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Canning -- Miscellaneous

What causes lids to come unsealed or not seal at all?

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Using current home canning jars, lids, bands, processing methods and times all help assure there is no seal failure or that unsealing does not occur. It is important to follow the manufacturer?s instructions when preparing jars, lids and bands for use. It is also important to examine the canner to be certain it is in good working condition. When home canning, always use an up-to-date, tested recipe from a reliable source. If seal failure or unsealing does happen, check the following points to determine if one of them is the cause: insufficent or incorrect processing; over-tightening the band before processing or re-adjustment of the band after processing; incorrect headspace; reusing lids; using commercial jars; not preparing lids for use according to manufacturer?s instructions; not removing air bubbles from the jar or cleaning the rim of the jar before applying the lid. For more detailed information about the proper use of home canning jars, lids, bands and canners, see Step-by-Step. If a lid does not seal within 24 hours after processing, the product must be reprocessed immediately, stored in the refrigerator and used within a few days, or placed in a proper freezer container and frozen. To safely reprocess a product, remove the food from the jar. If it was hot-packed, reheat the food. Pack it into a clean, hot jar. Allow the correct headspace for the type of food being canned. Place a new, pre-heated lid on the jar. Reprocess the product using the correct canning method and follow the entire processing time as recommended by an up-to-date, reliable source. Source: Original FAQ posted at

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