Can You Put Glass In The Microwave? Pyrex, Mason Jar, Glass Cup…

Can you put glass in the microwave? You may wonder and have seen this question circulating on the internet, with people giving various answers. Some say that it’s safe to do so, while others warn against it. 

Microwave ovens have been around since the 1940s, and they’re a staple in most kitchens. But that question still attracts many people. Glass is one of the most versatile materials in the world. It can be used for a variety of purposes, from drinking glasses to window panes. 


So what’s the truth? What will be an exact answer? Here we will explore both sides of the argument and provide a verdict on whether or not you should put glass in the microwave. 

Can You Put Glass In The Microwave?

For the most part, yes, but it has to be tempered glass made especially for the microwave.

It is not advisable to put other types of unsafe glass in the microwave. You can read the label of the glass carefully to identify if it will be safe or not to put inside the microwave. Below, you will also see the exact types of glass which are safe for microwaves.

Tempered glass is the kind used for oven doors, it is safe to use in the microwave because it is designed for this purpose. Non-tempered glass can break apart more easily, which means you have to be extra cautious with how you clean and store them after microwaving food on them or using them as a plate cover.

How Do Microwave Ovens Work?

Microwave ovens work by exciting the molecules in food, causing them to move and bump into each other. This causes the food to heat up. The microwaves used in microwave ovens are absorbed by many types of foods including plastics, glass, ceramics, and paper. 

Microwaves pass through metal foil so this type of material should never be used around a microwave oven or in its vicinity when it is on.

Even though there is no danger in touching the inside of a microwave when it’s turned off, if you want to avoid being burned while removing your food from the oven then you should keep at least one hand behind your back while removing it with an oven mitt or towel.

What Types of Glass are Safe in Microwaves?

is it safe to put glass in the microwave?

Now, you already know the answer to the question of “ Can You Put Glass In The Microwave?” So here are some types of glass that are totally safe to use in microwaves:

Pyrex go in the microwave


Pyrex is a brand of heat-resistant glassware. Pyrex products are safe to use in the microwave. According to the company, Pyrex cannot be made from ordinary glass because lead oxide was used as a stabilizer for expansion and contraction during heating and cooling. This caused pieces to explode during heating or cooling if they were made of ordinary glass.

Pyrex is made from borosilicate glass, which was discovered by a French scientist in 1892 and patented in the United States in 1893.

Glassware with labels for microwave-safe

Microwave-safe labels on glassware mean that the product has been tested and found to be microwave safe. Microwaving is meant for heating or cooking, not for storing food. Microwaves do not remove bacteria from food, so containers used in microwaves should be clean before being placed in the oven.

Glassware is designed to be heat-resistant and safe in the microwave, but not necessarily airtight or leakproof. Glassware that does not have a microwave-safe label can still be used in a microwave oven.

Glassware that passes the microwave test

The glass that is made to be used in microwaves is heat-resistant. However, heat resistance for glassware does not equal airtight or even leakproof. Glass with a microwave-safe label means the product has been tested and found to be microwave safe.

Microwaving is meant for cooking or heating food, not for storing it long-term. Glassware that does not have a microwave-safe label can still be used in microwaves. Always be sure to clean glass containers before using them in the microwave oven.

What Types of Glass are Not Safe in Microwaves?

Can You Put Glass In The Microwave?

Glass-ceramics, colored glassware, and glassware with metallic trims are not safe for use in microwaves. Glass kitchen items should be labeled as microwave-safe. If they are not labeled as such, it is advised to play them safely and avoid using them in the microwave oven.

Glass Ceramics

These types of glass are not recommended to use in the manufacture of cookware. Although these materials are capable of withstanding pretty high temperatures and but it can not be put into an oven, broiler, or microwave. 

The downside to these products is that they may cause minor breakage in microwaves due to their material composition which differs from regular kitchen glassware. Regular glassware contains silica while some ceramic glasses contain more alumina than others.

