We are often asked how Harvest Guard Reusable Canning Lids differ from single use, metal lids. Since a picture is said to be worth a thousand words, we came up with this simple diagram which shows how our lids and rings are applied to a canning jar.
The key to success is ensuring the metal screw band is not applied too tightly prior to processing, so as not to trap pressure in the jar. It is also necessary to tighten the band, within just a few minutes of removing jars from the canner, while they are still hot, using caution due to the hot contents.
This process will ensure pressure is released properly during the canning process, and allow the vacuum created during cooling to properly seal the jars after removal from the canner.
As always, use extreme caution when handling hot jars of processed food, and if you find a lid that appears “domed up” in the center, allow at least 15 minutes before tightening the metal band as this is indicative of pressure trapped in the jar which can be violently released if handled improperly.