Can you microwave cardboard? Experts and chefs share whether it's safe, and what to do instead

Microwaving cardboard might seem like a quick, convenient way to reheat food. You might've even done so in the past without anything going wrong. But is it actually safe to microwave cardboard containers?

Cardboard is made of paper fibers and flammable, meaning microwaving it leaves your kitchen open to a fire risk. Before attempting to microwave anything in a cardboard container, make sure you understand the risks involved, as our electrical and cooking experts warn.

Microwaves produce an extremely high heat, so cardboard should go onto the list of kitchen items you can't microwave. Here's what the experts have to say.

Can you microwave cardboard?

In short, no. Cardboard's composition includes some flammable materials which, if exposed to the high heats food and liquid reach when being microwaved, could ignite.

'As an industry expert focused on machinery solutions for over 25 years, I know cardboard and microwaves do not mix well,' warns Todd Cleppe, executive engineer at CFAB. 'The coatings and materials frequently found in food packaging and containers will ignite quickly under intense, focused microwave heat.'

Dennis Littley, chef of more than 40 years and owner of Ask Chef Dennis, adds, 'Cardboard is made from paper fibers, and when exposed to high heat can become a fire hazard if it gets too dry. If the cardboard has plastic coatings, waxes, or inks, which a lot of food packaging does, then you might also be dealing with some sketchy chemicals leaching into your food.'

The food inside the cardboard container also poses a fire risk as Al Fouz, owner of Abaco Air Experts, highlights. Al says, 'Pizza boxes are especially dangerous since they frequently contain grease residue. If the cardboard does catch fire, the flames can spread rapidly even after removing it from the microwave.'

Are some cardboard food packages safe to microwave?

There are some types of cardboard packaging that are designed to be microwave-safe. '[Certain types of cardboard] are often designed with microwaving in mind, and they can handle the heat without causing too many problems,' says Dennis, but you should only do so if the packaging specifically states that it's microwave-safe. If it doesn't, it likely hasn't been treated to be able to withstand high temperatures.

Instead, transfer the food to a microwave-safe container or dish and place a microwave-safe plate cover available at Target, to avoid food splatter. 'The risks of damage or injury are simply too great, no matter how convenient microwaving the cardboard packaging may seem,' Todd says, so make sure you read the instructions.

If you're running low on microwavable food containers, here are some low-priced and reliable options.

Next, find out whether microwaves are bad for you.