Why are My Canning Jars Not Sealing? Canning Jar Issues

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This is the second in a series of videos explaining possible reasons why your jars are not sealing.  What is going on? How can you fix this? Why are my canning jars not sealing? One possibility is you have issues with your canning jars.

Residue on the Rim of the Canning Jar

A canning lid has a rubber coating that runs around the inside edge of the lid. This rubber seal must have direct contact with the jar. When a hot jar starts cooling, the contents start shrinking, and if there is good contact with that lid and jar…it will suck down and there will be enough vacuum to create a seal.  

One of the most likely reasons for jars not sealing is food or residue on the rim of your jar.  Always be sure and clean off the rim of the jar just before you put the lid on it. If there is anything on that rim, if it is sticky or greasy, or if there are food particles, it might interfere with the seal.  

Wiping the rim of a jar of carrots.

Crack in Rim of the Jar

If there is a crack in the rim of the jar, it will not allow the seal to happen. Run your finger around the rim of the jar to check by feeling. You can feel small nicks that you might miss by just looking.  

Boiling the Canning Lids Before Placing Them on the Jars

It used to be standard practice to boil canning jar lids before putting them on the jars. It softened the rubber coating and made for better seals. However…the coating that is used on jars nowadays is different. It is thinner, and it does not require boiling.  

In fact, boiling can actually cause the lids to not seal!

Rings and flat lids spread out on the countertop.

Some people really don’t like the new way, but the fact remains; this is the way lids are now made. If you are using old practices, you need to update to use the new lids properly. 

It took me a while to get used to the idea of not boiling. I’d still put the lids in a pan and heat them up. I’d get pretty close to boiling but not quite. So they still got very hot. Now I simply put them in a pan or bowl and pour hot water out of the tap over them.  

I don’t recommend just taking them out of the box directly to the jars. They do need to be cleaned off by some hot water. But no boiling is needed. Everything gets fully sterilized in the canner when you are processing.  

I love it! So much easier. It doesn’t take a burner on your stove, and it is still a safe, recommended method.  

Using Non-Standard Canning Jars

There are times when you might want to use recycled mayonnaise or pickle jars.  Using recycled jars is okay…but use them with caution. Standard is better. 

Learn more about using recycled canning jars here.

  • Sometimes the lids don’t fit. It seems like the lids fit, however, they are just slightly off. If the rim of the jar is not on the rubber coating, it won’t seal. Standard canning jars will fit standard canning jar lids.  
  • Another issue is that sometimes non-standard canning jars will have a thinner rim that won’t seal well. Again, if it doesn’t have enough contact surface, the seal can’t happen. 

Links to the rest of the series.

  1. What Causes Jars to Not Seal: 10 Common Reasons
  2. Why are My Canning Jars Not Sealing? Canning Jar Issues <— you are here
  3. Are Canning Lids Supposed to Pop? Why are My Canning Lids Not Sealing?
  4. Why are My Canning Lids Not Sealing? Issues with your canning methods.

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Why are My Canning Jars Not Sealing

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