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. I boiled 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, I poured it into a tray to cool. It hardened up in about an hour and then I smashed it to pieces.