Can You Microwave Mason Jars? (why or why not?)

Mason jars can be fantastic containers for storing just about anything, including food. What if you want to microwave something in a Mason jar—are Mason jars microwave-safe?

You can microwave Mason jars. Mason jars are made of glass, and glass is almost always a microwave-safe material. However, if the lid of the Mason jar is made of metal, you cannot microwave the jar with the lid on. Also, be aware that old or poor-quality Mason jars may shatter in the microwave.

What are Mason jars?

Mason jars are also known as canning jars. The name “Mason” comes from the American tinsmith John Landis Mason who patented the original design. The jars were intended to make at-home canning or preserving food easier. Before refrigeration, preserving food such as fruit, vegetables, and the meat was essential in order to have enough food for the winter. 

As time went on, the term “Mason jar” no longer referred to that particular brand of the jar but came to mean any kind of glass jar with a lid that could be used to preserve food.

Why are Mason jars microwave-safe?

Mason jars are intended to be used to preserve food. During the canning process, the jars are boiled in water to kill any bacteria present in the food—this means the jars must be able to withstand high temperatures for prolonged periods of time. For this reason, Mason jars (at least the glass part) are usually fine to go in the microwave. Plus, glass is generally a microwave-safe material anyway. 

However, Mason jars aren’t made entirely of glass. They typically have a metal lid—obviously, this part of the jar can not be microwaved, so you’ll need to leave the lid off. Some Mason jars have a glass lid that is fastened to the rest of the jar with sturdy metal wire—you’ll need to completely remove this part of the jar before microwaving it.

If you want to microwave a Mason jar with the lid on, you’ll need to look for specialist Mason jars that come with microwave-safe lids—these are usually made of microwave-safe plastic. Or, you can separately buy microwave-safe lids for Mason jars (link further down).

Some Mason jars have a microwave-safe symbol on them. This can usually be found on the bottom of the jar—look for three wavy lines (possibly inside a rectangle) or the actual words “microwave-safe”. If you find this, you know for sure your jar is microwave-safe.

Why might a Mason jar not be microwave-safe?

Mason jars have seen a resurgence in popularity in the past decade or so. With so many jars being produced by so many manufacturers, the quality of some jars is questionable. Cheaply made and/or thin Mason jars may not fare well in the microwave, particularly if they are repeatedly microwaved.

Glass can break due to repeated heating and cooling, particularly if there are air bubbles inside the glass (more common in low-quality Mason jars). Because air expands when it is heated, air bubbles could cause your Mason jar to shatter.

Additionally, if the manufacturer warns against microwaving their jars, you should listen to this advice as it’s probably given with good reason.

6 tips for microwaving Mason jars

1. Don’t microwave very old Mason jars. They are more likely to shatter.

2. Don’t put cheap Mason jars in the microwave. Particularly if there is no microwave-safe symbol on the jar.

3. Don’t microwave any metal components of the jar. Sparks will be created in the microwave and could start a fire.

4. Only use microwave-safe lids. If you want to microwave a Mason jar with the lid on.

5. Never completely seal a Mason jar when microwaving it—steam given off by the food could cause the jar to explode.

6. Don’t microwave food from frozen in a Mason jar—this strains the glass too much. Instead, put the jar in a bowl of cold water (the water should cover or almost cover the jar) and microwave.

4 popular microwave-safe Mason jars and accessories

1. 6-pack of Ball wide-mouth Mason jars (16 oz)—these durable Mason jars are completely airtight and come with lids and bands. They are rated microwave, freezer, and dishwasher-safe and even come with a grippy jar opener.

2. 6-pack of Ball regular-mouth Mason jars (8 oz)—these smaller Mason jars are also airtight and come with lids and bands. They are microwave, freezer, and dishwasher-safe and come with a jar opener.

3. 6-pack of Urban Platter Mason jars with silver caps (100ml)—these very small Mason jars are perfect for getting organized in your kitchen. You can use them for storing spices and other small quantities of ingredients. They are fine to go in the microwave, freezer, and dishwasher and come with a jar opener.

4. 6-pack of reusable silicone stretch lids in various sizes—as most lids that come with Mason jars are not microwave-safe, these silicone lids come to the rescue. They are rated microwave and dishwasher-safe. 

Final words

Can you microwave Mason jars? Yes. Mason jars are made of glass and are usually ok to be microwaved. Saying this, glass can become strained in the microwave if it is old, thin, or cheaply made. It’s best only to microwave Mason jars that have a microwave-safe symbol on them.

You cannot, however, microwave metal lids that often come with Mason jars. Check out the links above if you need microwave-safe lids for your jars or want to buy some high-quality Mason jars.