Are Glass Coffee Mugs Microwave-Safe?

You have to take a lot of precautions when heating glass kitchenware because it’s so fragile. So, are glass coffee mugs microwave-safe? Let’s learn more.

Are glass coffee mugs microwave-safe?
Double-wall glass mugs can retain the heat of the coffee

I love drinking coffee and tea from a glass coffee mug. Being able to see the layers of my cappuccino or get to watch the color seep from the tea bag is a wonderful way to begin my morning. I particularly like the glass mugs with a double wall, which can retain the heat of the coffee as a ceramic mug does.

However, I tend to get distracted in the morning with chores and getting ready for work. As a result, my coffee tends to get cold before I finish it, and I end up putting it in the microwave. Unfortunately, this is how I discovered that not all glassware is microwave-safe.

So, when it comes to determining are glass coffee mugs microwave safe, it depends. Many are, but if the mug does not have the microwavable symbol on the base or the original packaging, you can probably assume that it’s not. 

Can Glass Go In The Microwave?

If you’re like me, you have microwaved glass containers many times before. From reheating leftovers in a glass Tupperware or melting butter in a Pyrex measuring cup for making cookies, I microwave glass fairly frequently without a problem.

That is why I was so surprised when my glass mug shattered in the microwave. In doing some research, I discovered two important facts about microwaving glass. The first is that there are different kinds of glass, some of which handle high temperatures better than others.

The second is that no kinds of glass like sudden temperature changes – which is why you also have to be careful when you put glass containers in the freezer. You might also find our explainer on how to heat up coffee without a microwave helpful.

What Types Are Glass Coffee Mugs Microwave-Safe?

Certain types of glass are more heat-resistant than others. Both tempered and Pyrex glass are designed to handle more extreme temperature changes than normal glass.

Pyrex is made with borosilicate glass. Borosilicate glass has a low coefficient of thermal expansion. This means that borosilicate glass is far less likely to break when exposed to extreme temperature changes compared to regular glass.

Cheaper glassware is often made with synthetic glass. These synthetic glasses typically do not handle temperature change well and will shatter in the microwave or in the freezer. Even just pouring hot coffee into a room-temperature synthetic glass coffee mug can be risky, as the temperature change can shock the glass.

It is also important to make sure that the glass coffee mug you wish to use does not have any plastic, rubber, or metal built into it. Some glass cups have rubber gaskets, such as a travel mug, or metal rims, such as a canning jar. These can melt or spark depending on the material.

Thus, it is important to make sure your glass cup is solely made from glass.

How Can I Tell If A Glass Coffee Mug Is Microwave-Safe?

When purchasing a glass coffee mug, you should first check the online listing or speak with the representative at the store to make sure the mug is microwave-safe. If the mug is made from tempered glass or Pyrex, then you can feel confident the mug is microwave-safe.

Further, many microwave-safe mugs will have a microwave symbol on the bottom. This is typically a simple image of a microwave with a series of squiggly lines. If you see this image on your glass cup, then it is safe to put it in the microwave.

Conversely, some glassware will have the microwave logo with an “X” over it. This logo indicates that the glassware is not microwave-safe.

What If I Don’t Know If My Glass Coffee Mug Is Microwave-Safe?

A man setting microwave to 30 seconds
Microwave this cup of water on high for 30 seconds to a minute

I have a few glass cups in my cabinet that I like, but they don’t seem to have a microwave-safe symbol on them. I was curious if there was a way to figure out if these glass cups are microwave-safe. I discovered there is a simple test to help determine if your glass coffee cup is safe to use in the microwave.

To begin, start with your glass coffee cup at room temperature. Fill it halfway with cold water from your sink. You are going to microwave this cup of water on high for 30 seconds to a minute.

After microwaving the cup of water, you will take the glass cup out and check the temperature of both the glass and the water. If the glass is as hot or hotter than the water, then the glass cup is not microwave-safe. If the glass is cooler than the water, then the glass cup is likely microwave-safe.

If the glass cup itself gets hot in the microwave, this indicates that the microwave is actually heating the cup itself. If left in the microwave for too long or used in the microwave too many times, then this kind of glass cup is likely to break. If the cup does not get hot in the microwave, this indicates it is made of heat-resistant glass that is able to withstand heat.

You can use this method to test any glassware. Essentially, if the glass itself has started to get hotter, this lets you know that if you microwave it for too long, the glass will break. However, this is just a simple test.

If you are unsure if a glass is microwave-safe, it is always best to exercise caution.

Choosing The Right Glass Coffee Cup

Now that we have figured out that not all glass is microwave-safe, we can figure out the best glass coffee mugs to add to our collection. There are a few general considerations.

Make Sure The Glass Is Heat-Resistant

First, as discussed, we want to make sure that the glass is heat-resistant. For example, the Bodum Bistro Coffee Mug 

Bodum Bistro Coffee Mug
$33.99 ($17.00 / Count)
  • Made of mouth-blown borosilicate glass known for its insulating qualities.
  • Double walled to keep drinks cold or hot for longer. Eat resistant glass
  • Dishwasher, microwave, and oven safe up to 350°F.
  • 10 oz. Capacity.
  • Set of 2 mugs.
  • Shatter Proof: No


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02/10/2024 07:14 pm GMT
is made with borosilicate glass, so we know that it will be microwave-safe. These Libbey Robusta glass coffee mugs are made from soda-lime glass, which is not microwave-safe.

It is important to ensure the mug is made from the right kind of glass.

