In a large saucepan, combine the corn syrup, salt, 1/2 cup water and granulated sugar. Place over medium heat. Bring to a boil. Stir the sugar until it has dissolved. Place the candy thermometer into the syrupy liquid -- without stirring -- until it is at 240°F. Still, allow it to boil. If it begins to foam up DO NOT WORRY! Just turn the heat down and/or remove saucepan from heat until it has cooled slightly.