My Jars Didn’t Seal! What Happened?

We’ve all been there. You’re at the end of a canning project, the jars out of the canning pot and are cooling on the counter. As you clean up, you notice that there’s one jar that didn’t seal. Or worse yet, none of the jars have sealed. If this has happened to you, two questions probably popped to mind. Why did this happen and what can I do to fix it. Let’s tackle these one at a time.

Why did this happen?

  • It could be that your canning pot wasn’t at a full, rolling boil for the entire canning process. Without that full boil, it could be that the jars didn’t fully vent the oxygen in the headspace. Without a thorough venting, there won’t be enough of a pressure differential to cause the vacuum seal to form when the jars come out of the canner.
  • Another possibility is that there was a physical barrier to the seal forming. In most cases, this happens when you don’t wipe your rims completely, or some food particle gets pushed out of the jar during processing.
  • Sometimes the lids are to blame. Really old lids sometimes lose the ability to create a full seal. And of course, if you’re reusing lids, the chances that they will provide a high quality seal are very low.
  •  There was a chip or crack in the rim of your jar. This will prevent a seal every time. You can prevent this simply by carefully looking over your jars before filling and canning.
  • Improper headspace. Under or over filling your jars can sometimes cause the seal to fail.
  • Occasionally, the rings are the culprit. While it is important to only tighten to fingertip tight to allow the oxygen to vent, if you leave them too lose, that can cause a seal failure.

How to fix it?

The best way to handle jars that failed to seal depends on the product you’re dealing with and how many jars have failed. If you have just one or two jars that failed, the easiest thing to do is to put them in the fridge and eat or share them promptly. The reason for this is that to reprocess jars always results in some loss of product and quality.

When it comes to pickles, trying to reprocess them isn’t ideal, because any additional heat exposure will soften their texture. This is particularly true for cucumber pickles.

When it comes to jams and other sweet preserves, there are more options. If the entire batch has failed to seal, the best method is to open the jars, reheat the jam, prep the jars, use new lids, and reprocess.

If you have just one or two jars that didn’t seal and you don’t want to go with the refrigeration plan, there’s another way. Once the jars have cooled completely, put new lids on the jars (taking care to wipe the rims and make sure that you’re getting the rings tightened properly). Place those room temperature jars in a canning pot of cold water. Bring that pot of water to a boil slowly, so that the contents of the jars heat along with the water. Once it reaches a rolling boil, process as you always do. The jars should seal properly this time around.


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19 responses to “My Jars Didn’t Seal! What Happened?”

  1. This just happened to me last week. I had two whole batches of raspberry jelly that didn’t seal! I had used lids that came with a new pack of jelly jars, so I would have expected them to be ok, but I think they were defective. I was so upset…as you know, raspberry jelly can be time consuming…I had hand picked berries over the course of a week in order to get enough for my jelly. I used new lids and reprocessed the jars, and I heard that wonderful “pop” as I took them out of the canner!

  2. Unsealed jars is something I’ve been wondering about. I’ve read to not check the seals for 12 hours, then to refrigerate anything that didn’t seal. But that means the food sat there unsealed for 12 hours. So I end up visually checking the seal in the first hour or so, then refrigerating anything that hasn’t sealed by then. Is there a particular reason to wait so long to check seals? Thanks!

    • My jars usually seal right away and you can hear them pop into place. Last night I was making yellow plum preserves and one of the jars did not seal. The preserves were still warm and I popped it into the microwave until the top bubbled and I resealed it. Worked like a charm!

  3. Could you address jar breakage? Is there anything to look for when preparing the jars? I have the problem mostly with quart jars that I’m reusing (water bath not pressure). Hate to lose even one jar of peaches or pickles. Thanks

  4. Best post ever! It never occurred to me that I possibly wasn’t tightening the rings enough. I have very little failure but I also am wary of tightening my rings too much so this suggestion sounds likely to me.

  5. I occasionally have a jar that doesn’t seal (have been canning for many, many years) and always carefully check my jars before storing. Every now and then, many months later, I go to use a jar out of the pantry and find the seal has popped. Even though there is usually no mold (so I assume the seal failed recently) I always discard the contents. Would you know why this happens?

    • If a seal fails while on the shelf, it’s typically the result of spoilage or there was a bit of food on the rim of the jar.

  6. Unsealed jars are frustrating, but can be a blessing in disguise. Especially if you want to get your hands on the yummies that are inside said jars. Your refrigeration plan is my goto!

  7. How are you preparing your new lids? The “old” boil to sanitize is OUT!! The new lids have a different product on the rims that does not do well in boiling water. Use the NEW directions on the lid box – wash in sudsy warm water, rinse and set aside – can set aside in warm water if you wish, but not in boiling water. We found this out in 2018 after 40 years of canning, We had some lids stock- piled (purchased when on sale) and went happily on without reading the lid box directions – who reads that every year? We lost 15 quarts of canned peaches which had successfully sealed and were placed on the canning shelves. They slowly lost their seal – one at a time and not all from the same batch. To preserve the last 65 quarts of peaches, we reprocessed them using the NEW directions for lids – all is still great on the canning shelves now.

  8. I’m discouraged. Really not sure if this canning is worth the effort, between inconsistent information on jar lids, rim tightness, jar breakage, and always wondering if I’m going to poison myself or someone else. This is a good site though, I just might decide to quit trying to can things at home. Too much work. 🙂

  9. What if an unsealed jar of otherwise perfectly made jam with a ph of 3.50 sat at room temp for 24 hours undisturbed after being hot water processed? Would it be safe to consume?

  10. Okay, I had something weird happen. I was canning jars of brunswich stew but two of the jars apparently took on liquid from my pressure canner, HOWEVER the jars sealed. Should these be frozen/refrigerated or tossed out?

    • That’s really weird. There’s not enough water in a pressure canner to really leak into the jars. Are you sure it’s not just separation. Still, it’s probably safe, though the stew might be unpleasantly dilute.

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