Put a Lid On It! Best Practices for Using Closures for Home-based Canning(FN2028, Revised May 2022)
Research-tested canning recipes recommend metal two-piece closures for home-based canning. Two-piece lids are sold to fit regular and wide-mouth glass canning jars and are made up of a flat metal lid and a metal screw band. The lid contains a sealing compound that, when properly used, softens during the canning process and forms an airtight seal as the container cools.
Traditional metal lids are designed to be used only once. When opening the jar, the lid becomes warped. Also, the sealing compound is compromised by use. Unused lids should be stored in a cool, dry location and may be good for up to five years from the date of manufacture. Through time, the sealing compound will degrade and the lid may fail to seal.
CAUTION: Many consumers noticed canning supplies were of inferior quality in 2021. To ensure quality, consider ordering directly from the manufacturer or its representative and not from a third-party vendor.