Can You Microwave Glass?

Some types of dishes can safely go in the microwave, while others will melt, smoke, or explode when exposed to heat. Are glass dishes safe to microwave, or will they be destroyed?

Glass is safe to microwave, and most glass dishes will mention on the label that they are microwave safe. If the label does not say the dish is microwave safe, test it in the microwave carefully. Never microwave cold glass; major changes in temperature can cause the glass to shatter.

Glass is not always safe to microwave, so it is important to be aware of which glass dishes can be microwaved and how to tell if a dish is microwave safe.

Is Glass Safe to Microwave?

Unlike metal and plastic, glass is perfectly safe to put in the microwave. In fact, it is one of the best types of dishes to use when microwaving something. Most people will use a glass plate or bowl to microwave food. This is especially good for leftovers that come in Styrofoam or plastic containers, which are not microwaved safe at all and can damage the microwave or, tragically, ruin your food.

Most glass dishes come with a label that says that they are microwave safe. Check the bottom of the dish or the sticker that comes with it to see if it is microwave safe. Most will have a definitive answer, and that answer is usually yes. If your dish says it is microwave safe, feel free to plop your leftover pasta or microwave pizza onto it and put it in the microwave.

Is There Glass That Can’t Be Microwaved?

Unfortunately, not all glass can be microwaved. There are a few different types of glass, and not all dishes are made in such a way that they can withstand the heat. It is important that you make sure that the glass dish you have actually microwaves safe before using it in the microwave because it won’t necessarily be just because it is glass.

The first thing to do to determine if your dish is microwaveable is to check if the label says it is microwave safe. If the label says it is or isn’t microwave-safe, that is all you need to do to move forward. If there is nothing on the label saying it is or isn’t microwave safe, or if the only label was a sticker that you peeled off and threw away long ago, there is a test you can do to see if it is microwave safe.

To test if a dish is microwave safe, put it in the microwave. Make sure that it is empty. You will also need to put a glass of water in the microwave as well; make sure that it is a microwave-safe glass before. Don’t let the glass of water and the dish you are testing touch. Run the microwave on high for 60 seconds.

After you have run the microwave for one minute, carefully feel the dish that you are testing. If the dish is cool, that means that it is microwave safe and you can now use it to microwave food. If it is warm or hot, the dish is not safe to use in the microwave, so you should find a different bowl or plate to heat up your food. Make sure to be careful when feeling the dish to see if it is hot or cold so that you don’t burn yourself.

Microwave-safe dishes don’t absorb heat very well, so if the glass dish is cool, that means it has not absorbed much heat. Glass dishes may be hot after food is heated up in them because the heat can pass more easily from the microwave to the food or liquid, and then from the food/liquid to the dish. If the dish is hot even when there is no food or liquid in it, it absorbs heat well, and that means it is not safe to microwave for longer than a minute because it may shatter.

When Can You Not Microwave Glass?

Now that you know your glass dish is microwave safe, that doesn’t mean you are off the hook. There are a couple of situations in which you cannot microwave a glass dish, even if it is microwave safe. Do not microwave a glass dish when it is cold or when it is sealed.

Cold Glass Dish

Putting a cold glass dish in the microwave is not safe, even if the dish is microwave safe. When the glass is at room temperature, the heat from the microwave will slowly increase the temperature of the dish, which is perfectly fine. However, if the dish is cold, there is a much larger temperature change. It’s the same reason why you should never pour hot water onto your frozen car windshield. The change in temperature will make the glass shatter.

Having glass shatter while you’re microwaving has some obvious problems; in the best case scenario, you lose a perfectly good dish, while the worst case scenario is damaging your microwave or the shattering glass hurting you or someone else. It is important that you never cause an extreme temperature change in the glass. Never pour hot water into a cold glass dish or cold water into a hot glass dish. These can cause the same problems as microwaving a cold glass dish.

Sealed Glass Dish

It is also not safe to put a glass dish in the microwave when it is sealed. When heated up, air expands, increasing the pressure. If the glass dish is open or has holes in it, the air will have a chance to escape. However, if the container is airtight, the expanding air cannot escape. It will press on the glass until it cracks. A sealed glass dish can also shatter just like a cold one can, so it is important that you remove the lid of any glass dishes or at least leave a place for the hot air to escape.

Make sure to always be careful when microwaving glass and only do it in short increments at a time.