Can You Put Glass In The Microwave?

Microwave ovens were invented entirely by accident in 1946 when an engineer working on a radar magnetron noticed that a snack in his pocket had melted. Today more than 90% of American homes have a microwave, and it is a convenient and fast way to cook. Knowing what cooking items are safe to use in a microwave can be confusing, so let’s discuss one of the most popular materials: glass and can you put glass in the microwave?

Before putting glassware in the microwave, check that it is microwave safe. Most glassware is safe to use in a microwave as it has a high heat threshold and generally tolerates microwaving well. Avoid microwaving any glassware containing decorative metallic rims or bubbles of air.

While most glassware is fine to microwave, some types may shatter or crack. There are also a few things that you should never microwave using a glass item.

Let’s go through some glass safety tips so you can cook and reheat food in the microwave confidently. 

Can You Put Glass In The Microwave?

If the glassware items you are using are marked ‘microwave-safe,’ then it is safe, and you can go ahead and use it with confidence.

You can usually find a tiny label on the underside of glass dishes or jugs.

Glassware specifically made to use in the microwave often feels thicker and more sturdy than regular glass items. 

While most glass items are safe to use in the microwave, some are not safe.

Some decorative glass dishes or glasses have metallic rims.

In this case, it is not the glass that would be unsafe, but the metal rim could cause sparks inside the microwave, damaging the appliance or even shattering the glass. 

When ordinary glass is manufactured, tiny air bubbles sometimes get trapped inside the glass while it is being cooled down.

If you carefully inspect transparent water glasses, you may spot one. Microwave safe glass is special because it is double-checked to ensure no tiny pockets of air in the glass.

Microwaving glass that contains air bubbles can superheat the air inside the glass, which will cause it to shatter.  

If you don’t see a microwave-safe label on your dish, don’t assume it is suitable.

Not all glass is the same, so before cooking or reheating in an unmarked dish, do a quick experiment to test if the item is microwave safe.

How To Test If A Glass Item Is Microwave Safe

Checking whether a glass item is safe to put into a microwave is a simple experiment. Here’s what you’ll need:

  • The dish you are testing
  • A microwave-safe jug or dish
  • A cup of water

Add the water to the container or jug that you know is microwave safe.

Then put it inside the microwave with the dish you are testing. Please put it on high power for 1 minute.

The container containing the water must not be touching the test container. 

Next, carefully open the microwave.

In this experiment, only the water should have absorbed the heat.

If the surface of the glass dish you are testing is hot, it is not microwave-safe.

Use it as a serving dish or a fruit bowl, but do not use it for cooking in the microwave. 

Can You Boil A Glass Of Water In The Microwave? 

If you need to boil water, use a kettle or boil it on the stove.

Water should never be boiled inside a microwave and definitely not in a glass or cup, even if it is marked microwave safe. 

Heat bubbles in water can’t build effectively inside a microwave, so instead of bubbles releasing heat when it starts boiling, the liquid gets hotter and hotter.

When you finally open the microwave, the glass with the water may look pretty harmless, but the moment you move it, the superheated water can explode, burning you.

Can You Microwave An Empty Glass? 

Starting a microwave with no food or liquid inside is extremely dangerous.

You must never start a microwave that contains only an empty glass.

If it is a microwave-safe glass, it will not warm up at all, and if it is not microwave-safe, the glass could shatter. 

A microwave produces waves that are absorbed by food or liquid, which results in it heating up.

If there is nothing to heat up, those waves have nowhere to go, and the magnetron inside the machine would need to absorb them. 

Running an empty microwave or one that contains an empty glass would result in it either catching fire or, if you are lucky, the appliance would just break.

Never start the microwave unless you are cooking some food or liquid that can absorb the energy being produced.

Can You Put Glass In The Oven? 

Many types of glass are safe to put in an oven, and some are not. Oven-safe glassware is specifically made to withstand high temperatures like those inside an oven. More flimsy types of glass may shatter. 

Safe oven glass is made from thick tempered glass.

That means it is different from regular drinking glasses that should never be placed into a hot oven.

Standard glass, like the kind drinking glasses are made from, is not safe to use in the oven.

It may contain tiny air bubbles or imperfections in the glass, which could cause the glass to break if heated to high temperatures like in an oven. 

Before putting a glass dish into the oven, check if it has an oven-safe label.

Also, keep in mind that even safe glass dishes shouldn’t go from super-cold to boiling hot too quickly.

If the container you are using has been in the freezer or refrigerator, let it warm up to room temperature before putting it into a preheated oven.

The sudden temperature shock could make even safe glass items crack. 

Conclusion

Most glassware is safe to use in a microwave.

If the item you are using is not marked as microwave safe, you can check it by performing a simple experiment by heating water in a microwave-safe dish.

Glassware with decorative metallic edges must never be placed in a microwave.

Glass that is not microwave-safe often contains minute air bubbles that heat up and cause the glass to shatter when microwaved.