How to check your canning jars for a good seal

Posted by Kim Christensen on October 6, 2011 · 1 Comment 

After a long day of canning, you may think that you are off the hook the minute you take those jars out of the water canner. Oh, how wrong you are! One of the most important things about canning won’t happen until those jars are nice and cool. What is it?

You need to check the seal!

If your lids haven’t formed a good seal with the rim of the jar, your food will not be properly preserved. This means that pathogenic bacteria and fungus can form easily and make the food unfit for consumption. While keeping unsafe food in your own cupboard is bad enough, swapping or gifting unsafe food is even worse, as the person receiving the food may not recognize signs of improperly preserved food. While mold will be visible, some bacterial growth in the food may not be, and if someone consumes the food they may become very ill. Plus, opening a jar full of moldy jam is really nasty.

Thankfully, illness, shame, and sadness can be easily avoided with a few simple steps. Rejoice!

Here are a few tips to help ensure that you almost always get a good seal.

• Always use new canning lids. It is unsafe to reuse canning lids for water bath processed foods.
• Do not use really old canning lids, even if they are unused. While the box of canning stuff you found in the cellar of your rental house or the unwanted canning stuff from Grandma may be really exciting, treat yourself to new lids. The adhesive compounds on old lids – even if they are unused – tend to break down over time and may not seal properly. To be safest, use canning lids that are no more than 1-2 years old.
• Check the rim of your jars. If there are chips or cracks, do not use for canning.
• Thoroughly wipe the rims of your jars after filling. Use a damp, clean cloth and wipe up any of the contents that may have spilled on to the rim. I like to use a canning funnel to fill the jars to make it less messy – there’s less to wipe up!
• Process for the designated amount of time in your recipe. Remember to account for changes in elevation if you are canning above 1,000 feet.
• Remove your jars from the water canner gently after processing, keeping them as level as possible. Do not tip to pour off water that may have collected on the lid – it will evaporate. Place the jars on a double thickness of towel on a level surface. Keep away from drafts and let sit undisturbed for 12-24 hours.

Then…

You may hear a “ping!” sound as the jars cool – this sound means that the jar has sealed properly. But listening for this sound alone is not a reliable method for checking the seal. Plus, the “ping!” is an easy sound to miss and some well-sealed jars never “ping!” at all.

Once the jars have cooled…

1. Press down on the center of the lid. Does the lid move up and down or does it feel solid and concave? Solid and concave means a good seal. If the center of the lid moves up and down, your jar has not sealed and the food is not safely preserved.
2. Tap on the lid. If it makes a tinny, ringing sound your jar is sealed. If it sounds like a dull thud, the seal is poor or non existent and the food is not safely preserved.
3. Here’s the big one: unscrew the canning jar ring. Then pick up the jar holding on to nothing but the lid. If you succeed, your seal is awesome. If not, well, you guessed it – bad seal.

If your seal passed the test, you have successfully preserved your foods!

Nice work. Remove the band and wipedown the rims and sides of the jars to remove any residues from canning. Replace the band if you’d like by screwing it on and leaving a bit of give, or leave band-less so you can use the band for other canning projects. Then label the jar with the contents and the date, store in a cool, dark place and consume within one year for best freshness.

If your seal did not pass the test, you have a few options.

1. You can eat the contents immediately
2. You can refrigerate the jar and eat soon. Within 1 – 4 weeks, depending on the food.
3. You can reprocess the jar. Unfortunately, you can’t just screw on a new lid and band, and drop in a pot of boiling water. Rather, you need to start over from the very beginning. Clean the jar(s) and band(s) thoroughly and use a new canning lid(s). Heat the jar (sterilization not needed if processing over 10 minutes). Then heat the contents back to a boil then reduce to a simmer. Then fill the jar as directed in the recipe and process for the designated amount of time.

Easy, right? That said, don’t feel bad about your canning abilities if you have a jar (or two) that doesn’t seal. It happens to the best of us sometimes! Just be thankful that you caught it and didn’t stash it in your pantry unsealed. And besides, it gives you an excuse to dig into some of your tasty foods now rather than later.

In closing, pretty pretty please remember to check your seals thoroughly whenever you can, especially if you will be sharing your canned goods with with friends, family, or at a food swap. Food safety is fun, right? Happy canning!

xo, Kim

Filed under Food Safety, How-To, Tips & Tricks · Tagged with canning, how-to check for a good seal