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Canning lids

How to Tell if a Canning Jar is Sealed Properly

It's important to check the jar lids are sealed properly so the food doesn't spoil or spill. There are various simple ways to do this

How to Tell if a Canning Jar is Sealed Properly

bright jelly in canning jar

For whatever you’re canning this season, testing to make sure your cans are properly sealed is an essential part of the home canning process.

Protect your food from contamination and extend its shelf life for months by using one of Jar Store’s food canning jars paired with one of the easy methods below to test your jar seal!

Starting the Sealing Process

Sealing a canning jar begins once you remove your jars from the boiling water bath and place them on a countertop to let them sit at room temperature for at least 12 hours. Soon after they’ve been removed, you should hear the canning lids pop or ping. This is the sound of the seals being formed by the inner vacuum in the middle of the lid.

After the canning jars have cooled to room temperature, remove the screw bands and check the seals by grabbing the edge of the jar lid and seeing if it stays put.

Canning jar lids

Testing the Jar Seals

It’s important to check the jar lids are sealed properly so the food doesn’t spoil or spill. There are various simple ways to do this, just make sure you’re testing the jars once they’ve cooled!

Method 1:

Press down on the center of the lid with your finger. If the lid does not spring up when you release your finger, that means the jar is sealed correctly.

Method 2:

Gently tap the lid with the bottom of a teaspoon. If sealed properly, it should make a sharp, clear ringing sound. If it makes a dull sound the lid is either not sealed properly or there is food up against the underside of the lid.

Tip: Leaving headspace, or 1/4-1/2 an inch, between the contents of your jar and the lid is recommended by the United States Department of Agriculture.

Method 3:

Hold the jar at eye level. The center of the lid should be concave or slightly turned inwards. If the lid is completely flat or bulging, it may mean it’s not sealed.

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What if Some are Not Sealed?

If you try one of these methods and it turns out some of your cans are not sealed, don’t stress! You can either refrigerate the food and use it within two to three days, freeze it to last even longer, or reprocess it.

Reprocessing Canning Jars

If a lid fails to seal on a jar, first look to see if there are any food remnants, nicks or cracks on the rim. If there are, wipe it off or change the jar out accordingly. Then, repeat the sealing process within 24 hours.

Jar Store’s stylish containers keep outside liquids and other elements from contaminating your product inside. From small jelly jars to extra large canning vessels, our food storage container selection is sure to have what you’re looking for.

Canning jar with lids


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