Is it Really Safe to Microwave Glass? Find out the Surprising Truth!

A question that is still on everybody’s minds: can you microwave glass safely? Unfortunately, with so many variable factors, it’s difficult to say if you don’t know what to look out for. 

But in today’s guide, that’s exactly what I’m going to show you! We will take a look at every tell-tale sign that can indicate a microwave-safe glass dish. And, if you are still not sure by the more obvious signs, I’ve included a test you can safely do to decide for yourself.

Once you are confident in your choice, you can make anything from Microwave Eggs to Hot Chocolate.

Can You Microwave Glass?

There is quite a lot to cover on this topic, so let’s jump straight into it!

Can you heat up glass in the microwave? Yes, you can! However, there are a few “only if” statements that go along with it.

The most important thing to remember when it comes to microwaving glass is that not all glass types can be heated for cooking. This doesn’t only apply to a microwave, but to oven-uses too!

So, just because you can heat a mug with boiling water, doesn’t mean it will be safe to use in a microwave. And just because you have an oven-safe glass baking dish, doesn’t mean it is microwave-safe.

This is usually where the misconceptions, and often shattered glass bowls, come into play.

How To Know If Glass Is Microwave Safe?

Now, at first, this may seem like an uphill battle. How are you possibly supposed to know when you can and cannot use glass in a microwave?!

Luckily, with the laws and regulations in place today, they make it SUPER easy. You just have to look out for a couple of things.

Labeling

The first sign is the most obvious as well. If a glass container or bowl can be used inside the microwave, it will be marketed as such.

This can be in the form of packaging or an embossed stamp at the bottom of the dish. This stamp usually looks like a microwave with little heat waves inside.

If the dish doesn’t have a microwave-safe stamp, it IS NOT microwave safe!

Please do not ever use glass dishes with heat if they aren’t supposed to be used with heat. You can get severely injured through cuts and burns when these dishes shatter inside the microwave.

Lack Of Labeling

Now, this may seem obvious, but if there isn’t any stamps or the words “microwave-safe,” it is better to assume that the dish is not safe to be used in a microwave.

You may also sometimes see an oven-safe stamp on the baking dish. But again, this is NOT a microwave-safe stamp, and therefore it shouldn’t be used in the microwave.

And finally, if there is a microwave sign with a cross of some type through it, that obviously indicates that you shouldn’t use it inside a microwave.

If there is no labeling at all, don’t take the risk.

Look Of The Dish

Finally, microwave-safe glass dishes usually have a similar look.

The dish is often quite thick (about 1/8-1/6 of an inch) and has a thick rim at the top.

There should also be NO air bubbles inside the glass, as this indicates weak points that will crack when heated.

The glass container should also not have any plastic or metal attached to it. The only exception here would be a heat-proof rubber or silicone attachment. But it is best to avoid any and all other materials.

Glass Types

Some common glass types that are not microwave safe include colored glass, vitroceramic glass, soda-lime glass, glass with metal or foil decorations or details, and storage containers with plastic or wooden lids.

A safe option to always go for is Pyrex products or any dish made from borosilicate glass.

Testing For Microwave-Safe Containers

If you have any doubts about the safety of a glass dish for microwaving, it’s better to do my test. This isn’t necessarily a foolproof technique but will give you a better idea of how safe it will be and if the container should be heated at all.

What you want to avoid here is a shattered, exploded glass dish. This can ruin your microwave and cause deep cuts and third-degree burns.

That being said, keep in mind that this test might crack thin glassware.

1. To start, fill your room-temperature glass container with cold water. It doesn’t have to be icy, just cold.
2. Microwave the water for 1-2 minutes. 
3. If the container is hot to the touch, it is not safe to use and will shatter. However, if the container is just starting to heat up (or if it is still cold) but the water inside has heated, it is usually safe to use.

Tips And Tricks For Microwaving Glass

• Never microwave cold or chilled glass containers. The sudden temperature change will make the container or dish shatter.
• It’s safe to assume that drinking glasses, thin glass dishes, and glass storage containers are not safe to use in a microwave. Again, unless there is a stamp that says otherwise.
• If you ever doubt whether or not you can use glass in a microwave, do the test I’ve laid out above.
• Make sure you stir the food or liquids as you are heating them inside the microwave. This will help distribute the heat more evenly and prevent you from having to reheat the contents for longer than they should.
• When removing the glass dish from the microwave, don’t forget to use pot holders or a thick towel. The glass gets extremely hot and retains the heat very well.

How Long Can You Microwave Glass?

Try to always keep the heating (especially in glass) under 5 minutes. This will help make sure that you never crack a glass container – even one that is microwave safe.

If you use lower microwave heat settings, you might be able to heat the food for slightly longer. On the defrosting setting, I would still keep it around 10 minutes at the most. 

The glass retains heat well and even when heated at low temperatures, will continue to get hotter and hotter.