Can glass go in the microwave? Microwaves are godsends! They’re so convenient when it comes to heating leftovers. But with convenience comes challenges.
For microwaves specifically, containers have to be appliance safe. In this blog, we’ll be answering if you can put glass in the microwave? Is it safe?
What types of glassware are unsuitable for microwaves?
It is generally safe to microwave glass. It’s more stable than microwave-safe plastic or take-out containers.
That being said, there is some science that you need to be familiar with and some dos and don’ts.
Can Glass Go in the Microwave?
Microwaves work by emitting rays, which cause the water molecules in foods or beverages to start vibrating.
The increased friction from the vibrations generates heat, which warms up the food. Glass that hasn’t been appropriately reinforced might begin to heat and expand.
According to scientists, glass isn’t exactly solid or liquid—it’s a state of matter in its own right due to its unique properties.
Glass is often referred to as an amorphous solid or rigid liquid because its particles don’t flow freely like with liquids, but nor do they form any fixed shape as the atoms aren’t held rigidly together.
This is why glass that isn’t reinforced can start behaving similarly to water in the microwave.
There are ways to test for yourself if your particular glassware can withstand microwaves.
Try heating it for a minute or two at a high-power setting and then feel the container’s temperature.
If it’s anywhere between mildly warm and cool, it’s probably going to be safe to microwave with food.
Can You Put Glass in The Microwave – Some Concerns with Heating Glass
If glass starts to show tiny air bubbles, it is probably not suitable for microwave use as these air bubbles could expand enough to shatter the glass.
Glassware with metal finishing, such as around the edge or on the handles, should not be used in your appliance. Sparks from the metal could shatter the glass and ruin your microwave.
Another thing to look out for is dyes. If your glass is colored instead of transparent, you need to check its label to see if it is safe to microwave.
The pigments used could leech into the food if microwaved on high power for a long time.
Types of Glass
Another way to understand can glass go in the microwave is by identifying its types. In the United States, all glasses undergo tempering treatment, making them more robust and microwave resistant.
This is why glass won’t break into chunks in the microwave. Nonetheless, here are the different types of glassware that one would find in almost all kitchens.
1. Natural Glass
It’s a mistake to think the glass is man-made when, in fact, glass is found in spades across the world in different forms.
Glass is typically formed when sand or rocks are heated to high temperatures and left to cool immediately.
An example of this is obsidian or volcanic glass, which forms when molten igneous rock cools quickly.
Cookware made from natural glass is microwave safe as the heat doesn’t affect them. Still, it’s a good practice to check the label and take needed precautions.
2. Synthetic Glass
Synthetic glass is manufactured in laboratories to the specification of its purpose.
If they’re going to be used for cooking or reheating, they’re made to be microwave-proof.
The best glassware for home-use is made from one of these two synthetic glass types – Borosilicate glass and Soda-lime glass.
3. Borosilicate Glass
Borosilicate glass is a popular type of synthetic glass built to resist thermal shocks thanks to its 15% boron trioxide composition.
Some glasses tend to crack when the temperature drastically fluctuates, but borosilicate glass can go straight from the freezer to the oven rack without getting so much as a crack on it.
4. Soda-Lime Glass
Soda-Lime glass accounts for a whopping 90% of the world’s manufactured glass, meaning there’s a 9 out of 10 chance you’re holding one.
As a cost-efficient item to manufacture, it has many applications, including reheating food in a microwave.
However, soda-lime glass does not inherit the same toughness and resilience as borosilicate glasses, so you have to be a bit more careful with them when altering their surrounding temperature.
They are subject to expansion or cracking under extremely high temperatures or drastic shifts in temperature—it expands twice as fast as Borosilicate glass.
What Is Pyrex?
Pyrex is one of the largest and most respected glass manufacturers in the world—it’s history can be traced as far back as over 100 years.
Pyrex has often been mistaken for borosilicate glass, but that’s not what they exclusively produce anymore.
In fact, the brand name Pyrex has been split and is shared by two different companies.
One goes by the name PYREX (French make), and they only manufacture borosilicate glass, while pyrex (American make) only utilizes soda-lime glass.
Can Glass Go in The Oven?
Ovens work differently from microwaves in that they heat food through convection currents.
This, however, means that glass will be heated to a much higher temperature compared to microwaves.
For that reason, it’s better to stick with the PYREX borosilicate glassware when it comes to baking foods or reheating them in the oven. They’re more durable and catch less heat compared to their counterpart, soda-lime glass.
It’s not that we can’t use soda-lime glass for oven cooking, but a few risks are associated with it since it tends to get really hot. Most professional bakers opt for PYREX glassware instead.
Can glass go in the oven? In short, yes, but make sure you read the safety instructions provided with the kitchenware and follow the time and temperature regulations.
Putting Glass in Microwave – Safety Tips
You can microwave glass, but here are some safety practices to follow to avoid accidents:
Tip #1. Follow the user manual and microwaving instructions provided. It’s improbable that you’ll buy any glass kitchen utensils today that don’t come with these.
Do not heat for longer or at a higher power or temperature than the manufacturer’s recommendation.
Tip #2. Do not microwave any glassware lined with tin foil, plastic or metal handles, or other generally microwave-unsafe materials.
According to the USFDA, only glass and ceramics with microwave-safe labels are safe for microwave or an oven.
Tip #3. Do not heat water beyond its boiling point. This has been known to cause scalding injuries as water beyond a certain temperature can cause their container to explode.
Tip #4. Keep checking at regular intervals during a long reheating or cooking session for any food leaks or damage to the container’s structure.
If you see anything suspicious, stop the session and remove the vessel.
Tip #5. Do not use any glass that hasn’t been tempered or reinforced, only use branded glassware that comes with a label, such as PYREX.
Some Final Thoughts
The answer to your question, can glass go in the microwave, is yes! But before you do, check what type of glass and brand you have on hand.
Do also remember to check temperature settings and cooking durations for a safe and enjoyable microwave experience.
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