Ask the Goats: Leaking after Processing?

Ask the Goats is a weekly feature in which we attempt to answer your questions about growing, making, preserving, and eating food. Got a question for the goats? Drop us a line at

Q. Last week I canned a few quarts of crushed and whole tomatoes. I thought I had done everything correctly, including allowing proper headspace in my jars. However, after processing some of the jars leaked  some of their juices while cooling.  At first I was concerned, but it seemed that the jars had sealed properly so I cleaned them and put them away.  I checked on the jars yesterday and found that the two quarts of crushed tomatoes had leakage signs.  I tossed them out 🙁

So here’s where the question comes in… yesterday I canned 6 quarts of pickled peppers.  I was especially careful with the headspace this time around. Again several of the jars had leakage while they were cooling (as evidenced by dried briney trickles down the sides of the jar). I know for sure all ended up sealing properly (as I was sitting in the adjoining room while they cooled and heard many plinking sounds!). Anyway… is a small amount of leakage normal after removing your jars from your canner?  Should I be concerned about my peppers?  Am I doing something incorrectly?—Lindsey Nicolescu

A: Ah, siphoning—the canner’s bane. The problem you’ve described is fairly typical, especially in pressure canning (see this earlier Ask the Goats on a related problem). Whether you’re water-bath canning or pressure canning, the cause is the same: a sudden change in temperature or pressure can cause trapped air in the jars to suddenly expand, forcing liquids out. In a pressure canner, you can reduce the chance of the problem by leaving the jars to cool in the canner, but obviously, this strategy won’t work in the water-bath. What you can do is turn off the heat and take off the lid when the processing time is done, then wait five minutes. This cools things down a bit and reduces the chance that you’ll get siphoning without overcooking the product too much. I had never noticed this before your question, but it’s actually the strategy recommended in many canning books, including the Ball Blue Book and Put ‘Em Up.

The main danger from siphoning is that it can interfere with your seal. If this is the case, refrigerate or reprocess them. Depending on their contents, you might even be able to add more liquid before trying again. If you do get a seal, the jars are safe, but you’ll want to eat them first, as they’ll be more prone to oxidation. Again, this isn’t a safety issue, but a quality issue.

As for preventing the problem in the first place: siphoning is much more likely to happen in liquid-y products (peaches in  light syrup, pickled peppers, tomatoes in water, etc.) than in thick, gloppy canned goods (jams, chutneys, relishes). Be sure to remove air bubbles, and watch that headspace. Then cross your fingers, spin three times, and hum.

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6 comments to Ask the Goats: Leaking after Processing?

  • ndrew

    Quick clarification needed: How does leaving jars to cool indide a pressure canner differ from letting them cool in a water bath? Why is the former ok and the latter not? Wouldn’t the food keep cooking a bit in both?

  • ndrew

    Quick clarification needed: How does leaving jars to cool inside a pressure canner differ from letting them cool in a water bath? Why is the former ok and the latter not? Wouldn’t the food keep cooking a bit in both?

  • dorisandjilly

    Honestly, anything that’s already been in a pressure cooker has already gotten so hot that it would be difficult to damage its texture further. I’m thinking here of things like tomato sauce and chicken stock. I suppose with whole tomatoes in juice it might be a good idea to take them out sooner rather than later. With most (but not all) water-bath items, you care about the texture. Think peaches and peppers. But more to the point, siphoning is generally less of a problem with water-bath canning. There’s no point in leaving the jars in there for hours at a time because 5 minutes will take care of the problem.

  • Also don’t forget that you don’t HAVE to throw them out if you’re worried about the seal–just pop those babies in the fridge and use them over the next week or so.

  • Janice Young

    I just canned 25 lbs. of plums, I no longer no which ones were the leakers, but, there were some in each batch, is there any way to tell as all the jars are sticky…I can’t eat 25 lbs. of plums in the next week and I hate to throw them away, especially after all that WORK!!!

  • Kathleen

    i just made some apple butter and took it out of the water bath about 32 hours ago. When I checked the jars at 24 hours last night all the jar lids looked concave (I never heard the pinging sound). this morning I went to wipe down the jars and found that some of the butter had leaked out at some point. I immediately put them in the refrigerator, but since it has been longer than 24 hours is it still safe to eat and should I reprocess?