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Can You Put Styrofoam in Microwave?

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A microwave is an essential appliance in the kitchen. It helps save time while cooking, defrosting, or warming food, and many even use microwave to reheat takeout food in the styrofoam for time saving and eliminate washing dishes. 

However, microwaving styrofoam may not always be the most appropriate option to use while heating food. Let’s discuss whether or not you should be putting styrofoam inside a microwave to begin with.

Can you put styrofoam in the microwave? Most types of styrofoam are not designed for use in a microwave. Always check the microwave-safe symbol to ensure proper usage. 

If the icon indicates CPET #1, then the styrofoam is microwave-safe. Even if it is safe for microwave usage, lower the power setting to reheat the meal and avoid overheating the container.

Styrofoam containers are suitable for maintaining heat by insulating hot food, keeping food in shape and protecting it while traveling. Before deciding whether using Styrofoam in a microwave is safe, it is crucial to note that there exist two different types of Styrofoam containers available in the market that you need to be aware for selection.

In this article, we are discussing the types of styrofoam that are safe to use in microwave, what styrofoam is made out of, danger of styrofoam and how to identify microwave-safe styrofoam. Read through to gain understanding about answers to frequently asked questions about using styrofoam for your daily meal prep. 

What Is Styrofoam Made of?

Styrofoam is a manufacturing trademark for polystyrene. This chemical compound known as polystyrene is a petroleum-based product that is made of styrene monomers. 

During polymerization, styrene is converted into polystyrene.  Hydrofluorocarbon is added, and the mixture is left to form a product by expanding under pressure.

Styrene is a relatively light material, with 95% part of it being air, giving it excellent insulation properties. Styrofoam does not sink and easily maintains its form due to the high amount of air inside its structure. 

Styrofoam does not break down for an extended period, hundreds of years, and melts when heated in high temperatures to emit carbon and little water as by-products. Under normal heat, it emits carbon monoxide and carbon black that are environmentally hazardous.

Styrofoam Safe for Microwave Use

The microwave-safe type of Styrofoam is not commonly available in the marketplace. It is tested to meet the safety requirements for microwave use under specific guidelines. 

The containers are made of safe materials, which have fewer toxic compounds and a higher melting point. Also, it does not melt very quickly when heated due to its enhanced stability.

When determining whether your container is microwave safe, check for a safety label imprinted on the bottom. However, if you discover visible damage to the Styrofoam box after heating using a microwave, dispose the container and don’t consume that food. 

Styrofoam container with cracks in the material should not be heat in the microwave, neither should you reuse it for any food storage.

The crack or damage on the Styrofoam actually releases toxins into the food. When consumed, the food may result in harmful side effect to the body. 

Always check the condition of the container before placing it into the microwave. If it has significant damage, transfer the food to a microwave-safe container in order to reheat.

Traditional Styrofoam

The most common type is traditional Styrofoam, which is not safe for microwaving. The material appears typically stable when using under average temperatures, however when heated at high temperature, it will start to melt and deform the container.

Unfortunately, microwave heat might result in toxic chemicals leaching into your food. Styrene and acetone are linked to cancer, and are dangerous to your reproductive system.

Can Styrofoam Go in The Microwave?

Most Styrofoam will melt, even at low temperatures, and do not conduct heat at all making it difficult for the outer part of the container to sense the temperature of the food. These containers are great to transport food and maintain warmth of food in a short time. 

On the contrary, using microwave-safe Styrofoam containers to safely warm food in the microwave is acceptable. Manufacturer’s instructions should be keenly followed when using these containers. 

Don’t exceed the stated heating temperature and avoid cooking food in the microwave using Styrofoam containers. They are typically designed for defrosting and reheating temperatures, not the high heat temperatures required for cooking.

Minimize the power setting to low and only use microwave-safe Styrofoam to reheat meal in 30 second bursts that do not exceed 1 minute per cycle. If you have to cook in the microwave, do not use Styrofoam plate instead place food on a microwave safe plate for best results.

How Can You Tell If Styrofoam Is Microwave-Safe?

When you want to reheat food, but can’t tell if your container is safe, consider the instructions below to ensure your styrofoam can handle the heat from the microwave.

