In addition to quality food, successful canning starts with the use of jars in good condition and new lids with new or used ring bands in good condition. Regular and wide-mouth Mason-type, threaded, home-canning jars with self-sealing lids are the best choice. They come in ½ pint, pint, 1 ½ pin, quart and ½ gallon sizes. Half-gallon jars should only be used for canning very acid juices. Some jelly jars do come in smaller sizes and are processed according to the recommendations in the recipe.
Canning jars in good condition are reusable for years. Check them for nicks, cracks, and hairline factures before they are used. Small nicks on the rims of the jars can cause the jar not to seal properly. Bail-wire jars with rubber gaskets are not recommended for canning. Bail wire jars have not been made in the United States since the early 1960’s. Jars are subject to more seal failures and breakage. They do make great storage jars for dried foods. Older jars, including those that once used zinc-based lids, may also have lead issues.
After checking your jars for imperfections, it is time to get them ready for use. Wash empty jars in hot, soapy water and rinse well by hand, or wash in the dishwater. Keep jars warm until they are filled with food. You want to avoid filling cold jars with hot food. The jar could crack. Jars that have scale or hard-water films can be soaked for several hours in a vinegar solution of 1 cup of vinegar (5% acidity) to one gallon of water.
All jars with jams, jellies and pickled products processed for less than 10 minutes need to be sterilized. To sterilize, place the jars in the canner and fill jars and the pot with hot water to 1 inch above the jars. Boil the jars for 10 minutes. Increase boiling time by an additional 1 minute for every 1,000 feet above sea level.
Next, prepare lids according to the manufacturer’s instructions. This is important because several years ago, manufacturers such as Ball® changed the design of lids to increase rust resistance and seal-ability and most lids NO longer need to be preheated. Boiling or heating of lids can contribute to seal failure.
Flat metal lids are meant to be used once than tossed after the jar of food has been used. Ring bands in good condition can be reused year after year if they are not misshaped or rusty. Wash both lids and bands prior to canning. Tighten bands on the jars until finger tight. Don’t over tighten because air won’t be able to escape jars causing contents to darken and lids to buckle and jars to break. Too little tightening can lead to liquid loss in jars and seal failure.
Once the jars of food are processed, do not retighten the bands. Leave them alone while the jars cool for 12 -24 hours. The seal will form and strengthen as the jar cools. Once the jars have cooled, remove the ring bands, wash, dry and store for the next time you can. You do not need to store jars of food with the band on since the seal on the jars will be enough to keep the food inside the jars safe. Gently wash the jars with hot, soapy water, rinse and dry before storage. Everything is sealed so soap will not penetrate the seal.
Unsealed jars of food may be reprocessed within 24 hours using a new lid. You can also store them in the refrigerator and use within a few days or freeze the contents in freezer safe packaging.
The last thing is marking the lids with contents, date, and batch number, if canning more than one batch per day. If something were to go wrong with the seals, you would know which other products were canned at the same time.
National Center for Home Food Preservation (2023). General Canning Information: Recommended Jars and Lids. University of Georgia.
Barbara H. Ingham (27 July 2020). Canning Update: successful jar sealing. University of Wisconsin Extension.