Ippodo tea indicates that Sencha should be steeped for 60 seconds at 176 F (80 C). Suggested ration of tea to water is 2 Tbsp (yes, Tbsp!) to 7 ounces (210ml) of water. To cool water to the proper temperature, Ippodo suggests transferring the water once by first pouring into a cup and then the tea pot. A second and third pot can also be brewed at 176 F (80 C) water with no steeping time.
I had a WONDERFUL cup of cold-brewed Hosen at the Ippodo shop in Kyoto. I think that this was the first time I understood the meaning of “umami” – it was unlike anything I’ve ever tasted. Any Japanese green tea can be cold-brewed by steeping 2 Tbsp in 7 ounces of chilled water for 15 minutes. A second and third pot can be prepared by brewing the second pot for 7 minutes and the third for 3 minutes.