Pacific Northwest PNW 421 Using Manual - Safety Features
jiggles during processing. They control pressure pre-
cisely and need neither constant watching nor checking
for accuracy during processing. The sound of the weight
rocking or jiggling indicates that the canner is maintain-
ing the recommended pressure.
The single disadvantage of weighted-gauge canners is
that they cannot correct precisely for higher altitudes. At
altitudes above 1,000 feet, they must be operated at
canner pressures of 10 pounds per square inch instead
of 5, or 15 pounds per square inch instead of 10.
The dial gauge is attached to the cover and has a nee-
dle to point to the amount of pressure inside the canner.
Dial gauges should be checked for accuracy before use
each year. If your dial gauge reads high or low by more
than 1 pound when tested at 11 pounds of pressure, it
should be replaced. If the reading is off by less than 1
pound, follow the recommendation of the person testing
your canner (see "Pressure Canner Testing," page 13).
Remember to have your new dial gauge tested before
you use it. Low gauge readings cause overprocessing
and may indicate that the accuracy of the gauge is
unpredictable. High readings cause underprocessing
and could lead to food spoilage.
Although many pressure canners have gaskets or seal-
ing rings made of rubber or a similar material to prevent
steam from escaping between the lid and the kettle rim,
some form a tight metal-to-metal seal with the use of
clamping mechanisms.
Safety features
The vent port (steam vent) lets air out of the canner and
releases steam as needed. On weighted-gauge pressure
canners the weight on the vent controls the escape of air
or steam. Generally, dial-gauge pressure canners have a
petcock attached to the vent. A petcock releases steam
and air when open and holds the steam when closed.
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