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Can You Microwave Cold Glass?

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The universality and convenience of microwave ovens can make you believe that you can put almost anything inside it. In just few minutes without any problem your food will be ready. Unfortunately, this is not the case, especially when it comes to cold glass. 

Glass is regarded as one of the best materials to use for cooking. It can withstand high heat and is extremely durable. But what about cold glass?

Even though glass is generally microwave safe, microwaving cold glass is out of the question. Chilled glass will break or shatter when exposed to extreme temperature fluctuations in a high heat microwave.

In fact, there are many dos and don’ts about microwaves. We all known by now that aluminum foil and Styrofoam is an absolute no-go. 

Aluminum foil will produce sparks and can even catch on fire. Styrofoam, on the other hand, will lead to melting and reactions that can taint your food with hazardous chemicals. 

As a result, microwaving glass has become a common go-to for preparing or warming food to avoid any cooking mishaps. But, can you safely microwave cold glass?

Can you Microwave Glass?

Well, the answer to this question will depend on the type of glass and how cold is the glass is.

Glass can be a very durable substance that you can put in the fridge, freezer, and microwave oven. What happens to it will depend on how long it is in for, and what you have placed inside it.

Types of Glass

There are two main types of glass that are found in everyone’s kitchen cabinets. They are either natural and synthetic glass.

Natural glass is quite common and for the most part happens to be safe for cooking in a microwave oven. You can put thick natural glass container in a microwave and it will not crack, break or melt. 

The heat from the oven will not be able to affect the dish if heating quickly. Thus, glass is perfect for warming up food, however you must keep the rule of thermodynamics in mind.

If the container has been in the freezer or refrigerator for a long time, give it some time to warm up before microwaving. 

The molecules in the glass gets frozen when you put it in cold temperatures. As the glass container heats up, the movement of the molecules becomes faster. 

Glass is a good conductor of heat. So, in a microwave oven when it is heated up quickly, the glass is put under stress, resulting in cracking.


In some cases it might even explode, depending on how cold it was when you placed it inside the oven. Thus, natural glass with frost should not be placed inside the microwave directly and you should allow the frost to melt away first.

Similarly, natural glass containers that has gathered condensation in a refrigerator needs to warm up for few minutes before sticking it in the microwave oven. However, it is safe to microwave recently refrigerated natural glass.

Just like natural glass, synthetic glasses is also safe to use in microwave ovens. And just like natural glass, you should give some time to warm up the cold glass before placing it in the microwave. 

Do not put frozen synthetic glass inside the microwave as well. The energy sent out by the oven do not react with the glass, but placing a frozen synthetic glass container can increase the movement of molecules go faster which will result into cracks or explosion.

Is it safe to microwave cold glass?

So, room temperature or slightly cold (recently refrigerated) natural and synthetic glass containers are okay for microwave usage, so long as the glass is tempered before heating. 

But if you are pressed for time and cannot wait for you refrigerated glass dish to warm up, then it will be best to opt for microwave-safe glassware. They have good heat resistance, in addition to being chemically inert, which means it will not react with your food items. 

Not every glass is safe for the microwave oven. Microwave-safe glass containers are usually certified with a logo that is commonly imprinted at the bottom of the glass container. A small image of a microwave with some squiggly lines is the common microwave safe symbol/logo/label to represent microwave-safe glass container.

Unlike normal glass containers, microwave-safe glass containers do not have metal decoration or tiny air bubbles trapped in the glass during manufacturing. 

The air bubbles present in non-microwave-safe can expand upon heating. So, if the air in bubbles expand to a certain extent, the glass may shatter. 

For this reason, recently refrigerated microwave-safe glass with slight to minor condensation can be put inside a microwave and heated on medium power level. If you use a low to medium power level, then you don’t need to wait for the condensation to dissipate. 

Here it is important to mention that frozen microwave-safe containers with frost should be thawed first before placing it in the microwave at any temperature.

Can you microwave cold glass?

Does glass melt in microwave?

Glass becomes molten at temperatures ranging from 900 degrees to 1600 degrees Fahrenheit, depending the type of glass being produced. Standard microwaves are not able to generate that much heat in any length of time.

Due to the tiny air bubbles trapped in a glass container, the container might shatter, crack or explode. But a microwave will not be able to melt glass. 

So, you can microwave cold glass containers (microwave-safe) for as much time as needed and not face any melted glass issue.

How do you microwave cold glass?

If the glass container is microwave-safe, then you can put it in the microwave oven even if it is slightly cold. You have the luxury to heat it up for as much time as you want, just start off slowly and gradually increase the heat level.

You need to make sure that the glass is not too cold. For such types of glass, you also have to make sure that you are not putting it in for a long time. 

So only heat the glassware for a couple of minutes, then stir the contents and continue heating. Stirring will distribute the heat and evenly cook food without extreme hotspots.

Tips to Microwave Cold Glass

If you have a slightly cold microwave-safe glass dish that you need to put in the oven, then there are some things that you should know.

There will be condensation on the surface of the glass container when it is taken out of the refrigerator. It is highly recommended that you wipe away condensation before putting the glassware into the oven.

If the cold glass container is not microwave-safe, then make sure to run your microwave for just few minutes. After few minutes check on the food and see if it is hot as per your liking. 

If not, then give the dish a good stir to breakup the hot and cold pockets. After that again put it back in the oven for few more minutes. 

This way you can make sure that your dish will not form cracks, even if it is not microwave-safe.

Microwaving Cold Glass: Final Thoughts

So, it is safe to say that only microwave-safe glass dishes can be microwaved, even if it is slightly cold. If the glass dish is made up with natural and synthetic glass, then it will be best to avoid putting it directly in the microwave when it is too cold

And do remember to wipe away the condensation with a paper towel to ensure the glass does not break or shatter inside the microwave. Be very careful when you microwave cold glass and gradually temper the surface of the glass to reduce the risk of damage.

It is important to mention that exterior decorations or tiny air pockets within the glass will affect the performance and can lead to potential hazards when heated in the microwave. Therefore, it’s important to stick with the best microwave safe containers that are guaranteed to withstand the extreme heat.

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