Can You Microwave Red Solo Cups? Discover the Hidden Dangers

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Chances are you’ve used those ubiquitous red solo cups at a party or get-together before. They’re cheap, convenient, and great for serving drinks in a casual setting. But have you ever wanted to quickly reheat your drink in one? Before you toss that half-full cup into the microwave, let’s take a closer look and see if it’s really safe.

A Brief History of the Red Solo Cup

Before we get into the microwave debate, let’s first understand what exactly red solo cups are made of. These disposable party cups were first introduced in the 1970s by the Solo Cup Company. Though they now come in various colors, the classic red cup remains the most popular.

Red solo cups are made from a material called polystyrene, which is a type of plastic derived from petroleum. Polystyrene is lightweight, rigid, and transparent. It hit the commercial scene in the 1930s and quickly became popular for making food containers, packaging, appliances, toys, and more.

The reasons for polystyrene’s widespread use are simple – it’s cheap to produce, maintains its shape well, and insulates temperature. These characteristics made it perfect for a disposable, on-the-go vessel like the solo cup. And so, the iconic party staple was born.

Why Polystyrene and Microwaves Don’t Mix

Now that we know what red solo cups are made from, we can understand why they and microwaves don’t get along. The primary issue is that polystyrene can’t withstand high temperatures very well.

Microwaves work by emitting electromagnetic waves that cause water molecules in food to vibrate rapidly, creating heat. This happens very quickly, bringing food and drinks to a boiling point faster than conventional ovens.

When polystyrene is subjected to the intense heat of a microwave, a few alarming things can happen:

  • The cup’s shape becomes deformed as the material softens and warps under heat. This can cause the cup to collapse, spill, or leak.
  • The material could actually catch fire as it becomes damaged by microwaves but can’t conduct the heat away quickly enough. This can destroy the cup and be a hazard.
  • Chemicals from the polystyrene leach out into the food or drink contents. This is very hazardous, as we’ll explore next.

So the composition of solo cups just can’t hold up in the microwave without suffering damage. But the bigger concern is the last issue we mentioned, leaching chemicals.

Dangers of Leaching Toxins

When heated, polystyrene can release chemicals into whatever food or liquid is inside, contaminating it. Let’s look at some of the concerning chemicals:


One of the most infamous is BPA, or bisphenol A. BPA is often added to plastics to increase their durability. But it is an endocrine disruptor that can mimic hormones in the body and lead to negative health effects. These include:

  • Fertility issues
  • Developmental problems in children
  • Increased cancer risk
  • Heart disease
  • Diabetes
  • Obesity

Microwaving cups allows more BPA to leach out. Studies show that microwaving food in plastic containing BPA drastically elevates the levels of the chemical.


Polystyrene also often contains styrene, the building block of this type of plastic. Styrene is considered a possible carcinogen and has also been linked to:

  • Hearing loss
  • Liver damage
  • Central nervous system effects

Heating polystyrene releases styrene into food and drinks. The styrene vapors can then be inhaled.

Benzene, Toluene, and Other Solvents

Some of the solvents used in manufacturing polystyrene include benzene, toluene, ethylbenzene, and xylene (BTEX). Benzene is a known carcinogen. Others, like toluene, may affect the nervous system. Heating the cups allows these to migrate into your drink too.


In addition, various additives are used in the production of polystyrene and solo cups. Additives can enhance flexibility, durability, and more. But they also may have negative health effects, especially when heated. These health effects aren’t always known either.

As you can see, microwaving any polystyrene product like a red solo cup comes with the risk of ingesting or inhaling some very toxic substances. That’s a recipe for disaster.

What Could Happen If You Microwave Solo Cups Anyway?

Okay, so we’ve established that red solo cups contain harmful chemicals and aren’t built to withstand microwave heat. But what are the real dangers if you decide to microwave that leftover cocktail or coffee in one anyway?

Here are some gruesome possibilities:

The Cup Melts and Deforms

One likely scenario is that the cup simply melts and loses its structure under the heat. As the polystyrene softens, the cup’s bottom could give out, spilling your scalding hot drink everywhere. Or, it could fold in on itself, causing the liquid to leak out the sides.

This melted polystyrene could also fuse to the rotating plate or walls of your microwave, creating a nasty mess.

The Cup Catches Fire

Perhaps even more alarmingly, the overheated polystyrene could actually catch ablaze in your microwave. The fumes given off by the melting plastic can ignite, causing the cup and its contents to combust.

This could irreparably damage your microwave at best. At worst, it could lead to a dangerous kitchen fire.

