I have long been frustrated with the general and unspecific instructions on brewing tea which I often come across. Recently, I’ve come across two tables which provide absolutely precise brewing times (for Japanese green teas), amount of tea leaves, temperature of water, volume of water and number of servings. Extremely useful, only problem is that are differences between the two tables!
[From Fukujuen pamphlet, "Japanese Green Tea"]
NB: 1 cup = 1 U.S. cup, or 240ml; 1 tsp = 1 level spoonful
[Mutsuko Tokunaga, New Tastes in Green Tea (Tokyo: Kodansha, 2004), p. 23]
[...] gyokuro. As glass cups are thin and can be very hot to the touch, they are only suitable for teas which are not brewed with boiling water, i.e. green teas. High quality green teas, such as this gyokuro, should be brewed at 50°C-60°C, [...]