You make rock candy by dissolving granulated sugar in boiling water to create a supersaturated solution, then pouring it into a clean glass jar. Suspend a wooden skewer or string coated in dry sugar crystals into the liquid so more sugar can crystallize around it over several days. Place the container in a warm, quiet spot and let it sit undisturbed while large, beautiful sugar crystals grow on the stick. Once the candy reaches your desired size, pull it out of the jar and let it dry completely.