"If I could use my SBC for only one thing, it would be for canning," says Eleanor Shimeall. "Processing in a solar cooker is much simpler than conventional methods. It takes me about 10 minutes of preparation time starting from a bowl of fresh fruit to placing the jar in the cooker. An added bonus is that the benign heat of the sun does not destroy the jewel-like colors of the fruit."
Eleanor is such an advocate of solar canning that she has been giving demonstrations in the field without benefit of kitchen facilities. She has also included a chapter on this subject in her book, Eleanor's Solar Cookbook.
She says she uses canning jars or jars such as those used by commercially prepared spaghetti sauce, which have a rubber ring bonded into the inside of the screw-on cap.
Eleanor uses the "terminal sterilization" method: begin with clean glass jars and lids, add the fruit or tomatoes, dry sugar or salt, and water to fill up to the neck of the jar. You must leave space for expansion of the contents during cooking. Screw lids onto the jars as tightly as you can and place them into the solar cooker. Once the contents of the jar boils out from under the lid, the jar and contents are sterilized.
Lids with a rubber ring are made to release steam during canning. Once the correct temperature has been reached, the contents of the jar will boil and flow under the tightly screwed-on lid. Remove the jars one-by-one as each one boils over. Wipe clean, set aside away from drafts to cool down slowly. As the jar cools, the lid is pulled downward to form a vacuum seal. Check each cool jar to make sure it is sealed properly by hitting it with a spoon and listening for a clear ringing note, or gently press down on the lid making sure it doesn't move up and down. If a jar did not seal, add more liquid or another tomato and reprocess. The quality will not be impaired.
Melted wax can also be used in place of a lid.
Solar canning is safe for acid foods only. Acid foods are fruits and tomatoes, or their juice, jams, jellies. DO NOT CAN MEATS OR VEGETABLES IN YOUR SOLAR COOKER!!! Don't even add a sprig of parsley as botulism can grow on any non-acid food!