resistant paper plate. They might also contain germs and emit toxic fumes that could transfer to your food when push comes to shove.
What about Microwaving Cardboard?
Cardboard is also made of paper like paper plates and towels. So that means cardboard is safe to microwave like them, right? Nope. Cardboard takeout boxes can contain fasteners or metal handles that can serve as a fire hazard as well.
Cardboard is cheap, stiff paper that can contain various waxes, glues, and other fire-inducing materials. It won’t go up to flames like a tinderbox necessarily, but the longer you microwave it the likelier it will go up in flames. It’s definitely a safety hazard for your microwave oven appliance.
Related: Can You Microwave Cardboard?
Paper’s Equilibrium Moisture Content
Paper has the “equilibrium moisture content” of 8 percent. Drying paper out with a microwave oven’s radiowave so that it dries out to about 1-2 percent of moisture content, it can catch fire. Even though the microwave rays don’t affect the paper, the glass plate below and the food being heated could.
This is the reason why even the paper plate, which is considered microwave-safe, can sometimes get burned on the underside when left in the microwave for too long. It has enough moisture to affect its temperature, the food on top of it can get really hot, and the glass plate below also absorbs food heat.
How Flammable is Cardboard inside a Microwave?
On one hand, people have used microwaves before to dry out the wet paper. There are people who’ve microwaved water-damaged books without incident. On the other hand, if it gets too hot it will catch fire because the paper is flammable by nature.
Paper plates seemingly made of the same cardboard material use safer materials to allow them to possess microwaveable properties. They don’t contain as many unsafe glues and waxes as office-grade cardboard folders for example.
If Dry Paper Is Flammable Then Shouldn’t Paper Towels Catch Fire?
Paper towels are both microwave-safe but flammable to a certain point. Don’t microwave a paper towel alone. That will catch fire. Instead, use it in tandem with food to fulfill certain jobs, like catching grease or moisture.
Also, make sure that the plate or bowl is clearly marked as microwave-safe. Even if it is labeled as such, if it’s damaged or compromised, it ceases to be microwave-safe. The paper plate or towel should be in pristine condition before being used.
Don’t Experiment Too Much with Paper Plates and Towels
A paper towel alone being microwaved can lead to it being hot enough to get charred in a minute or two. Actually, there are people who’ve tried microwaving paper towels and ended up with their microwave dying a week later.
You absolutely should not allow anything to catch fire inside your device, because it can destroy your appliance once it’s interior circuits are overheated. The paper towel should catch splattering food instead of microwaved on its own.
When Do Paper Plates and Paper Towels Catch Fire?
As established above, once the paper plate, paper towel, or paper anything reaches the equilibrium moisture content of 1 to 2 percent it becomes a fire hazard. However, if they’re used as intended—reheating food for about 1-3 minutes or absorbing moisture, they work fine.
What does this mean? Don’t microwave a paper plate or towel alone. They can catch fire if the food is cooked long enough. Hot grease can particularly turn the paper plate to pulp, which is why some plates have foil or plastic coating.
However, you can’t microwave paper plates coated with those materials. It’s enough to make paper plate microwaving a bad idea except for quick reheating. You definitely can’t cook food on a paper plate.
Use ceramic or glass plates instead to play it safe. Better err on the side of caution than to risk setting the inside of your microwave on fire. You can also use Tupperware and other thick, microwave-safe plastic containers as well.
How microwave-safe paper depends on the paper and the situation. Paper plates and paper towels are microwave-safe as long as you don’t microwave them too long. Sheets of paper can catch on fire if heated up to 1-2 percent moisture or dryness.
You can also use wet paper towels to make them “microwave-safer”, but you need to be careful when it comes to overheating them to dryness. It also depends on the type of paper you use. Parchment or wax paper is okay to microwave. Cardboard, newspapers, and brown paper bags are not.
- Karen B. Gibbs, “What can and can’t go in a microwave? An expert reveals the answers“, Today.com, December 17, 2016
- “Is it safe to microwave sheets of paper?” Quora.com, July 17, 2017
- “What can you microwave?“, Whirlpool.com, Retrieved April 25, 2021