How to Test Canning Jar Seals (3 Easy Methods)

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Cooling your jars and knowing how to test canning jar seals are two of the most important steps in the canning process.

A properly sealed jar is what keeps your food safe for long-term storage—so it’s important to check your seals before putting jars away.

If you’re new to canning, be sure to read my water bath canning for beginners guide and see the canning supplies you need here before getting started.

Table of Contents

Cooling Canning Jars

After removing your jars from the canner, allow them to cool at room temperature for 12 to 24 hours.

As jars cool, you may notice:

This is normal.

If a jar loses a significant amount of liquid, do not add more liquid—just check the seal once cooled.

After jars have cooled, remove the screw bands and test seals using one of these methods:

Press the center of the lid with your finger.

Tap the lid with the bottom of a teaspoon.

Hold the jar at eye level and look across the lid.

If a jar didn’t seal properly:

If freezing, you can adjust headspace to about 1½ inches

If you’re learning to can, these guides will help:

You can also browse all of my canning and preserving recipes here for more ideas.

Follow my canning and preserving board on Pinterest.