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Is It Safe To Microwave Pyrex?

I’ve had a large Pyrex dish for as long as I can remember, and I absolutely love it! It’s my go-to for nachos, vegetable bakes, and super-stacked lasagnas, but its one flaw is that it’s far too big to fit in my microwave.

So, recently, I decided to buy some Pyrex that would fit in my microwave, just in case I ever need to whip up a tasty meal in a time-sensitive situation, but just as I was about to place the order, I was struck by a thought… Can you even microwave Pyrex?

That dish of mine must have been in and out of the oven thousands of times and there’s not a scratch on it (it’s easy to clean, too), but microwaves are a different kettle of fish, so I took it upon myself to do a little digging, and here’s what I found out.

Can You Microwave Pyrex
Source: Flickr

Is Pyrex Microwave-Safe?

After a quick search online, I discovered that Pyrex is indeed microwave-friendly, giving me the go-ahead to confirm my purchase and officially take my Pyrex obsession to the next level — hooray!

In fact, Pyrex isn’t just microwavable, it’s so resilient that it’s used in laboratories all over the world for scientific research, and if it’s good enough for scientists, it’s good enough for me, but then I got to wondering how the folks over at Pyrex make it so dang strong. It’s just glass, right? Shouldn’t it be fragile?

Well, traditionally, glass is made when silica sand is heated, melted, then cooled, forming a clear, brittle, crystalline solid, but Pyrex glass, on the other hand, is a combination of superheated silica sand and boric oxide. 

It’s this boron element that gives it such a robust, heat- and chemically-resistant molecular structure, but this substance does have limits, limits that you should know about before taking your Pyrex measuring cup for a spin in your microwave.

It’s not the microwaving itself that causes the issues with Pyrex, but the potential thermal shock that may occur after the fact when exposed to sudden temperature fluctuations.

Thermal shock refers to the fallout an object experiences when subjected to two extreme, yet opposing temperatures. When this happens, parts of the material expand at different rates, compromising structural integrity.

For example, when you put a hot pan in cold water, the stress of the uneven expansion will warp the metal. The same principles apply to Pyrex glass, but, as it’s more brittle than metal, the pressure causes it to shatter, burst, or crack rather than warp.

So, if you have a piping hot Pyrex dish straight from the microwave or oven, don’t place it on a cold surface or rinse it with cold water. Neither should you take a Pyrex bowl straight from the freezer and immediately defrost your leftovers in the microwave.

But as long as you follow the manufacturer’s guidelines for usage and keep temperature transitions nice and gentle, you have absolutely nothing to worry about. The microwaving itself causes no harm whatsoever!

Will My Pyrex Dish Melt When Microwaved?

The melting point of Pyrex is 1510° F (820° C), so you’d need a pretty monstrous microwave to get it anywhere close to changing phases. The boron content in Pyrex makes it, by and large, completely heat-resistant.

You can microwave Pyrex, put it in the oven, beneath a grill, even rest it on your stovetop — there is nothing in the home kitchen powerful enough to melt your Pyrex dish!

How Can Safely Microwave Pyrex?

If you really want to make sure your Pyrex dishes, bowls, and cups are safe in the microwave, it’s good practice to gently preheat them a little beforehand. If you can smooth out the temperature transition, you’ll have absolutely nothing to worry about.

Whatever you do, DO NOT…

  • Set your piping hot Pyrex kitchenware down on a chilly surface.
  • Pour steaming hot liquids into a chilled Pyrex product.
  • Microwave an empty Pyrex product.

As long as you take these guidelines into consideration, you and your Pyrex will live a long and happy life together. Every single Pyrex product is as strong as the next, so you don’t need to worry about shopping around for a specialist, microwavable unit — they’re all great. Even their BPA-free plastic lids are microwavable!

That said, there are some aspects of certain Pyrex products that make them much easier to manage than others when microwaving.

A handle, for instance, can be a fantastic addition, as it won’t heat as much as the central body of the product, giving you a safe place to hold on to when you remove it from the microwave.

Thermal shock is, of course, something to keep in mind when using Pyrex with your microwave, but it’s not like your kitchenware is going to explode every time there’s a slight deviation in temperature.

Corning Inc, (the manufacturer) does everything in their power to galvanize Pyrex glass and ensure your safety, which is why all their glass products exhibit thermal shock resistance up to 428° F (220° C).

It’s also widely known that Pyrex can support temperatures from -104–572° F (-40–300° C), making it one of the most trustworthy and resilient non-metal kitchenware products on the market.

Is There A Limit To How Long I Should Microwave Pyrex Glass?

Okay, so here’s the thing… Every piece of Pyrex glass is tested rigorously before it’s released onto the market for consumer consideration — we’re talking roughly 1000 hours of testing.

This means that anything that falls under the category of regular home usage, really won’t come close to the stress imparted on these products during testing, so you can’t “over mic” your Pyrex.

The truth of the matter is that glass (and ceramic) is actually much more suited for a life in the microwave than plastic, as it doesn’t warp over time or soften when heated, so go ahead… microwave it up, my Pyrex pal!

Pro Tips On Microwaving Pyrex

Due to the Boron content, Pyrex is essentially the Superman of glass, but like the man of Steel, it has one weakness, a kryptonite: the basic thermodynamic rules of contraction and expansion.

However, as long as you follow the guidelines for use on the packaging or on the Pyrex website, you can cook up a storm without a care in the world. Just to give you some extra peace of mind, let’s breeze through 3 pro-tips when microwaving Pyrex…

Thaw Frozen Food Naturally Before Microwaving It In Pyrex

Most Pyrex can go straight from the fridge to a low-to-medium heat microwave, but you should always defrost any frozen goods in the container before introducing them to a high-powered microwave oven.

Follow The Guidelines

No one knows Pyrex better than Pyrex, so make sure you read all the instructions on the package carefully and follow them to the word!

Eliminate Condensation Beforehand

Use a kitchen towel to clear out build-ups of condensation on your Pyrex before microwaving it.

Microwaving Pyrex: FAQ

Q: Why Did My Pyrex Dish Explode?

A: The only reason Pyrex explodes is if it goes through thermal shock. This occurs when the glass is cooled or heated at a rapid rate causing localized contracting or expanding that can crack or shatter the glass.

Q: What Is The Highest Temperature Pyrex Can Withstand?

A: Pyrex can be heated safely to a maximum temperature of 425 degrees Fahrenheit. For any culinary activity that ventures beyond this lofty temp, consider using metal kitchenware.

Q: How Do You Stop Pyrex From Exploding?

A: Generally speaking, the best thing you can do to ensure your Pyrex glass doesn’t crack or shatter is to follow the manufacturer’s guidelines.

More specifically, try to keep temperature shifts as gentle as possible. For example, instead of placing a hot Pyrex dish directly on a cold kitchen surface, place a dry kitchen towel down first.

Can You Microwave Pyrex: Summing Up

Even regular glass without any boron in its DNA is suitable for most forms of home microwaving, so it stands to reason that the heat-treated, chemically resistant molecular structure of Pyrex can handle the zap of a microwave remarkably well.

You’ll often hear people complain that their Pyrex “exploded”, but don’t let that scare you away from these wonderful kitchenware products. The only reason their glass pops is that they’re using it incorrectly and ignoring the guidelines on the package.

The moral of this story? Always follow the provided instructions, and everything will be A-okay! If you can’t find the original package, or it doesn’t have any microwave guidelines, you can normally find more info about the product online. Enjoy those leftovers!

Jess Smith