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Sep 7, 2010 08:13 PM

Canning tomato sauce, what am I doing wrong?


I am in the middle of canning fresh San Marzano tomato sauce for the first time. The instructions from the Bernardin website say to leave 1/2" of headspace, simmer 1 Litre jars for 40 minutes covered with 1" of water. I have done this and the lids are buckling. Has anybody else experienced this? What, if anything, have I done wrong? The only thing I can think of is that maybe I have tightened the jars too tight...

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  1. The lids are supposed to pop and become a little concave. If thats what's happening then you did everything okay. If they are actually buckling - like making a crease I'm at a loss. You should tighten the lids, but you don't need to really crank them closed, the change in pressure inside the jars as they heat creates a vacuum seal. Hope this helps - Good Luck!

    7 Replies
    1. re: corneygirl

      Yes, the lids are not just concaving, they are actually buckling and bending in the water bath.

      I've done loads of canning the past few years, but this is the first time I've done tomatoes and used 1 Litre jars. I've never experienced this before.

      1. re: bogie

        Can you post a pic of the lids? I just can't picture how the lids could "buckle" or "bend". Is there a seal, or did the sauce leak out into the water?

        You're correct that you shouldn't tighten the lids too tight, air has to be able to escape during the canning process, but that doesn't need very much slack. (The usual advice is to fully tighten then loosen the ring about a quarter of a turn.) But if they're too tight, I'd expect the lids to bulge, and then go back to being fairly flat instead of slightly concave. If you're lucky and the jars don't crack, anyway.

        1. re: MikeG

          The lids did buckle and bend, however the seal must hav remained intact as no sauce leaked into the water bath. I will take pictures for you when I get home this afternoon.

          I think that maybe I shouldn't have tightened the jars so much. I could see that it might not be a problem for a 250ml jar in a 10 minute water bath. But with the added volume of a 1 Litre jar as well as an increase in pressure and 40 minute bath time, the effect of too tight jars could be amplified.

          1. re: bogie

            If nothing leaked and the lids stayed convex after processing then yeah, I agree the only answer seems to be overtightening the lids. You'll need to re-process (or freeze, or use now) the jars that happened to, but at least the jars didn't crack.

        2. re: bogie

          Are they buckling inward? If so, I suspect that you are leaving too much airspace in the larger jar and creating a very strong vacuum that buckles the lid.

          That's a shot in the dark though, because I've never seen this problem while canning.

          1. re: cowboyardee

            No, they are buckling outward. I am leaving exactly 1/2" of headspace as specified on the Bernardin website. Is that too much?

            1. re: bogie

              Sounds like over-tightening then. But still, just a guess.

      2. as others have said, picture would be helpful but it does sound like too much head space.

        1. I will buy more lids and reprocess this evening, I will let you all know what happens when I don't tighten the lids as much. Thanks for your help!