Can You Microwave Glass? (And How To Tell If It Is Safe)


can you microwave glassMicrowaves have become an integral part of modern kitchens, offering a quick and convenient way to heat up or cook a variety of foods. However, when it comes to using glassware in the microwave, many people are unsure about the safety and precautions involved.

If you’ve ever found yourself wondering, “Can you put glass in the microwave?” or “How can I tell if my glassware is microwave-safe?”, then you’ve come to the right place.

In this comprehensive guide, we’ll address all your burning questions about microwaving glass. We’ll explore the dos and don’ts, the types of glass that are suitable for microwave use, and the potential risks involved if proper precautions are not taken.

So, whether you’re a seasoned microwave user or a newcomer to the world of microwave cooking, this article will equip you with the knowledge you need to make informed decisions about using glass in your microwave.

Can You Put Glass in the Microwave?

Now to the big question: can you put glass in the microwave? The answer is yes and no. I know what you are probably thinking “how can it be both?”

So here’s the thing: glass items that come with the label “microwave safe” can be used in the microwave without issues. But if your glassware doesn’t have the label or you are not sure if it has, it’s better not to use it in the microwave.

However, if you want to use the glassware in the microwave, then there are some tests you can carry out to ascertain if it can be used or not. You’ll find the tests you can carry out in the “Is it Safe to Put Glass in the Microwave” section of this blog post.

Another commonly asked question about microwaving glass is “if it is possible to microwave cold glass.” Again, the answer to this question is yes and no.

If the cold glass was recently refrigerated, it’s microwave safe, and it’s slightly cold, then it can be microwaved – remember to wipe off moisture (or condensation) before placing it in the microwave. But if it’s been in the freezer for a very long time, then you should keep the glass on a counter and allow it to warm up to room temperature before microwaving it.

If you don’t let the glass thaw before microwaving, the extreme heat fluctuations can cause the glassware to break or crack.

How Long Can You Put Glass in the Microwave?

Now you know that it’s okay to use some glassware in the microwave, the next big question is: how long can you leave glass in the microwave?

The general rule of thumb is to keep glass’s microwave visits short and sweet – we’re talking no more than 3 minutes for most pieces. Pushing past that could result in breakage.

If you’re using dedicated microwave-safe glass containers like jars (i.e., glass jar or mason jar) or bakeware specifically designed to handle those microwave electromagnetic waves, feel free to push past 3 minutes if the manufacturer gives you the green light. Just be sure to follow any microwave time instructions to a T.

Is it Safe to Put Glass in the Microwave?

mocrowave safe logo

If you have been reading this blog post, you should already know that it’s safe to keep certain (microwave safe) glassware in the microwave. But what if you don’t know if the glass is safe is not? Probably because you can’t find the label or microwave safe symbol. What do you do in that situation?

To answer that, we need to first understand how glass behaves in a microwave. Glass is a brittle material that breaks into sharp pieces when it shatters. When glass is exposed to an extreme temperature, it shatters.

That happens because when the glass is heated, the molecules move faster and the pressure increases as well. As the pressure increases, the temperature increases along with it until it gets to the point where it exceeds the glass capacity.

When that happens, the molecules separate from their bonds, enlarge and start violently colliding with each other. This goes on until the pressure in the glass makes the glass shatter from thermal shock.

Now you know why or how glass shatters in the microwave, it means you also know that it’s very important that the glass you are about to use is safe in the microwave. But if there’s no way of telling, to avoid breaking or shattering the glass in the microwave oven, you can carry out a test to help you determine if you should carry on or not.

To be sure you have a microwave safe glass or glassware, carry out this test:

  • Pour a cup of cold water into your glass object and place the object or item inside the microwave for a duration of 1 to 2 minutes.
  • After the duration, check the temperature of the glass. If it feels hot, It’s an indicator that the glass isn’t microwave safe. But if the glass is mildly warm or stays cool, then it’s safe to say that the glassware or glass can be safely used in the microwave.
  • However, you should remember to be mindful of the general three-minute duration for glasses in a microwave so you don’t end up breaking or shattering the glass.

Finally, it is important to note that if you place delicate glassware in the microwave to carry out the above test, it may break during the examination. So it’s important to always be cautious when carrying out this test.

How to Safely Sterilize Glass?

Let’s be real – there’s nothing quite as satisfying as sparkling clean glass, fresh out of the sterilization oven. But getting those dishes safe for use takes more than just a quick nuke. We’re talking some serious heat to decimate any lingering bacteria.

The good news? Glass is built to withstand high temps without melting or breaking. Those silicon and oxygen elements – what it’s made of – give it some serious heat-defying power. We’re talking upwards of 700°F before it even thinks about losing its cool.

But every glass has its limits. The key is walking that fine line between “sterilized and spotless” and “shattered into a million pieces.” Follow these steps to safely sterilize your glass without the risk of breaking or melting it:

  • Place the glassware in a metal container and add water to cover.
  • Boil the water for 5 minutes once it boils.
  • Next, carefully transfer the glass to a preheated 400°F oven for around 10 minutes.
  • Once they have been sufficiently heated, remove your clean glass and let it cool off on a drying cloth for 15 minutes.
  • Keep repeating this boil-bake-dry cycle until all your glass pieces are squeaky clean.

Can Pyrex Glass Go In The Microwave?

Pyrex glassware is great for microwaving food. The glass they are made from can handle really hot temperatures without cracking or breaking apart.

Most Pyrex bowls, baking dishes, measuring cups, and containers have a “microwave-safe” label on them. That means the company tested them to make sure they heat up evenly in the microwave without getting messed up or leaving harmful chemicals in your food.

But there are still some things to watch out for when using Pyrex in the microwave:

  • Don’t put really cold Pyrex straight into the microwave. Let it warm up to room temperature first. Rapid temperature changes can cause problems.
  • Never microwave an empty or almost empty Pyrex dish. It can get way too hot.
  • Use oven mitts to grab hot Pyrex out of the microwave. The glass holds heat very well.
  • Check for any cracks, chips, or scratches before microwaving. Damaged Pyrex won’t work as well.
  • Follow any instructions from Pyrex about how long to microwave for.

If you’re careful, Pyrex makes an excellent microwave-safe choice. The special borosilicate glass it’s made from can take lots of heat without shattering like regular glass. So feel free to your Pyrex dishes when you need to heat something up quickly and safely.


At the end of the day, microwaving glass comes down to playing it safe. While certain types of glassware are designed to withstand the mighty microwave, others can turn into a dangerous shattered mess.

The golden rule? Only use glass containers that have a microwave-safe label written on them. These bad boys have undergone rigorous testing to ensure they won’t warp, leach nasty chemicals, or explode when heated. If your glass doesn’t have a safe label, it’s better to be safe than sorry.

For those unlabeled glass pieces, there’s a nifty test you can perform. Simply microwave the item with some water for a minute or two. If it stays cool or just slightly warm, you’re likely in the clear. But if that glass is piping hot afterward, keep it far away from your microwave.

No matter what, try to limit microwave time for glass to under 3 minutes. Anything longer raises the risk of thermal shock and shattering. And if you’re using a specially designed microwave-safe glass container, always follow the manufacturer’s instructions to a T.

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