Wash grapes and let drain overnight. In morning, pick off stems, cook until skins pop. Strain or let drip through sugar sack. Measure juice, put into kettle and bring to boiling point. For every 3 cups juice use 4 cups sugar. Stir sugar, 1/2 cup at a time, into juice until all is dissolved. By the time all sugar is dissolved, jelly is getting thick. Pour into glasses; seal.