Canning Vault field guide
Jars, Lids & Reliable Seals
Choose, fill, close, cool, and inspect jars with confidence. Reliable seals begin before the lid touches the jar. Use purpose-made canning jars, protect the sealing surface, leave the specified headspace, and give jars time to cool naturally.
Chapter 01
Choose and inspect the container system
Mason-type home-canning jars with compatible two-piece lids are the standard choice. Sound jars and screw bands may be reused, but use a new flat metal lid for each batch and follow the lid manufacturer's current preparation directions.
Wash jars before every use and keep them at the temperature required by the recipe. Sudden temperature differences can contribute to breakage.
Presterilize empty jars when a jam, jelly, or pickled product will be processed for less than 10 minutes. Presterilizing is unnecessary when filled jars will receive at least 10 minutes in a boiling-water canner, or when they will be pressure canned.
Chapter 02
Headspace gives food and air room to move
Headspace is the measured distance between the food or liquid and the top of the jar. Too little can allow food to bubble onto the sealing surface. Too much can leave excess air and interfere with the formation of a strong vacuum.
After removing bubbles and rechecking headspace, clean the rim as directed. Even a small seed, fiber, or film of syrup can interrupt contact between the lid compound and glass.
Chapter 03
Apply lids without trapping the air
Center the prepared flat lid and apply the screw band according to the lid manufacturer's directions. Excessive tightening can prevent air from venting during processing and may contribute to buckled lids or breakage.
Do not retighten bands after processing. The seal develops as the jar cools and the contents contract.
Chapter 04
Cool, test, clean, and label
Let jars cool undisturbed for 12 to 24 hours. Then remove screw bands, test each seal, and wash away residue without disturbing the lid.
A properly sealed lid is concave and does not spring upward when pressed. Label the jar with its contents and date, then store it without the band in a clean, cool, dark, dry place.