Can You Microwave Glass Jar? Is it really safe?

Yes as long as it’s labeled “microwave safe”

Although glass mostly features a thick surface, that doesn’t stop food and drinks from getting cold. And it’s not wise to consume them in cold temperatures.

Warm food has a good taste and flavor that’s absent when cold. Microwaving is one of the most feasible reheating and cooking options.

It’s effective. But can you microwave a glass jar? Let’s find out whether glass is microwavable and how you can use it to extend its lifespan in this short article.

Is Glass Jar Microwave-Safe?

Yes, as long as it contains the “microwave-safe” label, glass can go into the microwave. A microwavable glass jar is designed to handle high temperatures, making it ideal to use in the microwave.

What you should strictly observe, though, is the microwave-safe label. This means some glass should not go in the microwave due to some manufacturing variations.

Some manufacturers might have designed certain glass containers for uses like storage or serving. These glasses could have qualities that may interfere with your microwaving of food.

Glassware that’s not microwavable could have contents of the following:

  • Metal.
  • Dyes and inks.
  • Air bubbles.

Thawing such glass containers puts them at risk of cracking or breaking in the microwave. You don’t want to imagine the damage that could happen when glass containers spill food and drinks inside your microwave.

Drinking glasses and glass food containers with plastic seals should also not go in the microwave. Apart from risking burning, those plastic seals can easily melt into your food and they also pose severe health complications like cancer.

Even worse, you could get your microwave damaged when plastic warps and melts inside. Cleaning out the melts is also a tough task you don’t want to entertain.

Another pro-tip to consider is the coldness of your glass.

While it’s safe to microwave glass that’s slightly cold after refrigerating, it’s never safe to thaw a glass container that’s been in the freezer for a while. 

You must place the latter on the counter and allow it to warm up first before microwaving.

Microwaving an extremely cold glass leads to immense heat fluctuations that can cause it to crack or break. 

If you’re still unsure whether your glass is safe to use in the microwave, you can apply the following microwave safety test:

  1. Fill your glass dish with a cup of water.
  2. Place it in the microwave and nuke for 1-2 minutes.
  3. Check its temperature.
  4. If it’s extremely hot to the touch, then it’s not microwave-safe.
  5. If it’s slightly hot and the water has absorbed heat, then it’s safe to use in the microwave.

How to Tell if Glass is Microwave-Safe

The surest way to check if glass is microwavable is to look for the microwave-safe mark. Alternatively, you can perform the short test and follow the steps outlined in the above section.

While looking for the microwave-safe sign, you should note that manufacturers place these markers on the surfaces of the container in different versions. 

Most manufacturers place the label in the form of a microwave image at the bottom or on the surface of the container. You may also find the image on the product’s packaging or in the product description.

The microwave image is usually a rectangular box with circles on one side, indicating the knob. The other side of the box has a few squiggly wavy lines to indicate the microwaves.

Other glass containers come paired with the word “microwave” or “micro.”

But some glass containers won’t come with the label. In such cases, liaise with the manufacturer to know if your container is safe for use in the microwave.

You can also apply the microwave safety test with the steps indicated in the previous section. 

It’s also worth noting that even a microwave-safe glass container can break or crack in the microwave. Never nuke your glass container for more than 5 minutes even if it’s labeled microwave-safe.

Set your microwave power setting to high and nuke for under 5 minutes to prevent your container from exploding.

Is It Microwave a Glass Jar?

Yes, you can microwave a glass jar as long as it contains the “microwave-safe” label. Glass jars containing tempered glass are also safe to use in the microwave.

The microwave-safe sign could be in the form of a drawing of a microwave with wavy lines or #5. Some manufacturers also label their microwavable glass jars with the wordings, “microwave-safe,” “microwave,” or “micro” on the side or bottom.

Additionally, containers with tempered glass mostly feature a 3 or 5 mark and are microwavable. They may also contain the microwave-safe sign.

Always check for these features before nuking a glass jar. If you microwave a glass jar that’s not microwave-safe, it can break and release harmful pieces.

Glass jars are heat-treated to make them sturdier and lower their chances of shattering. 

To check if your glass jar is safe to use in the microwave, check at its bottom for a circle with a number in or beside it. 

You may find the numbers 3 or 5. Or come across information on the type of glass used to make your container.

Safety tips When Microwaving Glass

It’s imperative to look out for trouble whenever you use a microwave. The best way to stay out of problems with your microwave is to ensure you stick to safety guidelines.

First things first, you must ensure your glass container is safe to use in the microwave before putting it in the appliance. Check for the microwave-safe signs on your container before proceeding with the heating.

After confirming that your glass plate is safe to microwave, there are more tips to consider. Please observe the following safety tips when microwaving glass:

  • Stick to the manufacturer’s instructions.
  • Always close the microwave oven doors when heating.
  • Never turn on the microwave before placing your glass inside.
  • Conduct microwave leak checks regularly. Switch your microwave off, then place your mobile phone in the microwave, and call it on another line. If you hear it ringing, it means your microwave lets out electromagnetic waves.
  • Engage with a technician to have your appliance repaired.
  • Always check if your glass is microwave-safe before nuking.
  • Nuke your glass at a high heat setting for not more than 5 minutes to prevent it from breaking and causing a mess.
  • Always use pot holders or oven mitts to get hot glassware out of the microwave to avoid burning.


What types of glass is microwave-safe?

Microwavable glass includes the following:

  • Pyrex glassware.
  • Glassware that passes microwave safety test.
  • Glassware with a “microwave-safe” mark.
  • Glass-ceramics without metallic paint/ink.

What type of glass is unsafe to microwave?

Never microwave glass containers with the following features:

  • Colored.
  • Vitroceramic.
  • Drinking glass.
  • Glass containing foil or metallic lining.
  • Glass food containers with plastic seals.


It’s safe to microwave glass. But you should always check for the microwave-safe sign before proceeding.

Alternatively, you can test your glassware using the microwave safety test given in this article.

After confirming that your glassware is safe to thaw, always microwave it at a high heat setting for not more than 5 minutes. Nuking glass for more than 5 minutes can cause it to shatter and mess up your microwave with glass pieces and food spills.

Leave a Comment