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Coffee Tips

Can You Put a Metal Coffee Cup in the Microwave?

Microwaves are practically everywhere – offices, schools, hospitals, homes, you name it. However, despite their popularity, most people aren’t sure what can go into them and what can’t. So, in this article, we’ll answer the most common question – can you put a metal coffee cup in the microwave?

metal coffee cup in the microwave

A metal coffee cup and other metal items shouldn’t be microwaved. Why? The microwave heat won’t penetrate the metal coffee cup and therefore your coffee won’t warm up. Let’s discuss this in detail.

Can You Microwave a Metal Coffee Cup?

A metal coffee cup is not ideal for use in the microwave. However, the microwave won’t catch fire or blow up as most people believe. The only thing you will notice is that the coffee won’t warm up as required. Microwaves heat doesn’t penetrate through metals. However, microwaves can induce an electric current in the coffee cup if the metal has jagged points or edges.

Usually, metals are good conductors of electricity, meaning that they can transfer electricity between different points. The electrons in metals are usually free to move around. On the other hand, microwaves work by pulling and pushing the electrons around. So, when you microwave a metal coffee cup with sharp edges, tips, or points, the electrons may build up on these points, which leads to sparks. Additionally, if there is anything combustible in the microwave, a fire is possible. Generally, don’t put your metal coffee cup in the microwave.

What Materials Are Safe to Microwave?

Instead of using metal coffee cups to warm up your coffee in the microwave, you can use alternative materials such as glass, ceramic, and plastic. These materials are safe to use in the microwave since the electrons are not free to move around.


Glass is safe to microwave as long as it lacks gold or silver rims. Decorative cups aren’t safe for microwave use. Basically, when it comes to microwaving, it’s important to confirm whether the glass you’re using is microwave safe. Not all glassware is safe to microwave. Check the bottom of the glass mug or container for a microwave-safe symbol.

Also, you can run a test by filling up the glass with water, then microwaving it on high heat for a minute. If the glass is microwave-safe, the water will become hot and the glass will remain cold. On the other hand, if the glass mug becomes hot, and the water inside is cold, then the glass isn’t for microwave use. Unsafe glassware will break when subjected to high temperatures.


Ceramic mugs that have no metal on the rim or other decorative details are safe to microwave. However, check for microwave-safe labels before using any material. Mostly, ceramics are made through clay, and this makes them heat resistant and microwave safe. However, ceramic cups and dishes may be hot to touch after microwaving them. Therefore, be cautious when handling them.


Most plastics are microwave-safe. However, others may be dangerous. While most plastic containers won’t cause a fire, some can release toxic fumes into your drink or food when exposed to high heat. Usually, the majority of plastic cups contain bisphenol A and polypropylene which are harmful chemicals for human consumption.

Additionally, plastic mugs will damage your microwave if they melt. A plastic mug that is microwavable will have a microwave-use label on the bottom. Also, don’t microwave your plastic cup that has a fastened lid on it. Take the lid off and heat the cup with your coffee or drink in it.

Equally important, avoid using old plastic cups for your microwave. Old plastics are affected by high heat releasing harmful chemicals into your drink or food. Also, don’t microwave plastic disposable cups, even if it’s a convenient option.


    1. Can You Put a Metal Coffee Cup in the Microwave?

No. Metal coffee cups are not for microwave use. The stainless steel won’t allow heat through and so your coffee won’t heat up. Additionally, don’t microwave metal coffee cups with sharp edges, tips, or points to avoid sparks and possible fire.

    2. Is a Stainless Steel Coffee Cup Microwave Safe?

No. Stainless steel tends to block heat from microwaving your coffee. Additionally, steel may damage your microwave and cause a portal fire. How? During the heating process, stainless steel coffee cups tend to reflect the microwaves instead of absorbing them. This results in potential fire hazards and sparks.

    3. Can You Microwave a Metal Tumbler?

No. A metal tumbler belongs to the Yeti drinkware that you shouldn’t microwave. Other Yeti drinkware includes mugs, jugs, and bottles that are made from high-quality 18/8 stainless steel. Stainless steel doesn’t allow heat through and therefore the metal absorbs the energy causing it to build inside the molecular structure. The excess energy emerges as sparks, loud popping noises, and intense heat that may result in a fire hazard. Therefore, don’t microwave a metal tumbler or other yeti drinkware.

    4. Is an Aluminum Mug Microwave Safe?

Aluminum containers including aluminum trays work well in both traditional microwaves and ovens. However, when using aluminum containers, remove the lid before use, ensure the container doesn’t come into contact with microwave walls, and only use one container or tray at a time. Aluminum foils are also safe to use in microwaves.

    5. Is a Coffee Cup Microwave Safe?

No. Most paper coffee cups have plastic coatings and wax that prevent them from being microwaved. Additionally, there are risks involved such as getting burned or consuming coffee full of chemicals from the cup. Therefore, paper coffee cups aren’t recommended for microwave use.

    6. Can You Microwave a Tin Mug?

No. Metallic materials such as tin, copper, zinc, and gold are used to make enamel and shouldn’t be microwaved. To put it simply, think of enamel mugs as metal mugs. The same way you can’t microwave metal is the same way you shouldn’t microwave enamel mugs such as tin mugs.

    7. Can You Microwave a Starbucks Tumbler?

No. Despite being made of paper; Starbucks tumblers or cups aren’t microwave-safe. The plastic cup liner inside them makes the cups dangerous to heat in the microwave. Most paper cups aren’t safe to heat in the microwave. Additionally, thermal expansion may cause the tumbler to grow, increasing an imploding possibility.

    8. Can You Microwave a Thermos Mug?

Yes. You can safely microwave a thermos mug without any issues. However, take the thermos lid off and keep in mind that the contents won’t heat up quickly or evenly as with using ceramic mugs, glass, or plastic mugs.

Expert advice: Never run your microwave while empty since the heat has nowhere to go. This may damage the magnetron thus ruining the microwave.


The key to knowing the microwave-safe mugs, cups, or containers is checking for the microwave-safe label. If the label isn’t available, you can run a safety test which involves putting some water into the container, microwaving it for a minute, and checking for results. If the container is cold to touch and the water is warm, the container is microwave-safe. But if the container is hot and the water is cold, then it’s not safe to use in the microwave.

Generally, avoid using metallic cups or containers, melamine, paper cups, stainless steel materials, yogurt containers, and single-use plastic containers such as margarine and butter containers to warm your food or drinks. Additionally, ceramic mugs with decorated rims such as gold and silver rims should be avoided.


Also read: How Long Will a Coffee Can Heater Last?