Are Mason Jars Microwave Safe? All You Need to Know

Microwaves are a very helpful invention that makes cooking a whole lot faster and easier. However, not every dish is microwave safe; some materials smoke, pop, or even explode. So, can you microwave mason jars?

Mason jars are microwave safe, though older mason jars cannot be microwaved as long as newer ones. Mason jars will still get hot to the touch when microwaved, so they shouldn’t be microwaved for longer than 5 minutes. The lids and rubber rings of mason jars are not safe to microwave.

There are a few things you need to know about microwaving mason jars, such as how long you can microwave them, whether you can microwave the lids or frozen food, and how to tell if a mason jar is microwave safe.

Microwaving Mason Jars

Glass is one of the most consistent microwave-safe materials, but not all glass is safe to microwave. Mason jars are made of glass, but that doesn’t necessarily mean that they are microwave-safe. So, can you safely microwave a mason jar?

Mason jars are considered safe to microwave. However, not all mason jars are as microwave safe as others. While newer mason jars are designed to be as microwave-safe as possible, older ones aren’t. This is why newer mason jars include a symbol saying whether they are microwave-safe, while older ones usually don’t. Older mason jars can be microwaved, but not for more than a minute or two.

Newer mason jars are non-reactive, but they tend to get hot more quickly than many other types of glass dishes. When taking a mason jar out of the microwave, it is important to be careful. Use a hot pad to remove a mason jar from the microwave, or wait a few minutes for it to cool down. You don’t want to burn your hand by trying to pick up a hot mason jar.

Because mason jars do not have as good heat regulation as other glass dishes, microwaving one for too long may cause it to shatter. Small mason jars, or those with less than 1 liter of volume, should not be microwaved for more than 2 minutes. Medium mason jars with 1 to 4 liters of capacity should not be microwaved for more than 4 minutes. Large mason jars, or those with over 4 liters of volume, should be taken out of the microwave before 5 minutes.

If you plan to microwave something for longer than 5 minutes, you should empty the contents of the jar into a different microwave-safe container instead of using the mason jar.

If your mason jar is tightly packed with food, it is probably a good idea to separate the food into another container. At best, the tightly packed food will not heat up as quickly, especially at the bottom and in the middle. At worst, the food and air in the jar may expand outward, shattering the jar.

Can You Microwave the Lids?

So, mason jars can be microwaved, but what about the lid? Can you put a mason jar in the microwave with the lid and the rubber ring screwed on?

While the jar is microwaveable, the lids and rubber rings of mason jars are not safe to microwave. Metal is not safe to microwave, as it will grow very hot because it conducts heat very well. The metal will start to pop and spark in the microwave and may cause a fire, so it is definitely not safe to leave the lid on a mason jar. If you leave the rubber ring on the mason jar, it will melt because of the heat. It can ruin the jar or even melt into the food that is in the jar.

Even if a mason jar lid was safe to microwave, it would be a bad idea to keep the lid on the mason jar while microwaving it. When air is heated, it expands, so the air inside of a mason jar will expand as it is microwaved. It is important that the hot air can escape from the jar. Otherwise, the pressure will build up and the jar will explode. Therefore, it is of the utmost importance that you remove the lid from the jar before you microwave it.

Can You Microwave Frozen Food in a Mason Jar?

Microwaves are commonly used to defrost frozen food so it can be cooked. Microwaves even have defrost settings that defrost food safely and efficiently. Is it safe to defrost or microwave frozen food while it is in a mason jar?

You should not microwave frozen food in a mason jar, especially if the mason jar was frozen with the food. When the temperature of glass changes rapidly, the glass isn’t able to handle the change and will likely shatter. Mason jars in particular, which aren’t as microwave safe as other glass dishes, are definitely unable to handle extreme temperature changes.

If you want to defrost food in a mason jar, try submerging the jar in a bowl of cool water. Using hot water will cause the same problems, but cool water that is warmer than the frozen jar will be able to safely defrost the food. It will take quite a bit longer than defrosting using the microwave, so if you want to defrost it more quickly, try transferring the food to another microwave-safe container and defrosting it.

When freezing food in a mason jar, it is important that you don’t fill the jar past the freeze line on the jar’s surface. This leaves plenty of space in the jar for the product to expand.

How Do You Tell If a Mason Jar is Microwave Safe?

Not all mason jars are totally microwave-safe, and older ones do not come with warnings about whether or not they are microwave-safe. To test if a mason jar is microwave safe, put 1 cup of water in the mason jar and microwave it for 1 minute. If the jar is warm around the water and cool everywhere else, it is safe to microwave. If the jar is hot, it is not safe to microwave.