Can You Microwave Styrofoam? Your Questions Answered

We all know how incredibly helpful the humble microwave can be. We also know that there are some materials that should never go in the microwave!

The heating waves won’t penetrate through most metals, while aluminum foil and tin will absorb those waves and quickly catch fire.

Can you microwave styrofoam though, or even heat styrofoam at all?

This guide explains everything you need to know about this important topic. 

I’ll explain how this material works, why heating it is potentially risky, and why you might want to consider some common alternatives instead.

What Is Styrofoam?

Styrofoam is a form of plastic that was originally developed by The Dow Chemical Company.

It’s original purpose was for use in construction, but since then it’s become a material used for all kinds of things including coffee cups, disposable plates and takeaway containers.

It’s fair to say, however, that styrofoam has fallen out of favor in recent years. The material is cheap to manufacture and hugely versatile, but the environmental impact is massive.

Styrofoam doesn’t biodegrade for a start. Estimates of its lifespan range from 500 years to 1 million years.  In other words, we don’t know exactly how bad the problem is, but we know it’s bad.

Before that time passes though, it breaks down into smaller fragments which can cause a choking hazard to animals.

How big a problem has our styrofoam addiction been in terms of landfill? Well, it currently occupies up to 30% of our capacity. The show is very much over for styrofoam, with more than a dozen States currently outlawing – or planning to outlaw – its use.

In terms of domestic use, styrofoam also contains a chemical compound called styrene.

According to the OSHA, this material can cause the following symptoms when ingested:

  • Headache
  • Fatigue
  • Dizziness
  • Confusion
  • Drowsiness
  • Malaise
  • Difficulty concentrating
  • Feelings of intoxication

Don’t panic about your takeout though! In normal use – and ignoring the environmental problem – styrofoam doesn’t cause these problems.

The risk comes from heating the material when it contains food. At higher temperatures, the compound may break down and leech into the food.

How Is Styrofoam Used?

In food terms, there are endless uses for styrofoam. Here are some of the most common though:

Beverage Cups: Styrofoam is a very useful material for serving hot drinks, and keeping them warm while you’re on the move! These cups are also commonly used for liquid meals like soup as well.

Plates: Styrofoam plates are a cheap, disposable alternative that are always popular at outdoor events. That disposable nature is obviously a problem though, and for the environmental reasons I’ve already covered.

Takeout Containers: There’s a good chance your favorite takeout is delivered in styrofoam containers. They’re also frequently provided by restaurants for taking leftovers home.

Is Styrofoam Toxic & Does It Melt?

The main health concern with styrofoam is a chemical compound called styrene. 

Styrene has been declared as “reasonably anticipated to be a human carcinogen”.

So, it’s not a material you want to heat up or encourage to break down in your food!

Styrofoam will begin to soften at 212F / 100C. It will melt entirely as it approaches a temperature of 464F / 240C.

Suffice to say, you can’t cook anything in styrofoam in a standard oven, and your microwave is likely to breach these temperature limits quickly too.

The good news, however, is that it’s fine to use styrofoam for cold storage. If you want to store some leftovers in the refrigerator, there’s no reason to be fearful about using a styrofoam box.

Just transfer the food to a microwave-safe container before heating it up!

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Can You Safely Microwave Styrofoam?

So, is it ever safe to microwave food in styrofoam? What type of styrofoam can be microwaved?

The key here – as with all plastics – is to check for the presence of the microwave-safe logo.

This is a simple design, and consists of a square box with a few wavy lines inside. If you see this mark – from a reputable manufacturer – you can be confident it’s safe to microwave food in it.

If you see the logo, you’re good to go! If you don’t, play it safe and use something else instead. 

Final Tips

Here are some tips to keep in mind when it comes to reheating food in your microwave, regardless of the container material you’re using:

  • If you can’t see that microwave-safe logo on the container, it’s sensible to assume it can’t be used for reheating food. Stick to using the container in question for food storage only. If it’s sold for use with food, it’ll be fine to stash it in the refrigerator or freezer. When you’re ready to heat the food, transfer it to a glass or ceramic dish, or a plastic container that is labeled microwave-safe.
  • Whatever container you’re using, never use any kind of plastic wrap to cover the food. Use a light fitting lid or a plate instead. If the wrap comes into contact with the food, there’s a risk of chemicals leeching into it. In the worst case scenario, it may even melt into the food.
  • You likely already have a collection of Tupperware in your kitchen – branded or otherwise. Make sure your tupperware is microwave safe before using them for anything other than storage.
  • Keep your plastic containers in good condition, and replace them if they show any signs of scratches or cracks. Once it’s in a bad state of disrepair, the risk of compounds leeching into your food increases.
  • If in doubt, use the stovetop instead! We all love our microwaves for the convenience they provide, but it’s always better to be safe than sorry. No logo? Always heat it on the stove instead.
  • When you’re buying new food containers, always keep an eye out for that microwave-safe logo. Any reputable manufacturer worth their salt will include this on kitchenware designed for use in the microwave.
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Wrapping Up

So, can you put styrofoam in the microwave safely?

Given the many alternatives that exist, I’d have to recommend against it.

If I can’t avoid using them altogether, I’ll use styrofoam boxes for cold storage, but always transfer them into something more suitable for reheating.

Consider using microwave-safe tupperware, glass, or ceramic containers for actually cooking the food!

It’s better for the environment, and it’s better for your peace of mind as well.