Can You Put Glass in the Microwave? – When To and When Not To

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Glass containers are fantastic for a wide range of uses in the kitchen, such as storing, freezing, reheating, and mixing. Actually, pretty much everything else! Can you put glass in the microwave – this question is completely dependent on the type of glass you have. It is important that you follow a few careful steps to make sure that you have microwave-safe glassware to ensure you practice good microwave safety. To find out how you can do this, keep reading below!

Can You Put Glass In The Microwave? – When To And When Not To

Table of Contents

Why Is Glass A Good Container Material?

Glass makes such a great container because of its sturdiness and versatility. You can do something as simple as boil water in the microwave using a mug.

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Glass is great for withstanding very high temperatures, particularly compared to plastic and styrofoam. It wont react in the microwave the way a metal container would.

Unlike plastic, glass does not stain like if you are reheating tomato-based food (such as bolognese) or curry-based dishes (such as Thai curry). This will cause the inside of your container to stain with the color of the food, making it look permanently dirty.

Plastic will also likely leak some of its chemicals into your food if used to reheat, which does not happen with glass.

Glass-ceramics are also mostly considered microwave-safe. Glass ceramics also hold up very well against heat, and most you will find are microwave-safe.

That being said, glass ceramics come in different thicknesses, so it is important to ensure that your ceramic either has the microwave-safe stamp on it, or you need to test it out before you use it.

Can You Put Glass in The Microwave?

Glass is a really good material for reheating in the microwave, but not all glass is microwave-safe. Be sure to check on the bottom of the container to see if it is microwave-safe, and if it is, you are good to go!

Unsafe glassware may cause explosions in your microwave so be careful. This is also true for glass containers that have decorative rims with metallic paint, or any metal present on them. Do not put these in the microwave.

It is important to check the glass container you are purchasing for its suitability to your lifestyle. For example, if you are buying it to use in the microwave, make sure that it is suitable for the microwave!

1. Can You Microwave Glass Pyrex?

Pyrex glassware can withstand temperatures of up to 1000 degrees Celcius! They are perfect for microwave use.

What makes Pyrex glass microwave-safe is that it has very stable chemical properties and has a good reputation for its acid resistance and high durability.

Guide to Best Handling Practices for Pyrex Glass

Following the Pyrex Safety and Usage Instructions, there are a few guidelines that need to be followed to ensure safe handling of these products:

Avoid Sudden Temperature Change

As with any type of glass, including Pyrex glass, avoid any sudden temperature changes in the glass. Do not add very hot liquid to a cold glass container, or vice versa.

For example, if you are putting cold liquid in the glass dish, that has just come out of the hot dishwasher, make sure that the glass dish has cooled down before adding the cold liquid. The same goes for the other way around.

No Direct Heat

Never apply direct heat to glass, such as a stovetop, naked flame, broiler, grill, or toaster oven.

If you want to melt something, like butter or chocolate, put the food in the glass dish and put the glass bowl into a saucepan.

Before heating your glass, make sure there is a medium that will absorb most of the heat into the glass dish, like whatever you want to heat. This avoids any risks like hot splashing which could cause burns.

Always use Potholder/Protective Measures

When using glass in the microwave, it is going to heat up, so make sure that you keep yourself protected.

Use oven gloves or a tea towel, especially when transporting any heated dish.

Avoid Impact on Glassware Due to Dropping or Knocking

Even though Pyrex glass has been reinforced and is less likely to crack compared to normal glass, it is still glass. It is not indestructible.

Knocking or dropping will cause it to shatter.

2. Can you Microwave Glass with a Lid on?

No, it is important that you do not leave a lid tightened on containers when you put them in the microwave. This can cause superheating of food and explosions due to a build-up of pressure within the container.

This can be dangerous when dealing with hot food because you can get easily burned.

Make sure you are using a lid to remove the sealing clips and place it on top of the container so there are some gaps where hot air can escape. This will help to heat your food more quickly.

3. Can You Microwave Cold Glass?

Microwaving cold glass is a big no-no.

Taking a glass container straight from the fridge and putting it in the microwave is very likely going to cause it to shatter or crack.

For example, you have frozen sausages you want to microwave, but the container has been in the freezer, too. You might be surprised that your dishware cracks.

This is because of the large temperature difference between the two. Rapid heating of glass will cause it to excessively vibrate and shatter due to thermal stress.

Even if you are using Pyrex glass, this is really not good for the container. This exposure to a drastic temperature change will weaken it.

How Long Can You Microwave Glass For?

When using glass containers in the microwave, it’s crucial to follow microwave-safe duration guidelines to prevent overheating and potential breakage. The length of safe microwaving time depends on several key factors:

Microwave Wattage Settings

Higher wattages generate more intense heat. A 700-watt microwave should limit glass to 2-3 minutes, while a 1200-watt model requires closer monitoring with a 1-2 minute cutoff.