This information should be listed on the product so it will not come as a surprise when you discover your item has broken after microwaving it for a while.

Colored Glassware

These products can work fine in microwaves provided there isn’t too much contrast between the color of the glass and its design. Items that are plain or transparent can be microwaved while those that have dark colors, such as brown or black, should not be used since one cannot see inside them to monitor food while cooking.

Glassware with foil trims or Metallic

It is best to avoid putting glassware in a microwave oven if it has any type of metal coating on its exterior because it could heat up and cause sparks to fly when exposed to microwaves which can lead to a fire hazard. This is because metals reflect microwaves and this causes the waves to bounce back and forth throughout your kitchen appliance until they hit the food you’re trying to thaw out from being frozen.

In turn, this will raise the temperature of the glassware which could cause it to break if the food is not thawed out.

Glassware does not pass the microwave test.

Some manufacturers would label their products as microwave-safe when in reality they are not. Labeling guidelines vary from country to country which means items that are safe for use in one specific region might be unsafe for another.

That is why it’s best to always check the manual provided by the manufacturer of your kitchen appliances before deciding whether or not you can use your glassware inside them especially if you’re using a secondhand item, do not have an original manual, or misplaced the one that came with your product.

What Happen If You Put Glass in the Microwave?

Glass won’t turn into a liquid if you put it in the microwave, however, it can shatter. The glass may shatter if there is a sudden change in temperature or pressure caused by something else that happens in the microwave oven. Or the glass type is not designed to be put in the microwave.

For example, there might be steam building up inside of an empty cup. When you put the cup in the microwave oven to heat the water, the water will turn to steam and press against the already-cool air inside of the oven. 

Since cooler air cannot hold as much moisture as warm air, some of the humid air condenses on your cold cup to release its excess energy. This greatly increases the rate at which your cup cools down.

If you’re, before this process can complete itself, you open the microwave oven to remove your now-hot glass cup, it will shatter.

Another reason for shattered glass in the microwave is when the glass changes temperature too quickly. If you put a cold drink into your hot oven or even leave food out of refrigeration long enough, it can drop below its condensation point.

When this happens, the moisture that’s on the outside of your cup or bowl turns to water vapor and becomes suspended in the air around your vessel. Because there are no greasy substances around these bits of water, everything has been cooked away, they can travel freely through your oven.

When they come into contact with something cold like part of an ice cream container or condensation from inside a vessel, they immediately condense back into liquid water. This causes the pressure inside of the vessel to rise with extreme intensity.

The glass will not convert into a liquid when in the microwave because it cannot absorb any changes in temperature or pressure enough to allow for this to happen. Whether there is no change in temperature, or too fast of a temperature change, the glass will shatter within the microwave oven if something else was to cause this sudden increase or decrease in pressure and/or temperature.

Why Does Glass Break in the Microwave Sometimes?

Glass is solid. In the microwave, energy from the microwaves makes the water molecules in glass move faster and bump into other molecules, including other water molecules. This process is called “thermal expansion”. These collisions make the whole piece of glass vibrate, which can make it crack or shatter.

Thermal expansion occurs for any object that has trapped water inside its pores, even a sponge! That’s why you shouldn’t put a sponge in a microwave oven.

Sometimes the safe microwave labeled glass still brokes in the microwave if it has a crack or chip. Hence, before placing the microwave, you should check the conditions of your glassware first.

Tips to Keep the Glass from Breaking in the Microwave

You use your microwave oven for reheating, melting butter or chocolate, cooking vegetables and so much more. But have you ever had a glass shattered in the oven? What are some tips to help prevent this from happening again?

Tips to keep the glass from breaking in the microwave.

