Can You Microwave Styrofoam?

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Updated June 27, 2022

Even the best microwaves are a bit of a mystery. What can you really put in them?

One question we frequently hear about microwaves is: “is it safe to microwave styrofoam? Does styrofoam melt in the microwave, or is it okay?” Since this is a fairly important health issue, we decided to talk about it with a little more detail. Whether you have the Kenmore 7212 Countertop Microwave – Editor’s Choice/Best Mainstream Model or another model, we have the answer.

Two Types of Styrofoam

Styrofoam isn’t made to be microwaved…except for a few exceptions.

When people say “styrofoam” they usually mean any of the foam-like, lightweight products used to temporarily hold food and drink: pretty simple, right? But the facts are a bit more complicated. There are two general types of styrofoam out there, with an important difference.

The first type is traditional styrofoam, which is a product name for products made out of polystyrene. Polystyrene is a plastic product that’s made from, among other things, styrene and benzene, which are bad news compounds. Tests have shown that in high levels these compounds are carcinogenic (can cause cancer), can damage reproductive systems, and have a number of other unpleasant qualities. In other words, you don’t want any them in your body, especially from any manufactured products.

Polystyrene is a common plastic compound used for many different purposes.

The problem is that styrofoam doesn’t react very well to heat. High or prolonged heat causes the material to break and melt, which in turn leeches styrene and benzene into foods. The last thing you want to do is put styrofoam in the microwave, or burning it at all. Styrofoam at normal temperatures has been certified as fine to come in contact with foods, but microwaving styrofoam will leech out dangerous chemicals.

The second type of styrofoam isn’t technically the traditional version that we know, but rather a similar product made using different, safer materials, or lower levels of dangerous compounds. It may still be called styrofoam (and look like the same product in some cases), but the ingredients are different from the traditional version, and designed specifically to withstand heat more effectively.

Is this newer version of styrofoam microwave safe? Yes – for the most part. The FDA requires extensive tests for these materials to make sure that any chemical leeching meets safety levels for a lifetime of use. If material tests pass the FDA review, they will have a notification on the material that it can be used in a microwave. If you’re wondering how to tell if styrofoam is microwave safe, simply look at the bottom or sides of the product for any sign, warning, or notification.

Okay, Let’s Talk Common Situations

Melting Styrofoam
You never want your styrofoam to melt under any conditions.
  • Cup of Noodles: We know you’re wondering, “If styrofoam is bad, can you microwave cup noodles in them?” Cup of noodles products are generally designed to be microwavable. However, look on the box/cup and make sure that the instructions allow you to keep the noodles in the cup, and don’t suggest switching it out to another container.
  • Take-Out: Can you microwave styrofoam to go boxes? Take-out is a little more tricky. If your take-out comes in a styrofoam-like box, don’t put it in the microwave – transfer food out first. If your take-out comes in cardboard, it’s probably safe to microwave (just remember to never microwave anything with metal components). Or you could just use the OneBowl, a portable bowl/cup product that’s suitable for everything.
  • Coffee Cups: Can you microwave styrofoam cups? Don’t try it. Styrofoam coffee cups are made for very temporary, quick-drinking situations when the coffee is already heated. They aren’t made to be heated themselves, and the coffee won’t hold the heat very well. Pour your coffee into a normal mug before sticking it in the microwave – or in the little USB mini microwave. For more discerning palates, you can also create espresso from scratch with the Piamo.
  • Throwaway Plates: What about those cheap bulk plates – can you microwave styrofoam plates? Styrofoam plates have generally fallen out of favor in recent years, replaced largely by paper plates. Paper plates can be microwaved, but with greasy foods they might fall apart. Styrofoam plates shouldn’t be microwaved at all.

The Bottom Line

When it doubt, throw it out. Don’t microwave styrofoam materials unless you see a sign that they can be microwaved. If there is any sign that the material is melting or breaking down, throw it and the food out rather than take the chance! If you’re looking for a great new microwave, remember to check out our microwave news and reviews as well!

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