Rinse your flowers gently for less than 30 seconds, removing all dirt and other unwanted matter from them. Immerse them immediately in an ice bath to help perk up the petals.
Shake off as much excess water as you can, and place the chilled flowers on paper towels to let them air dry completely.
Line your cookie sheet with parchment or wax paper, and dust it with superfine sugar.
Pour some of the sugar in a shallow bowl.
Beat two egg whites and 1 tsp. water in a bowl until they are no longer translucent and frothy. Powdered pasteurized egg whites or meringue powder used for baking can be substituted for the raw egg whites.
Holding a flower with your tweezers, use a paintbrush to coat it entirely with a thin, even layer of the egg white mixture. Any areas of the flower left uncovered will turn brown and not be properly preserved. To crystallized petals only, pluck them cleanly from the flower and hold their tips with tweezers to coat.
Hold the wet flower over the shallow bowl, and sprinkle sugar over the entire surface of the flower, coating it evenly on all sides. Gently shake off excess sugar. A clean salt shaker or fine sieve can be used for sprinkling the sugar.
Dry the flowers on the lined cookie sheet coated with sugar in a cool place for 12 to 24 hours.
To keep the shape of some flowers, place them upside down first. Turn the flowers occasionally to ensure proper drying on all sides.
Store your sugared flowers in an air-tight container between layers of airy, soft padding, such as tulle or Easter grass, for up to a year. This keeps the sugar from collecting moisture and allowing the flowers to rot.