  1. Use stoneware dishes when microwaving food that contains direct heat ingredients such as sugar, cheese, jam, or alcohol. Do not use any container that is made of metal because many metal cans contain acids that could be released into the food during cooking. 
  2. When using stoneware, make sure it is low-temperature resistant (microwave safe). Some people like to use stoneware baking dishes inside the microwave oven.
  3. When cooking food that has a high water content (such as vegetables or pasta), place the dish on a glass trivet instead of directly onto the glass turntable. This will prevent any water from dripping down onto the hot glass tray and possibly creating too much steam, which can cause it to shatter.
  4. You should always let your food stand for about 30 seconds after cooking time is complete before you open the oven door. 
  5. Doing this allows cold air inside to replace the hot air so you won’t be exposed to broken glass if your casserole dish or plate happens to crack while there is still heat tenaciously hanging on in its interior. Although microwaves are impervious to ultraviolet rays, they are very sensitive to cold.
  6. Never place a painted dish in the microwave oven,  this includes most decorated stoneware and pottery made before 1986. Even if it is labeled as microwave safe, the product may have changed during storage or handling so you’ll be safer if you choose another type of casserole dish or serving platter. 
  7. No matter what type of glassware or dishes you use in your oven always checks for any cracks that could cause them to break when heated.
  8. If your plate does break, keep fingers out from behind the glass because broken shards will fly forward from the force of steam being released inside. Clear glass cookware can also dull knives and cutlery stored right next to it in a drawer so be careful when accessing your utensils.
  9. Glassware made with lead tends to shatter more when exposed to heat and cold and is best not used in microwaves because it can easily break into sharp pieces that could cause injury. Although most glassware is marked as “microwave safe” or “oven-safe,” some glasses may still contain lead, so we recommend only using these in microwaves for reheating purposes only.

If you have any questions about the suitability of a particular glass product in a microwave oven, contact the manufacturer. In general, though, it would be wise to avoid buying any glass products from flea markets or garage sales unless you are positive they are microwave safe.

FDA Precautions for Using Microwave Ovens

Microwave ovens are used to quickly cook foods. Although they can be convenient, some safety risks have been identified. The Food and Drug Administration (FDA) recommends the following precautions when using a microwave:

  • * Do not cook or reheat baby formula or baby food in your microwave.
  • * Keep the door closed. Never heat food in an open container, even if you vent it first by opening the lid partway to let steam escape. Some microwaves produce too much energy inside the oven if you keep the door open during cooking. This can lead to overheating of the food and even cause it to catch fire.
  • * Go easy on defrosting. When defrosting food, take it out of its package so that any juices inside won’t be microwaved too long. For best results, place a dish or wrap loosely around the food while thawing in the microwave oven to reduce heat loss.
  • * The FDA recommends using special care with items containing metal, for example, stirring soup with a metal spoon or stirring brewed coffee with a metal stirrer. Metal objects can reflect microwaves and cause sparks, or in extreme cases, may even superheat or melt the food and cause it to burn you.
  • * Foods that have been heated beyond 140ºF (60ºC) should not be eaten such as foods that look like they’re bubbling from their surface while heating. This is because high temperatures can damage vitamins and enzymes. 
  • * Don’t use your microwave oven for anything except cooking food.
  • * If the oven is not working properly, it could cause food poisoning. If you suspect your oven is emitting microwaves at dangerous levels or that there’s a problem with its door or window seals, don’t use it until it has been inspected by an authorized appliance service firm. Also, if your microwave doesn’t have a solid metal door frame and handle, do not use it.

Frequently Asked Questions on Can You put Glass in the Microwave

Will a microwave oven shatter glass that is in the oven when it is turned on?

A: If there are hairline cracks in the glass or chipped areas, they can explode when exposed to high temperatures. For this reason, you should be cautious about using any type of cookware with chips and cracks in it.

If your dish does have a chip or crack, don’t use it in the microwave at all. One expert said he has heard reports of entire sets of dishes breaking after being used in a microwave oven due to having a flaw somewhere in one piece. These flaws could be hidden so always inspect your plates and dishes before putting them into your appliance. 

If you suspect your oven is emitting microwaves, it’s probably best not to use it at all. If your oven door appears damaged or you notice any strange sounds when the appliance is running, stop using this appliance immediately.

