Sort and wash grapes, and remove stems. Place them into a large kettle and crush them. Add water, cover, and bring to a boil over high heat. Reduce heat to low, and simmer for 10 minutes. Remove from heat, and extract juice. Allow the juice to stand in a cool place overnight to prevent the formation of crystals in the jelly.
Strain the juice through a double thickness of damp cheesecloth. Measure 4 cups of the juice into a large pot. Stir in the sugar. Quickly bring to a full rolling boil. Stir in pectin, and allow to boil hard for 1 minute. Remove from heat, and skim off foam. Pour into hot sterile jars, and process for 5 minutes in a boiling water bath.