Michigan State University Extension
Preserving Food Safely - 01600951
10/13/97

### TESTING JAR SEALS

        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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