According to Molecular Gastronomy: Exploring the Science of Flavor research has been conducted to determine the most effective and expeditious method to cool a hot cup of tea.
4) Leaving the teaspoon in the cup ranked the least efficient.
3) Adding warm milk resulted in the third worst.
2) Stirring the tea for one minute dropped the temperature by 6 degrees.
1) However, blowing in the cup of hot tea for the same amount of time while stirring was the quickest method, nearly twice as effective. Why? Because blowing and stirring maximizes the surface area between the air and the liquid.