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For those new to home canning, using the pressure canner for the first time can be an intimidating experience. Experienced home canners know a pressure canner is a necessity in preserving vegetables safely, as well as for preserving meat, poultry and fish - what we call low-acid foods. It is important to understand why the pressure canner is necessary for these foods, how to select a canner, and how to operate it safely.
A pressure canner can be a lifetime investment. If well cared for, it can outlast several generations! Because older canners may be handed down from grandmothers, or found at garage sales or thrift stores, user manuals may be lost along the way. The rubber gasket may need to be replaced and the dial gauge tested.
The pressure itself does not destroy harmful microorganisms, but the higher temperatures attained by steam under pressure for an adequate period of time do kill harmful bacteria capable of growing in canned food.
Selecting a Pressure Canner:
Models made before 1970 were heavy-walled (cast aluminum) kettles with a clamp-on or turn-on lid. At least one company still makes the cast aluminum, clamp-on lid type, which requires no gasket. Canners will have a dial or weighted gauge, a vent with a petcock or counterweight, and a safety valve or fuse. Most modern pressure canners are lightweight (pressed aluminum or stainless steel), thin-walled kettles. Most have a turn-on lid with a rubber gasket. The clamp-on type requires no gasket. All canners should have a jar rack so jars do not touch the bottom of the kettle or each other. The vent may be an automatic vent/cover lock, or a steam vent to be closed with a counterweight or petcock. The safety fuse may be a rubber cap that will blow off if pressure becomes excessive, or a one-piece counterweight.
Gauge Options
The weighted gauge exhausts tiny amounts of air and steam each time the gauge rocks or jiggles during processing so it is self-regulating. It controls pressure precisely but requires attention by listening so the rocking or jiggling is maintained but not excessive. It does not need periodic testing for accuracy. Some weight gauges indicate only 15-pounds pressure. Others may have options for 5, 10 or 15-pounds pressure. One disadvantage is that it cannot correct precisely for high altitude adjustment (such as 13 pounds for 6,000ft.).
Dial gauges should be checked for accuracy each season before using and should be replaced if the accuracy is off by more than a pound. Low readings may indicate accuracy is unpredictable. (Some Extension offices provide this service.) It is sometimes more difficult to regulate the heat under the canner to hold a constant pressure, especially on electric ranges.
Buying a used canner
Because a pressure canner is a rather expensive piece of equipment, finding a good used canner can be a real bargain. They may be found at garage sales, thrift stores and even grandma's attic. Many early-dated canners are useable, but may need replacement parts and a good cleaning. Replacement parts are sometimes available at variety or hardware stores, as well as from appliance repair shops and manufacturers of today's canners. Generally, old handles and knobs that have cracked and come off can be replaced. Check for any dents that might prevent a good seal when closed. A warped bottom will not make good contact with an electric unit and may never attain proper pressure.
Operating a pressure canner
If you have never operated a pressure canner, it's best to do a "trial run" without jars of food inside. This provides an opportunity to watch for steam leaks, check the gasket fit and determine what heat setting on the range seems to hold proper pressure. To do a "trial run":
- Make sure a rack is in the bottom of the canner
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Place three inches of water in the bottom
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Secure the lid correctly
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Turn heat to high and leave the vent (petcock) open. When steam
appears, allow the steam to vent 10 minutes so that steam, not air,
fills the entire canner. This ensures that you will attain the right
pressure.
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Close the petcock (on the dial gauge canner) or put the weight
gauge on the vent. If you have a weight gauge canner, be attentive to
when the rocking begins and start timing. Adjust heat to maintain a
slight jiggling. With a dial gauge canner, when the needle reaches the
desired pressure, adjust heat to maintain the pressure. (The required
pressure is 13 pounds at 6,000 feet altitude.) DO NOT LOWER PRESSURE by
opening the petcock or lifting the weight.
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Do not leave the kitchen area during the processing time. Keep a
close watch on the dial gauge or listen to the rocking of the weight
gauge.
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When processing time is complete, remove the canner from the
heating unit. Do not place it in a draft. Let the canner cool, but do
not hurry the cooling by using cold water. Too rapid cooling can cause
loss of liquid in the jars.
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When the pressure is at zero, open the petcock. Or, when the weight
gauge does not hiss when touched, remove the gauge and open the lid
carefully, lifting it away from the body to protect your face from
steam.
When ready to process jars of food, place jars on the rack so steam can flow around the jars without the jars touching. After opening the canner, remove jars immediately with a jar "lifter" and place on a dry towel or rack with ample space for air circulation. Avoid a drafty area. Fast cooling as well as fluctuating pressure may cause loss of liquid in the canned product. Do not touch the jar lids until completely cool. During the cool-down the jar lid is sucked down and seals. You will hear a ping as each jar seals.
For more detailed information about selection, care and operation of pressure canners, contact your local
Colorado State University Extension office. Fact Sheets with directions and processing times for vegetables, meats and fish are also available at Extension offices.
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Updated Tuesday, November 27, 2007
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