Preparation Place large rack on sheet of foil. Whisk egg whites in medium bowl until frothy. Dip grape clusters into whites to coat. Arrange clusters on rack. Sift sugar over grapes, turning to coat on all sides. Let grapes stand until dry, at least 2 hours and up to 8 hours.
Preparation Place large rack on sheet of foil. Whisk egg whites in medium bowl until frothy. Dip grape clusters into whites to coat. Arrange clusters on rack. Sift sugar over grapes, turning to coat on all sides. Let grapes stand until dry, at least 2 hours and up to 8 hours.