Equipment for heat-processing home-canned food is of two main typesóboiling water canners
and pressure canners. Most are designed to hold seven quart jars or eight to nine pints. Small
pressure canners hold four quart jars; some large pressure canners hold 18 pint jars in two
layers, but hold only seven quart jars. Pressure saucepans with smaller volume capacities are
not recommended for use in canning. Small capacity pressure canners are treated in a similar
manner as standard larger canners, and should be vented using the typical venting procedures.
Low-acid foods must be processed in a pressure canner to be free of botulism risks. Although
pressure canners may also be used for processing acid foods, boiling water canners are 1-13
recommended for this purpose because they are faster. A pressure canner would require from 55
to 100 minutes to process a load of jars; while the total time for processing most acid foods in
boiling water varies from 25 to 60 minutes. A boiling-water canner loaded with filled jars requires
about 20 to 30 minutes of heating before its water begins to boil. A loaded pressure canner
requires about 12 to 15 minutes of heating before it begins to vent; another 10 minutes to vent
the canner; another 5 minutes to pressurize the canner; another 8 to 10 minutes to process the
acid food; and, finally, another 20 to 60 minutes to cool the canner before removing jars.
These canners are made of aluminum or porcelain-covered steel. They have removable
perforated racks and fitted lids. The canner must be deep enough so that at least 1 inch of briskly
boiling water will be over the tops of jars during processing. Some boiling-water canners do not
have flat bottoms. A flat bottom must be used on an electric range. Either a flat or ridged bottom
can be used on a gas burner. To ensure uniform processing of all jars with an electric range, the
canner should be no more than 4 inches wider in diameter than the element on which it is
Using Boiling-water Canners
Follow these steps for successful boiling-water canning:
1. Fill the canner halfway with water.
2. Preheat water to 140 F for raw-packed foods and to 180 F for hot-packed foods.
3. Load filled jars, fitted with lids, into the canner rack and use the handles to lower the rack
into the water; or fill the canner, one jar at a time, with a jar lifter.
4. Add more boiling water, if needed, so the water level is at least 1 inch above jar tops.
5. Turn heat to its highest position until water boils vigorously.
6. Set a timer for the minutes required for processing the food.
7. Cover with the canner lid and lower the heat setting to maintain a gentle boil throughout
the process schedule.
8. Add more boiling water, if needed, to keep the water level above the jars.
9. When jars have been boiled for the recommended time, turn off the heat and remove the
10 Using a jar lifter, remove the jars and place them on a towel, leaving at least 1-inch
spaces between the jars during cooling.