A wash kettle that fits over two burners should not be used on either a gas or electric range because jars in the middle of the kettle will not get enough heat. Return to Table of Contents Processing in a Pressure Canner Low-acid foods must be processed in a pressure canner for the correct time and temperature to avoid the risk of botulism. Foods can spoil if processed at a lower pressure than specified or processed for a shorter time than specified. All types of pressure canners must be vented 10 minutes before they are pressurized because air trapped in a canner lowers temperature, resulting in underprocessing. Canners must be cooled at room temperature until they are completely depressurized.
Foods can spoil if canners are improperly exhausted or if canners are cooled too quickly with water.
Pressure canners have either a weight or a dial gauge that controls pressure. For weight-gauge models, the sound of the weight rocking or jiggling during processing indicates that the canner is maintaining the recommended pressure. Weight-gauge models, however, cannot correct pressure precisely at altitudes of 1,000 feet above sea level or higher. Dial-gauge models must be checked for accuracy before use each year. Gauges can be checked at county Cooperative Extension offices.