Bring 4 cups of grape juice to a simmer over medium-high heat, whisk in 1 tablespoon of pectin, and simmer for three minutes. Reduce the heat to medium-low, stir in 2 cups of sugar, stir and simmer until the sugar dissolves, and pour the jelly into clean jars.
Refrigerate the grape jelly after it cools. To make jelly with fresh grapes, bring 4 1/2 cups of stemmed Concord grapes, 1/2 cup of water and 1 chopped Granny Smith apple to a simmer. Continue to simmer until the mixture becomes juicy. After the mixture reaches the proper consistency, strain it through a fine sieve.
Combine 3 cups of the strained juice with 2 1/4 cups of sugar, and cook the mixture until it is 220 degrees Fahrenheit. Remove from heat, and pour the mixture into sterilized canning jars. Place the lidded jars in a pan of boiling water for five minutes. Refrigerate any jars that fail to seal.
Another option is to mix 5 cups of Concord grape juice, 1/2 teaspoon of butter and 1 box of fruit pectin together in a saucepan and bring the mixture to a rolling boil. Stir in 7 cups of sugar, and boil the mixture for one minute. Remove from heat, ladle into sterilized jars, and process the jars for five minutes in a boiling-water canner.