Wash the grapes. If making jelly from grape juice, skip to step 6

In a large bowl, add enough grapes to fill the bottom of the bowl. Using a potato masher, crush the grapes.

Add the crushed grapes to a large non-reactive stockpot. Repeat until all the grapes are in the pot.

Add enough water to the pot just until the grapes are barely covered. Bring the grapes to a boil over medium-high heat, stirring frequently. Reduce heat and simmer for 10 minutes.

Pour the mixture into a jelly strainer or in a colander lined with cheesecloth over a large bowl. For best results let the mixture strain overnight.

In a small bowl, add the pectin and ½ cup of sugar and mix together. Set aside.

Place a metal spoon in a glass of ice water and set aside.

Pour the strained grape juice into a large stockpot and add the pectin/sugar mixture. Over medium-high heat cook the juice until it begins to boil.

Stir in the remaining sugar and bring it back to a rolling boil. Let it continue to boil for 1 minute and test the thickness using the cold spoon. Fill the teaspoon half full and set it on a plate. Once It cools to room temperature, turn the spoon sideways. If the gel has thickened to the desired consistency you can begin to fill the sterilized mason jars, leaving ¼ inch head space. If not, continue the boiling process and retest until it thickens.