After it comes to a boil, turn the heat down to low-medium and simmer for 25 minutes. This length of time is needed to get the final product just right. If it's not cooked long enough, the end sugar hair removal product will be too sticky to work with.
Caution. If you only have a thin saucepan, a low-medium heat may be too high of a temperature to simmer. Keep the temperature as low as you need so that it's only simmering, not boiling and turning dark too quickly.