Categories: Zero Waste Kitchen

Are Mason Jars Airtight?

When you are at home, you may not throw away all leftover food since this may be an unnecessary waste. Indeed, you can safely store different types of food in your fridge but you need a good storage container like a mason jar. All the same, all storage containers should be properly sealed which brings us to this question: “Are mason jars airtight?

Can you get Airtight Mason Jars? 

The simple answer is yes but there are certain factors that you need to know when you want to buy mason jars for storage of food. There are two types of mason jars made of plastic and glass.

Plastic Mason Jars

Plastic jars are ideal for storage of dry foods like nuts or flour. These jars come with a lid that also has a ring and they are airtight as long as you keep dry food. However, the problem with plastic mason jars is that they are not ideal for canning or storage of hot food. These types of perishable food need an airtight container that is not susceptible to heating.  

The challenge with a plastic jar is that it quickly responds to heat by expanding then later contracts as the contents inside cool. This process of expansion and contraction is not good since it causes the container to lose shape. The lid and ring, on the other hand, lose their firmness which results in air escaping. Such scenario is not good for the storage of perishable food like soup.

Glass Mason Jars

On the other hand, you can get Glass Mason Jars which are completely airtight and they are ideal for preserving food products that are perishable. These jars are also ideal for other purposes like canning homemade products such as spices and herbs as well as jam. 

The glass mason jars are also perfect for storing products like pipe tobacco and coffee where they serve as airtight containers to keep them fresh.  To be airtight, these jars need to be always made of glass and not plastic. As noted, plastic material has its own weaknesses. 

A glass jar comes with a lid that is designed to create an airtight seal. The lid has a rubberized rim that is found underneath the inside part of the lid. The rubberized feature creates an airtight seal when it is pressed upon screwing so that there is no air that can escape from the storage container. 

The other feature is that is the lid of the glass Mason jar has a “popper” in the center which pops up upon opening. This happens when the jar has been pressurized during the canning process when the lid prevents air from escaping.  


Mason jars can be airtight but the level of tightness depends on the type of jar as well as the type of food stored inside. Plastic jars are good for dry food and you can consider glass jars for usually hot and perishable foods. There are different steps that you should take when using glass jars.  


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