Sterilize your canning jars and lids.

If using fresh grapes, crush them and cook with a little water. Strain the mixture through a food mill or fine mesh strainer to extract the juice.

In a large pot, combine the grape juice and lemon juice. Stir in the fruit pectin and mix well.

Bring the pot to a boil over medium heat, stirring constantly.

Once boiling, add the granulated sugar all at once. Stir until fully dissolved, and bring back to a rapid boil.

Boil for 1-2 minutes, then check the consistency by dropping a spoonful on a cold plate.

Using a funnel, carefully fill the sterilized jars with the hot jelly, leaving about 1/4 inch of headspace.

Process the jars in a boiling water bath for 5-10 minutes.