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Can You Microwave Glass?(Hilarious Safety Tips)

Is it safe to put glass in the microwave? It’s a debate we often find ourselves in since we throw almost everything inside the microwave. 

In this post, we will expound more on that in a detailed manner. But first, is glass microwave safe?

Although glass is microwave safe, microwaving cold glass is questionable. Some glass containers aren’t microwave-safe – like glass ceramics, glass with metallic trims, and colored glasses. Stick with glass products labeled “microwave-safe” 

Related Post: Can You Microwave Glass Jar?

Is Glass Microwave Safe?

What is Glass?

Glass is a non-crystalline, solid material that is transparent, brittle, and hard. Pie plates and glass casserole are the most common vessels you find in most kitchens. 

Glass is super delicate, but it’s quite a robust tool when it comes to cooking and baking. Below are some of the advantages of cooking with glass;

  • It’s very easy to clean because of its nonporous surface
  • Cooks and heats food uniformly 
  • Glass does not react with food 
  • Most glass containers are microwave-safe
  • It’s extremely durable and can withstand high heat
  • It’s a good conductor of heat

What Type of Glass Can You Microwave?

Below is a review of some of the glasses you can and can’t microwave;

Microwave- Safe

  • Any glass that labeled “microwave-safe” is safe to use
  • Pyrex glassware
  • Glassware that manages to pass the microwave test

Not Microwave-Safe

  • Colored glasses
  • Glasses featuring metallic trims or foil trims
  • Glass-ceramics
  • Glasses that don’t pass the microwave test.

Why Should You Not Microwave Some Glasses?

You’ll find some glasses labeled “not microwavable” and there are reasons for this. For example, it can depend on the chemicals the manufacturer uses, the structure, or even the decorations.

  • Colored glass isn’t microwave-safe. Adding color or dyes to the glassware during the manufacturing process makes it unsafe for microwaving. This is because some of those chemicals leach into the food and can be hazardous.  And that is why colored glassware is unsafe for microwaving.
  • Glass-ceramic is not microwavable. Glass ceramics contain a mixture of ceramic clay.  When you heat such a container then cool it rapidly, the contraction transposes the internal bonds, causing the ceramic container to shatter. 
  • Glassware that has metallic trimmings can easily ignite sparks inside the microwave. Sparks are pretty dangerous as they can damage your appliance, and glass is also more prone to damage from sparks. 
  • Lastly, some glasses are not made to be set in the microwave. For example, those with air bubbles which the manufacturer did not eliminate during production. Such bubbles expand while in the microwave and could cause the container to crack.

How Do You Know If Glass is Microwave-Safe or Not?

You can’t tell if the Glass is microwave safe by looking at it. There are different ways to determine if you can microwave food in it or not. 

First, check for stickers or labels on the container or the packaging that ascertain that the Glass is microwave-safe. If it doesn’t have any labels, there’s a small experiment you can perform to test if it’s safe to microwave.

But remember, if the glassware is ceramic, colored, or has some metallic or foil trimmings, you should NOT perform this test. 

Materials required;

  • Glassware to be tested 
  • A microwave-safe container
  • Water
  • Microwave

Simple steps to follow;

  • Ensure there are no labels on the glassware
  • Set the microwave at the highest power
  • Pour one cup of water on the microwave-safe container
  • Keep the glassware empty
  • Put both the glassware and the microwave safe container in the microwave (if the glassware is a little bigger than the container, you can just set the container in the glassware). Remember to keep the glassware empty even at this point.
  • Microwave the container (with water inside) and the glassware too for about one minute.
  • Cautiously touch the glassware and feel how hot it is.

If the glassware turns out to be hot, then it’s a clear sign that it’s not safe for use in a microwave. Microwave-safe glassware only gets slightly warm. 

If your microwave-safe container is hot, but the glassware is cool, that indicates your glassware is microwave-safe. 

Is It Safe to Microwave Cold Glass?

Slightly cold glass containers or those at room temperature are microwave-safe as long as you temper them before heating. 

However, if you aren’t patient enough to wait for the glass container to warm up a little, it would be best to use a microwave-safe container. 

Can You Heat Water With Glass in the Microwave?

While it may seem convenient and fast to heat water in a microwave, there are some precautions you should consider. 

Unless the glass container is safe for microwaving, then you should not heat water in it. It would be best if you only used the approved containers to boil water in a microwave.

Can You Microwave Glass Jars? 

The simple answer is No! Jars are made of standard glass that can’t be set in microwaves. Since such material can’t handle high heat, it will either explode if put in a microwave.

Bonus Safety Tips

Here are some helpful tips you can use if you’re cooking using glass containers;

  • Don’t put any liquid in hot glassware because it might crack.
  • You should not expose hot glassware to rapid temperature changes
  • Never place empty glassware inside a microwave because it might crack or shatter
  • You should not use glassware to overheat oil or butter  


If the glassware you’re using has a “microwave-safe” label imprinted on it, then you can go ahead and start cooking. If it doesn’t have any, you can perform a simple test to ascertain its safety. 

Avoid using any glassware without colors on it, metallic trimmings, or those made of ceramic Glass. If you’re still unsure about the container to use, go for the one rated safe.

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