Canning mishaps happen to the best of us. One day I'm confidently demonstrating on video how to pickle asparagus. The jar is still hot, and while most canning pros tell you to let the jar cool completely before testing the seal, I'm feeling bold. I pick up the jar and turn it upside down. The lid stays put. Magic.
It's a neat trick and it usually works, but not always. Fast-forward a few months later and I'm doing another canning demo. This time it's live, and I'm feeling the crowd and having fun. So I take the jar of carrots, turn it upside down... and you can probably guess what happens next. Pickling brine and carrots spill out everywhere. I just provided a solid example of what not to do.
Sometimes learning what not to do is a whole lot more important than learning what to do. We always remember mistakes longer than flawless performances. With canning, most of the time there is a simple explanation when things go wrong. So assuming you're not playing fast and loose with methods or ingredients (canning recipes should be followed faithfully for safety reasons) here are a few technical mistakes to avoid.
- Overfilling jars. Too full and the contents of the jar can bubble out while the jars boil away. When bits of food adhere to the rim, the lid won't seal to the jar. Recipes generally say how much room to leave, since it changes depending on the size of the jar (small jam jars need less space than large jars, but leaving 1/2 inch of space between the food and rim is a good rule of thumb).
- Under-filling jars. When there's too much room in a jar, the jar might not seal. Even if it does, the contents of the jar tend to oxidize.
- Forgetting to soften the rubber compound on the lid before putting it on the jar. You want to make sure the rubber is soft enough to adhere to the rim of the jar while it processes. When you take jars out of the water bath to cool, the inside of the jar has this sort of vacuum effect and the lid sticks to the jar firmly.
- Putting cold jars into the hot water bath. When cold jars are put into hot water, they can crack. So when you scald jars in hot water before filling them with vegetables or fruit, you aren't sterilizing them (that happens while the filled jars boil away). You're tempering the glass.
- Not having enough water in the pot you're using to process the jars. It should cover the jars by at least an inch. If the top of the jars aren't submerged, the jars won't seal correctly.
- Finding yourself with mystery jars. This sounds basic, but it's so easy to put jars away thinking you'll label them later — and then a few months go by and you have no idea if the jar in your hand comes from the batch of hot sauce you made...or from the batch of jam.
There are others pitfalls to avoid, but I don't want it to sound like canning is this scary process. It's pretty simple. Fun, actually. But it's always more fun when things come out successfully. It also helps when there are some good tunes to listen to. My blog post tomorrow tackles that subject — I'll be sharing my ideal cooking playlist.