You’ve probably heard that you shouldn’t put any sort of metal or foil in the microwave. But what people really want to know is whether or not cardboard is safe in the microwave when it is being used as a container for their foods, particularly leftover food.
Yes, cardboard is safe in the microwave. However, cardboard can come with extra hangers-on that are not as safe, such as staples, metal utensils, and other things that react poorly with microwaves. In short, cardboard is safe, but be sure you are only putting cardboard and food into the microwave.
Will Microwaving Cardboard Make The Food Inside Unhealthy?
This is a common concern, but the short answer is no.
The reason people think this is because a great many food containers actually do break down at high temperatures. If you have ever heard people advise against drinking out of a warm water bottle, it is because water bottles break down at high temperatures and begin to mix their ingredients into the water inside.
This does not happen with cardboard as, simply put, the cardboard does not break down in the same way, at the same temperatures, or into damaging chemicals. As stated previously, the water in your food is more likely to mix with the cardboard, as compared to the cardboard mixing with the food.
The best way to think of this is thusly: If the cardboard were to break down and mix with the food, it would happen in such an obvious way that not only would you immediately know about it, but it would become difficult to eat the food. The most likely situation is that the cardboard would completely fall apart.
Sure, it would “mix” with the food in a way that would make the food bad to eat. But unlike the water bottle example, this would not be a secret. It would be obvious and make it hard for you to even pick up the food.
Cardboard is quite beneficial for the modern person trying to reheat food on the go, as it holds things together while generally being incredibly low maintenance. Just be super, duper sure it does not have any metal in it.