Q. I frequently have take-out or leftover foods in cardboard containers and want to reheat them without getting extra dishes dirty. Can you microwave cardboard?
A. When you want to quickly reheat food without using dishes and creating extra cleanup work, putting cardboard in the microwave is an attractive option. In general, it’s safe to put cardboard in the microwave but there are a few important precautions to take.
First, ensure that you never place an empty cardboard container – or plain cardboard of any type – in the microwave without food or liquid. Cardboard and other paper products are flammable and can cause steam explosions if heated to a sufficiently high temperature without food or liquid to absorb the microwave’s energy.
Second, make sure that the cardboard container does not contain any metal parts. For example, many take-out cardboard containers from Chinese restaurants contain metal handles. It’s never safe to microwave these as the metal handles will spark and damage your appliance. On rare occasions, recycled cardboard can contain metal particles and spark in the microwave but this is generally not an issue with food containers.
Another potential issue with microwaving cardboard is that some containers contain or are coated in plastic. This is not a common issue but before placing cardboard in the microwave, check for a plastic or wax coating. If it feels overly slick or smooth to the touch, it might not be microwave safe, as it could emit toxic fumes or partially melt.
Once you’re confident that your cardboard is safe to put in the microwave, you should still carefully monitor the food or drink being reheated. Liquids that are heated for too long in the microwave can be superheated and cause explosions. It might not damage your appliance, but it poses a safety hazard upon opening the microwave or drinking the beverage. Heating food for too long can also damage the integrity of a cardboard container, render the food inedible, and leave a mess in your microwave.
As long as you exercise proper caution by ensuring your container is not empty and does not contain any metal or plastic, microwaving cardboard is a quick and easy way to reheat food.