Place the granulated sugar, corn syrup, salt and the remaining 1/2 cup (118ml) of water in a medium-size saucepan. Stir gently to combine. Place the saucepan on the stovetop over medium heat. Cook, without stirring, until the temperature reaches 230ºF (110ºC) on a candy thermometer. Gently swirl the pan occasionally to help prevent hot spots.