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What causes lids not to seal?

Failure of lids to seal may be caused by:

- A chip on the rim of the jar. 

- Failure to follow manufacturer's directions for using lids. 

- Presence of food particles on jar rim. Always wipe rim clean before putting on lid. 

- Leaving too little headspace, letting pressure in pressure canner fluctuate, or lowering the pressure too suddenly. In all of these cases, food particles may be forced between the jar and lid, causing sealing failure.  

- Leaving too much head space may prevent sealing because the processing time was not long enough to exhaust all the air from the inside of the jar.

- Not removing air bubbles has the same effect as leaving too much headspace. 

- Putting screw bands on too loosely. 

- Tightening screw bands after removing jars from canner. 

- Reusing lids. Lids should be used only once. 

- Defective lids. Contact the manufacturer to recover costs when procedures have been followed and lids are defective.  

- Using commercial or one-trip jars, such as mayonnaise, peanut butter, or baby food. These jars have slightly different sizes of sealing edges.      




Barbara Willenberg, Nutritional Sciences, University of Missouri-Columbia







Last update: Tuesday, May 05, 2009



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