Pop! Pop! Pop! Those are the sounds anxiously awaited by home cooks making homemade jams, jellies, chutneys or any other food that moves from fresh to canning jars for long-term preservation. Sealing the Mason jars is the most important step in the process – that's when the goodness is contained in a bacteria-free environment. It's how the commercial producers preserve those jams and jellies that you see on grocery store shelves that stay fresh for ages. Mason jars, Ball jars and Kerr jars are brand names that describe the same product – glass jars used for canning since the mid-1800s.
Tools of the Trade
Canning and preserving don't require special tools, yet the market is flooded with specially designed water-bath canners, jar lifters, canning funnels, bubble freers and headspace tools. Do you need all these for preserving success? No. A deep pot, cake rack, rubber spatula and a spoon work as well. The two items you must have, however, are the lids and bands that fit on top of the glass jars. Without them, you risk your food getting contaminated.
Preparing the Jars
If the dishwasher is safe for sterilizing baby bottles, it's safe for sterilizing Mason jars. Run the jars you are using through a regular wash cycle and take them out right before they are used. This maintains their heat and keeps them consistent with the hot food you're pouring into them.
It's not necessary to sterilize the lids and bands. Just make sure they're clean and dry. Bands can be reused; lids cannot. Don't economize and reuse the lids – the rubber sealant is violated when it's used the first time, leaving it open for incomplete sealing when used a second time.
Creating the Magic
Once your delicious food is cooked and ready to be jarred, use a canning funnel or a large spoon to ladle the mixture into a Mason jar. Don't fill it up to the top; instead, keep room between the top of your food and the lid. You need this headspace for the vacuum to occur. Most jars have an indicator on the rim for guidance.
Use a spatula to press down the contents all around the jar, packing as tightly as you can. Wipe the jar; then place the lid over the top. Screw down the lid with the band. Your Mason jar is sealed.
Cooking Out the Bad Stuff
A pot of hot water with a cake rack on the bottom should be ready for the jars. For insurance, keep a kettle of water ready on the side if your pot isn't full enough to cover the jars, plus 1–2 additional inches of water. Don't let the jars sit on the bottom of the pot.
Cover the pot and let it boil for the time recommended in your recipe, making sure it's at least 10 minutes. When done, remove the pot lid and let the jars sit for at least 5 minutes. Remove them carefully – they're hot! Place them on a kitchen towel and DON'T TOUCH! Let them rest for 12–24 hours.
Testing the Seals
After 24 hours, remove the bands and try to lift the lid off a jar. If it comes off easily, it didn't seal. Refrigerate and use the contents as soon as possible. If the lid is secure, store the jars in a cool, dark place and use within 18 months.
Sounds of a Good Seal
Look at the lids. They should be concave, effecting a vacuum seal. If you're in doubt, use a teaspoon to rap on top of the lid. You'll hear a high-pitched sound if the seal is good. A dull sound spells trouble. And those popping sounds you heard as the jars rested on the towel when removed from the boiling water? That's the sound of success!