Michigan
State University Extension
Preserving
Food Safely - 01600949
10/13/97
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.