Put a small plate in the freezer for testing the jams thickness later on.
Place the 6 cups of grapes and 3/4 cup of water into a sauce pan on a medium heat and cover with a lid. Cook and stir occasionally for 20 minutes or until the grapes have broken down into a sauce.
Put the sauce now into a blender and blend to desired thickness.
Add mixture back into the sauce pan with the 1/2 cup of agave nectar and continue cooking on a medium/low heat for 20 minutes stirring regularly.
Now use the chilled plate from the freezer and test the thickness of the jam by spreading a small spoonful on the surface. If it gels up then it is ready. Enjoy!