Can you microwave styrofoam? (The Real Answer)

If you’re a fan of quick meals and frozen leftovers, you must be an avid microwave user. But that also means you need to know what you can and cannot microwave.

Glass, polypropylene, polystyrene, borosilicate, plastic, and so on – there are so many different kinds of materials that it can often get confusing to decide if you can put the container in a microwave. 

And while there’s a simple microwave-safe or not microwave-safe when it comes to these materials, the same is not the case with styrofoam. 

Styrofoam is an entirely different story. You can and cannot microwave styrofoam. 

Confused?

Read on as I explain whether you can microwave styrofoam or not.

Can you microwave styrofoam?

You can microwave beverages or food in styrofoam containers that have the microwave-safe symbol or label. If there’s no label or symbol, the container is most likely not safe to microwave.  

There’s some concern when it comes to microwaving styrofoam. Styrofoam is essentially a trademark name for polystyrene foam. This is a petroleum-based plastic that is often used for packing and serving food and beverages.

Styrofoam contains a compound known as styrene, which has often been linked to cancer in both humans and animals. In some cases, styrofoam can even melt, causing harmful chemicals to leach into your food. This is very common when microwaving fatty foods like cheese and meats. 

However, the FDA regulates polystyrene plates, cups, and containers and tests if they are safe to use in the microwave or not. So, if they say they are microwave-safe, that means they’ve been tested in the microwave. And if they don’t, that means their safety isn’t guaranteed and it’s best not to put them in the microwave.

Is it safe to microwave styrofoam?

This depends on the kind of styrofoam in question. Traditional styrofoam is not safe to microwave, but you can safely nuke microwave-safe styrofoam.

There are basically two kinds of styrofoam containers. And while one is microwave-safe, the other isn’t. 

Traditional styrofoam is the most commonly used kind of styrofoam. And the material stays stable during normal use. But as you subject it to high temperatures, it starts to melt or even break down. 

Sometimes, you might not see any visible damage, but it can cause styrene and other chemicals to leach into the food. As mentioned earlier, styrene is carcinogenic and can also affect the reproductive system.

On the other hand, we have microwave-safe styrofoam. This kind is not too common but it meets the FDA requirements and is considered safe. This is because it is more stable, even under high temperatures. Plus, it is made of a safer material and contains only a small amount of dangerous chemicals.  

If your styrofoam plates, cup noodle containers, and coffee cups are made of the latter kind, you can microwave them. But it’s still important to be careful. You should only microwave them for 30 seconds at most, and that too at medium power. Heating them for longer than that can be dangerous.

Styrofoam is basically plastic with foam and overheating can release harmful chemicals into the food. Apart from cancer and problems with the reproductive system, such chemicals can also cause vision and digestive issues.    

Of course, there’s a way to know if the styrofoam you have is microwave-safe or not. Just check the packaging for a microwave-safe symbol or a label. If it doesn’t have the label or symbol, it means you probably shouldn’t nuke it in the microwave. But it’s up to you if you want to take the risk.

But if there are any signs of damage once you microwave the styrofoam container, make sure you throw out both the container and the food. You should also not microwave styrofoam with cracks or a container that you have already microwaved once.

How long can you microwave styrofoam?

You should microwave styrofoam for a maximum of 30 seconds. Any longer than that and you risk the styrofoam melting.

Today, there are many microwave-safe styrofoam containers available that can handle standard reheating. This is not the case with traditional styrofoam. Just make sure you don’t go overboard or microwave the former for excessively long. 

Can your microwave styrofoam cups? 

The answer to this also depends on the kind of styrofoam you have. Any styrofoam cup without the microwave-safe symbol or label shouldn’t be subjected to heat.

Traditional styrofoam is a kind of porous plastic that contains numerous chemicals. Such kind of styrofoam melts in the microwave very quickly. And I mean very, like in just seconds. 

And that doesn’t just ruin the cup’s structural integrity; it also leaches harmful chemicals into your beverage. These chemicals might not instantly make you sick, but they can have an adverse effect in the long run. 

But you can microwave cups that have the microwave-safe logo on them. If you’re not familiar with it, it’s basically a small microwave with three squiggly lines or waves. In some cases, it might just be the three waves on top of a container. And if there’s no symbol, there might be a label. 

If any of these are present, you can just go ahead and put the cup in the microwave. If not, you’ll have to look for some other way to heat your coffee or tea.

Can you microwave styrofoam takeout containers?

It’s best not to microwave styrofoam takeout containers because they can change shape or, worse, melt. 

I understand why you’d think it’s safe to microwave styrofoam takeout boxes. After all, they do hold piping hot food, so it must be fine – right? But that’s not entirely the case. Styrofoam doesn’t react to whatever it’s holding, even if it’s super-hot. But it does react to being heated. 

When you heat styrofoam, the polymer starts to expand. And once it hits a certain temperature, it starts to change shape and melt. 

So when you want to heat food that’s in your takeout box, first transfer it to a microwave-safe container and then reheat it. You can then put it back in the takeout box if you want to enjoy eating out of it. 

Tips to microwave styrofoam 

As you’ve seen by now, it’s a little tricky to decide if you should microwave styrofoam. Here are some more tips that can help you decide:

  • Always look for cracks and scratches before putting the styrofoam container in the microwave, especially if it’s old. If you don’t, it might leach harmful chemicals into your food.  
  • Make sure there’s some way for steam to escape from the styrofoam container. Doing so makes sure that there’s no pressure build-up, which can otherwise cause an explosion.
  • The container might be hot once you’re done microwaving. Make sure to use gloves or mittens to take it out of the microwave so that you don’t burn your hands.
  • If you’re not 100% sure that your container is microwave-safe, it’s best not to put it in the microwave. Instead, transfer its contents into a microwave-safe ceramic or glass container. 
  • To ensure that the styrofoam is safe to use in the microwave, look for an FDA-approved seal or label at the bottom. If it’s present, that means the container has passed FDA standards and can be microwaved for up to 30 seconds.
  • A lot of people tend to cover the food to prevent a mess during microwaving. While this doesn’t dirty the microwave, it can be dangerous. If steam doesn’t have a way to vent out, it can overheat and melt the styrofoam container. 

Wrapping It Up

So now you know if you can microwave styrofoam or not. Make sure you never microwave styrofoam – whether that’s cups, plates, takeout containers, or boxes – if it doesn’t have a microwave-safe symbol. 

And if there’s any sign of the container breaking down or melting in the microwave, make sure to throw it out along with whatever is inside it. After all, you don’t want to risk ingesting dangerous chemicals! 

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