A note from the goats: This blog used to have a weekly feature called “Ask the Goats.” At the time, most of our readers were people we knew in real life, and we quickly ran out of questions. Since then, our audience has grown, and we’re now getting a steady stream of questions on Twitter, in the comments, and via e-mail. We’d like to use this forum to share our answers with the rest of you, who are quite likely wondering about the same things. Keep the questions coming, and we’ll try to answer them on Mondays!
Q: I’ve just read your instructions [for canning chicken stock]. I’ve tried twice now to can a batch of stock in my pressure canner and most of the jars won’t seal. I removed air bubbles, left 1″ in the jar, and followed the other instructions. Any ideas why these jars won’t seal?—Jen
A: After Jen asked me this, we had a long e-mail discussion about the various options. She was indeed doing everything right, but we eventually settled on two things. First, her stock was fairly fatty. While this makes for delicious stock, it can make getting a good seal more difficult if fat gets trapped between the lids and the jar. But secondly, and more importantly, this was a case of opening the pressure cooker lid too soon.
But what, exactly, constitutes “too soon”? Most pressure canning instructions, including mine, tell you to wait about 10 minutes after letting the pressure drop of its own accord before opening the lid. Over time, though, I’ve found that this is too soon. A pressure canner full of chicken stock is very, very hot. Even when the pressure drops inside the canner, the temperature and pressure inside the jars is still quite high. The dramatic change in pressure from removing the lid (even after the indicator has fallen) can be enough to cause liquid to spurt or seep out of the jars. This not only causes you to lose some of your precious chicken stock, but it also interferes with the seal. So now, whenever I pressure can anything with a significant amount of clear liquid (beets, tomatoes, stock, etc.), I always wait at least an hour after the pressure drops before opening the lid. Ideally, I do this at night and just turn off the heat and go to bed. The next morning, I take off the lid, and viola! Everything seals.
Jen e-mailed me about a week later with an update. Success!