Once the canning process is complete and the finished
product has cooled, jars should be inspected. Visually, your jars
should pass this test:
Jars have retained proper head space.
Jars are free of air bubbles.
Liquids just cover solids.
Produce is free of imperfections as well as,
stems, cores, and seed.
To physically test the seals, press the center of the
lid down. If the lid does not move, it is sealed. Another way to test
seals is to tap the center of the lid with a spoon. A good seal will
produce a ringing sound. A thudding sound may indicate a poor seal.
If you feel any of your jars have not sealed properly
the food inside must be eaten immediately, refrigerated, or reprocessed.