The Cup Explodes

Another possibility is that the intense heat and steam buildup cause the cup to explode in the microwave. Hot liquid flying in all directions? No thanks. This could lead to serious burns.

You Ingest Toxins

And of course, you’d be ingesting a cocktail of harmful BPA, styrene, and other chemicals leached from the melting cup. With exposure to high heat and fat/alcohol contents, chemical migration skyrockets.

In the short term, this could cause nausea or headaches. Long-term effects could be much more devastating – think increased cancer risk, fertility issues, and developmental problems if you microwave solo cups frequently.

Healthier Reheating Options

Okay, so it’s clear that microwaving red solo cups is a pretty terrible idea. Here are some safer alternatives for reheating your beverages:

  • Ceramic mugs – As long as they don’t have any metal paints or decorations, ceramic mugs do great in the microwave. They won’t leach any chemicals either.
  • Glass cups or jars – Any glass container without metal lids or parts can be microwaved safely. Borosilicate glass works best.
  • Silicone cups – Silicone is highly heat-resistant and flexible. Silicone cups and food containers are great for microwave use.
  • BPA-free plastic – Not all plastic is created equal. Opt for BPA-free containers labeled as microwave-safe.

The key things to look for are microwave-safe labels and non-porous materials that won’t leach chemicals. With the right vessel, you can reheat your drink safely and avoid solo cup-related disasters.

Microwaving Other Disposable Cups – Still Risky

While we’ve focused on traditional red solo cups, it’s worth noting that other disposable cups carry risks too. Here are some other cups you should keep out of the microwave:

  • Paper coffee cups or paperboard cups – The wax or plastic lining may melt, leach chemicals, or catch fire.
  • Plastic food containers – Even BPA-free plastic could warp, melt, or leach chemicals when microwaved, especially if not labeled microwave-safe.
  • Foam cups – The foam can melt, leach chemicals, or catch fire when microwaved.
  • Plastic airline cups – Most airline cups contain BPA and aren’t designed for microwave use.

The safest bet is to transfer your drink into a ceramic, glass, or silicone container before reheating. It’s not worth taking risks on other disposable cups not made for high heat.

Microwaving Precautions

If you do opt to microwave your drink in a safe vessel, take these extra precautions:

  • Remove any metal lids, which can spark and cause fires.
  • Use lower power levels and heat for less time to prevent splattering or boiling over.
  • Allow a vent hole for steam to escape and avoid pressure buildup.
  • Carefully handle the hot container afterwards using oven mitts.
  • Avoid microwaving drinks with high alcohol content, as this is flammable.
  • Stir well before drinking to distribute heat evenly and prevent burns.

Exercising caution is key to preventing accidents whenever using a microwave.

Frequently Asked Questions

Let’s recap some common questions about microwaving solo cups:

Can you microwave a red solo cup with water in it?

No. Water can quickly bring the polystyrene to melting temperatures. The cup could leak, deform, or release chemicals into the hot water.

What about microwaving a red solo cup with alcohol in it?

Definitely not recommended. Alcohol’s low boiling point and flammability make it extremely hazardous to microwave in a red solo cup.

Is it bad to microwave a red solo cup with coffee?

Yes, you shouldn’t microwave any liquid in a red solo cup, including coffee. The cup’s integrity will weaken and chemicals could taint your beverage.

Can you microwave a red solo cup with soup?

No way. The hot fatty soup could cause rapid melting and leaching of chemicals from the polystyrene cup.

Can red solo cups go in the dishwasher?

Dishwashers also expose the cups to high heat and pressures. It’s best to hand wash red solo cups gently instead.

Can you reuse a red solo cup after microwaving it?

Never reuse a solo cup that has been microwaved. Even if it appears intact, the heat may have caused invisible damage to the cup’s structure and released toxins.

The Verdict

Let’s review the key takeaways:

  • Microwaving red solo cups is dangerous due to melting, fire hazards, and leaching of chemicals.
  • Solo cups contain harmful substances like BPA, styrene, benzene, and other additives that can migrate into food and drinks when heated.
  • Safer reheating options include ceramic mugs, glass containers, silicone cups, or BPA-free plastic labeled microwave-safe.
  • Take precautions even when using microwave-safe vessels, like removing metal parts, stirring afterwards, and heating cautiously.

So remember – as convenient as they may seem, red solo cups and microwaves are a combination to avoid at all costs. Your health and safety just aren’t worth the risks!

By Rosie Elliott

I’m Rosie. I’m a professional chef with experience in Western, Mediterranean, and Italian cuisine. I’ve been cooking for over 15 years, and I have two daughters that keep me busy!

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