Frequently Asked Preservation Question

What causes lids to buckle, warp or bulge upward?
Frequently Asked Preservation Question - Articles
Frequently Asked Preservation Question 163207097

When buckling occurs immediately after heat processing, the band may have been applied too tightly. During processing air inside the jar expands and venting must take place to allow air to escape and create a vacuum seal when the jar cools. If the ring band was applied too tightly on the lid, a buckle forms as the air forces a path to escape. Adjust the band using only your fingertips. When buckling occurs during storage, the cause is food spoilage. Heat processing has been inadequate to destroy all spoilage microorganisms which then produce gasses inside the jar. The lid may bulge or it may actually break the seal.