Making grape jelly is easier than you can think. This recipe is for the old-fashioned grape jelly which only needs two ingredients. We prefer Concord grapes or wild grapes, but trying make grape jelly with any grapes that you have on hand.
Wild grapes or underripe Concord grapes make the best jelly. Wash and stem the grapes. Put into the kettle, mash down and cook slowly for about 10 minutes, until the juice flows freely. Water may be added a little at a time if necessary to prevent scorching or sticking. Strain through a jelly bag or strainer or cheesecloth. Leave the strained juice overnight in the refrigerator to allow the white crystals that sometimes form to settle. In the morning, pour off the juice carefully, discarding the sediment, if any, at the bottom.
Measure out 4 cups (leave the rest for another batch). Heat the sugar in a double boiler; with 4 cups of juice, you’ll need 3 cups of sugar. Bring the juice to a full rolling boil, then add the heated sugar and bring the mixture back to a full rolling boil. Boil quickly, stirring, until the candy thermometer reads 8 degrees above the boiling point (about 220°F) or until the jelly sheets off the spoon. Skim and pour into hot, sterilized jars. Process in a hot water bath for 5 minutes.
Note: The jelly needs to be cooked until it’s fairly thick so make sure you cook it long enough. You can add two tablespoons of lemon juice to the batch while it’s coming up to temperature.