How to Ensure a Good Seal
Posted: August 16, 2012
Here are some tips to ensure a good jar seal.
- Use standard mason jars, lids, and screw bands.
- Use new lids.
- Use jars that are free of nicks, cracks or dips on the sealing surface.
- Inspect lids for dents scratches or a narrow or incomplete ring of sealant.
- Use correct headspace—usually ¼ inch for jams and jellies, ½ inch for tomatoes, fruit, pickles, 1 inch for vegetables and meat, and 1 ¼ inch for chicken.
- Use recommended processing methods and times.
- Use a dampened paper towel to remove food particles from the jar sealing surface.
- Turn screw bands firmly tight. This is sometimes described as fingertip tight. If bands are too tight, air cannot vent during processing and lids will buckle; if bands are too loose, vacuum will be low and seals may fail now or later.
- Use a jar lifter to insert and remove jars from the canner. Position the jar lifter on the neck of the jar below the screw band.
- Wait 12 to 24 hours to test if jars are sealed.
- Reprocess jars that did not seal within 24 hours. Use new lids and reprocess for the original processing time. (Or freeze product or refrigerate and use within 3 days.)
- Remove screw bands when jars are cool. Wash jars, rinse and dry before storing. Store jars without replacing screw bands.
- Avoid extreme changes in storage temperatures. Store between 50°F and 70°F.
Testing the Seal
- Press the center of the lid. If it is down and will not move, it is sealed.
- If the lid looks concave (curved down), it is sealed.
- Pick the jar up by the lid and the lid does not come off.
- Tap the lid with a spoon. A clear ringing sound indicates the jar is sealed. However, if food has expanded in the jar and is touching the lid, the lid may still be sealed even with a dull sound.