How can I determine if my microwave oven leaks microwaves?

A: This may be difficult to detect because most modern microwaves emit very low levels of radiation even when in perfect working order.

However, if you suspect yours does leak microwaves due to damage or visible corrosion inside the cavity where the waves are generated, keep people and pets out of that room when in use. 

You should also unplug the unit and have it serviced by a qualified technician who specializes in microwave repairs since radiation leakage could pose a potential health risk.

Why does a plate sometimes shatter in the microwave when you nuke it for just a few seconds?

A: This seems to happen when too much cold air gets into the oven from opening the door. The sudden influx of extremely cold air makes the water molecules in the dish contract so quickly that they implode, leading to an explosion and shattering of your favorite china. 

Although this only happens occasionally, it is best not to open the door until all of the steam has dissipated inside after cooking so this doesn’t occur again.

Why do some glasses explode in a microwave if there are any cracks in them?

A: If a glassware item does have obvious damage like chips or cracks, don’t use it at all in your oven. Even if your glassware seems to be in one piece, it still might have invisible cracks that could cause it to break during heating. Always inspect your glassware before using it in the oven.

Is there any way I can test my microwave oven for radiation leakage?

A: There are testing kits you can purchase online that measure radiation exposure, but this is unnecessary unless you suspect a problem with your appliance.

If you don’t feel comfortable with microwaves or feel you need more information on how they work, look for books at your local library about understanding electrical appliances and follow all of the manufacturer’s safety guidelines when operating them.

Why do some plastic items melt in the microwave?

A: Some types of plastics can release potentially harmful chemicals like dioxins when exposed to very high temperatures like those generated by microwaves, so it’s best not to use them in this appliance at all. 

When storing plastic bags or wrap (such as sandwich bags or saran wrap), always keep them away from your food items since they could melt onto your food if placed too close to it during a cycle.

Can I reheat a pizza in a glass dish?

A: While it’s never recommended to reheat food in a dish that has already been used for cooking, the high temperatures that are generated by microwaves can cause this type of glassware to shatter. 

If you’re using a microwave oven at work or school, you might consider asking the kitchen staff if they have any pans or crock pots with lids available for heating your lunch instead.

Can I use paper towels in my microwave oven?

A: Paper towels are flammable and could catch fire when exposed to very high levels of radiation like those emitted by microwaves, so it’s best not to use them inside your appliance. The same goes for napkins and tissues-you may want to ask yourself whether there are wastebaskets available nearby so you can collect them before starting your microwave cycle.

Will my dishes heat up faster if I leave the salt and pepper shakers in?

A: Not at all-salt and pepper should never be heated inside a microwave oven as they could cause the glassware to crack, but there is something you can do with them after microwaving your food. Adding these spices turns any liquid that’s been released from the food into seasoning, which makes it easier for those who like lots of flavors to enjoy their meal.

Can I use paper plates in my microwave oven?

A: Paper plates and other types of disposable tableware are flammable and may catch fire when exposed to very high levels of radiation, so it’s best not to use them inside your appliance. Disposable tableware is never recommended in microwaves at all since the high temperatures can cause them to

catch fire or melt into a messy residue that can be difficult to clean up later on.

Can I put glass bottles in my microwave oven?

A: Glass baby bottles have been common for many years and are used safely every day by parents who need a container for heating milk or formula. As long as you know how to safely handle a baby bottle, there should be no problems with putting one inside your microwave oven. 

However, you should always remember that anything else made from glass could shatter if exposed to very high microwaves for too long.


Microwaves have been around for decades, but there are still a lot of people who don’t know the answer to The question of “Can you put glass in the microwave?”. The short answer is yes but not all the glass, you can’t put unsafe-microwave glass in a microwave oven. That Glass container will shatter and cause injury if heated up in a microwave.

Hence, you should be careful when choosing the safe to microwave glass. Make sure the conditions of glass conditions are well. Hopefully, my sharing will be useful for you!

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