Michigan State University Extension
Preserving Food Safely - 01600496
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 heated.
(Using Boiling-Water Canners)
Follow these steps for successful boiling-water canning: 1. Fill the canner halfway with water. 2. Preheat water to 140 degrees Fahrenheit for raw-packed foods and to 180 degrees Fahrenheit 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 canner lid. 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.