To prevent spoilage, homemade jams and jellies need to be processed in a boiling-water canner. This type of canner is a large kettle with a lid and a rack designed to hold canning jars. Any large cooking pot can be used if it has a rack and a tight-fitting lid and is deep enough for briskly boiling water to cover the jars by 1 inch. The following tips will help assure top-quality home-canned products.
Use only standard canning jars. These are tempered to withstand the heat inside the canner and their mouths are specially threaded for sealing canning lids. To prepare the canning jars, wash them in hot, soapy water; rinse thoroughly. To sterilize the jars, immerse them in boiling water for 10 minutes.
Use screw bands and new flat metal lids with a built-in sealing compound. Prepare screw bands and lids according to manufacturers directions.
Fill canner half full of water; cover and heat over high heat until boiling. Heat additional water in another kettle.
When the water is hot, fill each jar and place it on rack in canner. Leave some space between the jars. Most canners will hold up to 6 jars. After the last jar has been added, pour additional boiling water into canner until tops of jars are 1 inch below the water line. Cover; heat to brisk, rolling boil. Now begin the processing timing. Keep the water boiling gently during processing.
At the end of processing time, turn off heat; remove jars. Cool on rack, wooden board, or towel.
When jars are completely cool (12 to 24 hours), press the center of each lid to check the seal. If dip in lid holds, the jar is sealed. If lid bounces up and down, the jar isnt sealed. (The contents of unsealed jars can be refrigerated and used within two to three days or reprocessed within 24 hours. To reprocess, use a clean jar and a new lid; process for the full length of time specified.)