Wait until the sugar has completely dissolved before boiling the liquid, and never stir once the syrup boils.
Stir the sugar and water over low heat until the sugar dissolves completely.
Using a wet pastry brush, brush the sugar crystals from the side of the pan.
Boil, without stirring, until the syrup reaches the soft-ball stage, which is between 116°C (241°F) and 118°C (244°F).
If you don’t have a sugar thermometer, drop about ¼ teaspoon of the syrup into a bowl of iced water. The ball of syrup should hold its shape but be soft when pressed.