Pacific Northwest PNW 421 Using Manual - page 5
Canners with 16- to 23-quart capacity (volume of the ket-
tle) are common and hold seven quart jars for canning.
The smallest canner that can be used safely is one that
will hold at least four quart jars. Use of pressure
saucepans with smaller capacities is not recommended.
The weighted gauge is a small round weight or disk
that is placed on the vent port to control internal pres-
sure. Weighted-gauge pressure canners exhaust tiny
amounts of air and steam each time the gauge rocks or
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
needle to point to the amount of pressure inside the
canner. Remember to have your new dial gauge tested
before you use it. Dial gauges also should be checked
for accuracy before use each year.
If your dial gauge reads high or low by more than 2
pounds when tested at 11 pounds of pressure, it should
be replaced. If the reading is off by less than 2 pounds,
follow the recommendation of the person testing your can-
ner (see “Dial Gauge Inspection and Accuracy,” page 13).
Low readings cause overprocessing. If a gauge is read-
ing lower than it should, you can make adjustments to
avoid overprocessing, but they are not essential to safe-
ty. Gauges that read high cause underprocessing and
may result in unsafe food. Every pound of pressure is
necessary to reach the canner temperature needed for
producing safe food. Accurate gauges and adjustments
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