Volume and Contents

A larger volume of food or liquid absorbs more microwave energy rather than the glass itself, allowing you to heat more safely. However, empty or nearly empty glass heated for too long can shatter from overexposure.

Glass Thickness

Thicker glass materials like Pyrex have higher heat resistance compared to thinner glass. Sturdy glass bowls or baking dishes can typically withstand longer heating than thinner glass.

Spot-Checking Progress

Regardless of microwave power, food volume, or material, it pays to pause and stir contents periodically, checking if sufficiently hot before returning to finish heating. This helps prevent overcooking from edges inward.

  • Monitor all glassware for signs of weakness, including tiny cracks forming, clouding appearance, or severe hotspots. 
  • Discontinue heating immediately if the glass container feels uncomfortably hot to the touch even with protection.

While microwaves provide speedy cooking convenience, take a conservative approach with glass time limits. Typically for reliable brands, heat glass bowls of food for 1-3 minutes, and mugs or small volumes for 30 seconds at a time. 

How Hot Can a Glass Jar Get Before It Breaks?

When microwaving glass jars, it’s crucial to avoid subjecting them to thermal shock leading to breakage. Most commercial jars for home canning or food storage have published safe microwave recommendations not exceeding 212°F internally. Exceeding this threshold risks dangerous steam pressure buildup.

However, quality borosilicate glass like Pyrex can tolerate brief exposure nearing 300°F before structural integrity degrades. The key is monitoring progress and not overcooking contents way past sufficiently hot serving temperature. For example, heating pasta sauce to bubble and steam is fine, but bringing it to an excessive boil risks shattering the jar.

Why Does Glass Break in the Microwave?

Glassware that has tiny air bubbles in them are not microwave-safe. This is because the air inside these bubbles will expand in the heat.

This can cause the glass to shatter, making them unsafe to use in the microwave.

Any decoration or embellishment on the glass can also because for concern. These may not be microwave-safe.

If the paint on our glass container is metallic, then this is not microwave-safe. Such dishware should not be put in the microwave as this can cause sparks, which could lead to a fire.

If there are cracks or chips in your glass container from wear and tear, then this would also make your container microwave unsafe. The cracks will cause the glass to heat up unevenly, expanding at different rates, and causing your glassware to shatter.

How to Ensure Your Glassware is Microwave Safe

There are a few different methods you can try to ensure that your glassware is safe to use in the microwave.

Just follow these tips below:

1. Look out for the microwave-safe label

An obvious one to start off with, but review the underneath of your container to make sure that your glass container is microwave-safe.

Any sign stating ‘safe for microwave use’ or ‘microwave-safe’ is perfect, and the manufacturer has checked that it is suitable for microwave use.

Can You Put Glass In The Microwave? – When To And When Not To

If your container doesn’t have a microwave-safe label, this doesn’t completely rule out that it can’t be used in the microwave. You can try the second option in this situation.

2. Trial Run

If your container doesn’t have the microwave-safe label, you could try a trial run to see if it can withstand going in the microwave or not.

  1. Set your microwave to the highest power setting that it goes to.
  2. Fill a separate microwave-safe container fill it to three-quarters full and place this container into the microwave.
  3. Put the glass container in the microwave. If it is small and you can fit the two containers next to each other, do this. If the glass container is large, then put the container with water into the glass container but don’t get any water on the glass container.
  4. Set the microwave to one minute and start.
  5. Once finished, check the water temperature. If the glass has retained all the heat and the water is cold, then the glass container is not microwave-safe. If the glass is warm or only has a little heat in it, and the water is hot, then the container is microwave-safe.

This test is a handy way for you to be fully sure that your containers are safe. It’s particularly handy if you have young kids who are heating up foods on their own, so you can be fully sure it’s safe for them too.

3. Label Your Glassware

Once you have tested your glassware and confirmed that it is indeed microwave-safe, it is crucial to properly label it for future use. This will prevent any confusion down the line.

The best approach is to use a permanent marker or etching tool to mark your glassware with the phrase “Microwave-Safe.” Write this on the bottom or along the rim of the container. Alternatively, you can purchase reusable microwave-safe stickers or tags to adhere to your now proven glassware. Having this clear microwave-safe identification will ensure no one accidentally tries microwaving untested containers. Proper labeling is a simple yet critical final step after you have vetted that your glassware can withstand the microwave without issue. It streamlines the process for hassle-free reheating.

Microwaving Colored Glassware

When reheating foods in colored glassware, safety depends on the glass type and colorant formulation. Darker opaque glass tends to resist breaking better than light see-through versions which may overheat faster.

  • Opt for lead-free dishes marketed as microwave-safe.
  • Confirm safety by microwave testing new colored containers for 1 minute maximum before regular use. 
  • Also, frequent high heat and alkaline dishwasher detergents can degrade colored glass over time. For best care and to preserve vibrancy, handwash with moderate-temperature water and mild detergent instead. 
  • Stay cautious with uncertain glassware and default to lower microwave times. 

