If screw bands are too tight, air cannot vent during processing, and food will discolor during storage. After Processing After removing hot jars from a canner, do not retighten their lids. Retightening hot lids may cut through the gasket and cause seal failures. Cool the jars at room temperature for 12 to 24 hours on towels or racks. The food level and liquid volume of raw-packed jars will be noticeably lower after cooling.
Air is exhausted during processing, and food shrinks.
If a jar loses excessive liquid during processing, do not open it to add more liquid. After jars have cooled, remove screw bands. Wash and dry bands, then store them in a dry area. If bands are left on stored jars, they become hard to remove and often rust, making them unsuitable for further use. If it springs up when released, the lid is not sealed.