Bring the cup of water to a boil in the saucepan. Turn off the heat. Add the sugar. Stir until it is all dissolved. Set the pan aside and let the sugar solution cool.
Tie the string around the middle of the pencil. Rest the pencil on the top of the glass and let the string hand into the glass, almost to the bottom.
Pour the cooled sugar solution into the glass. Set the glass in a warm place where no one will disturb it for a few days.
Soon crystals will begin to form on the string. When a crust forms on top of the water, break it. More sugar crystals (rock candy) will grow on the string. Pick off the crystals and eat them.
