A. It is important to remove jars from the boiling-water bath pot immediately when the processing time is up. The spores of certain thermophilic, or heat-loving bacteria, can survive boiling-water processing. Because these bacteria thrive at high temperatures, they can multiply and cause spoilage if preserving jars are left in the hot water to cool slowly.
When processing foods in a pressure canner, the canner is removed from the heat source when the processing time is up. Jars are left in the pressure canner until the pressure returns to zero naturally. This period of time and after removal from heat until the pressure reaches zero, is considered part of the processing time and is necessary for destruction of micro-organisms. Do not rush this cooling by placing the canner under water, or by using a fan. Remove the jars immediately when the pressure returns to zero, and cool at room temperature away from drafts. Do not touch or move the jars until completely cool so position them where they are not going to be in your way.