Michigan State University Extension
Preserving Food Safely - 01600949
Follow these steps for successful pressure canning:
1. Put 2 to 3 inches of hot water in the canner. Place filled jars on the rack, using a jar lifter. Fasten canner lid securely. 2. Leave weight off vent port or open petcock. Heat at the highest setting until steam flows from the petcock or vent port. 3. Maintain high heat setting, exhaust steam 10 minutes, and then place weight on vent port or close petcock. The canner will pressurize during the next 3 to 5 minutes. 4. Start timing the process when the pressure reading on the dial gauge indicates that the recommended pressure has been reached, or when the weighted gauge begins to jiggle or rock. 5. Regulate heat under the canner to maintain a steady pressure at or slightly above the correct gauge pressure. Quick and large pressure variations during processing may cause unnecessary liquid losses from jars. Weighted gauges on Mirro canners should jiggle about 2 or 3 times per minute. On Presto canners, they should rock slowly throughout the process. 6. When the timed process is completed, turn off the heat, remove the canner from heat if possible, and let the canner depressurize. DO NOT FORCE-COOL THE CANNER. If you cool it with cold running water in a sink, or open the vent port before the canner depressurizes by itself, liquid will spurt from jars, causing low liquid levels and jar seal failures. Force-cooling may also warp the canner lid of older model canners, causing steam leaks. Depressurization of older models should be timed. Standard size heavy-walled canners require about 30 minutes when loaded with pints and 45 minutes with quarts. Newer thin-walled canners cool more rapidly and are equipped with vent locks. These canners are depressurized when their vent lock piston drops to a normal position. 7. After the vent port or petcock has been open for 2 minutes, unfasten the lid and remove it carefully. Lift the lid away from you so that the steam does not burn your face. 8. Remove jars with a lifter, and place on towel or cooling rack, if desired.