When it comes to pressure canning people often share two related problems:

  1. Jars enter the canner full of liquid and when processing finishes you are surprised to see how much liquid is missing.  The outside of the jars are a little dirty and it appears that liquid has siphoned from inside, out.
  2. Related to question 1; is it ok to still eat preserved (and pressure canned) food that is missing a lot of liquid?

People often ask question 2 without resolving question 1 first.  I say this because I was one of them – I was so focused on what to do with the ‘problem jars’ after processing that I missed getting to the root of the problem and preventing them all together.

And, while I have the occasional jar that siphons, it’s an extreme rarity.  So, let’s start there..


I used to suffer from siphoning on a routine basis.  It happened almost every time I pressure canned and quite often when I made pickles and other water bath preserves. I was getting frustrated with my results when this happened:

  • The timer went off in my kitchen and I turned the heat off.
  • I carefully moved the canner from the electric element (where it sat) and moved it to a cool element to cool it faster.
  • I wasted a few minutes and, being impatient, I put a steam-resistant oven mitt on and, against all warnings (do not do this), I removed the weight on the top of the canner.  This let the pressure out quicker so I could open it sooner.
  • I waited a while until I could open the canner.  I tried a few times to open it so I wouldn’t lose any time (I have no idea why I was in such a rush).
  • I grabbed my tongs, pulled the jars out and sat them on a rack.  I watched the jars closely and was amused to see the liquid still boiling inside.
  • I walked away.  Everything seemed fine.
  • I checked my jars a few hours later.  The counter was wet and the jars had siphoned.

Let’s be clear: don’t do the above.  I messed up for your benefit!

I wasn’t certain but I had my first theory: rapidly cooling the jars forces air lout of the jars at a faster rate than naturally cooling and this increased pressure pulls the liquid out.  I don’t know if my theory is scientifically correct – but letting the jars cool naturally has all but solved my siphoning problems!

When waterbath canning I simply turn the heat off and let the jars remain in the waterbath for a few minutes to slightly lower the temperature.  5 or 10 minutes is generally enough.  Then proceed as you normally would.

When pressure canning, I turn the element off and walk away.  I don’t open the canner until it easily opens on it’s own.


I often worry when answering questions on safety here; and I tend to avoid them like the plague.  I’ve also written on why you probably shouldn’t blindly trust me or other food bloggers without assessing the risk for yourself.

And, the good news here, is that you don’t have to trust me!  Check out these guidelines from the University of Minnesota Extension Office:

Loss of liquid does not mean that the food is unsafe to eat. However, food above the liquid may discolor during storage.  Use those jars first. If the loss of liquid is excessive (i.e. at least half of the liquid is lost), refrigerate the jar(s) and use within 2-3 days.

The extension office publishes a wonderful newsletter (linked above) – it has some amazing information on pressure canning and more information on troubleshooting siphoning!

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