Rock candy is a candy made from large chunks of sugar which are grown on a string or stick. Because it is made from pure sugar, this candy will be naturally clear and extremely sweet. It may be eaten plain, dissolved in sweet drinks, or used as a garnish on desserts. Since the process for making rock candy is very straightforward, many people like to make it at home, and some teachers use it to illustrate crystal formation to young students.
To make rock candy, water and sugar are combined to make a supersaturated sugar solution. The solution is so high in sugar that no more sugar can be dissolved in it, causing added sugar to sink to the bottom. A substrate for crystal growth such as a stick or string is lowered into the solution and left undisturbed for a few days to a week, allowing crystals to form on the substrate as the water evaporates. When the substrate is removed, it is covered in very large, jagged sugar crystals.
Many people add food coloring to their rock candy to make it more visually interesting. Flavoring may be added as well, for people who want to taste something other than pure sugar. Sticks of this type of candy are often available in candy stores and along the seashore and similar vacation spots. The crystallized sugar is also sold in bulk for restaurant use as a decorative garnish.
To make rock candy, boil one cup of water and add two cups of sugar, stirring constantly and allowing the mixture to boil again. These amounts can easily be increased or decreased if desired, as long as you keep the ratio the same. Once the sugar has completely dissolved, pour the water into a jar and dip a string or stick into it. If you wish to add color or flavorings, do so after the sugar has dissolved, but before you pour it into a jar. Once the string is saturated, pull it out and allow it to dry. This will create seed crystals, which will allow the sugar crystals to be larger and more even.
Once the stick or string has dried, dip it back into the jar of dissolved sugar and allow it to sit until large crystals form. Try to avoid moving or jostling the jar, as this can disrupt the formation of the crystals. Once big, even crystals have formed, the rock candy can be removed from the jar and served or wrapped in wax paper for later consumption.