Is Pyrex Microwave Safe?

Is Pyrex Microwave Safe?

By Becky Charles

Is Pyrex Microwave Safe?

So, you're probably wondering, is Pyrex microwave safe? The answer, my friends, is a resounding yes...mostly. You see, Pyrex used to be made of borosilicate glass, which meant that it could withstand really high temperatures and wouldn't break easily.


However, over the last few years, there have been reports of the occasional Pyrex dish exploding in the microwave. That is because Pyrex is made of tempered glass now.


So while it's technically safe to use Pyrex in the microwave, you might want to exercise caution and make sure you're not putting it through extreme temperature changes, which can (in rare cases) lead to thermal shock.


Or you can use a traditional ceramic plate instead, just to be on the safe side.


What is Borosilicate Glass?

Borosilicate glass is made by adding boron to regular glass. It offers several advantages over traditional glass, including its high resistance to breaking and shattering.



What is it used for?

Borosilicate is often used in scientific equipment, such as beakers and flasks, thanks to its durability and ability to withstand extreme temperatures. Borosilicate is an incredibly versatile, durable and heat-resistant material that also works for a variety of kitchenware applications.


Benefits in the Kitchen

It is a type of glass that produces very low thermal expansion coefficients. This means that it will not crack or shatter when exposed to sudden changes in temperature – from boiling hot to freezing cold. Borosilicate glass can withstand temperature changes of up to 300°C, which makes it ideal for use in both the oven and microwave.


Simply put, it is as shock resistant as glass can be. For this reason, Pyrex continues to remain popular over decades since its invention - testament to its flexibility and acclaimed durability against thermal shock. Its low thermal expansion also means that it is resistant to chemicals, so it won't absorb odors or flavors from food.


What is Tempered Glass?

Tempered glass is made by first heating the glass to its melting point, then rapidly cooling it down. This process gives tempered glass a strong structure that makes it more durable than regular glass and suitable for kitchenware applications.



What is it used for?

Tempered glass can withstand temperature changes of over 200 degrees without cracking. It is an important component in devices such as smartphone screens, windshields, and table tops.


Benefits in the Kitchen

Tempered glass is less resistant to thermal shock than borosilicate glass, but still does a pretty good job. It is still quite durable and can hold up well to the high temperatures of a microwave, as long as it does not undergo extreme temperature changes in quick succession.


For example, taking a Pyrex bowl from the freezer and adding boiling water to it would not be a good idea. Remember, water boils at 212 degrees so that's quite a drastic change in temperature for that bowl!


So yes, Pyrex dishes made of tempered glass are generally considered safe for use in the microwave, although some users may still prefer to use ceramic plates instead, just to be on the safe side.


Why Is Pyrex Made of Tempered Glass?

Pyrex was originally made of borosilicate glass when it was first introduced in 1915, but it was later switched over to tempered glass around the 1950s or 1960s. Some people search for vintage pieces because of this.



While some Pyrex is still made of borosilicate glass today, the majority of its pieces are now manufactured using tempered glass instead. There are a few reasons for this switch:


Breaks Less Easily

Tempered glass is a lot stronger and more durable than borosilicate glass. It can withstand impacts that could potentially break regular glass, making it a safer option for kitchenware products.


Safer When Broken

When tempered glass shatters, it breaks into safer pieces than the shards that borosilicate breaks into.


Shock Resistant

Tempered glass is also resistant to thermal shock – the sudden change in temperature from room temperature to boiling hot or freezing cold – just less so than borosilicate.



Some people argue that tempered glass is also easier to clean than borosilicate glass, since it resists stains and doesn't absorb food smells or colors. However, this claim is still up for debate.



Tempered glass is cheaper to manufacture than borosilicate glass.


Is it Safe to Microwave Cold Pyrex Glassware?

It is generally safe to microwave cold Pyrex glass that has been in the refrigerator. It's not a good idea to microwave Pyrex glass that was just in the freezer. The high heat of the microwave can cause thermal shock and shatter the glass. Always be sure to let Pyrex glass sit for a while after taking it out of the freezer before putting it in the microwave.




And it is safe to put hot Pyrex in the refrigerator without fear, but it is best to let it get to room temperature first. And it's best not to put hot Pyrex products or Pyrex that has recently been exposed to high heat on a cold surface like on a rack in the freezer.


Just avoid those drastic temperature changes! Or you can transfer the contents to another microwave safe container.


Microwaving other Materials

Plastics and other synthetic materials may contain chemicals that can leach into your food when heated, so even if something looks like it should be microwave safe, you could still be exposing yourself to materials that should not be ingested. And some containers are not bpa free.


Many dishes also have metal pieces attached to them which should never go in the microwave as this can create sparks which could cause a fire inside your microwave. If you're ever unsure about whether something should be microwaved or not - always err on the side of caution and avoid popping it into the microwave altogether.


Never Put These in a Microwave

As convenient as microwaves are for a quick meal or snack, it's important to remember there are certain things that should never go in one. For example, aluminum foil, plastic wrap, and Styrofoam can all get very hot when put in the microwave and even spark or catch fire.


Not only that, but these materials have toxins like bisphenol-A (BPA) present in them which are released into your food if heated too long. In general it's best to avoid putting any kind of container with an unknown material or without specific directions on its use in the microwave. Quicker isn't always better when it comes to meal prep!


By being aware of what not to stick in the microwave oven you can ensure you'll still be around to enjoy the food once it's finished cooking!


When in Doubt, Use a Ceramic Dish

Whenever you're opting for cooking ware or storage vessels, nobody would blame you if you're feeling a little uncertain. What type of material is going to be the most durable? Will it be safe for the food I'm going to make with it?



The answer to these questions could lie in the use of ceramic dishware - an extremely popular choice due to its versatility, durability and general aesthetic appeal. Ceramic dishes are available in such a wide range of shapes and sizes, so there's sure to be something that looks perfect for your kitchen.


Not only that, but these dishes are very easy to clean and will effortlessly stand up against regular wear and tear. Their non-porous surface ensures that there's no need to worry about germs spreading through them either - meaning your food is always in safe hands when stored in ceramic vessels.


That being said, it's also important to remember not to overload ceramic dishes by putting hot items directly into cold ones; this could cause breakage so take care when handling them. By remembering this however, a ceramic dish could be just what you need the next time you're feeling unsure about which materials can get the job done properly!


So, Should You Microwave Pyrex Glass?



Is Pyrex microwave safe? Yes, Pyrex is safe to microwave. Pyrex is resistant to thermal shock and can be microwaved safely as long as you follow the instructions on the packaging. If you're unsure whether something is microwave safe, it's always best to err on the side of caution and not microwave it.


There are some things that you should never put in the microwave, such as aluminum foil, plastic wrap, and Styrofoam. If you're ever in doubt, just transfer what you want to microwave into a ceramic dish or a room temperature Pyrex dish! Enjoying your meals quickly and easily doesn't have to be a risk!