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
- 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
- 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
- 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