Canning - Why Lids Don't Seal

There are various reasons why a lid doesn't seal on a canned product. Review this list of possible reasons:

1. Failure to read and follow instructions on package for using bands and lids.
2. Leaving wrong amount of head space when filling jars.
3. Not removing particles of food, seeds, seasonings, or pulp of fruit from the top of jar before putting the lid on. Also, watch for threads from the cloth that is used to clean the rim of the jar.
4. Screwing band too tight can cause lid to buckle.
5. Not screwing band tight enough.
6. Insufficient heat to seal the lid.
7. Failure to exhaust (vent) steam - pressure canner for a full 10 minutes.
8. Letting pressure in canner fluctuate.
9. Reusing jars in which commercial food is sold.
10. Using warped, rusty, worn bands, or old commercial caps instead of home canning brands that are in good condition.
11. Reusing lids. The lid of a two - piece metal cap should not be used more than once.

Source: USDA Complete Guide To Home Canning

Also see:

• University of Missouri Extension guide Quality for Keeps — Before You Start to Can, Learn the Basics
• University of Missouri Extension guide Quality for Keeps: Food Preservation — Steps to Success in Home Canning

Susan Mills-Gray, Mills-GrayS@missouri.edu
Regional Specialist, Nutrition and Health Education
Cass County, Missouri
University of Missouri Extension