How Long Should It Take Jars to Seal After Canning?
Quick Answer
Canning jars seal as they cool, but wait 12 to 24 hours before checking them. Leave jars upright and undisturbed during that time. Do not press the lids or tighten the bands while jars cool. After cooling, check every seal before storing the food.
What Are the Common Mistakes When Canning?
Use undamaged Mason-style canning jars and new lids. Wipe each rim and tighten the band as directed by the lid maker. Some mistakes can affect a lid's ability to seal to the jars. These are common mistakes to avoid:
- Leaving too much or too little headspace (the gap between the food and the jar rim)
- Not wiping off food on the jar rim before putting on the lid
- Using a damaged jar or lid, including reusing a lid
- Tilting jars when removing them from the canner
- Tightening bands while jars are cooling
- Pressing on the lids before they have cooled
- Cooling a pressure canner too quickly
- Skipping the required processing time or altitude adjustment
A failed seal does not always mean the food was canned incorrectly. You cannot store a jar that did not seal in the pantry. Store it in the fridge and use it within a week, or freeze it and use it within a year, only if the food was processed correctly and you discovered the failed seal within 24 hours.
How Can I Tell Whether a Canning Jar Is Sealed?
After jars cool for 12 to 24 hours, remove the bands and check the lids. The center should curve down and should not spring up when pressed. A lid that clicks or moves up and down is not sealed. A ping during cooling alone does not prove a good seal.
What Should I Do if a Jar Does Not Seal?
If you followed a tested recipe correctly and find an unsealed jar within 12-24 hours, you have a few options. The easiest option is to either refrigerate the jar and use it within a week, or freeze it in a freezer-safe container, leaving about one inch of headspace to allow for expansion. Another option is to reprocess the jars. This is great if many of your canning jars didn’t seal. However, reprocessing jars takes time and can reduce food quality. If you choose to reprocess, do all of the following within 24 hours:
- Confirm that a tested hot-pack process exists for this food. Hot pack means heating food before filling jars.
- Remove the lid, transfer the food to a pot, and bring it to a boil.
- Fill a clean, undamaged jar with the hot food. Leave the required headspace and remove air bubbles.
- Wipe the rim and fit a new lid as directed.
- Use the full tested hot-pack processing time for your jar size and elevation.
Do not reprocess food without a tested hot-pack process. If you did not follow a tested recipe correctly the first time, do not taste or eat the food. A jar that comes unsealed during storage is a different problem: discard it safely. Do not treat it as a fresh seal failure.
References
- USU Extension — Avoiding Common Canning Mistakes
- USU Extension — Principles of Pressure Canning
- USU Extension — Principles of Boiling Water Canning
- USU Extension — Ask an Expert: What Should I Do If I Can't Find Canning Lids?
- USU Extension — Storing Canned Goods
- USU Extension — Preserve the Harvest
- NCHFP — Reprocessing When a Lid Does Not Seal
Adapted from USU Extension food preservation resources.
Contact
Jenna Dyckman, USU Extension Associate Professor
Jenna Dyckman
Extension Associate Professor | Cache County Director
Home and Community Department