Libbey Clear Glass Coffee Mugs
$20.99
  • Ergonomic Shape: With large handles and a wide flat base, our clear coffee mugs have extra stability for all your latte drinking needs.
  • Crystal Glass: Made from crystal glass, our set of cups maintain higher durability than typical glass mugs.
  • Timeless: Their classic and elegant style will show off your refined taste to any guest.
  • Dishwasher Safe: Clean your sophisticated coffee cups with ease!
  • Ideal Care Package: To gift friends, family, girlfriends, boyfriends, workmates, housewarming gifts, parties, and even yourself!


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02/10/2024 06:44 pm GMT

Choosing Single Or Double-Walled Cups

Second, unlike a ceramic mug, glass cups conduct heat very well. This means that the heat of your coffee beverage will heat the glass, both cooling your beverage and making the cup too hot to hold. That’s why many glass coffee mugs are made with a double wall of glass.

The two layers of glass better insulate the coffee, keeping your coffee nice and hot and the outside of the mug cool enough to touch comfortably.

It is important to also determine if a double-wall glass coffee mug is dishwasher safe. Because there are two layers of glass, if the cup is not made well, water can accumulate inside the two layers of glass, potentially leading to breaking. While this double-walled mug from Sweese is microwave-safe, it is not dishwasher-safe.

If you are looking to really elevate your coffee-drinking game, I recommend checking out the Fellow Stagg Tasting Glasses. These mugs combine microwave-safe glass with a sleek design that will fit in with just about any kitchen aesthetic.

Fellow Stagg Tasting Glasses for Coffee and Tea Mug - Handblown Borosilicate Glass, Insulated Double Wall For Pour Over Mug
  • STAGG TASTING GLASSES - Great coffee has finally met its container; Made of handblown borosilicate glass designed with a smooth transition from a double-wall insulated cup to single wall easy-to-sip lip
  • A SUBTLE FLUTED LIP - Glass mug details are essential in taking you on a luxurious coffee drinking journey; Our flared lip design delivers coffee to your entire palate allowing you to taste the full spectrum of the coffee flavors
  • HANDBLOWN BOROSILICATE GLASS - For the coffee connoisseur who enjoys a clean, handcrafted brew; Maintain your coffee's robust, rich flavor by drinking out of a high quality glass mug
  • A GLASS WITHIN A GLASS - The double-walled glass is designed to maintain hot and cold beverage temperatures for an extended amount of time; Stagg Tasting Glasses come in a pair of two 10 oz glasses
  • PERFECT POUR OVER PARTNER - If traditional pour-over coffee is your game, pair Stagg Tasting Glasses with our Stagg [X] Dripper, as it nests perfectly on top of a Stagg Tasting Glass and brews the exact amount of coffee the glass allows (300 ml/10 oz)


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Glass Coffee Mugs For Those On The Go

Holding a glass travel mug
A non-glass sleeve to protect your hands as the mug heats up

Not all of us have the luxury of drinking our coffee at home. Glassware can be difficult to take as we travel since glass tends to heat up quickly and leach the heat out of our beverage. Plus, the risk of dropping and accidentally breaking a glass cup is much higher when we are on the move.

A good glass travel mug has several important features. First, it must be made of tempered glass; that way, it is resilient to being dropped. As I mentioned before, tempered glass is also microwave-safe! As well, it will need a non-glass sleeve to protect your hands as the mug heats up.

Finally, you will need a good lid for sipping the coffee that prevents spilling.

The KeepCup Reusable Glass Coffee Cup is an excellent choice for anyone looking to buy a portable glass coffee mug. With a BPA-free plastic lid and cork sleeve, this mug is effective, stylish, and environmentally friendly. Just make sure to take the cork sleeve off before you put it in the dishwasher!

KeepCup Reusable Tempered Glass Coffee Cup | Travel Mug with Spill Proof Lid, Brew Cork Band, Lightweight
$32.00
  • THE CUP THAT STARTED THE REUSE REVOLUTION: Made from durable tempered glass, designed to be loved and looked after. Use it and join the movement. Reuse it and change the world.
  • BARISTA STANDARD: For the coffee maker. Drafted vessel for the perfect pour, and sits under coffee machine group heads, keeping extraction and crema intact. Volumes replicate industry standard single use cup sizing, for correct coffee to milk ratio, ease of cafe workflow and speed of service.
  • DESIGNED FOR DRINKING PLEASURE ON THE GO: Splashproof, press fit lid that allows room for your nose, while mouthpiece ensures optimal liquid and aroma flow. Lovely to drink from, lid on or off. Lightweight, easy to carry and fits comfortably in your hand and cup holders.
  • DOING GOOD BUSINESS: 1% of all KeepCup revenue is donated annually to protect the environment. Manufactured locally where possible, with all products hand-assembled in our warehouses - keeping jobs in our local community. BCorp certified - we measure to improve social and environmental performance. Single-use free, we help convert people and organisations into committed reusers.
  • HYGIENIC AND EASY TO LOOK AFTER: Plug closure keeps mouthpiece covered when not in use, and has easy assembly for cleaning and care. Handwash to preserve cork band. Independently lab tested to ensure products are free from BPA, BPS, phthalates including DEHP, lead and cadmium.


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02/10/2024 07:59 pm GMT

Invest In High-Quality Products

As glass mugs have become more trendy, more options have shown up on the market. It is best to choose your mugs from a reputable source that lists the actual kind of glass their mugs are made from. If a product listing does not say what kind of glass the mug is made from, it is likely made from synthetic material.

Author

  • Aisling O'Connor

    Aisling is an Irish food and drinks writer and journalist fueled by coffee and herbal tea. She followed up her journalism degree with nutrition studies. Find Aisling on LinkedIn.