Can You Microwave Glass Baby Bottles?

Microwaving glass baby bottles are generally not recommended due to safety concerns: 

  • Rapid, uneven heating can create hot spots that burn the baby’s mouth 
  • The bottle’s components may also leach chemicals when microwaved

However, if desperately needed, you can microwave a glass bottle for no more than 30 seconds at 50% power. Check the temperature before feeding and avoid drastic temperature fluctuations that can shatter glass. 

Better heating options include bottle warmers, running warm tap water, or placing bottles in warm (not hot) water. Never microwave bottles with nipples or caps on.

Sterilizing Glass in the Microwave

Using your microwave is a quick and convenient way to sterilize glassware, containers, and utensils. When done properly, microwave sterilization eliminates bacteria just as effectively as other methods.

How to Sterilize Glass in the Microwave

Follow these steps for safe microwave sterilization of glass items:

  1. Wash the glass thoroughly with hot, soapy water first. Rinse away any soap residues.
  2. Fill the glass with plain water until around 3⁄4 full. The water helps distribute microwave heat evenly.
  3. Microwave the glass for 2-3 minutes at full power. Time depends on microwave wattage and volume of water.
  4. Use oven mitts to remove the sterilized glass carefully. Water should be steaming hot but not boiling over.
  5. Allow the glass to cool fully before emptying the hot water into the sink.
  6. Repeat steps 2-5 to sterilize multiple glasses. Adjust microwave times if needed.

Microwave Sterilization Precautions

When sterilizing glassware, beware of thermal shock causing breaks or cracks. Follow these precautions:

  • Make sure that the glass is free of defects
  • Handle microwaved glassware with care using mitts
  • Cool hot glasses gradually; don’t add cold liquids
  • Avoid putting very cold glass directly into the microwave
  • Use lower power for delicate glassware

Adjust duration based on your microwave wattage, the glass volume, and the amount of water used. 2 minutes at 700+ watts sterilizes most average glasses sufficiently.

The Best Glassware Containers for Use in the Microwave

Below is a super good example of a glassware container that is suitable for use in the microwave.

You can purchase microwave glass Tupperware on Amazon and is pretty cheap too:

Important Things to Know About Microwaving Glass

  1. While there are a few factors to be aware of when using glassware in the microwave, if you have glass that is suitable for the microwave, it will be the best container for you to use in the appliance.
  2. While some don’t have the safety label, it is likely that they will be microwave safe. It will be superior to using a microwave-safe plastic container because plastic will often leak chemicals into your food, or slightly melt.
  3. Avoid heating cheap glass for too long. Their heat resistance may be questionable and could break under high temperatures.
  4. It is also important not to heat frozen foods in a glass container. Or if you’ve taken the glass container out of the freezer this is not suitable to go into the microwave. The extreme change in temperature will cause the glass to shatter.
  5. If you need to microwave cold glass, start off by putting your microwave to a lower temperature setting, while occasionally removing the container to stir, helping to make the heat change more gradual.

Can You Microwave Glass? Be Careful When You Do!

Glass is a really good container to use in the microwave – probably the best if you have the right one.

There are a couple of different ways you can check its suitability, which is useful, particularly for containers that don’t have the microwave-safe mark.

If you have tested a piece of glassware that doesn’t have the microwave-safe mark and seems suitable for use in the microwave, make sure that you don’t leave it in for too long. Or at least give the contents a stir every two minutes, to ensure the heat is being evenly distributed across the glassware.

If you liked this post, let me know in the comments. You can check out some of my other posts I have previously written following the links below:

FAQs Can You Put Glass in the Microwave

Can You Microwave a Glass Jar?

Glass reacts to heat but quite slowly compared to other materials. Generally, glass should be okay to put in the microwave. But you should not put a mason jar in the microwave for longer than five minutes, or there will be a high risk that it will shatter. Check that it has the microwave-safe label before use.

Is it Safe to Use the Glass Plate from the Microwave in the Oven?

No, the microwave glass plate is only to be used at the holding turntable plate for reheating in the microwave. It is not designed as a conducting material accessory to be heated up in a conduction oven.
It is also very expensive to replace this plate if it does shatter, you may need to buy a new microwave.

Can you Microwave Colored Glassware?

While colored glassware looks really good, you should be careful when using it in the microwave. I would recommend against using it, because the colors and additives that give the glass its color may leak into your food while heating. You wouldn’t want your microwaved ramen to have specks or nasty chemicals mixed in!

By Anna

Anna Brooks, the voice behind CooksDream.com, is a seasoned writer and editor with an insatiable love for food. While not a professional chef, her culinary adventures and unique insights have captivated readers for years. Anna believes in the transformative power of food, stating it "feeds the soul." Dive into her writings for a mix of inspiration, entertainment, and culinary wisdom. Author Pinterest Facebook Twitter Instagram YouTube Tumblr Reddit Quora

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