Remove from heat and skim off foam. Wipe jar rims and adjust lids. Process 5 minutes in a boiling water bath. In a large saucepan heat grapes at a low heat setting for 8 to 10 minutes to loosen skins. Put throu gh a food mill or wide mesh strainer.
Discard skins and seeds.
Combine ingredients in a saucepan. Bring to a rolling boil and boil 1 minute. Remove from heat and skim off foam. Wipe jar rims and adjust lids. Process 5 minutes in a boiling water bath.