  • Look for a symbol at the bottom of the container. The microwave safe symbol is wavy lines. If #5 plastic is indicated on the container, the container was made using polypropylene which is perfect for microwave use.
  • If the container is CPET or #1, then it is safe to use for microwave. Usually, these products are used for oven application, however it is different from APET since it can withstand higher temperatures due to its crystallized nature. 
  • APET is unsafe for microwave. They include water bottles and plastic containers. In general, most products used to store cold food with clear packaging are not safe for reheating, however you can recycle them.
  • Number 6 Styrofoam is not completely microwave safe, but it may depend on certain factors. These containers are typically for disposable use only, therefore it is not recommended for microwave use.
  • Styrofoam #7 is unsafe for microwave use. These are containers made of insulation properties, which will help keep food warm when traveling, but avoid using them to heat food in the microwave. 
  • Containers made of harvest fibers are not suitable for microwave since they are made up of natural components. These are paper cup, plate, or takeout container due to coated, sealed, or glued to stay together which additives could leak into your food. 

Not every Styrofoam is capable of microwave heat. Depending on the type and ingredients, they do react differently when forced heat is applied in the microwave. 

Double check the microwave-safe symbol on each Styrofoam to identify whether it is safe to microwave in the first place. It will help you to reheat your meal without any concern. 

Is It Dangerous to Microwave Styrofoam?

Styrofoam containers without safety labels are likely to melt when heated under high temperatures. It’s not a good idea to use such containers; they are a potential health hazard. 

Styrene is a dangerous chemical and will leach into your food if precautions are not followed. Consuming the compound, like many other chemicals, may be risky and damage your body leading to poor health.

However, if the container has a microwave-safe label, consider using it but not more than once. Styrofoam containers are not reusable in any condition. 

Putting constant heat overtime, the Styrofoam not only will misshapen, but may also leak harmful toxins to the food. If you are heating food under high temperatures that can burn the Styrofoam container, transferring food to a ceramic or glass dish is inevitable.

Things to Know Before Putting Styrofoam in Microwave

After finding out if the Styrofoam is safe for microwave, there are additional tips to know before using them. Even though they are microwave-safe, it still requires careful attention to avoid any unwanted result. 

Here are things you need to know before placing styrofoam in microwave.

  • Never reheat food more than one time.
  • Check the condition of microwave to ensure in good condition before putting in Styrofoam. If it has any sign of failure, avoid using the appliance.
  • Make sure your Styrofoam container has a microwave-safe icon stamped on the bottom. The last thing you want to do is risk your health. 
  • Consider transferring the food into a safer container before heating if the current one cannot withstand high temperatures.
  • Cover with microwave-safe lid or paper towel to avoid splattering food in the microwave. 
Is it safe to put styrofoam in microwave

Putting Styrofoam in Microwave: Final Thoughts

Styrofoam containers are great tool to transport takeout food anywhere and fulfill your hunger quickly. In addition, with correct microwave-safe symbol, you may safely reheat to-go food for less than a minute

In the current market, it is difficult to find microwave-safe Styrofoam made of a polystyrene base instead of styrene. When these containers are heated in the microwave, styrene may melt and leak hazardous chemicals into the food leading to a potential health risk.

Identify the microwave-safe symbol or label on each Styrofoam box at the bottom before putting them in the microwave. Styrofoam that is #1 or #5 is safe to use in the microwave, but use caution and avoid high heat.

Always adjust the power setting to low and reduce the timing to less than 15 second intervals. Check after each duration and microwave for less than a minute per cycle.

If you see any cracks or breaks in the Styrofoam container, simply throw it away and do not microwave or even store food inside for that matter. The chemicals can release from the opening which can cause harm to your food and health. 

Furthermore, avoid reheating Styrofoam more than one time. Styrofoam is not capable of consistent temperature changes.

When uncertain, replace the styrofoam with a microwave-safe container to reheat you food. It will save your health and time when preparing meal for the day. 

Not all Styrofoam reacts the same way when heating, double check the condition of microwave and adhere to the recommended instructions for microwaving Styrofoam.