Place grape pulp and 1/4 cup sugar in a medium saucepan; bring to a boil. Reduce heat; simmer 10 minutes or until seeds begin to separate from pulp.
Press pulp mixture through a fine sieve into a bowl. Discard seeds.
Place skins, remaining 1/2 cup sugar, rind, juice, and pulp in saucepan; bring to a boil. Reduce heat; simmer until reduced to 2 1/2 cups (about 2 hours and 45 minutes), stirring occasionally.
Pour into a bowl; cool. Cover and store in refrigerator up to 2 weeks.
