Rock Candy. 2 cups water • 1 cup white corn syrup • 3 1/2 cups sugar • 1/4 tsp cream of tartar Then I added: • 1/4 tsp vanilla extract • 3 drops of blue gel food coloring Boil the mixture and then continued stirring it on the heat until it reached 300 degrees F (used a candy thermometer to measure the temp). At that point, Pour it into a tray to cool. It hardened up in about an hour and then smash it to pieces. Great in a pretty jar for gifts!