Why do jars break during processing?
A. Jars break during processing for the following reasons: Canner became dry during the processing period. This is caused by either a steam leakage in your canner, which means you need a new part, or by using insufficient water for the processing period. Commercial jars (peanut butter, mayonnaise, etc.) were used instead of the recommended glass home canning jars. Cracked or nicked jars were used. Food was packed too solidly or jars were overfilled. Lids were overtightened (follow manufacturer s directions). Cold jars were immersed in boiling hot water. Food and jars should be hot when placed in the canner. Jars were placed directly on canner bottom. A canning rack should always be placed on the canner bottom. It is not necessary to place a rack between a layer of pint or half-pint jars. Stagger the jars by placing a top jar on two bottom jars (see picture). Pressure was reduced quickly after processing. Always let pressure drop of its own accord. Air was exhausted from canner at too h