What causes buckled or bulging lids?
Buckled lids appear to warp or bulge upward under the screw bands. There are two causes: • Buckling that is apparent immediately after heat processing is caused by application of the screw bands too tightly. Bernardin two-piece home canning lids are made in two pieces for a very important reason: to release pressure and vent air from the jar during heat processing. As the filled jar is heated, headspace pressure increases until excess air is vented from the jar. When the band is applied too tightly, there is no way for air to be exhausted from the jar. Consequently, the pressure build-up warps the lids and disrupts the seal formation. • Buckling that occurs during storage is caused by food spoilage. When heat processing is insufficient and does not destroy all spoilage microorganisms, food may spoil during storage. This spoilage produces gases inside the jar that forces the lid to bulge upward. This food should be discarded in a manner that neither humans nor animals will consume it.
