Distinguish between bubble types to determine safety.

It’s not uncommon to see tiny bubbles in glass canning jars; these are generally not a concern. But large bubbles in the glass are manufacturing defects. They indicate weak points in the walls of the jars which could spell trouble during the canning process – there is a good chance of the jar breaking. This is one of the reasons that all new canning jars should be carefully inspected before being used. Check for bubbles, chips, cracks, and manufacturing debris, and then wash the jars.

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Last updated July 2025