To make rock candy quickly, add corn syrup to the traditional recipe and allow the sugar syrup to harden on a flat cookie sheet. Traditional rock candy forms over a period of 3 to 10 days by creating a simple syrup with water and sugar. Pouring the simple syrup into a jar and hanging strings into the mixture will cause large sugar crystals to form and create rock candy.
Mixing 2 cups of sugar, 1/2 cup of corn syrup, and 1/2 cup of boiling water creates a thicker simple syrup that hardens quickly when placed on a flat cookie sheet. Once the mixture sets, it breaks easily into little pieces of rock candy. Flavored oils or food coloring can enhance the look and taste of the candy as well.