Can You Microwave Glass? Read Our Guide Before You Press That Button

Can You Microwave Glass? Read Our Guide Before You Press That Button

Is it ok to put glass in the microwave? It’s a question that modern man has pondered since the invention of the microwave oven. While you may be trigger-happy with the power button, it pays to take a moment to think before you blast. The truth is that not all glassware is safe for microwave use. Luckily, we’ve got you covered. Here’s what you need to know about microwaving glassware.

Step 1: Examine the glassware

First things first, you need to check the glassware thoroughly. Some manufacturers will tell you whether their glassware is microwave safe (this is the easiest way to figure out whether you can put your glassware in the microwave or not). If you buy a new jug, plate, cup, or bowl, take the time to look at it and check for any symbols. 

For example, you may find that the glassware says ‘Safe for Microwave Use’ or—on the other hand—’Not Safe for Microwave Use’. Check the bottom of the item for this information. Alternatively, you may find that there is product information on the box.

You should also look for the microwave-safe symbol on the glassware products. In the United Kingdom, this symbol is squiggly lines that you can find on the bottom of the product. Sometimes, you may find that this is a small picture of a microwave.

It’s also worth looking out for specific glassware brands that make microwave-safe items. These include Anchor Hocking, Duralex, Pyrex, Corningware, and Visions. Of course, should you get a glass Pyrex item, you still need to check whether it’s safe for the microwave. Don’t make any assumptions here. It’s always better to be safe than sorry.

Step 2: Fill a cup with water

If you have thick glass dishes, glass mugs, or glass cups that don’t have any information on them, you can test them. Before you get started, you will need a separate mug that is microwave safe. Of course, you should first check that the mug has the microwave-safe sign. Next, fill the cup up three-quarters of the way.

Step 3: Microwave the glassware

Next, make sure the heat is high on your microwave. The instructions will differ from product to product. You may need to check out your microwave manual to see how to change the heat level. You must do this ahead of time.

Put the mug of water and your chosen glassware in the microwave and put it on for one minute. Then, you can either sit the mug on top of the glassware or next to it. The position will depend on the size of your microwave. You can figure out what works for you.

Step 4: Check the glassware

Do you hear that beep? When the minute is up, it’s time to test the glassware. You should use oven mitts to remove the mug from the microwave. When you’ve done that, place your hand on the glassware to see how warm it is and check the water. Here’s what you’re looking for:

  • Unsafe for microwave use

If the glassware is unsafe for microwave use, the water will be cold, but the glassware will be warm. The reason for this is that the glassware will have absorbed the heat. When that happens, it means that the glassware could overheat and break when you microwave it.

  • Safe for microwave use

If the glassware is safe for microwave use, the water will be warm, and the glassware will be cold. That means the water has absorbed the heat while the glassware has not. That’s good news and should mean that you can use the glassware in the microwave.

TOP TIP: You may find that the glassware is warm where the mug has been on it. If that is the case, you shouldn’t worry about it. It’s no big deal. The heat has transferred from the mug to the glassware.

Step 5: Label your glassware

Now that you know which glassware is safe to use in the microwave, you should label it. Find a permanent marker and use it to write on the bottom of the product. If you want to make it super clear, you could add the microwave-safe symbol to the item.

Labelling your glassware means that you can quickly and easily figure out which ones you can use in the future. It takes just a second to do now but will save you time and effort later. Why not have some fun with it and make up your own symbols? Give it a go!

Next, read our other article to find out the answer to "can you put glass in the oven?".


Now that you know how to check whether your glassware is safe for use in the microwave, let’s take a look at some frequently asked questions. Before you use your products in the microwave, it’s smart to know all of the facts. Here are some things that you should know first.

How long can glass be in the microwave?

When you have checked that your glassware is microwave safe, you can use it in the microwave oven. However, you should note that you don’t want to put it in there for too long. The general advice is not to microwave glassware for more than three minutes.

If you have specific microwave friendly items — such as glass jugs, glass cups, or glass jars — they may have separate instructions. If that is the case, you should check their labels to see how long you can microwave them for. Simple.

Can you microwave glass Tupperware?

Most of the time, glass Tupperware is safe for the microwave. However, this may vary from product to product. With that in mind, you need to make sure that you check your collection. Glass food containers are not always safe for the microwave.

Can you microwave glass baby bottles?

Some glass baby bottles may be microwave safe. You should check each individual product before you use it in your microwave oven. Despite this fact, it is not wise to heat baby milk in the microwave. These appliances don’t always heat things evenly.

That means that the milk may be hot in some areas and cooler in others. When you’re feeding a small child, you don’t want to take any risks. Instead, you can get specific bottle warmers to heat your baby milk. That way, you can be 100% sure that it is evenly heated.

For more information, you should look at the info on Baby Centre. You can find advice on how to heat your baby’s bottle and ensure it’s safe for your small child. 

Are mason jars microwave safe?

The answer depends on how old the mason jar is. Newer glass jars tend to be microwave-safe, while older ones may not be. To figure out whether your mason jar is safe to use in the microwave, check for the microwave-safe symbol. If you don’t see it, you may want to avoid heating it in the microwave.

How do you know if a container is microwave safe? 

Before you put your glassware in the microwave, you need to see whether it’s safe to do so. There are a couple of ways you can tell. First of all, you should look for the microwave-safe symbol on the bottom of the product. In some cases, you will find that the glassware has ‘microwave safe’ written on it somewhere. Should you see either of these things, you can be sure that the product is safe to use in the microwave oven.

Of course, if you don’t see the symbol or ‘microwave safe’ note, you need to test the product for yourself. As described in this guide, there is a simple way to check whether glassware is microwave safe. First, you put the glassware in the microwave along with a cup of water. If the product comes out warm, it’s not safe to use in the microwave. That’s because the glass has begun to absorb the heat from the microwave.

Can you microwave plastic?

It’s a bad move to microwave plastic. There are two reasons for this. First of all, many plastic products will melt at extreme heat. That means that a glass tub may turn to mush if you decide to put it in the microwave oven. Don’t make that mistake.

The second reason is that plastic is full of potentially harmful chemicals. So—even if you can microwave some plastic containers—doing so could hinder your health. For that reason, it’s always wise to use microwave-safe products rather than reheating plastic.

Can you put a Nutella jar in the microwave?

Fancy some gooey chocolaty goodness? You may think that popping the whole jar of Nutella in the microwave is a brilliant idea. However, doing so could be dangerous and will melt all of your spread. Instead, take the amount of Nutella out that you need and heat it in a microwave-friendly dish or cup.

Find our tips helpful? Let us know in the comments below!

Joanne A


Expert in finding beautiful solutions for small and rented spaces. Would happily spend the rest of my life shopping for homewares and watching Disney movies - I only wish I had Cinderella's army of mice to help me clean!

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