Can You Microwave Mason Jars? | Answered!

can you microwave mason jars

Mason jars are the glass modelled jars that were initially produced for canning and preserving food. These jars have also become a popular replacement for coffee mugs since they look good, are cost-effective and can be carried anywhere easily. They are now popularly used to store food, drinks, or any other loose supplies or household items. 

Mason jars, though made of glass, are not made from tempered glass and hence can’t withstand high levels of heat, but can be an effective option in case of freezing. These jars are not ideally meant for microwaving and putting in the oven. But modern mason jars are being said to be safe for microwave use. Apart from older mason jars, there’s a whole bunch of things that you should never put in a microwave. You might want to know about them as well.

Are Mason Jars Microwave Safe?

are mason jars microwave safe

There has always been a lot of controversy over the safety of mason jars in the microwave or oven. The glass of the mason jars expands under the heat and can thereby crack or shatter completely. The working of microwaves is such that it doesn’t directly heat the utensils but the content inside. The heat is then transferred to jars. Even with this case of indirect heat transfer, mason jars often tend to crack when put in a microwave. Basic mason jars are not microwave safe, but the modern jars can be made microwave safe although it depends on several other factors. This stays true for microwaves of all types and configurations.

Age is a very important factor in determining the safety of mason jars, since the older jars can easily be shattered under high temperatures. A lot of mason jars also come with the microwave safe symbol while there are a few others which do not have the symbol. Before heating it is critical to establish whether the symbol is there or not. Older mason jars without the symbol should not be used in a microwave. Not in standard countertop microwaves, nor in the over-the-stove or built-in drawer variants, for all of these essentially have the same working principles.

The mason jars are made using annealed glass and it’s possible for them to bear the stress caused by heating and cooling to some degree. Although this should not occur too frequently since it can weaken the glass, and reduce its ability to bear the heat.

How Long Can You Microwave Mason Jars For? 

Mason jars are microwave safe, but a person still needs to be watchful while putting them in the microwave. Since they cannot withstand high temperatures, there is always a looming threat of them shattering. Ideally, mason jars should not be in the oven for more than 5 minutes at a time

Mason jars which have a microwave safe symbol on them can be used easily. The microwave safe is symbol is not consistent for all utensils, however. Read this guide to learn what all signs manufacturers uses to show label a product ‘microwave safe’. However, it is advisable to not put anything in the mason jars that might require long periods of heating. Mason jars can effectively be used in cases of quick heat items, when it is only required to heat them for a few minutes. 

Safety Precautions to Follow If You Microwave Mason Jars 

Most mason jars are now microwave safe, but microwaving the glass makes it pick up some of the heat thereby making it hard to get the jar out of the microwave. Hence, there is a need to be careful during such processes. It is often advisable to proceed slowly, stir the jar often and use baking gloves or a kitchen towel to take it out of the microwave. 

The lids and rings of the mason jars contain metal, and there can be arcing or fire hazards if you put the jar with the metallic lids inside a microwave. They should be removed before the jars are placed in the oven. It is recommended to use only those jars in the microwave that come with the label “microwave safe”. Mason jars with thin walls and older models are very likely to crack and are not meant to extreme temperatures. They should be kept out of the microwave. 

Can You Sterilise a Mason Jar in the Microwave?

can you sterilize mason jars in microwave

One of the most significant uses of putting the mason jar in the microwave is to sterilise it before processing food in it. Sterilising mason jars by putting it in the microwave is better as compared to doing the same on the stove. Before sterilising the jars in the microwave, it needs to be ensured that they are absolutely clean without any specs of dirt. 

It should be cleaned properly by using detergent or soda on the stubborn spots. Any jars that have cracks or are not perfectly cleaned should not be used. The lid of the jar cannot go in the microwave so it needs to be sterilised separately on the stove. 

After being cleaned, the mason jar should be filled with water and heated according to its capacity. For a mason jar of 1 litre or less capacity, 1-2 minutes of heating is fine. For jars with 1 – 4 litres capacity, 3-4 minutes and for those with more than 5 litres capacity, 5 minutes or more will do. 

Can You Microwave Frozen Food in a Mason Jar?

It is highly advisable to not put the mason jars in the microwave when the content inside it is fully frozen. During heating, the temperature of the glass changes rapidly which causes the glass to expand, and this extreme change in the temperature and the structure of the glass can then cause it to shatter. 

Thermal shock is the safety hazard that comes into play when a mason jar with frozen contents is placed directly in the microwave. It could eventually lead to broken and shattered glass. It is always advisable to thaw the frozen contents inside and wait for the jar to reach a more room level temperature before it is put in the microwave so that the glass doesn’t shatter or break. 

If you’re met with a situation where you have some frozen food in a mason jar that requires to be microwaved before consumption, it is best to first thaw the jar at room temperature and only then put it inside a microwave or oven for that matter. To accelerate the thawing process, you may choose to put the jar in lukewarm water.

Are Mason Jars Oven Safe for Baking? 

are mason jars oven safe

Mason jars are not very effective for baking purposes. Since the jars cannot be heated for long, it is advisable to not use them for baking. The oven may get heated rapidly making the jar shatter or pop. Baking in mason jars in this way can be incredibly dangerous. 

Glass used for baking is generally tempered and toughened and is five times stronger than the untreated glass of the mason jars. When baking is done in mason jars, there is a high heat pressure on them. This can result in shattering of the glass. Even if you successfully bake in the mason jar, it may eventually crack if it cools down rapidly. 

Are Mason Jars Dishwashers Safe?

are mason jars microwave safe

Mason jars can be cleaned in a dishwasher. However, dishwashing them repeatedly may scuff their surface and make it rough. In cases of older jars, it is better to hand-wash them, to protect their appearance from deteriorating further. Before mason jars are put straight in the dishwasher, it is advisable to sterilise them before, to ensure proper cleaning. 

The modern mason jars have been designed to withstand the scrubbing and the high temperature of the dishwasher. Their rubber ceilings and lids can also be washed in the dishwasher since they are made to handle the water well. The ultimate safety level of the mason jars in the dishwasher depends on its quality, age, and how well they are handled. Modern mason jars are better in quality, design and size and hence are better equipped than the older ones to be washed in the dishwasher. 


Mason jars are highly versatile and can be used for a variety of purposes around the house from canning to storing food. Since glass is non-reactive, using it for heating purposes is not a very big deal. However, glass may pick up the heat during the microwaving process, and hence needs to be handled with care. 

There are certain things which need to be checked to ensure the safety of mason jars inside the microwave. The metal lid of the mason jar should be removed and it should not be heated for more than a few minutes at a time. Also a jar without the microwave safe label or the jar which is old, should never be used.

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