What Causes Canning Lids to Buckle?

Buckled lids look warped, bulged, or creased near the outer edge. Two-piece vacuum lids are made to release pressure by venting air from the jar after processing and during cooling. When the lid does not vent, pressure build-up, warps the lids and prevents a good seal.

There are several potential reasons for this to occur:

• Applying the screw bands too tightly. Buckling may become apparent immediately after processing. Screw on bands just until resistance is felt, or fingertip tight.
• Boiling the lids softens the sealing compound too much, resulting in a premature seal. Today’s Ball® and Kerr® lids do not require preheating. Research shows preheating them will cause seal failure. Simply wash in hot soapy water, dry, and use.
• Food spoilage due to incorrect processing produces gases inside the jar that force the lid to buckle or unseal. Use current processing methods and guidelines.

NOTE: Never reuse lids. They will not form a good seal. According to the USDA Complete Guide to Home Canning, the rubber gaskets in unused lids should work well for at least five years from date of manufacture. It is best, however, to only buy the quantity of lids intended to use within a year.

Source: Frequently Asked Preservation Question: Buckling Lids – Penn State Extension