How to Test the Lids on Home Canned Jars of Food to Make Sure They Sealed Properly

With spring here, and the planting season starting up, it won't be too long before gardeners like myself will be preserving fresh produce. I use metal canning jar lids with rubber seals, and metal, threaded bands to hold the lids in place. Hearing a "ping" as the jars cool down is a good indication the lid has sealed. As each jar cools down, a vacuum forms inside. It pulls the lid down tight against the glass and seals it in place. When that happens, the "ping" sound is made. The jars will have completely cooled down in 12 to 24 hours. Unscrew the rings and remove them. Then, it's a good idea to test the lids on home canned jars of food to make sure they sealed properly. Using one of these tests should be adequate, unless you're not sure.

1. The Finger Test
Place your fingertip on the center of a canned jar lid. Press down and then release. If you can't make an indent in the metal lid, the jar is properly sealed. If the lid pops back up when you release your finger, that means the lid isn't sealed.

2. The Sight Test
Another easy way to test the lids on home canned jars of food to make sure they sealed properly is by looking at them. Hold the jar up so you can see straight across the lid. The lid should be curved slightly in its middle, according to pickyourown.org. A metal lid that's either flat, or is protruding, isn't sealed.

3. The Ringing Test
Tap the center of a metal lid on a jar of home canned food with a teaspoon. If it makes a high-pitched ringing sound, according to the New Mexico State University, the lid is sealed. If not, then the lid has failed.

What To Do With Home Canned Jars of Food That Failed to Seal

Within 24 hours of processing the jar the first time, you must do one of these things in order to save the contents:

1. Process the jar again immediately. Check the jar for cracks or nicks, especially in the glass rim. If you find damage, replace the jar.

2. Place the jar with the lid on it in the refrigerator. Use the contents up within a few days.

3. Place the contents of the canning jar in a freezer container, according to freshpreserving.com. Freeze it until you're ready to use the food.

Resources
http://www.pickyourown.org/spoilage_testing.htm
http://aces.nmsu.edu/pubs/_e/e-316.html
http://www.freshpreserving.com/pages/faq/42.php