Can You Microwave Glass?

Can you microwave glass?

I  too often use glass to boil water for tea; for sure, Pyrex glassware works better for me.

This article answers all questions you’d have about putting glass in a microwave and if there are any dangers associated with this action.

We’ll also look at the types of glass that are safe for use in a microwave and  non-microwavable ones. 

Is It Safe To Put Glass In The Microwave?

Even though glass is commonly used in microwaving food products these days, it doesn’t mean that all glass containers are microwavable.

Glass containers are used in the microwave because they’re heat resistant. They don’t leach chemicals into the food when as well. .

Glasses are safe to use in a microwave and are healthy too.

Always remember to check for the microwave-safe symbols or logos at the bottom of your glasses to confirm if they’re safe.

However, if a glass lacks a certified microwave safe logo, that doesn’t mean you can’t use it. 

If in any doubt you can carry out an easy and quick test, (I’ll share with you on your glasses to separate those that are microwave-safe from those that are not) meaning

Though most of the glass containers are safe, some may shatter due to rapid heat changes when heated

How Do You Determine Whether Your Glassware Is Microwave Safe Or Not?

Step 1: Examine the glassware

The first thing you should do is to check your glassware thoroughly. Many manufacturers put logos on their glassware to show they are microwave-safe.

If you purchase a new plate, jug, bowl or cup, take your time to look at it well to confirm any symbols on it.

For example, you’ll find some glassware labeled “safe for microwave use’’ and some written “Safe for microwave use’’.

Alternatively, you may find some information and instructions in the glassware package showing whether the material is safe for heating.

It’s also good to buy your glassware from specific brands such as Pyrex, Anchor Hocking, Corningware, Duralex, and Visions.

Step 2. Fill a cup with water

If you’ve glass, mugs, dishes, or cups that don’t have logos, you can test them.

Before you start, you will require another microwave-safe glass mug. Ensure the mug has a microwave-safe symbol on it.

Next, fill the glass mug halfway with clean water.

Step 3. Microwave the glassware

Next is to set up the heat settings. Make sure the heat inside the microwave is at high levels.

Remember, different products have different instructions. Set heat levels that are safe for your glass mug.

Check your microwave manual to learn how to change heat levels. It’s advisable to do this ahead of time.

Put the glass mug containing water in the microwave plus the glassware being tested next to it, or sit the mug on the glassware.

How you position the two highly depends on your microwave size or preference. Figure out what works well for you.

Step 4: Check the glassware

When your microwave beeps, know that heating time is up. Then get the glass mug containing water and the glassware out.

Use oven mitts to do this.  Once you are done, touch the glassware to check its warmth.

This is what you are targeted to check for;

  • Unsafe for microwave use

If the water is cold and the glassware is warm, then it is unsafe for use in the microwave.

 This is because your glassware will have absorbed the heat. This means it can overheat and break whenever used in the microwave.

  • Safe for microwave use

If the water becomes warm and the glassware remains cold, then it is microwave-safe.

This indicates that water has absorbed heat while glassware hasn’t. This permits you to use glassware for microwaving.

Step 5: Label the glassware

Now that you have completed your test, it means you know which glassware is safe. Label them to avoid confusion.

Use a permanent marker to mark your microwave-safe glassware using symbols, or simply write “microwave-safe”.

This makes it faster and easier for you to figure out which one to use for microwaving in the future.

This saves you time. 

How Long Can Glass Be In The Microwave?

After carrying out the test and identifying the glassware, you can comfortably use it in the microwave.

However, note that you are not supposed to use it for so long in the microwave. Don’t use it for more than three minutes.

You may have various microwave-friendly items, such as glass jars, cups or jugs, which contain different heating instructions.

If this is the case, check their labels and manufacturer instructions to confirm how long they should be microwaved. 

What Happens When You Put Glass In The Microwave?

It’s important to be aware of the type of glass before using it in the microwave.

Ordinary toughened glass containers are only used for heating for a very short time, at most 3 minutes. 

The glass container will explode under high temperatures.

Delicate glass containers cannot withstand high temperatures. They are most likely to crack when exposed to intense heat.

Curved and crystal glass products  will burst when heating fatty food because of their uneven thickness.

Sugar and fat-rich food products require to be heated at very high temperatures compared to water-based foods.

 Be mindful to eat foods with a lot of sugar and fat cautiously.

Why Does Glass Break in the Microwave?

Glass containers are the best for microwave use, unfortunately, not all are safe. Some end up breaking when exposed to intense heat.

The types of glasses that are unsafe contain air bubbles that expand during heating.

Increased heat makes the glass material stretch unevenly, and will eventually break.

When the stress is so strong and unbearable, it causes the glass to break. 

Embellishments and decorations also contribute to the structural integrity of a glass container.

Some glass containers contain a metal layer making them unsafe. During heating, the metal sparks, and your glass breaks apart.

A glass container that is microwave-safe but has some cracks on it may break down when used in the microwave.

Again, your glass container may break due to uneven heating.

Note: Avoid microwaving glass containers with gold or silver rims as metal reacts with electromagnetic waves.

What Types Of Glass Can Be Microwaved?


Not microwave safe, if not labeled

Pyrex glassware


Glassware having microwave-safe logos.

Colored glassware

Glassware that passes the microwave-safe test(the test described above)

Glassware that passes the microwave-safe test

Glass containers have silver or gold rims.

Glassware containing foil or metallic trims

Can You Microwave Cold Glass From Freezer?

If you would like to microwave food in a glass container directly from the freezer there are a few things you need to know first.

Allow the frozen food to thaw before you place it in the microwave oven for heating.

After removing the glass container there will be condensation on the top of the food container. Be sure to wipe this away before putting the food in the microwave for heating.

When your food heats at the desired temperature, take it from the microwave using kitchen gloves or a pot holder to avoid burning your hands.

Materials to Never Microwave

Apart from certain types of glassware, never forget other types of materials are non-microwavable. 

For example, metallic and foil containers are not to be used in the microwave to heat food.

Below is a list of materials you should never use in a microwave;

  1. Metallic or foil material
  2. Brown paper glass
  3. Styrofoam plates and cups
  4. Plastic containers
  5. Plastic wraps unless with a logo indicating they are microwave-safe

The Bottom Line

Most glassware is recommended for use in the microwave to heat food. This is because it does not break easily. 

It does not leach harmful chemicals into your food either.

However, not all glassware containers are microwave-safe. Remember to check for the ‘microwave-safe’ logo at the bottom of your container.

If your glassware lacks the safety logos or symbols, test them using the procedure described in this article. 

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