Michigan State University Extension
Preserving Food Safely - 01600951


After cooling jars for 12 to 24 hours, remove the screw
bands and test seals with one of the following options:

Option 1. Press the middle of the lid with a finger
or thumb. If the lid springs up when you
release your finger, the lid is unsealed.
Option 2. Tap the lid with the bottom of a teaspoon.
If it makes a dull sound, the lid is not
sealed. If food is in contact with the
underside of the lid, it will also cause a
dull sound. If the jar lid is sealed
correctly, it will make a ringing,
high-pitched sound.
Option 3. Hold the jar at eye level and look across
the lid. The lid should be concave (curved
down slightly in the center). If center of
the lid is either flat or bulging, it may
not be sealed.

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